Cleaning solution for cleaning an object produced using a 3D printing method

Abstract

The invention relates to a cleaning solution for cleaning an object produced using a 3D printing method, to a method for cleaning an object produced using a 3D printing method by means of the cleaning solution according to the invention, and to the use of the cleaning solution according to the invention to clean an object produced using a 3D printing method. The cleaning solution according to the invention comprises a carbonate and water.

Description

[0001] Cleaning solution for cleaning an object produced using a 3D printing process

[0002] The invention relates to a cleaning solution for cleaning an object produced by a 3D printing process, a method for cleaning an object produced by a 3D printing process using the cleaning solution according to the invention, and the use of the cleaning solution according to the invention for cleaning an object produced by a 3D printing process.

[0003] 3D printing processes have been known in the state of the art for some time. These are manufacturing processes in which material is deposited layer by layer to create 3D (three-dimensional) objects or workpieces. The material to be deposited is typically plastic or synthetic resin, but also ceramic. 3D printing processes are used, for example, in mechanical and automotive engineering, the aerospace industry, and medical and dental technology.

[0004] Objects produced using a 3D printing process should be cleaned after production and / or before use to remove any possible residues from the manufacturing process from their surface. These residues could include, for example, remnants of unpolymerized resin. This is particularly important in the dental field, as objects produced using a 3D printing process, especially dental objects, are used or inserted in the oral region of patients.

[0005] This cleaning can be done by hand, using ultrasonic baths, or using the now widely used mechanical cleaning method (e.g. RS wash cleaning device [Rapid Shape; Heimsheim; Germany]; Prowash / Dry [Sprintray; Los Angeles; USA]). The most commonly used cleaning method is using ultrasonic baths. Here, a solvent / cleaning agent is placed in a beaker, the object to be cleaned is added, and the object is cleaned for a specific time using an ultrasonic bath. This process is usually repeated in a beaker using clean solvent. Mechanical cleaning usually follows a similar principle (first a pre-cleaning followed by a post-cleaning), although typical solvents such as isopropanol or ethanol are also used.

[0006] Hand cleaning produces the best results, but is not commonly used in practice due to convenience. A solvent-soaked cloth or brush is used for cleaning. Visual inspection removes residues very effectively, and the short exposure time of the solvent minimizes the impact on the material properties / physics of the finished object.

[0007] Isopropanol is the most commonly used solvent / cleaning agent in 3D printing. However, its use as a cleaning fluid is associated with several disadvantages. Firstly, the use of isopropanol can lead to the formation of flammable or explosive mixtures or the formation of harmful vapors. Secondly, if the cleaning agent is left on the object for too long, it can penetrate the surface of the object, negatively altering the material properties. Furthermore, used isopropanol, which is contaminated with resin, must be disposed of in a complex manner after cleaning. Ethanol, which is also quite commonly used, has similar properties.

[0008] In addition to isopropanol, cleaners based on high-boiling glyme compounds have recently become available. Glyme compounds are ethylene glycol chains used as solvents for cleaning. While this eliminates the risk of inflammation, the other two disadvantages remain.

[0009] Cleaning is particularly problematic for filled 3D printing resins, as the fillers can form a white film on the printed restoration after cleaning, which then requires laborious removal. Such filled resins are primarily used in dentistry, such as composites, which comprise a plastic matrix with fillers or packings dispersed therein. DE 10 2019 123 104 A1 discloses a method for cleaning an object produced using a 3D printing process, in particular a dental molded part produced using a 3D printing process. The method uses a gas stream to remove adhering residues from the 3D object.

[0010] An object of the invention is to overcome the above-mentioned disadvantages of the prior art.

[0011] It is a further object of the invention to provide a cleaning solution which cleans 3D-printed objects of residues and / or dirt and at the same time does not negatively influence the material properties of the 3D-printed object to be cleaned, in particular a 3D-printed dental object to be cleaned.

[0012] It is also an object of the invention to provide a cleaning solution which cleans 3D objects made of composite and at the same time does not leave a white film on the cleaned 3D object.

[0013] It is a further object of the invention to provide a method for cleaning objects produced by a 3D printing process, wherein the method should be simple and fast.

[0014] The invention therefore provides a cleaning solution for cleaning 3D-printed objects, characterized in that the cleaning solution comprises a carbonate and water. Carbonates are esters of carbonic acid, the preparation of which is known in the art. Surprisingly, it has also been found that particularly good results are achieved with a close mixing ratio of water to carbonate in the cleaning solution.

[0015] The invention offers numerous advantages. Using the cleaning solution according to the invention, objects produced using a 3D printing process can not only be reliably cleaned, but their material properties, such as flexural strength, can also be preserved.

[0016] A further advantage of the invention lies in the cleaning of composite objects produced using a 3D printing process. A composite comprises, or consists of, a plastic matrix with fillers dispersed therein. The fillers are typically made of glass or quartz, which are dispersed in the matrix. After cleaning such composite-containing 3D objects, no white film remains on the surface of the cleaned 3D-printed objects.

[0017] A further advantage of the invention lies in its reprocessing capability. After the cleaning process, the used cleaning solution can be recycled by exposure to light and subsequent filtration. Resin residues detached from the cleaned 3D object harden and can then be easily separated.

[0018] Suitable carbonates are organic carbonates such as diethyl carbonate (CAS No. 105-58-8), ethylene carbonate (CAS No. 96-49-1), propylene carbonate (CAS No. 108-32-7), and butylene carbonate (CAS No. 4437-85-8), although this list is not exhaustive. Propylene carbonate exists in two stereoisomers (CAS No. 51260-39-0 and CAS No. 16606-55-6), each of which can be used individually or as a racemic mixture.

[0019] The carbonate is preferably selected from the group consisting of diethyl carbonate, ethylene carbonate, propylene carbonate, butylene carbonate, and mixtures thereof. The carbonate may therefore comprise not only a single component, such as propylene carbonate, but may also comprise a mixture of, for example, ethylene carbonate and propylene carbonate. If the carbonate is present as a mixture of two or more components, the mixing ratios between the two or more components are freely selectable.

[0020] Preferably, the carbonate comprises propylene carbonate, more preferably the carbonate consists of propylene carbonate.

[0021] The mixing ratio of carbonate to water in the cleaning solution varies from carbonate to carbonate and depends on the miscibility of the carbonate with water. For example, the mixing ratio of the preferred propylene carbonate to water in the cleaning solution is preferably between 17:83 and 21:79 by weight, more preferably between 18:82 and 20:80 by weight, and most preferably between 18.5:81.5 and 19.5:80.5 by weight based on the total weight of the cleaning solution.

[0022] The water can preferably be distilled water or non-distilled water. Non-distilled water is, for example, tap water or spring water. Non-distilled water typically contains trace elements, organic substances, microorganisms, and / or other contaminants that can reduce the quality of the water. Non-distilled water can also be used for the cleaning solution according to the invention, especially if its quality or purity is sufficient. Otherwise, distilled water is preferable. The water is preferably distilled water.

[0023] The cleaning solution may additionally contain a solvent such as isopropanol, ethanol, acetone, or a glycol compound and / or a glyme compound. Preferably, however, the cleaning solution does not contain any of these solvents, glycol compounds, and / or glyme compounds.

[0024] The invention further provides a method for cleaning an object produced using a 3D printing process. The method for cleaning an object produced using a 3D printing process comprises, or consists of, the steps of a) providing an object produced using a 3D printing process, b) cleaning the object produced using a 3D printing process with a cleaning solution according to the invention.

[0025] Preferably, the object produced using a 3D printing process is a dental object.

[0026] Preferably, the dental object is a denture base, a model of a denture base, a denture tooth, a model of a denture tooth, a dental crown, a model of a dental crown, a filling, a model of a filling, a set of teeth, a model of an artificial set of teeth, a dental model, a model of an oral cavity for setting up dentures, a bite splint, a drilling template, an individual impression tray, a gum mask, a complete denture, a model of a complete denture, a try-in, an orthodontic appliance, an inlay, a model of an inlay, an onlay, a model of an onlay, a veneer, a model of a veneer, an implant, a model of an implant, a bridge construction or a model of a bridge construction, whereby this list is not exhaustive.

[0027] The dental object preferably comprises a composite, or the dental object preferably consists of a composite. The composite preferably comprises or consists of a plastic matrix and a filler. The plastic matrix preferably comprises or consists of an acrylate resin, an epoxy resin, or a vinyl ester resin. All resins are preferably cured, i.e., already fully polymerized. The acrylate resin preferably comprises or consists of a methacrylate resin. The methacrylate resin preferably comprises bis-glycidyl dimethacrylate resin (BisGMA) and / or urethane dimethacrylate resin (UDMA).

[0028] Preferably, the filler comprises an inorganic filler or the filler consists of an inorganic filler. The inorganic filler preferably comprises or consists of a glass and / or quartz; more preferably, the inorganic filler comprises a glass. The glass preferably comprises or consists of a dental glass. Dental glass is commercially available, for example, from Schott AG.

[0029] In a preferred embodiment, the composite comprises a methacrylate resin, in particular a cured methacrylate resin, and dental glass.

[0030] The cleaning time in step b) is preferably 1 to 10 minutes, more preferably 2 to 4 minutes. Cleaning in step b) can be done manually or mechanically. Manual cleaning is, for example, cleaning the 3D-printed object with a brush or sponge using the inventive cleaning solution. Mechanical cleaning is, for example, cleaning the 3D-printed object in an ultrasonic bath using the inventive cleaning solution or by cleaning the 3D object in a separate device such as RS wash (Fa Rapid Shape; Heimsheim; Germany). Cleaning in step b) is preferably done mechanically, preferably in an ultrasonic bath.

[0031] Cleaning step b) can be performed once or repeated, the latter particularly to remove stubborn contaminants and / or residues on the surface of the 3D-printed object to be cleaned. These residues are typically residues of materials used in the manufacturing process.

[0032] Cleaning step b) is preferably repeated, with each repetition of step b) being carried out using a fresh cleaning solution. Fresh cleaning solution is understood to mean an unused or new cleaning solution.

[0033] All preferred embodiments of the inventive cleaning solution as described herein are also preferred embodiments of the inventive method for cleaning an object produced by a 3D printing process, where applicable.

[0034] The present invention further provides the use of the cleaning solution according to the invention for cleaning an object produced by a 3D printing process.

[0035] All preferred embodiments of the inventive cleaning solution as described herein as well as all preferred embodiments of the inventive method for cleaning an object produced by a 3D printing process are also preferred embodiments of the use according to the invention, if applicable.

[0036] The invention will now be explained in more detail with reference to the following examples.

[0037] EXAMPLES

[0038] Measurement methods

[0039] The bending strength is determined using 2 x 2 x 25 mm 3Printed rods were measured according to DIN EN ISO 4049 [Dentistry - Polymer-based restorative materials (ISO 4049:2019)]. Flexural strength is considered the most suitable physical parameter in the dental field. The cleaning effect was assessed visually. The homogeneity of the cleaning solutions was also assessed visually.

[0040] Purification attempts

[0041] In a series of experiments, dental crowns produced using a 3D printing process were cleaned using conventional cleaning agents as well as the cleaning solution according to the invention.

[0042] The 3D-printed dental crowns or rods comprise a methacrylate-based 3D resin (Crowntec, Saremco Dental AG) coated with a dental glass filler. The cleaning times are as shown in Tables 1 and 2. In the case of two cleaning steps, e.g., two 3-minute cleaning cycles, fresh conventional cleaning agent or inventive cleaning solution was always used for the second cleaning step.

[0043] The cleaning method "ultrasonic bath with isopropanol, ethanol, or butyldiglycol" resulted in a deterioration of the physical properties of the cleaned objects (Table 1). In addition, a whitish layer formed on the surface of the dental crowns. All tests were conducted at room temperature. The results can be found in Table 1 below.

[0044] Table 1 Results of cleaning tests with different cleaning methods; If two cleaning times are mentioned, the second cleaning was always carried out with a new, clean solvent.

[0045] * Metanova Cleaning Liquid [Metaux Precieux Dental GmbH; Stuttgart] contains butyl diglycol (CAS No. 112-34-5).

[0046] An inventive cleaning agent consisting of water and propylene carbonate (PC) was then used, and the mixing ratio of water to propylene carbonate was varied, see Table 2. It was found that at mixing ratios of water to PC greater than 82:18 wt.%, the cleaning effect decreases somewhat. At concentrations less than 75:25 wt.%, the cleaning effect is very good, but the flexural strengths are reduced. A whitish layer was not observed. All tests were carried out at room temperature. The results can be found in Table 2 below. Table 2 Results of the cleaning tests with different mixing ratios of water to propylene carbonate (PC); if two cleaning times are given, the second cleaning was always carried out with a new, clean solvent. ng not measured

[0047] As the table shows, many different mixing ratios were tested. The results showed that a mixture of 81 ±0.5 wt.% water with 19 ±0.5 wt.% propylene carbonate produced the best results. With higher water content, the cleaning effect decreased; with higher propylene carbonate content, the cleaning effect remained roughly the same, but the physical properties decreased. In addition, the cleaning solution separated, making the cleaning process more difficult.

[0048] By adding solvent, it is possible to prevent separation into two phases. Table 3 shows the results of such measurements. Here, the mixture of water:carbonate, which is not homogeneous under normal conditions, was used in a ratio of 80:20, and a small amount of solvent was added.

[0049] Table 3 Results of cleaning tests with mixing ratios of water to propylene carbonate (PC) to a solubilizer; if two cleaning times are given, the second cleaning was always carried out with a new, clean solvent.

[0050] As the table shows, homogeneous mixtures can be produced this way. The physical properties are reduced, but still significantly better than those with pure solvents. Furthermore, no whitish layer remains. However, the results without the solubilizer are even better compared to these homogeneous mixtures. Nevertheless, the homogeneity range can be further expanded. This is especially important if the cleaner is to be used at lower temperatures, as demixing can occur under such conditions. Furthermore, the cleaning effect can be improved at lower propylene carbonate contents.

Claims

Claims Cleaning solution for cleaning an object produced using a 3D printing process, characterized in that the cleaning solution comprises a carbonate and water. Cleaning solution according to claim 1, wherein the carbonate is selected from the group consisting of diethyl carbonate, ethylene carbonate, propylene carbonate, butylene carbonate, and mixtures thereof. Cleaning solution according to one of the preceding claims, wherein the carbonate comprises propylene carbonate or consists of propylene carbonate. Cleaning solution according to one of the preceding claims, wherein the carbonate consists of propylene carbonate. Cleaning solution according to one of the preceding claims, wherein the mixing ratio of propylene carbonate to water in the cleaning solution is between 17:83 weight percent and 21:79 weight percent, based on the total weight of the cleaning solution.Cleaning solution according to one of the preceding claims, wherein the mixing ratio of propylene carbonate to water in the cleaning solution is between 18.5:81.5 weight percent and 19.5:80.5 weight percent, based on the total weight of the cleaning solution. Cleaning solution according to one of the preceding claims, wherein the water is distilled water. Method for cleaning an object produced by a 3D printing process, comprising the steps of a) providing an object produced by a 3D printing process, b) cleaning the object produced by a 3D printing process with a cleaning solution according to one of claims 1 to 5. The method according to claim 8, wherein the object produced using a 3D printing process is a dental object. The method according to claim 8, wherein the dental object is a denture base, a model of a denture base, a denture tooth, a model of a denture tooth, a dental crown, a model of a dental crown, a filling, a model of a filling, a set of teeth, a model of an artificial set of teeth, a dental model, a model of an oral cavity for setting up dentures, a bite splint, a drilling template, an individual impression tray, a gum mask, a complete denture, a model of a complete denture, a try-in, an orthodontic appliance, an inlay, a model of an inlay, an onlay, a model of an onlay, a veneer, a model of a veneer, an implant, a model of an implant, a bridge construction, or a model of a bridge construction. The method according to one of claims 8 or 9, wherein the dental object comprises a composite.Use of a cleaning solution according to any one of claims 1 to 7 for cleaning an object produced by a 3D printing process.

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