Polymer emulsion having heat sealability for blister package and preparation method thereof

Abstract

The present invention provides a polymer emulsion having heat sealability for a blister package, and a method for preparing the same. Since the polymer emulsion of the present invention includes latex particles having an average particle diameter of a nanosize and a low unimodal particle size distribution, it may exhibit uniform and stable emulsion properties, particularly excellent heat sealability, and thus may be suitably used for a blister package and on the like. Furthermore, the polymer emulsion of the present invention is polymerized in an aqueous medium without using an organic solvent, and thus enables provision of a blister package with minimized harmfulness to a human body and the environment.

Claims

1. A polymer emulsion having heat sealability for a blister package, comprising latex particles, wherein a water soluble polymer emulsifier having a weight average molecular weight of 6,000 to 23,000 g/mol, a glass transition temperature of 100 to 150 C., and an acid value of 100 to 230 mg KOH/g covers a polymer derived from ethylenically unsaturated monomers, wherein the water soluble polymer emulsifier is a polymer derived from a monomer mixture comprising 80 to 90 parts by weight of alpha-methylstyrene and 80 to 90 parts by weight of acrylic acid, based on 100 parts by weight of styrene.

2. The polymer emulsion having heat sealability for a blister package according to claim 1, wherein the ethylenically unsaturated monomer is a compound represented by the following chemical formula B: ##STR00005## in the chemical formula B, R.sup.b is hydrogen or a methyl group, L.sup.b is a phenyl group or a C(O)OR.sup.n group, and R.sup.n is hydrogen or a C1-10 linear or branched alkyl group.

3. The polymer emulsion having heat sealability for a blister package according to claim 1, wherein the polymer derived from ethylenically unsaturated monomers is a polymer derived from a monomer mixture comprising styrene monomers represented by the following chemical formula B-1, and one or more kinds of acrylic monomers selected from the group consisting of the compounds represented by the following chemical formula B-2 and chemical formula B-3 at a weight ratio of 1:1.5 to 1:10: ##STR00006## in chemical formulae B-1 to B-3, R.sup.5 to R.sup.7 are each independently hydrogen or a methyl group, and R.sup.8 is a C1-10 linear or branched alkyl group.

4. The polymer emulsion having heat sealability for a blister package according to claim 3, wherein the acrylic monomer is a compound having a glass transition temperature (T.sub.g) of 70 to 30 C.

5. The polymer emulsion having heat sealability for a blister package according to claim 1, wherein the polymer derived from ethylenically unsaturated monomers is a polymer derived from a monomer mixture comprising 150 to 900 parts by weight of butyl acrylate, based on 100 parts by weight of styrene.

6. The polymer emulsion having heat sealability for a blister package according to claim 1, wherein the latex particle comprises the water soluble polymer emulsifier in an amount of 10 to 20 wt %, based on the polymer derived from ethylenically unsaturated monomers.

7. The polymer emulsion having heat sealability for a blister package according to claim 1, wherein the latex particles have an average particle diameter of 45 to 65 nm.

8. The polymer emulsion having heat sealability for a blister package according to claim 1, wherein the latex particles have a unimodal particle size distribution.

9. The polymer emulsion having heat sealability for a blister package according to claim 1, wherein the polymer emulsion has a glass transition temperature (T.sub.g) or 10 C. or less.

10. The polymer emulsion having heat sealability for a blister package according to claim 1, wherein the polymer emulsion has a solid content of 40 to 60 wt %.

11. The polymer emulsion having heat sealability for a blister package according to claim 1, wherein the polymer emulsion has an acid value of 50 to 100 mg KOH/g.

12. A method for preparing the polymer emulsion having heat sealability for a blister package according to claim 1, comprising the step of emulsion polymerizing ethylenically unsaturated monomers in an aqueous medium in which a water soluble polymer emulsifier having a weight average molecular weight of 6,000 to 23,000 g/mol, a glass transition temperature of 100 to 150 C., and an acid value of 100 to 230 mg KOH/g exists, wherein the water soluble polymer emulsifier is a polymer derived from a monomer mixture comprising 80 to 90 parts by weight of alpha-methylstyrene and 80 to 90 parts by weight of acrylic acid, based on 100 parts by weight of styrene.

13. The method according to claim 12, wherein the emulsion polymerization is conducted at a reaction temperature of 70 to 100 C.

14. A blister package comprising a heat sealable coating layer formed from the polymer emulsion of claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a graph showing the particle size distribution of the polymer emulsion according to Example 1 of the present invention.

(2) FIG. 2 is a graph showing the particle size distribution of the polymer emulsion according to Comparative Example 1.

(3) FIG. 3 is a graph showing the particle size distribution of the polymer emulsion according to Comparative Example 2.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(4) Hereinafter, preferable examples are presented for the complete understanding of the preset invention. However, these examples are intended only to illustrate the present invention, and the present invention is not limited thereto.

Example 1

(5) A water soluble polymer emulsifier (product name S-70; manufactured by Hanwha Chemical; weight average molecular weight of 7,000 g/mol; glass transition temperature (Tg) of 120 C.; acid value of 218 mg KOH/g; bulk polymer derived from about 84.2 parts by weight of alpha-methylstyrene and about 87.5 parts by weight of acrylic acid, based on 100 parts by weight of styrene) was prepared.

(6) Into a 5 L reactor, 122 g of the water soluble polymer emulsifier (about 35 wt %, based on the following monomer mixture) was dissolved in 30 ml of an ammonia aqueous solution, and then, while raising the temperature to 86 C., ammonium persulfate (APS) was dividedly introduced as an initiator. A monomer mixture including styrene and butyl acrylate at a weight ratio of 1:2.6 was semi-continuously introduced into the reactor, thus obtaining a polymer emulsion including latex particles by emulsion polymerization.

Example 2

(7) A water soluble polymer emulsifier (product name S-120; manufactured by Hanwha Chemical; weight average molecular weight of 12,500 g/mol; glass transition temperature (Tg) of 130 C.; acid value of 218 mg KOH/g; bulk polymer derived from about 84.2 parts by weight of alpha-methylstyrene and about 87.5 parts by weight of acrylic acid, based on 100 parts by weight of styrene) was prepared.

(8) Into a 5 L reactor, 122 g of the water soluble polymer emulsifier (about 35 wt %, based on the following monomer mixture) was dissolved in 30 ml of an ammonia aqueous solution, and then, while raising the temperature to 86 C., ammonium persulfate (APS) was dividedly introduced as an initiator. A monomer mixture including styrene and butyl acrylate at a weight ratio of 1:2.6 was semi-continuously introduced into the reactor, thus obtaining a polymer emulsion including latex particles by emulsion polymerization.

Example 3

(9) A polymer emulsion was obtained by the same method as Example 2, except that a monomer mixture including styrene and butyl acrylate at a weight ratio of 1:3.5 was semi-continuously introduced into a reactor in which a water soluble polymer emulsifier and an initiator existed, thus progressing emulsion polymerization.

Example 4

(10) A polymer emulsion was obtained by the same method as Example 2, except that a monomer mixture including styrene and butyl acrylate at a weight ratio of 1:5 was semi-continuously introduced into a reactor in which a water soluble polymer emulsifier and an initiator existed, thus progressing emulsion polymerization.

Example 5

(11) A polymer emulsion was obtained by the same method as Example 2, except that a monomer mixture including styrene and butyl acrylate at a weight ratio of 1:7 was semi-continuously introduced into a reactor in which a water soluble polymer emulsifier and an initiator existed, thus progressing emulsion polymerization.

Example 6

(12) A polymer emulsion was obtained by the same method as Example 2, except that a monomer mixture including styrene and butyl acrylate at a weight ratio of 1:9 was semi-continuously introduced into a reactor in which a water soluble polymer emulsifier and an initiator existed, thus progressing emulsion polymerization.

Comparative Example 1

(13) A polymer emulsion was obtained by the same method as Example 1, except that a water soluble polymer emulsifier (product name S-60L; manufactured by Hanwha Chemical; weight average molecular weight of 8,000 g/mol; glass transition temperature (Tg) of 38 C.; acid value of 80 mg KOH/g; bulk polymer derived from 5.8 wt % of acrylic acid, 33.7 wt % of ethyl acrylate, 6 wt % of methacrylic acid, and 54.5 wt % of methyl methacrylate) was used.

Comparative Example 2

(14) A polymer emulsion was obtained by the same method as Example 1, except that a water soluble polymer emulsifier (product name S-150L; manufactured by Hanwha Chemical; weight average molecular weight of 15,000 g/mol; glass transition temperature (Tg) of 60 C.; acid value of 80 mg KOH/g; bulk polymer derived from 5.8 wt % of acrylic acid, 33.7 wt % of ethyl acrylate, 6 wt % of methacrylic acid, and 54.5 wt % of methyl methacrylate) was used.

Comparative Example 3

(15) A polymer emulsion was obtained by the same method as Example 1, except that a water soluble polymer emulsifier (product name S-160L; manufactured by Hanwha Chemical; weight average molecular weight of 16,000 g/mol; glass transition temperature (Tg) of 78 C.; acid value of 230 mg KOH/g; bulk polymer derived from 37 wt % of acrylic acid, 7.5 wt % of butyl acrylate, and 55.5 wt % of styrene and alpha-methylstyrene) was used.

Experimental Example

(16) For the polymer emulsions obtained through examples and comparative examples, the following experiments were conducted, and the results are shown in the following Tables 1 and 2 and FIGS. 1 to 3.

(17) (1) Glass transition temperature (Tg): A glass transition temperature was measured by differential scanning calorimetry (DSC), and at the time of measurement, a temperature range was 50 to 200 C. and a temperature rising speed was 10 C./min.

(18) (2) Acid value: The acid value of resin was measured by dissolving about 1.0 g of each polymer emulsion in about 50 g of tetrahydrofuran (THF), then adding 5 to 6 ml of a phenolphthalein solution (concentration 1%), and titrating with a potassium hydroxide standard solution (KOH 0.1 N).

(19) (3) The average particle diameter, solid content, and particle size distribution of latex particles included in the polymer emulsion were measured using a particle size analyzer (model name: NANOTRAC)

(20) (4) Peel strength: Each polymer emulsion was coated on an Al foil to a thickness of about 6.8 m, dried in an oven at 100 C. for 1 minute, and then dried at room temperature for 30 minutes or more. The dried coated Al foil was heat laminated with a PVC film using a heat laminator to manufacture a specimen. The peel strength between the Al foil and the PVC film was measured using a universal tension testing machine, wherein the peel strength was measured 5 times and the average value is shown in the following Table 1. Here, it can be seen that heat sealability is better as the peel strength is larger.

(21) TABLE-US-00001 TABLE 1 Average Acid Solid particle Vis- value Peel Exam- T.sub.g content diameter cosity (mg strength ple ( C.) (wt %) (nm) (cps) pH KOH/g) (kgf/cm.sup.2) 1 0 44.6 54 112 8.32 71.8 0.536 2 2 44.55 52 185 8.28 71 0.322 3 5.7 44.6 51.2 272 8.39 72 0.686 4 10.9 44.3 47.7 291 8.44 68 0.6 5 14.8 44.6 52.9 252 8.23 69 0.419 6 17.1 44.07 52.9 300 8.32 74 0.427

(22) TABLE-US-00002 TABLE 2 Com- Average Acid Peel parative Solid particle Vis- value strength Exam- T.sub.g content diameter cosity (mg (kgf/ ple ( C.) (wt %) (nm) (cps) pH KOH/g) cm.sup.2) 1 13 44.4 bimodal 23,2300 9.3 51 0.483 2 8 43.2 bimodal 1 3 4 44.2 bimodal 13,680 8.07 60 0.531

(23) Referring to the tables and drawings, it was confirmed that the polymer emulsions according to the examples include latex particles having a unimodal particle size distribution, as shown in FIG. 1 (Example 1). It was also confirmed that the polymer emulsion of the examples have good properties on the whole, and exhibit appropriate viscosities and excellent peel strengths, and thus are suitable for heat seal coating of a blister package.

(24) To the contrary, as shown in FIG. 2 (Comparative Example 1) and FIG. 3 (Comparative Example 2), the latex particles included in the polymer emulsions of the comparative examples exhibited bimodal particle size distributions. Further, although the polymer emulsions according to the comparative examples exhibited peel strengths equivalent to those of the examples, due to their excessively high viscosities, it was not easy to handle and use them, and particularly, in the case of Comparative Example 2, a gel state was formed, and thus it was impossible to measure the properties.