Method for producing a polymerizable UV absorber
View Patent ↗The present invention relates to a two-stage preparation process for an organic UV absorber that has a (meth)acrylate group in the molecule and which as a result is particularly suitable for curable UV protective coatings. One example of the preparation process is:
1. A process for preparing a compound of formula (I)
A—X—CH 2 —O—C(═O)—C(R)═CH 2 (I),
where
A is
in which
Y 1 and Y 2 independently of one another are substituents of formula
in which
r is 0 or 1,
R 1 , R 2 , and R 3 independently of one another are H, OH, C 1-20 -alkyl, C 4-12 -cycloalkyl, C 2-20 -alkenyl, C 1-20 -alkoxy, C 4-12 -cycloalkoxy, C 2-20 -alkenyloxy, C 7-20 -aralkyl, halogen
X is branched or unbranched C 1-20 -alkyl,
R is H or CH 3 ,
wherein the process comprises the following steps:
reducing a compound of formula (II)
A—X—C(═O)—O—R″′ (II)
where A and X have the above definitions and R″′ is branched or unbranched C 1-20 -alkyl, C 4-12 -cycloalkyl, or C 6-12 -aryl substituted optionally by C 1-12 -alkyl, C 1-12 -alkoxy, CN and/or halogen;
to give a compound of formula (IIa)
A—X—CH 2 OH (IIa), and
reacting the compound (IIa) with (meth)acrylic acid and/or with an anhydride, acid chloride or ester of (meth)acrylic acid.
2. The process according to claim 1 , wherein X is CH(CH 3 ).
3. The process according to claim 1 , wherein r in each of the substituents Y 1 and Y 2 is 1.
4. The process according to claim 1 , wherein the radicals R 1 , R 2 and R 3 in each of the substituents Y 1 and Y 2 are H.
5. The process according to claim 1 , wherein the reducing of the compound (II) to the compound (IIa) takes place with a complex hydride as reducing agent.
6. The process according to claim 1 , wherein the reducing of the compound (II) to the compound (IIa) is carried in a solvent mixture comprising tetrahydrofuran and an alcohol.
7. The process according to claim 1 , wherein the reacting of the compound (IIa) takes place with (meth)acrylic acid and/or (meth)acrylic esters and in the presence of benzenesulfonic acid and/or toluenesulfonic acid as catalyst.