ACRYLIC EMULSION

Abstract

The present invention addresses the problem of providing an emulsion having excellent emulsion stability and excellent coagulability (salting-out properties) in manufacturing of an acrylic rubber. The present invention provides an acrylic emulsion containing an acrylic polymer having an average particle diameter of 150-300 nm in a step for emulsion-polymerizing a monomer in manufacturing of an acrylic rubber.

Claims

1. An acrylic emulsion comprising an acrylic polymer, the acrylic polymer comprising: a constituent unit derived from a (meth)acrylate and a constituent unit having a crosslinking group, the constituent unit derived from an unsaturated monomer, the acrylic polymer having an average particle size of 150 nm to 300 nm.

2. An acrylic rubber comprising the acrylic emulsion according to claim 1, wherein the acrylic rubber is produced using the acrylic emulsion.

3. An acrylic rubber-containing composition comprising: the acrylic rubber according to claim 2; and a crosslinking agent.

4. A crosslinked acrylic rubber product comprising the acrylic rubber-containing composition according to claim 3, wherein the crosslinked acrylic rubber product is produced using the acrylic rubber-containing composition.

5. A method for manufacturing acrylic rubber, the method comprising the steps of: coagulating the acrylic emulsion according to claim 1 with a coagulant to obtain a coagulated slurry; and drying the coagulated slurry to obtain acrylic rubber.

Description

Example 1

(Manufacture of Acrylic Emulsion A)

[0088] A polymerization reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a pressure reducer was charged with 60 parts by mass of water, 0.6 parts by mass of a polyoxyethylene alkyl ether phosphate sodium salt and 0.16 parts by mass of polyoxyethylene lauryl ether phosphate as emulsifiers, and 19.1 parts by mass of ethyl acrylate, 19.1 parts by mass of n-butyl acrylate, and 0.8 parts by mass of monobutyl fumarate as monomers, degassing by reducing pressure and substitution with nitrogen were repeated to remove oxygen sufficiently, then 0.054 parts by mass of sodium hydrogen sulfite, 0.0001 parts by mass of ferrous sulfate, and 0.03 parts by mass of ammonium persulfate were added to initiate an emulsion polymerization reaction at normal pressure and normal temperature, and the reaction was continued until the polymerization conversion rate reached 95% to obtain an acrylic emulsion A (solid content: 40%).

Example 2

(Manufacture of Acrylic Rubber Emulsion B)

[0089] An acrylic emulsion B (solid content: 40%) was obtained in the same manner as in the manufacture of the acrylic emulsion A except that the emulsifiers used to charge the polymerization reactor were changed to 0.4 parts by mass of a polyoxyethylene alkyl ether phosphate sodium salt and 0.1 parts by mass of polyoxyethylene lauryl ether phosphate. The acrylic emulsion B had a viscosity of 13.0 mPa.Math.s.

Example 3

(Manufacture of Acrylic Rubber Emulsion C)

[0090] An acrylic emulsion C (solid content: 40%) was obtained in the same manner as in the manufacture of the acrylic emulsion B except that the emulsifiers used to charge the polymerization reactor were changed to 0.2 parts by mass of a polyoxyethylene alkyl ether phosphate sodium salt and 0.05 parts by mass of polyoxyethylene lauryl ether phosphate. The acrylic emulsion C had a viscosity of 8.0 mPa.Math.s.

Example 4

(Manufacture of Acrylic Rubber Emulsion D)

[0091] An acrylic emulsion D (solid content: 40%) was obtained in the same manner as in the manufacture of the acrylic emulsion C except that the monomers used to charge the polymerization reactor were changed to 19.1 parts by mass of ethyl acrylate, 19.1 parts by mass of n-butyl acrylate, and 0.8 parts by mass of vinyl monochloroacetate, the emulsifiers were changed to 0.4 parts by mass of a polyoxyethylene alkyl ether phosphate sodium salt and 0.05 parts by mass of polyoxyethylene lauryl ether phosphate, and the polymerization auxiliary material was changed to 0.02 parts by mass of sodium formaldehyde sulfoxylate.

Example 5

(Manufacture of Acrylic Rubber Emulsion E)

[0092] An acrylic emulsion E (solid content: 30%) was obtained in the same manner as in the manufacture of the acrylic emulsion D except that the monomers used to charge the polymerization reactor were changed to 14.6 parts by mass of ethyl acrylate, 7.3 parts by mass of butyl acrylate, 7.3 parts by mass of methoxyethyl acrylate, and 0.8 parts by mass of vinyl monochloroacetate, and the emulsifiers were changed to 0.13 parts by mass of sodium lauryl sulfate and 0.16 parts by mass of a polyoxyethylene alkyl ether.

Comparative Example 1

(Manufacture of Acrylic Rubber Emulsion F)

[0093] An acrylic emulsion F (solid content: 30%) was obtained in the same manner as in the manufacture of the acrylic emulsion E except that the amount of water used to charge the polymerization reactor was changed to 70 parts by mass, the monomers were changed to 14.7 parts by mass of ethyl acrylate, 14.7 parts by mass of n-butyl acrylate, and 0.6 parts by mass of monobutyl fumarate, the emulsifiers were changed to 0.16 parts by mass of sodium lauryl sulfate and 0.4 parts by mass of a polyoxyethylene alkyl ether, and the polymerization auxiliary material was changed to 0.015 parts by mass of sodium hydrogen sulfite. The acrylic emulsion F had a viscosity of 5.0 mPa.Math.s.

Comparative Example 2

(Manufacture of Acrylic Rubber Emulsion G)

[0094] An acrylic emulsion G (solid content: 40%) was obtained in the same manner as in the manufacture of the acrylic emulsion E except that the emulsifiers used to charge the polymerization reactor were changed to 0.2 parts by mass of a polyoxyethylene alkyl ether phosphate sodium salt and 0.023 parts by mass of polyoxyethylene lauryl ether phosphate. The acrylic emulsion G had a viscosity of 6.0 mPa.Math.s.

(Method of Measuring Average Particle Size of Acrylic Polymer in Acrylic Emulsion)

[0095] The acrylic emulsion was diluted 40 times with ion-exchanged water, and measured with a dynamic light scattering method using a particle size measuring device (Zetasizer Nano S manufactured by Malvern Panalytical Ltd.). Table 1 shows the results.

(Method of Measuring Viscosity of Acrylic Emulsion)

[0096] The viscosity of the acrylic emulsion was measured in accordance with JIS K 7117-1 under an environment at 23° C. with a rotational viscometer (Brookfield manufactured by EKO Instruments) using an LV-1 spindle at a rotation speed of 30 rpm.

(Stability of Acrylic Emulsion)

[0097] The stability of the acrylic emulsion was evaluated in accordance with the following criteria. Table 1 shows the results. [0098] o: When the acrylic emulsion after completion of polymerization is left to stand for 2 hours and then filtered with an 80 mesh-size wire mesh, the amount of the aggregate is less than 1 mass % with respect to the entire acrylic emulsion. [0099] x: When the acrylic emulsion after completion of polymerization is left to stand for 2 hours and then filtered with an 80 mesh-size wire mesh, the amount of the aggregate is 1 mass % or more with respect to the entire acrylic emulsion.

(Coagulability of Acrylic Emulsion)

[0100] The coagulability of the acrylic emulsion was evaluated in accordance with the following criteria. Table 1 shows the results. [0101] o: When a mixture obtained by adding 6 parts of sodium sulfate to 100 parts by mass of water is heated to 85° C., and 100 parts of the acrylic emulsion is added dropwise and coagulated, the obtained yield of the polymer is 95 mass % or more (based on the polymer content, obtained as a residue after drying the acrylic emulsion at 110° C., set to 100 mass %). [0102] x: When a mixture obtained by adding 6 parts of sodium sulfate to 100 parts by mass of water is heated to 85° C., and 100 parts of the acrylic emulsion is added dropwise and coagulated, the obtained yield of the polymer is less than 95 mass % (based on the polymer content, obtained as a residue after drying the acrylic emulsion at 110° C., set to 100 mass %).

TABLE-US-00001 TABLE 1 Comparative Comparative Example 1 Example 2 Example 3 Example 4 Example 5 Example 1 Example 2 Acrylic emulsion A B C D E F G Emulsion size 222.0 231.3 263.6 299.4 157.6 142.6 332.5 [nm] Coagulability of ∘ ∘ ∘ ∘ ∘ x ∘ emulsion Stability of ∘ ∘ ∘ ∘ ∘ ∘ x emulsion

[0103] From Table 1, the acrylic emulsions in Examples obtained with the method for manufacturing of the present invention are excellent in coagulability and emulsion stability. The acrylic emulsion in Comparative Example 1 was equivalent in emulsion stability, but inferior in coagulability to the acrylic emulsions in Examples. The acrylic emulsion in Comparative Example 2 was equivalent in coagulability, but inferior in emulsion stability to the acrylic emulsions in Examples. As a result, it has been shown that the acrylic emulsions in Examples were superior in coagulability and emulsion stability to the acrylic emulsions in Comparative Examples.

INDUSTRIAL APPLICABILITY

[0104] The acrylic emulsion of the present invention has excellent coagulability in manufacturing acrylic rubber and has excellent stability, and thus is excellent in stability during liquid feeding in the manufacturing process, so that the acrylic emulsion is useful. The acrylic rubber manufactured using the acrylic emulsion of the present invention can be widely used as a material of rubber products utilizing its excellent heat resistance, weather resistance, ozone resistance, and abrasion resistance. In particular, the crosslinked product produced using the acrylic rubber of the present invention is extremely effective as fuel hoses, air hoses, tube materials, and the like for automobiles.