ENERGY CURABLE COMPOSITIONS COMPRISING REACTION PRODUCTS OF POLY(ALKYLENE OXIDE)-CONTAINING GLYCIDYL ETHERS AND ACRYLIC ACID

Abstract

The present invention is drawn to low migration energy-curable compositions comprising epoxy acrylates derived from the reaction of poly(alkylene oxide) containing glycidyl ethers with acrylic acid. The compositions of the invention are particularly useful for the printing or coating of food packaging.

Claims

1. Low migration energy-curable compositions comprising epoxy acrylates derived from the reaction of poly(alkylene oxide)-containing glycidyl ethers with acrylic acid, wherein the average degree of alkoxylation of any poly(alkylene oxide) of the glycidyl ether is at least 2 and the number of glycidyl ether groups per molecule is at least 1.

2. The composition of claim 1, wherein the poly(alkylene oxide) of the glycidyl ether is selected from either poly(ethylene oxide) or poly (propylene oxide) or poly(butylene oxide) or a blend thereof, and preferably from either poly(ethylene oxide) or poly(propylene oxide) or a blend thereof.

3. The composition of claim 1, wherein the glycidyl ether is a poly(ethylene glycol) diglycidyl ether or a poly (propylene glycol) diglycidyl ether or a poly(butylene glycol) diglycidyl ether.

4. (canceled)

5. The composition of claim 1, wherein the glycidyl ether is selected from the group consisting of ethoxylated or propoxylated glycerol glycidyl ethers, ethoxylated or propoxylated trimethylolpropane glycidyl ethers, ethoxylated or propoxylated ditrimethylolpropane glycidyl ethers, ethoxylated or propoxylated pentaerythritol glycidyl ethers, ethoxylated or propoxylated dipentaerythritol glycidyl ethers, and blends thereof, or wherein the glycidyl ether is selected from the group consisting of ethoxylated or propoxylated trimethylolpropane or pentaerythritol glycidyl ethers, or blends thereof.

6. The composition of claim 1, further comprising any blend of photoinitiators.

7. The composition of claim 6 which is UV-curable.

8. The composition of claim 7 which comprises 6.0% (w/w) or less, preferably which comprises less than 5.0% (w/w), of any blend of photoinitiators

9. The composition of claim 1, which is EB-curable.

10. The composition of claim 1, which is EB-curable and not UV-curable.

11. The composition of claim 10 which is essentially free of photoinitiators.

12. The composition of claim 1, which is a pigmented inkjet fluid.

13. The composition of claim 1, which comprises at least 2.0% (w/w), and preferably at least 4.0% (w/w) of the epoxy acrylate.

14. The composition of claim 1, wherein the epoxy acrylate raises the hydroxy value of the ink by at least 5.0; and more preferably by at least 10.0 mgKOH/g.

15. The composition of claim 1, further comprising free-radically polymerizable ethylenically unsaturated monomers and oligomers, such as acrylates.

16. A process for preparing a printed substrate comprising printing the composition of claim 1 onto a substrate and curing.

17. The process of claim 16, wherein the composition is exposed to both UV and EB radiation.

18. The process of claim 16, wherein the composition is partially cured using any combination of UV-LED lamps, prior to EB-curing.

19. The process of claim 16 wherein the composition is cured by EB radiation

20. (canceled)

21. (canceled)

22. (canceled)

23. A method of reducing the amount of uncured monomer in a cured ink or coating composition comprising applying the composition of claim 1 to a substrate and curing.

24. (canceled)

25. The use of the epoxy acrylates defined in claim 1 to promote the energy-cure of a free-radically polymerizable composition.

26. (canceled)

Description

EXAMPLES

[0108] The following examples illustrate specific aspects of the present invention and are not intended to limit the scope thereof in any respect and should not be so construed. These examples are illustrative and are not to be read as limiting the scope of the invention as it is defined by the appended claims.

[0109] Viscosity measured using a Brookfield DV-II+ Pro Viscometer equipped with Spindle no. 18, at 100 rpm.

[0110] Curing the Inks for Extraction Testing: For UV-curing, the inks were applied to 23 μm Melinex 813 (a polyester film) at 10 μm, and then cured with a dose of 150 mJ/cm.sup.2, using a Fusion UV Systems UV-Rig equipped with a medium pressure H-bulb. The bell speed was adjusted to deliver the required U V-dose of 150 mJ/cm.sup.2, as measured by a calibrated International Light Technologies ILT 490 Profiling Belt Radiometer (covering the UV-A and UV-B ranges).

[0111] For EB-curing, the inks were applied in the same manner as described above, but the inks were cured using an EBeam Technologies EBLab, using an accelerating voltage of 100 keV and the doses specified in the examples, with an oxygen level of less than 200 ppm.

[0112] Assessing the Level of Extractable Monomer: The levels of unbound, unreacted monomer residues in a print were determined by a ‘total extraction’ test. This test involved soaking 30cm.sup.2 of the print in 2 ml of methanol, containing 0.005% (w/w) of MEHQ (stabilizer) for 24 hours at room temperature before the methanol solution was analyzed by GC-MS. The GC-MS was calibrated with known solutions of the monomers and the results are reported as the amount of uncured monomer per unit area of print, expressed as μg/dm.sup.2.

Preparation of an Epoxy Acrylate According to the Invention: PEGDGE-AA

[0113] A 250-ml three-necked round bottom flask fitted with condenser, thermometer, gas inlet (used for air sparge with Teflon pipe), dropping funnel and stirrer was charged with 99.50 g (0.14 mol) PEG-400-DEG (a di-glycidyl ether with PEG-400 chain; product of Raschig GmbH, Germany), 0.2 g 4-methoxyphenol (polymerization-inhibitor), and 0.6 g triphenyl phosphine (catalyst). The reaction mixture was heated to 94° C. and air bubbled through the clear reaction mixture. 22 g (0.3 mol) acrylic acid was added dropwise to the mixture under stirring. After about 20 minutes, addition of the acid was complete. The reaction mixture was kept at 98° C. and the decrease of the acid number monitored. When the acid value fell below 5 mg KOH/g, the reaction mixture was allowed to cool to room temperature and the product was obtained without need for further purification as a clear liquid.

[0114] Yield: 115 g

[0115] Acid Value: <5 mgKOH/g

[0116] Viscosity: 334 mPa.Math.s @25° C., 50 s.sup.−1.

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Ink Examples

[0117] Use of PEGPGE-AA to Enhance UV-Cure: To show how the PEGDGE-AA adduct can promote the UV-cure response, in terms of a reduction in the amount of uncured monomer, inkjet compositions were prepared according to Table 1. The inks were blended using a Silverson high shear mixer.

TABLE-US-00001 TABLE 1 UV-Curable Inkjet Composition - General Formula for Subsequent Examples Component % (w/w) VEEA.sup.1 30.0 3-MePDDA.sup.2 30.0 TMPEOTA.sup.3 6.5-16.5 CN3715.sup.4  3.0 Additional Monomer.sup.5 0-10.0 Omnirad 819.sup.6  0.5 Esacure KIP160.sup.7  2.0 Onmirad 127.sup.8  2.0 TegoGlide 410.sup.9  1.0 Magenta Pigment Paste.sup.10 15.0 Notes to Table 1: .sup.1VEEA = 2-(2-vinyloxyethoxy)ethyl acrylate; .sup.23-MePDDA = 3-Methylpentanediol diacrylate; .sup.3TMPEOTA = Trimethylolpropane ethoxylate triacrylate (3 moles ethoxylation). The concwentration of this monomer was adjusted downwards to allow the incorporation of the additional monomer (5); .sup.4CN3715 = Acrylated Amine, ex. Sartomer; .sup.5The additional monomer includes PEGDGE-AA and the two control monomers PEG400DA (PEG400 diacrylate) and BDDGE-AA, which is the adduct of butanediol diglycidyl ether with acrylic acid; .sup.6Omnirad 819 = Acylphosphine oxide photoiniator, ex. IGM Resins; .sup.7Esacure KIP160 = Low migration potential hydroxyketone photoinitiator, ex. IGM Resins; .sup.8Omnirad 127 = Low migration potential hydroxyketone photoinitiator, ex. IGM Resins; .sup.9TegoGlide 410 = Polyethersiloxane; ex. Evonik Industries; .sup.10Magenta Pigment Paste = Proprietary Pigment dispersion comprising 21.0% Pigment Red 122, dipropylene glycol diacrylate, dispersants stabilisers.

[0118] Table 2 provides the results for the individual inks prepared according to Table 1, in terms of the additional monomer, the ink viscosity and the amount of uncured monomer.

TABLE-US-00002 TABLE 2 UV-Curable Inkjet Compositions and the Amount of Uncured Monomer Hydroxy Value Contributed by Additional % (w/w) Monomer Viscosity Extractable Extractable Extractable Additional Additional (mgKOH/ @ 45° C. DPGDA 3-MePDDA VEEA Monomer Monomer g (ink)) (mPa .Math. s) (μg/dm.sup.2) (μg/dm.sup.2) (μg/dm.sup.2) Comp. Ex 1 — — — 6.8 16.7 36.7 38.3 Comp. Ex 2 BDDGE-AA 2.5 8.1 7.1 9.2 16.8 20.8 Comp. Ex 3 BDDGE-AA 5.0 16.2 7.5 5.1 9.7 11.0 Comp. Ex 4 BDDGE-AA 10.0 32.4 10.6 1.1 1.4 2.1 Comp. Ex 5 PEG400DA 2.5 0 7.0 2.1 3.5 4.4 Comp. Ex 6 PEG400DA 5.0 0 7.0 2.2 3.8 5.5 Comp. Ex 7 PEG400DA 10.0 0 7.1 1.4 2.7 3.2 Inv. Ex 1 PEGDGE-AA 2.5 5.5 7.0 2.0 3.4 4.5 Inv. Ex 2 PEGDGE-AA 5.0 11.0 7.2 1.3 1.8 3.0 Inv. Ex 3 PEGDGE-AA 10.0 21.9 7.7 <0.5 <0.5 1.4

[0119] The results in Table 2 show that the low molecular weight epoxy acrylate BDDGE-AA produces a significant lowering of the amount of uncured monomer (Comparative Examples 2 to 4) compared with Comparative Example 1. This in itself is a surprising finding since it is used to replace TMPEOTA, a trifunctional acrylate monomer, which is known for its capacity to produce low migration energy-curable compositions. The fact that a trifunctional monomer is being replaced with a difunctional monomer might be expected to result in a reduction of the cure response with respect to the amount of uncured monomer in the cured ink film. The likely reason for the reduction in the amount of uncured monomer achieved with BDDGE-AA likely arises from the presence of the secondary alcohol groups in its chemical structure. A negative impact of the use of BDDGE, especially at 10.0% (w/w), is on the viscosity, which would limit its use in inkjet formulations particularly.

[0120] The highly alkoxylated monomer, PEG400DA also produces a reduction in the amount of uncured monomer, after the inks were UV-cured (Comparative Examples 5 to 7).

[0121] The most effective monomer in reducing the amount of uncured monomer, as shown in Inventive Examples 1 to 3 was PEGDGE-AA, the epoxy acrylate prepared in-line with the invention. This was particularly the case for those inks where it was used at 5 and 10.0% (w/w). As well as producing the lowest amounts of uncured monomer. Inventive Examples 2 and 3 also produced prints having the lowest odor, a further indication of low residual amounts of uncured monomer. Compared with BDDGE-AA, PEGDGE-AA did not have the same negative impact on viscosity, an advantage for the preparation of inkjet compositions.

[0122] A further point to make about the inkjet compositions of Table 2 (which were UV-cured in air) is the relatively low overall photoinitiator concentration of 4.5% (w/w). Usually, UV-curable inkjet compositions comprise significantly higher concentrations of photoinitiators to deliver satisfactory cure. The ability of inventive compositions to achieve acceptable cure with such low concentrations of photoinitiators is clearly advantageous.

[0123] To show the positive impact that epoxy acrylates according to the invention can have on EB-curing, the inkjet compositions according to Table 3 were prepared and tested for the amount of uncured monomer according to the methodology previously described.

TABLE-US-00003 TABLE 3 EB-Curable Inkjet Compositions and the Amounts of Uncured Monomer Component Comp. Ex 8 Comp. Ex 9 Comp. Ex 10 Inv. Ex 4 Inv. Ex 5 Inv. Ex 6 Inv. Ex 7 VEEA 30.0 30.0 30.0 30.0 30.0 30.0 30.0 3-MePDDA 35.0 35.0 35.0 35.0 35.0 35.0 35.0 TMPEOTA 21.0 6.0 6.0 16.0 11.0 6.0 1.0 HBA.sup.1 — 15.0 — — — — — SR9035.sup.2 — — 15.0 — — — — PEGDGE-AA — — — 5.0 10.0 15.0 20.0 CN3715 4.0 4.0 4.0 4.0 4.0 4.0 4.0 TegoGlide 410 1.0 1.0 1.0 1.0 1.0 1.0 1.0 Cyan Pigment 9.0 9.0 9.0 9.0 9.0 9.0 9.0 Paste.sup.3 Total 100 100 100 100 100 100 100 Viscosity at 5.2 4.3 6.3 5.6 6.1 6.3 6.9 45° C. (mPa .Math. s) OHV.sup.4 0 58 0 11.0 21.9 32.9 43.8 Extracted Uncured Monomer at 35 kGy (μg/dm.sup.2) DPGDA 15.1 1.9 2.1 2.8 1.1 <0.5 <0.5 3-MePDDA 35.0 4.9 4.0 6.1 1.9 <0.5 <0.5 VEEA 34.7 5.9 3.3 4.5 2.7 1.6 1.7 HBA — 7.5 — — — — — Extracted Uncured Monomer at 30 kGy (μg/dm.sup.2) DPGDA 0.9 3-MePDDA 1.5 VEEA 2.8 Extracted Uncured Monomer at 25 kGy (μg/dm.sup.2) DPGDA 4.8 3-MePDDA 10.1 VEEA 14.5 Notes to Table 3: .sup.1HBA = 4-Hydroxybutyl Acrylate; ex. Aldrich Chemicals; .sup.2SR9035 = TMPEOTA having 15 moles of ethoxylation, ex. Sartomer. This monomer was shown to be a most effective alkoxylated monomer for EB-curable inkjet compositions in WO2017180496; .sup.3Cyan Pigment Paste = a proprietary dispersion containing 25.0% (w/w) of Pigment 15:4, the remainder comprising the dispersant stabilizers and DPGDA (dipropyleneglycol diacrylate); .sup.4OHV = Hydroxy Value Contributed by Additional Monomer (mgKOH/g (ink)).

[0124] The results in Table 3 show how effective epoxy acrylates of the invention are in enhancing cure of inkjet compositions designed for EB-curing (lacking: photoinitiator). Although no photoinitiator was included in the compositions of Table 3, it should be understood that photoinitiators may be included in EB-curable ink and coating compositions comprising epoxy acrylates of the invention to facilitate a dual UV-EB curing process, as laid out in WO2017180491 and WO2017180496.

[0125] At an incorporation level of 15.0% (w/w), PEGDGE-AA, Inventive Example 6 not only produced significantly lower levels of uncured monomer than Comparative Example 8 comprising no cure boosting monomer, but also delivered lower uncured monomer levels than either 4-hydroxybutyl acrylate (Comparative Example 9) and TMPEOTA having 15 moles of ethoxylation (Comparative Example 10). These two monomers are those reported in the references as promoting the cure of EB-curable inkjet compositions.

[0126] Furthermore, Inventive Example 6 was able to produce less uncured monomer, compared with Comparative Examples 8, 9 and 10 when the EB dose was reduced from 35 kGy to 30 kGy, and less uncured monomer at 25 kGy compared with Comparative Example 8. These findings indicate that EB-curable inkjet compositions comprising epoxy acrylates of the invention would be able to achieve faster press speeds than would be achievable with the current state of the an.

[0127] The current invention has shown the surprising benefit of the inclusion of epoxy acrylates derived from the reaction poly(alkylene oxide) containing glycidyl ethers and acrylic acid, such as PEGDGE-AA demonstrated by way of the examples here. These epoxy acrylates combine the features of pol(alkylene oxide) and hydroxyl groups which both help promote the UV-, and EB-curing of inks and coatings. This is a finding not previously revealed or suggested, in the identified references.