USE OF POLYHYDROXY COMPOUND AS PLASTICIZER FOR POLYVINYL ALCOHOL IN 3D PRINTING PROCESS

Abstract

The invention is directed to a process of manufacturing a three-dimensional object byproviding a support structure comprising polyvinyl alcohol (PVOH) todepositing and solidifying a molten thermoplastic polymer on the support structure to form a three-dimensional preform characterized in that the support structure consists of a mixture of polyvinyl alcohol (PVOH) and at most 20% by weight of at least one plasticizer according to formula (I), (II) or (III): R1-C(CH.sub.2OH).sub.3 (1); [R1-C(CH.sub.2OH).sub.2CH.sub.2].sub.2O (11); (R1)C(CH.sub.2OH).sub.2CH.sub.2OCH.sub.2C(CH.sub.2OH)C(R1)CH.sub.2OCH.sub.2 C(CH.sub.2OH)2R1 (III). With R1=H, CH3, C.sub.2H.sub.5, C.sub.3H.sub.7, CH.sub.2OH. The support structure can be dissolved to from the three-dimensional object.

Claims

1. A process of manufacturing a three-dimensional object, comprising: depositing and solidifying a molten thermoplastic polymer on a support structure to form a three-dimensional preform, wherein the support structure consists of a mixture of polyvinyl alcohol (PVOH) and at most 20% by weight of at least one plasticizer according to formula I, II or III:
R1-C(CH.sub.2OH).sub.3 (I)
[R1-C(CH.sub.2OH).sub.2CH.sub.2].sub.2O (II)
(R1)C(CH.sub.2OH).sub.2CH.sub.2OCH.sub.2C(CH.sub.2OH)C(R1)CH.sub.2OCH.sub.2C(CH.sub.213 OH).sub.2R1 (III) wherein R1 is H, CH.sub.3, C.sub.2H.sub.5, C.sub.3H.sub.7, or CH.sub.2OH.

2. The process according to claim 1, wherein the plasticizer is at least one selected from the group consisting of trimethylolpropane, di(trimethylolpropane), pentaerythritol, dipentaerythritol and tripentaerythritol.

3. The process according to claim 1, wherein the polyvinyl alcohol (PVOH) has a vinyl actetate content of at least 10 mol %.

4. The process according to claim 1, wherein the polyvinyl alcohol (PVOH) has a degree of polymerization of 200 to 3000.

5. The process according to claim 1, wherein the polyvinyl alcohol (PVOH) has a degree of hydrolysation DH of 60 to 99%.

6. The process according to claim 1, wherein the support structure is dissolved to form the three-dimensional object.

7. The process according to claim 6, wherein the support structure is dissolved in water.

8. The process according to claim 1, wherein the molten polyvinyl alcohol (PVOH) is deposited at a temperature of at least 170 C.

9. The process according to claim 1, wherein the thermoplastic polymer is deposited on the support structure at a temperature of at least 140 C.

10. The process according to claim 1, wherein the thermoplastic polymer is at least one selected from the group consisting of polylactic acid (PLA), acrylonitrile-butadiene-styrene copolymer (ABS), polyamides (PA), polycarbonates (PC), polyethylene terephthalate (PET), polyethylene terephthalate copolymers (PETG), polyhydroxyalkanoates (PHA), wood filled composites, metal filled composites, carbon fiber filled composites, polyvinylbutyral (PVB), thermoplastic elastomers (TPE), thermoplastic polyurethanes (TPU), polyolefins, polypropylenes (PP), acrylonitrile styrene acrylate (ASA), polyacrylates, and polymethacrylates.

11. The process according to claim 1, wherein the polyvinyl alcohol (PVOH) comprises as repeating units vinyl alcohol, vinyl acetate and up to 20 Mol % of further olefinic monomers.

Description

EXAMPLES

[0030] Compounds of PVOH and plasticizers were prepared with a DSM Xplore micro compounder MC 15. All components were mixed thoroughly before filling into the compounder. The samples were homogenized in the compounder at a screw speed of 100 rpm and a melt temperature of 190 C. for 5 minutes. The micro compounder provides a value for the melt viscosity of the sample during extrusion. After homogenization the melt was extruded to a strand with a diameter of ca. 3 mm, which was cut to ca. 3 cm long pieces. The same process was also used to extrude the strand onto a belt with adjustable speed. By controlling the speed the strand diameter was adjusted to obtain a filament of 1,75 mm in diameter. The filament was subjected to 3d printing tests with a Felix Pro 1 3d printer.

[0031] PVOH resin from Kuraray Europe GmbH was used. Trimethylolpropane (TMP) was purchased from BASF. Di(trimethylolpropane) (Di-TMP), pentaerythritol (penta) and dipentaerythritol (di-penta) were obtained from Perstorp.

[0032] Thermal properties of compounds were determined by DSC measurement with a Netzsch DSC 214 ASC Polyma equipped with an Intracooler 70. A temperature range of 20 C. to 230 C. was used. Melting temperatures were measured at a heating/cooling rate of 10 K/min in the second heating cycle. Glass transition temperatures were derived from a third heating cycle at a heating rate of 30 K/min. The moisture uptake of each sample was determined by placing a defined quantity of the strand pieces of each compound into a climate chamber at 23 C. and a relative humidity of 50%. The weight increase was measured over time.

Comparative Example 1

[0033] KURARAY POVAL 6-88 was compounded with 5 wt.% of glycerine. A melt viscosity of 1.11 kPa.Math.s was measured during extrusion. A glass transition temperature Tg of 56.6 C. and a melting temperature Tm of 173.7 C. was measured by DSC. The product absorbed 1.8 wt.% of moisture during storage at 23 C. and 50% relative humidity for 14 days. The product is entirely soluble in water at 25 C.

[0034] A 1.75 mm filament extruded from the same formulation was exposed to 23 C. and 50% relative humidity for 14 days before it was used for printing of a test object. Some defects by uncontrolled release of melt from the nozzle by bubble formation were observed, but overall the print quality was still acceptable.

Comparative Example 2

[0035] KURARAY POVAL 6-88 was compounded with 10 wt.% of glycerine. A melt viscosity of 0.84 kPa.Math.s was measured during extrusion. A glass transition temperature Tg of 46.7 C. and a melting temperature Tm of 171.6 C. was measured by DSC. The product absorbed 4.0 wt.% of moisture during storage at 23 C. and 50% relative humidity for 14 days. The product is entirely soluble in water at 25 C. A 1.75 mm filament extruded from the same formulation was exposed to 23 C. and 50% relative humidity for 14 days before it was used for printing of a test object. A lot of defects by uncontrolled release of melt from the nozzle by bubble formation were observed. The overall print quality was bad, due to foam formation of the melt.

Examples 1-8

[0036] KURARAY POVAL 6-88 was compounded with various amounts of different plasticizers as listed in Table 1. For all experiments the melt viscosity measured by the microcompounder is in a similar range as a comparable compound with glycerine as plasticizer. This indicates efficient plastification of the compound. Generally, all glass transition and melting temperatures were higher than of comparable compounds with glycerine as a plasticizer. The moisture absorption of all compounds was lower than of comparable compounds with glycerine as plasticizer (see Table 1). All compounds are entirely soluble in water at 25 C.

[0037] 1.75 mm filaments extruded from the formulations were exposed to 23 C. and 50% relative humidity for 14 days before they were used for printing of test objects. For examples 2 and 6 some defects by uncontrolled release of melt from the nozzle by bubble formation were observed, but overall the print quality was still acceptable. Thus, a similar print quality as in comparative example 1 could be achieve, but with double plasticizer content, which allows for faster and easier printing due to lower melt viscosity. All other examples resulted in high printing quality without any significant defects.

TABLE-US-00001 TABLE 1 Experimental results for examples 1-8. Melt Moisture viscosity.sup.a Tg.sup.b Tm.sup.b absorption.sup.c Example Plasticizer [kPa .Math. s] [ C.] [ C.] [wt. %] 1 5 wt. % TMP 1.17 61.7 181.6 1.3 C1 5 wt % glycerine 1.11 56.6 173.7 1.8 2 10 wt. % TMP 0.89 52.9 182.8 2.3 C2 10 wt % glycrine 0.84 46.7 171.6 4.0% 3 5 wt. % Di-TMP 1.22 62.6 184.7 1.1 4 10 wt. % Di-TMP 0.98 56.6 183.7 1.4 5 5 wt. % penta 1.24 64.0 179.0 1.3 6 10 wt. % penta 0.95 53.1 170.5 2.1 7 5 wt. % Di-penta 1.27 64.3 181.5 1.1 8 10 wt. % Di-penta 1.07 56.8 179.2 1.1 .sup.aMelt viscosity measured by the microcompounder. .sup.bGlass transition temperature Tg and melting temperature Tm determined by DSC. .sup.cMoisture absorption at 23 C. and 50% relative humidity after 14 days. TMP = trimethylolpropane, Di-TMP = di(trimethylolpropane), penta = pentaerythritol, Di-penta = dipentaerythritol