JP2012172063A - Long chain (meth)acrylate-based emulsion and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an emulsion containing a (meth)acrylate-based copolymer having a long chain alkyl group, and a method for producing the emulsion.SOLUTION: The long chain (meth)acrylate emulsion includes a copolymer obtained by emulsion polymerization of a monomer mixture including a (meth)acrylate having a ≥16C linear alkyl group, a (meth)acrylate having a 1-8C alkyl group, and a polar monomer in an aqueous medium. The method for producing the long chain (meth)acrylate-based emulsion includes: a process of obtaining a dispersion (A) by dispersing the monomer mixture in the aqueous medium to which a surfactant is added; a process of obtaining a dispersion (B) by adding a protective colloid to the dispersion (A); and a process of performing emulsion polymerization of the monomer mixture by adding a polymerization initiator to the dispersion (B).

Description

  The present invention relates to an emulsion containing a (meth) acrylate copolymer having a long-chain alkyl group and a method for producing the emulsion.

  A (meth) acrylate copolymer having a long-chain alkyl group is generally known as a side-chain crystalline polymer (see, for example, Patent Document 1). The side chain crystalline polymer contains (meth) acrylate having a straight chain alkyl group having 16 or more carbon atoms as a long chain alkyl group as a monomer unit, and has a melting point due to the long chain alkyl group. Yes. The side chain crystalline polymer exhibits fluidity and develops tackiness when heated to a temperature above this melting point, and has the property of crystallizing and lowering the adhesive strength when cooled to a temperature below the melting point. Therefore, it is used for adhesive applications.

  However, the conventional side chain crystalline polymer as described in Patent Document 1 is produced by a solution polymerization method. In view of environmental impact and safety, it is desirable to make the side chain crystalline polymer aqueous.

JP-A-9-251923

  The subject of this invention is providing the emulsion containing the (meth) acrylate type copolymer which has a long-chain alkyl group, and its manufacturing method.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found a solution means having the following constitution and have completed the present invention.
(1) A monomer mixture containing a (meth) acrylate having a linear alkyl group having 16 or more carbon atoms, a (meth) acrylate having an alkyl group having 1 to 8 carbon atoms, and a polar monomer in an aqueous medium A long-chain (meth) acrylate emulsion characterized by containing a copolymer obtained by emulsion polymerization with a polymer.
(2) The long-chain (meth) acrylate emulsion according to (1), wherein the aqueous medium is water.
(3) A monomer mixture containing a (meth) acrylate having a linear alkyl group having 16 or more carbon atoms, a (meth) acrylate having a C 1-8 alkyl group, and a polar monomer, to which a surfactant is added. A step of obtaining a dispersion liquid (A) by dispersing in a medium, a step of obtaining a dispersion liquid (B) by adding a protective colloid to the dispersion liquid (A), and adding a polymerization initiator to the dispersion liquid (B) And a step of emulsion polymerization of the monomer mixture. A method for producing a long-chain (meth) acrylate emulsion.
(4) The method for producing a long-chain (meth) acrylate emulsion according to (3), wherein the surfactant has an HLB value of 14 to 18.
(5) The long-chain (meth) acrylate emulsion according to (3) or (4), wherein the addition amount of the surfactant is 5 to 15 parts by weight in terms of solid content with respect to 100 parts by weight of the monomer mixture. Production method.
(6) The method for producing a long-chain (meth) acrylate emulsion according to any one of (3) to (5), wherein the aqueous medium is water.
(7) The monomer mixture is stirred by a stirring means, and the aqueous medium is added to the stirred monomer mixture to obtain the dispersion (A). (3) to (6) A method for producing a long-chain (meth) acrylate emulsion.
(8) The long chain (meth) acrylate according to any one of (3) to (7), wherein the addition amount of the protective colloid is 1 to 9 parts by weight in terms of solid content with respect to 100 parts by weight of the monomer mixture. A method for producing an emulsion.

  According to the present invention, a mixture of monomers constituting the above-mentioned side chain crystalline polymer is emulsion-polymerized in an aqueous medium to form a copolymer, and an aqueous emulsion containing this copolymer is obtained. It is less pollutant than the conventional side chain crystalline polymer manufactured by the company, therefore it has less impact on the environment, is superior in safety against fire and handling, and can also save resources. effective. And if water is employ | adopted as an aqueous medium, solvent-free can be achieved.

  The long-chain (meth) acrylate emulsion of the present invention (hereinafter sometimes referred to as “emulsion”) is a (meth) acrylate having a linear alkyl group having 16 or more carbon atoms, and 1 to 8 carbon atoms. It is an aqueous emulsion containing a copolymer obtained by emulsion polymerization of a monomer mixture containing a (meth) acrylate having an alkyl group and a polar monomer in an aqueous medium.

  Examples of the (meth) acrylate having a linear alkyl group having 16 or more carbon atoms include 16 to 22 carbon atoms such as cetyl (meth) acrylate, stearyl (meth) acrylate, eicosyl (meth) acrylate, and behenyl (meth) acrylate. (Meth) acrylates having a linear alkyl group can be used, and these may be used alone or in combination of two or more.

  Examples of the (meth) acrylate having an alkyl group having 1 to 8 carbon atoms include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, and the like. Alternatively, two or more kinds may be mixed and used.

  Examples of polar monomers include carboxyl group-containing ethylenically unsaturated monomers such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, and fumaric acid; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meta ), Hydroxyl group-containing ethylenically unsaturated monomers such as acrylate and 2-hydroxyhexyl (meth) acrylate, and the like. These may be used alone or in combination of two or more.

  The monomer mixture containing each monomer described above is 30 to 70 parts by weight of a (meth) acrylate having a linear alkyl group having 16 or more carbon atoms and 29 to (meth) acrylate having an alkyl group having 1 to 8 carbon atoms. Although it is preferable to contain 70 weight part and a polar monomer in the ratio of 1-10 weight part, it is not limited to this.

  Examples of the aqueous medium include water, a mixed medium of water and a water-soluble organic solvent, and the like. In order to eliminate the solvent, water alone is preferable. In the case of using a mixed medium of water and a water-soluble organic solvent, it is preferable that the content of water is larger than the content of the water-soluble organic solvent in view of environmental impact and safety. Examples of the water-soluble organic solvent include water-soluble alcohols such as methanol, ethanol, propanol and butanol; acetone and the like, and these may be used alone or in combination of two or more.

  Here, among the monomers contained in the monomer mixture, the (meth) acrylate having a linear alkyl group having 16 or more carbon atoms is hydrophobic, and the (meth) acrylate having an alkyl group having 1 to 8 carbon atoms and All polar monomers are hydrophilic. Such a monomer mixture in which a specific hydrophobic monomer and a hydrophilic monomer are combined tends to be difficult to emulsion-polymerize in an aqueous medium. In the present invention, this monomer mixture is subjected to emulsion polymerization in an aqueous medium through the following steps.

  First, the monomer mixture described above is dispersed in an aqueous medium to which a surfactant is added to obtain a dispersion (A). Examples of the surfactant include an anionic surfactant, a cationic surfactant, an amphoteric surfactant, a nonionic surfactant, a reactive surfactant, and the like, and a nonionic surfactant is particularly preferable. It is.

  Nonionic surfactants include, for example, polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene nonyl phenyl ether, polyethylene glycol dilaurate, polyethylene glycol distearate. , Polyoxyethylene sorbitan monostearate, sorbitan monolaurate and the like, and these may be used alone or in combination of two or more.

  The HLB value of the surfactant is preferably 14-18. The HLB value is a value representing the degree of affinity of the surfactant with water and oil. If the HLB value is too small or large, the emulsion may be separated after emulsion polymerization.

  Further, for the same reason as described for the HLB value, the cloud point of the surfactant is preferably 70 ° C. or higher.

  The addition amount of the surfactant is preferably 5 to 15 parts by weight in terms of solid content with respect to 100 parts by weight of the monomer mixture. If the amount of the surfactant added is too small or large, the surfactant may be separated after the emulsion polymerization. The surfactant may be added alone, or may be added after a solution previously dissolved or diluted with an aqueous medium or the like.

  The proportion of the aqueous medium to which the above-mentioned surfactant is added is preferably 50 to 400 parts by weight, more preferably 100 to 300 parts by weight with respect to 100 parts by weight of the monomer mixture. If the proportion of the aqueous medium is too small, the viscosity increases and handling properties decrease, and if it is too large, the productivity decreases, which is not preferable. The total amount of the aqueous medium may be added all at once, or may be added in multiple portions.

  The dispersion (A) is preferably obtained by bringing the monomer mixture into a stirring state with stirring means and adding an aqueous medium to the stirring monomer mixture. After adding the aqueous medium, the mixture is heated at 50 to 80 ° C. with stirring. It is more preferable to obtain the temperature state and hold this state for about 10 to 60 minutes. Thereby, a dispersion liquid (A) can be obtained easily. The resulting dispersion (A) is usually in an emulsified state.

  Examples of the stirring means include a stirrer, but are not limited thereto as long as the monomer mixture can be brought into a stirring state. Further, the stirring speed is not particularly limited, and can be set as appropriate.

  A protective colloid is added to the obtained dispersion liquid (A) to obtain a dispersion liquid (B). Examples of protective colloids include polyvinyl alcohols such as partially saponified polyvinyl alcohol, fully saponified polyvinyl alcohol, and modified polyvinyl alcohol; cellulose derivatives such as hydroxyethyl cellulose, hydroxypropyl cellulose, and carboxymethyl cellulose salt; and natural polysaccharides such as guar gum. These may be used, and one kind or a mixture of two or more kinds may be used.

  The addition amount of the protective colloid is preferably 1 to 9 parts by weight in terms of solid content with respect to 100 parts by weight of the monomer mixture. If the amount of protective colloid added is too small or large, it may be separated after emulsion polymerization. The protective colloid may be added alone, or may be added after previously dissolving or diluting with an aqueous medium or the like.

  A polymerization initiator is added to this dispersion (B) to carry out emulsion polymerization of the monomer mixture. Examples of the polymerization initiator include persulfates such as potassium persulfate, ammonium persulfate, and sodium persulfate; perchloric acid compounds; perboric acid compounds; benzoyl hydroperoxide, benzoyl peroxide, cumene hydroperoxide, tertiary hydro Peroxides such as peroxides and hydrogen peroxide; azo compounds such as 4,4′-azobis (4-cyanopentanoic acid) and azobisisobutyronitrile; potassium persulfate-sodium thiosulfate, hydrogen peroxide -The redox type | system | group initiator etc. which consist of a combination of peroxides, such as ascorbic acid, and a reducing compound are mentioned.

  The addition amount of the polymerization initiator is preferably 0.05 to 2 parts by weight and more preferably 0.05 to 1 part by weight with respect to 100 parts by weight of the monomer mixture. If the addition amount of the polymerization initiator is too small, it is not preferable because the polymerization rate becomes slow and the time required for the completion of the polymerization becomes long. On the other hand, if the polymerization initiator is added too much, the polymerization rate becomes too fast, the reaction heat generated becomes large, and the control of the reaction temperature becomes difficult.

  The polymerization initiator may be added alone, or may be added after a solution previously dissolved or diluted with an aqueous medium or the like. The addition rate of the polymerization initiator is not particularly limited as long as the monomer mixture can be subjected to emulsion polymerization, and can be appropriately set.

  Emulsion polymerization is preferably performed by heating to 50 to 80 ° C. with stirring and maintaining this state for about 2 to 6 hours. Moreover, it is preferable to perform emulsion polymerization in inert gas atmosphere, such as nitrogen gas and argon gas. In addition, it is preferable to carry out in inert gas atmosphere also in each process of obtaining the dispersion liquid (A) and (B) mentioned above.

  The copolymer obtained by emulsion polymerization is obtained in the form of an aqueous emulsion in which particles are dispersed in an aqueous medium. The average particle size of the emulsion is about 200 to 1000 nm, but is not limited thereto. As solid content concentration of an emulsion, it is preferable that it is 20 to 66 weight%, and it is more preferable that it is 25 to 50 weight%. When the solid content concentration is too low, the productivity is lowered, and when it is too high, the viscosity is increased and the handling property is lowered, which is not preferable.

  The copolymer contained in the emulsion is a side-chain crystalline polymer that crystallizes at a temperature below the melting point and exhibits phase transition at a temperature above the melting point and exhibits fluidity. Therefore, the long-chain (meth) acrylate emulsion of the present invention containing this copolymer can be suitably used for adhesive applications and the like, but is not limited thereto.

  As a usage form of the long-chain (meth) acrylate emulsion of the present invention, for example, it can be applied directly to an adherend or the like, or can be used after being sprayed and dried to form a film. In addition, if the long chain (meth) acrylate emulsion of the present invention is applied to one or both sides of a base film and dried, it can be used in a tape form and further applied onto a release film. If it is dried, it can be used in the form of a substrate-less film or sheet.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited only to a following example. In the following description, “part” means part by weight.

In the examples, the materials used for the production of the long chain (meth) acrylate emulsion are as follows.
Surfactant (1): “Nonion NS-210” manufactured by NOF Corporation having an HLB value of 13.3 and a cloud point of 45 to 55 ° C. was used.
Surfactant (2): “Nonion NS-212” manufactured by NOF Corporation having an HLB value of 14.1 and a cloud point of 70 to 85 ° C. was used.
Surfactant (3): “Nonion NS-215” manufactured by NOF Corporation having an HLB value of 15.0 and a cloud point of 85 to 100 ° C. was used.
Surfactant (4): “Nonion NS-220” manufactured by NOF Corporation having an HLB value of 16.0 and a cloud point of 100 <° C. was used.
Surfactant (5): “Nonion NS-230” manufactured by NOF Corporation having an HLB value of 17.1 and a cloud point of 100 <° C. was used.
Surfactant (6): “Nonion NS-270” manufactured by NOF Corporation having an HLB value of 18.7 and a cloud point of 100 <° C. was used.
The surfactants (1) to (6) are all nonionic surfactants made of polyoxyethylene nonylphenyl ether.

Aqueous medium: ion-exchanged water, protective colloid: “PVA224” manufactured by Kuraray Co., Ltd., which is partially saponified polyvinyl alcohol having a saponification degree of 88% was used.
-Polymerization initiator: Potassium persulfate was used.

<Manufacture of long chain (meth) acrylate emulsion>
First, 45 parts of behenyl acrylate, 50 parts of methyl acrylate, and 5 parts of acrylic acid were mixed to obtain a monomer mixture. Next, this monomer mixture is added to a separable flask equipped with a stirrer and a gas introduction tube, and nitrogen gas is introduced from the gas introduction tube into a nitrogen gas atmosphere, and the mixture is stirred with a stirrer at a rotation speed of 120 rpm. I made it. In addition, the stirrer with the shaft which equip | provided the substantially rectangular flat plate-shaped stirring blade at the front-end | tip was used for the stirrer.

  Next, an aqueous medium in which a surfactant was dissolved in advance was added to the stirred monomer mixture. The aqueous medium was 220 parts in total with respect to 100 parts of the monomer mixture, and 120 parts of this was added to the stirred monomer mixture. Table 1 shows the types and addition amounts of the surfactants dissolved in the aqueous medium. In addition, the addition amount of the surfactant in Table 1 is a value in terms of solid content with respect to 100 parts of the monomer mixture.

  After the aqueous medium was added, the mixture was heated to 70 ° C. with stirring, and this state was maintained for 30 minutes to obtain a dispersion (A). The obtained dispersion (A) was in an emulsified state.

  Next, a protective colloid was added to the dispersion (A), and the mixture was heated to 70 ° C. with stirring, and this state was maintained for 1 hour to obtain a dispersion (B). The protective colloid was added as a solution previously dissolved in an aqueous medium. The aqueous medium used for dissolving the protective colloid used 90 parts of the total amount described above. The amount of protective colloid added is as shown in Table 1. The addition amount of the protective colloid in Table 1 is a value in terms of solid content with respect to 100 parts of the monomer mixture.

  A polymerization initiator was added to the obtained dispersion (B), and the mixture was heated to 70 ° C. with stirring, and this state was maintained for 4 hours to carry out emulsion polymerization to obtain an emulsion (samples in Table 1). No. 1-13). The addition amount of the polymerization initiator was 0.3 parts with respect to 100 parts of the monomer mixture. The polymerization initiator was previously dissolved in an aqueous medium and added dropwise to the dispersion (B) over 1 minute. The remaining 10 parts of the total amount described above was used as the aqueous medium used for dissolving the polymerization initiator.

<Evaluation>
About the obtained emulsion, melting | fusing point and storage stability were evaluated. Each evaluation method is shown below, and the results are also shown in Table 1.

(Melting point)
Whether or not emulsion polymerization was performed was determined from the melting point. That is, the monomer mixture described above was polymerized in advance, and the melting point of the obtained copolymer was measured. Then, the melting point of the copolymer obtained by the solution polymerization is compared with the melting point of the copolymer obtained by the emulsion polymerization described above, and if the difference between the two melting points is within a range of ± 5 ° C. It was determined that emulsion polymerization was performed as a quantitative copolymer.

  By melting point is meant the temperature at which a certain portion of the polymer that was initially aligned in an ordered arrangement becomes disordered by some equilibrium process. The melting point was measured using a differential thermal scanning calorimeter (DSC) under measurement conditions of 10 ° C./min. The solution polymerization was performed by adding the above monomer mixture to 230 parts of ethyl acetate and stirring at 55 ° C. for 4 hours.

(Left stability)
The state after leaving the emulsion at 23 ° C. for 1 week was evaluated by visual observation.

  The melting point of the copolymer obtained by solution polymerization of the above monomer mixture was 57 ° C. As is clear from Table 1, sample No. 1 to 13 are all emulsion-polymerized because the difference from the melting point of the copolymer obtained by solution polymerization is within ± 5 ° C. Therefore, sample no. It can be said that all of 1 to 13 are long-chain (meth) acrylate emulsions containing a copolymer obtained by emulsion polymerization in an aqueous medium.

  Sample No. 1 to 13, the HLB value of the surfactant is 14 to 18, the addition amount of the surfactant is 5 to 15 parts in terms of solid content with respect to 100 parts of the monomer mixture, and the addition amount of the protective colloid is Sample No. 1 to 9 parts in terms of solid content with respect to 100 parts of the monomer mixture. Nos. 2-5, 8, 9, 12 had good standing stability. These sample Nos. Nos. 2, 5, 8, 9, and 12 maintained a stable state even after being left at an ambient temperature of 23 ° C. for 6 months.

Claims (8)

(Meth) acrylate having a linear alkyl group having 16 or more carbon atoms;
(Meth) acrylate having an alkyl group having 1 to 8 carbon atoms;
A polar monomer;
A long-chain (meth) acrylate emulsion characterized by containing a copolymer obtained by emulsion polymerization of a monomer mixture containing an aqueous medium.   The long-chain (meth) acrylate emulsion according to claim 1, wherein the aqueous medium is water. Disperse a monomer mixture containing (meth) acrylate having a linear alkyl group having 16 or more carbon atoms, (meth) acrylate having an alkyl group having 1 to 8 carbon atoms and a polar monomer in an aqueous medium to which a surfactant is added. And obtaining a dispersion liquid (A),
Adding a protective colloid to the dispersion (A) to obtain a dispersion (B);
Adding a polymerization initiator to the dispersion (B) and performing emulsion polymerization of the monomer mixture;
A process for producing a long-chain (meth) acrylate-based emulsion, comprising:   The method for producing a long-chain (meth) acrylate emulsion according to claim 3, wherein the surfactant has an HLB value of 14 to 18.   The method for producing a long-chain (meth) acrylate emulsion according to claim 3 or 4, wherein the addition amount of the surfactant is 5 to 15 parts by weight in terms of solid content with respect to 100 parts by weight of the monomer mixture.   The method for producing a long-chain (meth) acrylate emulsion according to any one of claims 3 to 5, wherein the aqueous medium is water.   The long-chain (meth) acrylate according to any one of claims 3 to 6, wherein the monomer mixture is stirred by a stirring means, and the aqueous medium is added to the stirred monomer mixture to obtain the dispersion (A). A method for producing an emulsion.   The method for producing a long-chain (meth) acrylate emulsion according to any one of claims 3 to 7, wherein the addition amount of the protective colloid is 1 to 9 parts by weight in terms of solid content with respect to 100 parts by weight of the monomer mixture.