Process and apparatus for locally polymerizing a starting material by dual color photopolymerization and method for volumetric printing of a shaped body
A process, an apparatus, and photoswitchable photoinitators for polymerizing a starting material by dual color photopolymerization. In particular, photoinitiators are provided, which cause curing of photopolymerizable formulations upon illumination with two different wavelengths.
1. A process for locally polymerizing a starting material by dual color photopolymerization, comprising:
providing a polymerizable starting material containing photoinitiator molecules which can be converted by sequential optical excitation into a reactive state in which the photoinitiator molecules locally trigger polymerization of the starting material; and
photopolymerizing the starting material in a local volume by irradiating light of a first wavelength and light of a second wavelength, different from the first wavelength, into the local volume, whereby in the local volume
the photoinitiator molecules are converted, due to the absorption of the light of the first wavelength, from an initial state in which the photoinitiator molecules substantially do not absorb the light of the second wavelength, into an intermediate state with changed optical properties compared to the initial state, such that the photoinitiator molecules in the intermediate state absorb the light of the second wavelength; and
the photoinitiator molecules are transferred from the intermediate state to the reactive state due to the absorption of the light of the second wavelength, which triggers the polymerization locally; wherein the polymerizable starting material further contains a solvent, wherein the solvent is water.
2. The process according to claim 1 , wherein the polymerizable starting material contains the following parts by weight:
1-99.9999 wt %, preferably 5-99.99 wt %, more preferably 20-99.9 wt % of photopolymerizable compound(s);
0-99 wt %, preferably 1-50 wt %, more preferably 3-20 wt % co-initiator, when the co-initiator contains photopolymerizable groups;
0-50 wt %, preferably 1-40 wt %, more preferably 3-10 wt % of co-initiator, when the co-initiator does not contain photopolymerizable groups;
0.0001-20 wt %, preferably 0.001-10 wt %, more preferably 0.01-5 wt %, most preferably 0.1-1 wt % of dual color photoinitiator;
0-20 wt %, preferably 1-10 wt %, more preferably 3-5 wt % of acids or bases;
0-90 wt %, preferably 1-70 wt %, more preferably 5-50 wt %, most preferably 10-30 wt % of other additives, such as organic or inorganic fillers, optical brighteners, inhibitors, chain transfer agents and others; and
0-80 wt %, preferably 5-50 wt %, more preferably 10-30 wt % of the solvent.
3. A process according to claim 1 , wherein the light of the first wavelength and the light of the second wavelength are simultaneously irradiated into the local volume; or wherein the light of the second wavelength is irradiated into the local volume after the irradiation of the light of the first wavelength in the local volume has ended, the light of the second wavelength being irradiated before the end of a decay time of the intermediate state of the photoinitiator molecules.
4. The process according to claim 1 , wherein the photoinitiator molecules are converted into a reactive state due to the sequential absorption of light of the second wavelength which triggers a polymerization in the local volume.
5. The process according to claim 1 , wherein the photoinitiator molecules are converted into a reactive state due to the absorption of the light of the second wavelength, which triggers a radical polymerization in the local volume.
6. The process according to claim 1 , wherein the photoinitiator molecule is represented by the following formula (I)
wherein R a and R b are selected independently from unsubstituted or substituted aryl, unsubstituted or substituted alkyne or a linked to each other to form a unsubstituted or substituted ring structure, Y is selected from O, S, or N; where Y is N, the substituent contains the atoms necessary to complete a cyclic structure with R 8 selected from the group consisting of benzimidazole, indoline, indole, dihydroquinoline, and tetrahydroquinoline; wherein Z is selected from N or CR 4 ; wherein R 3 to R 8 are independently selected from the group consisting of H; D; halogen; NO 2 ; CN; OH; SH; substituted or unsubstituted C 1 -C 20 -alkyl; substituted or unsubstituted C 3 -C 20 -cycloalkyl; substituted or unsubstituted C 6 -C 48 -aryl; substituted or unsubstituted C 2 -C 42 -heteroaryl; substituted or unsubstituted C 2 -C 49 -alkyl acyl; substituted or unsubstituted C 2 -C 49 -aryl acyl; substituted or unsubstituted C 1 -C 20 -alkoxy; substituted or unsubstituted C 6 -C 48 -aryloxy, and NH 2 ; substituted or unsubstituted C 1 -C 20 -alkyl ester; substituted or unsubstituted C 6 -C 48 -aryl ester; substituted or unsubstituted C 1 -C 20 alkyl amide; substituted or unsubstituted C 6 -C 48 -aryl amide; NR′ 2 , SiR′ 3 , —O—SiR′ 3 wherein R′ is independently selected from the group consisting of substituted or unsubstituted C 1 -C 20 -alkyl and substituted or unsubstituted C 6 -C 48 -aryl, two R′ may form a ring structure; substituted or unsubstituted carboxylic acids and salts thereof; substituted or unsubstituted sulfonic acids and salts thereof; substituted or unsubstituted sulfonic esters; substituted or unsubstituted sulfonic amides; formyl; ether, thioether; carbonate; carbonate ester; sulfates; boronic acids; boronic esters; phosphonic acids; phosphonic esters; phosphines; phosphates; peroxycarbonic acids; thiocarbonic acids; sulfinic acids; sulfinic esters; sulfonates; thiolesters, sulfoxides; sulfones; hydrazides; thioaldehydes; ketones; thioketones; oximes; hydrazines; nitroso; azo; diazo; diazonium; isocyanides; cyanate; isocyanate; thiocyanate; isothiocyanate; hydroperoxide; peroxide; acetals; ketal; orthoester; orthocarbonate esters; ammonium; imines; imides; azide; nitrate; isonitrile; nitrosoxy; substituted or unsubstituted carbamates; substituted or unsubstituted ethers; substituted or unsubstituted polyether carbamates; substituted or unsubstituted arylazo; substituted or unsubstituted C 2 -C 20 -alkynyl and substituted or unsubstituted C 2 -C 20 -alkenyl; wherein the one or more substituents, if present in one or more of R 3 -R 8 , are independently selected from the group consisting of D; halogen; NO 2 ; CN, C 2 -C 49 -alkyl acyl; substituted or unsubstituted C 1 -C 20 -alkoxy; substituted or unsubstituted C 6 -C 48 -aryloxy; substituted or unsubstituted C 2 -C 49 -aryl acyl; (meth)acrylate; tosyl; NH 2 ; and OH; and/or wherein two adjacent groups of R 5 -R 8 may be linked to each other to form a fused ring structure, preferably, a fused aromatic C 6 -ring; and wherein at least one of R 3 -R 8 , is selected from one of the following structures:
wherein R 14 to R 25 are independently selected from the group consisting of H; D; halogen; NO 2 ; CN; OH; SH; substituted or unsubstituted C 1 -C 20 -alkyl; substituted or unsubstituted C 3 -C 20 -cycloalkyl; substituted or unsubstituted C 6 -C 48 -aryl; substituted or unsubstituted C 2 -C 42 -heteroaryl; substituted or unsubstituted C 2 -C 49 -alkyl acyl; substituted or unsubstituted C 2 -C 49 -aryl acyl; substituted or unsubstituted C 1 -C 20 -alkoxy; substituted or unsubstituted C 6 -C 48 -aryloxy, and NH 2 ; substituted or unsubstituted C 1 -C 20 -alkyl ester; substituted or unsubstituted C 6 -C 48 -aryl ester; substituted or unsubstituted C 1 -C 20 alkyl amide; substituted or unsubstituted C 6 -C 48 -aryl amide; NR′ 2 , SiR′ 3 , —O—SiR′ 3 wherein R′ is independently selected from the group consisting of substituted or unsubstituted C 1 -C 20 -alkyl and substituted or unsubstituted C 6 -C 48 -aryl, two R′ may form a ring structure; substituted or unsubstituted carboxylic acids and salts thereof; substituted or unsubstituted sulfonic acids and salts thereof, substituted or unsubstituted sulfonic esters; substituted or unsubstituted sulfonic amides; formyl; ether, thioether; carbonate; carbonate ester; sulfates; boronic acids; boronic esters; phosphonic acids; phosphonic esters; phosphines; phosphates; peroxycarbonic acids; thiocarbonic acids; sulfinic acids; sulfinic esters; sulfonates; thiolesters, sulfoxides; sulfones; hydrazides; thioaldehydes; ketones; thioketones; oximes; hydrazines; nitroso; azo; diazo; diazonium; isocyanides; cyanate; isocyanate; thiocyanate; isothiocyanate; hydroperoxide; peroxide; acetals; ketal; orthoester; orthocarbonate esters; ammonium; imines; imides; azide; nitrate; isonitrile; nitrosoxy; substituted or unsubstituted carbamates; substituted or unsubstituted ethers; substituted or unsubstituted polyether carbamates; substituted or unsubstituted arylazo; substituted or unsubstituted C 2 -C 20 -alkynyl and substituted or unsubstituted C 2 -C 20 -alkenyl; wherein the one or more substituents, if present in one or more of R 14 -R 25 , are independently selected from the group consisting of D; halogen; NO 2 ; CN, C 2 -C 49 -alkyl acyl; substituted or unsubstituted C 1 -C 20 -alkoxy; substituted or unsubstituted C 6 -C 48 -aryloxy; substituted or unsubstituted C 2 -C 49 -aryl acyl; (meth)acrylate; tosyl; NH 2 ; and OH; and R 15 and R 16 may be linked to each other to form a unsubstituted or substituted ring structure.
7. The process according to claim 1 , wherein the photoinitiator molecule is represented by the following formula (II)
wherein X is selected from S, CR 1 R 2 , or NR 1 ; Y is selected from O, S, or NR c ; when Y is N, the substituent R c contains the atoms necessary to complete a cyclic structure with R 8 selected from the group consisting of benzimidazole, indoline, indole, dihydroquinoline, and tetrahydroquinoline; Z is selected from N or CR 4 ; and R 1 to R 13 are independently selected as defined in R 3 to R 8 regarding formula (I) above.
8. The process according to claim 6 or 7 , wherein one of the substituents R 1 -R 13 contains a functional group which increases the solubility in water.
9. The process according to claim 8 , wherein the functional groups is an ionic functional group forming salts, such as ammonium or sulfonate; polyethyleneglycols, or polar functional groups, such as OH, NH 2 , SO 2 NH 2 .
10. The process according to claim 1 , wherein the polymerizable starting material further contains a co-initiator and/or a sensitizer; wherein the co-initiator is or comprises at least one of a derivative of ethanolamine, aminobenzoic acid, germane, thiol, alcohols, ether, thioether, silane, phosphine, acetal, dialkylaniline, N-phenylglydne, arylsulfinate, iodonium salt, sulfonium salt, and organoborate salt or a combination of at least two of the aforementioned substances.
11. The process according to claim 10 , wherein the co-initiator is of high molecular weight, such as >1000 g/mol, or bound to a polymer to prevent migration in the cured object.
12. The process according to claim 11 , wherein the co-initiator contains polymerizable groups, such as acrylates or methacrylates which are built into the polymer network during curing to prevent later migration of the co-initiator.
13. The process according to claim 10 , wherein the co-initiator contains polymerizable groups, such as acrylates or methacrylates which are built into the polymer network during curing to prevent later migration of the co-initiator.
14. The process according to claim 1 , wherein the polymerizable starting material further contains an additive, an acid and/or a base.
15. The process according to claim 14 , wherein the acid is a weak acid, such as acetic acid, formic acid, benzoic acid, or a strong acid, such as trifluoroacetic acid; and/or wherein the base is an amine, such as diisopropylethylamine, triethylamine, 1,8-diaza-bicydo[5.4.0]undec-7-ene (DBU), 1,5-diazabicydo[4.3.0]non-5-ene (DBN), 1,5,7-tri-azabicyclo[4-4.0]dec-5-en (TBD), 2,6-di-tert-buiyipytide, and 1,4-diazabicyde-[2.2.2]octan (DABCO).
16. A process for 3D-printing a shaped body, wherein the shaped body is produced by means of a process according to claim 1 .
17. The process according to claim 2 , wherein the photopolymerizable A compound(s) are monomers.
18. The process according to claim 2 , wherein the photopolymerizable groups are acrylates.