JP3225105B2 - Method for producing core-shell type emulsion - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a core / polymer which is polymerized using only a reactive surfactant containing a radically polymerizable unsaturated group (hereinafter simply referred to as "reactive surfactant"). The present invention relates to a method for producing a shell type emulsion, and the obtained emulsion is useful for adhesives and paints, papermaking, textiles, etc. by utilizing its function.

[0002]

2. Description of the Related Art In general, when two kinds of monomers having different hydrophobic-hydrophilic properties are separately polymerized in two steps, both polymer components undergo phase separation, and are composed of a particle core and a shell. Of different core-shell emulsions are produced.

[0003] In the first step, for example, alkyl benzene sulfonate, alkyl diphenyl ether disulfonate, alkyl sulfate,
Non-reactive surfactants (hereinafter simply referred to as surfactants) such as anionic surfactants such as higher fatty acid salts and nonionic surfactants such as polyoxyethylene alkyl phenyl ether can be used alone or as a mixture with the starting monomer. The core polymer emulsion is synthesized by a usual emulsion polymerization method using 0.5 to 5% by weight. Next, a method is known in which excess surfactant contained in this emulsion is carefully removed by dialysis or the like, and polymerization of the second-stage raw material monomer is performed by adding only a catalyst. (Polymer processing Vol.34, No.3, p5 ~
(See 11)

[0004] At this time, if the sur- factant is not completely removed but is present in the system in excess, new single particles of the monomer for the shell part are formed during the polymerization of the shell part in the second stage, and the core and the core are not treated.
It is not a shell type but a mixed emulsion of core particles and shell particles. Furthermore, since the surfactant used for the production of this emulsion is non-volatile, it will remain in the polymer even after moisture evaporates from the emulsion, and since the surfactant is a low molecular substance having a hydrophilic group, Poor compatibility with the polymer, causing localized concentration in the polymer film and uneven distribution, or migration to the interface between the polymer film and the adherend, causing a decrease in the water resistance, adhesion, etc. of the film. It has become.

In addition, when a persulfate is used as a polymerization initiator during the emulsion polymerization, ionic radicals generated by the decomposition become an initiator and remain as ionic terminal groups at polymer terminals, and the ionic radicals remain at the polymer terminals. A polymerization method that does not use a surfactant is also known, taking advantage of its stability and that it greatly contributes to the stability of the emulsion after polymerization.However, in order to maintain the stability of the emulsion, a large amount of persulfate is used. Must be used, resulting in impairment of the water resistance of the obtained polymer film. In this method, it is extremely difficult to produce an emulsion having a core-shell structure.

JP-A-2-17982 discloses that an unsaturated carboxylic acid monomer, an unsaturated sulfonic acid monomer and the like are polymerized together with other monomers in an alcoholic solvent, a neutralizing agent is added, and then water is added. A pressure-sensitive adhesive composition having a core portion of a soap-free emulsion obtained by distilling off a solvent and changing the phase to an aqueous system has been proposed, but the production method is extremely complicated, and according to the examples, the core portion particles are Of the film contains units of unsaturated carboxylic acid and unsaturated sulfonic acid monomers, so that the water resistance and adhesion of the film are inevitably reduced.

[0007]

SUMMARY OF THE INVENTION The present invention provides a simple and excellent novel core which does not have the above-mentioned problems of the prior art and has improved water resistance and adhesion of the resulting film.
The purpose of the present invention is to provide a method for producing a shell emulsion.

[0008]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that the use of a reactive surfactant is a key point, and reached the present invention. That is, the present invention has solved the above-mentioned problem, and does not use any non-reactive surfactant, but polymerizes using only a reactive surfactant.
This is a method for producing a shell type emulsion, comprising
Nomer, reactive surfactant, and polymerization initiator
Polymerizing the emulsion forming the core in the system,
Polymerization initiator and monomer forming shell part (however, shell part type
The core-forming monomer is more hydrophobic than the comonomer)
In addition, the core-shell emulsion obtained by polymerization
Manufacturing method .

Hereinafter, the present invention will be described in detail. Examples of the reactive surfactant used in the present invention include:

Embedded image

[0010]

Embedded image Anionic reactive surfactants such as, and

[0011]

Embedded image And other nonionic reactive surfactants.

The reactive surfactant may be used alone or in combination of two or more. If the amount is too small, a large amount of coagulum will be generated in the produced emulsion. The resulting film does not show good physical properties. If the amount is too large, the particle size of the polymer becomes too small, the viscosity of the emulsion becomes too high, the polymerization rate decreases, and the water resistance of the film also deteriorates. Therefore, the amount of the reactive surfactant to be used is preferably 0.5 to 15% by weight, particularly preferably 1 to 7% by weight of the total monomers.

In the method of the present invention, the monomer having a polymerizable unsaturated bond may be used alone or in combination of two or more of each of the core and shell portions among known monomers. a combination of monomers constituting the shell portion you the core portion and the more hydrophobic monomer. 25
It is advisable to select a monomer group classified below based on the number of grams of the monomer dissolved in 100 grams of water at ° C.

A: monomers less than 0.1 dissolved in 100 grams of water at 25 ° C. 2-ethylhexyl acrylate, isononyl acrylate, decyl acrylate, butyl methacrylate, styrene, α-methylstyrene, Chloromethylstyrene, vinyl chloride ^* , vinylidene chloride ^*, etc. ( ^{* at} saturated vapor pressure) B: Same as above. Monomers with dissolved gram number of 0.1 to less than 1. Butyl acrylate, ethyl methacrylate, isopropyl methacrylate, etc. C : Monomers having a dissolution gram number of 1 or more and less than 10 Ethyl acrylate, methyl acrylate, methyl methacrylate, vinyl acetate, etc. D: Monomers having a dissolution gram number of 10 or more Acrylonitrile, maleic anhydride, acrylic acid, methacrylic Acid, 2-hydroxyethyl (meth) acrylate,
Hydroxyalkyl (meth) acrylates such as 2-hydroxypropyl (meth) acrylate, (meth) acrylamide, diacetone (meth) acrylamide, N-
(Meth) acrylamides such as methylol (meth) acrylamide, (meth) acrylic tertiary amines such as dimethylaminoethyl acrylate, vinyl sulfonic acid,
Monoethylenically unsaturated sulfonic acids such as styrene sulfonic acid and 2-acrylamido-2-methylpropane sulfonic acid and salts thereof

In addition to the above, small amounts of polyfunctional monomers can be used to crosslink the polymer. Examples of this are divinylbenzene, allyl (meth) acrylate,
Examples include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, glycidyl (meth) acrylate, and glycidyl allyl ether. The polyfunctional monomer is used as a monomer constituting the core portion and the shell portion irrespective of hydrophobicity and hydrophilicity. However, it is preferable in the present invention to use an amount of 5% by weight or less in the core portion.

The weight ratio of the core polymer to the shell polymer is preferably from 1: 0.01 to 3, more preferably from 1: 0.02 to 1.

In addition, if necessary, a rosin-based, petroleum-based, coumarone-indene-based, phenolic-based, or other tackifying resin may be added to the monomer before use.

Examples of the radical polymerization initiator used in the method of the present invention include persulfates such as potassium persulfate and ammonium persulfate, aqueous hydrogen peroxide, t-butyl hydroperoxide and hydrochloride of azobisamidinopropane. Water-soluble types, oil-soluble types such as benzoyl peroxide, cumene hydroperoxide, dibutyl peroxide, diisopropyl peroxy dicarbonate, cumyl peroxy neodecanoate, cumyl peroxy octoate, azobisisobutyronitrile, etc. Is exemplified. Further, if necessary, a redox system using a reducing agent such as sodium acid sulfite, Rongalit, or ascorbic acid can also be used. The amount of the polymerization initiator to be used may be usually 0.1 to 10% by weight, preferably 0.5 to 5% by weight, based on the monomer.

In order to produce a core-shell type emulsion, first, the above-mentioned various monomers are mixed, and a reactive surfactant, a polymerization initiator and the like are added thereto, and the emulsion for forming the core portion is polymerized in an aqueous system. In this case, various methods such as a method of batch polymerization and a method of polymerization while continuously supplying each component can be applied. Polymerization is usually 10 to 90 ° C
It is good to carry out at a temperature of under stirring. In the core polymerization, it is important that the reactive surfactant is almost completely polymerized and does not substantially remain in the aqueous phase of the core polymer emulsion. At the time of polymerization, new particles may be generated due to the monomer in the shell portion, which reduces the effects of the present invention. Next, a polymerization initiator and various monomers are further added to the system, and polymerization is performed to form a shell portion.

[0020]

EXAMPLES The present invention will be specifically described based on examples and comparative examples, but the present invention is not limited to the examples. In the examples, parts and% are parts by weight and% by weight, respectively.
Is shown.

Example 1 A polymerization vessel equipped with a stirrer, a condenser, a thermometer and a nitrogen gas inlet was charged with 156 parts of deionized water and a reactive surfactant Eleminol JS-2 (trade name, manufactured by Sanyo Chemical Industries, Ltd.). 3.3 parts, reactive surfactant Adecaria Soap NE
-10 [Asahi Denka Kogyo Co., Ltd., trade name] 5 parts,
The mixture was heated to 50 ° C. with stirring to dissolve, and then replaced with nitrogen. 0.2 parts of aqueous hydrogen peroxide and 0.07 ferrous sulfate
Was added, and 20 parts of a 1% aqueous solution of ascorbic acid were added, and 167 parts of butyl acrylate were added dropwise over 3 hours at the same time, and the mixture was further reacted at 50 ° C. for 2 hours to complete the polymerization. When the solid content, pH, viscosity and average particle diameter of the emulsion at the end of the core polymerization were measured,
They were 49.9%, 3.8, 560 cps and 251 nm, respectively. The measurement of the average particle diameter was performed by using a submicron particle analyzer manufactured by Coulter Corporation. In addition, reactive surfactant remaining in the system is analyzed using the Epton method (anion type) and the liquid chromatography method (nonionic type).
And it was confirmed to be 0.1% or less.

The reactive surfactant used in the core polymerization has the following structure.

Embedded image

Subsequently, 62 parts of deionized water was charged into the polymerization vessel, and after nitrogen replacement, 0.1 part of hydrogen peroxide and 0.03 part of ferrous sulfate were added, and 10 parts of a 1% aqueous solution of ascorbic acid were further added. And 72 parts of methyl methacrylate
The mixture was dropped uniformly over a long period of time, and further reacted at 50 ° C. for 2 hours to complete the polymerization, thereby producing a core-shell emulsion. When the solid content, pH, viscosity and average particle size of the emulsion at the end of the shell polymerization were measured,
They were 49.9%, 3.3, 340 cps and 278 nm, respectively.

The stability of the core-shell emulsion obtained above and the physical properties of the film were evaluated. The evaluation was performed as described below, and the results were as shown in Table 2. (Emulsion Stability) One drop of the emulsion was dropped on the palm and rubbed with the finger of the opposite hand, and evaluated on a three-point scale based on the time until the particles became tattered. ：: 10 seconds or more Δ: 5 to 10 seconds ×: 5 seconds or less (finger touch) Emulsion was applied on a glass plate so that the dry film thickness became 20 g / m ^2, and then 100
The film was dried at 2 ° C. for 2 minutes to prepare a film, which was used as a test piece. The presence or absence of tack on the surface of the film was evaluated by touch. (Water resistance) The test piece was immersed in water, taken out at regular time intervals, and the time required until the characters of the newspaper became unreadable through the membrane was measured and evaluated on a three-point scale. ：: 7 days or more Δ: 2 hours to 7 days ×: 2 hours or less (Transparency) The transparency of the test piece was visually evaluated. Good transparency ○ 〜 △ 〜 × Poor transparency

Examples 2 to 4 In the same manner as in Example 1, the reactive surfactants shown in Table 1 were polymerized with the types and amounts of the monomers and additives used in the core and shell portions, and the core-shell type was obtained. An emulsion was prepared. The stability of the obtained emulsion and the physical properties of the film test piece were similarly evaluated, and the results are shown in Table 2.

Comparative Example 1 Anionic surfactant EMAL 0 [manufactured by Kao Corporation, trade name] 1.7 parts instead of reactive surfactant Eleminol JS-2 and Adecaria Soap NE-10, nonionic Surfactant Neugen EA-170 [manufactured by Daiichi Kogyo Seiyaku Co., Ltd.
[Trade name] An emulsion was obtained in the same manner as in Example 1 except that 3.3 parts were used. The stability of the obtained emulsion and the physical properties of the film test piece were similarly evaluated, and the results are shown in Table 2.

Comparative Example 2 135 parts of deionized water was charged into a polymerization vessel equipped with a stirrer, a condenser, a thermometer and a nitrogen gas inlet, and the inside temperature was raised to 80 ° C. after purging with nitrogen. Then, simultaneously with the addition of 40 parts of a 20% aqueous solution of ammonium persulfate, 167 parts of butyl acrylate were uniformly added dropwise over 3 hours, and the reaction was further carried out at 80 ° C. for 2 hours to complete the polymerization. Thereafter, 44.6 parts of deionized water was charged and the atmosphere was replaced with nitrogen again.
° C, 0.1 part of hydrogen peroxide solution, ferrous sulfate 0.0
3 parts, and then a 1% aqueous solution of ascorbic acid 10
At the same time as the addition of 72 parts, 72 parts of methyl methacrylate was uniformly added dropwise over 1 hour, and further reacted at 80 ° C. for 2 hours to complete the polymerization to obtain an emulsion. The stability of the obtained emulsion and the physical properties of the film test piece were evaluated in the same manner as in Example 1, and the results are shown in Table 2.

[0028]

[Table 1]

The reactive surfactant in Table 1 has the following structure.

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[0030]

[Table 2]

From the results of the evaluation of finger touch, only the characteristics of the polymer composed of the monomer used in the shell part are shown in the examples, whereas the characteristics of the polymer composed of the monomer used in the core part are considered in the comparative examples. Characteristics appear. This indicates that the examples produce emulsions with a complete core-shell structure. In addition, since the evaluation of transparency is good in Examples, it is inferred that new particles are not generated by polymerization of the shell part and the core-shell structure is complete.

[0032]

According to the present invention, a novel method for producing a core-shell type emulsion having a simple and stable core-shell structure is provided. The emulsion obtained by this production method has excellent water resistance because the film does not contain a free surfactant, and the polymer characteristic of the shell part is remarkably exhibited as its surface characteristic. Very useful for adhesives, paints, papermaking and textiles.

Continuation of the front page (72) Inventor Nobuyuki Takahata 2-17-33 Kitafu, Takefu-shi, Fukui Prefecture Nissin Chemical Industry Co., Ltd. (56) References JP-A-62-236808 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) C08F 2/16-2/30

Claims (1)

(57) [Claims] 1. A method for producing a core-shell emulsion, comprising polymerizing using only a reactive surfactant without using any non-reactive surfactant ,
Core-forming monomer, reactive surfactant, and polymerization initiation
Add emulsion and polymerize emulsion to form core in aqueous system
And a polymerization initiator and a monomer for forming a shell portion (however,
The core-forming monomer is less dense than the shell-forming monomer
Core-shell type obtained by polymerization
A method for producing an emulsion .