LIMONENE-BASED (METH)ACRYLATES FOR USE IN 3D PRINTING

Abstract

The present invention relates to photocurable compositions, comprising a limonene-based (meth)acrylate (A) obtainable by reacting a) 1 equivalent of a compound of formula, especially (I) with 1 to 3 equivalents of a compound of formula (II) in the presence of a catalyst and an inhibitor at elevated temperature and its use in a photopolymerization 3D printing process. The limonene-based (meth)acrylate (A) significantly increases stiffness and glass transition temperatures of photo-cured acrylate compositions. While such effects are usually achieved with the use of aromatic or bisphenol A based compounds, the limonene-based (meth)acrylate (A) offers a sustainable alternative at much lower viscosity.

##STR00001##

Claims

1. A photocurable composition, comprising (A) a limonene-based (meth)acrylate obtainable by reacting a) 1 equivalent of a compound of formula ##STR00069## especially ##STR00070## with 1 to 3 equivalents of a compound of formula ##STR00071##  in the presence of a catalyst and a polymerization inhibitor at elevated temperature, wherein  R and R′ are independently of each other H, or a methyl group,  R.sup.1, R.sup.2 and R.sup.3 are independently of each other H, or a C.sub.1-C.sub.4 alkyl group, b) optionally reacting the product obtained in step a) with an acid anhydride, or acyl halide; (B) optionally an oligomer (B), (C) a diluent (C), and (D) a photoinitiator (D).

2. The photocurable composition according to claim 1, wherein the viscosity of the photocurable composition is in the range of 10 to 3000 mPa.Math.s at 30° C.

3. The photocurable composition according to claim 1, wherein R.sup.2 and R.sup.3 are H.

4. The photocurable composition according to claim 1, wherein R.sup.1 is a methyl group.

5. The photocurable composition according to claim 1, wherein the viscosity of the limonene-based (meth)acrylate (A) obtained by reacting compound (I) and (II) is in the range of 1 to 500 Pa.Math.s at 25° C.

6. The photocurable composition according to claim 1, wherein the photoinitiator (D) is a compound of the formula XII ##STR00072## wherein R.sub.50 is unsubstituted cyclohexyl, cyclopentyl, phenyl, naphthyl or biphenylyl; or is cyclohexyl, cyclopentyl, phenyl, naphthyl or biphenylyl substituted by one or more halogen, C.sub.1-C.sub.12 alkyl, C.sub.1-C.sub.12 alkoxy, C.sub.1-C.sub.12 alkylthio or by NR.sub.53R.sub.54; or R.sub.50 is unsubstituted C.sub.1-C.sub.20 alkyl or is C.sub.1-C.sub.20 alkyl which is substituted by one or more halogen, C.sub.1-C.sub.12 alkoxy, C.sub.1-C.sub.12 alkylthio, NR.sub.53R.sub.54 or by —(CO)—O—C.sub.1-C.sub.24 alkyl; R.sub.51 is unsubstituted cyclohexyl, cyclopentyl, phenyl, naphthyl or biphenylyl; or is cyclohexyl, cyclopentyl, phenyl, naphthyl or biphenylyl substituted by one or more halogen, C.sub.1-C.sub.12 alkyl, C.sub.1-C.sub.12 alkoxy, C.sub.1-C.sub.12 alkylthio or by NR.sub.53R.sub.54; or R.sub.51 is —(CO)R′.sub.52; or R.sub.51 is C.sub.1-C.sub.12 alkyl which is unsubstituted or substituted by one or more halogen, C.sub.1-C.sub.12 alkoxy, C.sub.1-C.sub.12 alkylthio, or by NR.sub.53R.sub.54; R.sub.52 and R′.sub.52 independently of each other are unsubstituted cyclohexyl, cyclopentyl, phenyl, naphthyl or biphenylyl, or are cyclohexyl, cyclopentyl, phenyl, naphthyl or biphenylyl substituted by one or more halogen, C.sub.1-C.sub.4 alkyl or C.sub.1-C.sub.4 alkoxy; or R.sub.52 is a 5- or 6-membered heterocyclic ring comprising an S atom or N atom; R.sub.53 and R.sub.54 independently of one another are hydrogen, unsubstituted C.sub.1-C.sub.12 alkyl or C.sub.1-C.sub.12 alkyl substituted by one or more OH or SH wherein the alkyl chain optionally is interrupted by one to four oxygen atoms; or R.sub.53 and R.sub.54 independently of one another are C.sub.2-C.sub.12 alkenyl, cyclopentyl, cyclohexyl, benzyl or phenyl, or the photoinitiator (D) is a mixture of a compound of the formula (XII) and a compound of the formula ##STR00073## R.sub.29 is hydrogen or C.sub.1-C.sub.18 alkoxy; R.sub.30 is hydrogen, C.sub.1-C.sub.18 alkyl, C.sub.1-C.sub.12 hydroxyalkyl, C.sub.1-C.sub.18 alkoxy, OCH.sub.2CH.sub.2—OR.sub.34, morpholino, S—C.sub.1-C.sub.18 alkyl, a group —HC═CH.sub.2, —C(CH.sub.3)═CH.sub.2, ##STR00074## d, e and f are 1-3; c is 2-10; G1 and G2 independently of one another are hydrogen or methyl; R.sub.34 is hydrogen, ##STR00075## R.sub.31 is hydroxy, C.sub.1-C.sub.16alkoxy, morpholino, dimethylamino or —O(CH.sub.2CH.sub.2O).sub.g-C.sub.1-C.sub.16 alkyl; g is 1-20; R.sub.32 and R.sub.33 independently of one another are hydrogen, C.sub.1-C.sub.6 alkyl, C.sub.1-C.sub.16alkoxy or —O(CH.sub.2CH.sub.2O).sub.g-C.sub.1-C.sub.16 alkyl; or are unsubstituted phenyl or benzyl; or phenyl or benzyl substituted by C.sub.1-C.sub.12-alkyl; or R.sub.32 and R.sub.33 together with the carbon atom to which they are attached form a cyclohexyl ring; R.sub.35 is hydrogen, OR.sub.36 or NR.sub.37R.sub.38; R.sub.36 is hydrogen, C.sub.1-C.sub.12 alkyl which optionally is interrupted by one or more non-consecutive O-atoms and which uninterrupted or interrupted C.sub.1-C.sub.12 alkyl optionally is substituted by one or more OH, or R.sub.36 is ##STR00076## R.sub.37 and R.sub.38 independently of each other are hydrogen or C.sub.1-C.sub.12 alkyl which is unsubstituted or is substituted by one or more OH; R.sub.39 is C.sub.1-C.sub.12 alkylene which optionally is interrupted by one or more non-consecutive O, —(CO)—NH—C.sub.1-C.sub.12alkylene-NH—(CO)— or ##STR00077##  with the proviso that R.sub.31, R.sub.32 and R.sub.33 not all together are C.sub.1-C.sub.16alkoxy or —O(CH.sub.2CH.sub.2O).sub.g-C.sub.1-C.sub.16 alkyl, or the photoinitiator is a mixture of different compounds of the formula (XII), or the photoinitiator is a trialkyl benzoyl, or dialkyl dibenzoyl germanium compound, or the photoinitiator is camphorquinone in combination with a tertiary amine.

7. The photocurable composition according to claim 1, wherein the oligomer (B) is selected from polyester acrylates, polyether acrylates, epoxy acrylates and urethane acrylates.

8. The photocurable composition according to claim 1, wherein the oligomer (B) is obtained by reacting a polyalkylene glycol with caprolactone, isophorone diisocyanate and an hydroxyalkylacrylate, or the oligomer (B) is obtained by reacting caprolactone, isophorone diisocyanate and an hydroxyalkylacrylate; or the oligomer (B) is obtained by reacting caprolactone, isophorone diisocyanate and hydroxyethylacrylate; or the oligomer (B) is obtained by reacting trimethylhexamethylene diisocyanate with hydroxyethylmethacrylate, or the oligomer (B) is obtained by reacting (B1) a hydroxyalkylacrylate, or hydroxyalkylmethacrylate, (B2) an aliphatic diisocyanate, cycloaliphatic diisocyanate, or an aromatic diisocyanate, and (B3) a polyester polyol, which is derived from aliphatic dicarboxylic acids and aliphatic diols, and (B4) optionally a second polyol.

9. The photocurable composition according to claim 1, wherein the diluent (C) is selected from glycerol dimethacrylate, N-vinyl-pyrrolidone, vinyl-imidazole, N-vinylcaprolactam, N-(hydroxymethyl)vinylamide, N-hydroxyethyl vinylamide, N-isopropylvinylamide, N-isopropylmethvinylamide, N-tert-butylvinylamide, N,N′-methylenebisvinylamide, N-(isobutoxymethyl)vinylamide, N-(butoxymethyl)vinylamide, N-[3-(dimethylamino)propyl]methvinylamide, N,N-dimethylvinylamide, N,N-diethylvinylamide, N-methyl-N-vinylacetamide, acryloylmorpholine, methacryloylmorpholine, N-(hydroxymethyl)acrylamide, N-hydroxyethyl acrylamide, N-isopropylacrylamide, N-isopropylmethacrylamide, N-tert-butylacrylamide, N,N′-methylenebisacrylamide, N-(isobutoxymethyl)acrylamide, N-(butoxymethyl)acrylamide, N-[3-(dimethylamino)propyl]methacrylamide, N,N-dimethylacrylamide, N,N-diethylacrylamide, N- (hydroxymethyl)methacrylamide, N-hydroxyethyl methacrylamide, N-isopropylmethacrylamide, N-isopropylmethmethacrylamide, N-tert-butylmethacrylamide, N,N′-methylenebismethacrylamide, N-(isobutoxymethyl)methacrylamide, N-(butoxymethyl)methacrylamide, N-[3-(dimethylamino)propyl]methmethacrylamide, N,N-dimethylmethacrylamide and N,N-diethylmethacrylamide, isobornyl methacrylate, tetrahydrofurfuryl methacrylate, ethoxylated phenyl methacrylate, cyclohexylmethacrylate, lauryl methacrylate, stearyl methacrylate, octyl methacrylate, isodecyl methacrylate, tridecyl methacrylate, caprolactone methacrylate, nonyl phenol methacrylate, cyclic trimethylolpropane formal methacrylate, methoxy polyethyleneglycol methacrylates, methoxy polypropyleneglycol methacrylates, hydroxyethyl methacrylate, hydroxypropyl methacrylate, glycidyl methacrylate, 1,3-butylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, polyethylene glycol (200) di(meth)acrylate, tetraethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polyethylene glycol (400) di(meth)acrylate, ethoxylated (3) bisphenol A di(meth)acrylate, dipropylene glycol di(meth)acrylate, alkoxylated hexanediol di(meth)acrylate, ethoxylated (4) bisphenol A di(meth)acrylate, ethoxylated (10) bisphenol A di(meth)acrylate, polyethylene glycol (600) di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, polytetramethylene glycol di(meth)acrylate, 3-methyl-1,5-pentanediol di(meth)acrylate, dimethylol-tricyclodecane di(meth)acrylate, bistrimethylolpropane tetraacrylate, pentaerythritol tetracrylate, tetramethylolmethane tetramethacrylate, pentaerythritol tetramethacrylate, bistrimethylolpropane tetramethacrylate, ethoxylated pentaerythritol tetraacrylate, propoxylated pentaerythritol tetraacrylate, dipentaerythritol tetraacrylate, ethoxylated dipentaerythritol tetraacrylate and propoxylated dipentaerythritol tetraacrylate and mixtures thereof

10. A process for the production of a limonene-based (meth)acrylate, comprising a) reacting a) 1 equivalent of a compound of formula ##STR00078## especially ##STR00079## with 1 to 3 equivalents of a compound of formula ##STR00080## in the presence of a catalyst and an inhibitor at elevated temperature, wherein R and R′ are independently of each other H, or a methyl group, R.sup.1, R.sup.2 and R.sup.3 are independently of each other H, or a C.sub.1-C.sub.4 alkyl group, especially a methyl group, and b) optionally reacting the product obtained in step a) with an acid anhydride, or acyl halide.

11. The process according to claim 10, wherein the catalyst is selected from triphenyl phosphine, 1,2-dimethylimidazole and benzyltriethylammonium chloride.

12. A method for producing a three-dimensional article, comprising a) providing the photocurable composition according to claim 1, b) exposing the photocurable composition to actinic radiation to form a cured crossection, c) repeating steps (a) and (b) to build up a three-dimensional article.

13. The method according to claim 12, comprising a vat photopolymerization, wherein the photocurable composition according to claim 1 in step b) is cured directly onto a translated or rotated substrate, and the irradiation is patterned via stereolithography, holography, or digital light projection (DLP).

14. The method according to claim 12, comprising a) applying a layer of the photocurable composition of claim 1 onto a surface; b) exposing the layer imagewise to actinic radiation to form an imaged cured cross-section; c) applying a second layer of the photocurable composition onto the previously exposed imaged cross-section; d) exposing the layer from step (c) imagewise to actinic radiation to form an additional imaged cross-section, wherein the radiation causes curing of the second layer in the exposed areas and adhesion to the previously exposed cross-section; and e) repeating steps (c) and (d) in order to build up a three-dimensional article.

15. A three-dimensional article, which is a cured product of the photocurable composition according to claim 1.

16. Use of the photocurable composition according to claim 1, or a limonene-based (meth)acrylate, obtained by a) reacting a) 1 equivalent of a compound of formula ##STR00081## especially ##STR00082## with 1 to 3 equivalents of a compound of formula ##STR00083## in the presence of a catalyst and an inhibitor at elevated temperature, wherein R and R′ are independently of each other H, or a methyl group, R.sup.1, R.sup.2 and R.sup.3 are independently of each other H, or a C.sub.1-C.sub.4 alkyl group, especially a methyl group, in a photopolymerization 3D printing process.

17. The photocurable composition according to claim 1, wherein the product of step a) is reacted with an acid anhydride or acyl halide.

18. The photocurable composition according to claim 1, further comprising an oligomer (B).

19. The photocurable composition of claim 8, wherein the oligomer (B) is obtained by reacting (B1) a hydroxyalkylacrylate, or hydroxyalkylmethacrylate, (B2) an aliphatic diisocyanate, cycloaliphatic diisocyanate, or an aromatic diisocyanate, (B3) a polyester polyol, which is derived from aliphatic dicarboxylic acids and aliphatic diols, and (B4) a second polyol.

Description

EXAMPLES

Materials

[0389] Limonene dioxide (LO) was purchased from Nitrochemie Aschau GmbH, 1,2-dimethylimidazol (DMI, 98%), butylated hydroxytoluene (BHT, 99%), methacrylic acid (MA, 99%, 250 ppm MEHQ), Diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO, 97%) and glycidyl methacrylate (GMA, 97%, 100 ppm MEHQ) were obtained from Sigma Aldrich. Magnesium oxide (99%, nanoparticles, 20 nm) and 4-methacryloylmorpholine (ACMO, 98%) were purchased from abcr and TCI, respectively. Laromer© UA 9089 (Laromer) was provided by BASF.

Methods

[0390] NMR spectra were recorded in deuterated chloroform on an ARX 300 spectrometer from Bruker at room temperature. The chemical shifts were referenced to the solvent signals. DSC measurements were performed using a Perkin Elmer's Pyris 1 with a heating and cooling rate of 20 K min.sup.−1 in the temperature range between 0 and 200° C. Tensile testing was performed on a ZwickZ005(Ulm, Germany, ISO 527-1/2) with a drawing speed of 5 mm min.sup.−1. The mechanical properties such as elastic modulus, tensile strength and breaking elongation extracted from measurements at 21° C. by taking the statistical average of four to six test specimens (5A), which were conditioned before testing (24 h, 21° C., const. humidity. The viscosities were measured on a MARS from Thermo Scientific using a plate-plate set-up with a plate diameter of 35 mm and a gap of 0.6 mm at various shear rates from 0.1 to 100 s.sup.−1 (100 steps, logarithmic, 5 s per step, 3 s integration time, 25° C.) and the final viscosity received as an average over all 100 values. Significant shear-thinning was usually not observed, as indicated by the standard deviations.

Synthesis of Limonene-Based Methacrylates (LMA)

[0391] Mixtures of limonene dioxide (LDO), methacrylic acid (MA), butylated hydroxytoluene (BHT) and the respective catalyst were added to a flask according to the weight portions described in Table 1. The flask was then lowered into a preheated oil bath, which marked the start of the reaction during which the reaction mixture was vigorously stirred under air atmosphere. The products were received as viscous liquids and used without further purification, or after liquid-liquid extraction in case of LDMA-4. For this extraction the respective LDMA grade was dissolved in 60 ml of dichloromethane and the solution washed four times with 50 ml 1 M K.sub.2CO.sub.3-Solution and one time with distilled water. The organic fraction was dried over MgSO.sub.4 and the solvent subsequently evaporated under reduced pressure.

TABLE-US-00004 TABLE 1 Weight portions and reaction conditions of limonene-based methacrylate (LMA) syntheses. Sample LO MA Catalyst m(BHT) T t code m [g] n [mmol] m [g) n [mmol] Catalyst m [mg] [mg] [° C.] [h] LDMA-1 9.165 54.48 9.837 114.3 DMI 379 190 100 6 LDMA-2 106.52 633.1 92.51 1074.6 DMI 3985 796 100 8 LDMA-3 75.11 446.5 49.93 580.0 DMI 2510 1250 100 13 LDMA-4 23.75 141.1 36.45 423.4 DMI 1198 120.4 100 5 LDMA-1 and LDMA-2 were further purified.

Synthesis of LDMA-2-GDMA

[0392] Based on the weight portions of the starting materials and the methacrylic acid (MA) turnover of 72% (calculated from .sup.1H-NMR spectrum) during the synthesis of LDMA-2, the amount of residual MA was calculated to be 1.48 mmol g.sup.−1. LDMA-2 (77.26 g, 114.3 mmol MA) was mixed inside a flask with glycidyl methacrylate (16.25 g, 114.3 mmol) and the mixture was vigorously stirred under air atmosphere at 100° C. for 90 minutes. The product was used without further purification.

Synthesis of LDMA-1-GDMA

[0393] Based on the weight portions of the starting materials and the methacrylic acid (MA) turnover of 58% (calculated from .sup.1H-NMR spectrum) during the synthesis of LDMA-1, the amount of residual MA was calculated to be 2.60 mmol g.sup.−1. LDMA-1 (12.90 g, 33.54 mmol MA) was mixed inside a flask with glycidyl methacrylate (4.768 g, 33.54 mmol) and the mixture was vigorously stirred under air atmosphere at 100° C. for 3 h. The product was used without further purification.

Preparation and Curing of Acrylate Resins

[0394] The base resin formulation (BF) consists of 4-methacryloylmorpholine (ACMO) and a polyester-urethane-acrylate prepolymer Laromer UA 9089 in a 59:39-ratio. Additionally 1 wt % diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO) as a photoinitiator was applied in all cured samples. For the preparation of the acrylate resins, TPO was first dissolved in the respective amount of ACMO and subsequently Laromer homogenized with this solution according to the predefined ratio. Any tested component was afterwards added according to Table 2 and homogenized using a SpeedMixer DAC 150.1 FV from Hausschild (2 min, 2500 RPM). Tested component LDMA-1-MgO consists of LDMA-1 and additional MgO (35.85 mg per gram of LDMA-1) but were not added simultaneously. In this case, TPO and MgO were added to ACMO and kept in an ultrasonic bath (10 min, 35° C.) to yield a homogenous dispersion. LDMA-1 was then added in three portions and after each addition the mixture was kept in an ultrasonic bath (10 min, 35° C.). During the last step the turbid dispersion turned translucent. Subsequently the respective amount of Laromer was added and the mixture homogenized using a SpeedMixer DAC 150.1 FV from Hausschild (2 min, 2500 RPM) to yield a completely transparent resin. The UV curing of the casted samples was performed under a Mercury-vapor lamp (400 W, 280-700 nm, 10 cm distance, 2×10 min from both sides) with a thermal post-cure (30 min, 150° C.) in an oven.

TABLE-US-00005 TABLE 2 Acrylate resins and the respective weight ratios of their acrylate components. Tested component m.sub.f (TPO) m.sub.f (MgO) # Resin (TC) m (BF):m (TC) [wt %] [wt %] BF.sup.a — 100:0  1 0 B-1 LDMA-3 90:10 1 0 B-2 LDMA-3 70:30 1 0 B-3 LDMA-3 50:50 1 0 B-4 LDMA-4.sub.purified 70:30 1 0 B-5 BisGMA 70:30 1 0 B-6 LDMA-1 70:30 1 0 B-7 LDMA-2-GDMA 70:30 1 0 B-8 LDMA-1-GDMA 70:30 1 0 B-9 LDMA-1-MgO 70:30 1 1.1 .sup.aBF = base formulation, which consist of a mixture of ACMO and Laromer in a 59:39-ratio.