JPS61258854A - Fine sphere of crosslinked polymer of acrylic ester and production thereof - Google Patents

Abstract

PURPOSE:The titled fine spheres having uniform and desired particle diameters, obtained by adding an oil-soluble crosslinking agent to an aqueous dispersion of a copolymer consisting of a (meth)acrylic ester and a reactive functional group-containing vinyl monomer and crosslinking the copolymer in the particles. CONSTITUTION:A copolymer consisting of (A) 90-99.5wt% (meth)acrylic ester having <=10 deg.C, preferably <=0 deg.C glass transition point and (B) 10-0.5wt% reactive functional group (carboxyl group, hydroxyl group, etc.)-containing vinyl monomer is dissolved in an organic solvent, the solution is added to an queous dispersion medium containing a surface active agent to give an aqueous dispersion. (C) An oil-soluble crosslinking agent such as a polyisocyanate compound when the reactive functional group of the component B is hydroxyl group is added to the aqueous dispersion, sufficiently stirred and lagged at 20-90 deg.C for 2-24hr to give fine spheres crosslinked in the particles. The particle diameters of the fine spheres are controlled by the kind. of the surface active agent, the amount added and stirring rate.

Description

Detailed Description of the Invention [Technical Field to which the Invention Pertains] The present invention relates to crosslinked polymer microspheres and a method for producing the same, and more specifically, to copolymerization of a (meth)acrylic acid ester and a vinyl monomer containing a reactive functional group. The present invention relates to crosslinked polymer microspheres obtained by dispersing the aggregate in the form of particles in an aqueous medium, adding an oil-soluble crosslinking agent to the dispersion, and causing a crosslinking reaction, and a method for producing the same.

[Prior art and its problems] In recent years, removable pressure-sensitive adhesive sheets that can be attached to unagigaeshi have become widely used. In addition to regular adhesives, sticky elastic microspheres may be used on the adhesive surface of the sheet. 1. By using elastic microspheres, it is possible to point-adhere the sheet to an adherend such as paper. This also made it possible to apply adhesive by spraying.

By the way, in order to obtain such microspherical polymer particles,
Suspension polymerization is generally preferred. Suspended JvJ polymerization is carried out using (meth)acrylic ester and various ionic monomers in the presence of small amounts of emulsifiers and oil-soluble initiators, but in such a method, the particle size is relatively large (
It is possible to obtain only copolymer microspheres with a particle diameter of 100% or more.

On the other hand, according to emulsion polymerization, it is possible to obtain microspheres having a particle size of Q, 17za+ or less, but since the microspheres obtained by this method tend to fuse together, it is difficult to separate individual particles in a dry state. I couldn't let it exist. There is also a method of blending a cross-linking monomer in emulsion polymerization, but since the main monomer must be selected depending on the reactivity of the monomer, there are restrictions on the types of microspheres that can be obtained.

[Object of the Invention] An object of the present invention is to find microspheres having a desired and uniform particle size and a method for producing the same.

[Summary of the Invention] The microspheres of the present invention are microspheres made of a copolymer composed of 90 to 99.5% by weight of ester of acrylic acid or methacrylic acid and 10 to 0.5% by weight of a vinyl monomer containing a reactive functional group. The copolymer microspheres are spheres, and are characterized in that the copolymer microspheres are intraparticle crosslinked with an oil-soluble crosslinking agent via a reactive functional group of a vinyl monomer.

On the other hand, the method for producing microspheres is characterized by adding an oil-soluble crosslinking agent to the aqueous dispersion of the copolymer, and then crosslinking the copolymer within the particles.

That is, the greatest feature of the present invention is that polymer microspheres are obtained by intraparticle crosslinking of an acrylic acid ester copolymer in a suspended state in the presence of an oil-soluble crosslinking agent.

The present invention will be explained in more detail below.

In the present invention, first, a copolymer of a (meth)acrylic acid ester and a vinyl monomer containing a reactive functional group is synthesized. The mixing ratio of (meth)acrylic acid ester/vinyl monomer in the copolymer is usually 90 to 99.5/10 to 0.5, preferably 95 to 0.5% by weight.
, 515 to 0.5. If the amount of (meth)acrylic acid ester blended is 90% by weight without swirling, it is difficult to obtain adhesiveness and elasticity, and if it exceeds 99.5% by weight, microspheres with sufficient intraparticle crosslinking cannot be obtained.

In order to obtain sticky microspheres at room temperature, (meta)
As an acrylic ester, the glass transition point is usually 10°C.
Hereinafter, preferably a temperature of 0° C. or lower is used. These esters may be used alone or in combination of two or more, and are appropriately selected depending on the intended use of the resulting microspheres. As the ester, (meth)acrylic ugly alkyl ester having a linear or branched alkyl group having 2 to 12 carbon atoms is usually used, and specifically, butyl (meth)acrylate, isobutyl (meth)acrylate, etc. , 5ec-butyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, inoctyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, etc. be done. These can be used alone, but when copolymerized with them, for example, methyl (meth)acrylate, tetradecyl (meth)acrylate, hexadecyl (meth)acrylate,
Stearyl (meth)acrylate and the like can also be used.

In addition, in order to increase the cohesive force of the uninvented globules, namely,
When the microspheres are used as an adhesive, in order to prevent the adhesive from remaining on the adherend by causing a stringing phenomenon when peeled from the adherend, vinyl acetate, styrene, acrylonitrile, Methacrylonitrile and the like can be added in an amount of up to 50% by weight of the alkyl ester monomer.

The vinyl monomer containing a reactive functional group is a substance having a functional group that can react with an oil-soluble crosslinking agent to cause intraparticle crosslinking. Here, the reactive functional groups include carboxyl group, hydroxyl group, ami7 group, glycidyl group,
Examples include methylol group, formyl group, mercapto group, acid anhydride, and the like, and the functional group is appropriately selected depending on the type of oil-soluble crosslinking agent. Specific examples of vinyl monomers having this group include (meth)acrylic acid, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)
Acrylate, glycidyl (meth)acrylate, N-
Examples include methylol (meth)acrylamide, N-butoxymethyl (meth)acrylamide, (meth)acrylic acid amide maleic anhydride, and the like.

Copolymers of (meth)acrylic acid esters and vinyl monomers can be obtained by conventionally known methods such as emulsion polymerization, suspension polymerization, solution polymerization, or bulk polymerization.The reaction conditions differ slightly depending on each polymerization method. Usually 5~ at 40-90℃
A copolymer is obtained by reacting for 20 hours.

Next, the obtained copolymer is dispersed in water to prepare an aqueous dispersion of polymer particles. For this purpose, a surfactant is usually added to an aqueous dispersion medium (preferably ion-exchanged water) in advance, and the copolymer is gradually added to the dispersion medium while stirring it.

At this time, since the polymer is insoluble in water, it is dispersed as oil droplets. In order to effectively disperse the polymer, it is necessary to prepare the polymer in advance in an organic solvent (toluene, ethyl acetate, n-hexane, cyclohexane, heptane, 1,1.1-)lichloroethane, etc.) at a concentration of about 20 to 30% by weight. dissolved in
It is preferable to gradually add the polymer solution to the dispersion medium. The mixing ratio of the dispersion medium and the polymer solution is preferably 5=1 to 1:1 by weight, and most preferably about 2/1. Further, when the viscosity of the polymer solution is high, it is effective to add a surfactant to the polymer solution and add water to the solution while stirring the solution. In addition, when the above-mentioned copolymer is obtained by emulsion polymerization or suspension polymerization using water as a dispersion medium, there is no need to prepare an aqueous dispersion liquid again, and it is possible to add a surfactant to the polymerization solution after the reaction is completed. You may also use it.

Examples of surfactants added to the aqueous dispersion of polymer particles include alkyl sulfonates represented by the following formula: % formula % (wherein R represents an alkyl group and X represents a halogen atom) (for example, Anionic surfactants such as sodium alkylbenzene sulfonate (e.g. sodium dodecylbenzene sulfonate) represented by the following formula (wherein R is an alkyl group and X represents a halogen atom); Polyoxyethylene alkyl ether (e.g., polyoxyethylene lauryl ether, polyoxyethylene oleyl ether) represented by the following formula: % formula % (wherein R is an alkyl group and n represents a positive integer) Nonionic surfactants such as polyoxyethylene alkylphenyl ether (e.g., polyoxyethylene octylphenyl ether, polyoxyethylene nonylphenyl ether) represented by the formula (wherein R is an alkyl group and n is a positive integer) Examples include agents. These surfactants are added to the aqueous dispersion of polymer particles above the critical micelle concentration, preferably within the range of 0.001 to 1.0%.

The particle size of the microspheres of the present invention can be adjusted by adjusting the amount and type of surfactant added and the stirring speed.

Usually, when forming small spheres of 0.1 to 0.01, the amount of surfactant added is increased and the stirring speed is set to 500 rpm. In addition, relatively small spheres can be obtained using anionic surfactants. On the other hand, when forming large spheres of 100 or more, it is preferable to add gelatin, starch, polyvinyl alcohol, polyvinylpyrrolidone, etc. in equal amounts along with a surfactant.

Next, after adjusting the particle size of the polymer particles, an oil-soluble crosslinking agent is added to the aqueous dispersion containing the particles. Since the oil-soluble crosslinking agent is insoluble in water, which is a dispersion medium, it is absorbed into the polymer particles when the dispersion is sufficiently stirred. Usually 30-12
By stirring for 0 minutes, the crosslinking agent is absorbed into the polymer particles. After that, by keeping the dispersion under constant temperature conditions, elastic microspheres with intraparticle crosslinking are obtained.

Various oil-soluble crosslinking agents are used depending on the type of reactive functional group in the copolymer. When the functional group is a hydroxyl group, a polyisocyanate compound is usually used. Specific examples of the compound include 1, for example, aliphatic polyisocyanates such as propylene diisocyanate and hexamethylene diisocyanate; aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, and naphthylene diisocyanate; 1-methyl- Alicyclic polyisocyanates such as 2,4-diisocyanate cyclohexane and 4,4-methylene-bis(cyclohexyl isocyanate) can be mentioned.

When the functional group is a carboxyl group, the above polyisocyanate compounds can be used, but in addition to these, polyfunctional epoxy compounds can also be used.

Specific examples of polyfunctional epoxy compounds include ethylene glycol, diglycidyl ether, propylene glycol diglycidyl ether, 1,8-hexanediol diglycidyl ether, and the like.

When the functional group is a glycidyl group, for example, polyamides such as a condensate of a dimer or trimer of an animal or vegetable oil unsaturated acid and an aryl or alkyl amine; trimellitic anhydride, methyltetrahydrophthalic anhydride, endo Polycarboxylic acid anhydrides such as methylenetetrahydrophthalic anhydride; general formula 8% polysulfides; R+0-(C:3H6S)n-C)+2-CH-CH2
-SHI 3n-1~2. R is a polymercaptan such as an aliphatic hydrocarbon; a phenolic resin such as trimethylaminomethylphenol or dimethylaminemethylphenol is used.

When the functional group is an amine group, for example, incyanates such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, xylylene diisocyanate, and polyisocyanate prepolymers can be used.

When using a substance that easily reacts with water, such as a polyisocyanate compound, as an oil-soluble crosslinking agent, dissolve the crosslinking agent in an appropriate organic solvent such as toluene or ethyl acetate, and use the resulting solution as a dispersion. Add to. At this time, since the crosslinking agent becomes difficult to contact with water, it is absorbed into the particles while keeping the reactive functional groups active. On the other hand, when a water-soluble crosslinking agent is used, the crosslinking agent diffuses throughout the aqueous dispersion and causes a crosslinking reaction between each polymer particle, so the entire system gels and can no longer be taken out as particles.

The amount of the oil-soluble crosslinking agent added is usually 0.1 to 0.001 times, preferably 0.07 to 0.03 times, the chemically equivalent amount by mole relative to the reactive functional group.

Note that a catalyst may be added to promote the crosslinking reaction. Examples of the catalyst include tertiary amines and quaternary ammonium salts used in crosslinking carboxyl groups with epoxy compounds.

The amount of catalyst used is usually 1 to 0.0 per part of crosslinking agent.
It is within the range of 1 part.

In addition, an appropriate amount of an ultraviolet absorber or an anti-aging agent may be added in order to improve the weather resistance of the microspheres obtained or to prevent aging due to oxidation.

After adding a predetermined amount of an oil-soluble crosslinking agent and other additives if necessary to an aqueous dispersion of polymer particles, and stirring the dispersion thoroughly, the reaction system is usually heated at 20 to 90°C for 2 to 24 hours. ,
Preferably, the temperature is kept at 40 to 60°C for 5 to 10 hours. During this crosslinking reaction, the polymer and crosslinking agent are mixed within the particles, so there is no particular need for stirring, but if the particles are unstable, stirring may be performed to maintain a dispersed state.

Because the polymer particles are three-dimensionally crosslinked by the above reaction,
Microspheres that maintain their spherical shape are obtained without the particles fusing together either in the solution state or after coating and drying.After the reaction, the microsphere-containing aqueous dispersion is directly coated with a knife coater and coated with adhesive tape. etc., but it can be used for
Usually, the microspheres are once isolated from the dispersion liquid and used for various purposes.

Usually, the microspheres of the present invention are obtained by adding a large amount of a polar solvent such as methanol, acetone, or an aqueous sodium chloride solution to an aqueous dispersion to precipitate microspheres, which are then filtered and then dried.

The microspheres do not fuse together even when redispersed in an organic solvent such as toluene, 1,1.1-)lichloroethane, n-hexane, cyclohexane, or ethyl acetate.
Therefore, it is possible to apply the microspheres to an object by spraying. Furthermore, if the microspheres themselves have adhesive properties, they can be used as adhesive sprays. Of course, the microspheres dispersed in a solvent may be applied by roll coating.In the case of adhesive elastic microspheres, by applying the core spheres to a base material such as paper, it is possible to make a point between the adherend and the adherend. It can be provided as a removable pressure-sensitive adhesive sheet that can be bonded. As a new application, the microspheres of the present invention may be used in vehicles such as inks and paints. In this case, inks and paints that give a three-dimensional effect, are matte, and have a soft feel are obtained.

[Effects of the Invention] In the present invention, since polymer particles are crosslinked using an oil-soluble crosslinking agent, microspheres that do not fuse with each other and can exist as particles in a dry state can be obtained. Furthermore, according to the method of the present invention, all of the oil-soluble crosslinking agent is absorbed into the polymer particles, so interparticle crosslinking does not occur, and therefore microspheres having the once adjusted particle size can be obtained. Therefore, by preparing the particle size in advance at the stage of dispersing the polymer before adding the crosslinking agent, microspheres having a uniform and desired particle size can be obtained.

Therefore, if the microspheres are elastic and sticky, they are useful as adhesives for removable pressure-sensitive adhesive sheets that can be point-adhered, and if they are non-tacky, they are useful as vehicles for ink and paint. .

[Examples of the Invention] Hereinafter, the present invention will be described in detail based on Examples, but the scope of the present invention is not limited by these Examples. In addition, all "parts" and "%" in the examples represent "parts by weight" and "% by weight", respectively.

Example 1 In a reaction vessel, 350 parts of toluene, 49 parts of n-butyl acrylate, 48 parts of 2-ethiohexyl acrylate, 2 parts of acrylic acid, and 0.0 parts of azobisisobutylnitrile were added.
25 parts of the mixture was added, and the mixed solution was stirred at 90° C. for 10 hours in a nitrogen stream to obtain an acrylic ester polymer.

Next, 200 parts of this polymer solution (30% solid content) was added to 400 parts of ion-exchanged water to which 4 parts of sodium dodecylbenzenesulfonate (anionic surfactant) was added while stirring at 300 revolutions per minute. Added gradually. Approximately 3
After stirring for 0 minutes, 1 part of Epicote 812 (trade name, epoxy resin, manufactured by Shell Chemical Co., Ltd.) and 0.5 parts of triethylamine were added.
was added to the solution and stirred for an additional 30 minutes. After that,
The solution was left at 40°C for 8 hours without stirring.

After the reaction was completed, the obtained mixed solution was applied as it was on a polyester film with a thickness of 25 mm, and the surface was visually observed, and the surface showed diffused reflection. Further, when the surface was observed using an optical microscope, it was found that the polymer microspheres crosslinked by the reaction had a uniform particle size of 200 particles on average. Furthermore, the microspheres also had elasticity.

Example 2 In a reaction vessel, 200 parts of ion-exchanged water, 10 parts of inbutyl acrylate, 87 parts of inoctyl acrylate, 3 parts of acrylic acid, 0.2 parts of benzoyl peroxide, and sodium lauryl sulfate ( Add 1 part of anionic surfactant)
By suspending polymerization at 90°C in a nitrogen stream for 4 hours, lowering the temperature to 70°C and stirring for 16 hours,
An acrylic ester polymer was obtained.

Then, supervecamine (
0.5 part of butylated melamine resin (trade name, manufactured by Nippon Reichhold Co., Ltd.) was added, and the mixture was further stirred for about 30 minutes. Thereafter, the solution was left at 60°C for 24 hours. continue,
1. Add 300 parts of methanol to the reaction mixture to precipitate the produced crosslinked polymer microspheres, filter and dry them.
, 1.11 was redispersed in lychloroethane. The concentration of microspheres in the redispersion is 10%. The microspheres thus obtained were observed to be elastic and sticky, and had a uniform particle diameter of 30 mm on average.

Next, 60 parts of the above redispersion liquid and a propellant (liquefied propane)
A spray adhesive was prepared by mixing 40 parts. The adhesive could be sprayed without forming a spider web.

In suspension polymerization, the polymer can be obtained in the form of particles without any particular crosslinking. However, it has been found that polymer microspheres with higher cohesive strength can be obtained by intraparticle crosslinking of the polymer according to the present invention.

Example 3 200 parts of ion-exchanged water, 5 parts of ethyl acrylate, 92.5 parts of 2-ethylhexyl acrylate, and 2.5 parts of hydroxyethyl acrylate were placed in a reaction vessel.

Add 4 parts of sodium lauryl sulfate (anionic surfactant) and 0.15 parts of potassium persulfate, and add 6 parts of sodium lauryl sulfate (anionic surfactant) in a nitrogen stream.
An acrylic acid ester polymer was obtained by emulsion polymerization at 0° C. with stirring for 7 hours.

Next, 2.5 parts of a 20% toluene solution of Coronate L (trade name, polyisocyanate, manufactured by Nippon Polyurethane Co., Ltd.) was added to the obtained polymer solution, and the mixture was further stirred for about 30 minutes. Thereafter, the mixture was left at 30° C. for 8 hours. Subsequently, 300 parts of methanol was added to the reaction mixture to precipitate the resulting crosslinked polymer microspheres, which were filtered, dried, and redispersed in toluene. The concentration of microspheres in the redispersion is 12%. The microspheres exhibited elasticity and adhesiveness, and had a uniform particle size of 0.1 mm on average.

200 parts of the elastic microspheres were added to an acrylic ink having the following composition: 50 parts of titanium white, 100 parts of ethyl acetate, and 400 parts of toluene, and the resulting ink was applied to a polyester film using a gravure coater. Visual observation of the surface revealed that the ink had excellent matte properties.

Comparative Example 1 In Example 3, 300 parts of methanol was added to the polymer solution after emulsion polymerization to precipitate the polymer particles, which were filtered. When the core particles are completely dried, the particles fuse together and can no longer be redispersed.
It was redispersed in toluene before drying. The polymer concentration in the redispersion is 10%.

Next, Coronate L was added to 100 parts of the obtained polymer solution.
Add 2.5 parts of a 20% toluene solution of
It was left for 8 hours. The reaction solution completely gelled, and the crosslinked polymer could no longer be taken out in the form of particles.

Comparative Example 2 In Example 3, the polymer particles produced by emulsion polymerization were present in the polymer solution in a dispersed state with a particle size of 0.1-.

When this polymer solution was directly applied onto a 25 μm thick polyester film, a glossy and uniform coating was obtained. Therefore, the film was observed using an electron microscope, but no polymer particles were found.

Claims (2)

[Claims] (1) Acrylic acid or methacrylic acid ester 90
~99.5% by weight and 10 to 0.5% by weight of a vinyl monomer containing a reactive functional group, the copolymer microspheres comprising a reactive functional group-containing vinyl monomer. 1. Acrylic acid ester-based crosslinked polymer microspheres characterized by being intraparticle crosslinked with an oil-soluble crosslinking agent via a group. (2) Acrylic acid or methacrylic acid ester 90
An oil-soluble crosslinking agent is added to an aqueous dispersion of a copolymer consisting of ~99.5% by weight and 10 to 0.5% by weight of a vinyl monomer containing a reactive functional group, and then the copolymer is crosslinked within the particles. A method for producing acrylic ester crosslinked polymer microspheres, characterized by: