METHOD FOR THE 3D PRINTING OF TWO-COMPONENT POLYURETHANE COMPOSITIONS

Abstract

A method applying a two-component polyurethane composition by means of 3D printing, including steps providing pumpable first component A including at least one polyol having OH functionality in range from 1.5-4 and average molecular weight Mn in range from 250 to 15 000 g/mol, and at least one diol having two hydroxyl groups joined via a C2-C9 carbon chain, and at least one compound T having at least one thiol group; feeding pumpable second component B into continuous mixer's mixing region, where second component B includes at least one polyisocyanate; wherein one of components A and B additionally includes at least one metal catalyst for reaction of hydroxyl groups and isocyanate groups that is able to form thio complexes, and molar ratio of all thiol groups in at least one compound T to all metal atoms in at least one metal catalyst K is between 1:1 and 250:1.

Claims

1. A method of applying a two-component polyurethane composition by means of 3D printing, comprising the steps of providing a pumpable first component A comprising at least one polyol A1 having an OH functionality in the range from 1.5 to 4 and an average molecular weight (number average) M.sub.n in the range from 250 to 15 000 g/mol, and at least one diol A2 having two hydroxyl groups joined via a C2 to C9 carbon chain, and at least one compound T having at least one thiol group; feeding the first component A to a continuous mixer comprising an inlet, a mixing region having at least one static or dynamic mixing element connected to the inlet, an outlet into which the mixing region opens, wherein the first component A is conveyed through the at least one inlet into the mixing region; feeding a pumpable second component B into the mixing region of the continuous mixer, where the second component B comprises at least one polyisocyanate I; mixing the first component A with the second component B in the mixing region of the continuous mixer to give a mixed curable polyurethane composition; conveying the mixed curable polyurethane composition to the outlet; and applying the mixed curable polyurethane composition layer by layer; wherein one of the two components A and B additionally includes at least one metal catalyst K for the reaction of hydroxyl groups and isocyanate groups that is able to form thio complexes, and the molar ratio of all the thiol groups in the at least one compound T to all metal atoms in the at least one metal catalyst K is between 1:1 and 250:1.

2. The method as claimed in claim 1, wherein the metal catalyst K comprises a bismuth(III) compound.

3. The method as claimed in claim 2, wherein the bismuth(III) compound additionally contains an 8-hydroxyquinoline ligand or a 1,3-ketoamide ligand.

4. The method as claimed in claim 1, wherein the diol A2 is selected from the group consisting of butane-1,3-diol, butane-2,3-diol, butane-1,4-diol, 2-methylpropane-1,3-diol, pentane-1,2-diol, pentane-1,5-diol, pentane-2,4-diol, 2-methylbutane-1,4-diol, 2,2-dimethylpropane-1,3-diol, hexane-1,2-diol, hexane-1,6-diol, 3-methylpentane-1,5-diol, octane-1,2-diol, octane-3,6-diol, nonane-1,9-diol, 2-ethylhexane-1,3-diol, 2,2,4-trimethylpentane-1,3-diol, 2-butyl-2-ethylpropane-1,3-diol, 2,7-dimethyloctane-3,6-diol, cyclohexane-1,4-diol, cyclohexane-1,3-dimethanol and cyclohexane-1,4-dimethanol.

5. The method as claimed in claim 1, wherein the at least one compound T comprises a polythiol compound having 2 to 6 thiol groups, or a mercaptosilane.

6. The method as claimed in claim 5, wherein the at least one compound T is selected from the group consisting of ethylene glycol di(3-mercaptopropionate), ethylene glycol dimercaptoacetate, dipentaerythritol hexa(3-mercaptopropionate), and 3-mercaptopropyltrimethoxysilane.

7. The method as claimed in claim 1, wherein the molar ratio of all the thiol groups in the at least one compound T to all metal atoms in the at least one metal catalyst K is between 5:1 and 100:1.

8. The method as claimed in claim 1, wherein the metal catalyst K is present in the first component A.

9. The method as claimed in claim 1, wherein the polyol A1 comprises a polyether polyol.

10. The method as claimed in claim 1, wherein the polyisocyanate I is a form of diphenylmethane 4,4′-, 2,4′- or 2,2′-diisocyanate that is liquid at room temperature and any mixtures of these isomers (MDI) in the form of polymeric MDI or MDI containing proportions of oligomers or derivatives.

11. The method as claimed in claim 1, wherein the second component B comprises a polyurethane polymer containing isocyanate groups.

12. The method as claimed in claim 1, wherein the composition comprises less than 0.5% by weight of carboxylic acids, based on the overall composition.

13. The method as claimed in claim 1, wherein the two components A and B each have a viscosity, measured at 20° C. on a plate-plate viscometer with plate separation 1 mm and plate diameter 25 mm, of less than 75 Pa.Math.s at a shear rate of 10 s.sup.−1.

14. The method as claimed in claim 1, wherein the static or dynamic mixer is mounted on a moving printhead.

15. A shaped body produced by the method as claimed in claim 1.

Description

EXAMPLES

[0166] Substances Used:

TABLE-US-00001 TABLE 1 Substances used Voranol CP 4755 Voranol ® CP 4755 (Dow Chemical); polyether triol, CAS No. 9082-00-2; MW: 5000 g/mol; OH value: 35 mg KOH/g Pentane-1,5-diol (Sigma Aldrich) Thiocure GDMP Thiocure ® GDMP (Bruno Bock Thiochemicals); glycol di(3-mercaptopropionate) Desmodur CD-L Desmodur ® CD-L (Covestro); modified diphenylmethane 4,4′-diisocyanate (MDI); NCO content: 29.5% by weight Monarch 570 Monarch ® 570 (Cabot Corp.); carbon black (filler) Whitetex White Tex ® (BASF); calcined aluminum silicate (filler) Bi cat. (2.68 35% by weight of Coscat 83 (organobismuth catalyst; mmol Bi/g) Coscat ® 83 (Vertellus Specialties Inc.)) in plasticizer containing 1 molar equivalent of 8-hydroxyquinoline (based on Bi)

[0167] Production of Components A and B

[0168] For each composition, the ingredients of the first component A specified in table 2 below were processed in the amounts specified (in parts by weight or wt %), by means of a vacuum dissolver with the exclusion of moisture, to give a homogeneous paste and stored airtight. The ingredients of the second component B specified in the tables were likewise processed and stored. The two components were each introduced into one compartment of an airtight twin cartridge.

TABLE-US-00002 TABLE 2 Two-component polyurethane composition for 3D printing Ingredient Parts by weight Component A Voranol CP 4755 60 Pentane-1,5-diol 12 Monarch 570 10 Whitex 15.7 Thiocure GDMP 1.5 Bi cat. 0.8 TOTAL 100 Component B Desmodur CD-L 44 Voranol CP-4755 32 Whitex 15 Monarch 570 10 TOTAL 100

[0169] Printing Test

[0170] The abovementioned twin cartridge (with one cartridge of the twin cartridge containing component A and the other component B, both components according to the ingredient data in table 2) was connected to a 3D printer such that the cartridge outlet opened into a static mixer of length 10 cm.

[0171] The outlet of the static mixer opened into a hose connected to the printhead of the 3D printer. The printhead had a round exit opening having a diameter of 2 mm. The 3D printer used was a commercial Delta WASP 2040 3D printer (from WASP CSP S.r.I., Italy). The twin cartridge was expressed at a flow rate of 100 ml/minute by means of a pneumatic piston. The two components A and B were mixed in a volume ratio A:B (v/v) of 1:1. The dwell time in the mixer was about 10-20 s.

[0172] It was thus possible, in a continuous process, to print a cylindrical hollow figure layer by layer with a height of 10 cm, a wall thickness of 2 mm and a diameter of 5 cm within 2-3 min. The composition was sag-resistant and dimensionally stable directly after application and subsequently cured continuously, although the curing of one layer was still incomplete when a second layer was applied thereto. This permitted good cohesion between the layers. After about 15 min, the shaped body was firm and had formed a dry skin.

[0173] The shaped body had a nice smooth surface and was of solid, elastic consistency.