SOLUBLE SUPPORT MATERIALS FOR ADDITIVE MANUFACTURING

Abstract

The present invention refers to a method for additive manufacturing a silicone elastomer article using a 3D printer selected from an extrusion 3D printer and a 3D jetting printer, in which a soluble support material composition V is used, which comprises: (A) at least one polyorganosiloxane, (B) at least one polyether or polymer containing polyether moiety, (C) silica; to a silicone elastomer article obtainable by the method of present invention; and to the use of a support material composition V for 3D printing a support, preferably by extrusion.

Claims

1. A method for additive manufacturing a silicone elastomer article using a 3D printer selected from an extrusion 3D printer and a 3D jetting printer, said method comprising: 1) printing at least one part of a support material composition V, wherein the support material composition V comprises: (A) at least one polyorganosiloxane A, optionally linear polyorganosiloxane; (B) at least one polyether or polymer containing polyether moiety B; (C) silica C, optionally selected from fumed silica, precipitated silica or the mixture thereof; 2) printing at least one part of a building material composition, which is a crosslinkable silicone composition X precursor of the silicone elastomer article; 1) and 2) being done simultaneously or successively, and when 1) and 2) are done successively, 1) can be performed before 2), or 2) can be performed before 1); 3) optionally repeating 1) and/or 2); and 4) allowing the crosslinkable silicone composition X precursor of the silicone elastomer article to crosslink, optionally by heating, to obtain a silicone elastomer article; 5) removing the support material, optionally, by dissolution in a solvent, optionally in water, and/or mechanically.

2. The method according to claim 1, wherein the at least one polyorganosiloxane A is at least one polyorganosiloxane oil A, optionally at least one linear polyorganosiloxane oil, which is a linear homopolymer or copolymer which has, per molecule, monovalent organic substituents, which are identical to or different from one another, bonded to the silicon atoms, and which are selected from the group consisting of C.sub.1-C.sub.6 alkyl radicals, C.sub.3-C.sub.8 cycloalkyl radicals, C.sub.6-C.sub.10 aryl radicals and C.sub.7-C.sub.15 alkylaryl radicals.

3. The method according to claim 1, wherein the polyorganosiloxane A is selected from vinyl polysiloxane, hydroxy polysiloxane or mixture thereof, optionally selected from vinyl terminated polydimethylsiloxane, hydroxy terminated polydimethylsiloxane or a mixture thereof.

4. The method according to claim 1, wherein the polyorganosiloxane A has a dynamic viscosity from about 1 to 50 000 000 mPa.Math.s at 23° C., optionally from about 10 to 10 000 000 mPa.Math.s at 23° C., optionally about 50 to 1 000 000 mPa.Math.s at 23° C.

5. The method according to claim 1, wherein the silica C) is selected from treated silica or non-treated silica, optionally selected from treated silica.

6. The method according to claim 1, wherein said support material composition X comprises: 1% to 99% by weight, optionally 3% to 95% by weight and optionally 5 to 85% by weight of polyorganosiloxane A, and/or 0.01 to 99% by weight, optionally 0.5% to 90%, optionally 1 to 85% by weight and optionally 3 to 80% by weight of component B, and/or 0.5% to 60% by weight, optionally 1% to 40%, optionally 2% to 30%, and optionally 5% to 20% of silica C, relative to the total weight of the support material composition X.

7. The method according to claim 1, wherein said support material composition X has a thixotropic index of 2 to 100, optionally 3 to 60, and optionally 3.5-50.

8. A silicone elastomer article obtainable by the method according to claim 1.

9. A method for additive manufacturing a silicone elastomer article and a support using a 3D printer selected from an extrusion 3D printer and a 3D jetting printer, said method comprising: 1) printing at least one part of the support with a support material composition V, wherein the support material composition V comprises: (A) at least one polyorganosiloxane A, optionally linear polyorganosiloxane; (B) at least one polyether or polymer comprising polyether moiety B; (C) silica C, optionally selected from fumed silica, precipitated silica or a mixture thereof; 2) printing at least one part of a building material composition, which is a crosslinkable silicone composition X precursor of the silicone elastomer article; 1) and 2) being done simultaneously or successively, and when 1) and 2) are done successively, 1) can be performed before 2), or 2) can be performed before 1); 3) optionally, repeating 1) and/or 2); and 4) allowing the crosslinkable silicone composition X precursor of the silicone elastomer article to crosslink, optionally by heating, to obtain a silicone elastomer article.

10. A product comprising a support material composition V in 3D printing, optionally by using a 3D printer selected from an extrusion 3D printer and a 3D jetting printer, wherein the support material composition V comprises: (A) at least one polyorganosiloxane A, optionally linear polyorganosiloxane; (B) at least one polyether or polymer containing polyether moiety B; (C) silica C, optionally selected from fumed silica, precipitated silica or a mixture thereof.

11. A support material composition V comprising: (A) at least one polyorganosiloxane A, optionally linear polyorganosiloxane; (B) at least one polyether or polymer containing polyether moiety B; (C) silica C, optionally selected from fumed silica, precipitated silica or a mixture thereof.

Description

DESCRIPTION OF THE FIGURES

[0290] FIG. 1 is a photograph showing a silicone elastomer article formed by the building material before removing the support material.

[0291] FIG. 2 is a photograph showing a silicone elastomer article formed by the building material after removing the support material.

MODE OF CARRYING OUT THE INVENTION

[0292] The scope and interest of the invention will be better understood based on the following examples which are intended to illustrate certain embodiments of the present invention and are non-limitative.

Examples

[0293] The raw materials of the support material used in the examples are listed in the following Table 1, and formulas and test results of the support material can be found in Tables 2-1 and 2-2.

TABLE-US-00001 TABLE 1 The description of structure of raw materials of the support material Raw materials Chemical description or structure A-1 Non-reactive methyl polysiloxane, viscosity: 50 mPa .Math. s A-2 Non-reactive methyl polysiloxane, viscosity: 1000 mPa .Math. s A-3 Vinyl terminated Polydimethylsiloxane, viscosity: 100000 mPa .Math. s, vinyl content: 0.08 wt % A-4 Hydroxy terminated Polydimethylsiloxane, viscosity: 14000 mPa .Math. s Hydroxy content: 0.014 wt % B-1 CAS NO.: 68937-55-3, Siloxanes and Silicones, dimethyl, 3-hydroxypropyl methyl, ethoxylated propoxylated B-2 CAS NO.: 69011-36-5 Alcohol iso-C13, poly (12) ethoxylate B-3 CAS NO.: 9004-81-3 Polyethylene glycol monolaurate C-1 CAS NO.: 112945-52-5 Particle size (D50) is 10 μm, specific surface area is 190 m2/g ACEMATT ® 3300 is an advanced polymer-treated thermal silica C-2 Fumed silica treated by D4, specific surface area is about 235 m.sup.2/g

TABLE-US-00002 TABLE 2-1 Formulas and test results of silicone support materials Raw Example Example Example Example Example Example Example Example Example materials 1 2 3 4 5 6 7 8 9 A-1 0 0 0 0 0 0 0 0 40 A-2 0 80 0 60 80 85 80 0 0 A-3 5 0 0 0 0 0 0 70 0 A-4 0 0 80 0 0 0 0 0 0 B-1 80 10 10 0 0 5 0 25 50 B-2 0 0 0 30 10 0 0 0 0 B-3 0 0 0 0 0 0 10 0 0 C-1 15 10 10 10 10 10 0 5 10 C-2 0 0 0 0 0 0 10 0 0 Total 100 100 100 100 100 100 100 100 100 Test results viscosity 629000 610000 1780000 860000 775000 1970000 946000 392000 1250000 η (mPa .Math. s) at [0.5 s − 1], 23° C. viscosity 64000 32000 100000 40000 29000 47000 27000 105000 80000 η (mPa .Math. s) at [25 s − 1], 23° C. Thixotro 10 19 18 21 27 42 35 4 16 pic index Status thixotropic thixotropic thixotropic thixotropic thixotropic thixotropic thixotropic thixotropic thixotropic Dissolution 0.5 0.5 0.5 0.5 0.67 168 168 1 0.5 time in water/ h, 23° C.

TABLE-US-00003 TABLE 2-2 Formulas and test results of silicone support materials Comparative Comparative Comparative Example 1 Example 2 Example 3 Raw materials A-1 0 0 0 A-2 90.91 0 0 A-3 0 0 0 A-4 0 0 0 B-1 0 90.91 0 B-2 0 0 0 B-3 0 0 90.91 C-1 9.09 9.09 9.09 C-2 0 0 0 Total 100 100 100 Test results Viscosity, mPa .Math. s, 26000 26500 6000 (5#, 10 rpm, 23° C.) Status flowable flowable flowable

[0294] Experiments

[0295] In example 1, all of the raw materials are mixed according to weight ratio as indicated in the Table 2-1. Specifically, 5 parts of A-3 and 80 parts of B-1 are mixed with 15 parts of silica C-1 sufficiently, to obtain the support material composition of example 1. Examples 2-9 and comparative examples 1-3 are also prepared in a similar process according to the weight ratio as indicated in the Tables 2-1 and 2-2.

[0296] Properties Assessment

[0297] According to the invention, assessment results of the samples are listed in the Table 2-1 and Table 2-2.

[0298] Rheological test: A rotational rheometer (Haake Rheometer) is used to define the rheological behavior of samples based on examples 1-9. A thixotropic test is performed in two parts at 25° C. using cone-plate (35 mm, 1°, gap=52 μm) in order to keep a constant shear rate in samples. The first part is a pre-shear test in order to destroy the material's microstructure as in 3D printing conditions (3 s at 5 s.sup.−1). The second part is a time sweep test in order to define the thixotropic performance of samples. An equivalent shear thinning test was performed to define a “viscosity ratio” which allows users to evaluate the material's performance in 3D printing. The “ratio” is calculated with the dynamic viscosity at low and high shear rate: 0.5 and 25 s.sup.−1 respectively. A high value of “viscosity ratio” means that material is able to product 3D objects with high quality.

[0299] In this method, the support materials of the present examples show the adequate rheological properties necessary to avoid collapse or deformation of the silicone elastomer articles at room temperature before complete curing. Preferably, the “thixotropic index” of the support material composition is defined as the ratio of the dynamic viscosity at low (0.5 s.sup.−1) and high shear rate (25 s.sup.−1). The higher thixotropic index means the better thixotropic performance of the support materials. Generally, the thixotropic index of more than or equal to 2 is well for the support material.

[0300] Viscosity test: According to ASTM D445, the viscosity of the samples based on comparative examples 1-3 is tested at 23° C., the detail of testing conditions can be seen in the table 2-2.

[0301] The above testing methods are employed to show if the samples can be used as support materials. Generally, the status of “thixotropic” as determined by the viscometer is a precondition for good shaping of support materials. The status of “flowable” as determined by the viscometer offers a proof that samples from comparative examples cannot keep good shape well.

[0302] Dissolution test: 3 g sample of the support material is put into 30 g of water and left to stand until the sample is completely dissolved (no obvious agglomeration was seen in the solution). Dissolution time can be seen in Table 2-1.

[0303] The inventors also test the dissolution time of the support material sample in organic solvents such as isopropanol and cyclohexane. In a similar way, for example, 3 g sample of the support material from example 2 is put into 30 g of isopropanol and 30 g hexane respectively and left to stand until the sample is completely dissolved (no obvious agglomeration was seen in the solution). Dissolution time in isopropanol and in hexane are all 0.5 h.

[0304] Dissolution property in solvent such as in organic solvents or in water is a key parameter in removing support materials. Proper support materials can be removed completely and will not have an adverse effect on building materials. It can be seen from the above tests that the support material according to the present invention has a suitable dissolution time in water, isopropanol and hexane, indicating that the support material of the present invention can be easily removed by a solvent, especially water.

[0305] A support material requires suitable thixotropic property during printing process meanwhile it can be removed easily such as dissolution in water or organic solvent quickly. To achieve the target, the combination of the components A, B and C plays a key role in the support material. In the examples, the combination of the components A, B and C exhibits ideal effect such as good thixotropy and fast dissolution speed in water or organic solvent. The support materials in the comparative examples cannot exhibit good thixotropy due to absence of component A or B.

[0306] 3D Printing Process

[0307] The 3D printing process is carried out by using a 3D printer based on extrusion process. The Printer has been equipped with two extrusion systems and two nozzles. One extrusion system is for a building material, the other one is for a support material.

[0308] The building material is prepared as below.

[0309] Raw materials of the building material composition are mixed according to weight ratio. 57.28 parts of vinyl terminated Polydimethylsiloxane (viscosity: 1500 mPa.Math.s, vinyl content: 0.26 wt %) and 7.05 parts of vinyl terminated Polydimethylsiloxane (viscosity: 600 mPa.Math.s, vinyl content: 0.38 wt %) are mixed with 24.59 parts of treated silica (CAS NO: 68988-89-6). 0.36 part of 2,4,6,8-Tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane (CAS NO.: 2554-06-5) is added and then mixed sufficiently. 2.16 parts of Poly(methylhydrogeno)(dimethyl)siloxane with SiH groups in-chain and end-chain (α/ω) (viscosity: 300 μmPa.Math.s, SiH content: 4.75 wt %), 1.72 parts of Poly(methylhydrogeno)(dimethyl)siloxane with SiH groups in-chain and end-chain (α/ω) (viscosity: 25 μmPa.Math.s, —SiH content: 20 wt %) and 1.72 parts of Poly(methylhydrogeno)(dimethyl)siloxane with SiH groups in-chain and end-chain (α/ω) (viscosity: 8.5 mPa.Math.s, SiH content: 5.5 wt %), are added and stirred, following with 0.017 part of catalyst Platinum(0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane (Pt content: 10 wt %) and 2 part of vinyl terminated methyl phenyl polysiloxane (viscosity: 800 mPa.Math.s, phenyl content: 15 wt %, refractive index: 1.46) to obtain polyaddition build materials. The viscosity of the build materials is 790000 mPa.Math.s (7#, 2 rpm, 23° C.) and 161400 mPa.Math.s (7#, 20 rpm, 23° C.)). The ratio of viscosities at different shear force is 4.9, which indicates the build material can be extruded via printer nozzle and keep shape very well.

[0310] The support material is prepared based on example 2 from Table 2-1.

[0311] Printing process is as follows:

[0312] I. Loading the building material and the support material into extruding systems respectively. The nozzle diameter used is 0.4 mm. The distance between the nozzle and the substrate is about 0.4 mm;

[0313] II. Level adjusting the printing platform and setting printing parameters;

[0314] III. Printing a silicone elastomer article as follows:

[0315] 1) printing at least one part of the support material composition as defined in example 2 from Table 2-1,

[0316] 2) printing at least one part of the building material composition as defined above, steps 1) and 2) being done successively, and step 2) is performed before step 1)

[0317] 3) repeating step 1) and step 2) respectively multiple times according to the desired shape of the final article;

[0318] 4) allowing the building material composition to crosslink at room temperature for 24 hours;

[0319] 5) removing the support by dissolution in water with ultrasonic device.

[0320] The obtained product is for example shown in FIG. 1-2. As indicated above, FIG. 1 shows the silicone elastomer article before removing the support material, whereas FIG. 2 shows the silicone elastomer article after removing the support material.

[0321] The obtained silicone elastomer article is well formed, and the support material can be removed easily and quickly.