Emulsifier for emulsion polymerization and method for producing emulsion polymerization latex

Abstract

To provide: an emulsifier for emulsion polymerization, which suppresses generation of aggregates and has excellent polymerization stability and low foamability; and a method for producing an emulsion polymerization latex.SOLUTION: Provided is an emulsifier for emulsion polymerization, comprising a phosphoester compound represented by the following general formula (1). (In the formula, R is a C8-24 unsaturated aliphatic hydrocarbon group; AO is a C2-4 oxyalkylene group; n is an average number of moles of addition of alkylene oxide in a range of 1-30; m is an integer of 1-3; M is a hydrogen atom, an alkali metal atom, a Group 2 metal atom, an ammonium group, or an organic ammonium group).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a novel emulsifier for emulsion polymerization, which is characterized by suppressing the generation of aggregates when producing a latex by emulsion polymerization, having excellent polymerization stability, and having low foaming properties. [Background technology]

[0002] Resin emulsions, dried resin pellets, and resin powders are widely used as paints, adhesives, paper processing agents, fiber processing agents, resin modifiers, etc., and emulsion polymerization is often used as a method for producing them. Since emulsion-polymerized latex obtained by emulsion polymerization uses water as a solvent, its industrial importance is increasing from the viewpoint of environmental conservation and work safety. In this context, for example, the paint industry is rapidly switching from solvent-based paints to water-based emulsion-based paints.

[0003] Examples of emulsifiers for emulsion polymerization used in emulsion polymerization include nonionic surfactants such as polyoxyethylene alkyl ethers and polyoxyethylene alkyl phenyl ethers, and anionic surfactants such as alkylbenzene sulfonates, polyoxyethylene alkyl sulfates, polyoxyethylene alkyl phenyl sulfates, and higher fatty acid salts. These emulsifiers for emulsion polymerization are essential for smoothly advancing emulsion polymerization and suppressing the generation of aggregates, but the emulsifiers remaining in the generated emulsion cause foaming, and in paint applications, for example, cause adverse effects such as the generation of pinholes in the coating film. For this reason, there is a high demand for low-foaming emulsifiers for emulsion polymerization, and many have been proposed, such as styrenated phenol-based emulsifiers (Patent Document 1), emulsifiers with a specific molecular weight distribution (Patent Document 2), and emulsifiers made from natural unsaturated alcohols (Patent Document 3), but the current situation is that there is still no emulsifier that satisfies the performance. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 8-113602 [Patent Document 2] JP 2001-300283 A [Patent Document 3] JP2004-002644A Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has an object to solve the above-mentioned problems in the conventional art, and to provide a novel emulsifier for emulsion polymerization, which is characterized by suppressing the generation of aggregates, excellent polymerization stability, and low foaming property when producing a latex by emulsion polymerization, and a method for producing an emulsion-polymerized latex, which is characterized by using the same. [Means for solving the problem]

[0006] Means for Solving the Problems The present inventors have conducted intensive research to achieve the above object and have found that, when a phosphoric acid ester compound having a specific structure is used in producing a latex by emulsion polymerization, the generation of aggregates can be suppressed, the polymerization stability is excellent, and further, the foaming property is low, and thus the present invention has been completed.

[0007] That is, the present invention provides [1] Chemical formula (1): [ka] (In the formula, R is an unsaturated aliphatic hydrocarbon group having 8 to 24 carbon atoms, AO is an oxyalkylene group having 2 to 4 carbon atoms, n is a number from 1 to 30 which is the average number of moles of alkylene oxide added, m is an integer from 1 to 3, and M is a hydrogen atom, an alkali metal atom, a Group 2 metal atom, an ammonium group, or an organic ammonium group.) An emulsifier for emulsion polymerization, comprising a phosphoric acid ester compound represented by the formula: [2] The emulsifier for emulsion polymerization according to [1], wherein in the chemical formula (1), R is an alkenyl group having 12 to 22 carbon atoms. [3] The emulsifier for emulsion polymerization according to [1], wherein in the chemical formula (1), R is an oleyl group. [4] The present invention relates to a method for producing an emulsion polymerization latex, which comprises emulsion polymerizing an unsaturated monomer in the presence of the emulsifier for emulsion polymerization according to any one of [1] to [3]. Effect of the Invention

[0008] The emulsifier for emulsion polymerization of the present invention exhibits the effects of suppressing the generation of aggregates when producing a latex by emulsion polymerization, being excellent in polymerization stability, and simultaneously satisfying low foaming properties. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The emulsifier for emulsion polymerization of the present invention contains a phosphoric acid ester compound represented by the following general formula (1).

[0010] [ka] (In the formula, R is an unsaturated aliphatic hydrocarbon group having 8 to 24 carbon atoms, AO is an oxyalkylene group having 2 to 4 carbon atoms, n is a number from 1 to 30 which is the average number of moles of alkylene oxide added, m is an integer from 1 to 3, and M is a hydrogen atom, an alkali metal atom, a Group 2 metal atom, an ammonium group, or an organic ammonium group.)

[0011] Specific examples of the unsaturated aliphatic hydrocarbon group having 8 to 24 carbon atoms include alkenyl groups such as an octenyl group, a nonenyl group, a decenyl group, a dodecenyl group, a tridecenyl group, a tetradecenyl group, a pentadecenyl group, a hexadecenyl group, a heptadecenyl group, an octadecenyl group, an oleyl group (cis-9-octadecenyl group), an elaidyl group (trans-9-octadecenyl group), an eicosenyl group, a docosenyl group, and a tetracosenyl group; alkadienyl groups such as an octadecadienyl group, a linoleyl group (cis,cis-9,12-octadecadienyl group), and an elaidolinoleyl group (trans,trans-9,12-octadecadienyl group); and alkatrienyi groups such as an octadecatrienyl group. Among these, from the viewpoint of having good low foaming properties, alkenyl groups having 12 to 22 carbon atoms are preferred, and in particular, a hexadecenyl group, a heptadecenyl group, an octadecenyl group, and an oleyl group are preferred.

[0012] In the general formula (1), AO is an oxyalkylene group having 2 to 4 carbon atoms, specifically an oxyethylene group, a 1,2- or 1,3-oxypropylene group, and a 1,2-, 1,3-, or 1,4-oxybutylene group. Among these, preferred are an oxyethylene group and a 1,2-oxypropylene group, and particularly preferred is an oxyethylene group. n is the average number of moles of alkylene oxide added, and is a number from 1 to 30, but is preferably a number from 2 to 10 from the viewpoint of emulsifiability. When n is 2 or more, n AOs may be the same or different, and when they are different, it is -(AO) n The addition may be in the form of random addition, block addition, or alternating addition.

[0013] In the general formula (1), M is a hydrogen atom, an alkali metal atom, a Group 2 metal atom, an ammonium group, or an organic ammonium group. Examples of alkali metals include lithium (Li), sodium (Na), and potassium (K), and examples of Group 2 metals include beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba). The organic ammonium group is an ammonium group derived from an organic amine, and examples of the organic amine include alkanolamines such as monoethanolamine, diethanolamine, and triethanolamine, methylamine, dimethylamine, triethylamine, ethylamine, diethylamine, and triethylamine.

[0014] In the above general formula (1), m is an integer of 1 to 3, and preferably 1 or 2. The phosphate ester compound represented by formula (1) is a phosphate monoester or a salt thereof when m is 1, a phosphate diester or a salt thereof when m is 2, and a phosphate triester when m is 3. The emulsifier for emulsion polymerization of the present invention contains one compound or a mixture of two or more compounds selected from the group consisting of phosphoric acid monoesters and salts thereof, phosphoric acid diesters and salts thereof, and phosphoric acid triesters. The ratio of phosphoric acid monoester or its salt / phosphate in the total amount of the phosphoric acid ester compound represented by formula (1) From the viewpoint of emulsifying property, the ratio of phosphoric acid diester or its salt / phosphoric acid triester is It is preferable that the content of the polyester or its salt is 10 to 70% by mass, and it is preferable that the content of the polyester or its salt is 20 to 60% by mass. More preferably, the phosphoric acid diester or its salt is 30 to 90% by mass, and 40 to 50% by mass. It is more preferable that the content of the phosphate triester is 0 to 10% by mass. It is preferable that the content be 0 to 5% by mass.

[0015] The emulsifier for emulsion polymerization of the present invention may contain components other than the above phosphoric acid ester compounds, as long as the object of the present invention is not impaired. For example, polyoxyalkylene alkenyl ether remaining as an unreacted raw material of the phosphoric acid ester compounds, phosphoric acid compounds such as metaphosphoric acid, pyrophosphoric acid, orthophosphoric acid, triphosphoric acid, and tetraphosphoric acid, etc. may be mentioned.

[0016] Examples of unsaturated monomers that can be used in emulsion polymerization using the emulsifier for emulsion polymerization according to the present invention include acrylic monomers such as acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methacrylic acid, methyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl methacrylate, acrylonitrile, acrylamide, and methacrylamide, aromatic monomers such as styrene, α-methylstyrene, vinyltoluene, p-methylstyrene, and divinylbenzene, vinyl ester monomers such as vinyl acetate, monoolefins or conjugated diolefins such as ethylene, butadiene, and isoprene, halogenated vinyl monomers such as chloroprene, vinyl chloride, vinylidene chloride, and vinyl bromide, and other monomers such as itaconic acid, fumaric acid, maleic acid, and methyl maleate, but are not limited to these monomers. These monomers can be used alone or in combination.

[0017] As the polymerization initiator, for example, known polymerization initiators such as potassium persulfate, ammonium persulfate, hydrogen peroxide, azobisisobutyronitrile, t-butyl hydroperoxide, benzoyl peroxide, etc. Redox polymerization may also be carried out using a reducing substance such as sodium hydrogen sulfite, sodium thiosulfate, ferrous sulfate, etc.

[0018] A chain transfer agent can also be used in combination, such as t-dodecyl mercaptan, dodecyl mercaptan, carbon tetrachloride, chloroform, or triphenylmethane.

[0019] Furthermore, additives commonly used in emulsion polymerization methods can be used, such as chelating agents, buffers, salts of organic acids, solvents, etc. As the solvent, in addition to water, organic solvents such as alcohols, glycols, and glycol ethers can be used, with water being preferred.

[0020] The emulsion polymerization method may be any commonly used method such as a batch polymerization method or a continuous polymerization method. In the case of a batch polymerization method, the solvent, the emulsifier, the monomer, and the initiator may be charged all at once, or the monomer and the initiator may be added dropwise. The polymerization temperature and polymerization time depend on the polymerizability of the monomer and the initiator, but are usually 20 to 130°C, preferably 30 to 100°C.

[0021] The amount of the emulsifier for emulsion polymerization of the present invention varies depending on the type of monomer and polymerization conditions, but is usually in the range of 0.1 to 10% by weight based on the total monomers, and preferably in the range of 0.3 to 5% by weight for effective and economical reasons. In addition, nonionic surfactants such as polyoxyethylene alkyl ethers and polyoxyethylene alkyl phenyl ethers, anionic surfactants such as alkylbenzene sulfonates, polyoxyethylene alkyl ether sulfates, polyoxyethylene alkyl phenyl ether sulfates, and polyoxyethylene alkyl ether phosphates, cationic surfactants, and other known emulsifiers and various stabilizers may be used in combination within a range that does not impair the object of the present invention.

[0022] The emulsion polymerization latex produced by using the emulsifier for emulsion polymerization of the present invention is not particularly limited and can be applied to various things. For example, it can be used to produce acrylate-based latex, styrene-based latex, vinyl acetate-based latex, SBR (styrene / butadiene) latex, ABS (acrylonitrile / butadiene / styrene) latex, BR (butadiene) latex, IR (isoprene) latex, NBR (acrylonitrile / butadiene) latex, etc., and two or more kinds of monomers can be mixed and emulsion polymerized. EXAMPLES

[0023] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these. Unless otherwise specified, the blend amounts are shown in parts by mass.

[0024] The structures of the phosphoric acid ester compounds used in the examples and comparative examples for the production of emulsion-polymerized latexes are shown in Table 1 below. In the table, EO represents an oxyethylene group. The molar ratio of the phosphoric acid monoester to the phosphoric acid diester in each phosphoric acid ester compound is monoester / diester=50 / 50. Incidentally, Example 5 in which emulsifier (5) was used is a reference example.

[0025] [Table 1]

[0026] <Example of emulsion polymerization latex production> Example 1 Into a polymerization vessel equipped with a cooler, 190 parts of ion-exchanged water was charged and heated to 80°C. Furthermore, a mixture prepared by adding 0.40 parts of sodium formaldehyde sulfoxylate, 0.00004 parts of ferrous sulfate, and 0.0001 parts of EDTA to 5 parts of ion-exchanged water was charged all at once. On the other hand, 9 parts of ion-exchanged water was charged into another vessel equipped with a stirrer, and then 25 parts of methyl methacrylate, 25 parts of butyl acrylate, and 0.08 parts of t-butyl hydroperoxide were added and mixed by stirring. Next, 1.5 parts of emulsifier (1) shown in Table 1 were added to the vessel while stirring, and stirring was continued for 20 minutes again to prepare a monomer emulsion. Next, while stirring the inside of the polymerization vessel under nitrogen, 10 g of the prepared monomer emulsion was dropped, and the reaction was continued for 15 minutes, and the remainder was dropped over 90 minutes. Next, 5 parts of ion-exchanged water and 0.2 parts of sodium formaldehyde sulfoxylate were added. Further, 10 parts of ion-exchanged water was charged into another vessel equipped with a stirrer, and then monomer components consisting of 10 parts of styrene and 50 parts of butyl acrylate and 0.1 parts of t-butyl hydroperoxide were charged and mixed with stirring. Next, 2 parts of emulsifier (1) shown in Table 1 was charged into the vessel with stirring, and stirring was continued again for 20 minutes to prepare a monomer emulsion, which was added dropwise into the polymerization vessel over 120 minutes, and the reaction was continued for 120 minutes to obtain an emulsion polymerization latex.

[0027] The amount of aggregates, solid content, foamability, and stability over time of the obtained emulsion polymerized latex were evaluated according to the following evaluation methods. The results are shown in Table 2.

[0028] (1) Amount of aggregates The latex after emulsion polymerization was filtered through a 200 μm stainless steel mesh, and the weight of the residue after drying was evaluated in terms of weight % relative to the total monomers.

[0029] (2) Solids About 1 g of the emulsion polymerized latex was weighed into an aluminum cup, and the weight after drying for 2 hours in a dryer at 105° C. was evaluated as a weight percentage relative to the emulsion polymerized latex before drying.

[0030] (3) Foaming property The emulsion polymerized latex was diluted two-fold with ion-exchanged water, 50 mL of which was placed in a 100 mL measuring cylinder with a stopper, shaken for 20 seconds, and the amount of foam after standing was evaluated.

[0031] (4) Stability over time The emulsion-polymerized latex was placed in a 100 mL glass container, sealed and stored at 25° C., and the state of separation of the emulsion-polymerized latex was visually confirmed. No separation: Yes Slight separation: △ Clear separation: ×

[0032] Examples 2 to 5 Except for using emulsifiers (2) to (5) shown in Table 1, emulsion polymerization latexes were prepared in the same manner as in Example 1, and the amount of aggregates, solid content, foamability, and stability over time were similarly evaluated. The results are shown in Table 2.

[0033] Comparative Examples 1 to 7 Except for using emulsifiers (6) to (12) shown in Table 1, emulsion polymerization latexes were prepared in the same manner as in Example 1, and the amount of aggregates, solid content, foamability, and stability over time were similarly evaluated. The results are shown in Table 2.

[0034] [Table 2]

[0035] From the results of the Examples, it is seen that the emulsion polymerization latex using the emulsifier for emulsion polymerization of the present invention has an amount of aggregate generation that does not cause problems when producing a synthetic resin by emulsion polymerization, has polymerization stability, and is excellent in low foaming property. In contrast, the emulsion polymerized latex using the emulsifier of the comparative example foamed significantly, with bubbles still remaining even after 10 minutes.

Claims

1. The following chemical formula (1): 【Chemistry 1】 (In the formula, R is an alkenyl group having 12 to 22 carbon atoms, AO is an oxyalkylene group having 2 to 4 carbon atoms, n is a number from 1 to 30 which is the average number of moles of alkylene oxide added, m is an integer from 1 to 3, and M is an alkali metal atom, a Group 2 metal atom, an ammonium group, or an organic ammonium group derived from an organic amine selected from monoethanolamine, diethanolamine, triethanolamine, methylamine, dimethylamine, ethylamine, diethylamine, and triethylamine.) An emulsifier for emulsion polymerization, comprising a phosphoric acid ester compound represented by the formula:

2. 2. The emulsifier for emulsion polymerization according to claim 1, wherein in said chemical formula (1), R is an oleyl group.

3. 3. A method for producing an emulsion polymerization latex, which comprises emulsion polymerizing an unsaturated monomer in the presence of the emulsifier for emulsion polymerization according to claim 1 or 2.

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