PVC material for 3D printing and methods for printing it

Abstract

A polymer-containing material for 3D printing consists of at least two base polymers A and B, wherein the first base polymer A is present in a concentration of at most 95 phr and simultaneously more than 50 phr, and together with the second base polymer B and optionally further base polymers, forms a total concentration of 100 phr. Here, the first base polymer A is polyvinyl chloride (PVC) with a K-value of less than 54, and the second base polymer has a K-value of at least 55, and wherein the second base polymer contains at least one component with a K-value between 55 and 59, preferably 57.

Description

[0001] The invention relates to a PVC-based material, such as a filament for 3D printing, and a method for processing the same. Technical field

[0002] Window and door frames were formerly mostly made of wood. Nowadays, they are mostly made of polyvinyl chloride (PVC) or aluminum-PVC composite profiles.

[0003] Polyvinyl chloride (PVC) is a widely used synthetic polymer employed in a variety of applications across the construction, healthcare, electronics, and many other sectors. PVC's versatility, recyclability, and low cost of production make it an important material for numerous applications. Furthermore, PVC exhibits high chemical resistance. State of the art

[0004] PVC profiles for doors and windows are usually extruded, while aluminum parts are extruded. These manufacturing processes result in straight profiles, so windows and doors are typically rectangular.

[0005] Windows with intricate contours, such as the world-famous window above the entrance of Notre-Dame Cathedral, cannot therefore be manufactured using extruded profiles.

[0006] Exotic shapes that are difficult or impossible to produce using conventional manufacturing methods can be manufactured using 3D printing. This involves applying material in multiple thin layers on top of each other to create complex three-dimensional objects.

[0007] In 3D printing, also known as additive manufacturing (AM), it is crucial to ensure that the material is processable and possesses the desired material properties afterward. Consequently, not all materials can be printed, or their properties may change compared to conventional manufacturing methods.

[0008] EP 3365380 B1 describes vinyl chloride polymers and compositions for additive manufacturing processes. The basis here is polyvinyl chloride (PVC) with a K-value of 57 or alternatively 50.

[0009] Like the viscosity number, the K-value is a quantity that characterizes the average molar mass (molecular chain length). The K-value is a constant that is independent of the concentration of the polymer solution and is characteristic of the polymer under investigation.

[0010] In PVC filaments, certain substances are added to a PVC base. Their concentration is usually given in parts per hundred rubber (phr). This refers to the mass fractions of the individual mixture components in a polymer mixture. The values ​​are based on 100 parts by mass of the base polymers.

[0011] The filaments known from EP 3365380 B1 contain, in particular, calcium carbonate at a concentration of 20 phr. A commercially available plasticizer, also at a concentration of 20 phr, is added to some of these filaments. Titanium dioxide, at a constant concentration of 4 phr, provides the white color. Furthermore, some of the filaments contain 10 phr of a copolymer.

[0012] From DE 1569386 A1, vinyl chloride mixtures for the manufacture of objects using the blow molding process are known, in which vinyl chloride components with different K-values ​​are mixed together. Task

[0013] Since PVC has excellent material properties for window frames, particularly regarding thermal insulation and durability under climatic influences, there is a need to produce PVC profiles using additive manufacturing to enable complex shapes. Additive manufacturing requires a suitable plastic material, such as a filament. A filament is a thermoplastic material that is processed in wire form on spools. The filament or other material is heated in the 3D printer and applied layer by layer through a nozzle. The filament must be fluid within the printer and solidify relatively quickly outside the printer to allow for the creation of a solid structure. A layer must not deform significantly under the influence of the next layer.Unlike PVC extrusion, 3D printing is said to eliminate the need for tool run-up with significant amounts of scrap before reaching a stable production state. This also allows for small batch sizes.

[0014] The higher melting point of PVC compared to other plastics presents a further challenge for 3D printing, as it necessitates high printing temperatures, which also impacts the printer and print nozzles. Overheating PVC can release harmful fumes, including hydrogen chloride (HCl). These fumes are hazardous to health and can corrode printing equipment. Furthermore, adhesion problems are common. The bond between printed layers can be problematic, resulting in weak or fragile parts. Adhesion to the print bed can also be difficult. A major challenge is PVC's tendency to warp. PVC tends to deform during cooling, which can lead to inaccurate or incomplete prints.

[0015] Another requirement is the white color that the 3D-printed product should have, matching the standard white of PVC extrusion windows. Furthermore, the 3D-printed products must be bondable or weldable to extruded PVC products.

[0016] The object of the invention is therefore to create a PVC-based material suitable for 3D printing, preferably of white products, and a method for processing it, including the parameters in the 3D printing slicer and on the 3D printer, which has a higher thermal stability and a lower viscosity than PVC-based material used in conventional processing methods such as extrusion, and enables a relatively high printing speed. Description of the invention

[0017] The invention solves this problem by providing a material with the features of the independent claim and a method for processing this material.

[0018] A polymer-containing material according to the invention for 3D printing consists of at least two base polymers A and B. The first base polymer A is present in a concentration of less than 95 phr and simultaneously in a concentration of more than 50 phr; that is, in at least half of the polymer-containing base polymers. The two base polymers A and B, and optionally further base polymers, together constitute 100 phr. Here, the first base polymer A is polyvinyl chloride (PVC) with a K-value of less than 54. The second base polymer has a K-value of at least 55. The second base polymer contains at least one component with a K-value between 55 and 59, preferably 57.

[0019] This type of material has proven to be both easily processable using 3D printing and thermally stable.

[0020] All other additives to the polymer-containing material refer in their concentration to the aforementioned 100 phr.

[0021] Advantageous configurations result from the characteristics of the dependent claims.

[0022] It is particularly advantageous if the first base polymer A is polyvinyl chloride (PVC) with a K-value between 48 and 52, preferably 50.

[0023] It has also proven to be very advantageous if the second base polymer B contains polyvinyl chloride (PVC) and / or a copolymer.

[0024] The combination of the aforementioned two basic polymers with different K-values ​​is particularly easy to process and exhibits favorable material properties.

[0025] According to a positive embodiment of the invention, the polymer-containing material contains titanium dioxide at a concentration of at least 4 phr. Titanium dioxide acts as a whitening agent. A higher concentration has a negative impact on other material properties.

[0026] According to a positive embodiment of the invention, the polymer-containing material contains chalk in a concentration of between 1 and 5 phr. The viscosity of the mixture is influenced by the chalk.

[0027] Optionally, the polymer-containing material contains a tin stabilizer in a concentration of between 2 and 7 phr. Tin stabilizers are used to improve thermal stability, ensure good processability of the mixture, produce a homogeneous melt, and prevent surface defects. The polymer-containing material can optionally contain a calcium-zinc stabilizer for the same purpose. Calcium-zinc stabilizers promote a balanced ratio of internal and external lubrication and give the product good flowability during manufacturing.

[0028] Certain additives have beneficial effects: A low molecular weight acrylic dispersion aid, preferably in a concentration between 10 and 30 phr, is used for processing; this ensures good mixing.

[0029] An acrylic shell-core processing aid, preferably in a concentration up to 2 phr, serves as a lubricant.

[0030] A plasticizer is also advantageous, preferably based on phthalates, acrylates, aliphatic diesters or epoxides, preferably in a concentration between 10 and 20 phr, so that the product does not become brittle.

[0031] An impact modifier should preferably be based on acrylates, polyesters, polyethylene or chlorinated polyethylene (CPE) and should further preferably be present in a concentration up to 10 phr.

[0032] Color pigments, preferably in a concentration of up to 0.1 phr, are used for coloring.

[0033] Advantageously, the material is available in filament, granules, pellets, a dry mix, and / or powder to be suitable for various applications. Filaments are used, for example, in Fused Deposition Modeling (FDM), granules in Material Extrusion (ME), and powder in Powder Bed Fusion (PBD).

[0034] In a method for printing a polymer-containing material according to the invention, the printing temperature is preferably between 190 and 230°C, more preferably between 200 and 210°C. A preferred bed temperature is between 30 and 80°C, more preferably between 60 and 75°C. According to an advantageous embodiment, the printed area is preferably cooled with air after printing so that no deformation can occur after rapid solidification.

[0035] The polymer-containing material described above differs significantly from PVC compounds used in extrusion processes. In particular, it has good thermal stability properties.

[0036] The materials mentioned are usually not used in their pure form, but rather blended into a masterbatch. Masterbatches are mixtures that contain both the substance with the specific property and additives that positively influence technical process reliability. These additives can, for example, improve mixing.

[0037] The following table shows material mixtures suitable for 3D printing with PVC. The different mixtures vary in terms of cracking susceptibility, surface finish, and stability, so the most suitable mixture may depend on the specific application. Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 phr phr phr phr phr phr PVC K50 95 80 80 70 70 60 PVC K57 5 30 20 Copolymer (K57) 20 20 30 20 Shell Core Processing Aid 0,25 0,55 0,1 Polyethylene wax 0,2 0,3 0,4 Oxidized polyethylene wax 1 0,1 0,15 0,1 Oxidized polyethylene wax 2 0,1 0,05 0,1 0,05 Fischer-Tropsch wax 0,1 0,2 0,5 Internal lubricant 1 0,5 0,7 1 low molecular weight acrylic dispersion aid 10 25 8 10 10 12 Plasticizers 12 7,5 Impact modifier 1 7 7 7 Impact modifier 2 8,25 6,25 Metal soap 0,4 0,5 0,5 0,3 Decanted chalk 2 2 6 2 4 2 Calcium-zinc stabilizer 5 5 Tin stabilizer 4 4 4 4 titanium dioxide 5 5 5 5 5 5 Color pigment 0,05 0,05 0,05 0,05 0,05 0,05 Sum: 142,05 150,85 125 129,55 132,35 132,65

[0038] Sample 1 is characterized by the fact that the PVC consists almost entirely of a PVC with a K-value of 50; only 5 phr of the base polymer consists of PVC with the higher K-value of 57. To improve flow properties and prevent sticking to hot metal surfaces, a shell-core processing aid is used. This shell-core processing aid has a high-molecular-weight PMMA shell and a core made of a low-molecular-weight acrylic polymer. This gives the processing aid a powder-like consistency. The outer shell ensures good gelation. The inner core has only external lubricating properties and is released only during product processing. An oxidized polyethylene wax acts as a lubricant, thus facilitating extrusion from the print nozzle. Oxidized polyethylene wax has a high viscosity and a high softening point hardness.A low molecular weight acrylic dispersion aid reduces the melt viscosity of the mixture and contributes to improved gelation speed. It also enhances impact strength. An acrylic polymer plasticizer acts as a soft impact modifier, promoting particularly weather-resistant applications, allowing the printed product to withstand environmental influences. An acrylic impact modifier contributes to good weather resistance. Chemical bonding with the polymer matrix results in increased ductility. A tin stabilizer based on methyltin mercaptide facilitates easier processing, reduces chipping, produces a more homogeneous melt, and minimizes surface defects. A metal soap based on calcium distearate acts as an external lubricant and co-stabilizer in PVC processing, improving melt flow and yield.The metallic soap prevents the softened filament from adhering to the nozzle walls and thus prevents nozzle clogging. Precipitated chalk based on ultrafine, surface-treated, precipitated calcium carbonate with a mean particle diameter of 0.07 µm allows for good control of rheological properties such as yield point, viscosity, and anti-lumping behavior. Titanium dioxide acts as a white pigment. In addition, a specific color pigment is used.

[0039] Sample 2 differs from Sample 1 primarily in that the proportion of PVC with a K-value of 50 is reduced from 95 to 80 phr. The remaining base polymer is present as a copolymer with a K-value of 57. Sample 2 contains largely the same additives in different concentrations. Polyethylene wax is omitted as a lubricant in this mixture. Sample 2 has a relatively high proportion of low molecular weight acrylic dispersing agent.

[0040] Probe 3 features an internal lubricant based on fatty acid esters; this has low volatility and high compatibility, resulting in improved rheological properties, optimized machine performance, and improved surface finish of the final product.

[0041] Sample 4 is distinguished, among other things, by an even lower PVC content with a K-value of 50. Furthermore, it contains a mixture of several polyethylene waxes. Compared to samples 1 to 3, a different impact modifier is used, which is particularly suitable for window profiles.

[0042] Samples 5 and 6 use a calcium-zinc stabilizer instead of a tin stabilizer. Sample 6 differs from the other samples in that it uses PVC with a K-value of 50, PVC with a K-value of 57, and a copolymer with a K-value of 57.

[0043] Some of the components can be used alternatively, and others cooperatively. The mixtures, in the concentrations specified in the claims, are particularly suitable for window profiles and differ in detail with regard to their processing properties and the material properties of the 3D-printed profiles. The specific samples mentioned are merely examples. Mixtures containing components of various mentioned samples also belong to the mixtures according to the invention.

Claims

[1] Polymer-containing material for 3D printing, wherein the material consists of at least two basic polymers A, B, the first base polymer A is present in a concentration of a maximum of 95 phr and simultaneously more than 50 phr, and together with the second base polymer B and optionally other base polymers form 100 phr, characterized by , that The first basic polymer A polyvinyl chloride (PVC) with a K-value of less than 54 is the second base polymer has a K-value of at least 55 and the second base polymer contains at least one component with a K-value between 55 and 59, preferably 57. [2] Polymer-containing material according to claim 1, characterized by , that the first basic polymer A is polyvinyl chloride (PVC) with a K-value between 48 and 52, preferably 50. [3] Polymer-containing material according to claim 1 or 2, characterized bythat the second base polymer contains polyvinyl chloride (PVC) and / or a copolymer. [4] Polymer-containing material according to any one of claims 1 to 3, characterized by that the material contains titanium dioxide in a concentration of at least 4 phr. [5] Polymer-containing material according to any one of claims 1 to 4, characterized by that the material contains chalk in a concentration of between 1 and 5 phr. [6] Polymer-containing material according to any one of claims 1 to 5, characterized by that the material contains a tin stabilizer or calcium zinc stabilizer in a concentration between 2 and 7 phr. [7] Polymer-containing material according to any one of claims 1 to 6, characterized by that the material a low molecular weight acrylic dispersing aid, preferably in a concentration between 10 and 30 phr and / or an acrylic shell-core processing aid, preferably in a concentration up to 2 phr and / or an oxidized polyethylene wax, preferably in a concentration up to 0.2 phr and / or a polyethylene wax, preferably in a concentration up to 0.5 phr and / or a Fischer-Tropsch wax, preferably in a concentration up to 0.8 phr and / or a plasticizer, preferably based on phthalates, acrylates, aliphatic diesters or epoxides, preferably in a concentration between 10 and 20 phr and / or an impact modifier, preferably based on acrylates, polyesters, polyethylene or chlorinated polyethylene (CPE), preferably in a concentration up to 10 phr and / or Color pigments, preferably in a concentration up to 0.1 phr contains. [8] Polymer-containing material according to any one of claims 1 to 7, characterized bythat the material is a filament, granules, pellets, a dry mix and / or powder. [9] Method for printing a material according to any one of claims 1 to 8, characterized by that the printing temperature is between 190 and 230°C, preferably between 200 and 210°C and / or the bed temperature is between 30 and 80°C, preferably between 60 and 75°C and / or the printing area is preferably cooled by air after printing.