Radiation curable coatings for printed surfaces

A radiation curable coating composition includes one or more reactive monomers; a surface curing photoinitiator; an amine synergist; one or more reactive oligomeric resins; a through-cure photoinitiator; and an aqueous polymer emulsion. The composition provides an overprint varnish that can be applied in-line over a conventional lithographic ink.

The following are non-limiting representative examples of compositions included within the present invention. 
 EXAMPLE 1 Example 1 contains two types of monomer. 1 Component Wt. % difunctional acrylate monomer 20-30 trifunctional acrylate monomer 20-30 benzophenone 5-10 amine functional acrylate additive 10-15 ketone photoinitiator 1-10 polydimethyl siloxane polymer 0.5 to 5.0 acrylated epoxy monomer blend 40.0-50.0 aqueous acrylic polymer emulsion up to 60.0 
 EXAMPLE 2 Example 2 contains one or more type of monomer in an amount up to 60%. An aqueous acrylic polymer emulsion is included in an amount of up to 20%. 2 Component Wt. % difunctional and/or trifunctional acrylate monomer 20-60 benzophenone 5-10 amine functional acrylate additive 10-15 ketone photoinitiator 1-10 acrylated oligomer 20.0-50.0 aqueous acrylic polymer emulsion up to 20.0 
 EXAMPLE 3 3 Component Wt. % Difunctional acrylate monomer 12-30 Trifunctional acrylate monomer 10-30 Benzophenone 5-10 Amine functional acrylate additive 5-15 Ketone photoinitiator 1-10 Polydimethyl siloxane polymer 0.5-5.0 Acrylated epoxy monomer blend 20-50 Aqueous styrenated acrylic polymer emulsion 1.0 to 60.0 
 EXAMPLE 4 4 Component Wt. % Difunctional acrylate monomer 10-30 Trifunctional acrylate monomer 10-30 Polydimethyl siloxane polymer 0.5-5.0 Acrylated epoxy monomer blend 20-50 Aqueous Acrylic polymer emulsion 1.0 to 60.0 
 EXAMPLE 5 5 Component Wt. % Difunctional acrylate monomer 8-22 Trifunctional acrylate monomer 10-22 Benzophenone 5-10 Amine functional acrylate additive 5-15 Ketone photoinitiator 1-5 Polydimethyl siloxane 0.5-5.0 Acrylated epoxy polymer 15-50 Aqueous Polyurethane dispersion 1.0-60.0 The following tables provide a series of presently preferred examples of the present invention. All compositions shown are in weight percent (wt. %). 6 TABLE 1 (UV Curable Coatings) 1* 2 3 4 5 6 7 Tripopylene glycol diacrylate 25 20 20 20 20 25 25 Trimethylol Propane Triacrylate 25 25 20 25 20 25 25 Acrylated epoxy; Photomer 3016 31 31 31 31 31 Acrylated polyester, Laromer PE 44F (BASF) 31 27 Benzophenone 7 7 7 7 7 7 7 Amine functional acrylate, Photomer 4967 10 10 10 10 10 10 10 Ketone photoinitiator, Darocur 1173 (Ciba) 1 1 1 1 1 1 1 Polydimethyl siloxane polymer, DC-57 (Dow Corning) 1 1 1 1 1 Roshield 3120 (Rohm & Haas) 5 10 1 5 Aqueous UV reactive acrylic emulsion Joncryl 74 (S.C. Johnson) 5 10 Aqueous UV non-reactive acrylic emulsion 100 100 100 100 100 100 100 *represents the prior art. In Table 1, Example 1 is a conventional UV coating of the prior art, which does not include an aqueous emulsion. Example 2 is a UV coating with good holdout on porous paper/board stock. It is also recommended for in-line finishing of conventional lithographic inks with minimal gloss back. Example 3 is a UV coating with excellent holdout on porous paper/board stock as compared to 2 because of greater amount of reactive aqueous emulsion/dispersion. Higher than 10% emulsion/dispersion will cause machining problems. It is also recommended for in-line finishing of conventional lithographic inks. Gloss back may even be lower than Example 2. Example 4 is a UV coating with holdout comparable to 3 but gloss lower than 3 because of the non-reactive nature of aqueous emulsion. In Table 1, Example 5 is a UV coating with holdout comparable to 3 but gloss lower than 3 because of the non-reactive nature of aqueous emulsion. Higher than 10% of aqueous emulsion results in machining problems. Example 6 has a more consistent COF than conventional coatings. Example 7 has an even more consistent COF than 6. Higher than 5% of aqueous emulsion leads to clinging and blocking and also difficult to achieve higher COF. 7 TABLE 2 (UV Curable Coatings) 8 9 10 11 12 13 Tripopylene glycol diacrylate 20 20 25 25 20 20 Trimethylol Propane Triacrylate 25 20 25 25 25 20 Acrylated epoxy: Photomer 3016 Acrylated polyester, Laromer PE 44F (BASF) 32 32 31 27 32 32 Benzophenone 7 7 7 7 7 7 Amine functional acrylate, Photomer 4967 10 10 10 10 10 10 Ketone photoinitiator, Darocur 1173 (Ciba) 1 1 1 1 1 1 Polydimethyl siloxane polymer, DC-57 (Dow Corning) Roshield 3120 (Rohm & Haas) 5 10 Aqueous UV reactive acrylic emulsion Joncryl 74 (S.C. Johnson) 1 5 5 10 Aqueous UV non-reactive acrylic emulsion 100 100 100 100 100 100 In Table 2, Example 8 is a UV coating with good gluability. Example 9 is a UV coating with even better gluability than 1 and 8 because of greater amount of the aqueous emulsion/dispersion. Example 10 has a more consistent COF than conventional, comparable to 6 but lower gloss than 6 because of non-reactive nature of aqueous emulsion/dispersion. Example 11 has an even more consistent COF than 10 but lower gloss than 6 and 10 due to non-reactive nature of the aqueous emulsion/dispersion. Example 12 has gluability close to 8 but lower gloss due to non-reactive nature of aqueous emulsion/dispersion. Example 13 has gluability close to 9 but even lower gloss than 12 due to higher concentration of non-reactive aqueous emulsion/dispersion. As previously mentioned, other acrylated epoxies from Cognis, such as Photomer 3005, Photomer 3015, Photomer 4028, and the like, can be used instead of Photomer 3016. Also acrylated epoxies are available from several vendors, such as UCB Radcure (Ebecryl 3700, 3701, etc.), Sartomer (CN104, CN112, etc.)and/or BASF (EA81, LR8713, etc.). The present invention is not limited to epoxy acrylate as similar properties can be achieved using acrylated polyesters or acrylated urethanes, and the like. Also, as previously mentioned, oligomers other than Laromer PE 44F can be used to achieve similar properties including acrylated epoxies, acrylated urethanes, etc., which are available from several different vendors. Other acrylated amines, such as Photomer 4770, Ebecryl P115, etc., can be used instead of Photomer 4967. These alternatives apply to the EB Curable Coatings shown below in Tables 3 and 4 as well. 8 TABLE 3 (EB Curable Coatings) 1* 2 3 4 5 6 Tripropylene glycol diacrylate 31 31 26 31 26 32 Trimethylol proopane triacrylate 31 31 31 31 31 35 Acrylated epoxy, Photomer 3016 37 32 32 32 32 Acrylated polyester, Laromer PE 44F (BASF) 33 Polydimethyl siloxane polymer, DC 57 (Dow Corning) 1 1 1 1 1 Aqueous UV reactive acrylic emulsion 5 10 1 Roshield 3120 (Rohm & Haas) Joncryl 74 (S.C. Johnson) 5 10 Aqueous UV non-reactive acrylic emulsion 100 100 100 100 100 100 *represents the prior art In Table 3, Example 1 is a conventional EB coating of the prior art, which does not include aqueous emulsion. Example 2 is an EB coating with good holdout on porous stock. It is also recommended for in-line finishing of conventional lithographic inks with minimal gloss back. Example 3 is an EB coating with excellent holdout on porous stock; better than 2. It is also recommended for in-line finishing of conventional lithographic inks as it has higher amount of reactive aqueous emulsion. Higher than 10% of aqueous emulsion results in machining problems. Example 4 is an EB coating with holdout similar to 2 but gloss lower than 2, as the aqueous emulsion is non-UV reactive resulting in lower gloss. Also can be recommended for in-line finishing over conventional lithographic inks if gloss is not too low. Example 5 is an EB coating with holdout similar to 3 on porous stock but gloss lower than 3 because of non-reactive nature of aqueous emulsion. High than 10% of aqueous emulsion/dispersion results in machining problems. Example 6 is an EB coating with more consistent COF than conventional non-skid coatings. 9 TABLE 4 (EB Curable Coatings) 7 8 9 10 11 12 13 Tripropylene glycol diacrylate 32 31 30 32 32 31 30 Trimethylol proopane triacrylate 31 32 30 35 31 32 30 Acrylated epoxy, Photomer 3016 Acrylated polyester, Laromer PE 44F (BASF) 33 32 30 32 32 32 30 Polydimethyl siloxane polymer, DC 57 (Dow Corning) Aqueous UV reactive acrylic emulsion 5 5 10 Roshield 3120 (Rohm & Haas) Joncryl 74 (S.C. Johnson) 1 5 5 10 Aqueous UV non-reactive acrylic emulsion 100 100 100 100 100 100 100 In Table 4, Example 7 is an EB coating with even higher consistency of COF due to higher amount of reactive aqueous emulsion/dispersion. Example 8 is an EB coating with good gluability. Example 9 is an EB coating with even better gluability, better than 1 and 8 because of greater amount of the aqueous emulsion/dispersion. Example 10 is an EB coating with more consistent COF than conventional non-skid coating but lower nature of the aqueous emulsion/dispersion. Example 11 is an EB coating with even more consistent COF than 10 but lower gloss than 10 due to higher concentration of the non-reactive aqueous emulsion/dispersion. Example 12 is an EB coating with better gluability compared to the standard EB coating 1. Its gluability is comparable to 8 but gloss may be lower due to non-reactive aqueous emulsion/dispersion. Example 13 is an EB coating with even better gluability than 12 but gloss could be lower because of the higher concentration of non-reactive aqueous emulsion.