POLYURETHANE COATING WITH A HIGH BIOSOURCED MONOMER CONTENT, COMPRISING ISOSORBIDE AND PENTAMETHYLENE DIISOCYANATE

Abstract

The present invention relates to a crosslinkable composition for forming a polyurethane coating on different types of substrates. The present invention relates in particular to a polyurethane composition with a high biosourced monomer content, comprising isosorbide as a diol chain extender and a pentamethylene diisocyanate trimer; the invention also relates to the polyurethane coating obtained from this composition.

Claims

1. A crosslinkable polyurethane coating composition comprising: a polyol fraction comprising a polyol chosen from a polyester polyol, a polyether polyol, a polycarbonate polyol or a mixture thereof, said polyol being a diol or a mixture of diols; a polyisocyanate fraction comprising a pentamethylene diisocyanate trimer; isosorbide.

2. The composition as claimed in claim 1, wherein the polyurethane coating obtained by crosslinking the composition has a single glass transition temperature Tg, said Tg being greater than or equal to 20 C., preferably greater than or equal to 25 C., more preferentially greater than or equal to 30 C.

3. The composition as claimed in claim 1, wherein the molar ratio of all the OH functions of the polyol fraction and of the isosorbide to all of the NCO functions of the polyisocyanate fraction is between 0.8 and 1.2, preferably between 0.95 and 1.05.

4. The composition as claimed in claim 1, wherein the molar ratio of all the OH functions of the polyol fraction to all the OH functions of the isosorbide is between 0.2 and 2; preferably between 0.3 and 1, more preferentially between 0.4 and 0.6.

5. The composition as claimed in claim 1, wherein the polyol has a molecular weight of between 400 and 4000 g/mol, preferably between 500 and 2000 g/mol and more preferentially between 600 and 1500 g/mol.

6. The composition as claimed in claim 1, wherein the polyol is chosen from a polyethylene glycol (PEG), a polypropylene glycol (PPG), a polytetramethylene ether glycol (PTMEG), a poly(caprolactone) diol, or a mixture thereof; preferably a PTMEG; more preferentially a PTMEG having a molecular weight of 400 to 2000 g/mol.

7. The composition as claimed in claim 1, wherein the polyol fraction also comprises a triol.

8. The composition as claimed in claim 1, wherein the polyisocyanate fraction also comprises an aliphatic diisocyanate, preferably chosen from pentamethylene diisocyanate (PMDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), methylene dicyclohexyl diisocyanate (HMDI or hydrogenated MDI), or a mixture thereof; more preferentially IPDI.

9. The composition as claimed in claim 1, wherein the polyisocyanate fraction comprises at least 5 mol % relative to the NCO functions, in particular at least 10 mol % relative to the NCO functions, more particularly at least 15 mol % relative to the NCO functions, of pentamethylene diisocyanate trimer.

10. The composition as claimed in claim 1, wherein the polyisocyanate fraction comprises: 1 to 40 mol %, preferably 2 to 30 mol %, relative to the NCO functions of pentamethylene diisocyanate trimer; and 60 to 99 mol %, preferably 70 to 98 mol %, relative to the NCO functions of aliphatic diisocyanate.

11. A process for producing a polyurethane coating on a substrate, comprising the following steps: depositing on the substrate a layer of the composition as claimed in claim 1, then crosslinking the composition.

12. A polyurethane coating which can be obtained by means of the process as defined in claim 11.

Description

EXAMPLES

A. Preparation of Crosslinkable Compositions in Accordance (EX) or Not in Accordance With the Invention (CEX)

[0092] The following products were used in the examples: [0093] polyol: poly(tetramethylene glycol) of molecular weight 650 g/mol (PTMEG 650) or 1000 g/mol (PTMEG 1000) (Sigma-Aldrich) [0094] polyisocyanate: pentamethylene diisocyanate trimer (t-PMDI) (Covestro) [0095] diisocyanate: isophorone diisocyanate (IPDI) (Aldrich) [0096] chain-extender diol: isosorbide (Roquette) or 1,4-butanediol (BDO) (Sigma Aldrich) [0097] solvent: 2-butanone and dimethyl isosorbide (Roquette) [0098] additive: polyether-modified polydimethylsiloxane (BYK 307) (BYK) [0099] catalyst: dibutyltin dilaurate (DBTDL) (Sigma Aldrich)

[0100] Various compositions were prepared by mixing the monomers indicated in the table below with a (OH polyol)/(NCO polyisocyanate+diisocyanate)/(OH chain extender) stoichiometry of 1/3.05/2. The monomers (that is to say the polyol, the diisocyanate, the polyisocyanate and the chain extender) are introduced into a solvent mixture comprising 2-butanone and dimethyl isosorbide (volume ratio 1:5) to obtain a concentration of 70% by weight of the monomers relative to the weight of the composition. The BYK 307 additive is added, to reduce the crater effects, at a percentage of 0.1% by weight relative to the weight of the monomers. The DBTDL catalyst is added at a percentage of 0.025% by weight relative to the weight of the monomers in order to accelerate the reaction (except for the CEX1 formulation which gelled before application).

TABLE-US-00001 MONOMERS Diisocyanate Polyisocyanate Chain- (mol % of NCO (mol % of NCO extender Polyol functions) functions) diol EX1 PTMEG 650 t-PMDI (100%) Isosorbide EX2 PTMEG 650 IPDI (80%) t-PMDI (20%) Isosorbide CEX1 PTMEG 650 t-PMDI (100% BDO CEX2 PTMEG 650 IPDI (80%) t-PMDI (20%) BDO

B. Production of the Coatings on a Steel Support

[0101] A thin layer of crosslinkable composition as described above was deposited on steel plates (Q-panel R44 standardized) using a Sheen Instruments 1133N bar-coater, equipped with a 150 m bar in order to cover the entire surface of the support with the minimum of composition.

[0102] The composition is then crosslinked in a vacuum oven under a vacuum of 100 mbar according to the following thermal cycle: [0103] heating at 100 C. for 60 min; [0104] increase in the heating temperature from 100 C. to 140 C. with a gradient of 2 C./min; [0105] heating at 140 C. for 90 min; [0106] increase in the heating temperature from 140 C. to 160 C. with a gradient of 2 C./min; [0107] heating at 160 C. for 30 min.

C. Characterization/Evaluation of the Properties of the Coatings Thus Obtained

Impact Resistance (1 kg at 1 m)

[0108] The impact resistance measurements were carried out according to standard ISO 6272: Paints and varnishesRapid deformation (impact resistance)testsPart 1: falling-weight test, large area indenter.

Adhesion (Grid Test)

[0109] The adhesion measurements were carried out in accordance with ISO standard 2409 Paints and varnishesCross-cut test.

[0110] Folding

[0111] The folding tests were carried out by folding the support at 90 (coating on the inside and outside face). The resistance of the coating was then evaluated qualitatively at the level of the fold.

Glass Transition Temperature (Tg)

[0112] The Tg measurements (expressed in degrees Celsius ( C.)) were carried out by differential scanning calorimetry (measured at the second pass 60 C. to 250 C., 20 C.min.sup.1.

TABLE-US-00002 Tg Impact resistance Adhesion Folding ( C.) EX1 Good + (1) OK 30 EX2 Good ++ (0) OK 48 CEX1 Poor (4) Tearing 4 CEX2 Good + (1) OK 14

[0113] The tests show that the coatings obtained after crosslinking of compositions containing isosorbide and pentamethylene diisocyanate have a higher Tg than the corresponding coatings obtained with BDO. In addition, the replacement of BDO with isosorbide can also lead to an increase in the adhesion of the coating to the substrate and to an increase in its folding resistance (cf. EX2 compared to CEX2).