RESIN COMPOSITION FOR 3D PRINTING

Abstract

A radiation-curable resin composition, comprising from 0 to 30% by weight of one or more oligomers; from 15 to 80% by weight of one or more monomers; from 10 to 80% by weight of a filler mixture; from 0.1 to 5% by weight of one or more photoinitiators;
wherein the filler mixture includes: from 39.9 to 90% by weight of first particles having a grain size d50.sub.vol of 3 to 20 μm; from 9.9 to 60% by weight of second particles having a grain size d50.sub.vol of 0.5 to 1 μm; from 0.1 to 5% by weight of nanoparticles having a BET surface area within a range of from 10 to 100 m.sup.2/g.

Claims

1. A radiation-curable resin composition, comprising from 0 to 30% by weight of one or more oligomers; from 15 to 80% by weight of one or more monomers; from 10 to 80% by weight of a filler mixture; from 0.1 to 5% by weight of one or more photoinitiators; wherein the filler mixture includes: from 39.9 to 90% by weight of first particles having a grain size d50.sub.vol of 3 to 20 μm; from 9.9 to 60% by weight of second particles having a grain size d50.sub.vol of 0.5 to 1 μm; from 0.1 to 5% by weight of nanoparticles having a BET surface area within a range of from 10 to 100 m.sup.2/g.

2. The radiation-curable resin composition according to claim 1, wherein said first or said second particles or both are silanized.

3. The radiation-curable resin composition according to claim 1, wherein said first particles are spherical in shape as measured with a QICPIC® device.

4. The radiation-curable resin composition according to claim 1, wherein said oligomers comprise free-radically polymerizable groups.

5. The radiation-curable resin composition according to claim 1, wherein said monomers have at least one free-radically polymerizable ethylenic double.

6. The radiation-curable resin composition according to claim 1, wherein said first and second particles of the filler mixture are independently fillers selected from the group consisting of amorphous silicon dioxide, crystalline silicon dioxide, feldspar, mica, anhydrite, and mixtures thereof.

7. The radiation-curable resin composition according to claim 6, wherein said feldspar is selected from the group consisting of potash feldspar, sodium feldspar, so-called feldspathoids, and mixtures thereof.

8. The radiation-curable resin composition according to claim 1, wherein said photoinitiator is selected from substances that are active within a wavelength range of from 355 to 405 nm.

9. The radiation-curable resin composition according to claim 1, wherein said resin composition without a filler mixture has a viscosity within a range of from 10 to 1000 mPa.Math.s, as measured at 25° C. and at a shear rate of 10 s.sup.−1 with a plate-plate geometry.

10. The radiation-curable resin composition according to claim 1, wherein said radiation-curable resin composition has a viscosity of at most 3000 mPa.Math.s at a shear rate of 10 s.sup.−1, and at most 15,000 mPa.Math.s at a shear rate of 0.1 s.sup.−1, respectively measured at 25° C. and with a plate-plate geometry.

11. The radiation-curable resin composition according to claim 1, wherein said resin composition does not exhibit any sedimentation of the filler mixture after storage at 25° C. for at least 3 months, as measured by visual inspection.

12. A radiation-cured resin composition obtainable by radiation-curing the resin composition according to claim 1.

13. The radiation-cured resin composition according to claim 12, having a flexural modulus of elasticity according to ISO 178 within a range of from 6,000 to 12,000 MPa.

14. The radiation-curable resin composition according to claim 4, wherein said free-radically polymerizable groups are (meth)acrylate groups.

15. The radiation-curable resin composition according to claim 5, wherein said monomers having at least one free-radically polymerizable ethylenic double bond comprise (meth)acrylate groups.

16. The radiation-curable resin composition according to claim 8, wherein said photoinitiator is selected from substances from the phosphine oxide class of substances.

17. The radiation-cured resin composition according to claim 12, having a heat deflection temperature HDT A according to ISO 75 of at least 100° C.

Description

EXAMPLES

Abbreviations and Parameters Employed

[0106]

TABLE-US-00001 MST methacryloxypropyltrimethoxysilane a-SiO.sub.2 amorphous silicon dioxide E.sub.f flexural modulus of elasticity or flexural modulus in Megapascal (MPa) according to ISO 178 ε.sub.fB bending strain at break in percent (%)according to ISO 178 σ.sub.fB bending stress at break in Megapascal (MPa)according to ISO 178 HDT A heat deflection temperature in degree centigrade (° C.) according to method A of ISO 75 n.d. not determined

Preparation of the Resin (for Examples 4 to 7)

[0107] The photoinitiator GENOCURE TPO is completely dissolved in the monomer SARTOMER SR 351 at room temperature and with stirring. Subsequently, the remaining components of the resin (SARTOMER SR 306, GENOMER 4425, EPDXY METHACRYLATE 97-053) are added. The mixture is stirred until a homogeneous mixture is obtained.

Preparation of the Resin Compositions (for Examples 4 to 7)

[0108] A DAC mixer from the company Hauschild (Speedmixer DAC 400 FVZ) was used for preparing the resin compositions. In a plastic beaker suitable for the Speedmixer (750 ml), 60 g of the resin (50% by weight of the total amount of resin) and 90 g of the filler mixture (50% by weight of the total amount of the filler mixture) are charged, and dispersed at 2,200 rpm for 2 min Subsequently, the remaining amount of the filler mixture (50% by weight of the total amount) is added, and again dispersed at 2,200 rpm for 2 min. In the third step, the remaining amount of the resin (50% by weight of the total amount) is added, followed by another 2 min of dispersing at 2,200 rpm. The resulting resin composition has a filler content of 60% by weight.

Viscosity Measurements

[0109] The viscosity of resins and resin compositions was determined with a rheometer MCR 102 from the company Anton Paar. The following setting was selected:

[0110] Geometry=50 mm plate-plate, measuring temperature=25° C., shear rates=0.1 s.sup.−1 and 10 s.sup.−1.

3D Printing of Test Specimens of the Cured Resin Composition

[0111] The radiation-curable resin compositions are printed to test specimens of the cured resin composition using a printer of the type SolFlex 650 of the company Way2Production (W2P).

Post-Curing of the Test Specimens of the Cured Resin Composition

[0112] After the printing, the test specimens of the cured resin composition are after-cured using a UV lamp (company Kulzer HiLite Power, emitted wavelength=390-540 nm) on both sides for 180 s.

Mechanical Properties of the Cured Resin Composition

[0113] The test specimens have the following dimensions: length 1=(80±2) mm, width b=(10±0.2) mm, thickness h=(4±0.2) mm

[0114] The bending properties are determined according to ISO 178.

[0115] The heat deflection temperature is determined according to ISO 75, method A. The heating rate of the oil bath is 50 K/h.

Example 1 (Comparison)

[0116] The commercial resin Prototype Clear of the company Way2Production was filled with 50% by weight of an amorphous silicon dioxide (d50=5 μm) according to the principle of the method described above. The resin composition has a viscosity of 5,000 mPa.Math.s (shear rate=0.1 s.sup.−1), or of 10,000 mPa.Math.s (shear rate=10 s.sup.−1). Because of the high viscosity, this resin composition is not suitable for 3D printing.

Example 2 (Comparison)

[0117] By analogy with Example 1. Instead of the unsilanized filler, an amorphous silicon dioxide silanized with MST (d50=5 μm) was used.

[0118] The resin composition shows a good flowability. The viscosity is 4,000 mPa.Math.s (shear rate=0.1 s.sup.−1), or 5,700 mPa.Math.s (shear rate=10 s.sup.−1). After storage at 50° C. for 6 hours already, the resin composition shows clearly visible sedimentation. Thus, this resin composition is not permanently stable when stored.

[0119] A freshly prepared sample of the resin composition was further processed into test specimens of the cured resin composition according to the above mentioned methods. The mechanical properties can be seen from Table 1.

Example 3 (Comparison)

[0120] By analogy with Example 2. Instead of an MST-silanized filler, two MST-silanized fillers having different grain size distributions were used (80% by weight of an amorphous silicon dioxide with a d50 of 5 μm, 20% by weight of an amorphous silicon dioxide with a d50 of 1 μm).

[0121] The resin composition shows a good flowability. The viscosity is 4,200 mPa.Math.s (shear rate=0.1 s.sup.−1), or 4,400 mPa.Math.s (shear rate=10 s.sup.−1). After storage at 50° C. for 6 hours already, the resin composition shows clearly visible sedimentation. Thus, this resin composition is not permanently stable when stored.

[0122] A freshly prepared sample of the resin composition was further processed into test specimens of the cured resin composition according to the above mentioned methods. The mechanical properties can be seen from Table 1.

TABLE-US-00002 TABLE 1 Parameter Unit Example 1 Example 2 Example 3 Bending properties according to ISO 178 E.sub.f MPa n.d. 6,500 6,400 ε.sub.fB MPa n.d. 142 154 σ.sub.fB % n.d. 3.1 3.6 Heat deflection temperature according to ISO 75 HDT A ° C. n.d. 70 71

[0123] The cured resin compositions from Examples 2 and 3 show very good stresses at break and strains at break. However, the flexural modulus is still too low for many applications. The same holds for the heat deflection temperature.

Examples 4 to 7

[0124] For the Examples 4 to 7, a self-formulated resin with a low viscosity of <100 MPa.Math.s (shear rate=10 s.sup.−1) that was prepared by the above described method was used instead of a commercially available resin. By analogy with the preceding Examples 1 to 3, filler mixtures of different compositions were incorporated into the resin by the above described method. The resulting radiation-curable resin compositions were characterized in terms of their viscosity. From the resin composition of Example 7 according to the invention, test specimens were produced by the above described 3D printing method. The test specimens of the cured resin composition were characterized in terms of their bending properties and heat deflection temperature. Details can be seen from Table 2.

[0125] Although the resin compositions of Examples 4 and 6 are stable when stored for an extended period of time (no sedimentation), their viscosity is rather a tad high in view of processing in 3D printing. In contrast, the resin composition of Example 5 shows good flow properties, but does not offer permanent stability towards sedimentation. The resin composition of Example 7 according to the invention is both readily processed (good flow properties) and stable when stored (no sedimentation).

[0126] In addition, the cured resin composition of Example 7 according to the invention shows good bending properties and a high heat deflection temperature.

TABLE-US-00003 TABLE 2 Example 4 Example 5 Comparison Comparison Example 6 Example 7 [% by weight] [% by weight] [% by weight] [% by weight] Formulation Function/Unit total // relative total // relative total // relative total // relative SARTOMER SR 306 Monomer 15 15 15 15 GENOMER 4425 Oligomer 5 5 5 5 Epoxy Methacrylate 97-053 Monomer 5 5 5 5 SARTOMER SR 351 Monomer 13.5 13.5 13.5 13.5 GENOCURE TPO Photoinitiator 1.5 1.5 1.5 1.5 Total filler content 60 100 60 100 60 100 60 100 a-SiO.sub.2, MST-silanized, first particles of 48 80 d50 = 7 μm filler mixture Spherical a-SiO.sub.2, MST- first particles of 48 80 30 50 48 60 silanized, d50 = 5 μm filler mixture a-SiO.sub.2, MST-silanized, second particles of 12 20 12 20 29.5 49.2 11.5 19.2 d50 = 1 μm filler mixture a-SiO.sub.2, MST-silanized, nanoparticles of 0.5 0.8 0.5 0.8 BET 100 m.sup.2/g filler mixture Total % by weight 100 100 100 100 Viscosity at 0.1 s.sup.−1 mPa .Math. s 67,000 6,000 31,000 12,000 Viscosity at 10 s.sup.−1 mPa .Math. s 3,000 2,000 2,500 2,000 Bending properties of the radiation-cured resin compositions according to ISO 178 E.sub.f MPa n.d. n.d. n.d. 9,000 ε.sub.fB MPa n.d. n.d. n.d. 67 σ.sub.fB % n.d. n.d. n.d. 0.8 Heat deflection temperature of the radiation-cured resin compositions according to ISO 75 HDT A ° C. n.d. n.d. n.d. 170 Processability viscosity too high viscosity o.k. viscosity rather high viscosity very good Storage stability no sedimentation not stable towards no sedimentation no sedimentation sedimentation