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EP-3776081-B1 - THIOL-ACRYLATE POLYMERS, METHODS OF SYNTHESIS THEREOF AND USE IN ADDITIVE MANUFACTURING TECHNOLOGIES

EP3776081B1EP 3776081 B1EP3776081 B1EP 3776081B1EP-3776081-B1

Inventors

  • LUND, BENJAMIN
  • HUFFSTETLER, Jesse
  • ZAMORANO, Daniel
  • DAS, SUSHANTA
  • NIERMANN, Crystal
  • LUND, Caleb
  • NGUYEN, AMY
  • WU, Yili
  • VOIT, WALTER

Dates

Publication Date
20260506
Application Date
20190328

Claims (13)

  1. A photopolymerizable resin for additive manufacturing in an oxygen environment, the resin comprising: a crosslinking component; at least one monomer and/or oligomer, wherein the at least one monomer and/or oligomer includes an acrylic monomer; and a chain transfer agent comprising at least one thiol, wherein the thiol includes a secondary thiol, wherein the resin is configured to react by exposure to light to form a cured material, wherein the chain transfer agent is configured to permit at least some bonding between a layer of resin previously cured and an adjacent, subsequently cured layer of resin, despite an oxygen-rich surface present on the previously cured layer of resin at an interface between the previously cured layer of resin and the subsequently cured layer of resin; and wherein the chain transfer agent is about 0.5 to 5% by weight of the resin.
  2. The photopolymerizable resin according to claim 1, wherein the chain transfer agent is about 0.5% to 4.0% by weight of the resin.
  3. The photopolymerizable resin according to claim 1, wherein the crosslinking component is about 1-95% by weight of the resin.
  4. The photopolymerizable resin according to claim 1, wherein the at least one monomer and/or oligomer is about 1-95% by weight of the resin.
  5. The photopolymerizable resin according to claim 1, wherein the crosslinking component includes a difunctional acrylic oligomer.
  6. The photopolymerizable resin according to claim 1, wherein the crosslinking component includes an aliphatic urethane acrylate oligomer.
  7. The photopolymerizable resin according to claim 1, wherein the crosslinking component includes an aromatic urethane acrylate oligomer.
  8. The photopolymerizable resin according to claim 1, wherein the crosslinking component includes at least one of poly(ethylene glycol) diacrylate, bisacrylamide, tricyclo[5.2.1.0 2,6 ]decanedimethanol diacrylate, and/or trimethylolpropane triacrylate.
  9. The photopolymerizable resin according to claim 1, wherein the secondary thiol includes at least one of Pentaerythritol tetrakis (3-mercaptobutylate); 1,4-bis (3-mercaptobutylyloxy) butane; and/or 1,3,5-Tris(3-melcaptobutyloxethyl)-1,3,5-triazine.
  10. The photopolymerizable resin according to claim 1, further comprising polybutadiene.
  11. An article having a majority of layers comprising the photopolymerizable resin of claim 1.
  12. A footwear midsole made from the photopolymerized resin of claim 1.
  13. A shape memory foam made from the photopolymerized resin of claim 1.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Application No. 62/649,130, filed March 28, 2018, and U.S. Provisional Application No. 62/660,894, filed April 20, 2018. FIELD OF INVENTION This invention is related generally to the field of additive manufacturing, and more particularly to three-dimensional (3D) printing materials, methods, and articles made therefrom. BACKGROUND Additive manufacturing or 3D printing refers to the process of fabricating 3D objects by selectively depositing material layer-by-layer under computer control. One category of additive manufacturing processes is vat photopolymerization in which 3D objects are fabricated from liquid photopolymerizable resins by sequentially applying and selectively curing a liquid photopolymerizable resin using light, for example ultraviolet, visible or infrared radiation. Stereolithography (SLA) and digital light processing (DLP) are examples of vat photopolymerization type additive manufacturing processes. Typically, systems for SLA or DLP include a resin vat, a light source and a build platform. In laser-based stereolithography (SLA), the light source is a laser beam that cures the resin voxel by voxel. Digital light processing (DLP) uses a projector light source (e.g., a LED light source) that casts light over the entire layer to cure it all at once. The light source may be above or below the resin vat. Generally, SLA and DLA printing methods include first applying a layer of the liquid resin on the build platform. For example, the build platform may be lowered down into the resin vat to apply the layer of resin. The liquid resin layer is then selectively exposed to light from the light source to cure selected voxels within the resin layer. For example, the resin may be cured through a window in the bottom of the resin vat by a light source from below (i.e. "bottom up" printing) or cured by a light source above the resin vat (i.e. "top down" printing). Subsequent layers are produced by repeating these steps until the 3D object is formed. Liquid photopolymerizable resins for 3D printing cure or harden when exposed to light. For example, liquid photo-curable thiol-ene and thiol-epoxy resins have been used in such applications. Thiol-ene resins polymerize by reaction between mercapto compounds (-SH, "thiol") with a C=C double bond, often from a (meth-) acrylate, vinyl, allyl or norbornene functional group, of the "ene" compound. For photo- initiated thiol-ene systems, the reaction follows a radical addition of thiyl-radical to an electron rich or electron poor double bond. The nature of the double bond may contribute to the speed of the reaction. The reaction steps of the radical-initiated, chain-transfer, step-growth thiol-ene polymerization may proceed as follows: a thiyl radical is formed through the abstraction of a hydrogen radical; the thiyl radical reacts with a double bond, cleaving it, and forms a radical intermediate of the β-carbon of the ene; this carbon radical then abstracts a proton radical from an adjacent thiol, through a chain transfer, reinitiating the reaction which propagates until all reactants are consumed or trapped. In the case of di- and polyfunctional thiols and enes, a polymer chain or polymer network is formed via radical step growth mechanisms. Thiol-ene polymerizations can react either by a radical transfer from a photoinitiator or by direct spontaneous trigger with UV-irradiation (nucleophilic Michael additions are also possible between un-stabilized thiols and reactive enes). For example, thiol-ene photopolymerizable resins have been cast and cured into polymers that show high crosslinking uniformity and a narrow glass transition temperature (Roper et al. 2004). These thiol-ene resins typically contain a molar ratio between 1:1, Id., and 20:80 (Hoyel et al. 2009) of thiol to ene monomer components. Additionally, thiol-ene resins comprising specific ratios of 1:1 to 2:1 pentaerithrytol tetrakis (3-mercaptopropionate) to polyethylene glycol have been used in 3D printing methods (Gillner et al. 2015). WO2017/154428A1 can also be cited as example of a photopolymerizable resin of the prior art. One problem that may be encountered with additive manufacturing of liquid photopolymerizable resins is oxygen inhibition. Typically, in systems for vat photopolymerization type additive manufacturing processes, the resin vat is open and exposed to ambient air during printing. This allows oxygen to dissolve and diffuse into the liquid resin. Oxygen molecules scavenge the radical species needed for curing. Therefore, oxygen has an inhibitory effect, slowing the curing rate and increasing manufacturing times. Incomplete curing due to oxygen inhibition produces 3D objects having highly tacky, undesirable surface characteristics. Further, in top down printing systems, the top surface of the resin, having the highest oxygen concentration, is also the interface where the next layer of resin is t