Urethane acrylates for curable coatings

Abstract

A urethane (meth)acrylate not comprising caprolactone is the product of reaction of A) a monoalcohol bearing from 1 to 5 (meth)acrylates, B) an allophanate-modified polyisocyanate, C) optionally, in the presence of a saturated polyol of functionality 2 to 3, D) optionally, in the presence of an unsaturated polyol with a hydroxyl functionality of 2 to 4, said polyol being C.sub.3 to C.sub.18, E) optionally, in the presence of a reactive diluent. A process for preparing the urethane (meth)acrylate includes reacting the monoalcohol A) and the polyisocyanate B) in the optional presence of C), D), and/or E). The urethane (meth)acrylate may be used in curable compositions for coatings, in particular for varnishes and inks, adhesives, adhesion primers, coatings for wood, metal or plastic and application by spray gun and provide a good compromise between reactivity, flexibility, adherence, hardness, and ease of use.

Claims

1. A urethane (meth)acrylate, comprising the product of reaction of: A) at least one monoalcohol bearing n (meth)acrylate groups with n ranging from 1 to 5, B) at least one allophanate-modified polyisocyanate, said polyisocyanate bearing at least one allophanate group in its structure and resulting from the reaction of an aromatic or aliphatic or cycloaliphatic initial polyisocyanate in excess with a monoalcohol, under conditions allowing the formation of allophanate by reaction of at least a second molecule of said initial polyisocyanate, with at least one formed urethane group, wherein said polyisocyanate has the general formula (I) below:
O═C═N—R.sub.1—N(R.sub.2)—C(═O)—NH—R.sub.1—N═C═O  (I) with R.sub.1: C6 alkylene or cycloalkylene, R.sub.2: —C(═O)—OR.sub.3 with R.sub.3 being the residue of a C.sub.6 to C.sub.36 alkanol, C) optionally, in the presence of at least one saturated polyol of functionality ranging from 2 to 3, D) optionally, in the presence of an unsaturated polyol of functionality ranging from 2 to 4 of hydroxyl, optionally bearing at least one or two (meth)acrylate groups, said polyol being C.sub.3 to C.sub.18, E) optionally, in the presence of a reactive diluent, which is a diluent which is radically polymerizable with said urethane (meth)acrylate, wherein the urethane (meth)acrylate does not comprise caprolactone in its structure.

2. The urethane (meth)acrylate as claimed in claim 1, wherein said polyisocyanate B) is an allophanate-modified diisocyanate having trimers and derived from a starting polyisocyanate from among: hexamethylene diisocyanate (HNDI), toluene diisocyanate (TDI), isophorone diisocyanate (IPDI) or the trimers of the allophanate-modified diisocyanate.

3. The urethane (meth)acrylate as claimed in claim 1, wherein, in said monoalcohol A), n=1 and said monoalcohol A) is selected from the group consisting of: a) hydroxyalkyl (meth)acrylates, b) hydroxy polyether (meth)acrylates with Mn not exceeding 500, c) hydroxy polyester (meth)acrylates with Mn not exceeding 500, d) epoxy (meth)acrylates (bearing a secondary hydroxyl) and e) a mixture of at least one to two from among a), b), c) and d).

4. The urethane (meth)acrylate as claimed in claim 3, wherein said monoalcohol A) is option a).

5. The urethane (meth)acrylate as claimed in claim 1, wherein, in said monoalcohol A), n is at least two, and said monoalcohol A) is selected from: the group consisting of trimethylolpropane di(meth)acrylate, pentaerythrityl tri(meth)acrylate, ditrimethylolpropane ether tri(meth)acrylate, and dipentaerythrityl ether penta(meth)acrylate.

6. The urethane (meth)acrylate as claimed in claim 1, wherein said saturated polyol C) is selected from the group consisting of optionally alkoxylated C.sub.2 to C.sub.36 aliphatic and C.sub.6-C.sub.12 cycloaliphatic alkane dials, optionally alkoxylated C.sub.3 to C.sub.12 alkane triols, diol or triol or tetrol oligoethers with Mn not exceeding 500, and diol, triol or tetrol oligoesters with Mn not exceeding 500.

7. The urethane (meth)acrylate as claimed in claim 1, wherein said unsaturated polyol D) is selected from the group consisting of: trimethylolpropane mono(meth)acrylate, pentaerythrityl di(meth)acrylate, ditrimethylolpropane ether di(meth)acrylate, and dipentaerythrityl ether tetra(meth)acrylate.

8. The urethane (meth)acrylate as claimed in claim 1, and having a functionality of at least 2 (meth)acrylates per molecule.

9. The urethane (meth)acrylate as claimed in claim 1, wherein said monoalcohol forming the starting urethane in the preparation of said polyisocyanate B) is selected from the group consisting of linear monoalcohols and branched monoalcohols selected from the group consisting of at least one of: a′) C.sub.6 to C.sub.36 alkanols, b′) ether alcohol or oligoether alcohol with Mn not exceeding 500 and c′) ester alcohol or oligoester alcohol with Mn not exceeding 500.

10. The urethane (meth)acrylate as claimed in claim 1, wherein said polyisocyanate B) is a diisocyanate or trilsocyanate based on a starting isocyanate which is HMDI.

11. A process for preparing a urethane (meth)acrylate as claimed in claim 1, wherein the process comprises a step of reaction between said monoalcohol A) and said polyisocyanate B) in the optional presence of C) and/or D) and/or E).

12. A curable composition comprising at least one urethane (meth)acrylate as claimed in claim 1.

13. The curable composition as claimed in claim 12, wherein, in addition to said urethane (meth)acrylate, said at least one reactive diluent E) is present during the preparation of said urethane acrylate or added and/or adjusted after its preparation and/or another reactive diluent F).

14. The curable composition as claimed in claim 13, wherein said reactive diluent E) or said reactive diluent F) comprise (meth)acryl monomers with a functionality ranging from 1 to 6, selected from the group consisting of: optionally alkoxylated polyol (meth)acrylic esters, epoxy (meth)acrylates, urethane (meth)acrylates, aminoacrylates, and ether ester (meth)acrylates.

15. The curable composition as claimed in claim 12, wherein it is a composition that is curable by radiation, or by peroxide, or both.

16. The curable composition as claimed in claim 15, wherein the curable composition is curable by radiation selected from the group consisting of UV, laser, electron beam and LED.

17. The curable composition as claimed in claim 12, wherein the curable composition is a coating composition, selected from varnishes, inks, or adhesives.

18. The composition as claimed in claim 13 wherein the weight content of said urethane (meth)acrylate is at least 10% relative to the total weight of urethane (meth)acrylate and of said reactive diluent E) and/or F).

19. The composition as claimed in claim 13 wherein the weight content of said urethane (meth)acrylate is at least 30% relative to the total weight of the urethane (meth)acrylate and of said reactive diluent E) and/or F).

20. A cured coating wherein the cured coating results from at least one urethane (meth)acrylate as claimed in claim 1.

21. The coating as claimed in claim 20, wherein said coating is an ink for inkjet or flexography or screen printing application.

22. The urethane (meth)acrylate as claimed in claim 1, wherein the said polyol C) is present and is a C.sub.2 to C.sub.36 polyol with a functionality of 2.

23. The urethane (meth)acrylate as claimed in claim 1, wherein the said polyol D) is present and is a C.sub.6 to C.sub.18 diol.

Description

EXAMPLES

(1) The examples that follow are given as illustrations of the invention and of its performance qualities and do not in any way limit its scope.

(2) 1) Starting Materials Used (see Table 1)

(3) TABLE-US-00001 TABLE 1 starting materials used Function according Commercial Abbreviated to the name (REF) Chemical name name Supplier invention Functionality Tolonate ® Allophanate ADI Vencorex Polyisocyanate 2 XFlo100 Diisocyanate Desmodur ® W 4,4′-Dicyclohexyl- DesW BAYER Polyisocyanate 2 methanediyl diisocyanate Tolonate ® HDI Hexamethylene HDI Vencorex Polyisocyanate 2 Diisocyanate HEA HydroxyEthylAcrylate HEA BASF Hydroxyacrylate 1 SR495B Caprolactone CapA Sartomer Hydroxyacrylate 1 Acrylate TIB KAT216 DiOctylTin diLaurate DOTL TIB Catalyst BHT Bis-tert-butyl BHT Innochem Inhibitor HydroxyToluene
2) Preparation of Urethane Acrylate Products
Procedure for Examples 1 to 4

Example 1 (Invention)

(4) 743.2 g of ADI, 1.0 g of BHT and 0.7 g of DOTL are placed in a 1 liter reactor equipped with an anchor stirrer, an air inlet (air sparge) and a thermometer probe. The mixture is brought to 60° C. and 255.1 g of HEA are added over 1 hour while increasing the temperature uniformly to 90° C. The mixture is maintained at this temperature by regularly controlling the isocyanate number (INCO), until its value is less than 0.5 mg KOH/g. A product referenced UA-1 is obtained, having the following characteristics: Appearance: clear (visual) Color: 0.7 G (Gardner) Viscosity at 25° C.: 3.3 Pa.Math.s

Example 2 (Comparative)

(5) 278.0 g of DesW, 1.0 g of BHT and 0.7 g de DOTL are placed in a 1 liter reactor equipped with an anchor stirrer, an air inlet (air sparge) and a thermometer probe. The mixture is brought to 60° C. and 720.3 g of Cap A are added over 1 hour while increasing the temperature uniformly to 90° C. The mixture is maintained at this temperature by regularly controlling the isocyanate number (INCO), until its value is less than 0.5 mg KOH/g. A product referenced UA-2 is obtained, having the following characteristics: Appearance:clear Color:1.0 G Viscosity at 25° C.: 16.0 Pa.Math.s

Example 3 (Comparative)

(6) This example is performed in the same manner as Example 2, except that the polyisocyanate is ADI at 496.2 g and CapA at 502.1 g. A product referenced UA-3 is obtained, having the following characteristics: Appearance: clear Color: 0.9 G Viscosity at 25° C.: 3.0 Pa.Math.s

Example 4 (comparative)

(7) This example is performed like Example 2, with the following difference: polyisocyanante DesW at 531.4 g and HEA at 466.9 g.

(8) A product referenced UA-4 is thus obtained, having the following characteristics: Appearance: clear Color: 0.2 G Viscosity at 25° C.: not measurable (crystalline solid)
3) Evaluation of the Application Performance Qualities
3.1) Formulations Tested
3.1.1) Standard Evaluation of the Urethane Acrylate Products Alone

(9) The standard formulation used is as follows (weight %): 96% of urethane acrylate product according to Examples 1, 2 and 3, UA-1, UA-2 and UA-3, respectively 4% of photoinitiator Darocur® 1173.
3.1.2) Evaluation of the Products in a Varnish Formulation for Inkjet Application

(10) The standard formulation used is a varnish formulation as follows (weight %): 25% of urethane acrylate product according to Examples 1, 2 and 3, UA-1, UA-2 and UA-3, respectively 15% of SR595 (decane diol diacrylate sold by Sartomer) 30% of SR 508 (dipropylene glycol diacrylate or DPGDA) 25% of SR 217 (t-butyl cyclohexyl acrylate sold by Sartomer) 5% of photoinitiator Darocur® 1173.
3.2) Performance Test and Results
3.2.1) Tests and Methods Used
3.2.1.1) Determination of the Appearance

(11) The product is observed visually in daylight, through a 60 ml colorless glass bottle, to determine whether the product is: clear: no turbidity, it is comparable to water, turbid: no longer allowing clear vision through the bottle, cloudy: opaque bottle, no image can be seen through the bottle.
3.2.1.2) Determination of the Brookfield Viscosity

(12) The viscous resistance of the liquid to be characterized is measured via the torsion of the spring associated with the rotor immersed in the liquid at a given shear rate. The dimensions and shape of the rotor, the container in which the rotor rotates, the spin speed of the rotor and the torsion torque of the calibrated spring are chosen so that the measurable viscosity interval contains the product to be tested.

(13) 3.2.1.3) Determination of the Reactivity

(14) The formulation as described generally above is applied as a 12 μm film to a contrast card (Leneta Penoparc charts form 1B®) and is then cured using a Fusion Hg 120 W/cm lamp. The minimum passage speed (in m/min) required to obtain a touch-dry film is measured.

(15) 3.2.1.4) For the following hardness, flexibility and acetone resistance tests, the photocured films are left in an air-conditioned room (T=23° C.) for 24 hours after curing and before the measurements.

(16) 3.2.1.4.1) Determination of the Persoz Hardness

(17) The formulation to be examined is applied as a 100 μm film to a glass plate and cured with a Fusion Hg 120 W/cm lamp at a speed of 10 m/min.

(18) The number of oscillations before damping of the oscillations (passage from 12° to 4° amplitude) of a pendulum in contact with the coated glass plate is measured according to standard ISO 1522.

(19) 3.2.1.4.2) Pencil hardness: tested by the presence or absence of scratches on the cured film (100 μm) with pencils of increasing hardness ranging from 6B to 6H.

(20) 3.2.1.4.3) Determination of the Flexibility

(21) The formulation is applied as a 100 μm film to a smooth steel plate 25/10 mm thick (D-46® Q-Panel), and then cured with a Fusion Hg 120 W/cm lamp at a speed of 10 m/min.

(22) The coated plate is curved on cylindrical mandrels according to standard ISO 1519. The result is expressed as the value (in mm) of the smallest radius of curvature that can be inflicted on the coating without it cracking or detaching from the support.

(23) 3.2.1.4.4) Determination of the Acetone Resistance

(24) The formulation is applied as a 12 μm film to a glass plate and then cured with a Fusion Hg 120 W/cm lamp at a speed of 10 m/min. The coating is rubbed with a cloth soaked with acetone. The result is the time (expressed in seconds) beyond which the film detaches and/or disintegrates.

(25) 3.2.1.4.5) Determination of the Elongation at Break

(26) The formulation is applied as a 120 μm film between two silicone-treated PET (polyethylene terephthalate) films, and then partially cured with a Fusion Hg 120 W/cm lamp at a speed of about 40 m/min. Dumbbell-shaped specimens 5 mm wide, with a working length of 25 mm and 120 μm thick are cut out using a punch according to standard ISO 527 3. Complete curing of these specimens is performed with the same lamp by means of 5 passages at 5 m/min.

(27) A traction test is performed at room temperature and at a constant speed of displacement (10 mm/min) on an Instron® 5564 machine. The stress as a function of the strain of the specimen is recorded.

(28) 3.2.1.4.6) Determination of the Adhesion

(29) The varnish formulation for inkjet application is applied as 6 μm films onto various types of plastic supports (ABS, PC (polycarbonate), PET, PVC) and then cured with a Fusion Hg 120 W/cm lamp at a speed of 10 m/min. Two series of incisions of 10 perpendicular lines are made, thus producing a 100-square checkerboard, and an adhesive tape of given adhesion force is then stripped off. The number of squares stripped off out of the 100 as described above is then counted, according to standard ISO 2409. The result is reported numerically on a scale from 0 to 5, 0 corresponding to the stripping of all 100 squares, and 5 corresponding to no stripping.

(30) 3.2.2) Results by Performance

(31) 3.2.2.1 ) Standard Evaluation of the Urethane Acrylate Products Alone

(32) TABLE-US-00002 Persoz Acetone UA product Reactivity hardness Flexibility resistance tested alone (m/min) (cycles) (mm) (s) Adhesion UA-1 5 35 3 80 2 UA-2 3 * 5 41 3 146 4
3.2.2.2) Compared Evaluation of Varnish Formulations for Inkjet Application

(33) TABLE-US-00003 UA product Acetone Elongation of tested Flexibility resistance at break Young's formulation (mm) (s) Adhesion (%) modulus UA-1 8 28 4 10 600 UA-2 6 25 4 4 500

(34) The performance levels in terms of acetone resistance and adhesion are equilibrated in the formulated systems (varnish for inkjet application) relative to the urethane acrylate products evaluated alone. The percentage of elongation at break is significantly higher for UA-1 (150% increase) with similar Young's modulus values. This means that the cohesive energy of the formulation according to the invention is significantly higher than that of the representative formulation of the prior art.

(35) The same tests were performed on compared formulations having the same viscosity of 40 mPa.Math.s corresponding to 37% by weight for UA-1 and for UA-2 maintained at 25% by weight.

(36) The results are as follows:

(37) TABLE-US-00004 UA product Acetone Elongation of tested Flexibility resistance at break formulation (mm) (s) Adhesion (%) 37% UA-1 6 42 4 13 UA-2 6 25 4 4

(38) The 50% increase in the content of UA-1 in the varnish formulation for inkjet application brings about an increase in the performance qualities in terms of flexibility and elongation at break relative to the initial composition containing 25% UA-1. This confirms the greater toughness of the urethane acrylate product according to the invention relative to that of the prior art.