A production method of highly unsaturated fatty acids with a high purity/high yield that compensates for shortcomings of conventional techniques is provided. A purification method of highly unsaturated fatty acids and/or derivatives thereof comprising (a) contacting and stirring first raw materials comprising the substances with a first silver salt aqueous solution to collect a first oil layer and a first aqueous layer; (b) separating the first aqueous layer into a second silver salt aqueous solution and the substances; and (c) contacting and stirring the first oil layer with the second silver salt aqueous solution for separation into an oil layer and an aqueous layer to obtain a second aqueous layer comprising the substances.

A production method of highly unsaturated fatty acids with a high purity/high yield that compensates for shortcomings of conventional techniques is provided. A purification method of highly unsaturated fatty acids and/or derivatives thereof comprising (a) contacting and stirring first raw materials comprising the substances with a first silver salt aqueous solution to collect a first oil layer and a first aqueous layer; (b) separating the first aqueous layer into a second silver salt aqueous solution and the substances; and (c) contacting and stirring the first oil layer with the second silver salt aqueous solution for separation into an oil layer and an aqueous layer to obtain a second aqueous layer comprising the substances.

The present invention provides a method of producing/purifying highly unsaturated fatty acids and/or derivatives thereof while suppressing deterioration of a silver salt aqueous solution, in production/purification of highly unsaturated fatty acids and/or derivatives thereof using the aqueous solution of silver salt. The present invention also contacts or mixes a mixture having a peroxide value (POV) of 10 or smaller with an aqueous solution of silver salt, in a method of purifying highly unsaturated fatty acids and/or derivatives thereof from a mixture comprising highly unsaturated fatty acids and/or derivatives thereof.

The present invention provides a method of producing/purifying highly unsaturated fatty acids and/or derivatives thereof while suppressing deterioration of a silver salt aqueous solution, in production/purification of highly unsaturated fatty acids and/or derivatives thereof using the aqueous solution of silver salt. The present invention also contacts or mixes a mixture having a peroxide value (POV) of 10 or smaller with an aqueous solution of silver salt, in a method of purifying highly unsaturated fatty acids and/or derivatives thereof from a mixture comprising highly unsaturated fatty acids and/or derivatives thereof.

The problem solved by the present invention is to provide a method for efficiently purifying acrylic acid derivative (I), more specifically a method for efficiently eliminating alcohol (II) from a composition containing acrylic acid derivative (I) and alcohol (II). This problem is solved by a method for purifying an acrylic acid derivative represented by Formula (I): ##STR00001##
wherein
R.sup.1 and R.sup.2 are identical or different, and each represents alkyl, fluoroalkyl, aryl that may have one or more substituents, halogen, or hydrogen,
R.sup.3 represents alkyl, fluoroalkyl, aryl that may have one or more substituents, or hydrogen, and
X represents alkyl, fluoroalkyl, halogen, or hydrogen, the method comprising
step A of bringing composition A containing the acrylic acid derivative represented by Formula (I) and alcohol represented by Formula (II):
R.sup.4OH,
wherein R.sup.4 represents C.sub.1-6 alkyl,
into contact with an acid anhydride to convert the alcohol into an ester compound that has a boiling point higher than the boiling point of the acrylic acid derivative represented by Formula (I).

The problem solved by the present invention is to provide a method for efficiently purifying acrylic acid derivative (I), more specifically a method for efficiently eliminating alcohol (II) from a composition containing acrylic acid derivative (I) and alcohol (II). This problem is solved by a method for purifying an acrylic acid derivative represented by Formula (I): ##STR00001##
wherein
R.sup.1 and R.sup.2 are identical or different, and each represents alkyl, fluoroalkyl, aryl that may have one or more substituents, halogen, or hydrogen,
R.sup.3 represents alkyl, fluoroalkyl, aryl that may have one or more substituents, or hydrogen, and
X represents alkyl, fluoroalkyl, halogen, or hydrogen, the method comprising
step A of bringing composition A containing the acrylic acid derivative represented by Formula (I) and alcohol represented by Formula (II):
R.sup.4OH,
wherein R.sup.4 represents C.sub.1-6 alkyl,
into contact with an acid anhydride to convert the alcohol into an ester compound that has a boiling point higher than the boiling point of the acrylic acid derivative represented by Formula (I).

The problem solved by the present invention is to provide a method for efficiently purifying acrylic acid derivative (I), more specifically a method for efficiently eliminating alcohol (II) from a composition containing acrylic acid derivative (I) and alcohol (II). This problem is solved by a method for purifying an acrylic acid derivative represented by Formula (I): ##STR00001##
wherein
R.sup.1 and R.sup.2 are identical or different, and each represents alkyl, fluoroalkyl, aryl that may have one or more substituents, halogen, or hydrogen,
R.sup.3 represents alkyl, fluoroalkyl, aryl that may have one or more substituents, or hydrogen, and
X represents alkyl, fluoroalkyl, halogen, or hydrogen, the method comprising
step A of bringing composition A containing the acrylic acid derivative represented by Formula (I) and alcohol represented by Formula (II):
R.sup.4OH,
wherein R.sup.4 represents C.sub.1-6 alkyl,
into contact with an acid anhydride to convert the alcohol into an ester compound that has a boiling point higher than the boiling point of the acrylic acid derivative represented by Formula (I).

The problem solved by the present invention is to provide a method for efficiently purifying acrylic acid derivative (I), more specifically a method for efficiently eliminating alcohol (II) from a composition containing acrylic acid derivative (I) and alcohol (II). This problem is solved by a method for purifying an acrylic acid derivative represented by Formula (I):

##STR00001##

wherein
R.sup.1 and R.sup.2 are identical or different, and each represents alkyl, fluoroalkyl, aryl that may have one or more substituents, halogen, or hydrogen,
R.sup.3 represents alkyl, fluoroalkyl, aryl that may have one or more substituents, or hydrogen, and
X represents alkyl, fluoroalkyl, halogen, or hydrogen, the method comprising
step A of bringing composition A containing the acrylic acid derivative represented by Formula (I) and alcohol represented by Formula (II):

R.sup.4OH,

wherein R.sup.4 represents C.sub.1-6 alkyl,
into contact with an acid anhydride to convert the alcohol into an ester compound that has a boiling point higher than the boiling point of the acrylic acid derivative represented by Formula (I).

The problem solved by the present invention is to provide a method for efficiently purifying acrylic acid derivative (I), more specifically a method for efficiently eliminating alcohol (II) from a composition containing acrylic acid derivative (I) and alcohol (II). This problem is solved by a method for purifying an acrylic acid derivative represented by Formula (I):

##STR00001##

wherein
R.sup.1 and R.sup.2 are identical or different, and each represents alkyl, fluoroalkyl, aryl that may have one or more substituents, halogen, or hydrogen,
R.sup.3 represents alkyl, fluoroalkyl, aryl that may have one or more substituents, or hydrogen, and
X represents alkyl, fluoroalkyl, halogen, or hydrogen, the method comprising
step A of bringing composition A containing the acrylic acid derivative represented by Formula (I) and alcohol represented by Formula (II):

R.sup.4OH,

wherein R.sup.4 represents C.sub.1-6 alkyl,
into contact with an acid anhydride to convert the alcohol into an ester compound that has a boiling point higher than the boiling point of the acrylic acid derivative represented by Formula (I).

The problem solved by the present invention is to provide a method for efficiently purifying acrylic acid derivative (I), more specifically a method for efficiently eliminating alcohol (II) from a composition containing acrylic acid derivative (I) and alcohol (II). This problem is solved by a method for purifying an acrylic acid derivative represented by Formula (I):

##STR00001##

wherein
R.sup.1 and R.sup.2 are identical or different, and each represents alkyl, fluoroalkyl, aryl that may have one or more substituents, halogen, or hydrogen,
R.sup.3 represents alkyl, fluoroalkyl, aryl that may have one or more substituents, or hydrogen, and
X represents alkyl, fluoroalkyl, halogen, or hydrogen, the method comprising
step A of bringing composition A containing the acrylic acid derivative represented by Formula (I) and alcohol represented by Formula (II):

R.sup.4OH,

wherein R.sup.4 represents C.sub.1-6 alkyl,
into contact with an acid anhydride to convert the alcohol into an ester compound that has a boiling point higher than the boiling point of the acrylic acid derivative represented by Formula (I).