Acrylic Emulsion Pressure-Sensitive Adhesive Composition

Abstract

An acrylic emulsion pressure-sensitive adhesive composition is provided. More particularly, an acrylic emulsion pressure-sensitive adhesive composition that may become easily removable when being impregnated with water in a water-borne removal process while being able to realize excellent tacky/adhesive strength for a substrate to be adhered is provided.

Claims

1. An acrylic emulsion pressure-sensitive adhesive composition comprising emulsion polymer particles (A) including: a1) a first repeating unit derived from an alkyl (meth)acrylate-based monomer, a2) a second repeating unit derived from an unsaturated carboxylic acid-based monomer, a3) a third repeating unit derived from vinyl acetate, and a4) a fourth repeating unit represented by the following Chemical Formula 1: ##STR00004##

2. The acrylic emulsion pressure-sensitive adhesive composition of claim 1, wherein the alkyl (meth)acrylate-based monomer includes one or more selected from the group consisting of methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, dodecyl (meth)acrylate, isobornyl (meth)acrylate, and lauryl (meth)acrylate.

3. The acrylic emulsion pressure-sensitive adhesive composition of claim 1, wherein the unsaturated carboxylic acid-based monomer includes one or more selected from the group consisting of acrylic acid, methacrylic acid, fumaric acid, maleic acid, itaconic acid, citraconic acid, mesaconic acid, glutaconic acid, and allylmalonic acid.

4. The acrylic emulsion pressure-sensitive adhesive composition of claim 1, wherein the acrylic emulsion pressure-sensitive adhesive composition includes 0.1 parts by weight to 10 parts by weight of the second repeating unit with respect to 100 parts by weight of the first repeating unit.

5. The acrylic emulsion pressure-sensitive adhesive composition of claim 1, wherein the acrylic emulsion pressure-sensitive adhesive composition includes 1 part by weight to 30 parts by weight of the third repeating unit with respect to 100 parts by weight of the first repeating unit.

6. The acrylic emulsion pressure-sensitive adhesive composition of claim 1, wherein the acrylic emulsion pressure-sensitive adhesive composition includes 0.1 parts by weight to 5 parts by weight of the fourth repeating unit with respect to 100 parts by weight of the first repeating unit.

7. The acrylic emulsion pressure-sensitive adhesive composition of claim 1, wherein the emulsion polymer particles (A) further include a fifth repeating unit derived from any one or more monomers of a hydroxy alkyl (meth)acrylate-based monomer and an aromatic vinylic monomer.

8. The acrylic emulsion pressure-sensitive adhesive composition of claim 7, wherein the hydroxy alkyl (meth)acrylate-based monomer includes one or more selected from the group consisting of hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and hydroxybutyl (meth)acrylate.

9. The acrylic emulsion pressure-sensitive adhesive composition of claim 7, wherein the aromatic vinylic monomer includes one or more selected from the group consisting of styrene, methylstyrene, ethylstyrene, butylstyrene, chlorostyrene, methyl vinyl benzoate, vinylnaphthalene, chloromethylstyrene, and divinylbenzene.

10. The acrylic emulsion pressure-sensitive adhesive composition of claim 1, wherein the acrylic emulsion pressure-sensitive adhesive composition includes 4000 ppm or more of acetic acid with respect to a weight of the emulsion polymer particles (A).

11. An adhesive member comprising: a substrate; and an adhesive layer which is formed on at least one surface of the substrate, wherein the adhesive layer includes the acrylic emulsion pressure-sensitive adhesive composition of claim 1.

12. The adhesive member of claim 11, wherein the adhesive member has a 90 degree peel strength of 500 gf/in or more with respect to SUS surface, as measured according to FINAT Test Method No.2 (FTM 2) standard, and has a 90 degree peel strength of less than 250 gf/in with respect to the SUS surface, as measured according to the FINAT Test Method No.2 (FTM 2) standard, after being impregnated with water.

13. The adhesive member of claim 11, wherein the adhesive member has a 90 degree peel strength of 250 gf/in or more with respect to HDPE surface, as measured according to FINAT Test Method No.2 (FTM 2) standard, and has a 90 degree peel strength of less than 130 gf/in with respect to the HDPE surface, as measured according to the FINAT Test Method No.2 (FTM 2) standard, after being impregnated with water.

14. A method of preparing an acrylic emulsion pressure-sensitive adhesive composition, comprising: forming emulsion polymer particles (A) by performing emulsion polymerization of a monomer mixture including an alkyl (meth)acrylate-based monomer, an unsaturated carboxylic acid-based monomer, and a vinyl acetate in the presence of an emulsifier; and hydrolyzing vinyl acetate-derived residues by leaving the emulsion polymer particles under acidic or basic conditions.

15. The acrylic emulsion pressure-sensitive adhesive composition of claim 1, wherein the acrylic emulsion pressure-sensitive adhesive composition includes 4000 ppm to 18000 ppm of acetic acid with respect to a weight of the emulsion polymer particles (A).

16. The adhesive member of claim 11, wherein the adhesive member has a 90 degree peel strength of 500 gf/in to 100 gf/in with respect to SUS surface, as measured according to FINAT Test Method No.2 (FTM 2) standard, and has a 90 degree peel strength of 100 gf/in to 250 gf/in with respect to the SUS surface, as measured according to the FINAT Test Method No.2 (FTM 2) standard, after being impregnated with water.

17. The adhesive member of claim 11, wherein the adhesive member has a 90 degree peel strength of 250 gf/in to 500 gf/in with respect to HDPE surface, as measured according to FINAT Test Method No.2 (FTM 2) standard, and has a 90 degree peel strength of 50 gf/in to130 gf/in with respect to the HDPE surface, as measured according to the FINAT Test Method No.2 (FTM 2) standard, after being impregnated with water.

Description

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0102] Hereinafter, the actions and effects of the present invention will be described in more detail with reference to the specific exemplary embodiments of the present invention. However, these exemplary embodiments are for illustrative purposes only, and the scope of the present invention is not intended to be limited thereby.

EXAMPLE

Emulsion Polymerization

[0103] 300 g of water and 10 g of a sodium alkyldiphenyloxide disulfonate solution at a concentration of 45% by weight were added to a 3 L glass reactor equipped with a thermostat, a stirrer, a dropping funnel, a nitrogen gas injection tube, and a reflux condenser, followed by stirring. The inside of the reactor was replaced with nitrogen, and then the temperature was raised to 80° C. under nitrogen atmosphere and maintained for 30 minutes.

[0104] Separately, monomers according to each composition of the following Table 1 were added to a 2 L beaker, and stirred for 30 minutes to prepare a monomer mixture (total weight of the monomers: about 600 g).

[0105] A solution consisting of 30 g of sodium polyoxyethylene lauryl ethersulfate at a concentration of 26% by weight, 5 g of a sodium alkyldiphenyl oxide disulfonate solution at a concentration of 45% by weight, 3 g of sodium carbonate, and 200 g of water was added thereto, and stirred to prepare a milky pre-emulsion.

[0106] 3 g of potassium persulfate at a concentration of 20% by weight was added to the glass reactor containing the emulsion, and dissolved by stirring for 10 minutes.

[0107] The pre-emulsion and 100 g of potassium persulfate at a concentration of 2% by weight were continuously added to the glass reactor evenly for 4 hours, and polymerization was performed at 80° C. After the addition was completed, the mixture was stirred at the same temperature for 30 minutes.

[0108] This mixture was cooled to room temperature to prepare an acrylic emulsion pressure-sensitive adhesive composition.

Hydrolysis Process

[0109] 100 g of the emulsion pressure-sensitive adhesive composition prepared above was put in a glass beaker at room temperature, and a 10% aqueous sodium hydroxide solution was added until the pH value of the composition became about 6.0 or higher, followed by stirring at 300 rpm for 1 hour.

[0110] After the stirring was completed, the content of acetic acid in the composition was examined by the following method, and when the content was less than 4000 ppm, 10% aqueous sodium hydroxide solution was added again under stirring until the pH value of the composition increased to about 1.0, and the mixture was stirred in the same manner until the content of acetic acid reached 4000 ppm or more. Then, the content thereof was examined, and the results are summarized in Table 1 below.

Examination of Content of Acetic Acid

[0111] About 1.0 g of the pressure-sensitive adhesive composition was taken and put in a beaker, and 4 mL of acetone was added thereto. It was examined whether precipitation occurred. The mixture was centrifuged, and the supernatant was used as a sample solution for examining the content of acetic acid.

[0112] GC/FID was used in analyzing the content of acetic acid, and specific conditions are as follows.

[0113] Column: DB-WAXetr (50 m L×0.32 mm ID, 1.0 um d.f., capillary);

[0114] Temperature : Injector (200° C.), Detector (250° C.);

[0115] Injection volume: about 1.0 uL

TABLE-US-00001 TABLE 1 Unit: Acetic parts by acid weight 2-EHA BA SM Vac MMA HEA AA MAA (ppm) Example 1 90 1 5 2 2 6000 Example 2 80 7 12 1 6800 Example 3 70 12 16.5 1 0.5 9700 Example 4 75 18 5 1 1 12300 Reference 79 1 3.5 15 1 0.5 3300 Example 1 Reference 70 29 1 27100 Example 2 Reference 78 7 12 1 1 1 19500 Example 3 Reference 77 10 12.5 0.5 3900 Example 4 *2-EHA: 2-ethylhexyl acrylate; BA: butyl acrylate; SM: styrene; Vac: vinyl acetate, MMA: methyl methacrylate; HEA: hydroxyethyl acrylate; AA: acrylic acid; MAA: methacrylic acid

Preparation of Adhesive Member

[0116] The acrylic emulsion pressure-sensitive adhesive composition prepared above was coated onto a release paper at a thickness of 18 μm, and dried at 120° C. for 1 minute, and then laminated on a PP film to prepare an adhesive member.

Measurement of Adhesive Properties

Measurement of 90 Degree Peel Strength

[0117] For the film label specimens prepared above, a 90 degree peel strength was measured in accordance with the FINAT Test Method FTM 2.

[0118] A specimen with a size of 1 inch×4 inch was prepared, and attached to the stainless steel surface (SUS304) and HDPE surface, and then pressed by reciprocating with a 2 kg roller at a speed of 300 mm/min twice. After aging at room temperature for 20 minutes, a peel strength was measured while peeling using a TA texture analyzer at a speed of 300 mm/min for 5 seconds.

Water Impregnation and Measurement Method of Adhesive Properties

[0119] Each film label specimen prepared above was attached to the stainless steel surface (SUS) and HDPE surface, and then placed in a glass container containing water so that the attached specimen was immersed in 100%. Then, each specimen was put in a 60° C. oven for 24 hours and then taken out, and the attached specimen was dried for 2 minutes using a nitrogen gun. While peeling each specimen in the same manner as above, a 90 degree peel strength value was measured.

[0120] The measurement results are summarized in Table 2 below.

TABLE-US-00002 TABLE 2 90 degree 90 degree 90 degree 90 degree peel peel peel peel strength after strength after strength strength impregnation impregnation (gf/in), SUS (gf/in), HDPE (gf/in), SUS (gf/in), HDPE Example 1 590 290 230 110 Example 2 640 340 180 100 Example 3 710 300 160 80 Example 4 510 260 130 70 Reference 520 270 250 130 Example 1 Reference 310 120 100 30 Example 2 Reference 480 170 150 50 Example 3 Reference 600 320 290 150 Example 4

[0121] Referring to Tables 1 and 2, it was confirmed that the acrylic emulsion pressure-sensitive adhesive compositions according to Examples and Reference Examples of the present invention or the adhesive members prepared by using the same had excellent peel strength values with respect to various substrates having completely different surface properties, such as SUS, HDPE, etc., while showing a remarkable reduction in the peel strength values after being immersed in water.

[0122] As in Table 2, it was clearly confirmed that Examples 1 to 4 had a 90 degree peel strength value of about 510 gf/in to about 710 gf/in with respect to SUS to exhibit very excellent adhesive strength, before being immersed in water, whereas Examples 1 to 4 had a 90 degree peel strength value of about 130 gf/in to about 230 gf/in with respect to SUS to exhibit about 20% to 40% reduction in the adhesive strength, after being immersed in water.

[0123] Further, as in Table 2, it was clearly confirmed that Examples 1 to 4 had a 90 degree peel strength value of about 260 gf/in to about 340 gf/in with respect to HDPE to exhibit very excellent adhesive strength, before being immersed in water, whereas Examples 1 to 4 had a 90 degree peel strength value of about 70 gf/in to about 110 gf/in with respect to HDPE to exhibit about 20% to 40% reduction in the adhesive strength, after being immersed in water.

[0124] Accordingly, it is believed that the acrylic emulsion pressure-sensitive adhesive composition of the present invention or the adhesive member prepared by using the same may be easily peeled off when being impregnated with water during a water-borne removal process, while being able to realize excellent tacky/adhesive properties with respect to a substrate to be adhered.