RU2792100C1 - Method for producing a semi-rigid harness based on carbon fiber and super engineering plastics in one stage of impregnation for 3d printing by fused deposition modelling method - Google Patents

Abstract

FIELD: 3D printing.

SUBSTANCE: invention relates to the field of three-dimensional printing, namely, to a method for producing a semi-rigid bundle based on carbon fiber and super engineering plastics in one stage of impregnation for 3D printing by fused deposition modelling. The method is carried out in the following way: carbon fiber is placed in an impregnating bath for impregnation with a solution of a polymer binder. Then molded at temperatures of 240-450°C in the process of drying from the solvent using metal dies with a diameter of at least 20% of the linear width of the original carbon fiber, installed directly in the drying oven. After that, the hot fiber leaving the furnace is passed through at least three guide rollers, while after each guide roller the direction of the hot fiber is changed to 90°, after which the resulting bundle is wound on a coil.

EFFECT: producing a semi-rigid bundle based on carbon fiber and super engineering plastics in one stage of impregnation for 3D printing by fused deposition modelling.

1 cl, 1 dwg

Description

Technical field

The invention relates to the field of three-dimensional printing, namely, to a method for producing a semi-rigid bundle based on carbon fiber and superstructural plastics in one stage of impregnation for 3D printing by layer-by-layer deposition.

State of the art

Fused Deposition Printing (FDM) is an additive manufacturing process that is realized through the extrusion of materials. In FDM, an object is built by applying molten material according to a predetermined algorithm/layer by 31 layers. The materials used are thermoplastic polymers and are filament-shaped. The nature of the material directly affects the mechanical properties and accuracy of printing, as well as its price.

For the manufacture of composite materials reinforced with continuous carbon fiber (CF), by layer-by-layer deposition, special preparation of the fiber is required. This is necessary, on the one hand, to ensure the manufacturability of the printing process, on the other hand, to uniformly impregnate the fiber with a polymer binder, which can be characterized by its low porosity.

There are two approaches to the implementation of continuous fiber printing technology.

The first approach is to impregnate the fiber with a binder directly during the printing process. In this case, the problem of incomplete impregnation of the fiber arises, since the polymer melt has a high viscosity and, moreover, is usually quite polar, while carbon fiber is non-polar in nature. As a result, the final product contains many cavities and defects, which significantly reduce its strength. To improve the impregnation of the fiber, it is treated with special compounds (sizing agents) that increase its surface energy and polarity, facilitating the process of impregnation with a viscous polymer melt. In addition, the sizing increases the adhesion of the hydrocarbon to the binder, which also has a positive effect on the strength of the composite product.

The disadvantage of this approach is the low manufacturability of the process: fiber impregnation directly during the printing process carries a technological difficulty - soft carbon fiber is difficult to feed into the print head of a 3D printer.

The second approach is co-extrusion technology. To implement it, carbon fiber is pre-impregnated with a polymer solution or melt and formed into a thin rigid composite thread, which is then fed into the printer's print head along with a polymer binder filament. This approach greatly facilitates the technological support of the printing process.

A known method for producing a continuous composite material from a thermoplastic resin reinforced with carbon fiber (CN 110576531 A, IPC B29B 15/14; B33Y 70/00, 12/17/2019), which consists in the fact that the fiber bundle is aligned by pulling through a series of spacer pins, then drawn through an impregnation head which includes a plurality of resin channels. The resin melt is applied to the expanded fiber tow from one or more directions to completely impregnate the fiber tow. The prepreg fiber tow is then drawn into a tapering die that removes excess resin and becomes a printable filament. An inclined drive roller is used to draw out the fiber bundle with sufficient force to overcome dry and viscous friction in the system components.

A known method of three-dimensional printing using reinforced fiber (US 2019232550, IPC B29B 15/14, B29C 48/154, 08/01/2019), which includes the preparation of a digital 3D model of the part, pre-impregnation of the reinforced thread with molten matrix polymer under pressure, supply reinforced filament into the extruder of the print head of the 3D printing machine, heating the reinforced filament to a temperature exceeding the melting point of the matrix polymer, extruding the reinforced filament onto the surface of the part to form a layer of thermoplastic composite material, adjusting the feed rate of the reinforced filament and trimming it, repeating the cycle until complete formation details.

Also known is a method for three-dimensional printing with a thermoplastic composite material (RU 2722944, IPC V29S 48/78, V29V 15/14, 06/05/2020), in which the reinforced thread is pre-impregnated with a molten matrix polymer under pressure, the reinforced thread is dried, the reinforced thread is fed into the extruder of the print head, heating the reinforced filament to a temperature exceeding the melting point of the matrix polymer of the reinforced filament, extruding the reinforced filament onto the surface of the part to form a welded layer of composite material with trimming the reinforced filament. After the reinforced thread is fed into the 3D printing zone, it is welded under simultaneous exposure to a temperature exceeding the melting temperature of the matrix material of the reinforced thread and ultrasonic vibrations. The printing process is carried out in a thermostatically heated chamber. As a result, it is possible to manufacture parts of complex geometry.

The disadvantage of using coextrusion technology is the impossibility of complete uniform impregnation of the fiber with such viscous systems as, for example, pre-ceramic mixtures, while the finished composite fiber is not impregnated during printing due to the dense polymer layer on the surface.

Disclosure of the essence of the invention

The technical problem to be solved by this technical solution is the creation of a technological method for producing a semi-rigid bundle based on carbon fiber and superstructural plastics in one stage of impregnation for 3D printing by layer-by-layer deposition.

The technical result of the invention is to improve the manufacturability of 3D printing of a composite product by layer-by-layer deposition and reduce the porosity of the finished composite product.

To achieve a technical result, a method is proposed for obtaining a semi-rigid bundle based on carbon fiber and superstructural plastics in one stage of impregnation for 3D printing by layer-by-layer fusing, characterized in that carbon fiber is placed in an impregnation bath for impregnation with a solution of a polymer binder, then molded at temperatures of 240 ° C - 450°C during drying from the solvent using metal dies with a diameter of at least 20% of the linear width of the original carbon fiber, installed directly in the drying oven, after which the hot fiber leaving the oven is passed through at least three guide rollers, with In this case, after each guide roller, the direction of the hot fiber is changed by 90°, after which the resulting bundle is wound on a bobbin.

The combination of the above essential features leads to the fact that:

- the manufacturability of 3D printing of a composite product by the method of layer-by-layer deposition is improved due to the use of composite materials reinforced with continuous carbon fiber (CF), a semi-rigid bundle based on carbon fiber and superstructural plastics obtained in one stage of impregnation for printing;

- the porosity of the finished composite product is reduced due to the fact that the carbon fiber intended for reinforcing the superstructural plastic is pre-impregnated with a polymer binder solution and then formed into a bundle at high temperatures during drying from the solvent using metal dies of a given diameter installed directly in the drying oven , after which the formed fiber is rolled through rollers to reduce the rigidity of the tow at an angle of 90 ° to create additional pressure.

Brief description of the drawings

In FIG. shows the layout of the rolling rollers, where the numbers indicate:

1 - rolling rope, 2 - rolling rollers, 3 - drying oven Implementation and examples of implementation Below is an example of a specific implementation of the device, which does not limit the options for its implementation.

To solve this technical problem, it is proposed to create a semi-rigid carbon fiber that combines the advantages of both approaches: fiber impregnation with a binder directly during printing, on the one hand, and co-extrusion technology, such a fiber will be rigid enough to automatically advance into a 3D printer, on the other hand, it will not will be completely impregnated with polymer, which will allow impregnation during the printing process, bypassing the additional stage of manufacturing a composite fiber. At the same time, the claimed technical result is achieved - improving the manufacturability of 3D printing of a composite product by layer-by-layer deposition, reducing the porosity of the finished composite product, due to a combination of technological parameters for the production of semi-rigid hydrocarbons: the concentration of the impregnating composition, the temperature of the drying oven and the geometry of the impregnation plant.

As a polymer binder solution, a composition is selected that is similar in nature to the composition of a polymer or polymer-ceramic binder, which will later be used to print the product. The concentration of the solution is selected in the range from 5% to 20%. When CF is dressed with a polymer binder solution with a concentration below 5%, it is impossible to obtain a rigid composite fiber having sufficient rigidity for 3D printing by layer-by-layer fusing; when CF is treated with a polymer binder solution with a concentration above 20%, a continuous polymer layer is created on the fiber surface, which prevents polymer impregnation during the printing process due to the already formed dense layer of polymer on the surface.

The impregnated fiber is formed in the process of drying from the solvent at a temperature of 240-450°C using metal dies of a given diameter, installed directly in the drying oven. To give the desired diameter and round section to the resulting bundle, stainless steel dies with the required diameter are installed in the drying oven. Forming dies are installed at the entrance to the drying oven, as well as before leaving it. A forming die installed at the furnace inlet removes excess impregnating composition and promotes additional penetration of the solution deep into the fiber, which is especially important for tows containing a large number of filaments and having a significant thickness. A spinneret installed at the outlet of the furnace forms a round cross-section of the bundle, which is necessary for its supply to the 3D printer during the printing process.

The formed fiber (tow) 1 is rolled through rollers 2 to reduce the rigidity of the tow 1. Hot after drying, the fiber is rolled through rollers 2 at an angle of 90° to create additional pressure. In this way, the bundle after leaving the oven with the help of rollers is given additional softness.

At the same time, the claimed technical result is achieved - improving the manufacturability of 3D printing of a composite product by layer-by-layer deposition, reducing the porosity of the finished composite product.

Thus, the technical problem, which consists in creating a technological method for producing a semi-rigid tow based on carbon fiber and super-structural plastics in one stage of impregnation for 3D printing by layer-by-layer fusing, is solved by using a method for obtaining a semi-rigid tow based on carbon fiber and super-structural plastics in one stage impregnation for 3D printing by layer-by-layer deposition, characterized in that the carbon fiber is placed in an impregnation bath for impregnation with a solution of a polymer binder, then molded at temperatures of 240 ° C - 450 ° C during drying from the solvent using metal dies of a given diameter, installed directly in a drying oven, after which the hot fiber leaving the oven is passed through three guide rollers to reduce the rigidity of the tow, after which the tow is wound on a spool. The hot fiber is passed through three guide rollers, each time changing direction by 90°, to create additional pressure.

To implement the invention, the following technological units are required: a furnace 3 for burning the factory sizing, guide rollers, an impregnating unit, squeeze rollers, a drying oven with installed forming dies and rolling rollers, as well as a fiber pulling and winding mechanism.

The furnace for burning the factory sizing is a pipe made of heat-resistant glass or any material suitable for operation at specified temperatures. The furnace used must have a heating system that allows maintaining the set temperature with an accuracy of 20 ° C along the entire length of the furnace. The length of the furnace is selected based on the speed of drawing the fiber, however, it cannot be less than 50 cm. In most cases, an oven temperature of 400 ° C is sufficient to remove the standard sizing, however, if there is a heat-resistant sizing on the fiber surface, the oven temperature can be increased, however, it should not exceed 800°C.

The guide rollers are installed before and after the impregnation bath in such a way that the pulled fiber does not touch the units of the installation: the walls of the furnaces and the impregnation bath. The rollers must be made of a material that does not react with the sizing composition and/or its components (PTFE or stainless steel) and have a flat, defect-free surface to avoid damage to the pulled fiber.

The impregnating unit is a bath made of a chemically resistant material (such as ceramic or glass) into which the impregnating solution is poured. An impregnating roller made of a chemically inert material (PTFE) is immersed in the bath so that the fiber passed along the lower surface of the roller is immersed in the impregnating solution. The diameter of the impregnation roller is chosen so that the treated fiber is immersed in the impregnation solution for at least 10 cm, but should not be less than 15 cm. Additionally, the impregnation roller can be rotated by a motor.

The squeezing rollers 2 must be made of a material that does not react with the sizing composition and/or its components (PTFE or stainless steel). The wringer rollers can be rotated by a motor.

The drying kiln 3 must be made of a heat-resistant material and equipped with a staged heating system that allows different temperatures to be created along the length of the kiln. The drying oven must have at least two controlled heating zones. The temperature of the first heating zone is selected based on the solvent used in the sizing composition, but cannot be less than 240°C. The heating temperature of the first zone must exceed the boiling point of the solvent used in the sizing composition by at least 50°C. The temperature of the second zone is selected based on the properties of the used sizing agent. The temperature of the second zone should correspond to or exceed the temperature of physical (eg, melting) or chemical (eg, crosslinking) transformation of the sizing agent, but does not exceed 450°C.

Drying oven 3 must be installed strictly perpendicular to the floor surface. Thus, the pulled fiber also turns out to be perpendicular to the floor surface, as a result of which the flow of the uncured solution under the action of gravity occurs evenly and a gradient in the thickness of the polymer layer is not formed, as if the fiber was dried horizontally or at an angle.

Forming dies must be made of a material with good thermal conductivity, which ensures uniform heating of the die and thermal stability, allowing their operation in the range of 240°C - 450°C. Forming dies must have a diameter that meets the requirements of the equipment used for the manufacture of products with the resulting tow, but not less than 20% of the linear width of the original carbon fiber. The forming dies must have a smooth surface to avoid damage to the drawn fiber. Forming dies are installed in the heated zones of the drying oven.

The rolling rollers 2 must be made of a thermally resistant, chemically inert material. The rolling rollers must be positioned in relation to each other and in relation to the neighboring units of the installation in such a way that, passing through them, the fiber changes direction by 90°, as shown in the figure. The optimal number of rollers is 3 pcs. but you can use a system with a large number. The diameter of the rolling rollers can be chosen arbitrarily.

The invention is illustrated by the following examples.

Example 1 A 5% solution of commercially available polyesterrimide in chloroform is placed in an impregnation bath. UMT42S-3K-EP carbon fiber manufactured by Yumatex is pulled through an oven heated to 400°C to burn the factory sizing, then it is passed through an impregnation bath with a polyesterimide solution, after which the fiber enters a drying oven heated to 300°C. The hot fiber leaving the furnace passes through three guide rollers, each time changing direction by 90°, after which it is wound onto a spool. The fiber pulling speed is 10 m/h. The finished semi-rigid tow is used for printing products in combination with a polyesterimide or polyamide binder. The porosity of the finished composite product, determined according to ASTM D3171-15, does not exceed 0.3%.

Example 2 A semi-rigid tow is prepared in the same manner as described in Example 1, however, a 20% solution of polyphenylene sulfide oligomers in α-chloronaphthalene is used for impregnation. The temperature of the drying oven is 300°C. The finished semi-rigid tow is used for printing products in combination with poly(ephenylene sulfide) or polyetheretherketone. The porosity of the finished composite product, determined according to ASTM D3171-15, does not exceed 0.4%.

Claims (1)

A method for producing a semi-rigid tow based on carbon fiber and superstructural plastics in one stage of impregnation for 3D printing by layer-by-layer fusing, characterized in that the carbon fiber is placed in an impregnation bath for impregnation with a solution of a polymer binder, then molded at temperatures of 240-450 ° C in the process drying from the solvent using metal dies with a diameter of at least 20% of the linear width of the original carbon fiber, installed directly in the drying oven, after which the hot fiber leaving the oven is passed through at least three guide rollers, while after each guide roller the direction of the hot the fibers are changed by 90 °, after which the resulting bundle is wound on a coil.

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