Polyacrylate allophanate

Abstract

The invention relates to a modified allophanate compound bearing acrylate functions, resulting from the reaction of a particular allophanate with an ester from the reaction between an acid selected from acrylic acid and methacrylic acid and at least one polyol that does not contain an oxylakylene or aa (poly)oxyalkylene group. The invention further relates to the use of said modified allophanate for preparing a hydrophobic cross-linkable coating composition by means of UV radiation.

Claims

1. A hydrophobic modified allophanate, prepared according to a method consisting of (a) providing; an allophanate of formula (I) ##STR00006## wherein R.sup.1 is the radical of a monoalcohol compound selected from the group consisting of the compound CAS RN 68213-23-0, the compound CAS RN 68154-96-1 and the compound CAS RN 68439-49-6 which is used alone or in mixtures and comprises an ether or polyether function after reaction of the hydrogen of the OH function of the monoalcohol with a compound with an isocyanate function; R.sup.2 and R.sup.3, either identical or different, are an aliphatic hydrocarbon group comprising a derivatized or non-derivatized isocyanate function; and then (b) reacting the allophanate with at least one ester, wherein the ester: being hydroxy-functionalized; comprising at least one acrylate function; and being prepared by reacting an acid selected from the group consisting of acrylic acid and methacrylic acid with at least one alcohol.

2. The hydrophobic modified allophanate according to claim 1, wherein the molar ratio of the urethane/allophanate functions (NCO functionality) is equal to 2.

3. The hydrophobic modified allophanate according to claim 1, wherein the allophanate of formula (I) has an NCO functionality selected from the group consisting of an NCO functionality ranging from 1.9 to 2.3: an NCO functionality ranging from 1.9 to 2.2: an NCO functionality ranging from 1.9 to 2.1; an NCO functionality ranging from 2 to 2.3; and an NCO functionality ranging from 2 to 2.2.

4. The hydrophobic modified allophanate according to claim 1 wherein the allophanate of formula (I) is a homo-allophanate, R.sup.2 and R.sup.3 being identical, or wherein the allophanate of formula (I) is a mixed allophanate, R.sup.2 and R.sup.3 being different.

5. The hydrophobic modified allophanate according to claim 1 wherein the allophanate of formula (I) is selected from the group consisting of bis-allophanate and tris-allophanate.

6. The hydrophobic modified allophanate according to claim 1, wherein the allophanate of formula (I) is prepared from hexamethylene diisocyanate (HDI) or isophorone diisocyanate (IPDI).

7. The hydrophobic modified allophanate according to claim 1 wherein the allophanate of formula (I) is prepared from at least one other polyfunctional isocyanate.

8. The hydrophobic modified allophanate according to claim 1, wherein the allophanate of formula (I) is prepared from at least one other polyfunctional isocyanate tricondensate.

9. The hydrophobic modified allophanate according to claim 1, wherein the allophanate of formula (I) is prepared from at least one other polyfunctional isocyanate tricondensate, in a proportion of less than 10% by mass; in a proportion of less than 8% by mass based on the allophanate of formula (I); in a proportion of less than 6% by mass based on the allophanate of formula (I); or in a proportion of less than 2% by mass based on a mixture in preparation of the allophanate of formula (I).

10. The hydrophobic modified allophanate according to claim 1, wherein step (b) is carried out with at least one monohydroxy-functionalized ester.

11. The hydrophobic modified allophanate according to claim 1, wherein step (b) is carried out with a single ester or with two esters.

12. The hydrophobic modified allophanate according to claim 1, wherein step (b) is carried out with at least one alcohol not comprising any oxyalkylene or (poly)oxyalkylene group.

13. The hydrophobic modified allophanate according to claim 1, wherein step (b) applies an ester prepared from an alcohol selected from the compounds of formula (III) ##STR00007## wherein p is 1, 2, 3, 4 or 5; L.sup.1 is a linear or branched hydrocarbon radical, or a linear or branched radical comprising a hydrocarbon chain and at least one heteroatom; L.sup.2 is O, S or a group of formula NT wherein T is H or a linear or branched C.sub.1-C.sub.8-alkyl group and N represents a nitrogen atom; R, either identical or different, is H or a linear or branched C.sub.1-C.sub.8-alkyl group; q is 1, 2, 3, 4 or 5.

14. The hydrophobic modified allophanate according to claim 1, wherein the at least one ester is selected from the group consisting of 2-hydroxyalkyl(meth)acrylates, 2-hydroxyethyl(meth)acrylate, 2-hydroxy propyl(meth)acrylate, 3-hydroxypropyl-(meth)acrylate, 4-hydroxybutyl(meth)acrylate, 3-hydroxy-2,2-dimethylpropyl-(meth)acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, a caprolactone modified by esterification with hydroxyalkyl(meth)acrylates, an -caprolactone modified by esterification with hydroxyalkyl(meth)acrylates, an -caprolactone modified by esterification with hydroxyalkylacrylates, an -caprolactone modified by esterification with 2-hydroxyalkyl(meth)acrylates, an -caprolactone modified by esterification with 2-hydroxyalkylacrylates caprolactone triacrylate, glycerol di(meth)acrylate, trimethylolpropane di(meth)acrylate, pentaerythritol tri(meth)acrylate (PETIA), di(pentaerythritol) penta(meth)acrylate, and trimethylolpropane diacrylate.

15. The hydrophobic modified allophanate according to claim 1, wherein the reaction (b) is carried out with at least one ester selected from the group consisting of pentaerythritol triacrylate (PETIA), dipentaerythritol pentaacrylate (DPHA), and trimethylolpropane diacrylate.

16. A of preparation of a coating composition, the method consisting of preparing the modified allophanate according to claim 1 by reacting the allophanate in (a) with the ester in (b).

17. A method of preparation of a hydrophobic coating composition, the method consisting of preparing the modified allophanate of claim 1 by reacting the allophanate in (a) with the ester in (b).

18. The method of preparation according to claim 16 wherein the coating composition is a cross-linkable coating composition.

19. The method of preparation according to claim 16 wherein the coating composition is a coating composition which is cross-linkable by UV irradiation.

20. The method of preparation according to claim 17 wherein the hydrophobic coating composition is a cross-linkable hydrophobic coating composition.

21. The method of preparation according to claim 17 wherein the hydrophobic coating composition is a hydrophobic coating composition which is cross-linkable by UV irradiation.

Description

EXAMPLES

(1) The following products are used.

(2) HDI: hexamethyldiisocyanateVencorex

(3) Tolonate HDB: hexamethylenediisocyanate biuretVencorex NCO equivalent weight=191 g Viscosity=9,000 mPa.Math.s Dry extract=100%

(4) Tolonate IDT 70 B: a trimer of isophorone diisocyanateVencorex NCO equivalent weight=342 g Viscosity=600 mPa.Math.s Dry extract=70%

(5) (Pentaerythritol)tri-acrylate: reaction product of acrylic acid and pentaerythritol Content of OH groups=149 mg KOH/g.

(6) Hexanediol diacrylate (HDDA): an acrylated reactive diluentSartomer

(7) An ethoxylated C.sub.12-C.sub.18 alcohol with OH content equal to 170 mg KOH/g (RNCAS=68213-23-0)

(8) Catalyst K KAT XK-629: a 20% solution in bismuth tris(2-ethylhexanoate) 2-ethylhexanol.

Example 1: Preparation of an Allophanate of Formula (I)

(9) In a perfectly stirred jacketed reactor, we introduce:

(10) 425 g of HDI (2.53 mol) and then 82 g of an ethoxylated C.sub.12-C.sub.18 alcohol (0.23 mol) preheated to 40 C.+1.45 g of a butanol-1/butanol-2 mixture (75/25 as a mass ratio m/m) and 5.85 g of catalyst K KAT XK-629 at room temperature. The medium is heated in order to attain the temperature of 110 C. in 2 hours. The reaction medium is held at this temperature for about 1.5 hours.

(11) The NCO content of the reaction medium is regularly measured by a return dibutylamine assay method.

(12) The reaction is stopped by adding 0.066 g of para-toluene sulfonic acid when the NCO content of the reaction medium corresponds to the expected theoretical content.

(13) After 15 minutes, the temperature of the reaction medium is brought back to room temperature.

(14) The NCO content of the final reaction medium is 0.829 mol of NCO for 100 g.

(15) It is then proceeded with 2 successive distillations on a thin film evaporator in vacuo (about 0.5 mbars) at a temperature of 130 C. for removing most of the monomer which has not reacted.

(16) The obtained amount after distillation is 192 g. This corresponds to a yield of the order of 40%.

(17) The final allophanate of formula (I) is characterized by the following data:

(18) NCO content: 0.30 mol of NCO for 100 g, i.e. a weight percent of 12.6%;

(19) viscosity measured at 25 C.: 138 mPa.Math.s.

Example 2: Preparation of a Modified Allophanate According to the Invention

(20) In a three-neck flask equipped with a cooling system, with a mechanical stirrer and with a nitrogen supply, 80 g (0.205 mol) of (pentaerythritol)tri-acrylate (PETIA), 0.02 g of dibutyltin dilaurate (DBTL), 0.072 g of butylhydroxytoluene (BHT) and 100 g of dry toluene are introduced.

(21) 61.4 g of allophanate (0.185 mol) of formula (I) of Example 1 is then added with stirring and dropwise and the reaction medium is then heated up to a temperature of 60 C.

(22) The reaction is stopped after 7 h when the NCO groups have entirely reacted and the reaction medium is left to return to room temperature.

(23) The solvent is then evaporated in vacuo.

Comparative Examples 3 to 5

(24) The same synthesis procedure is repeated by using as a comparison the polyisocyanates according to Table 1.

(25) TABLE-US-00001 TABLE 1 Compar- isocy- tol- ative Initial anate PETIA uene DBTL Reaction Example isocyanate (g) (g) (g) (g) time 3 Tolonate 63 80 100 0.02 >24 h IDT 70 B 4 Tolonate 35.2 80 1400 0.02 7 h 30 mins HDB 5 HDI 14.2 80.3 80 0.02 7 h

(26) The characteristics of the obtained products are shown in table 2.

(27) TABLE-US-00002 TABLE 2 Dry Mn Content of ex- (g/mol) Exam- Initial OH groups tract Mw Viscosity ple isocyanate (mg KOH/g) (%) (g/mol) (Pa .Math. s) 2 Allophanate 41 97.6 1100 17.1 to 23 C. of Example 1 1200 3 Tolonate 13 56.1 1300 .sup.20 to 50 C. IDT 70 B 3100 4 Tolonate HDB 17 63.9 1400 .sup.78 to 50 C. 5800 5 HDI 56 97.9 800 24.3 to 23 C. 1100

(28) The use of the allophanate of Example 1 as an initial reagent gives the possibility of obtaining products with lower viscosity both as compared with isocyanates (HDI) and with known polyisocyanates like the products Tolonate IDT 70 B or Tolonate HDB (Table 2).

Examples 6 to 8: Producing Coatings from Products of Examples 2, 3, 4

(29) The products of Examples 2, 3 and 4 were used for producing a coating which is crosslinkable under UV light under the conditions shown in table 3.

(30) The formulations based on urethane acrylates are adjusted to 50% of dry extract with acetone and 4% of a photoinitiator (Irgacure 500) is then added.

(31) The application is carried out on polycarbonate plates with a K-bar of 12 m. After evaporation of the solvents (30 minutes at 60 C. in an oven), the plates are stored for 24 h under constant temperature and humidity conditions (50% RH, 23 C.). The thickness of the coating is then 6 m.

(32) The plates are then cross-linked under UV radiation (mercury lamp) under the conditions shown in Table 3.

(33) TABLE-US-00003 TABLE 3 UV-C Dose UV-B Dose UV-A Dose UV-V Dose Running speed J/cm.sup.2 J/cm.sup.2 J/cm.sup.2 J/cm.sup.2 3 5 m/min 0.213 1.41 2.148 1.917

(34) The evaluation of the following properties is carried out 24 h after cross-linking.

(35) Glossiness

(36) It is measured according to an angle of 20 initially and after 50 round-trips with the glass wool ballasted with a weight of 385 g so as to evaluate damage of the surface due to friction.

(37) Contact Angle

(38) The measurement of the angle formed by a drop of water in contact with the coating is an indication of hydrophobicity of the coating. The higher the angle, the more hydrophobic is the surface.

(39) Pencil Hardness

(40) The coating is scratched with graphite leads of increasing hardness according to the scale of FIG. 1.

(41) TABLE-US-00004 TABLE 4 Contact Glossiness Product Pencil angle Initial (20) (initial hard- with glossiness after 50 Example isocyanate) ness water (20) rubs 6 Example 2 (The 5H-6H 73 90 88 allophanate of Example 1) 7 Example 3 3H-4H 65 90 86 (Tolonate IDT 70 B) 8 Example 4 3H-4H 50 76 89 (Tolonate HDB)

(42) The retained hardness is the one for which there was no mark on the coating.

(43) The obtained results show that the application of the allophanate of formula (I) according to Example 1 during the preparation and the application of a modified allophanate according to the invention gives the possibility of obtaining hydrophobic and scratch-resistant coatings.

Examples 9 to 10: Producing Coatings from Products of Examples 2 and 5

(44) The products of Examples 2 and 5 are formulated according to Table 5.

(45) TABLE-US-00005 TABLE 5 Product (initial isocyanate) Example 9 Example 10 Example 5 (HDI) 10 Example 2 (Allophanate of Example 1) 10 Hexanediol diacrylate (HDDA) 2.5 2.5 Irgacure 500 0.25 0.25

(46) These formulations were then applied on the glass or steel plates according to the test with a K-bar. The dry thickness is 35 m.

(47) UV irradiation is carried out by means of a mercury lamp according to the conditions of Table 6.

(48) TABLE-US-00006 TABLE 6 Running rate Total UV dose 2 5 m/min 1234 mW/cm.sup.2

(49) The formulation comprising the product of Example 2 (stemming from the allophanate of Example 1) has the same hardness and aspect characteristics as the Comparative Example but has superior flexibility during the Erichsen indentation test (ISO 1520-1999) (Table 7).

(50) TABLE-US-00007 TABLE 7 Example 10 Example 9 Example 2 Example 5 (Allophanate of Product (HDI) Example 1) Flexibility - Erichsen 0.3 1.4 indentation (mm) Glossiness (20 C.) 82 85 MEK resistance (double rubs) >250 >250 Pencil hardness 9H 9H