Method for preparing keto-functionalized aromatic (meth)acrylates

1. A method for the preparation of a keto-functionalized aromatic (meth)acrylate, comprising reacting a keto-functionalized aromatic alcohol or a keto-functionalized aromatic amine with (meth)acrylic anhydride in the presence of a catalyst, wherein the catalyst is an acid with a pK a of <2 or a base with a pK b of <9, in which reactants, products formed and catalyst are present together in a reaction matrix at a reaction temperature of between 50° C. and 120° C., and wherein:

a) the reactants, products formed and catalyst have a residence time in the reaction matrix that is restricted to from 0.1 to, at most, 4 hours; and

b) the (meth)acrylic anhydride used comprises a content of (meth)acrylic acetic anhydride of <4.5%.

2. The method of claim 1 , wherein the keto-functionalized aromatic alcohol or the keto-functionalized aromatic amine has its keto function adjacent to the aromatic system.

3. The method of claim 1 , wherein the keto-functionalized aromatic alcohol or the keto-functionalized aromatic amine comprises either a free NH 2 or a free OH group on its aromatic system.

4. The method of claim 1 , wherein the keto-functionalized aromatic (meth)acrylate is precipitated by addition of water or of an organic solvent into the reaction mixture and is isolated in solid form by filtration.

5. The method of claim 1 , wherein the keto-functionalized aromatic alcohol or the keto-functionalized aromatic amine comprises either a free NH 2 or a free OH group linked via a spacer unit to its aromatic system.

6. The method of claim 5 , wherein the spacer unit is, or comprises, an oligoether, alkyl, aryl, ether, thioether, amine, ester, thioester, or amide.

7. The method of claim 1 , wherein the reaction matrix further comprises a stabilizer at the start of the reaction and the stabilizer is present at a concentration of between greater than 0 and 5000 ppm based on the keto-functionalized aromatic alcohols or amines used.

8. The method of claim 1 , wherein the (meth)acrylic anhydride used has a purity of >93% and the reaction has a duration of 1 to 3 hours.

9. The method of claim 1 , wherein: a) said catalyst is an acid and, after the reaction is complete, the catalyst is neutralized with a base; and b) after neutralization, the Pt—Co colour index is, or is adjusted to <500 APHA, measured as a 30 wt % solution of the keto-functionalized aromatic (meth)acrylate in 60 wt % methyl methacrylate and 10 wt % methacrylic acid.

10. The method of claim 1 , wherein the product is treated with an adsorbent and, after the treatment, the adsorbent is removed to give a product with a Pt—Co colour index of <500 APHA measured as a 30 wt % solution of the keto-functionalized aromatic (meth)acrylate in 60 wt % methyl methacrylate and 10 wt % methacrylic acid.

11. The method of claim 1 , wherein the reaction is interrupted at a conversion of >90% of the keto-functionalized aromatic alcohol or keto-functionalized aromatic amine.

12. The method of claim 1 , wherein the reaction is carried out in the presence of catalytic amounts of acid.

13. The method of claim 12 , wherein said acid is sulfuric acid, alkylsulfonic acid or arylsulfonic acid.

14. The method of claim 12 , wherein, after the reaction, the catalytic amounts of acid are neutralized with an aqueous base.

15. The method of claim 14 , wherein the aqueous base is an aqueous alkali metal hydroxide solution or ammonia solution.

16. The method of claim 1 , wherein the reaction is carried out over 1-3 hours at 60 to 95° C.

17. The method of claim 1 , further comprising addition of a liquid (meth)acrylic ester or styrene into the reaction mixture at the end of the reaction.

18. The method of claim 3 , wherein the keto-functionalized aromatic (meth)acrylate is precipitated by addition of water or of an organic solvent into the reaction mixture and is isolated in solid form by filtration.

19. The method of claim 18 , wherein: a) said catalyst is an acid and, after the reaction is complete, the catalyst is neutralized with a base; and b) after neutralization, the Pt—Co colour index is, or is adjusted to <500 APHA, measured as a 30 wt % solution of the keto-functionalized aromatic (meth)acrylate in 60 wt % methyl methacrylate and 10 wt % methacrylic acid.

20. The method of claim 1 , wherein (meth)acrylic anhydride is reacted with 4-hydroxybenzophenone and at the end of the reaction, and prior to processing, there is 0.723% or less of 4-(acetoxy)benzophenone in the product.

21. The method of claim 1 , wherein the reaction is carried out in the presence of catalytic amounts of aqueous sodium hydroxide solution.

22. The method of claim 1 , wherein the keto-functionalized aromatic alcohol is 4-hydroxybenzophenone or 4-chloro-4′-hydroxybenzophenone; and the keto-functionalized aromatic amine is 2-amino-5-chlorobenzophenone.