Plasticized UV/EB cured coatings

Abstract

A plasticized ultraviolet electron beam (UV/EB) canonically cured coating, such as a release layer or print from UV/EB cured inks, comprises polymers with a reactive plasticizer incorporated therein. The cured coating contains the plasticizing additives permanently attached to the polymer matrix, locking them in place, and permanently flexibilizing the cured coating. The cured coating finds use on varied substrates including printable substrates used in conventional printers and those with release layers for adhesive labels. Coating formulations which form these canonically cured coatings comprise canonically polymerizable monomers and/or oligomers, a reactive plasticizer which is food grade, cosmetic grade, medical grade or biologically benign when incorporated in the polymer backbone, and a catalyst.

Claims

1. A plasticized ultraviolet or electron beam (UV/EB) cationically cured coating formulation comprised of polymers formed from: component A: a cationically polymerized monomers and/or oligomers, which are epoxy monomers, epoxy oligomers, oxetane monomers, oxetane oligomers, vinyl ether monomers, vinyl ether oligomers, or combinations thereof, the epoxy monomers or epoxy oligomers having a viscosity of 25.000 cps or less at 25° C. in the absence of a solvent, and component B: at least one plasticizer which is permanently integrated within the cured coating formulation, wherein the at least one plasticizer is completely incorporated into the polymer backbone and wherein the at least one plasticizer is chosen from: polypropanediol dimer dilinoleate, dimer dilinoleyl dimer dilinoleate, polyglyceryl-6 behenate, polyglyceryl-6 polyricinoleate, diisopropyl dimer dilinoleate or combinations of two or more thereof.

2. The cured coating formulation of claim 1, further comprising at least one coupling agent having the formula R.sup.1.sub.n—Si—OR.sup.2.sub.(4-n), where n is 2 and R.sup.1 contains a cycloaliphatic epoxy, vinyl ether, or oxetane moiety, and R.sup.2 is an optionally substituted C.sub.1-6hydrocarbon.

3. The cured coating formulation of claim 1, further comprising at least one or more coupling agents selected from the group consisting of: 2-(3,4-epoxycyclohexyl)ethyl methyl diethoxy silane, 2-(3,4-epoxycyclohexyl)ethyl triethoxy silane, 2-(3,4-epoxycyclohexyl)ethyl trimethoxy silane, 5,6-epoxyhexyl triethoxy silane, and combinations thereof.

4. The cured coating formulation of claim 1, the composition further comprising at least one of colorants, pigment dispersants, defoamers, and fillers.

5. The cured coating formulation of claim 1, wherein the cured coating formulation is a release layer for an adhesive label.

6. The cured coating formulation of claim 1, wherein the oxetane monomers or oxetane oligomers are of the formula: ##STR00003## wherein R, R.sub.1, R.sub.2, and R.sub.3 are each, independently, H or C.sub.1-8 alkyl with the proviso that at least one of R.sub.1 and R.sub.2 are non-hydrogen substituents.

7. The cured coating formulation of claim 6, wherein at least one of R.sub.1 and R.sub.2 is —CH.sub.2OH or —CH.sub.2(OH)(CH.sub.3).

8. The cured coating formulation of claim 6, wherein the oxetane monomers or oxetane oligomers have a viscosity of 25,000 cps or less at 25° C., in the absence of a solvent.

9. The cured coating formulation of claim 1, wherein vinyl ether monomers or vinyl ether oligomers are of the formula: ##STR00004## wherein R and R′ are each, independently, H or C.sub.1-8 alkyl.

10. The cured coating formulation of claim 9, wherein R and R′ are each H.

11. The cured coating formulation of claim 9, wherein at least one of R and R′ is CH.sub.3.

12. The cured coating formulation of claim 9, wherein the vinyl ether monomers or vinyl ether oligomers have a viscosity of 25,000 cps or less at 25° C., in the absence of a solvent.

13. A plasticized ultraviolet or electron beam (UV/EB) cationically cured coating formulation comprised of polymers formed from: component A: a cationically polymerized monomers and/or oligomers, which are epoxy monomers, epoxy oligomers, oxetane monomers, oxetane oligomers, vinyl ether monomers, vinyl ether oligomers, or combinations thereof, and component B: at least one reactive plasticizer which is permanently integrated within said composition, wherein: the at least one reactive plasticizer possesses one or more functional groups that react as chain transfer groups or chain terminating groups with cationically polymerized monomers and/or oligomers, the at least one reactive plasticizer is completely incorporated into the polymer backbone and is biologically benign in that state, further comprising at least one coupling agent having the formula R.sup.1.sub.n—Si—OR.sup.2.sub.(4-n), where n is 2 and R.sup.1 contains a cationic-reactive group which is a cycloaliphatic epoxy, vinyl ether, or oxetane moiety, and R.sup.2 is an optionally substituted C.sub.1-6hydrocarbon, and said composition forms a printed ink image.

14. The cured coating formulation of claim 13, wherein the at least one reactive plasticizer is: polypropanediol dimer dilinoleate, dimer dilinoleyl dimer dilinoleate, polyglyceryl-6 behenate, polyglyceryl-6 polyricinoleate, diisopropyl dimer dilinoleate or combinations of two or more thereof.

15. A plasticized ultraviolet or electron beam (UV/EB) cationically cured coating formulation comprised of polymers formed from: component A: a cationically polymerizable monomers and/or oligomers selected from epoxy monomers, epoxy oligomers, oxetane monomers, oxetane oligomers, vinyl ether monomers, vinyl ether oligomers, or combinations thereof, and component B: at least one reactive plasticizer, wherein the at least one reactive plasticizer possesses two or more functional groups that react as chain transfer groups or chain terminating groups with the cationically polymerized monomers and/or oligomers, wherein the at least one reactive plasticizer is completely incorporated into the polymer backbone and is biologically benign in that state, and component C: a cationic photoinitiator wherein: the at least one reactive plasticizer is a polydimethyl silicone polymer with diol end groups which completely incorporates in the polymer backbone and is biologically benign in that state, and further comprising at least one coupling agent having the formula R.sup.1.sub.n—Si—OR.sup.2.sub.(4-n), where n is an integer of 1 or 2 R.sup.1 contains a cationic-reactive group which is a cycloaliphatic epoxy, vinyl ether, or oxetane moiety, and R.sup.2 is an optionally substituted C.sub.1-6hydrocarbon.

16. The cured coating formulation of claim 15, wherein the at least one or more coupling agents is: 2-(3,4-epoxycyclohexyl)ethyl methyl diethoxy silane, 2-(3,4-epoxycyclohexyl)ethyl triethoxy silane, 2-(3,4-epoxycyclohexyl)ethyl trimethoxy silane, or 5,6-epoxyhexyl triethoxy silane.

17. The cured coating formulation of claim 15, which is an ink.

18. The cured coating formulation of claim 15, wherein the coating is a release layer for an adhesive label.

Description

EXPERIMENTAL EXAMPLES

(1) Seven coating formulations were prepared with the epoxy-functional linear polydimethylsiloxane polymer formulation UV POLY 230 available from Bluestar Silicones® of New Brunswick N.J. This was a formulated release coating, containing an iodonium borate salt cationic photoinitiator at 2.5 wt %. The formulations had a viscosity in the range of 500-600 cps at 25° C. An unmodified formulation served as a control, while the other 6 formulations each included a different reactive plasticizer.

(2) The coating formulations were run on a conventional printing press to print release layers for linerless labels at a coating-weight of 1.1±0.1 g/cm.sup.2. The release coatings were printed over the topcoated thermally reactive coating of a direct thermal paper substrate (Kanzaki KL370NCR) and the pressure sensitive adhesive was applied to the reverse (uncoated) side of the web. The release coatings were cured upon exposure to 35-40 mJ/cm.sup.2 UV radiation. Exposing each of the coating formulations to UV light caused a rapid polymerization, curing each to form a tack-free, smear-free layer in less than 1 second directly on the roll stock. About 20 days after printing, rolls of linerless labels were obtained after running the printed web through a slitter.

(3) Of the seven formulations, five produced suitable linerless label stock which did not experience picking or blocking at the slitter, including the control UV230 without any reactive plasticizer. All experimental formulations improved the flexibility of the silicone release layer based on 1 mm Mandrel Bend testing observed under optical microscopy and all provided resilient layers that passed rub tests.

(4) The five formulations which produced suitable label stock without picking or blocking at the slitter had the following reactive plasticizers in the amounts shown in Table 1:

(5) 1) none,

(6) 2) Pelmol P3D (Phoenix),

(7) 3) Pelmol DD (Phoenix),

(8) 4) UV9440E (Momentive) and

(9) 5) UV9440E (Momentive) and SIE4668.0 (Gelest).

(10) TABLE-US-00002 TABLE 1 Additives Evaluated as Weight % Composition Example Commercial Phoenix Phoenix Momentive Gelest Number UV230 Pelmol P3D Pelmol DD UV9440E SIE 4668.0 1 100% Bluestar UV230 Control 3 95% 5% (95.0%) (5.01%) 4 95% 5% (95.0%) (5.02%) 2 95% 5% (95.0%) (5.00%) 5 94.5% 5% 0.5% (94.3%) (5.15%) (0.54%)

(11) The values for weight % composition shown in the tables are target values. The actual values for weight % composition on press are shown in parenthesis.

(12) Three cases (30 rolls/case, for a total of 90 rolls; each roll was 270 ft long, or 4.6 miles of receipts) of each linerless label stock formulation were sequentially printed in a thermal printer without periodic cleaning of the thermal printhead and evaluated for print defects, which are indicative of mechanical release coating damage. Defects were manifested by gaps in a specific region of the test receipt image printed by the thermal printer. Such gaps are primarily attributed to the buildup of residue on the thermal printhead, which acts as thermal insulation, reducing the ability of the printhead to activate the direct thermal coating. In addition to the number of gaps, the defects were further characterized by the size (width) of the gaps in the printed image. The data are based on a sampling rate of 1% of the simulated receipts printed (120 of 12,000 receipts printed per case). The results are summarized in Table 2 below.

(13) TABLE-US-00003 TABLE 2 Print Defects All Defects by Total Defects Case—30 Rolls by Size—90 rolls Sample Tested Case 1 Case 2 Case 3 1/32″- 1/16″ 1/16″-⅛″ >⅛″ Comments Example 1: 32 47 90 54 114 1 total defects per Case or size Standard UV230 0.267 0.392 0.750 0.150 0.317 0.003 % defects per Case or size CONTROL 266.7 391.7 750.0 150.0 316.7 2.8 Defect rate/1000 per case or size Example 2: 49 67 65 78 101 2 total detects per Run or size 5% UV9440E 0.408 0.558 0.542 0.217 0.281 0.006 % defects per Run or size 408.3 558.3 541.7 216.7 280.6 5.6 Defect rate/1000 per case or size Example 3: 0 12 15 24 3 0 total defects per Run or size 5% Pelmol P3D 0.000 0.100 0.125 0.067 0.008 0.000 % defects per Run or size 0.0 100.0 125.0 66.7 8.3 0.0 Defect rate/1000 per case or size Example 4: 2 0 0 2 0 0 total defects per run or size 5% Pelmol DD 0.017 0.000 0.000 0.006 0.000 0.000 % defects per run or size 16.7 0.0 0.0 5.6 0.0 0.0 Defect rate/1000 per case or size Example 5: 0 0 0 0 0 0 total detects per run or size Example 2 plus 0.000 0.000 0.000 0.000 0.000 0.000 % defects per run or size 0.5% SIE 4668.8 0.0 0.0 0.0 0.0 0.0 0.0 Defect rate/1000 per case or size

(14) The data in Table 2 shows significantly reduced, print defects (less damage) by incorporation of 3 of the 4 reactive plasticizers that react into the polymer backbone of the release layer. The standard UV silicone (control) formulation had a total of 181 defects in 360 evaluated receipts, for a defect rate of 470/1000 receipts, whereas Example 3 had a total of 27 defects in 360 evaluated receipts, for a defect rate of 75/1000 and Example 4 had a total of 2 defects in 360 evaluated receipts, for a defect rate of 6/1000. The importance of the combined interactions between the reactive plasticizer, the cure chemistry and the substrate is demonstrated by comparing the results in Examples 2 and 5. Importantly, while the reactive plasticizer in Example 2 showed no improvement in the number of total detects, with a defect rate of 503/1000 receipts, when a coupling agent was added to the same formulation of reactive plasticizer and silicone, no defects occurred.

(15) The preceding examples can be repeated with similar success by substituting the generically or specifically described reactants and/or operating conditions of this invention for those used in the preceding examples.

(16) From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.