PHOTOSENSITIVE COMPOSITION FOR 3D PRINTING

Abstract

A process for producing a photosensitive resin for 3D printing includes: (i) treating a vegetable oil with a polyol to form a monoglyceride, (ii) reacting the monoglyceride of step (i) with an unsaturated reagent to form a liquid resin with viscosity lower than 20 Pa.Math.s at the temperature of 20° C., and (iii) mixing the liquid resin with a comonomer and a photoinitiator, as well as the photosensitive resin for 3D printing obtainable from such process and the 3D object obtainable from such photosensitive resin.

Claims

1. A process for producing a photosensitive resin for 3D printing comprising: (i) treating a vegetable oil with a polyol selected from the group which consists of polyols comprising 2 to 6 carbon atoms and at least 2 hydroxyl groups to form a monoglyceride, (ii) reacting the monoglyceride of step (i) with an unsaturated reagent selected from the group which consists of acids, esters or anhydrides comprising at least one carboxylic group and at least one double bond to form a liquid resin with viscosity (measured with a rotational viscometer) lower than 20 Pa.Math.s at the temperature of 20° C., (iii) mixing the liquid resin with a comonomer selected from the group which consists of vinyl and acrylic monomers, and a photoinitiator.

2. The process for producing a photosensitive resin for 3D printing according to claim 1, wherein said vegetable oil is selected from the group which consists of recovery or fresh food vegetable oils.

3. The process for producing a photosensitive resin for 3D printing according to claim 2, wherein said recovery or fresh food vegetable oils are olive oil, linseed oil, grape seed oil, coconut oil, palm oil and palm-kernel oil, corn oil, sunflower oil, sesame seed oil, wheat germ oil, jojoba oil, hemp oil, castor oil, evening primrose oil, avocado oil, soybean oil, rice bran oil, safflower oil, rape oil, peanut oil, walnut oil, macadamia oil.

4. The process for producing a photosensitive resin for 3D printing according to claim 1, wherein said polyol is selected from the group which consists of ethylene glycol, glycerin, pentaerythritol, adonitol, allitol, altritol, arabinitol, dulcitol, erythritol, galaxitol, glucitol, guliltol, iditol, inositol, isomalt, lactitol, lisitol, maltitol, mannitol, perseitol, ribitol, rhamnitol, sorbitol, talitol, threitol, xylitol, and mixtures thereof.

5. The process for producing a photosensitive resin for 3D printing according to claim 1, wherein said unsaturated reagent is selected from the group which consists of maleic anhydride, succinic anhydride, phthalic anhydride, itaconic anhydride, ethyl maleate, itaconic acid, maleic acid, fumaric acid and mixtures thereof.

6. The process for producing a photosensitive resin for 3D printing according to claim 1, wherein said comonomer is selected from the group which consists of vinyl monomers, such as for example N-vinylpyrrolidone, N-vinylcarbazole, triethylene glycol divinyl ether, vinyltoluene and ethyl maleate, and acrylic monomers, such as for example polyethylene glycol diacrylate, hexanediol diacrylate, methyl methacrylate, methacrylic acid and acrylic acid.

7. The process for producing a photosensitive resin for 3D printing according to claim 1, wherein said photoinitiator is selected from the group which consists of acylphosphine oxides, curcumin, benzophenones and derivatives, camphorquinone, anthraquinones and derivatives, xanthone and derivatives, thioxanthone and derivatives.

8. The process for producing a photosensitive resin for 3D printing according to claim 1, wherein said liquid resin has a viscosity greater than 100 mPa.Math.s at the temperature of 20° C.

9. The process for producing a photosensitive resin for 3D printing according to claim 1, wherein said treatment step (i) occurs at a temperature comprised between 180° C. and 230° C., preferably between 200° C. and 220° C., for a time comprised between 15 and 180 minutes, preferably between 60 and 120 minutes.

10. The process for producing a photosensitive resin for 3D printing according to claim 1, wherein said reaction step (ii) occurs at two times conducted at different temperature.

11. The process for producing a photosensitive resin for 3D printing according to claim 9, wherein said reaction step (ii) is conducted at a first time by heating up to a temperature comprised between 120° C. and 170° C., preferably between 140° C. and 160° C., and hence making the reaction occur at such temperature for a time comprised between 15 minutes and 2 hours, preferably between 40 and 70 minutes, and subsequently at a second time by heating up to a temperature comprised between 190° C. and 220° C., preferably between 200° C. and 220° C., and then making the reaction occur at such temperature for a time comprised between 15 and 90 minutes, preferably between 20 and 30 minutes.

12. The process for producing a photosensitive resin for 3D printing according to claim 1, wherein said treatment step (i) and said reaction step (ii) are conducted in nitrogen atmosphere.

13. The process for producing a photosensitive resin for 3D printing according to claim 1, wherein said mixing step (iii) comprises the addition of a coloring agent.

14. The process for producing a photosensitive resin for 3D printing according to claim 13, wherein said coloring agent is selected from the group which consists of Sudan I, Sudan III, Sudan IV, curcumin, E102 and other liposoluble food coloring agents, preferably of red and yellow color.

15. The process for producing a photosensitive resin for 3D printing according to claim 13, wherein said coloring agent is selected from the group which consists of Sudan I and liposoluble food coloring agents.

16. A photosensitive resin for 3D printing obtained according to the process of claim 1.

17. A three-dimensional object obtained by a 3D printer using the photosensitive resin of claim 16.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0027] FIG. 1 illustrates the printing cycle used in the exploratory tests of example 1.

[0028] FIG. 2 illustrates the results obtained in the print test of example 3 with the photosensitive resin Rfot R2.

[0029] FIGS. 3A-D illustrate the results obtained in the print test of example 3 with the photosensitive resin R.sub.fot G2.

[0030] FIGS. 4A-C illustrate the results obtained in the print test of example 3 with the photosensitive resin R.sub.fot C2 and C3.

DETAILED DESCRIPTION OF THE INVENTION

[0031] According to a preferred aspect of the process for producing a photosensitive resin for 3D printing of the present invention the vegetable oil is selected from the group which consists of fresh vegetable oils at high and low unsaturation, and mixtures of recovery vegetable oils, preferably food vegetable oils.

[0032] Examples of food vegetable oils which can be used in the present invention are: olive oil, linseed oil, grape seed oil, coconut oil, palm oil and palm-kernel oil, corn oil, sunflower oil, sesame seed oil, wheat germ oil, jojoba oil, hemp oil, castor oil, evening primrose oil, avocado oil, soybean oil, rice bran oil, safflower oil, rape oil, peanut oil, walnut oil, macadamia oil.

[0033] Advantageously, the vegetable oil is selected from the group which consists of olive oil, sunflower oil, peanut oil, corn oil, various seed oils, palm oil, rape oil, mixtures of frying oils.

[0034] According to a preferred aspect of the process for producing a photosensitive resin for 3D printing of the present invention, the polyol is selected from the group which consists of ethylene glycol, glycerin, pentaerythritol, adonitol, allitol, altritol, arabinitol, dulcitol, erythritol, galaxitol, glucitol, guliltol, iditol, inositol, isomalt, lactitol, lisitol, maltitol, mannitol, perseitol, ribitol, rhamnitol, sorbitol, talitol, threitol, xylitol, and mixtures thereof.

[0035] According to a particularly preferred aspect of the process for producing a photosensitive resin for 3D printing of the present invention, the polyol is selected from the group which consists of glycerin, pentaerythritol, mannitol, and mixtures thereof.

[0036] According to a preferred aspect of the process for producing a photosensitive resin for 3D printing of the present invention, the unsaturated reagent is selected from the group which consists of maleic anhydride, succinic anhydride, phthalic anhydride, itaconic anhydride, ethyl maleate, itaconic acid, maleic acid, fumaric acid and mixtures thereof.

[0037] Advantageously, the unsaturated reagent is selected from the group which consists of maleic anhydride, ethyl maleate, and mixtures thereof.

[0038] According to a preferred aspect of the process for producing a photosensitive resin for 3D printing of the present invention, the comonomer is selected from the group which consists of vinyl monomers, such as for example N-vinylpyrrolidone, N-vinylcarbazole, triethylene glycol divinyl ether, vinyltoluene and ethyl maleate.

[0039] According to a preferred alternative aspect of the process for producing a photosensitive resin for 3D printing of the present invention, the comonomer is selected from the group which consists of acrylic monomers, such as for example polyethylene glycol diacrylate, hexanediol diacrylate, methyl methacrylate, methacrylic acid and acrylic acid.

[0040] According to a preferred aspect of the process for producing a photosensitive resin for 3D printing of the present invention, the photoinitiator is selected from the group which consists of acylphosphine oxides, curcumin, benzophenones and derivatives, camphorquinone, anthraquinones and derivatives, xanthone and derivatives, thioxanthone and derivatives.

[0041] Advantageously, the photoinitiator is selected from the group which consists of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (BAPO), diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO), and curcumin.

[0042] According to a preferred aspect of the process for producing a photosensitive resin for 3D printing of the present invention, the liquid resin has a viscosity greater than 100 mPa.Math.s at the temperature of 20° C.

[0043] Advantageously, the liquid resin has a viscosity comprised between 15 and 0.2 Pa.Math.s, preferably between 10 and 0.5 Pa.Math.s.

[0044] According to a preferred aspect of the process for producing a photosensitive resin for 3D printing of the present invention, the treatment of the vegetable oil with the polyol of step (i) occurs at a temperature comprised between 180° C. and 230° C., preferably between 200° C. and 220° C., for a time comprised between 15 and 180 minutes, preferably between 60 and 120 minutes.

[0045] Advantageously, the treatment step (i) is conducted under nitrogen atmosphere.

[0046] Advantageously, the starting oil is treated with an anhydrifying agent, such as for example anhydrous sodium sulfate or anhydrous magnesium sulfate, and then subjected to filtration in order to eliminate the water traces.

[0047] Advantageously, the treatment step (i) is conducted in the presence of a basic catalyst, such as lithium hydroxide or sodium hydroxide, inserted at the start of the reaction.

[0048] Preferably, the concentration of the basic catalyst in the reaction mixture is comprised in the interval of 0.01-0.03% by weight over the total weight of the reaction mixture.

[0049] In order to verify the reaction that took place, a sample is taken from the reactor and this is mixed with a quantity of ethanol equal in volume to that of the drawn liquid. If after a brief stirring a single phase is obtained that is not turbid, the reaction is considered to be terminated.

[0050] According to a preferred aspect of the process for producing a photosensitive resin for 3D printing of the present invention, the reaction of step (ii) between the monoglyceride of step (i) with the unsaturated reagent occurs at two times conducted at different temperature.

[0051] Preferably, the unsaturated reagent is usually dosed with a stoichiometric defect that can vary from 10 to 40% in accordance with the oil. This condition serves for preventing the gelling of the material at room temperature.

[0052] Advantageously, the reaction step (ii) is conducted at a first time by heating up to a temperature comprised between 120° C. and 170° C., preferably between 140° C. and 160° C., more preferably at about 150° C., and then making the reaction to occur at such temperature for a time comprised between 15 minutes and 2 hours, preferably between 40 and 70 minutes, and subsequently at a second time by heating up to a temperature comprised between 190° C. and 220° C., preferably between 200° C. and 220° C., more preferably at about 205° C., and then making the reaction to occur at such temperature for a time comprised between 15 and 90 minutes, preferably between 20 and 30 minutes.

[0053] Preferably, the time necessary for the reaction can be determined when the evolution of reaction water decreases until ceasing.

[0054] Advantageously, the reaction step (ii) is conducted under nitrogen atmosphere.

[0055] According to a preferred aspect of the process for producing a photosensitive resin for 3D printing of the present invention, the mixing step (iii) comprises the addition of a coloring agent.

[0056] Preferably, the coloring agent is selected from the group which consists of Sudan I, Sudan III, Sudan IV, curcumin, E102 and other liposoluble food coloring agents, preferably of red and yellow color.

[0057] Advantageously, the coloring agent is selected from the group which consists of Sudan I and liposoluble food coloring agents.

[0058] The quantity of coloring agent introduced in the photosensitive resin depends on various factors, including the type of printer used, the type of photoinitiator used, and the light source used for activating the photoinitiator.

[0059] In particular, if a photoinitiator active at 400-405 nm is considered, it is necessary to calculate a concentration of coloring agent which, in that wavelength interval, attenuates the light by 30-50% in the desired print layer. For example, if a minimum print thickness of 0.2 mm is desired, the absorbance of the coloring agent must be 7.5-15 relative absorbance units at 1 cm.

[0060] The present invention is then further illustrated with reference to the following non-limiting examples.

EXAMPLE 1

[0061] Preparation of the Photosensitive Resin

[0062] For the synthesis in liquid phase, a 1000 ml and 500 ml compact mini-reactor was employed with mechanical stirring and electrical heating with temperature and rotation adjustable by a microcontroller by means of the integrated sensors, constituted by an aluminum block for the transmission of heat at high speed and a uniform distribution of the temperature with slots for the internal viewing of the reaction.

[0063] The vegetable oil is transformed into monoglyceride by treatment with glycerin and lithium hydroxide, the latter having catalyst function.

[0064] In the case of use of waste vegetable oil, this was first filtered in order to eliminate possible residues due to the preceding use of the oil (frying residues, residues of food under oil, and so forth) and then reacted with anhydrous sodium sulfate in order to eliminate the moisture of the oil, which can cause problems such as drops explosion at temperatures around 220° C. in reaction step.

[0065] Three samples of vegetable oil were used. The sample R is a waste vegetable oil composed of a single type of seed oil coming from a restaurant, the sample C is a waste vegetable oil containing various oil types, including extra-virgin olive oil, coming from a domestic used oil collection center of a large restaurant chain, and the sample G is composed of fresh sunflower oil (never used for cooking).

[0066] All the reagents, suitably weighed, were mixed within the reactor and the reaction was conducted under nitrogen, so as to ensure an inert environment, at the temperature of 220° C. and stirring set at 180 revolutions/minute.

[0067] The quantities of reagents and the time necessary for completing the reaction are indicated for each sample in the following Table 1.

TABLE-US-00001 TABLE 1 Oil Glycerin Reaction time (g) (g) (h) Mono R1 615.3 134.9 2 Mono R2 263.1 58.95 1 Mono C1 621.1 135.6 3 Mono C2 558.8 118.7 2 Mono C3 596.5 127.8 2:45 Mono G1 546.6 114 3 Mono G2 273.0 50.7 1

[0068] At the end of the reaction, the resulting liquid was cooled and filtered and directly used for the subsequent reaction of formation of the resin with maleic anhydride.

[0069] The mixture of the reagents, monoglyceride and maleic anhydride, suitably weighed, was poured within the same reactor and the reaction was conducted under nitrogen and under stirring at 180 revolutions/minute, first bringing the temperature to 150° C. and allowing reaction at this temperature for about an hour, and then increasing the temperature to 220° C. and allowing reaction at this temperature for about a further hour.

[0070] The quantities of reagents and the total reaction time are indicated for each sample in the following Table 2.

TABLE-US-00002 TABLE 2 Monoglyceride Maleic anhydride Reaction time (g) (g) (h) Resin R1 202.6 59.6 3:25 Resin R2 202.4 47.3 4:15 Resin C1 665.0 149.6 3:45 Resin C2 550.2 124.8 3:00 Resin C3 253.0 50.9 5:20 Resin G1 200.5 45.4 5:30 Resin G2 296.9 64.1 4:20

[0071] The resin R1 resulted solid and “rubbery” due to an excess of maleic anhydride. These characteristics are not in accordance with the liquid resin that it is desired to obtain, characterized by a viscosity preferably comprised between 10 and 0.5 Pa.Math.s, perhaps even quite high, which could be decreased due to the addition of other types of additives and adjuvants. For this reason it was discarded. The resin R2 was obtained with a quantity of maleic anhydride reduced by 20%.

[0072] The resulting liquid resins were cooled and filtered. The resins Cl and C2 resulted turbid due to formation of two phases, and for this reason they were subjected to centrifugation to eliminate the underlying phase.

[0073] The liquid resins were mixed with the bis-acylphosphine radical oxide photoinitiator (BAPO—phenylbis(2,4,6-trimethybenzoyl)phosphine oxide), the N-vinyl-pyrrolidone monomer (NVP—N-Vinyl-Pyrrolidone), and the coloring agent Sudan I to give the photosensitive liquid resins usable for the exploratory print tests and in the 3D object print test.

[0074] The quantities employed for attaining the exploratory tests are reported in the following table 3.

TABLE-US-00003 TABLE 3 Resin 2% BAPO 20% NVP (g) (g) (g) R.sub.fot R2_1 (RAM20) 3.9 0.10 1 R.sub.fot R2_2 (RAM10) 4.4 0.13 0.5 R.sub.fot R2_3 (EPR3) 4.8 0.11 0.11.sup.(*.sup.) R.sub.fot C2 (COOP20) 7.81 0.22 2.01 R.sub.fot C3 (COOP30) 7.87 0.20 2.27 R.sub.fot G1 39 .sup. 1.sup.(**.sup.) 10 R.sub.fot G2 133.6 3.43 35 .sup.(*.sup.)The 2% N-Vinyl-Carbazole monomer was used in place of NVP .sup.(**.sup.)The 2% curcumin radical photoinitiator was used in place of the BAPO. In this case, no other coloring agent was added.

EXAMPLE 2

Exploratory Tests

[0075] For the exploratory tests, the following inexpensive and easy-to-find apparatuses were used: [0076] 1. A HDMI IBM M400 projector having the following characteristics: [0077] Resolution: 1024×768 pixels and 1280×1024; [0078] Digital Input: DVI-I; [0079] Power: 250 Watt; [0080] Contrast: 1800:1; [0081] Brightness 1100 lumen; [0082] Lifetime of the lamp: 3000 hours; [0083] Power of the lamp: 120 Watt; [0084] Type of lamp: P-VIP. [0085] 2. A Raspberry PI 3 model B which allows, once set in the correct manner, the remote control of the “printer” such that it does not constrain the user to a “direct” use of the instrumentation. [0086] 3. An Arduino UNO (FIG. 22) which controls, by means of a driver DRV8825, a stepper motor which moves a screw trolley where an aluminum base has been connected. The image of the desired object is projected on such base, once immersed in the polymerizing resin, so as to allow the formation of the various layers.

[0087] The exploratory tests were carried out in order to verify the actual polymerization of the resin. The suitably-positioned photosensitive resin on an aluminum plate was hit by the light radiation emitted by the DLP projector, which projects squares that appear according to a sequence. In order to establish the times necessary for obtaining a good level of polymerization of the resin layer, the print cycle illustrated in FIG. 1 was carried out.

[0088] The exposure time for a single layer, i.e. the time interval in seconds in which the photosensitive resin is irradiated, was fixed equal to T1 up to reaching a total time TTOT equal to 4 times T1 (4T1). The wait time Ta, instead, is the time interval in which the light beam is absent (indicated with the black rectangle in FIG. 1).

[0089] The exposure parameters and the obtained results are illustrated in the following table 4.

TABLE-US-00004 TABLE 4 T1 (s) Ta Result R.sub.fot R2_1 (RAM20) 1.0 2.0 Only the first square polymerized (4T1) R.sub.fot R2_2 (RAM10) 2.5 2.0 All four squares Test 1 polymerized R.sub.fot R2_2 (RAM10) 1.0 2.0 All four squares Test 2 polymerized R.sub.fot R2_3 (EPR3) 2.5 2.0 No polymerization R.sub.fot C2 (COOP20) 2.0 2.0 Only the first Test 1 square polymerized (4T1) R.sub.fot C2 (COOP20) 5.0 2.0 All four squares Test 2 polymerized R.sub.fot C3 (COOP30) 2.0 2.0 Only the first Test 1 square polymerized (4T1) R.sub.fot C3 (COOP30) 4.0 2.0 All four squares Test 2 polymerized R.sub.fot G1 2.5 2.0 No polymerization R.sub.fot G2 2.0 2.0 All four squares polymerized

[0090] The exploratory tests led to the definition of the following parameters used in the print tests: [0091] Exposure time: 8 s [0092] Layer height: 0.2 mm [0093] Wait time: 5 s [0094] Activated immersion: 3 mm [0095] Immersion wait time: 3 s

EXAMPLE 3

Print Tests

[0096] The print tests of the 3D objects were attained with the photosensitive resins illustrated in the following table 5.

TABLE-US-00005 TABLE 5 Resin 2% BAPO 20% NVP Sudan I (g) (g) (g) (mg) R.sub.fot R2 (WASTE) 39.1 1 10 6 R.sub.fot C2 (COOP20) 117.0 3 30 18 R.sub.fot C3 (COOP30) 165.5 4.2 43 24 R.sub.fot G2 133.6 3.43 35 21

[0097] FIG. 2 illustrates the results obtained with the photosensitive resin R.sub.fot R2 with different doses of coloring agent and increasing level of detail.

[0098] In particular, from left to right, the concentration of coloring agent increases from 2.5 mg Sudan 1/50 mL of resin to 10 mg Sudan 1/50 mL with increments between the various tests of 1.25 mg of Sudan I. The exposure time for each 0.2 mm layer is 8 seconds. The penultimate test has an improved level of detail.

[0099] FIGS. 3A-D illustrate the results obtained with the photosensitive resin R.sub.fot G2.

[0100] FIGS. 4A-C illustrate the results obtained with the photosensitive resin R.sub.fot C2 and C3.