Light-curable composition

Abstract

A light-curable composition is provided which may be used as a photopolymerizable material in an additive manufacturing process. The additive manufacturing process involves heating the light-curable composition which has a viscosity at 20° C. of at least 20 Pa.Math.s. The light-curable composition includes a photopolymerizable matrix material, at least one thermoplastic polymer dissolved therein, and at least one photoinitiator. Polycaprolactone or a derivative thereof is used as the dissolved thermoplastic polymer.

Claims

1. A light-curable composition configured to be used as a photopolymerizable material in an additive manufacturing process, the process comprising heating said light-curable composition which has a viscosity at 20° C. of at least 20 Pa.Math.s, the light-curable composition comprising: a photopolymerizable matrix material, at least one thermoplastic polymer which essentially does not react with the photopolymerizable matrix material and does not participate in the polymerization process, and which is dissolved in the photopolymerizable matrix material, and at least one photoinitiator; wherein polycaprolactone or a derivative thereof is used as said dissolved thermoplastic polymer.

2. The light-curable composition according to claim 1, wherein said polycaprolactone or said derivative thereof has a number average molecular weight of at least 25,000 g/mol or at least 50,000 g/mol.

3. The light-curable composition according to claim 2, wherein said polycaprolactone or said derivative thereof has a number average molecular weight M.sub.n of at least 70,000 g/mol.

4. The light-curable composition according to claim 1, wherein said polycaprolactone or said derivative thereof is dissolved in said photopolymerizable matrix material at an amount of 2 to 30 wt %, based on 100 wt % of said matrix and said thermoplastic polymer taken together.

5. The light-curable composition according to claim 4, wherein said polycaprolactone or said derivative thereof is dissolved in said photopolymerizable matrix material at an amount of 5 to 15 wt %, based on 100 wt % of said matrix and said thermoplastic polymer taken together.

6. The light-curable composition according to claim 5, wherein said polycaprolactone or said derivative thereof is dissolved in said photopolymerizable matrix material at an amount of 10 wt %, based on 100 wt % of said matrix and said thermoplastic polymer taken together.

7. The light-curable composition according to claim 1, wherein polycaprolactone is used as said dissolved thermoplastic polymer.

8. The light-curable composition according to claim 1, wherein said photopolymerizable matrix material comprises at least one monofunctional reactive diluent and at least one di- or higher functional crosslinker.

9. The light-curable composition according to claim 8, wherein one or more (meth)acrylates is/are used as said reactive diluent and/or crosslinker.

10. The light-curable composition according to claim 8, wherein said at least one reactive diluent accounts for 30 to 80 wt % and said at least one crosslinker accounts for 70 to 20 wt % of said polymerizable matrix material.

11. The light-curable composition according to claim 8, wherein said at least one reactive diluent has a viscosity at 20° C. of not more than 0.1 Pa.Math.s.

12. The light-curable composition according to claim 8, wherein an oligomer having a number average molecular weight M.sub.n of at least 400 g/mol is used as said crosslinker.

13. The light-curable composition according to claim 1, wherein the composition has a viscosity at 20° C. of at least 50 Pa.Math.s.

14. The light-curable composition according to claim 13, wherein the composition has a viscosity at 20° C. of at least 80 Pa.Math.s.

15. The light-curable composition according to claim 1, wherein the light-curable composition comprises at least one further component selected from the group consisting of thermal initiators, dyes, fillers, and modifiers.

16. The light-curable composition according to claim 8, wherein an oligomer having a number average molecular weight M.sub.n of at least 1,000 g/mol is used as said crosslinker.

17. The light-curable composition according to claim 8, wherein an oligomer having a number average molecular weight M.sub.n of at least 5,000 g/mol is used as said crosslinker.

18. The light-curable composition according to claim 8, wherein an oligomer having a number average molecular weight M.sub.n of at least 10,000 g/mol is used as said crosslinker.

Description

EXAMPLES

(1) The present invention will be described below referring to specific exemplary embodiments and comparative examples as well as to the appended drawings that show the following:

(2) FIG. 1 shows the results of an impact resistance test to which various photopolymers according to the invention and photopolymers produced in comparative examples were subjected; and

(3) FIG. 2 shows the development of the viscosity of a composition for use according to Example 5 of the present invention.

Examples 1 to 4, Comparative Examples 1 to 6

(4) Compositions for the use according to the invention were produced with the proportions of components listed in Table 1 on the next page; 0.5 phr (“parts per hundred rubber”, i.e., parts per 100 parts by weight of the matrix material) of Ivocerin, a photoinitiator available from Ivoclar Vivadent, were added to each of them.

(5) 15 wt % of the respective soluble thermoplastic or polycaprolactone were added to each of the compositions of all Comparative Examples and the composition of Example 1 that comprised the matrices 1 to 3, while only 10 wt % of polycaprolactone were added to each of the compositions of the invention of Examples 2 to 4 that contained matrix 4 (in all cases based on 100 wt % of the matrix and the thermoplastic taken together).

(6) TABLE-US-00001 TABLE 1 Example Reactive diluent crosslinker thermoplastic Matrix 1, M1 66.7% IBMA .sup.1) 33.3% SR834 .sup.2) — Comparative Example 1, V1 ″ ″ 15% RB810 .sup.3) Comparative Example 2, V2 ″ ″ 15% RB830 .sup.4) Comparative Example 3, V3 ″ ″ 15% SBR BL .sup.5) Comparative Example 4, V4 ″ ″ 15% SBR SL .sup.6) Comparative Example 5, V5 ″ ″ 15% SBR SE .sup.7) Matrix 2, M2 90% HEMA .sup.8) 10% SR348L .sup.9) — Comparative Example 6, V6 ″ ″ 15% TPU .sup.10) Matrix 3, M3 70% IBMA 30% EO(30)BPA-DMA .sup.11) — Example 1, B1 ″ ″ 15% PCL 80 .sup.12) Matrix 4, M4 50% IBMA 30% EO(30)BPA-DMA — 20% XR741 .sup.13) Example 2, B2 ″ 30% EO(30)BPA-DMA 10% PCL 25 .sup.14) 20% XR741 .sup.13) Example 3, B3 ″ 30% EO(30)BPA-DMA 10% PCL 50 .sup.15) 20% XR741 .sup.13) Example 4, B4 ″ 30% EO(30)BPA-DMA 10% PCL 80 20% XR741 .sup.13) .sup.1) IBMA: isobornyl methacrylate from Sigma Aldrich .sup.2) SR834: tricyclodecane dimethanol dimethacrylate from Sartomer .sup.3) RB810: syndiotactic 1,2-polybutadiene from JSR, 90% 1,2-bounds, Mn 120,000 g/mol .sup.4) RB830: syndiotactic 1,2-polybutadiene from JSR, 93% 1,2-bounds, Mn 120,000 g/mol .sup.5) SBR BL: styrene butadiene copolymer from Lanxess, Buna BL 30-4548, 48% styrene, 30% in block form .sup.6) SBR SL: styrene butadiene copolymer from Lanxess, Buna SL 4525-0, 25% styrene, obtained by solution polymerization .sup.7) SBR SE: styrene butadiene copolymer from Lanxess, Buna SE 1502, 23.5% styrene, obtained by emulsion polymerization .sup.8) HEMA: hydroxyethyl methacrylate from Sigma Aldrich .sup.9) SR348L: ethoxylated (2) bisphenol A dimethacrylate from Sartomer .sup.10) TPU: thermoplastic polyurethane from Covestro, Desmopan DP 85085A, Mn 160,000 g/mol .sup.11) EO(30)BPA-DMA: ethoxylated (30) bisphenol A dimethacrylate from Sigma Aldrich, Mn 1,700 g/mol .sup.12) PCL 80: polycaprolactone from Perstorp, Capa 6800, Mn 80,000 g/mol .sup.13) XR741: difunctional aliphatic polyesterurethane methacrylate from Dymax, Bomar XR-741MS .sup.14) PCL 25: polycaprolactone from Perstorp, Capa 6250, Mn 25,000 g/mol .sup.15) PCL 50: polycaprolactone from Perstorp, Capa 6506, Mn 50,000 g/mol

(7) To simulate a generative manufacturing process, the composition was cast into moulds at a temperature of 80° C. and immediately exposed for 500 sec using an Uvitron Intelliray 600 UV chamber operated at full capacity and thus cured. The samples were demoulded, turned around by 180° and exposed a second time for 500 sec. The sample body was then polished to a width of 4 mm using grit 1000 abrasive paper and conditioned according to ISO 291 for at least 88 h at 23° C. and 50% humidity. The sample body of matrix M2 and of Comparative Example 6 were conditioned for 14 days. After that, impact resistance was tested according to DIN 53435, the results being shown in FIG. 1.

(8) The figure clearly shows that most of the soluble thermoplastics of the Comparative Examples were not able to achieve a significant improvement in impact resistance. Only the thermoplastic polyurethane of Comparative Example 6 did significantly increase the impact resistance of matrix material 3. This thermoplastic, however, had a number average molecular weight M.sub.n of 160,000 g/mol and was contained at a proportion of 15 wt %.

(9) The polycaprolactone in Example 1, by way of comparison, that was also contained at a proportion of 15 wt % increased the impact resistance of matrix material 3 to a similar extent, although its number average molecular weight M.sub.n only amounted to 80,000 g/mol.

(10) In the compositions of Examples 2 to 4, polycaprolactone was only contained at a proportion of 10 wt %, which is why the polycaprolactone “PCL 25” in Example 2 having a number average molecular weight M.sub.n of 25,000 g/mol only resulted in a minor improvement in the impact resistance of matrix material 4. The caprolactones of Examples 3 and 4, on the other hand, having molecular weights M.sub.n of 50,000 and 80,000 g/mol, respectively, resulted in a significant improvement in the impact resistance of the matrix that did not comprise any thermoplastic.

(11) Comparison of Water Absorption

(12) As the other soluble thermoplastics from the Comparative Examples had already proved hardly promising, only the sample bodies of Comparative Example 6 (V6) comprising a thermoplastic polyurethane and of Example 4 (B4) comprising polycaprolactone having a molecular weight of 80,000 g/mol were included in a test examining their water absorption. In this test, the two sample bodies were stored at 100% humidity for 8 days, after which the weight of V6 was found to have increased by 17.0%, while that of B4 had remained almost the same. Even after B4 had been immersed in water for 28 days, a weight increase of only 2.9% was observed, which confirms that, in terms of water absorption, the composition of Example 4 that contains polycaprolactone was clearly superior to that of Comparative Example 6 that comprised polyurethane as the thermoplastic and significantly higher polar matrix components, which are indispensable for dissolving polyurethane.

Example 5

(13) The polycaprolactone “PCL 80” having a number average molecular weight M.sub.n of 80,000 g/mol that had achieved the best results until then was used in a 3D print experiment that was identical to 3D printing processes in practice. The following compositions were produced, both the reactive diluent and the crosslinker components of the matrix were supplied comprising MEHQ as polymerization inhibitor.

(14) TABLE-US-00002 TABLE 2 Example reactive diluent crosslinker thermoplastic additives Matrix 5 45% IBMA .sup.1) 27% EO(30)BPA-DMA .sup.3) — 150 ppm MEHQ .sup.2) 18% XR741 .sup.4) 200 ppm MEHQ Example 5 45% IBMA .sup.1) 27% EO(30)BPA-DMA .sup.3) 10% PCL 80 .sup.5) 0.15 phr Ivocerin 150 ppm MEHQ .sup.2) 18% XR741 .sup.4) 0.5 phr ABCN .sup.6) 200 ppm MEHQ 0.075 phr SY .sup.7) .sup.1) IBMA: isobornyl methacrylate from Sigma Aldrich .sup.2) MEHQ: hydroquinone methylether (4-methoxyphenol), polymerization inhibitor from Sigma Aldrich .sup.3) EO(30)BPA-DMA: ethoxylated (30) bisphenol A dimethacrylate from Sigma Aldrich, Mn 1,700 g/mol .sup.4) XR741: difunctional aliphatic polyesterurethane methacrylate from Dymax, Bomar XR-741MS .sup.5) PCL 80: polycaprolactone from Perstorp, Capa 6800, Mn 80,000 g/mol .sup.6) ABCN: 1,1′-azobis(cyclohexane carbonitrile), a thermal initiator from Sigma Aldrich .sup.7) SY: Sudan Yellow 177, a dye from John Hogg

(15) 45 g of the two crosslinkers and 45 g of the reactive diluent were stirred for 30 min at 60° C. in a heated vessel equipped with a mechanical stirrer. After that, 10 g polycaprolactone were added, and the mixture was heated to 80° C., stirred for 6 hours at this temperature and then cooled to room temperature. The then solid mixture was removed from the vessel and transferred into a plastic cup where it was again heated to 80° C. and the photoinitiator (Ivocerin), the thermal initiator (ABCN) and the dye (SY) were added thereto. The mixture was homogenized for 10 min in a dual asymmetric centrifuge at 3,500 rpm.

(16) The thus obtained composition was solid at room temperature and had an (uncorrected) melting point that was determined by means of DSC (heating rate: 10 K/min) of approx. 42.5° C. The viscosity was determined using a cone-plate viscosimeter having a diameter of 25 mm and a test gap of 49 μm, at a shear rate of 50 s.sup.−1 and a heating rate of 0.05° C./s. The temperature-dependent development of the composition's viscosity is shown in FIG. 2.

(17) The material was then processed using a heated DLP (“digital light processing”) 3D printer at 60° C. In a tensile test according to ISO 527 with test bodies of type 5B, the thus printed test bodies had excellent tensile properties, i.e. an elongation at break of approx. 100%, and excellent thermo-mechanical properties (1 Hz and an amplitude of 20 μm) as regards dynamic modulus and damping (tangens delta) when tested on a Texas Instruments Dynamic Mechanical Analyzer DMA 2980 at −50 to 150° C.

(18) The above examples of the present invention clearly show the advantages of the use of the invention of polycaprolactones as soluble thermoplastics in light-curable compositions for generative manufacturing processes and 3D printing.