3D printed product

Abstract

The invention relates to a 3D printing product, in particular to a 3D printing product based on carbamate-acrylate-resin, which is separated from a color distance delta Elt of a coordinate L * a * b * of a color number starting from '2' in an RAL color card, and a color distance delta Elt of a coordinate L * a * b * of a color number starting from '2'. 20, comprising at least one orange methine dye dissolved therein, relating to the orange methine dye for producing, by photopolymerization-based 3D printing, a color distance [Delta] Elt; the present invention relates to the use of 3D printed products having a value of 1, 20, and to a method for improving the light resistance and color properties of a photopolymerizable urethane-acrylate-resin-based composition and of 3D printed products produced therefrom by means of at least one orange methine dye dissolved therein, and to a method for improving the light resistance and color properties of a photopolymerizable urethane-acrylate-resin-based composition and of a 3D printed product produced therefrom, the color distance delta Elt of the compositions and 3D printed products from the L * a * b * coordinate of the color number starting from 2 in the RAL color card; 20.

Description

Technical Field

[0001] The present invention relates to a 3D-printed product based on a urethane-acrylate resin, wherein the color distance ΔE of the L*a*b* coordinates of the color number beginning with "2" on the RAL color chart is less than 20, and the product contains at least one orange methine dye dissolved therein. The present invention also relates to the use of the orange methine dye for producing 3D-printed products having a color distance ΔE of less than 20 from the L*a*b* coordinates of the color number beginning with "2" on the RAL color chart by 3D printing based on photopolymerization. The present invention also relates to a method for improving the light fastness and color properties of a photopolymerizable composition based on a urethane-acrylate resin and a 3D-printed product produced therefrom by means of at least one orange methine dye dissolved therein, wherein the color distance ΔE of the L*a*b* coordinates of the color number beginning with "2" on the RAL color chart is less than 20. Background Art

[0002] Color masterbatches contain colorants in dispersed or dissolved form. The color or hue of plastic products serves, among other things, as a distinguishing feature of a company or a specific product, as a protective component, as a safety feature, or as a functional additive. Amorphous plastics such as polystyrene, polycarbonate, and polymethyl methacrylate, where transparency must be maintained, require the use of polymer-soluble dyes. Compared to pigments, colorants used for 3D printing via photopolymerization are preferably soluble in the plastic resin being processed and do not exist in colloidal form.

[0003] 3D printing is an additive manufacturing method. This refers to a process in which a component is built layer by layer by depositing material based on digital 3D design data. Therefore, for the purposes of this article, "3D printing" will be used as a synonym for additive manufacturing. However, additive manufacturing better describes a production process that differs significantly from conventional subtractive manufacturing methods. For example, additive manufacturing does not mill a workpiece from a solid block, but rather builds a component layer by layer from material available, for example, in fine powder form. A variety of metals, plastics, and composite materials are available as materials.

[0004] Meanwhile, 3D printing has established itself as a manufacturing method in numerous fields and industries. This method offers impressive advantages not achievable with other conventional methods, including for the construction of demonstration and functional prototypes, small and medium-sized series production, and, increasingly, large-scale production. For example, product development and market launch can be significantly accelerated, and product personalization or functional integration can be achieved in a shorter timeframe and often at a lower cost. For major original equipment manufacturers (OEMs) across a wide range of industries, additive manufacturing through 3D printing offers market differentiation opportunities in terms of new customer benefits, cost-reduction potential, and sustainability goals. In 3D printing, products are created by selectively shaping a material suitable for the respective printing technology into the desired shape, layer by layer, in an automated process. An original equipment manufacturer, or OEM, is a manufacturer of parts or products that does not actually place them on the retail market; in the automotive industry, the term "OEM" is used synonymously with the vehicle manufacturer.

[0005] There are various 3D printing processes for plastics. These include processes in which the plastic is produced only by curing during printing. One example is 3D printing based on photopolymerization, in which a photocurable resin liquid is applied layer by layer and subjected to a photocuring process / polymerization or photoinduced curing by the use of light. The selective layer-by-layer curing of the liquid resin is achieved by spatially confined, precisely defined, and computer-controlled exposure of the resin to light within a spectral range suitable for initiating the photopolymerization process. UV, visible, or infrared light are particularly suitable. The photopolymerization-based 3D printing process according to the present invention is preferably stereolithography (SLA) or digital light processing (DLP). In both 3D printing variants, the corresponding apparatus setup consists of a light source (through which light exposure can be applied from above or below, so-called "top-down" or "bottom-up" printing), a resin reservoir, and a platform on which the layer-by-layer curing of the plastic resin to be used for 3D printing occurs. In SLA 3D printing, the surface to be cured is exposed to light point by point by scanning with a laser beam; in DLP processes, exposure occurs over the entire surface to be exposed, typically using an LCD (liquid crystal display) panel. During a typical printing process, the print platform is immersed in resin from a resin reservoir while the exposure process runs and layers are created. Repeated layer creation ultimately results in the 3D printed product. In the SLA process, stereolithography printers use lasers to create 3D printed products. To do this, a plastic solution that cures under UV light is applied. The corresponding 3D printers are referred to as SLA 3D printers or DLP 3D printers. A comparison of the two technologies, as well as suppliers of the corresponding 3D printers, can be found in the review article: 3Dnatives, Regina P. April 8, 2021, at https: / / www.3dnatives.com / de / sla-vs-dlp-3d-druck-080420211 /

[0006] US 2004 / 204513 A1 provides a highly sensitive two-photon polymerizable composition capable of photopolymerization via two-photon absorption and simultaneously dyeing the polymer to a desired color during polymerization. Such a composition capable of photopolymerization via two-photon absorption comprises at least (A) a polymerizable compound, (B) a two-photon absorbing compound, (C) a polymerization initiator, and (D) a dye.

[0007] US 2011 / 0070976 A1 describes a golf ball composed of a core, at least one layer surrounding the core, and a fluorescent pigment color layer applied to the outermost surface of the casing. The outermost layer can be composed of a thermoplastic polyurethane material (Pandex® T8290 or Pandex® T8283). In one example, the orange fluorescent dye Solvent Orange 60 (Sumiplast® Orange HRP) is used as the color layer applied to the outermost layer. This ball exhibits excellent spin performance and durability, and its appearance is characterized by excellent visibility, stylishness, and luxury, as well as excellent weather resistance.

[0008] US 2019 / 0201171 A1 discloses a colored curable composition for use in an additive manufacturing method, wherein the composition comprises: a curable resin composition comprising a radiation-curable component, a photoinitiator, and a dye composition comprising a dye D1 and a dye D2, wherein dye D1 has a maximum light absorption in the wavelength range of 400 to 530 nm, and dye D2 has a maximum light absorption in the wavelength range of 540 to 650 nm. As an example, two anthraquinone dyes are used: CI Solvent Red 111, CAS No. 82-38-2 (Dye 1) and CI Solvent Violet 13, CAS No. 81-48-1 (Dye 2). The patent also describes an S30 3D printer (Rapid Shape GmbH, Heimsheim, Germany) that uses a wavelength of 405 nm and an intensity of 50 mW / cm 2 The LED light was applied for 11 seconds per layer.

[0009] In addition to favorable color properties during and immediately after the photopolymerization process for producing 3D-printed products, the in-use characteristics of such 3D-printed products must also be considered. The colorants used in the aforementioned prior art have proven disadvantageous due to color changes during the 3D manufacturing process due to exposure to the light required for photopolymerization. However, light sensitivity / light resistance is a hallmark of colored 3D-printed products produced via photopolymerization-based 3D printing. Fading, discoloration, or even browning of 3D-printed products produced via photopolymerization-based 3D printing should be avoided whenever possible.

[0010] Furthermore, during photopolymerization, preferably by SLA or DLP processes, colorants intended for 3D printing should maintain their advantageous performance characteristics and should not impair or even prevent the curing / polymerization of the 3D printed product. For the purposes of the present invention, advantageous performance characteristics in orange dyes for 3D printing according to the present invention are the creation of a desired / defined hue and the creation of a pure, vibrant color.

[0011] The problem addressed by the present invention is to provide an orange dye for 3D printing by photopolymerization, in particular by the SLA or DLP method, which, due to its solubility in the plastic to be processed, allows the creation of a defined orange hue, remains lightfast during the printing process and also maintains its color properties.

[0012] Method for evaluating light fastness

[0013] To determine the light fastness of dyes used in photopolymerization-based 3D printing, test specimens in the form of cuboids of colored resin were produced for the purposes of this invention. These specimens had dimensions of length = 60 mm, width = 40 mm, and height = 2 mm, and a dye concentration of 0.02% in the resin. These test specimens were then exposed to light (xenon arc) for 95–100 hours in the immediately printed state using a Xenotest Beta+ apparatus (Atlas Material Testing Technology GmbH, Linsengerich-Altenhaßlau, Germany) in accordance with DIN EN ISO 4892-2. Light fastness was evaluated colorimetrically by recording the transmission spectra of the exposed test specimens using an X-Rite Ci7800 sphere spectrophotometer (X-Rite GmbH, Planegg-Martinsried, Germany) with the following settings selected: measurement geometry = d / 8°; spectral interval = 10 nm; spectral range = 360–750 nm. Based on the obtained transmission spectrum, the manufacturer's sphere spectrophotometer software then calculates colorimetric data using the following settings: Illuminant / Observer = D65 / 10°; Color Space = L*a*b*C*h°. Lightfastness evaluation is based on the color distance ΔE between the light-exposed test sample and the corresponding unexposed test sample in the L*a*b*C*h° color space. The larger the color distance, the greater the change in color perception caused by light exposure, and therefore the poorer the lightfastness. ΔE is classified based on comparison with other orange dyes used as examples outside the present invention, whose lightfastness in other applications, particularly for mass coloring of plastics, is generally rated as good according to the manufacturer's data.

[0014] Method for evaluating the stability of color characteristics

[0015] In order to determine the changes in the spectral properties that determine the color characteristics of the dyes, for the purposes of the present invention, the absorption spectra of the colored resins under investigation were compared before and after light-induced curing.

[0016] To this end, the colored resins produced as described above in the "Method for Evaluating Lightfastness" section were transferred to quartz glass cuvettes with a width of 1 cm, and their absorption spectra were recorded in transmission mode over a wavelength range of 360 to 750 nm using an X-Rite Ci7800 instrument (X-Rite GmbH, Planegg-Martinsried, Germany). These absorption spectra were then corrected for the absorbance of the corresponding colorless resin by performing identical measurements with the colorless resin. Similarly, the absorption spectra of the colored test samples were recorded and corrected in transmission mode, and in each case, the spectrum was normalized to the path length of the cuvette / test sample in question.

[0017] Finally, the similarity of the absorption spectra before and after 3D printing was calculated from the measured data by calculating the correlation coefficient R of the normalized absorption (spectral spacing of 10 nm). The larger the value of R, the greater the similarity of the absorption spectra, and the more stable the color characteristics of the dye used for photopolymerization-based 3D printing and suitable for the purposes of the present invention are expected to be. Summary of the Invention

[0018] The solution to the problem provided by the present invention is 3D-printed products, whose color distance ΔE of the L*a*b* coordinates of the color numbers starting with "2" on the RAL color chart is less than 20. These 3D-printed products are based on a photopolymerizable composition comprising at least one urethane acrylate resin and at least one orange methine dye, wherein the orange methine dye has a molecular weight in the range of 50 to 1000 g / mol and a solubility in the composition based on urethane-acrylate resin of ≥ 0.05 g / L at 23°C, determined in accordance with DIN EN ISO 7579:2010 DE.

[0019] The present invention also provides the use of at least one orange methine dye having a molecular weight in the range of 50 to 1000 g / mol for improving the light fastness and color properties of photopolymerizable compositions based on urethane-acrylate resins and 3D-printed products produced therefrom, as determined in accordance with DIN EN ISO 4892-2. These compositions and 3D-printed products have a color distance ΔE < 20 from the L*a*b* coordinates of a color number beginning with "2" on the RAL color chart and have a dye solubility in the composition based on urethane-acrylate resin of ≥ 0.05 g / L at 23°C, as determined in accordance with DIN EN ISO 7579:2010 DE. The improvement of the light fastness and color properties in the use according to the invention is measured by recording the transmission spectra of a test sample of the corresponding colored urethane acrylate resin before and after light-induced curing using a sphere spectrophotometer, and then correcting for the absorbance of the corresponding colorless resin and normalizing for the path length of the cuvette / test sample under investigation, and finally determining the similarity of the absorption spectra before and after 3D printing from the measured data by calculating the correlation coefficient R of the normalized absorbance.

[0020] The present invention further relates to a method for improving the light fastness and color properties of photopolymerizable compositions based on urethane acrylate resins and 3D-printed products produced therefrom, as determined in accordance with DIN EN ISO 4892-2, using at least one orange methine dye having a molecular weight in the range of 50 to 1000 g / mol and a solubility in the composition based on urethane acrylate resins of ≥ 0.05 g / L at 23° C., as determined in accordance with DIN EN ISO 7579:2010 DE. The composition and 3D-printed products have a color distance ΔE < 20 from the L*a*b* coordinates of a color number starting with “2” on the RAL color chart. As with the use according to the invention, the improvement of the light fastness and color properties in the method according to the invention is measured by recording the transmission spectra of a test sample of the corresponding colored urethane acrylate resin before and after light-induced curing using a sphere spectrophotometer, and then correcting for the absorbance of the corresponding colorless resin and normalizing for the path length of the cuvette / test sample under investigation, and finally determining the similarity of the absorption spectra before and after 3D printing from the measured data by calculating the correlation coefficient R of the normalized absorbance.

[0021] Finally, the present invention also relates to a method for the additive production of 3D-printed products in a SLA 3D printer or DLP 3D printer based on photopolymerization, using a composition based on a urethane-acrylate resin containing at least one orange methine dye having a molecular weight in the range of 50 to 1000 g / mol and a solubility in the composition based on a urethane-acrylate resin of ≥ 0.05 g / L at 23°C, wherein the color distance ΔE of the L*a*b* coordinates of these 3D-printed products to a color number starting with "2" on the RAL color chart is less than 20.

[0022] For the sake of clarity, it should be noted that the scope of the present invention encompasses all definitions and parameters mentioned below in general or specified in the preferred ranges, in any desired combination. This also applies to the combination of the individual components in the amounts described in connection with the claimed methods and uses. The standards cited in the context of this application relate to the versions current at the filing date of this application. Unless otherwise stated, percentage values ​​are percentages by weight.

[0023] Table 1: Orange RAL color card

[0024] In the context of the present invention, orange is understood to mean a color in the RAL color system according to https: / / de.wikipedia.org / wiki / RAL-Farbe#Orange which has a color number starting with "2" in the RAL color card. Specifically, at the filing date of the present invention, the following distinction is made between orange hues:

[0025] L*a*b*

[0026] RAL 2000 yellow orange 58.2037.3068.68

[0027] RAL 2001 orange 49.4139.7935.29

[0028] RAL 2002 Blood Orange 47.7447.8733.73

[0029] RAL 2003 light orange 66.0241.2252.36

[0030] RAL 2004 pure orange 56.8950.3449.81

[0031] RAL 2005 bright orange 72.2787.7882.31

[0032] RAL 2007 bright light orange 76.8647.8797.63

[0033] RAL 2008 light reddish orange 60.3346.9160.52

[0034] RAL 2009 Traffic Orange 55.8347.7948.83

[0035] RAL 2010 Signal Orange 55.3940.1042.42

[0036] RAL 2011 dark orange 59.2440.8664.50

[0037] RAL 2012 salmon orange 57.7540.2830.66

[0038] RAL 2013 Pearl Orange 40.7332.1434.92

[0039] This table shows the device-independent CIE L*a*b* color values ​​for each RAL orange value: L* represents lightness, a* describes the color's position on the red-green axis, and b* describes the color's position on the yellow-blue axis, using D65 standard light and a 10° field of view for a standard observer. The color model is standardized in EN ISO 11664-4, "Colorimetry - Part 4: CIE 1976 L*a*b* Color space." For more information on the L*a*b* color space (also: CIELAB), see: https: / / de.wikipedia.org / wiki / Lab-Farbraum. Each color in the color space is defined by its position with Cartesian coordinates {L*, a*, b*}. The a*b* coordinate plane is constructed using the theory of opponents. Green and red are at opposite ends of the a* axis, while the b* axis runs from blue to yellow. Complementary hues are 180° opposite each other; all achromatic colors are centered between them (the coordinate origin a* = 0, b* = 0).

[0040] The L* axis describes the lightness (brightness) of a color, with values ​​ranging from 0 to 100. On the chart, it is positioned perpendicular to the a*b* plane at the origin. Since all achromatic colors (gray tones) are contained between the endpoints of black (L* = 0) and white (L* = 100), it is also called the neutral gray axis. The a* axis describes the green or red component of a color, with negative values ​​representing green and positive values ​​representing red. The b* axis describes the blue or yellow component of a color, with negative values ​​representing blue and positive values ​​representing yellow.

[0041] The a* value ranges from approximately -170 to +100, and the b* value ranges from -100 to +150, with the maximum value only reached at medium brightnesses for certain hues. The CIELAB color entity has its maximum range in the medium brightness region, but this varies in height and size depending on the color range.

[0042] According to the present invention, the color distance ΔE of the L*a*b* coordinates of the orange-like hue and the color number starting with “2” in the RAL color chart is less than 20.

[0043] Preferred orange methine dyes according to the invention

[0044] Methine dyes, also called polymethine dyes, are dyes according to https: / / de.wikipedia.org / wiki / Methinfarbstoffe#:~:text=Die%20Methinfarbstoffe%20enthalten%20eine%20ungerade,kationisch%2C%20anionisch%20oder%20neutral%20sein, in which the chromophore system consists of a conjugated double bond (polyene) flanked by two terminal groups (electron acceptor A and electron donor D), such as according to formula (I):

[0045] (I)

[0046] Methylene dyes contain an odd number of methine groups. The end group can be part of a heterocycle, and the double bond can be part of an aromatic system. This produces different subclasses of methine dyes. Methylene dyes can be characterized as polyene dyes with a terminal electron donor group and an electron acceptor group. In most cases, the end group of the methine dye contains a nitrogen or oxygen atom. However, although polyene dyes such as carotenoids that usually appear as natural dyes are limited to yellow to yellow-red tones, mainly synthetic methine dyes can achieve almost any color in the spectrum. The preferred orange methine dye for the coloring of plastics and therefore for 3D printing based on photopolymerization according to the present invention is a merocyanine dye with amino and carbonyl groups as the end groups of the polyene structural unit. This type of dye can be formulated into a neutral or zwitterionic meso standard form, such as according to formula (II).

[0047] (II)

[0048] A well-known representative of the merocyanine dyes is Macrolex® Orange R (CAS No. 185766-20-5) or Solvent Orange 107.

[0049] According to the present invention, methine dyes also preferably used for 3D printing in conjunction with plastic coloring are styryl dyes obtained by condensing active methylene compounds (e.g., malononitrile) with benzaldehyde derivatives. As a result of the integration of a benzene ring into the polyene moiety, these compounds have a styryl substructure.

[0050] Preferred embodiments of the present invention

[0051] Preferably, the urethane-acrylate resin-based composition usable according to the present invention and the 3D printed product produced therefrom have a color distance ΔE < 10 from the L*a*b* coordinates of the orange color number starting with "2" on the RAL color chart.

[0052] Particularly preferably, the urethane-acrylate resin-based composition usable according to the invention and the 3D printed products produced therefrom have a color distance ΔE <5 from the L*a*b* coordinates of the orange color number starting with "2" on the RAL color chart.

[0053] Preferably, the present invention relates to 3D-printed products based on a composition for additive manufacturing of 3D-printed products by photopolymerization-based 3D printing, wherein the color distance ΔE of the L*a*b* coordinates of the color numbers starting with "2" on the RAL color chart is <20, wherein the composition comprises at least one urethane acrylate-based resin and at least one orange methine dye having a molecular weight in the range of 50 to 1000 g / mol and a dye solubility in the urethane-acrylate resin-based composition of ≥0.05 g / L at 23°C, as determined in accordance with DIN EN ISO 7579:2010 DE.

[0054] Preferably, the present invention relates to a method for increasing the light fastness and color properties of photopolymerizable compositions based on urethane acrylate resins and 3D-printed products produced therefrom, as determined in accordance with DIN EN ISO 4892-2, by means of additive manufacturing in 3D printing, using at least one orange methine dye having a molecular weight in the range of 50 to 1000 g / mol and a solubility in the composition based on urethane acrylate resin of ≥ 0.05 g / L at 23° C., wherein the composition and the 3D-printed products have a color distance ΔE < 20 from the L*a*b* coordinates of a color number starting with “2” on the RAL color chart.

[0055] Preferably, the present invention relates to the use of at least one orange methine dye having a molecular weight in the range of 50 to 1000 g / mol for improving the lightfastness and color properties, as determined in accordance with DIN EN ISO 4892-2, of photopolymerizable urethane-acrylate resin-based compositions and 3D-printed products produced therefrom by additive manufacturing in 3D printing. These compositions and 3D-printed products have a color distance ΔE of <20 in terms of the L*a*b* coordinates of a color number beginning with "2" on the RAL color chart and a dye solubility in the urethane-acrylate resin-based composition at 23°C of ≥0.05 g / L, as determined in accordance with DIN EN ISO 7579:2010 DE. Preferred methine dyes for the use according to the invention are orange merocyanine dyes having amino and carbonyl groups as end groups of the polyene structural units, or orange styryl dyes obtained by condensing active methylene compounds with benzaldehyde derivatives and having a styrene substructure due to the integration of a benzene ring into the polyene moiety.

[0056] Preferably, the present invention relates to a 3D-printed product, the use according to the invention, and the method according to the invention for improving the light fastness and color properties of a 3D-printed product, wherein 0.005 to 5 parts by mass of a methine dye are used per 20 to 99.995 parts by mass of a urethane-acrylate-based resin, the resin preferably containing an additive.

[0057] Particularly preferably, the urethane acrylate resin comprises, in addition to at least one methine dye, 0.5 to 10 parts by mass of a photoinitiator, which preferably absorbs in the wavelength range of 300 to 450 nm.

[0058] Very particularly preferably, the urethane acrylate resin comprises, in addition to at least one methine dye and 0.5 to 10 parts by mass of a photoinitiator, 0.001 to 1 part by mass of at least one additive, preferred additives for the purposes of the present invention being at least one leveling agent, at least one stabilizer, at least one additional dye other than a methine dye, at least one filler or at least one organic pigment.

[0059] Urethane-acrylate based resins

[0060] Preferred photopolymerizable urethane-acrylate resins according to the present invention, particularly for additive manufacturing in 3D printing, are based on polyurethane acrylates [CAS No. 82116-59-4], polyether urethane acrylates, or urethane acrylate resins. Reference should be made to WO 2005 / 028532 A1, RU 2546966 C1, or M. Alishiri et al., Materials Science and Engineering: C, Vol. 42, September 2014, pp. 763-773.

[0061] Used in the context of the present invention and therefore particularly preferred is the "3D Printing UV-Sensitive Transparent Resin" from Shenzhen Anycubic Technology Co., Ltd., China; a colorless resin for high-speed light-induced 3D printing, which contains 30%-60% polyurethane acrylate (CAS No. 82116-59-4); 10%-40% isooctyl acrylate (CAS No. 29590-42-9) and 2%-5% photoinitiator.

[0062] The photopolymerizable resins useful in accordance with the present invention preferably contain, in addition to at least one dye, a mixture of at least one polymerizable monomer (preferably an acrylate) and / or prepolymer (preferably a (poly)urethane acrylate), at least one photoinitiator, and at least one additive. Regarding such additives, reference should generally be made to WO 2018 / 038954 A1, the contents of which are incorporated herein in their entirety. Preferred photoinitiators and additives are listed below.

[0063] Photoinitiator

[0064] The photoinitiators that can be used according to the invention are generally characterized by one or more of the following features,

[0065] - one or more absorption bands in the wavelength range from 300 to 450 nm and / or a solubility in the curable composition of at least 2 g / l at 23°C;

[0066] - solubility in the radiation-curable components of the curable resin composition and / or in the additives optionally present;

[0067] - The ability to form polymerization-inducing species (eg, free radicals) when exposed to light energy having a wavelength between 300 and 450 nm.

[0068] According to the invention, it is particularly preferred to use at least one photoinitiator from the following group: 2-hydroxy-2-methyl-1-phenylpropanone, 1-hydroxycyclohexylphenyl ketone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, ethyl(2,4,6-trimethylbenzoyl)phenylphosphinate.

[0069] additive

[0070] The photopolymerizable resin composition useful for 3D printing according to the present invention may preferably comprise at least one additive, stabilizer, or a mixture thereof.

[0071] In particular, adding stabilizers to the curable composition can help improve the resolution and accuracy of the SLA process by reducing or preventing undesirable scattering effects, and can also help extend the shelf life of the curable composition. Such stabilizers typically contain phenolic units. Preferred are p-methoxyphenol (MOP), hydroquinone monomethyl ether (MEHQ), 2,6-di-tert-butyl-4-methylphenol (BHT; Ionol), phenothiazine, 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO), and mixtures thereof. Such one or more stabilizers are preferably used in the following amounts:

[0072] •Lower limit: at least 0.001%, or at least 0.005%, or at least 0.01% by weight;

[0073] • Upper limit: not more than 0.02%, or not more than 0.05%, or not more than 0.5%, or not more than 1% by weight;

[0074] • Range: 0.001% to 1%, or 0.005% to 0.05% by weight;

[0075] Wherein the % by weight is based on the weight of the curable composition.

[0076] Methylene dyes

[0077] The orange methine dyes that can be used according to the invention are characterized by the following features:

[0078] •Molecular weight in the range of 50-1000 g / mol

[0079] • A solubility of at least 0.05 g / L in the curable composition at 23°C

[0080] • Maximum light absorption in the wavelength range of 400 to 560 nm

[0081] • Very good light resistance in 3D products

[0082] •Highly stable color properties during the curing process

[0083] •Contains at least one methine unit.

[0084] The methine dyes which can preferably be used according to the invention comprise at least one structure of the formula (V) in which R 1 represents a C1-C4 alkyl group, preferably a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group or a tert-butyl group, and R 2 represents a C1-C4 alkyl group, preferably a cyclohexyl group, a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, an isobutyl group or a tert-butyl group,

[0085] (V)

[0086] or they contain structural units of formula (VIII)

[0087] (VIII)

[0088] Where R represents a group:

[0089]

[0090] or group:

[0091]

[0092] And R 3 represents a C1-C4 alkyl group, preferably a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group or a tert-butyl group.

[0093] The methine dyes which can be used particularly preferably according to the invention comprise at least one structure of the formula (V), (VI) or (VII)

[0094] (V)

[0095] where R 1 represents a C1-C4 alkyl group, preferably a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group or a tert-butyl group, and R 2 represents a C1-C4 alkyl group, preferably a cyclohexyl group, a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, an isobutyl group or a tert-butyl group,

[0096] (VI)

[0097] where R 3 represents a C1-C4 alkyl group, preferably a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group or a tert-butyl group,

[0098] or

[0099] (VII).

[0100] A methine dye that can be used very particularly preferably according to the invention is methyl 1,3,3-trimethyl-2-[2-(3-methyl-5-oxo-1-phenyl-1,5-dihydropyrazol-4-ylidene)-ethylidene]-2,3-dihydroindole-5-carboxylate; Solvent Orange 107, CAS No. 185766-20-5.

[0101] The method for increasing the light resistance and color properties of a photopolymerizable urethane-acrylate resin-based composition, determined in accordance with DIN EN ISO 4892-2, is preferably used for the additive production of 3D-printed products, more preferably for additive production by photopolymerization, and especially preferably for additive production of 3D-printed products using an SLA 3D printer or a DLP 3D printer based on photopolymerization.

[0102] The present invention also relates to a method for additively producing 3D printed products in a photopolymerization-based SLA 3D printer or DLP 3D printer using a composition based on a urethane-acrylate resin, wherein the color distance ΔE of the L*a*b* coordinates of the 3D printed products to the color number starting with "2" on the RAL color chart is less than 20, and the orange methine dye has a molecular weight in the range of 50 to 1000 g / mol and a solubility in the composition based on the urethane-acrylate resin of ≥ 0.05 g / L at 23° C., as determined in accordance with DIN EN ISO 7579:2010 DE. Preferably, the orange methine dye comprises at least one structure of formula (V), wherein R 1 represents a C1-C4 alkyl group, preferably a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group or a tert-butyl group, and R 2 represents a C1-C4 alkyl group, preferably a cyclohexyl group, a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, an isobutyl group or a tert-butyl group,

[0103] (V)

[0104] or a structural unit containing formula (VIII)

[0105] (VIII)

[0106] Where R represents a group:

[0107]

[0108] or group:

[0109]

[0110] And R 3 represents a C1-C4 alkyl group, preferably a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group or a tert-butyl group.

[0111] Particularly preferably, the methine dye to be used in the method according to the invention has at least one structural unit of the formula (V), (VI) or (VII)

[0112] (V)

[0113] where R 1 represents a C1-C4 alkyl group, preferably a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group or a tert-butyl group, and R 2 represents a C1-C4 alkyl group, preferably a cyclohexyl group, a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, an isobutyl group or a tert-butyl group,

[0114] (VI)

[0115] where R 3 represents a C1-C4 alkyl group, preferably a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group or a tert-butyl group,

[0116] (VII).

[0117] Finally, the present invention very particularly preferably relates to a method for the additive production of 3D-printed products in a SLA 3D printer or DLP 3D printer based on photopolymerization, wherein the 3D-printed products have a color distance ΔE < 20 from the L*a*b* coordinates of a color number starting with "2" on the RAL color chart using a composition based on a urethane-acrylate resin containing at least one orange methine dye having a molecular weight in the range of 50 to 1000 g / mol and a solubility in the composition based on a urethane-acrylate resin of ≥ 0.05 g / L at 23° C., determined in accordance with DIN EN ISO 7579:2010 DE, wherein the methine dye is:

[0118] Methyl 1,3,3-trimethyl-2-[2-(3-methyl-5-oxo-1-phenyl-1,5-dihydropyrazol-4-ylidene)ethylidene]-2,3-dihydroindole-5-carboxylate; Solvent Orange 107, CAS No. 185766-20-5. DETAILED DESCRIPTION

[0119] Examples

[0120] Method for determining the lightfastness of dyes in 3D printing

[0121] To determine the lightfastness of dyes in 3D printing, test samples were produced for the purposes of the present invention from a colored resin based on Resin Composition 1 (see Table 6) with a dye concentration of 0.02% by weight. As test samples, rectangular parallelepipeds with the following dimensions were produced from the colored resin by 3D printing:

[0122] • Length 60 mm

[0123] • Width 40 mm

[0124] • Height 2 mm

[0125] The test specimens were exposed to light (xenon lamp) for 95–100 h using a Xenotest Beta+ apparatus (Atlas Material Testing Technology GmbH, Linsengerich-Altenhaßlau, Germany) according to DIN EN ISO 4892-2.

[0126] Light fastness was evaluated colorimetrically. This was done using an X-Rite Ci7800 sphere spectrophotometer (X-Rite GmbH, Planegg-Martinsried, Germany) to record the transmission spectra of the test specimens exposed to light. The following settings were selected for this purpose:

[0127] • Measurement geometry d / 8°

[0128] • Spectral spacing 10 nm

[0129] • Spectral range 360-750 nm

[0130] From the transmission spectra, the manufacturer's sphere spectrophotometer software calculated the colorimetric data using the following settings:

[0131] • Illuminant / Observer D65 / 10°

[0132] • Color space L*a*b*C*h°

[0133] Lightfastness evaluation is based on the color distance ΔE in the L*a*b*C*h° color space between a light-exposed test sample and a corresponding unexposed test sample. The greater the color distance, the greater the change in color perception caused by light exposure, and therefore, the worse the lightfastness. ΔE is classified based on a comparison with non-inventive orange dyes (see non-inventive examples), whose lightfastness in other applications (e.g., mass coloration of plastics) is generally rated as good according to manufacturer's data.

[0134] Table 2: Evaluation of light resistance

[0135]

[0136] *Compared to the average ΔE of non-inventive examples (see Table 5)

[0137] Method for evaluating the stability of color characteristics

[0138] To determine the changes in the spectral characteristics that determine the color characteristics of the dye, the absorption spectra of the colored resin based on Resin Composition 1 were compared before and after light-induced curing.

[0139] The colored resin, prepared as described previously, was transferred to a quartz glass cuvette with a width of 1 cm. Absorption spectra were then recorded in transmission mode using an X-Rite Ci7800 instrument (X-Rite GmbH, Planegg-Martinsried, Germany) over a wavelength range of 360 to 750 nm. These spectra were then corrected for the absorbance of the corresponding colorless resin by performing the same measurements with the colorless resin. Similarly, the absorption spectra of the colored test samples were recorded and corrected in transmission mode. In each case, the spectra were normalized to the path length of the cuvette or test sample.

[0140] The measured data is then used to calculate the similarity of the absorption spectra before and after 3D printing. This is accomplished by calculating the correlation coefficient R of the normalized absorption (spectral spacing of 10 nm). The larger the value of R, the greater the similarity of the absorption spectra, and therefore the more stable the color properties of the dye during 3D printing.

[0141] Table 3: Evaluation of stability / retention of color characteristics

[0142]

[0143] Colored 3D prints were produced and tested according to the method described above in three resin compositions (see Materials) with different properties. In resin composition 1, a dye mixture was also investigated by example.

[0144] Table 4: Inventive Example of Resin Composition "3D Printing UV-Sensitive Transparent Resin" from Shenzhen Zongwei Cube Technology Co., Ltd.

[0145]

[0146] Table 5: Non-inventive example of orange dye in the resin composition “3D printing UV-sensitive transparent resin” from Shenzhen Zongweilifang Technology Co., Ltd.

[0147]

[0148] reactants

[0149] Table 6: Materials used and sources of supply

[0150]

Claims

1. 3D printed products having a color distance ΔE of < 20 from the L*a*b* coordinates of a color number starting with "2" on the RAL color chart, wherein the 3D printed products are based on a photopolymerizable composition comprising at least one urethane acrylate resin and at least one orange methine dye having a molecular weight in the range of 50 to 1000 g / mol and a solubility in the composition based on urethane-acrylate resin of ≥ 0.05 g / L at 23°C, as determined in accordance with DIN EN ISO 7579:2010 DE.

2. The 3D printed product according to claim 1, characterized in that: The urethane acrylate resin is based on urethane acrylate, polyurethane acrylate or polyether urethane acrylate.

3. The 3D printed product according to claim 1 or 2, characterized in that: The orange methine dye is a merocyanine dye having an amino group and a carbonyl group as terminal groups of a polyene structural unit, or a styryl dye having a styrene substructure.

4. The 3D printed product according to one or more of claims 1 to 3, characterized in that The orange methine dye comprises at least one structure of formula (V), (VI) or (VII) (V) where R 1 represents a C1-C4 alkyl group, preferably a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group or a tert-butyl group, and R 2 represents a C1-C4 alkyl group, preferably a cyclohexyl group, a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, an isobutyl group or a tert-butyl group, (WE) where R 3 represents a C1-C4 alkyl group, preferably a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group or a tert-butyl group, or (VII)。 5. The 3D printed product according to one or more of claims 1 to 4, characterized in that The methine dye is 1,3,3-trimethyl-2-[2-(3-methyl-5-oxo-1-phenyl-1,5-dihydropyrazol-4-ylidene)-ethylidene]-2,3-dihydroindole-5-carboxylic acid methyl ester.

6. Use of at least one orange methine dye for increasing the light fastness and color properties determined according to DIN EN ISO 4892-2 of photopolymerizable compositions based on urethane-acrylate resins and 3D-printed products produced therefrom, characterized in that The methine dye has a molecular weight in the range of 50 to 1000 g / mol and a solubility of ≥ 0.05 g / L at 23°C in compositions based on urethane-acrylate resins, provided that these compositions based on urethane-acrylate resins and 3D-printed products produced therefrom have a color distance ΔE < 20 from the L*a*b* coordinates of the color numbers starting with "2" on the RAL color chart.

7. The use according to claim 6, characterized in that The use of the at least one orange methine dye in the additive manufacturing of 3D printed products occurs in 3D printing based on photopolymerization.

8. The use according to claim 6 or 7, characterized in that These compositions based on urethane acrylate resins are based on urethane acrylates, polyurethane acrylates or polyether urethane acrylates.

9. Use according to one or more of claims 6 to 8, characterized in that The orange methine dye is a merocyanine dye having an amino group and a carbonyl group as terminal groups of a polyene structural unit, or a styryl dye having a styrene substructure.

10. Use according to one or more of claims 6 to 9, characterized in that The orange methine dye comprises at least one structure of formula (V), (VI) or (VII) (V) where R 1 represents a C1-C4 alkyl group, preferably a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group or a tert-butyl group, and R 2 represents a C1-C4 alkyl group, preferably a cyclohexyl group, a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, an isobutyl group or a tert-butyl group, (WE) where R 3 represents a C1-C4 alkyl group, preferably a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group or a tert-butyl group, or (VII)。 11. Use according to one or more of claims 6 to 9, characterized in that The methine dye is 1,3,3-trimethyl-2-[2-(3-methyl-5-oxo-1-phenyl-1,5-dihydropyrazol-4-ylidene)-ethylidene]-2,3-dihydroindole-5-carboxylic acid methyl ester.

12. A method for increasing the light fastness and color properties of photopolymerizable urethane-acrylate resin-based compositions and 3D-printed products produced therefrom, determined according to DIN EN ISO 4892-2, characterized in that At least one orange methine dye having a molecular weight in the range of 50 to 1000 g / mol and a solubility of ≥ 0.05 g / L at 23° C. in compositions based on urethane-acrylate resins is used, provided that the color distance ΔE of these compositions based on urethane-acrylate resins from the L*a*b* coordinates of the color numbers starting with "2" on the RAL color card is <20.

13. The method according to claim 12, characterized in that The use of the at least one orange methine dye in the additive manufacturing of 3D printed products is provided in 3D printing based on photopolymerization.

14. The method according to claim 12 or 13, characterized in that These compositions based on urethane acrylate resins are based on urethane acrylates, polyurethane acrylates or polyether urethane acrylates.

15. Method according to one or more of claims 12 to 14, characterized in that The methine dye comprises at least one structure of formula (V), (VI) or (VII) (V) where R 1 represents a C1-C4 alkyl group, preferably a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group or a tert-butyl group, and R 2 represents a C1-C4 alkyl group, preferably a cyclohexyl group, a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, an isobutyl group or a tert-butyl group, (WE) where R 3 represents a C1-C4 alkyl group, preferably a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group or a tert-butyl group, or (VII)。 16. Method according to one or more of claims 12 to 14, characterized in that The methine dye is: 1,3,3-trimethyl-2-[2-(3-methyl-5-oxo-1-phenyl-1,5-dihydropyrazol-4-ylidene)-ethylidene]-2,3-dihydroindole-5-carboxylic acid methyl ester.

Images