DE102014208240A1 - METHOD FOR PRODUCING POLYMER COMPONENTS - Google Patents

Abstract

The invention relates to a method for the production of polymer components in which particles of a material deviating from the component material are embedded in the component material. For this purpose, particles are applied to a surface in the interior of a molding tool or mold part. Subsequently, the component material is introduced or filled in plastically deformable consistency in the mold, wherein the component material penetrates into pores or spaces between the particles applied to a surface particles. After curing, the component with the embedded particles in the near-surface areas is removed from the mold.

Description

The invention relates to a method for the production of polymer components, in which particles of a material deviating from the component material are embedded in the component material. The particles are embedded exclusively in a near-surface region in the component material.

Molded components produced in plastics processing are used in a wide variety of applications. The range of plastics used is correspondingly broad, as well as the number of materials and processes for functionalizing the components or component surfaces according to the purpose. This is necessary because the material or the plastic does not always meet the desired requirements. Depending on the application, the modification can take place by means of coating or production of a composite material / material by additives or fillers. When manufacturing a composite material / material usually the mechanical and optical properties of the component are changed, which is not always desirable. In addition, the required material / material cost of the filler is quite high. Fillers, which can also be particles, are present distributed over the entire component volume.

It is also known to provide components with a coating on the surface. During coating, high demands are placed on the component (topography, orientation, chemical structure, low proportion of lubricant, coating temperature resistance, etc.), which severely limits the possible combinations of different component materials / materials and coating materials / materials.

In this case, one or more thin layers are applied with different functions. There are application processes from the liquid phase (painting, electroplating, etc.) or from the gas phase (vapor deposition, sputtering, etc.). However, the possible combinations are generally limited, since the necessary temperatures for the coating (coating temperature or temperatures for drying) on the molding material with regard to (temperature resistance, or dimensional stability) must be coordinated. When coating from the liquid phase, the wetting, solvent compatibility and the drying behavior of the layers are always critical parameters. During evaporation (vacuum process), the outgassing of certain polymers during evacuation of the vacuum chamber is a great challenge. In addition, the conformal, homogeneous and shadow-free deposition on three-dimensional substrates often represents a major hurdle.

Coatings have an interface between the layer and the surface of a component where properties change very much. In addition, the layer adhesion to the base component is to be viewed critically.

In the fabrication of composite material / material components, the addition of fillers during fabrication or processing into the matrix material / material from which components are made. With fillers desired properties can be adjusted. These properties may relate to the manufacturing process (additives, such as lubricants or anti-blocking agents) or to subsequent use (colorants, antistatic agents, antioxidants, sunscreens). In the production of a composite material / material component, the high material requirement and the change in the electrical, optical, thermal and mechanical properties of the matrix material / material are disadvantageous. Composite materials / materials differ significantly in terms of processability from the unfilled raw materials.

It is therefore an object of the invention to provide possibilities for the production of molded components, which have exclusively on the surface and in the near-surface area particles of a material deviating from the component material and otherwise the properties of the component are determined by the component material.

According to the invention, this object is achieved by a method having the features of claim 1. Advantageous embodiments and further developments of the invention can be realized with features described in the subordinate claims.

In the method according to the invention particles are applied to a surface in the interior of a mold or mold part. Subsequently, the component material is introduced or filled in plastically deformable consistency in the mold, wherein the component material penetrates into pores or spaces between the particles applied to a surface particles. After curing, the component with the embedded particles in the near-surface areas is removed from the mold.

As a component material, a plastically deformable polymer or a polymer melt can be used. The particles used may be metallic, ceramic or organic particles which are solid at the processing temperature or which are not or only partially soluble in the component material. Organic particles can, for example, a have higher softening temperature than the component material.

The particles can be applied in a suspension to a surface of the mold or mold part, which can be achieved by spraying, dipping, spin-coating, printing and brushing.

Direct application of particles to a surface of the mold or mold part is also possible. This can z. B. be realized by a CVD method. Particles formed by means of flame spray pyrolysis can likewise be applied to a surface of the mold or mold part immediately after their formation.

The component material can be advantageously introduced with increased pressure in the mold. However, pressure forces can also be exerted on the component material accommodated in the molding tool. In the latter case, compressive forces can be exerted on the mold material still plastically deformable component material pressure with a plunger, hydraulically or pneumatically by increased liquid or gas pressure.

The particles should be embedded in the component material with a maximum depth of 0.1 mm, starting from the surface of the component. An exclusively near-surface embedding of the particles in the polymer material is to be striven for. It can particles with a maximum diameter of 0.01 mm, preferably not more than 0.0001 mm are used.

In many applications, it may be advantageous not to provide the entire surface of a component, but only certain selected surface areas with particles. Thus, particles can be applied only to predetermined areas of the inner wall of a mold or mold part. This can be achieved by using at least one template or mask, with which a shading of non-coated surface areas in the direct application of the particles or by means of stencil during the order, is possible. For this purpose, electrostatic forces can be used if only a suitable electrical charge is applied to certain surface areas of a mold or mold part, which then adhere particles with correspondingly opposite electrical charge. A structured application can also be done by appropriately trained nozzle shapes, similar to the ink jet printing, for example, using fine FSP or CVD nozzles. It can also be applied in a similar manner as in the airbrush techniques known per se, in particular suspensions in which particles are contained. The particles can also be prepared by known thermokinetic coating methods, for. As thermal spraying, suspension spraying, etc., are applied.

In principle, of course, it is possible to use the electrostatic bonding of particles on the entire surface of a molding tool or several mold parts in order to modify the entire component surface with particles after the transfer.

The method according to the invention makes it possible to produce components in which particles are embedded and integrated in the component material exclusively in regions near the surface. In this case, various methods (prototypes, forming) can be used, in which the component material to be formed is introduced into a shaping tool and there the shape of the respective component is achieved. The material to be molded may be a softened plastically deformable polymer, a polymer whose surface is plastically deformable, a polymer melt, polymerizable precursors (monomers, etc.) or monomer or polymer solutions.

Since the refinement of the component surfaces can also be realized with a wide variety of particle materials and geometries, the production of a wide number of differently designed and configured components is possible. Spherical, platelet-shaped or wire-shaped particles can be used.

The process can be divided into three sub-steps. In this case, in a first step, a coating of a layer with particles takes place on an inner surface of a molding tool or molding tool part (eg an injection molding tool).

The order can be carried out with a suspension containing particles. Alternatively, the particles may be deposited directly or applied to the wall of a mold or mold part. This can be done, for example, by means of flame spray pyrolysis, CVD, or the like.

The particles should not form a complete dense and closed layer.

When using suspensions, the layer formed with particles can be formed by applying the suspension to a possibly heated surface of a molding tool. Additives possibly contained in the suspension (eg surfactants) should be removed after application, in particular washed out. The direct application of particles allows to dispense with this subsequent removal, washing step, since the respective particles from the gas phase of chemical compounds in which a chemical element is contained, can be obtained with the particle of this chemical element or a chemical compound of this chemical element, directly can be deposited on a surface of a mold. This eliminates the expense of producing a suspension containing particles and possibly the washout step

In a second step, a close-to-surface integration of the particles takes place through layer transfer. This can be achieved by means of prediction (eg injection molding, casting from melt). In this case, the mold coated with particles on a surface is brought into contact with a melt of a thermoplastically processable polymer and cooled or energized to obtain the dimensional stability.

However, it can also be achieved by means of forming (for example pressing). The coated on a surface mold is pressed against a, above the Vicat softening temperature, heated molding. The Vicat softening temperature is lowered DIN EN ISO 306 determined at a heating rate of 120 K / h. By changing the dimensional stability, the flowability increases and thus an integration of the particles in the component surface is possible. After falling below the Vicat softening temperature, the component or its surface again becomes dimensionally stable and the particles migrated into the component material are firmly integrated in the polymer surface.

The preparation can also be carried out with a solution of a polymer. To a particle-coated surface of a mold to a polymer solution is poured and by removing the solvent, the polymer is cured. After curing, the component can be removed from the mold.

In the manufacture of components with a monomer, the coated mold can be used as a wall of a polymerization chamber into which a polymerizable, liquid mixture of monomer and initiator is filled. The curing can be carried out by thermal or radiation-initiated polymerization.

In all three cases, the plastically deformable component material can penetrate into the "open" network of the layer formed with particles on a mold surface and enclose the particles.

In a third step, the component is separated from the mold. In this case, the cured component is released from the mold, wherein particles remain embedded in the surface of the component in the component material. Mold tool parts can be moved away during demolding and separated.

A finished manufactured component has a core which is formed exclusively or substantially solely from the actual component material. Only in a near-surface region are the particles contained in a matrix consisting of the component material. In this case, the properties of the component change only in this particle-containing near-surface region of the component, without forming a sharp interface at which the mechanical, electrical, thermal and optical properties change abruptly. There is only a graded transition, which is influenced by the concentration of particles per volume in the component material. For example, no sudden change in the optical refractive index from the surface into the interior of the component occurs, as would be the case with a coating permanently applied to a component surface.

It is also possible to obtain components which are electrically conductive only on the surface in at least one region and the remainder of the component has no electrical conductivity.

With particles in optically transparent components, the color impression can be influenced.

In general, the properties remain inside a component of the component material produced according to the invention.

In contrast to a material composite based method in which particles occur in the entire component volume, there is the advantage that in this way a lower demand of the corresponding particles is required. At the same time, the mechanical properties of the component material used are only marginally influenced, if at all.

In contrast to coatings in which realizable coating parameters, such as temperature, solvent used u. a. depend very much on the material of the component, a versatile combination of different particles (materials and geometries) and polymeric component materials is possible with the method according to the invention.

By integrating the particles in the component surface can also negative Properties such as low abrasion resistance, brittleness or additional sharp interfaces are avoided.

In special cases, it is possible to produce optically transparent components. This can be achieved by using optically transparent matrix materials from which a component is to be produced, and materials of particles which do not absorb electromagnetic radiation in the visible spectral range or show only small light scattering effects due to their small size (<100 nm).

Another possibility is a transfer of structured deposited or applied particles (eg by using masks or templates). This allows the production of components that have spatially resolved structured surface modifications / refinements.

With the method according to the invention, the production of transparent and non-transparent components made of polymers with shaping manufacturing processes is possible. It can be manufactured components that have optically transparent, heated surfaces, surfaces with special optical properties (absorption, reflection, Lichtein-, Lichtauskopplung). It is also a surface functionalization for printing and gluing tasks (hydrophilic plastic surfaces) possible. Components produced according to the invention can also be used in medical technology (biocompatible surfaces or antimicrobial surfaces). An antimicrobial or antibacterial effect may be achieved with suitable metal particles embedded in the near-surface region, e.g. B. silver particles can be achieved.

Unrecognizable security features in the surfaces of components can also be formed without auxiliary means.

Nanoparticles with diameters of less than 100 nm, particularly preferably less than 50 nm, are preferably used for the production of optically transparent components and embedded in layer thicknesses of less than 0.001 mm, preferably less than 0.0005 mm, in a region near the surface. Particularly suitable transparent polymers are PMMA, PET, PC, PS, polymers from the group of polyesters, polyolefins, polyurethanes, polyimides, polyamides, polyacrylates and PMA, as well as copolymers or combinations thereof. For applications that require optically transparent surfaces / components that are also impermeable to UV radiation, nanoparticles of zinc oxide or titanium dioxide can be used. As a result, both the polymer itself and objects behind the polymer component can be protected from UV radiation. IR-absorbing particles for use in components according to the invention can be formed from doped tin dioxide, zinc oxide or indium oxide and z. B. are used for the targeted heating of the component surface by IR radiation.

Porous silicon dioxide particles, in particular nanoscale hollow spheres of SiO ₂ , or magnesium fluoride particles can be used, for example, in order to reduce the optical refractive index of the component surface. Thus, the reflection can be specifically reduced and the transmittance of the components can be increased. By particles of z. As zinc sulfide, zinc oxide, titanium dioxide, lead sulfide, the optical refractive index of the surface and thus the radiation reflection can be increased specifically. With luminescent nanoparticles (eg rare earth-doped substances such as europium-doped yttrium vanadate or doped semiconductors, such as manganese-doped zinc sulfide), optically transparent components can be generated which emit visible light under UV irradiation. For example, security features for product protection can be integrated.

By hydrophilic particles, such as. As silica or titanium dioxide, the surface energy of the polymer components can be specifically reduced. As a result, for example, the printability or adhesiveness of the components can be improved. Hydrophobic particles (eg, based on silica with functionalization by perfluorosilanes), the surface energy can be increased just as drastically to z. B. to produce a dust and water repellent surface. With particles based on z. As titanium dioxide or hydroxyapatite, the biocompatibility of the component surface can also be increased.

Metal or metal salt particles based on Ag, Cu or zinc can be used for antimicrobial component surfaces.

For the direct deposition of these particulate materials z. For example, flame spray pyrolysis (FSP) can be used as described by Pratsinis ( Journal of Material Chemistry, 2007, 17, 4743-4756 ). In this case, a combustible solvent / mixture (eg consisting of alcohols, acetonitrile, acetic acid, ...), in which a compound of the substance to be deposited (eg metal salts such as acetates, ethylhexanoates, nitrates, ...) dissolved or suspended / dispersed, conveyed through an FSP nozzle and atomized with drops of dosed oxygen and sprayed into a flame. In the flame, the solvent burns, so that the dissolved or suspended / dispersed material decomposes and aggregates into particles that deposit on thermally stable substrates above the nozzle. Of these substrates, the particle integration in the Polymer be carried out in the manner described. Besides metal oxide particles, metal particles can also be obtained by using noble metal compounds. Also, particle suspensions / dispersions and mixtures of suspended / dispersed particles and solutes may be used simultaneously to produce composite / hybrid materials.

The invention will be explained in more detail by way of examples.

Showing:

1 a diagram with transmission spectra on components, in whose near-surface regions different proportions of ITO particles are integrated

example 1

For the production of optically transparent components with absorbing effect for electromagnetic radiation from the wavelength range of the infrared light can proceed as follows:
A suspension is prepared with particles of indium tin oxide (ITO) and isopropanol. The suspension should contain 30% by weight of particles having a maximum mean particle size of 100 nm.

The suspension thus obtained is sprayed with an ultrasonic nozzle at a frequency of 120 kHz at a flow rate of ~ 0.5 ml / min on a surface of a mold part of an injection mold on a surface 100 mm × 150 mm and then dried so that only the ITO Particles adhere to the inner wall of the pre-coated surface of the mold part and the isopropanol has been evaporated. For this purpose, the mold part or the entire injection mold can be heated.

In the closed injection molding tool polyethylene (PE) is introduced with customary in plastic injection molding process parameters in the mold until it is completely filled with the polyethylene.

Since the ITO particles do not form a completely closed layer on the correspondingly coated surface of the mold part, the polyethylene can penetrate into interstices between the particles. As a result, in addition to a cohesive connection between the particles and the polyethylene, as a component material, a positive connection can be achieved and ITO particles can be embedded in the polymer matrix of polyethylene.

With the in 1 shown transmission spectra of components in the near-surface regions of different proportions of ITO particles are integrated, it becomes clear how the absorption of electromagnetic radiation with wavelengths above 1000 nm can be influenced and the transmission at wavelengths less than 1000 nm significantly less affected and only one small proportion of this radiation is absorbed or reflected. The upper curve shown represents a component made solely of polyethylene without particles.

The different mass fractions of particles per surface can be injected by different pressures and / or temperatures with which polymer in the injection mold and / or by the thickness and / or the number of applied to a surface of the mold part particles are influenced. Thus, the particle content can be increased at higher pressures and temperatures and greater layer thickness.

As a result of the ITO particles embedded in the near-surface region, the polymer, which is actually dielectric, may be electrically conductive in this surface region of the component and have an electrical sheet resistance of 3.7 × 10 ³ ohms, with a particle loading of 80 g / m ² .

Example 2

For the production of components having an antibacterial effect, silver nanowires, as a possible form of particles which can be used in the invention, having a mean diameter of 60 nm and a proportion of 0.5% by mass in isopropanol are processed into a suspension. The suspension is sprayed with an ultrasonic spray head at a frequency of 120 kHz and a flow rate of 0.5 ml / min on a 100 mm × 150 mm surface of an injection mold.

After heating, the isopropanol was evaporated and it was then injected into the now closed injection mold polyethylene adhering to usual in plastic injection molding parameters. In this case, the plastically deformable polyethylene penetrates as a component material in pores / spaces between the silver nanowires, so that after cooling and curing of the polyethylene, the silver nanowires are embedded in the near-surface region of the molded finished component after demoulding.

Example 3

For the preparation of zinc oxide particle layers, a 0.5 M zinc acrylate solution (2 ml / mm) in a methanol: acetic acid mixture (94: 6 Vol .-%), which is sprayed with oxygen (3.85 slm) in a TETHIS Npn nozzle. ZnO particles form in the 50 mm long flame and can be deposited 200 mm above the nozzle at 250 ° C on glass or steel substrates (approximately 75 × 25 × 1 mm ³ ). After deposition for 10 minutes, an approximately 200 nm thick layer is obtained, which can be integrated into polymer by the process described.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited non-patent literature

• DIN EN ISO 306 [0024]
• Journal of Material Chemistry, 2007, 17, 4743-4756 [0044]

Claims (8)

Process for the production of polymer components, in which particles of a material deviating from the component material are embedded in the component material, in which Particles are applied to a surface in the interior of a molding tool or mold part and then the component material is introduced or filled in plastically deformable consistency in the mold, wherein the component material penetrates into pores or spaces between the particles applied to a surface particles and after curing, the component with the embedded particles in the near-surface areas is removed from the mold. A method according to claim 1, characterized in that a plastically deformable polymer or a polymer melt is used as the component material. A method according to claim 1, characterized in that metallic, ceramic or solid at the processing temperature or in the component material not or only partially soluble organic particles are used. Method according to one of the preceding claims, characterized in that the particles applied directly or in suspension on a surface of the mold or mold part, wherein in a direct application by a CVD method or by flame spray pyrolysis particles formed immediately after their formation on a Surface of the mold or mold part are applied. Method according to one of the preceding claims, characterized in that the component material is introduced with increased pressure in the mold or pressure forces are exerted on the component material received in the mold. Method according to one of the preceding claims, characterized in that particles having a maximum diameter of 0.01 mm, preferably not more than 0.0001 mm are used. Method according to one of the preceding claims, characterized in that particles are applied only to predetermined areas of the inner wall of a mold or mold part. Method according to the preceding claim, characterized in that, using at least one stencil or mask or electrostatic forces are applied.

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