RADIATION CURING COATING COMPOSITION

Abstract

Disclosed is a UV-curing coating composition comprising (a) 40-70% by weight of at least one urethane (meth)acrylate being a product of a reaction between at least one polycaprolactone polyol (a1) and at least one adduct (a2), said adduct (a2) being a product of a reaction between at least one polyisocyanate (a3) and at least one hydroxyalkyl (meth)acrylate (a4), said polycaprolactone polyol (a1) being a product of a reaction between at least one polyalkoxylated polyol (a5) and at least one caprolactone monomer (a6), (b) 20-50% by weight of at least one reactive diluent having at least one olefinic carbon-carbon double bond, and (c) 0.5-10% by weight of at least one photoinitiator, and optionally (d) 1-15% by weight of at least one matting agent.

Claims

1. A coating composition characterised in, that said coating composition is a UV-curing coating composition comprising (a) 40-70% by weight of at least one urethane (meth)acrylate being a product of a reaction between at least one polycaprolactone polyol (a1) and at least one adduct (a2), said adduct (a2) being a product of a reaction between at least one polyisocyanate (a3) and at least one hydroxyalkyl (meth)acrylate (a4), whereby said polycaprolactone polyol (a1) is a product of a reaction between at least one polyalkoxylated polyol (a5) and at least one caprolactone monomer (a6), (b) 20-50% by weight of at least one reactive diluent having at least one olefinic carbon-carbon double bond, and (c) 0.5-10% by weight of at least one photoinitiator.

2. The coating composition according to claim 1 characterised in, that it additionally comprises (d) 1-15% by weight, calculated on subtotal of said components (a) to (c), of at least one matting agent.

3. The coating composition according to claim 2 characterised in, that said matting agent (d) is a haptic matting agent.

4. The coating composition according to claim 2 characterised in, that said matting agent (d) is a polyamide, a micronised biopolymer, a synthetic amorphous and optionally surface treated silica, a corpuscular crypto-cristalline amorphous silica, lamellar kaolin and/or an inorganically modified polyethylene wax dispersion.

5. The coating composition according to claim 1 characterised in, that said polycaprolactone polyol (a1) has 2-10 caprolactone units/molecule.

6. The coating composition according to claim 1 characterised in, that said polycaprolactone polyol (a1) has a glass transition temperature (Tg) of less than −40° C.

7. The coating composition according claim 1 characterised in, that said polycaprolactone polyol (a1) has a molecular weight (Mw) of 1000-6000 g/mol.

8. The coating composition according to claim 1 characterised in, that said adduct (a2) is obtained at a molar ratio polyisocyanate (a3) to hydroxyalkyl (meth)acrylate (a4) of between 1 to 0.8 and 1 to 1.

9. The coating composition according to claim 1 characterised in, that said polyisocyanate (a3) is an aliphatic or cycloaliphatic di or triisocyanate and/or a a NCO-functional dimer, trimer or polymer thereof or therewith.

10. The coating composition according to claim 1 characterised in, that said polyisocyanate (a3) is hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexyl methane diisocyanate, tetrahydrofuran diisocyanate, cyclohexylene diisocyanate and/or nonane triisocyanate, and/or a NCO-functional dimer, trimer or polymer thereof or therewith.

11. The coating composition according to claim 1 characterised in, that said hydroxyalkyl (meth)acrylate (a4) is hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, trimethylolethane di(meth)acrylate, trimethylolpropane di(meth)acrylate, trimethylolbutane di(meth)acrylate and/or pentaerythritol tri(meth)acrylate.

12. The coating composition according to claim 1 characterised in, that said polyalkoxylated polyol (a5) is a polyethoxylated, polypropoxylated and/or polybutoxylated diol or triol having 1-30 ethoxy, propoxy and/or butoxy units/molecule.

13. The coating composition according to claim 1 characterised in, that said polyalkoxylated polyol (a5) is a polyethoxylated and/or polypropoxylated neopentyl glycol, glycerol, trimethylolethane, trimethylolpropane or trimethylolbutane.

14. The coating composition according to claim 1 characterised in, that said caprolactone monomer (a6) is ε-caprolactone.

15. The coating composition according to claim 1 characterised in, that said reactive diluent (b) is at least one alkyl (meth)acrylate, vinyl (meth)acrylate, (meth)allyl (meth)acrylate, polyester (meth)acrylate, epoxy (meth)acrylate, urethane (meth)acrylate and/or melamine (meth)acrylate.

16. The coating composition according to claim 1 characterised in, that said reactive diluent (b) is isobornyl (meth)acrylate, dipropylene glycol di(meth)acrylate, tripropyleneglycol di(meth)acrylate, hexanediol di(meth)acrylate and/or trimethylolpropane tri(meth)acrylate.

17. The coating composition according to claim 1 characterised in, that said photoinitiator (c) is a benzoin ether, an acylphosphine, an acetophenone, an aminoalkyl phenone, a benzophenone and/or an antraquinone.

18. The coating composition according to claim 1 characterised in, that it additionally comprises at least one pigment, filler and/or dye.

19. The coating composition according to claim 1 characterised in, that it additionally comprises at least one UV-stabiliser, flow/levelling agent, rheological agent, inhibitor and/or UV-absorber.

20. (canceled)

21. (canceled)

22. A method for obtaining a decorative and/or protective topcoat comprising applying a coating composition of claim 1 to a substrate.

Description

EXAMPLE 1

[0015] Polycaprolactone polyols were produced by subjecting ε-caprolactone to reaction (ring opening and condensation) with either one of the alkoxylated trimethylolpropanes Polyol 3165™, Polyol 3380™ (Perstorp AB, Sweden) or with the propoxylated neopentyl glycol Polyol R2490™ (Perstorp AB, Sweden), having following properties:

TABLE-US-00001 Polyol 3165 3380 R2490 Hydroxyl functionality  3 3 2 Hydroxyl value (mg KOH/g) 165 ± 25 380 ± 25 485 ± 25 Molecular weight (g/mol) 1 010   440 220  Ethoxy units/molecule 20 7 — Propoxy units/molecule — 2

[0016] at molar ratios yielding polycaprolactone polyols having following properties:

TABLE-US-00002 Caprolactone polyol 1 2 3 4 5 Caprolactone units/molecule  .sup. 2.6  .sup. 5.2  .sup. 3.9 .sup.  6.1  .sup. 6.8 Calc. molecular weight (g/mol) 2 010.sup.  3 022.sup.  1 957.sup.  2 826   1 993.sup.  Acid value (mg KOH/g)    0.10    0.09    0.09    0.06    0.14 Hydroxyl number (mg KOH/g)  84  56  86 60  56 Colour (Hazen) 287 157 117 45 162 Viscosity at 60° C. (mPas) 214 429 296 620  450 Tg - DSC (° C.) −67 −64 −65 −63   −66 Melting point (° C.)  31  37  34 41  45

[0017] The reactions were performed at 180-190° C. in presence of a tin carboxylate as catalyst and monitored by GC determination of residual ε-caprolactone. The reactions were terminated when the amount of residual ε-caprolactone was close to zero.

EXAMPLE 2

[0018] An adduct between isophorone diisocyanate and 2-hydroxyethyl acrylate was produced, at 65-70° C. using 4-methoxyphenol as inhibitor and dibutyltin laurate as catalyst, at a molar ratio said diisocyanate to said acrylate of 1.0 to 0.95.

EXAMPLE 3

[0019] Urethane acrylates were produced by reacting a polycaprolactone polyol obtained in Example 1 and the adduct obtained in Example 2 at a molar ratio hydroxyl groups to isocyanate groups of 1.0 to 0.9. The reaction was performed at 60° C. using butylated hydroxytoluene as inhibitor, dibutyltin laurate as catalyst and toluene as solvent. The reaction was monitored by analysing the NCO-content and stopped when the NCO-value was close to zero. Products having following properties were yielded:

TABLE-US-00003 Urethane acrylate A B C D E Used polycaprolactone polyol 1  2 3  4 5 Calc. molecular weight (g/mol) 10 600    16 500    10 800    15 200    10 600    C═C concentration (meq/g)   1.07    0.81   1.07    0.82   0.66 Viscosity at 25° C. (Pas) 260  320  470  450  Solid Viscosity at 70° C. (Pas) 7 11 9 11 7 Tg by DSC (° C.) −39    −48   −35    −46   −50    C═C concentration: Determined using FTIR spectroscopy. Tg (glass transition temperature) by DSC: Determined on a Mettler DSC. 10 mg sample was analysed in a 40 μL aluminium pan. Temperature range from −100 to +120° C. Ramp 10° C./min.

EXAMPLE 4

[0020] UV-curing coatings were prepared by mixing 44.8 parts by weight of urethane acrylate A, B, C or D obtained in Example 3, 49.7 parts by weight of tripropylene glycol diacrylate as reactive diluent and 5.5 parts by weight of Irgacure® 1173 (BASF AG) as photoinitiator. Obtained coatings were coated on glass and aluminium panels using a K-bar yielding a wet film having a thickness of 30-40 μm. Curing was performed under a H vapour lamp (Fusion F600 max. 240 W/cm) at a UV dose of 5-6 J/cm.sup.2. The cured films exhibited following properties:

TABLE-US-00004 Coating I II III IV Used urethane acrylate A B C D Hardness (König secs) 43 38 43 42 Erichsen flexibility 4.8 4.3 4.5 3.8 (mm) Acetone spot test No No No No (2 min.) marking marking marking marking MEK double rubs 23 15 41 26 Tg by DMA (° C. −31 −44 −25 −31 max E″) MEK (methyl ethyl ketone) double rubs: Evaluation according to ASTM D4752. Acetone spot test: Evaluation according to SS 83 91 18. Tg by DMA (° C. max E″): Determined using a Mettler DMA, in tension mode, at a temperature range from −100 to 150° C. (ramp 3° C./min). Amplitude and frequency respectively equal to 15 μm and 1 Hz. Three specimens of each sample were tested and the average value was reported.

EXAMPLE 5

[0021] UV-curing coatings were prepared by mixing either 44.8 parts by weight of urethane acrylate C, obtained in Example 3, or 44.8 parts by weight of a urethane acrylate wherein the polyalkoxylated trimethylolpropane (Polyol 3380™) used in the polycaprolactone polyol was replaced by non-alkoxylated trimethylolpropane, 49.7 parts by weight of dipropylene glycol diacrylate as reactive diluent and 5.5 parts by weight of Irgacure® 1173 (BASF AG) as photoinitiator. Obtained coatings were coated on glass and aluminium panels and cured as in Example 4. The cured films exhibited following properties:

TABLE-US-00005 V VI Coating Embodiment Comparative Viscosity at 23° C. (Pas) 0.9 2.7 Hardness (König secs) 68 84 Acetone spot test (2 min.) No marking No marking MEK double rubs 55 83 Tg by DMA (° C. max E″) −25 19 E′ by DMA at 130° C. (Mpa) 42 40 Mc (g/mol) 270 275 MEK (methyl ethyl ketone) double rubs: Evaluation according to ASTM D4752. Acetone spot test: Evaluation according to SS 839118. Tg (° C. max E″) and E′ by DMA: Determined using a Mettler DMA, in tension mode, under a temperature range from −100 to 150° C. (ramp of 3° C./min). Amplitude and frequency respectively equal to 15 μm and 1 Hz. Three specimens of each sample were tested and the average value was reported. Mc ∝ (3ρRT)/E′ wherein E′ is the storage modulus on the rubbery plateau (J .Math. m.sup.−3), ρ is the material density (kg .Math. m.sup.3) at T, R is the gas constant (8,314 J .Math. mol.sup.−1 .Math. K.sup.−1) and T the temperature at the rubbery plateau (K).

EXAMPLE 6

[0022] UV-curing coatings were prepared by mixing 44.8 parts by weight of either urethane acrylate A or C or 44.8 parts by weight of a 60/40 (by weight) mixture of urethane acrylates C and E, obtained in Example 3, 49.7 parts by weight of dipropylene glycol diacrylate as reactive diluent and 5.5 parts by weight of Irgacure° 1173 (BASF AG) as photoinitiator. Deuteron® UV RS20 (inorganically modified polyethylene wax dispersion, Deuteron GmbH) or Orgasol® 2001 UD NATI (polyamide 12, Arkema, France) was as matting agent and added to obtained compositions in an amount of 10% by weight calculated on said compositions. Obtained coatings were coated on glass and aluminium panels as in Example 4. The cured films exhibited following properties:

TABLE-US-00006 Coating VII-M VIII-M IX-M X-M Used urethane A C C + E C + E acrylate Matting agent Deuteron Deuteron Deuteron Orgasol Hardness (König secs) 65 63 77 55 Erichsen flexibility   4.0   3.5   4.4   4.4 (mm) Acetone spot test No No No No (2 min.) marking marking marking marking MEK Double rubs 42 60 56 130  Surface feeling Soft/ Soft/ Soft/ Soft/ haptic haptic haptic haptic MEK (methyl ethyl ketone) double rubs: Evaluation according to ASTM D4752. Acetone spot test: Evaluation according to SS 839118.