VINYL ACETATE-ETHYLENE COPOLYMER EMULSION AND METHOD FOR THE PRODUCTION THEREOF

Abstract

A vinyl acetate-ethylene copolymer emulsion and method of making the same. The vinyl acetate-ethylene copolymer emulsion is prepared by using a redox initiator. Where the redox initiator includes a salt of at least one metal selected from the group consisting of silver (Ag), platinum (Pt), copper (Cu), mercury (Hg), zinc (Zn), tin (Sn), lead (Pb), bismuth (Bi), cadmium (Cd) and chromium (Cr). The emulsion further includes an oligomer of a monocarboxylic acid selected from the group consisting of C.sub.1-C.sub.14 aliphatic monocarboxylic acid and C.sub.6-C.sub.14 aromatic monocarboxylic acid.

Claims

1-18. (canceled)

19. A copolymer, comprising: a vinyl acetate-ethylene copolymer emulsion prepared by using a redox initiator; wherein the redox initiator comprises a salt of at least one metal selected from the group consisting of silver (Ag), platinum (Pt), copper (Cu), mercury (Hg), zinc (Zn), tin (Sn), lead (Pb), bismuth (Bi), cadmium (Cd), and chromium (Cr); and wherein the vinyl acetate-ethylene copolymer emulsion further comprises an oligomer of a monocarboxylic acid selected from the group consisting of C.sub.1-C.sub.14 aliphatic monocarboxylic acid and C.sub.6-C.sub.14 aromatic monocarboxylic acid.

20. The copolymer of claim 19, wherein the metal salt is oxidized to form a metal oxide during the polymerization of the vinyl acetate-ethylene copolymer.

21. The copolymer of claim 19, wherein the redox initiator comprises a salt of at least one metal selected from the group consisting of silver (Ag), copper (Cu), zinc (Zn), and tin (Sn).

22. The copolymer of claim 19, wherein the metal salt includes an anion selected from the group consisting of a carboxylate anion (COO), a sulfoxylate anion (SO.sub.2.sup.2−), and SO.sub.2.sup.−—HCOH—(COO).

23. The copolymer of claim 19, wherein said copolymer further comprises: (a) vinyl acetate-ethylene copolymer; (b) water; and (c) a metal oxide, which is formed by oxidization of the metal salt during the polymerization of the vinyl acetate-ethylene copolymer.

24. The copolymer of claim 19, wherein the metal oxide is contained at a content of 100 to 300 ppm, based on the total weight of the corresponding vinyl acetate-ethylene copolymer emulsion.

25. The copolymer of claim 24, wherein the monocarboxylic acid is selected from the group consisting of formic acid, acetic acid, propionic acid, lactic acid, sorbic acid, n-octanoic acid, undec-10-enoic acid, dehydroacetic acid, benzoic acid, salicylic acid, alkyl 4-hydroxybenzoates, naphthenic acid, and n-dodecanoic acid.

26. A method for preparing a vinyl acetate-ethylene copolymer emulsion, the method comprising: polymerizing vinyl acetate and ethylene in presence of a redox initiator in a protective colloid-containing aqueous reaction solution, wherein the redox initiator comprises a salt of at least one metal selected from the group consisting of silver (Ag), platinum (Pt), copper (Cu), mercury (Hg), zinc (Zn), tin (Sn), lead (Pb), bismuth (Bi), cadmium (Cd), and chromium (Cr), and wherein the aqueous reaction solution further includes a monocarboxylic acid selected from the group consisting of C.sub.1-C.sub.14 aliphatic monocarboxylic acid and C.sub.6-C.sub.14 aromatic monocarboxylic acid.

27. The method of claim 26, wherein the metal salt in oxidized to form a metal oxide during the formation of the vinyl acetate-ethylene copolymer in the polymerization.

28. The method of claim 26, wherein a content of the metal salt ranges from 0.05 to 0.02 parts by weight, based on 100 parts by weight of a sum of vinyl acetate and ethylene.

29. The method of claim 26, wherein the aqueous reaction solution further comprises a co-emulsifier.

30. The method of claim 29, wherein the co-emulsifier comprises PEG-n cocomonium chloride (n=2-15).

31. The method of claim 29, wherein the co-emulsifier is contained in an amount of 0.01 to 0.1 parts by weight, based on 100 parts by weight of a sum of vinyl acetate and ethylene.

32. The method of claim 31, wherein the monocarboxylic acid is contained in an amount of 0.15 to 0.4 parts by weight, based on 100 parts by weight of a sum of vinyl acetate and ethylene.

33. The method of claim 26, further comprising a step of adding a second redox initiator identical to or different from the redox initiator to the vinyl acetate-ethylene copolymer-containing emulsion formed in the polymerization step, after completion of the polymerization.

34. The method of claim 33, wherein the second redox initiator comprises a salt of at least one metal selected from the group consisting of silver (Ag), platinum (Pt), copper (Cu), mercury (Hg), zinc (Zn), tin (Sn), lead (Pb), bismuth (Bi), cadmium (Cd), and chromium (Cr).

Description

Comparative Example 1: Preparation of Vinyl Acetate-Ethylene Copolymer Emulsion

[0094] To a 1.sup.st vessel was fed 5520 g of process water, followed by 178 g of PVOH (25/88, degree of polymerization/degree of saponification) and 81 g of PVOH (05/88). Stirring the reactants for 20 min afforded a 1.sup.st aqueous reaction solution (pH 4). In a 2.sup.nd vessel, 0.21 g of ferrous ammonium sulfate and 0.21 g of citric acid were added to 3.42 g of process water and completely dissolved to obtain a 2.sup.nd aqueous reaction solution. Then, the 2.sup.nd aqueous reaction solution was added to the 1.sup.st aqueous reaction solution and stirred for 10 min. The resulting aqueous reaction solution was fed to a pressurized reactor (maximum internal pressure: 80 bar).

[0095] Subsequently, the inside of the pressurized reactor was sufficiently purged with nitrogen and 3021 g of vinyl acetate was fed into the pressurized reactor, followed by 882 g of ethylene gas. The reactants were stirred for about 20 min.

[0096] Then, the temperature of the pressurized reactor was elevated to and stabilized at about 55° C. before feeding a redox initiator to the pressurized reactor. In this regard, an oxidizing agent-containing solution and a reducing agent-containing solution were fed at rates of about 120 g/hour and about 240 g/hour, respectively. The feeding of the oxidizing agent-containing solution and the reducing agent-containing solution was continued for 90 min from the time point when the internal temperature of the reactor increased by about 1° C., which was regarded as the initiation of the polymerization reaction. Here, the oxidizing agent-containing solution and the reducing agent-containing solution in the redox initiator were a solution of 8.16 g of tert-butyl hydroperoxide in 211.32 g of process water and a solution of 8.06 g of sodium formaldehyde sulfoxylate (Bruggolite© FF6, Brueggemann Chemical US) in 100.3 g of process water, respectively.

[0097] From 3 min. after initiation of the polymerization reaction, vinyl acetate was additionally fed at a rate of about 6.2 g/min for about 90 min.

[0098] After completion of the polymerization reaction, a 2.sup.nd redox initiator was fed for 15 min to the pressurized reactor to remove (reduce) residual vinyl acetate monomers, thus obtaining a 1st emulsion containing a vinyl acetate-ethylene copolymer. Here, the 2.sup.nd redox initiator included a 2.sup.nd oxidizing agent-containing solution obtained by dissolving 2.47 g of tert-butyl hydroperoxide in 17.95 g of process water and a 2.sup.nd reducing agent-containing solution obtained by dissolving 1.13 g of FF6 in 17.5 g of process water.

[0099] One hour later, 50 ppm of potassium iodate (KI03) was to the 1st emulsion to obtain a 2.sup.nd emulsion to which 4.8 ppm of 2-methyl-4-isothiazolin-3-one (MIT), 10 ppm of 5-chloro-2-methyl-4-isothiazolin-3-one (CMIT), 100 ppm of 1,2-benzisothiazolin-3-one (BIT), and 100 ppm of dodecylguanidine hydrochloride (DGH) were then added to afford a 3.sup.rd emulsion containing a vinyl acetate-ethylene copolymer.

Comparative Example 2

[0100] A vinyl acetate-ethylene copolymer-containing emulsion was prepared in the same manner as in Comparative Example 1, with the exception that 50 ppm of KIO.sub.3, 4.8 ppm of MIT, 10 ppm of CMIT, 100 ppm of BIT, and 100 ppm of DGH were not added.

Comparative Example 3

[0101] A vinyl acetate-ethylene copolymer-containing emulsion was prepared in the same manner as in Comparative Example 1, with the exception that 260 ppm of ZnO was added, instead of 50 ppm of KIO.sub.3, 4.8 ppm of MIT, 10 ppm of CMIT, 100 ppm of BIT, and 100 ppm of DGH. The ZnO used was pretreated with tri-ethanol amine.

[0102] However, the vinyl acetate-ethylene copolymer-containing emulsion prepared could not be used as an emulsion because ZnO particles were gelled and coagulat-ed as shown in FIG. 7b.

Example 1

[0103] A vinyl acetate-ethylene copolymer-containing emulsion was prepared in the same manner as in Comparative Example 1, with the exception that 35.05 g of a zinc salt was used instead of 8.06 g of Bruggolite® FF6 serving as a reducing agent in the redox initiator and that none of 50 ppm of KIO.sub.3, 4.8 ppm of MIT, 10 ppm of CMIT, 100 ppm of BIT, and 100 ppm of DGH were used. The zinc salt used has a structure represented by the following Chemical Formula 1:

##STR00002##

[0104] FIG. 7a is a photographic image illustrating the vinyl acetate-ethylene copolymer-containing emulsion prepared in Example 1. In contrast to the VAE emulsion of Comparative Example 3, as shown in FIG. 7a, the VAE emulsion of Example 1 was found to have gelled or coagu-lated particles.

Example 2

[0105] A vinyl acetate-ethylene copolymer emulsion was prepared in the same manner as in Comparative Example 1, with the exception that 15 g of lactic acid and 3.67 g of the co-emulsifier coconut alkyl bis(2-hydroxyeth-yl)methyl quaternary ammonium chloride were added, together with PVOH, for preparing the 1st solution and that none of 50 ppm of KIO.sub.3, 4.8 ppm of MIT, 10 ppm of CMIT, 100 ppm of BIT, and 100 ppm of DGH were added to the 2.sup.nd emulsion.

Experimental Example 1: Assay 1 for Anti-Fungal Resistance of VAE Emulsion

[0106] The vinyl acetate-ethylene copolymer emulsion prepared in Example 1 and Comparative Examples 1 and 2 were assayed preservability (anti-fungal activity) as follows.

[0107] A fungus strain (Aspergillus brasiliensis ATCC 16404) was inoculated to each of the final vinyl ace-tate-ethylene copolymer emulsions prepared in Example 1 and Comparative Examples 1 and 2 and cultured at 25° C. for 72 hours. Thereafter, observation was made to see whether or not the emulsions were putrefied by the fungus, and the results are depicted in FIG. 1.

[0108] As can be seen in FIG. 1, the vinyl acetate-ethylene copolymer emulsion of Example 1 exhibited an effect of significantly preventing fungal infiltration, compared to the emulsion of Comparative Example 2 containing no preservatives, although if in not reached the anti-fungal effect of the emulsion of Comparative Example 1, which contained a preservative.

[0109] The vinyl acetate-ethylene copolymer emulsion according to Example 1 was found to exhibit a preservative and anti-fungal effect even without treatment with a preservative such as isothiazolinone-based preservatives (e.g., MIT, CMIT, BIT, etc.) or DGH.

Experimental Example 2: Assay 2 for Anti-Fungal Resistance of VAE Emulsion

[0110] In order to examine whether the use of lactic acid in the preparation of a vinyl acetate-ethylene copolymer emulsion in Examples 1 and 2 have a preservative (anti-fungal) effect on the vinyl acetate-ethylene copolymer emulsion, an assay was conducted as follows.

[0111] A fungus strain (Aspergillus brasiliensis ATCC 16404) was inoculated to each of the final vinyl ace-tate-ethylene copolymer emulsions prepared in Examples 1 and 2 and cultured at 25° C. for 72 hours. Subsequently, a degree of contamination by fungus was investigated and the results are given in FIG. 2 and Table 1. The degrees of contamination was evaluated as follows:

[0112] * Degree of Contamination

[0113] 0: None

[0114] 1: Very low (less than 10%)

[0115] 2: Low (from 10% to less than 30%)

[0116] 3: Moderate (from 30% to less than 60%)

[0117] 4: High (60% or more)

TABLE-US-00001 TABLE 1 Sample Example 1 Example 2 Inoculum Aspergillus brasiliensis ATCC 16404 Culture Temperature 25° C. Degree of Contamination 3 1

[0118] As is understood from data of Table 1 and FIG. 2, both the vinyl acetate-ethylene copolymer emulsions of Examples 1 and 2 exhibited the effect of preventing fungal infiltration thereto despite of free of a preservative. Particularly, the emulsion of Example 2 using lactic acid in preparation thereof was found to have a higher preservative and antifungal effect, compared to that of Example 1, which did not employ lactic acid in the preparation thereof.

[0119] When prepared by using a monocarboxylic acid, such as lactic acid, in the polymerization thereof, the vinyl acetate-ethylene copolymer emulsion according to Examples was observed to be further improved in preservability and antifungal resistance.

Experimental Example 3: Preservability of VAE Emulsion

[0120] In order to examine the preservability of the VAE emulsion prepared in Example 2, an assay was conducted as follows, and the result is depicted in FIG. 3.

[0121] The vinyl acetate-ethylene copolymer emulsion prepared in Example 2 was spread on a PDA (potato dextrin agar) plate and a TSA (tryptone soya agar) plate and monitored with the naked eye for putrefaction at 25° C. for 4 days.

[0122] As shown in FIG. 3, the VAE emulsion of Example 2 was putrefied on neither of PDA nor TSA for 4 days.

[0123] As such, the VAE emulsion prepared according to the Example was found to have excellent preservability.

Experimental Example 4: Particle Size Distribution in VAE Emulsion

[0124] Size distributions of vinyl acetate-ethylene copolymer particles in the final VAE emulsions prepared in Example 2 and Comparative Example 1 were measured and the results are depicted in FIG. 4.

[0125] As is understood from the data of FIG. 4, VAE particles had an average particle size of about 1 μm in the VAE emulsion of Example 2 and about 1.2 μm in the VAE emulsion of Comparative Example 1.

[0126] It was found that the use of a co-emulsifier in the polymerization to prepare the vinyl acetate-ethylene copolymer emulsion can make VAE particle sizes smaller in the final emulsion in a controllable manner.

Experimental Example 5: Test for Water-Whitening Effect of VAE Emulsion

[0127] The final VAE emulsions prepared in Example 2 and Comparative Example 1 were tested for water resistance as follows and the results are depicted in FIG. 5.

[0128] The VAE emulsions prepared in Example 2 and Comparative Example 1 were dried to make transparent films. Then, water drops were loaded onto each transparent film. The time points at which the water drop-loaded sites of the transparent films turned white were monitored with the naked eye.

[0129] As a result of the observation, the transparent film of Comparative Example 1 became opaque (white) at 3 min. 2 sec. after a water drop was loaded thereon so that the letters under the film were not read in the site of the water drop. By contrast, the letters under the transparent film of Example 1 could be barely dis-cerned through the site of the water drop 3 min. 2 sec. after the water drop was loaded, but could not be read at all 9 min. 46 sec after the loading (see FIG. 5b).

[0130] It was thus found that a transparent film having excellent water resistance could be made of the vinyl acetate-ethylene copolymer emulsion prepared using a co-emulsifier according to the Example.

Experimental Example 6: Adhesion and Cohesion of VAE Emulsion

[0131] The final VAE emulsions prepared in Example 2 and Comparative Example 1 were measured for adhesion and cohesion as follows and the results are given in Table 2 and FIG. 6.

[0132] 1) Wet Peel (Cloth/Cloth)

[0133] A suitable amount of the VAE emulsion of Example 2 was loaded on a cloth and primarily applied using #10 rod in the top-to-bottom direction. After 60 sec., a suitable amount of the VAE emulsion of Example 2 was loaded again and secondarily applied using #40 rod in the top-to-bottom direction. After 60 sec., the lower end and the upper end of the cloth were engaged with each other and compressed using a 7Ib roller in the top-to-bottom direction. Thereafter, the cloth was dried in an incubator (25° C., 60%) for 24 hours. Then, the cloth coated with the VAE emulsion was cut to make samples having a width of 1 inch. The samples were immersed in water for 1 hour and measured for 180° peel strength, using Instron. A control sample was prepared in the same manner as is described above, with the exception of applying the VAE emulsion of Comparative Example 1 to a cloth.

[0134] 2) Peel (PVC/Cloth)

[0135] A PVC film was surface treated with methanol and cut (size: 1 inch×5 inch). Thereafter, a suitable amount of the VAE emulsion of Example 2 was loaded on the surface-treated PVC film and primarily applied using #40 rod in the top-to-bottom direction. Immediately after completion of the application, a cloth was placed on the VAE emulsion of Example 2 and compressed once using a 7Ib roller, followed by drying in an incubator (25° C., 60%) for 24 hours. Then, 180° peel strength between the PVC and the cloth was measure using Instron. A control sample was prepared in the same manner as is described above, with the exception of applying the VAE emulsion of Comparison Example 1 to a cloth.

[0136] 3) Creep Rate (Cloth/Cloth, @77° C.)

[0137] A suitable amount of the VAE emulsion of Example 2 was loaded on a cloth and primarily applied using #10 rod in the top-to-bottom direction. After 60 sec., a suitable amount of the VAE emulsion of Example 2 was loaded again and secondarily applied using #40 rod in the top-to-bottom direction. After 60 sec., the lower end and the upper end of the cloth were engaged with each other and compressed using a 7Ib roller in the top-to-bottom direction. Thereafter, the cloth was dried in an incubator (25° C., 60%) for 24 hours. Then, the cloth coated with the VAE emulsion was cut to make samples having a width of 1 inch. The sample was left at 77° C. for 15 min in an oven, with the one side thereof fixed to the oven by using a clamp. Another side of the sample was suspended by a weight of 500 g by a clamp. A dis-tance to which the cloth had been stretched per hour was measured. A control sample was prepared in the same manner as is described above, with the exception of using applying the VAE emulsion of Comparative Example 1 to a cloth.

TABLE-US-00002 TABLE 2 Control Sample Sample (Comparative Example 1) (Example 2) Wet peel (cloth/cloth) 0.071 0.123 (lb/in) Peel (PVC/cloth) (lb/in) 1.012 1.151 Creep Rate (cloth/cloth 0.75 0.56 @77° C.) (mm/min)

[0138] As can be seen in Table 2, the VAE emulsion of Example 2 was about 173% higher in wet peel and about 114% higher in peel against PVC than that of Comparative Example 1. In addition, the VAE emulsion of Example 2 was lower in creep rate than that of Comparative Example 1.

[0139] Consequently, the VAE emulsion prepared according to the present invention is superior in terms of adhesion and cohesion to conventional VAE emulsions.

BRIEF DESCRIPTION OF THE DRAWINGS

[0140] FIG. 1 is a photographic image accounting for results of an assay for anti-fungal resistance of vinyl acetate-ethylene copolymer emulsions prepared in Example 1 and Comparative Examples 1 and 2.

[0141] FIG. 2 shows photographic images accounting for results of an assay for anti-fungal resistance of vinyl acetate-ethylene copolymer emulsions prepared in Examples 1 and 2.

[0142] FIG. 3 shows photographic images accounting for the preservability of the vinyl acetate-ethylene copolymer emulsion prepared in Example 2 as measured on a TSA (tryptone soya agar) plate (a) and on a PDA (potato dextrin agar) plate (b).

[0143] FIG. 4 is a graph accounting for particle size distributions in vinyl acetate-ethylene copolymer emulsions prepared in Example 2 and Comparative Example 1.

[0144] FIG. 5 shows photographic images accounting for water resistance of the vinyl acetate-ethylene copolymer emulsions prepared in Example 1 and Comparative Example 1, taken at 3 min. 2 sec. (a) and 9 min. 46 sec. (b) after water drops were loaded on the films.

[0145] FIG. 6 is a graph accounting for wet peel of the vinyl acetate-ethylene copolymer emulsions prepared in Comparative Example 1 and Example 2.

[0146] FIG. 7 shows photographic images accounting for whether the vinyl acetate-ethylene copolymer emulsions of Example 1 (a) and Comparative Example 3 (b) have un-dergone gelation or not.