JP2004244587A - Preparation process for polymer aqueous dispersion, and polymer aqueous dispersion - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a process for manufacturing an aqueous dispersion of a polymer which has a small volume-mean particle size and a desired copolymerization composition ratio from two or more kinds of radically polymerizable monomers using a small amount of an emulsifier. <P>SOLUTION: The preparation process of the polymer aqueous dispersion comprises dispersing an aqueous solution to be dispersed, which contains a monomer mixture containing at least two kinds of radically polymerizable monomers, an initiator, and a dispersing agent, by injecting at an injection pressure of 6.5×10<SP>7</SP>Pa or more to obtain a monomer aqueous dispersion and then copolymerizing the monomer aqueous dispersion. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

表１から、実施例のポリマー水分散体は、いずれも体積平均粒径が１μｍ以下であり、剥離力が軽く、かつ残接力が高く有用な剥離剤であることが分かる。これから実施例で得られたポリマー水分散体は、所望の組成比の共重合体であることが分かる。一方、比較例１はモノマー混合物の種類、組成比が実施例１と同じであるが、得られたポリマー水分散体は剥離力が大きくて、残接力が低いことが分かる。これから比較例１で得られたポリマー水分散体は、所望の組成比の共重合体が得られいないことが分かる。比較例２はモノマー混合物の種類、組成比が実施例２と同じであるが、得られたポリマー水分散体は体積平均粒径が大きい。そのため残接力が低く実用的ではない。
【図面の簡単な説明】
【図１】本発明の製造方法に用いる乳化分散機の一例である。
【図２】図１の乳化分散機の一態様である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing a polymer aqueous dispersion and a polymer aqueous dispersion obtained by the method. The polymer aqueous dispersion of the present invention can be applied to various uses. For example, it is useful as a water-based release agent, a water-based antiblocking agent, a water-based slip agent, a water-based water repellent and the like used for paper base materials and various plastic base materials such as polyvinyl chloride and polyolefin. Particularly, it is useful as an aqueous release agent for a release sheet, and a release sheet coated with the aqueous release agent of the present invention is suitable for protecting and preserving an adhesive surface such as an adhesive tape or an adhesive sheet.
[0002]
[Prior art]
In general, in an adhesive body such as an adhesive tape or an adhesive sheet, in order to protect the adhesive surface, a release sheet is attached to the adhesive surface, or the adhesive body is wound into a roll to form a substrate. Is stuck on the back. A release agent is applied to the release surface of the release sheet or the back surface of the substrate in order to improve the releasability during use.
[0003]
Conventionally, a silicone-based release agent or a release agent comprising a polymer having a long-chain hydrocarbon group such as a long-chain alkyl group (hereinafter referred to as a long-chain alkyl-based release agent) has been used as the release agent. In recent years, long-chain alkyl-based release agents have attracted attention because they have superior re-adhesiveness, writing properties, and printability as compared with silicone-based release agents. For example, it has been proposed to use a polymer obtained by reacting an alkyl isocyanate with ethylene vinyl alcohol as a solvent-type release agent (for example, see Patent Document 1).
[0004]
Further, a technique for converting a long-chain alkyl-based release agent to an aqueous solution has been proposed in consideration of work environment and pollution. For example, a long-chain alkyl-based release agent is obtained by reacting raw materials under stirring in water (for example, see Patent Document 2). Further, an aqueous dispersion obtained by emulsifying and dispersing a release polymer having a long-chain alkyl group in water is used as an aqueous release agent (for example, see Patent Documents 3 and 4).
[0005]
The aqueous release agent comprising an aqueous dispersion of the release polymer having a long-chain alkyl group is dispersed in the aqueous dispersion obtained so that the coating product is generally considered to be useful. It is required that the aqueous dispersion be a fine one having a volume average particle diameter of 1 μm or less, and have excellent storage stability and dispersion stability. For this reason, a large amount of an emulsifier is necessarily used in the production of the aqueous dispersion. The amount of the emulsifier in these aqueous dispersions is generally 10 to 100 parts by weight (dry weight) based on 100 parts by weight (dry weight) of the release agent polymer.
[0006]
However, when an aqueous dispersion (water-based release agent or the like) produced by using a large amount of an emulsifier is applied to an adhesive or the like with a release sheet coated on various substrates, a release film formed on the release sheet is obtained. A part of the adhesive migrates to the surface of the pressure-sensitive adhesive such as a pressure-sensitive adhesive body, and has an adverse effect such as a decrease in the adhesive strength of the pressure-sensitive adhesive and a contamination of the surface of the adherend adhered to the pressure-sensitive adhesive body.
[0007]
Further, the aqueous release agent can be obtained by a method of emulsifying and dispersing a radical polymerizable monomer having a long-chain alkyl group together with a polar monomer in water, followed by emulsion copolymerization (for example, see Patent Document 5). This method is considered to be a useful method for obtaining an aqueous dispersion of a release polymer having a volume average particle diameter of submicron or less with a relatively small amount of emulsifier. However, the radical polymerizable monomer having a long-chain alkyl group and the polar monomer copolymerized therewith have significantly different solubility in water. Therefore, in the case of ordinary emulsion polymerization, the solubilization rates of the monomers in the micelles are different, and it has been difficult to obtain a copolymer having an intended composition ratio. Therefore, the obtained aqueous release agent has not been obtained having the intended properties. On the other hand, it was difficult to obtain an aqueous dispersion of a release polymer having a volume average particle size of submicron or less by ordinary suspension polymerization.
[0008]
[Patent Document 1]
Japanese Patent Publication No. 60-30355
[0009]
[Patent Document 2]
JP-A-61-113678
[0010]
[Patent Document 3]
JP-A-9-111197
[0011]
[Patent Document 4]
JP-A-9-29756
[0012]
[Patent Document 5]
JP-A-4-222886
[0013]
[Problems to be solved by the invention]
The present invention provides a method for producing an aqueous dispersion of a polymer having a small volume average particle diameter and a desired copolymer composition ratio from two or more kinds of radically polymerizable monomers using a small amount of an emulsifier and the production method. It is an object of the present invention to provide an aqueous polymer dispersion. Still another object of the present invention is to provide a water-based release agent which uses an aqueous dispersion of the polymer and does not affect the adhesive properties of an adhesive such as an adhesive.
[0014]
[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 above-mentioned object can be achieved by the following manufacturing method, and have accomplished the present invention.
[0015]
That is, the present invention provides a monomer mixture containing at least two kinds of radically polymerizable monomers, an aqueous solution to be dispersed containing an initiator and a dispersing agent, at an injection pressure of 6.5 × 10 4. ⁷ The present invention relates to a method for producing a polymer aqueous dispersion, which comprises dispersing a monomer aqueous dispersion by spraying at a pressure of Pa or more to form a monomer aqueous dispersion, and then copolymerizing the monomer aqueous dispersion.
[0016]
In the method for producing a polymer aqueous dispersion, the aqueous solution to be dispersed is filled with an injection pressure of 6.5 × 10 ⁷ ~ 3.1 × 10 ⁸ It is preferable to inject at Pa, the initial injection speed: 150 to 630 m / sec.
[0017]
In the present invention, an aqueous solution to be dispersed containing a dispersoid (initiator and monomer mixture) and a dispersion medium (dispersant and water) is injected at a pressure of 6.5 × 10 4 ⁷ The monomer mixture is dispersed in water by jetting at an ultra-high pressure of Pa or more at an ultra-high speed and at an ultra-high speed to form a monomer aqueous dispersion of fine particles. In addition, since the dispersoid and the dispersion medium are injected at an ultra-high pressure and an ultra-high speed, high energy can be efficiently used for the production of the monomer aqueous dispersion. A fine monomer aqueous dispersion having the following average particle size can be obtained. In addition, since the monomer mixture which is a dispersoid is simultaneously incorporated into the monomer aqueous dispersion, the desired coexistence is obtained even when the monomer mixture contains two types of radically polymerizable monomers having different properties. An aqueous dispersion of a polymer having a polymerization composition ratio can be obtained.
[0018]
The higher the injection pressure, the smaller the particle size of the obtained aqueous monomer dispersion, which is preferable. The injection pressure is 6.5 × 10 ⁷ Pa or more, and further 1.8 × 10 ⁸ It is preferably Pa or more. Injection pressure 6.5 × 10 ⁷ If it is less than Pa, it is difficult to differentiate from a general rotary emulsifier, it is not possible to produce a monomer aqueous dispersion with high energy efficiency from the injection pressure, and the average particle size of the obtained monomer aqueous dispersion is large. Become. A polymer dispersion obtained by polymerization using an aqueous monomer dispersion having a large particle size necessarily becomes a polymer dispersion having a large particle size. When the polymer dispersion is used as an aqueous release agent, it does not become a processed product having an appropriate thickness, and the formed film has poor uniformity. And so on. On the other hand, the upper limit of the injection pressure is 3.1 × 10 ⁸ It is about Pa.
[0019]
The initial injection speed is preferably 150 m / sec or more from the viewpoint of appropriately controlling the average particle size of the obtained aqueous monomer dispersion. Further, it is preferably at least 370 m / sec. On the other hand, from the viewpoint of stable operation of the apparatus, the initial injection speed is preferably 630 m / sec or less, more preferably 560 m / sec or less.
[0020]
The method for producing a polymer aqueous dispersion can be suitably applied to a case where a non-polar monomer having poor solubility in water and a polar monomer having good solubility in water are contained as radical polymerizable monomers. Examples of the nonpolar monomer having poor solubility in water include (meth) acrylic acid esters having a long-chain alkyl group having 8 or more carbon atoms. The polar monomer having good solubility in water includes, for example, at least one selected from acrylic acid, methacrylic acid, and acrylonitrile.
[0021]
As described above, the method for producing a polymer aqueous dispersion of the present invention is to obtain a polymer aqueous dispersion having a desired copolymer composition ratio even when the monomer mixture contains two types of radically polymerizable monomers having different properties. Can be. For example, when preparing a releasable polymer, at least one (meth) acrylate having a long-chain alkyl group having 8 or more carbon atoms is used, and at the same time, the heat resistance of the resulting film of the releasable polymer is improved. Further, a monomer having a polar group can be used in combination for improving anchoring property to a substrate to be coated.
[0022]
In the method for producing an aqueous polymer dispersion, it is preferable that the dispersant (dry weight) is blended in an amount of 10 parts by weight or less based on 100 parts by weight (dry weight) of the monomer mixture. The polymer aqueous dispersion of the present invention can reduce the volume average particle diameter of the monomer aqueous dispersion even when the amount of the dispersant used is reduced to 10 parts by weight or less, and maintain the storage stability of the obtained polymer aqueous dispersion. Good performance can be maintained. In addition, the amount of the dispersant used is preferably as small as possible from the properties of the release agent, and the dispersant does not migrate to the adhesive in contact with the release treated surface, without reducing the adhesive force of the adhesive, The cause of adhesive contamination is eliminated. The use amount of the dispersant is more preferably 3 parts by weight or less. On the other hand, in order to obtain an aqueous dispersion having good storage stability, the amount of the dispersant used is preferably 0.2 parts by weight or more, more preferably 0.5 parts by weight or more.
[0023]
In the method for producing a polymer aqueous dispersion, it is preferable that the volume average particle diameter of the monomer aqueous dispersion is fine particles of 1 μm or less. The aqueous monomer dispersion of the present invention has good storage stability even with the fine particles. The volume average particle size is preferably 0.05 to 0.5 μm. In addition, the volume average particle diameter of the aqueous dispersion of the polymer obtained by copolymerizing the monomer aqueous dispersion is also 1 μm or less, more preferably 0.05 to 0.5 μm or less.
[0024]
The present invention also relates to a polymer aqueous dispersion obtained by the production method. Further, the present invention relates to an aqueous release agent containing the polymer aqueous dispersion. Although the polymer aqueous dispersion of the present invention can be used in various applications, it is particularly useful as an aqueous release agent, and provides a thin-layer coated product that does not cause problems such as contamination on the adhesive surface of the adhesive. Can be.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
The aqueous polymer dispersion of the present invention is obtained by forming a monomer mixture containing at least two kinds of radically polymerizable monomers, an aqueous solution to be dispersed containing an initiator and a dispersant into a monomer aqueous dispersion, and then copolymerizing the same. Can be
[0026]
The radically polymerizable monomer is not particularly limited, but as described above, when producing an aqueous dispersion of a releasable polymer, a non-polar monomer having poor solubility in water and a polar monomer having good solubility in water are used. It is preferred to include.
[0027]
Examples of the nonpolar monomer having poor solubility in water include (meth) acrylic acid esters having a long-chain alkyl group having 8 or more carbon atoms. If the number of carbon atoms is 7 or less, there is an inconvenience in terms of peelability. Examples of the long-chain alkyl group having 8 or more carbon atoms include octyl group, nonyl group, decyl group, undecyl group, dodecyl group, hexadecyl group, octadecyl group, and eicosyl group. Is about 8 to 22. It is more preferable that the number of carbon atoms be 12 to 20 from the viewpoint of polymer releasability. On the other hand, examples of polar monomers having good solubility in water include acrylic acid, methacrylic acid, and acrylonitrile.
[0028]
It is preferable that the ratio of the non-polar monomer to the polar monomer is 0.2 to 120 mol parts per 1 mol part of the non-polar monomer. When the amount of the polar monomer is 0.2 mol part or less, the effect of improving the heat resistance of the resulting polymer film and the improvement of the anchoring property to the substrate are insufficient. If the amount exceeds 120 mol parts, the peeling properties are affected, and the peeling force is increased, which is not desirable.
[0029]
In addition, various monomers can be contained in the monomer mixture according to the properties of the obtained polymer. When producing the aqueous dispersion of the releasable polymer, in addition to the non-polar monomer and the polar monomer described above, other monomers may be further contained as long as the releasability of the polymer is not impaired.
[0030]
As the initiator, any of oil-soluble and water-soluble initiators generally used for radical polymerization can be used, but they are incorporated into an aqueous monomer dispersion and can be subjected to suspension polymerization of a monomer mixture. Good oil-soluble initiators are preferred. Examples of the oil-soluble initiator include 2,2'-azobisisobutyronitrile, 2,2-azobis-2,4-dimethylvaleronitrile, 2,2'-azobis-2-methylbutyronitrile, Benzoyl oxide, cumene hydroperoxide, t-butyl hydroperoxide, isobutyryl peroxide, dicumyl peroxide and the like are used. The amount of the initiator used is the same as in the case of ordinary radical polymerization, and is preferably 0.1 to 10 parts by weight with respect to 100 parts by weight of the monomer mixture.
[0031]
As the dispersant, those suitable for stably dispersing the monomer mixture as fine oil droplets are preferable. As the dispersant, an anionic, cationic, or nonionic dispersant can be used alone or in combination. As described above, the use amount of the dispersant is desirably 10 parts by weight or less based on 100 parts by weight of the monomer mixture.
[0032]
Specific examples of the dispersant include, for example, anionic dispersants such as sodium stearate, potassium oleate, and sodium polyoxyethylene alkyl ether sulfate; polyoxyethylene cetyl ether, polyoxyethylene oleyl ether, sorbitan monostearate, and sorbitan Nonionic dispersants such as monooleate and polyethylene glycol monostearate; and cationic dispersants such as cetyltrimethylammonium chloride, stearyltrimethylammonium chloride and distearyldimethylammonium chloride.
[0033]
The aqueous solution to be dispersed contains a monomer mixture containing at least two kinds of radically polymerizable monomers, an initiator and a dispersant. In the aqueous solution to be dispersed, a chain transfer agent having good compatibility with the monomer mixture may be used in order to control the molecular weight of the obtained polymer. Various additives can be added to the aqueous solution to be dispersed. The aqueous solution to be dispersed is preferably prepared so that the concentration of the oil component (components other than water) is usually about 20 to 60% by weight. More preferably, it is 30 to 50% by weight.
[0034]
The aqueous solution to be dispersed is prepared by mixing the above components in advance. The aqueous solution to be dispersed can be preliminarily emulsified and dispersed by a general high-speed emulsification such as a rotary emulsifier.
[0035]
In the method for producing a polymer aqueous dispersion according to the present invention, the aqueous solution to be dispersed is injected at the ultrahigh pressure and the ultrahigh speed. As a result, a fine monomer aqueous dispersion having a volume average particle size of submicron or less can be obtained.
[0036]
As the emulsifying and dispersing machine for injecting the aqueous solution to be dispersed at an ultrahigh pressure and an ultrahigh speed, an ultrahigh pressure jet flow reversal emulsifying and dispersing machine (manufactured by Nippon BEE Co., Ltd.) can be used. FIG. 1 is a conceptual diagram of the emulsifying and dispersing machine. The emulsifying and dispersing machine has an inlet 1 for supplying an aqueous solution to be dispersed, and a nozzle assembly 2 for ejecting the aqueous solution to be dispersed at an ultrahigh pressure and an ultrahigh speed following the inlet 1. The jet liquid is introduced into the absorption (ABC) cell 4 through the jet port 2a. The nozzle assembly 2 adjusts the flow rate of the injection port 2a to control an ultra-high pressure and an ultra-high speed. A coupling 3 is replaceably provided between the injection port 1 and the injection port 2a. A laminar flow and a turbulent flow can be formed by the coupling 3, and the injection liquid can be premixed before injection. The plurality of absorption cells 4 are connected and held by a retainer 5. Further, a PEEK seal 6 is provided at a connection portion of the absorption cell 4. At the end of the absorption cell 4 in the direction of injection of the mixture, a reverse plug 7 or a feed plug 7 'is exchangeably provided. An outlet 8 (or an inlet 8 ′) is provided between the injection port 2 and the absorption cell 4.
[0037]
In the above-mentioned production method, for example, the ultrahigh-pressure jet flow inversion type emulsifying and dispersing machine (manufactured by Nippon BEE Co., Ltd.) is used in the mode of FIG. The aqueous solution to be dispersed is supplied to the injection port 1 by a high-pressure pump or the like, and is introduced into the absorption (ABC) cell 4 through the injection port 2a at an ultra-high pressure and an ultra-high speed. A reverse plug 7 is provided at the end of the absorption cell 4 in the injection direction of the mixture. The first fluid of the aqueous solution to be dispersed injected at an ultra-high speed passes through the center of the cell 4 and hits the reverse plug 7 to be inverted. The inverted second fluid flows back outside the inside of the cell 4, It is obtained from the outlet 8 provided between the injection port 2a and the absorption cell 4. The second fluid is mixed in the depression of the seal 6. For example, the super-high-speed mixture injected at the initial injection speed of 630 m / sec determined by Bernoulli's theorem contacts the liquid that reverses and flows backward to exchange energy, and the first mixture at the portion of the reverse plug 7. The flow velocity of the fluid was 2 m / sec, indicating that the energy was efficiently converted to emulsified dispersion of the liquid.
[0038]
Next, the obtained monomer aqueous dispersion is subjected to a usual radical polymerization reaction to copolymerize the monomer mixture. In the copolymerization, water is added to the aqueous monomer dispersion, and the oil concentration can be appropriately adjusted. Usually, it is preferable to adjust the oil concentration to about 20 to 60% by weight.
[0039]
The copolymerization is performed by heating. The heating temperature can be appropriately adjusted according to the type of the monomer mixture. Usually, it is about 60 to 80 ° C. The copolymerization is preferably performed in an atmosphere of an inert gas such as nitrogen.
[0040]
Thus, an aqueous dispersion of a polymer having an average particle size of submicron or less is obtained. The weight average molecular weight of the obtained polymer is not particularly limited, but is preferably about 0.5 to 500,000. Particularly, those having 10,000 to 300,000 are preferable. When the weight average molecular weight is less than 50,000, when used as a peelable polymer, the heat resistance is insufficient, and when it exceeds 500,000, the ability to form a peelable film tends to be inferior, which is not desirable.
[0041]
【Example】
Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples.
[0042]
Example 1
(Preparation of aqueous solution to be dispersed)
For 184 g of octadecyl methacrylate, 190 g of acrylonitrile, 3 g of 1-dodecanethiol, 1 g of azobisisobutyronitrile, 8 g of stearyltrimethylammonium chloride, and 3 g of polyethylene glycol monostearate (addition mole number of ethylene glycol is 140), the oil content is 45 weight. % Of water to prepare an aqueous solution to be dispersed.
[0043]
(Production of aqueous dispersion)
Next, an injection pressure of 1.8 × 10 3 was applied to the aqueous solution to be dispersed using DeBEE2000 (manufactured by Nippon BEE Co., Ltd.) of an ultra-high pressure jet flow inversion type emulsifying and dispersing apparatus shown in FIG. ⁸ Dispersion was performed at Pa and an initial injection speed of 370 m / sec. The volume average particle diameter of the obtained monomer aqueous dispersion was 0.2 μm. The injection pressure is a value measured by Instrument Quality Pressure Gauges of AUTOCLAVE ENGINEERS. The initial injection speed is a calculated value theoretically obtained based on the nozzle shape based on the injection pressure.
[0044]
Water was added to the obtained monomer aqueous dispersion to adjust the oil content to 33% by weight. This was placed in a flask equipped with a cooling tube, a nitrogen inlet, and a temperature sensor. After sufficiently performing nitrogen replacement, the mixture was heated to 70 ° C. to perform suspension polymerization to obtain a polymer aqueous dispersion. The volume average particle diameter of the obtained polymer aqueous dispersion was 0.2 μm.
[0045]
Example 2
(Preparation of aqueous solution to be dispersed)
To 134 g of octadecyl methacrylate, 210 g of acrylonitrile, 30 g of acrylic acid, 1.6 g of 2-mercaptoethanol, 1 g of benzoyl peroxide and 11 g of polyoxyethylene lauryl ether ammonium sulfate, water was added so that the oil content would be 45% by weight and dispersed. An aqueous solution was prepared.
[0046]
(Production of aqueous dispersion)
In Example 1, dispersion was performed under the same conditions as in Example 1 except that the aqueous solution to be dispersed was used, to obtain a monomer aqueous dispersion. The volume average particle diameter of the obtained monomer aqueous dispersion was 0.2 μm. In addition, suspension polymerization was performed on the obtained monomer aqueous dispersion in the same manner as in Example 1. The volume average particle diameter of the obtained polymer aqueous dispersion was 0.2 μm.
[0047]
Example 3
(Preparation of aqueous solution to be dispersed)
For 190 g of octadecyl acrylate, 154 g of acrylonitrile, 3 g of 1-dodecanethiol, 0.8 g of azobisisobutyronitrile, 10 g of stearyltrimethylammonium chloride and 3.5 g of polyethylene glycol monostearate (addition mole number of ethylene glycol is 140) Water was added so that the oil content became 45% by weight to prepare an aqueous solution to be dispersed.
[0048]
(Production of aqueous dispersion)
In Example 1, dispersion was performed under the same conditions as in Example 1 except that the aqueous solution to be dispersed was used, to obtain a monomer aqueous dispersion. The volume average particle size of the obtained monomer aqueous dispersion was 0.3 μm. In addition, suspension polymerization was performed on the obtained monomer aqueous dispersion in the same manner as in Example 1. The volume average particle diameter of the obtained polymer aqueous dispersion was 0.3 μm.
[0049]
Example 4
(Preparation of aqueous solution to be dispersed)
Water was added to 170 g of octadecyl methacrylate, 204 g of methacrylic acid, 4 g of 1-dodecanethiol, 1 g of azobisisobutyronitrile and 11 g of ammonium polyoxyethylene lauryl ether sulfate so that the oil content became 45% by weight, and the aqueous solution to be dispersed was added. Was prepared.
[0050]
(Production of aqueous dispersion)
In Example 1, dispersion was performed under the same conditions as in Example 1 except that the aqueous solution to be dispersed was used, to obtain a monomer aqueous dispersion. The volume average particle size of the obtained monomer aqueous dispersion was 0.3 μm. In addition, suspension polymerization was performed on the obtained monomer aqueous dispersion in the same manner as in Example 1. The volume average particle diameter of the obtained polymer aqueous dispersion was 0.3 μm.
[0051]
Comparative Example 1
Water was added to 184 g of octadecyl methacrylate, 190 g of acrylonitrile, 3 g of 1-dodecanethiol and 11 g of polyoxyethylene alkyl ether ammonium sulfate so that the oil content became 45% by weight to prepare an aqueous solution to be dispersed.
[0052]
This was emulsified and dispersed for 1 minute at 8000 rpm using a homomixer FK-2 (manufactured by Tokushu Kika Kogyo Co., Ltd.). The volume average particle diameter of the obtained emulsified dispersion (monomer aqueous dispersion) was 0.2 μm. The obtained emulsified dispersion is placed in a flask equipped with a cooling tube, a nitrogen inlet, and a temperature sensor, and after purging with nitrogen, the mixture is heated to 70 ° C., 1 g of ammonium persulfate is added as an initiator, and the mixture is emulsified with stirring. Polymerization was performed. The volume average particle size of the obtained emulsion polymer was 0.2 μm.
[0053]
Comparative Example 2
134 g of octadecyl methacrylate, 210 g of acrylonitrile, 30 g of acrylic acid, 1.6 g of 2-mercaptoethanol, 1 g of benzoyl peroxide and 11 g of polyoxyethylene lauryl ether ammonium sulfate were added with water so that the oil content was 45% by weight, and the aqueous solution to be dispersed was added. Was prepared.
[0054]
This was emulsified and dispersed for 1 minute at 8000 rpm using a homomixer FK-2 (manufactured by Tokushu Kika Kogyo Co., Ltd.). The volume average particle diameter of the obtained aqueous monomer dispersion was 2 μm. Next, suspension polymerization of this emulsified dispersion was carried out under the same conditions as in Example 1. The volume average particle diameter of the obtained polymer aqueous dispersion was 2 μm.
[0055]
The following evaluations were performed on the polymer aqueous dispersions or emulsion polymers obtained in Examples and Comparative Examples. Table 1 shows the results.
[0056]
[Volume average particle size]
The volume average particle size (μm) of the dispersion in the obtained aqueous dispersion was determined by performing a laser diffraction (scattering method) with a viscosity distribution measuring device (Horiba, Ltd.).
[0057]
[Film contamination]
The aqueous polymer dispersion or the emulsion polymer was applied on a polyethylene terephthalate film (thickness: 38 μm) so as to have a thickness of 0.2 μm, and a peelable film was formed by drying with a hot air drier at 120 ° C. for 3 minutes. A release sheet was prepared. This release sheet and a polyester adhesive tape No. 31B (manufactured by Nitto Denko Corporation) were bonded together and stored at 50 ° C. for 3 days to obtain a test sample.
[0058]
(Peeling force)
The peeling force (N / 20 mm) of the polyester adhesive tape No. 31B from the release sheet was measured with a Tensilon tensile tester (manufactured by Toyo Seisakusho) at a pulling speed of 300 mm / min (peeling angles 180 °, 23 ° C.).
[0059]
(Remaining force)
After peeling off the polyester adhesive tape No31B from the release sheet, the adhesive tape was attached to a SUS304 stainless steel plate, and the adhesive force after 30 minutes was measured by the above-mentioned tester under the same conditions. The residual force was expressed as% in comparison with the adhesive force of the No31B pressure-sensitive adhesive tape (blank), which was not in contact with the release sheet, with the SUS304 stainless steel plate, as 100%.
[0060]
[Table 1]

From Table 1, it can be seen that the polymer aqueous dispersions of the examples are all useful release agents having a volume average particle diameter of 1 μm or less, a low release force and a high residual contact force. From this, it can be seen that the polymer aqueous dispersion obtained in the examples was a copolymer having a desired composition ratio. On the other hand, Comparative Example 1 has the same type and composition ratio of the monomer mixture as in Example 1, but it can be seen that the obtained aqueous polymer dispersion has a large peeling force and a low residual force. From this, it can be seen that a copolymer having a desired composition ratio was not obtained in the polymer aqueous dispersion obtained in Comparative Example 1. Comparative Example 2 has the same type and composition ratio of the monomer mixture as in Example 2, but the obtained polymer aqueous dispersion has a large volume average particle size. Therefore, the residual contact force is low and not practical.
[Brief description of the drawings]
FIG. 1 is an example of an emulsifying and dispersing machine used in the production method of the present invention.
FIG. 2 is an embodiment of the emulsifying and dispersing machine of FIG.

Claims (9)

A monomer mixture containing at least two types of radically polymerizable monomers, an aqueous solution to be dispersed containing an initiator and a dispersing agent are dispersed by jetting at an injection pressure of 6.5 × 10 ⁷ Pa or more to disperse the monomer aqueous dispersion. And then copolymerizing the monomer aqueous dispersion to produce a polymer aqueous dispersion. The polymer aqueous dispersion according to claim 1, wherein the aqueous solution to be dispersed is injected at an injection pressure of 6.5 × 10 ^{7 to} 3.1 × 10 ⁸ Pa and an initial injection speed of 150 to 630 m / sec. Production method. The method for producing a polymer aqueous dispersion according to claim 1 or 2, wherein the radical polymerizable monomer includes a non-polar monomer having poor solubility in water and a polar monomer having good solubility in water. The polymer water according to any one of claims 1 to 3, wherein the nonpolar monomer having poor solubility in water is a (meth) acrylate ester having a long-chain alkyl group having 8 or more carbon atoms. A method for producing a dispersion. The polymer according to any one of claims 1 to 3, wherein the polar monomer having good solubility in water is at least one selected from acrylic acid, methacrylic acid, and acrylonitrile. Method. The polymer aqueous dispersion according to any one of claims 1 to 5, wherein the dispersant (dry weight) is blended in an amount of 10 parts by weight or less based on 100 parts by weight (dry weight) of the monomer mixture. Manufacturing method. The method for producing a polymer aqueous dispersion according to any one of claims 1 to 6, wherein the volume average particle diameter of the monomer aqueous dispersion is fine particles of 1 µm or less. A polymer aqueous dispersion obtained by the production method according to claim 1. An aqueous release agent comprising the polymer aqueous dispersion according to claim 8.

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