JPS6363575B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for reducing acetic acid bromination of ethylene-vinyl acetate copolymer. Ethylene-vinyl acetate copolymer can be used as a film,
It is used in a wide range of fields such as molded products, adhesives, extrusion coating materials, and polymer modification materials. It may give off a smell and be disliked. Of these, most of the vinyl acetate monomer odor can be physically removed during copolymer production, but the acetic acid odor generated during molding is difficult to physically remove, and compared to conventional methods. , calcium oxide (Special Publication No. 37-6626), organometallic salts and aliphatic polyhydric alcohols (Special Publication No. 47-6626)
No. 13855), higher fatty acid metal compounds (Special Publication No. 1972-
31690), or group metal hydroxides, oxides, carbonates or alcoholates (JP-A-46-12338)
), metallic soaps and organic phosphites, etc. (JP-A-49-37116), activated carbon (JP-A-49-99545),
Organic amines (JP-A-49-99550), oil-soluble alkylaryl sulfonates (JP-A-60-55646)
A method has been proposed to suppress the generation of free acetic acid during high-temperature processing by adding such substances. However, most of these additives inhibit the transparency of the product or
Many of them are colored, emit strange odors, and are not approved as food additives. Furthermore, when a composition containing an alkali metal hydroxide or carbonate is molded, there is a risk that the inner surface of the molding machine will be corroded, which is not preferable. Therefore, the present inventor has discovered that by adding an alkali hydrogen phosphate or an alkaline earth metal salt to an ethylene-vinyl acetate copolymer, high-temperature molding can be performed more effectively than in the various known methods described above. The present invention has been completed by discovering a low acetic acid bromination method for ethylene-vinyl acetate copolymer that suppresses the generation of free acetic acid during production, does not impair the transparency of the product, and does not generate off-flavors. The alkali or alkaline earth metal hydrogen phosphate used in the present invention includes potassium dihydrogen phosphate, dipotassium hydrogen phosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate, calcium dihydrogen phosphate, and hydrogen phosphate. These are dicalcium, magnesium dihydrogen phosphate, and dimagnesium hydrogen phosphate, and all of them may be either crystalline or anhydrous. Note that crystalline alkali hydrogen phosphate and alkaline earth metal salts are both approved as food additives. In the present invention, the ethylene-vinyl acetate copolymer is a copolymer consisting of ethylene and vinyl acetate, and the appropriate amount of alkali hydrogen phosphate or alkaline earth metal salt to be added varies depending on the composition of the copolymer. However, the odor of the copolymer can be reduced by adding in an amount of 0.01 to 5 parts by weight. In the present invention, when an antioxidant is used in combination, the odor resistance effect of the copolymer is further improved due to a synergistic effect. As antioxidants, 2,6-di-t-butyl-p-cresol, 1,3,5-trimethyl-
2,4,6-tris(3',5'-di-t-butyl-
4'-Hydroxybenzyl)benzene, 1,1,3
-tri(2-methyl-4-hydroxy-5-t-
butylphenyl)butene, octadecyl-3(3,
5-di-t-butyl-4-hydroxyphenyl)
Propionate, tetracis [methylene-3-
(3',5'-di-t-4-hydroxy-phenyl)
propionate] methane, 2,2'-thiobis(4
-methyl-6-t-butylphenol), 1,3,
5-tris(4-t-butyl-3-hydroxy-
2,6-dimethyl)isocyanurate, 6(4-
Hydroxy-3,5-di-t-butylanilino-
Phenolic compounds such as 2,4-bisoctylthio-1,3,5-triazine) are suitable. The amount of the antioxidant used in the present invention is 0 to 1 part by weight per 100 parts by weight of the copolymer. Even if more than 1 part by weight is added, no effect can be expected considering the amount added, and there is a risk that it will stand out on the surface of the product. In the present invention, there is no problem in using a slip agent, an anti-blocking agent, an ultraviolet inhibitor, or other additives in combination. Example 1 1% of various compounds were added to 50g of an ethylene-vinyl acetate copolymer having a melt index of 0.5 and a vinyl acetate content of 5.0% by weight, and kneaded at 160°C for 5 minutes using a Brabender plastograph. This kneaded material was pressed at 150°C for 5 minutes to form a sheet and then into pellets. This pellet was subjected to gas analysis using an F-45 head space analyzer (manufactured by PerkinElmer). The method is to put 5g of pellets in a container with a capacity of 20
ml vial was kept at 115°C for 2 hours, and the gas in the head space of the vial was introduced into a column (PEG-1500) at 100°C for 3 seconds with 1.5 par helium. The acetic acid peak that appeared at 1.6 minutes (time) was recorded using Chromatopack (manufactured by Shimadzu Corporation) CRA-1. Next, the kneaded product was formed into a 100 μm film by press molding, and the degree of haze was measured using NDH-2D (manufactured by Nippon Denshoku Kogyo). The results are shown in Table 1.

[Table] Mu 〓
Example 2 To 50 g of an ethylene-vinyl acetate copolymer having a melt index of 3.0 and a vinyl acetate content of 18% by weight, 1% of various compounds were added and kneaded at 150°C for 5 minutes using a Brabender plastograph. This kneaded material was pressed at 150° C. for 5 minutes to form a sheet and pelletize. This pellet was subjected to gas analysis using an E-45 head space analyzer. The method is 5
A vial containing g of pellets was kept at 100℃ for 2 hours, and the gas in the headspace of the vial was introduced into a column (PEG-1500) at 100℃ for 3 seconds with 1.5 bar of helium, resulting in a sensitivity of 1×4. in,
The acetic acid peak that appeared at RT 1.6 minutes was read using a CRA-1 recorder. The results are shown in Table 2. Table 2 Amount of acetic acid gas generated Additive Acetic acid peak area (mV.see) - 0.92 Dipotassium hydrogen phosphate 0.10 Disodium hydrogen phosphate (crystal) 0.06 Dicalcium hydrogen phosphate 0.13 Example 3 Melt index 2.5, vinyl acetate content For 50 g of 10% by weight ethylene-vinyl acetate copolymer, disodium hydrogen phosphate (crystals), tetracis[methylene-3(3',5'-di-t-4-hydroxyphenyl)propionate]methane ( Product name
Irganox 1010 (manufactured by Geigy) was added and kneaded at 150°C for 5 minutes using a Brabender Plastograph. This kneaded material was subjected to gas analysis in the same manner as in Example 2. The results are shown in Table 3.

【table】

Claims (1)

[Claims] 1. A low acetic acid bromination method for ethylene-vinyl acetate copolymer, which comprises adding 0.01 to 5 parts by weight of alkali hydrogen phosphate or alkaline earth metal salt to 100 parts by weight of ethylene-vinyl acetate copolymer. .