Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1997-12-05
2001-09-11
Reddick, Judy M. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S060000
Reexamination Certificate
active
06288165
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for producing vinyl acetate polymers, in particular ethylene-vinyl acetate copolymer, a process for producing high-quality saponified products of vinyl acetate polymers, particularly of ethylene-vinyl acetate copolymer, that are obtained by saponifying the same and cause little coloring and generation of gel-like agglomerates upon molding, and also to resin compositions comprising the saponified products.
2. Description of the Prior Art
Saponified products of vinyl acetate polymers have been used in a variety of applications utilizing their feature of having good hydrophilic property. Among the saponified products, that of ethylene-vinyl acetate is good in melt moldability and especially in oxygen barrier properties, oil resistance, antistatic property, mechanical strength and like properties and hence is useful as packaging material, such as film, sheet or container. The saponified product of ethylene-vinyl acetate copolymer should, when used for various packaging purposes, have the desired properties to meet the intended purposes and, in addition, should not cause even slight coloring of appearance, fish eyes, gel-like agglomerates, coarse grain and poor transparency.
However, the saponified product of ethylene-vinyl acetate copolymer tends to cause, on melt molding, the problems of coloring and generation of gel-like agglomerates. The following various measures have therefore been proposed to suppress the coloring and generation of gel-like agglomerates.
For example, many Japanese Patent Applications disclosing addition of acids such as acetic acid and phosphoric acid or salts thereof have been filed. See Japanese Patent Application Laid-open Nos. 25048/1973, 26993/1976, 28891/1976, 49294/1976, 91988/1976, 954/1977, 955/1977, 956/1977, 20044/1981, 41204/1981, 95043/1986, 95054/1986, 143954/1987 and others. They claim that saponified products of ethylene-vinyl acetate causing little coloring or gel-like agglomerates can be obtained by conducting solution polymerization of ethylene and vinyl acetate with a radical initiator in an organic solvent such as methanol, purging the unreacted vinyl acetate, saponifying the residue by adding an alkali catalyst and, after naturalization and washing, adding on acid such as acetic acid or phosphoric acid, and/or a salt thereof, following by drying.
On the other hand, Japanese Patent Application Laid-open No. 197603/1986 discloses a method of adding a specific aromatic compound after copolymerization of ethylene and vinyl acetate. That is, addition of a specific aromatic compound such as 2,4-diphenyl-4-methyl-1-pentene on completion of copolymerization of ethylene-vinyl acetate copolymer, followed by saponification, can yield a saponified product of the ethylene-vinyl acetate copolymer that generates no irregular odor on melt molding and gives films having good color shade and little fish eye.
As stated above, there have been taken a variety of measures against coloring or generation of gel-like agglomerates of saponified products of vinyl-acetate polymers, in particular that of ethylene-vinyl acetate copolymer.
However, with the addition of an acid such as acetic acid or phosphoric acid and/or a salt thereof, coloring or generation of gel-like agglomerates still occurs if sufficient neutralization and washing after saponification are not conducted or the acid such as acetic acid or phosphoric acid and/or a salt thereof are not added in appropriate amounts. To overcome this drawback, washing is now sufficiently conducted after saponification and the addition amounts of acetic acid or phosphoric acid and a salt thereof have been optimized, only to produce unsatisfactory results.
The addition of a specific aromatic compound (e.g. 2,4-diphenyl-4-methyl-1-pentene) is, as has become clear as a result of a repeating test conducted by the present inventors, can be hardly said to suppress coloring or generation of gel-like agglomerates sufficiently.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a process for producing high-quality saponified products of vinyl acetate polymers, as obtained by saponification of vinyl acetate polymers, in particular ethylene-vinyl acetate copolymer, the saponified products causing little coloring and generation of gel-like agglomerates on molding.
Another object of the present invention is to provide a resin composition having the above excellent features.
The present invention provides a process for producing vinyl acetate polymers which comprises, after polymerizing at least one monomer comprising vinyl acetate, adding a conjugated polyene having a boiling point of at least 20° C.
The present invention also provides a process for producing saponified products of vinyl acetate polymers which comprises saponifying the vinyl acetate polymers obtained by the above process.
the present invention further provides a resin composition comprising a saponified product of a vinyl acetate polymer and 0.000001 to 1% by weight of a conjugated polyene having a boiling point of at least 20° C.
DETAILED DESCRIPTIONS OF THE PREFERRED EMBODIMENTS
The polyene referred to in the present invention has a structure compressing carbon-carbon double bonds and carbon-carbon single bonds alternately, in which the number of carbon-carbon double bonds is at least 2, and thus includes compounds having what is known as conjugated double bonds.
The polyene may be a conjugated diene having a structure comprising 2 carbon-carbon double bonds and one carbon-carbon single bond connected alternately, may be a conjugated triene having a structure comprising 3 carbon-carbon double bonds and 2 carbon-carbon single bond connected alternately, or may be a conjugated polyene having a structure comprising a larger number of carbon-carbon double bonds and carbon-carbon single bonds connected alternately. Accordingly, conjugated trienes such as 2,4,6-octstriene are included in the polyene used in the invention. However, the of polyenes having not more than 7 conjugated carbon-carbon double bonds are preferred, since those with 8 or more conjugated carbon-carbon double bonds will color by themselves.
Usable polyenes also include those comprising a plurality of conjugated double bonds containing at least 2 carbon-carbon double bonds, each of which does not conjugate together. For example, tung oil, which has 3 conjugated trienes in a molecule, is also included in the polyene used in the invention.
These polyenes may contain, in addition to the above conjugated double bonds, other functional groups, e.g. carboxyl group and salts thereof, hydroxyl group, ester group, carbonyl group, ether group, amino group, imino group, amide group, cyano group, diazo group, nitro group, sulfone group, sulfoxide group, sulfide group, thiol group, sulfonic acid and salts thereof, phosphoric acid and salts thereof, phenyl group, halogen atoms, double bond and triple bond. These functional groups may either be directly bound to the carbon atoms constituting the conjugated double bonds or bound to an optional location apart from the conjugated double bonds. This means that a multiple bond contained in the functional group may be located at a position conjugatable with the above conjugated double bonds. For example, 1-phyenylbutadiene having a phenyl group and sorbic acid having a carboxyl group are also included in the polyene used in the invention.
Too large an amount of the polyene remaining in the resulting saponified products is not always desirable, because it causes generation of bad odor, oozing out and like unfavorable effects, in consideration that the products are widely used for packaging purposes. From this viewpoint, it is desirable, in order to obtain molded articles suited for packaging contains containing little residual polyene, to select those polyenes that have functional groups containing oxygen atom and are readily removable from the resulting resin during saponification and the succeeding washing step such as water washing. T
Aoyama Akiko
Aoyama Akimasa
Ikeda Kaoru
Kawahara Takaharu
Moritani Takeshi
Aoyama Akiko
Kuraray Co. Ltd.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Reddick Judy M.
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