Paper
Dipentaerythritol-hexakis(4-hydroxybenzoate)
Green Chemistry
(dip-ester): Ar-OCH2CHCH2), 6.99–7.12 (m, 6 H, 3,5-Ar), 7.90–8.03 (m, 6 H,
dipentaerythritol (96.9 g, 0.381 mol), ethyl-4-hydroxybenzoate 2,6-Ar).
(416 g, 2.50 mol) and DBTDL (9.45 g, 4.99 mmol) were added
Glycidyl ether of glycerol-tris(4-hydroxybenzoate) (gly-ester-
to a three-neck flask and heated to 180 °C for 48 h under nitro- epoxy): compound gly-ester (41.5 g), epichlorohydrin (127 g,
gen. The same work-out was performed as previously men- 1.38 mol), anhydrous Na2CO3 (58.8 g, 0.555 mol) and DMF
tioned. 287.46 g (90%) of the product was obtained. Tm
=
(4.14 g, 0.57 mol) were heated to 80 °C and kept under reflux
79–111 °C. 1H NMR δ (300 MHz; acetone-d6) 3.53–3.97 (m, 4 H, conditions for 8 h. With the same work-out outlined pre-
OCH2CCH2OCO), 4.34–4.72 (m, 12 H, OCH2CCH2OCO), viously, 46.83 g of the product was obtained, Tg = 18 °C. 1H
6.82–7.41 (m, 12 H, 3,5-Ar), 7.85–8.07 (m, 12 H, 2,6-Ar), 9.11 NMR δ (300 MHz; acetone-d6) 2.52–4.68 (m, 4 H, CHCH2OCO,
(br. s, 6 H, Ar-OH).
Ar-OCH2CHCH2), 5.03–5.70 (br. s, 1 H, CHOCO), 6.77–7.17
(m, 6 H, 3,5-Ar), 7.65–8.01 (m, 6 H, 2,6-Ar).
Glycidyl ether of pentaerythritol-tetrakis(4-hydroxybenzoate)-
(pen-ester-epoxy): compound pen-ester (49.1 g), epichlorohy-
General procedure for the synthesis of the multifunctional
epoxy resins
Ethyl 4-(glycidyloxy)benzoate (EHB-epoxy): ethyl-4-hydroxy- drin (148 g, 1.59 mol), anhydrous Na2CO3 (68.7 g, 0.648 mol)
benzoate (15.12 g, 0.091 mol), anhydrous Na2CO3 (19.3 g, and DMF (4.14 g, 0.57 mol) were heated to 80 °C and kept
0.182 mol, 2.00 eq.) and freshly distilled DMF (1.5 ml, under reflux conditions for 8 h. The same work-out was per-
0.02 mol, 20 mol%) were mixed together. Epichlorohydrin formed as previously mentioned. 51.89 g of the highly viscous
(120 ml, 1.53 mol, 16.8 eq.) was added to the mixture via the product was obtained, Tg = 18 °C. 1H NMR δ (300 MHz;
reflux condenser. The mixture was then heated to 80 °C for acetone-d6) 2.66–4.81 (m, 24 H, C-CH2OCO, Ar-OCH2CHCH2),
12 hours under a nitrogen atmosphere. After removal of the 6.99–7.12 (m, 8 H, 3,5-Ar), 7.88–8.02 (m, 8 H, 2,6-Ar).
excess of epichlorohydrin in a vacuum rotary evaporator, the
Glycidyl ether of sorbitol-hexakis(4-hydroxybenzoate) (sor-
resulting salt was taken into an excess of toluene, subsequently ester-epoxy): compound sor-ester (50.8 g), epichlorohydrin
dried over MgSO4 and eventually filtered. The product was (155 g, 1.67 mol), anhydrous Na2CO3 (70.5 g, 0.665 mol) and
further dried at 60 °C for 24 hours under high vacuum. To DMF (0.85 g, 11.6 mmol) were heated to 80 °C and kept under
complete the cyclisation reaction, 10 g of Na2CO3 were added reflux conditions for 8 h. The same work-out was performed as
in a second step and the mixture was stirred for 3 hours at previously mentioned. 52.80 g of the product was obtained,
80 °C. The product was then filtered, washed with toluene and Tg
dried at 60 °C for 18 hours. Ethyl 4-(glycidyloxy)benzoate was (Ar-OCH2CHCH2), 50.22 (Ar-OCH2CHCH2), 63.51–86.70
obtained quantitatively. 1H NMR δ (300 MHz; chloroform-d3; (OCHCHCH2),
114.88 (3,5-Ar), 122.40–122.65 (1-Ar),
= δ (75 MHz; acetone-d6) 44.39
18 °C. 13C NMR
Me4Si; 310 K) 1.37 (t, 3 H, OCH2CH3), 2.75 (m, 1 H, CHCH2O), 131.90–132.16 (2,6-Ar), 162.80–163.43 (4-Ar), 165.42–166.15
2.90 (m, 1 H, CHCH2O), 3.35 (m, 1 H, OCH2CH), 4.13 (d, 2 H, (Ar-COO).
OCH2CH3), 4.34 (q, 2 H, OCH2CH), 6.92 (m, 2 H, 2,6-Ar), 7.99
(m, 2 H, 3,5-Ar).
Glycidyl ether of dipentaerythritol-hexakis(4-hydroxybenzo-
ate) (dip-ester-epoxy): compound dip-ester (50.0 g), epichloro-
Glycidyl ether of 1,6-hexanediol-bis(4-hydoxybenzoate) (hex- hydrin (148 g, 1.59 mol), anhydrous Na2CO3 (68.97 g,
ester-epoxy): compound hex-ester (100.2 g), epichlorohydrin 0.650 mol) and DMF (0.85 g, 11.6 mmol) were heated to 80 °C
(258 g, 2.79 mol), anhydrous Na2CO3 (118 g, 1.11 mol) and and kept under reflux conditions for 8 h. The same work-out
DMF (4.14 g, 0.57 mol) were heated to 80 °C and refluxed for was performed as previously mentioned. 56.20 g of the
8 h. The excess of epichlorohydrin was removed by rotary eva- product was obtained, Tg = 3 °C. 1H NMR δ (300 MHz; acetone-
poration and the resulting mixture washed with toluene d6) 2.65–5.02 (m, 24 H, C-CH2, Ar-OCH2CHCH2), 6.71–7.22
(250 mL), filtered and dried over Na2SO4. Finally, the product (m, 8 H, 3,5-Ar), 7.44–8.06 (m, 8 H, 2,6-Ar).
was dried under vacuum at 100 °C for 12 h. 98.41 g of a white
Formulation, mixing and curing
solid was obtained, Tg = 9 °C. 1H NMR δ (300 MHz; acetone-d6)
1.46 (m, 4 H, OCH2CH2CH2), 1.73 (m, 4 H, OCH2CH2CH2), All formulations contain 4 wt% of Cardolite LITE HP 2513 as a
2.70–4.20 (m, 4 H, OCH2, OCH2CHCH2, CHOCH2CHCH2), 6.85 reactive diluent and 0.3 wt% of Fenuron as an accelerator.
(m, 8 H, 3,5-Ar), 7.91 (m, 8 H, 2,6-Ar).
Dicyandiamide (DICY) was added in stoichiometric quantity
Glycidyl ether of trimethylolpropane-tris(4-hydroxybenzo- (amine equivalent weight of 21 g eq.−1) with respect to the
ate) (tmp-ester-epoxy): compound tmp-ester (41.3 g), epichloro- epoxy resins. The percentage mentioned in the name of the
hydrin (137 g, 1.48 mol), anhydrous Na2CO3 (53.2 g, formulations corresponds to the ratio of epoxy groups from
0.502 mol) and DMF (4.14 g, 0.57 mol) were heated to 80 °C the synthesized epoxy resin vs. those from Araldite CY 225.
and refluxed for 8 h. The excess of epichlorohydrin was
Epoxy resins were mixed with the Planimax for 1 h at
removed by rotary evaporation and the resulting mixture 100 °C under reduced pressure. After addition of the hardener
washed with toluene (200 mL), filtered and dried over Na2SO4. and the accelerator, the mixture was additionally stirred for
Finally, the product was dried under vacuum at 100 °C for 30 minutes. The formulation was then poured in a pre-heated
12 h. 42.28 g of the product was obtained, Tg = 16 °C. 1H NMR mold and cured for 1 h at 140 °C and 1 h at 180 °C. DSC ana-
δ (300 MHz; acetone-d6) 0.84–1.14 (m, 3 H, C-CH2CH3), lyses of the samples confirmed that all the samples were fully
1.60–1.88 (m, 2 H, C-CH2CH3), 2.65–4.76 (m, 18 H, C-CH2O, cured.
Green Chem.
This journal is © The Royal Society of Chemistry 2013