DE102015119649B4 - Process for the production of a cavity element with a thermoplastic coating - Google Patents

Abstract

A method for producing a cavity element (1) with a thermoplastic coating (2), wherein the cavity element has a cavity continuous through the cavity element, the surface of the cavity element delimiting the cavity being coated with a thermoplastic, the method comprising the following steps: particles of a thermoplastic having a specific melting point into the cavity of the cavity member; and heating the surface of the cavity element defining the cavity to a temperature greater than or equal to the melting point of the thermoplastic, wherein the particles of the thermoplastic are present in a fluid suspended form when introduced into the cavity, and wherein the cavity element is a metal element.

Description

The present invention relates to a method according to claim 1 for producing a cavity element with a thermoplastic coating, the cavity element having a cavity which is continuous through the cavity element and whose delimiting surface is coated with a thermoplastic.

Capillaries made of stainless steel, glass (fused silica) or polyetheretherketone (PEEK) are usually used to connect the various components of an HPLC system (High Pressure Liquid Chromatography). For this, there are different requirements for such capillaries in HPLC devices. For example, capillaries made of titanium, MP35N ™ or PEEK are used for biocompatible HPLC systems, since such systems should be as free of iron as possible. Furthermore, there is a trend towards faster and more precise separations, which means that high pressures are required. Plastic capillaries made of PEEK can, for example, only be used at pressures of up to 500 bar. In the case of extremely high pressures, capillaries made of titanium or MP35N ™ are usually used. However, there are also limits to biocompatible HPLC systems here, as the low iron content also plays a greater role at high pressures, and because the capillaries on the inner wall - due to the manufacturing process - are not completely free of impurities, so that the HPLC system System can become dirty. This is why so-called PEEK-in-steel capillaries were used in the past. For example, a pressure-resistant metal tube is pushed over the plastic tube for stabilization. There must be no air gap between the inner and outer pipes, as otherwise the inner pipe could burst at this point. Since it is known that no drawn tubes have a perfectly smooth inner surface, this is probably the greatest problem in the prior art. Another problem is the precise coordination of the inner and outer tubes with regard to the adaptation of the diameter. The inner tube must not be too small, since the outer tube inner diameter has to be hammered smaller or the inner tube is inflated and melted onto the outer tube. This results in a specific ratio of tube inside diameter to tube outside diameter for each capillary size, so that different tube variants are necessary for different capillary thicknesses.

For example, the DE 100 17 606 A1 a process in which a metal pipe is reduced in diameter by means of hammering, thus mechanically enclosing the inner plastic tube. This method is relatively complex and can only partially solve the aforementioned problems.

WO 2012/021 596 A1 discloses a PEEK-in steel capillary made by sliding an extruded PEEK tubing into a stainless steel tube. Heat and pressure are used here so that the hose adheres to the inner surface of the pipe. Here, too, the process is to a certain extent complex and the stainless steel pipe and PEEK hose diameter must be varied for capillaries with different cavity diameters.

WO 2007/038 003 A1 also provides for the insertion of a PEEK hose into a stainless steel pipe, in which the connection between the hose and the pipe is created by heating the outer surface of the pipe and passing cooling air through the hose. Here, too, the disadvantages mentioned above cannot be overcome.

Furthermore, a method for producing metal-supported plastic capillaries is also known in which the pressure resistance of the capillary is increased by galvanic growth of a metal layer on the liquid-carrying plastic pipe. However, this method is costly and complex.

The DE 24 24 706 B2 relates to a method for coating the inner surface of metal pipes with a small diameter, in which a stream of a powdery synthetic resin diluted with air or an inert gas is passed through the metal pipe and melted onto its inner surface.

The DE 22 05 739 A1 relates to a process for the production of a metal pipe coated with thermoplastic on the inside, in which the plastic is applied to the inner wall of the metal pipe continuously produced on a jacket press by means of a spray device passed coaxially through the press tool at a point located behind the press exit and using the pressure resulting from the press process increased temperature of the pipe wall is sintered onto this.

The DE 20 52 314 B2 relates to a method for coating the inner surface of metal pipes with plastics by bringing the inner wall of the pipe into contact with plastic powder, a flow of air loaded with powder and then an air flow being blown through the horizontally stored pipe alone, and an induction coil being drawn over the pipe and during During this time an air stream laden with powder is circulated through the stationary pipe.

The DE 10 2011 050 037 B3 relates to a connector unit for connecting capillaries for high-performance liquid chromatography. The EP 0 037 024 A1 relates to a method for producing a tube made of cellulose hydrate, the inside of which is wetted with an aqueous dispersion of a thermoplastic and melted onto the inner surface.

The U.S. 3,693,588 A relates to a device for coating the inner surface of a tube made of cellulose with a plastic material.

Another problem in the prior art is that small bores above a certain length are difficult or even impossible to produce. The rule here is that the drilling length can be a maximum of 10 to 20 times greater than the diameter of the drill. It would therefore also be desirable to provide a method in which small bores with a large length can be produced.

It was therefore the object of the present invention to produce capillary tubes using the simplest and most economical manufacturing method possible, which are stable even at pressures above 500 bar, have biocompatibility (freedom from metal or iron), the inner surface of which has no residual contamination, for example oil or crumbs and whose inner surface is as smooth as possible. Furthermore, it is also an object of the present invention to be able to provide capillaries with a different inside diameter in the simplest possible manner without having to vary the diameter of the metal tubes used. Yet another object of the present invention is to provide a method with which the problem of the drilling length in the case of small bores can also be circumvented, so that longer tubular cavities with a small diameter can also be realized.

• - Einbringen von Partikeln eines Thermoplasts mit einem spezifischen Schmelzpunkt in den Hohlraum des Elements; und
• - Erwärmen der den Hohlraum begrenzenden Oberfläche des Elements auf eine Temperatur von gleich oder oberhalb des Schmelzpunkts des Thermoplasts,

worin die Partikel des Thermoplasts beim Einbringen in den Hohlraum in in einem Fluid suspendierter Form vorliegen, und worin das Hohlraumelement ein Metallelement ist.To achieve the above-mentioned objects, a method for producing a cavity element (hereinafter also simply called "element") with a thermoplastic coating is provided, the element having a cavity continuous through the element and the surface of the element delimiting the cavity having a Thermoplastics coated, the method comprising the following steps:

• - Introducing particles of a thermoplastic with a specific melting point into the cavity of the element; and
• - heating the surface of the element delimiting the cavity to a temperature equal to or above the melting point of the thermoplastic,

wherein the particles of the thermoplastic are in a form suspended in a fluid when introduced into the cavity, and wherein the cavity element is a metal element.

The term "cavity continuous through the element" means a cavity in the element which has two openings which are connected to one another via the cavity, i. it is a cavity opened on two sides of the cavity element. The cross-sectional area of the cavity can assume any conceivable shape, such as, for example, circular, elliptical, polygonal, such as, for example, triangular, square, pentagonal or hexagonal. Over the course of the passage from one opening to the other opening, the cross-sectional area can also have different shapes, i. vary.

The expression “surface delimiting the cavity” is understood to mean the surface of the cavity element which is defined by the lateral surface of the cavity.

The cavity element can be made of any metal that is temperature resistant up to above the melting temperature of the thermoplastic used and also has such a high pressure resistance that it can withstand pressures of up to 2000 bar and more in the form of thin-walled capillaries. The cavity element is thus a metal element, particularly preferably a steel element or stainless steel element.

The thermoplastic in the present invention is preferably a polyether ketone, more preferably a polyaryletherketone such as polyetheretherketone (PEEK), poly (etherketoneketone) (PEKK), poly (etheretheretherketone) (PEEEK), poly (etheretherketoneketone) (PEEKK) and poly (etherketone) ether ketone ketone) (PEKEKK). The thermoplastic can also be a polyimide, polyamide-imide or a polyketone. However, polyetheretherketone is most preferred. The thermoplastic should have a melting point of greater than 180 ° C., a melting point of greater than 200 ° C. being more preferred, a melting point of greater than 250 ° C. even more preferred, and a melting point of greater than 300 ° C. being most preferred.

Accordingly, the temperature when heating the jacket surface of the element delimiting the cavity is at least 180 ° C., more preferably greater than 200 ° C., even more preferably greater than 250 ° C. and most preferably greater than 300 ° C. The temperature when the jacket surface of the element delimiting the cavity is heated is preferably limited at the top due to the decomposition temperature of the thermoplastics used and is preferably at 500 ° C maximum, more preferably 450 ° C and most preferably 400 ° C.

The thermoplastic particles used in the process according to the invention preferably have an average diameter in the range from 1 μm to 100 μm, more preferably from 5 μm to 50 μm and most preferably from 5 μm to 20 μm. According to the invention, the average diameter is preferably determined by laser diffraction, for example with a Mastersizer from Malvern.

The step of introducing the particles of the thermoplastic into the cavity of the cavity element can take place before or after the heating of the jacket surface of the cavity element delimiting the cavity. In a variant of the method according to the invention, however, it is preferred that the particles of the thermoplastic are introduced into the cavity before heating. This has the advantage that the particles are evenly distributed in the cavity before the heating.

The particles of the thermoplastic are suspended in a fluid when they are introduced into the cavity. The use of a suspension of the particles of the thermoplastic has the advantage that the particles are more evenly distributed in the cavity prior to the thermal coating and, in a simpler manner, a uniform coating the surface of the cavity element can take place in the cavity than is the case with powders subject to gravity.

Any conceivable solvent that does not damage the thermoplastic at the process temperatures can be used as the fluid for the suspension mentioned, for example water, alcohol, such as ethanol, propanol or butanol, and isopropanol. Mixtures of different solvents or the solvents mentioned can also be used.

The average diameter of the cross-sectional area of the cavity (before coating) is preferably in the range of 0.1 mm to 2.0 mm, more preferably 0.1 mm to 1.0 mm, and most preferably in the range of 0.3 mm to 0.5 mm.

The particles can be presented statically in the cavity in a form suspended in a fluid, but they can also be passed continuously through the cavity. The suspension is pumped continuously through the cavity, for example. The flow rate during pumping through is preferably in the range from 0.01 to 0.5 m / s. During the passage of the particles suspended in a fluid through the continuous cavity, heating is preferably carried out at the same time, so that the particles are deposited on the surface of the cavity element by melting and the thermoplastic coating is formed.

The proportion by weight of particles of the thermoplastic is preferably in the range from 5 to 20% by weight, based on the total weight of the suspension.

The method according to the invention has the advantage that the thickness of the thermoplastic layer in the cavity element can be adjusted by several factors: by the concentration or the amount of substance of particles in suspended form in the total suspension, by the duration and the maximum temperature of the heating of the cavity delimiting the cavity Surface of the element, as well as by the flow velocity when passing through the particles in the form of a suspension.

The outer dimensions of the cavity element or its shape is in no way limited. The cavity element can have the shape of a tube or a capillary. However, it can also have any shape deviating therefrom, the cavity having been produced, for example, by a bore, as is used, for example, in HPLC valves.

In one embodiment of the method according to the invention, however, the cavity element is preferably in the form of a tube or a capillary. In a further embodiment of the method according to the invention, the heating of the tube or the capillary can preferably take place in a locally limited manner at at least one point, namely in such a way that the entire circumference, partial circumference or punctual heating is carried out with regard to the circumference of the tube or the capillary, however, only a limited area is heated in relation to the direction of extension of the tube or the capillary. In other words, the capillary or the tube is heated in a ring at a certain point. In this way, for example, the coating with the thermoplastic can only be carried out at the heated point, so that a cross-sectional constriction occurs at this point.

The heating of the tube or the capillary can also take place in a locally limited manner at several points and in such a way that, as in the aforementioned manner, heating is carried out several times in a locally limited manner, with the points at which local heating is in each case the same distance or also may have irregular distances from one another. In this way, cross-sectional constrictions are found in the interior of the capillary or the tube at periodic intervals, so that For example, when the sample is transported through the capillary, for example of an HPLC system, no paraboloid can form, which leads to mixing / dilution of the sample and thus to poorer analysis.

As an alternative to the static local heating mentioned above, the local heating can also take place dynamically, i.e. Although the heating takes place locally limited at one point, this point is varied along the extension direction of the tube or the capillary. It is preferably varied in such a way that a heat source is moved at a uniform speed along the extension direction of the tube or the capillary. The thickness of the coating within the capillary or the tube can also be influenced by the speed of this movement, for example. The particles can be present statically within the cavity in the form of a suspension, but they can also be passed through the cavity at a certain flow rate. The direction of movement of the heat source can be the same as the direction in which the particles pass through, but it can also be opposite to this.

The cavity element produced according to the invention is preferably in the form of a tube or a capillary, in particular it is a separation column for HPLC, or is used for it. The cavity element can, however, also be a block-shaped cavity element, such as, for example, a capillary socket on a switching valve or a separation column for HPLC.

The cavity element produced according to the invention can be periodically uniform or also irregular along the extension direction of the cavity. The cavity element produced according to the invention can be used as a separation column in an HPLC system or in a switching valve in an HPLC system.

The present invention will now be described in more detail with reference to figures or examples, these not being to be regarded as restrictive and all properties in the figures, which are in principle independent of one another, can also be applied to all embodiments independently of one another.

• 1 zeigt ein erfindungsgemäßes Hohlraumelement in Form einer Kapillare;
• 2 zeigt einen Längsschnitt eines erfindungsgemäßen Hohlraumelements in Form einer Kapillare;
• 3 zeigt ein erfindungsgemäßes Hohlraumelement in Form einer HPLC-Kapillarbuchse, wie z.B. an einem Schaltventil oder einer Trennsäule;
• 4 zeigt eine vergrößerte Ansicht des beschichteten Hohlraums des Hohlraumelements nach 3;
• 5 zeigt ein erfindungsgemäßes Hohlraumelement (halboffen) in Form einer Kapillare mit einem sich periodisch ändernden Innendurchmesser;
• 6 zeigt ein erfindungsgemäßes Hohlraumelement (geschlossen) in Form einer Kapillare mit einem sich periodisch ändernden Innendurchmesser;
• 7 zeigt ein erfindungsgemäßes Hohlraumelement (Längsschnitt) in Form einer Kapillare mit einem sich periodisch ändernden Innendurchmesser.

Illustrations:

• 1 shows a cavity element according to the invention in the form of a capillary;
• 2 shows a longitudinal section of a cavity element according to the invention in the form of a capillary;
• 3 shows a cavity element according to the invention in the form of an HPLC capillary socket, such as, for example, on a switching valve or a separation column;
• 4th Figure 12 shows an enlarged view of the coated cavity of the cavity member of FIG 3 ;
• 5 shows a cavity element according to the invention (half-open) in the form of a capillary with a periodically changing inner diameter;
• 6th shows a cavity element according to the invention (closed) in the form of a capillary with a periodically changing inner diameter;
• 7th shows a cavity element according to the invention (longitudinal section) in the form of a capillary with a periodically changing inner diameter.

1 (oblique view) and 2 (Longitudinal section) show a cavity element according to the invention 1 with a thermoplastic coating 2 in the form of a capillary. The cavity element 1 is preferably made of steel to ensure high pressure stability. Like in particular from 2 is the surface of the cavity of the cavity member 1 with a thermoplastic coating 2 provided, which narrows the cavity by its thickness, so that a desired inner diameter 3 results.

3 and 4th shows a cavity element according to the invention 1 in the form of a capillary that has a thin bore 4th has, the inner surface of which has a thermoplastic coating 2 is provided to the inside diameter 3 to be able to further restrict beyond the minimum drilling size.

5 to 7th show a cavity element according to the invention 1 shown in half-open ( 5 ), in closed (transparent) ( 6th ) and in open (longitudinally cut) form ( 7th ). As in 1 and 2 is the cavity element 1 a capillary whose cavity surface is covered with a thermoplastic coating 2 is provided. The coating 2 has a changing inside diameter 5 with a thinnest point 5 and one thickest point 6th on.

Embodiment:

A pressure-stable metal tube with an inside diameter of 0.5 mm is heated to 400 ° C. from its outside. Then a suspension of a PEEK powder (VICOTE ^® COATINGS 700 SERIES, 10 µm grain size) and water in a weight ratio of 20 g PEEK powder to 100 g water is pumped through the pipe at a speed of 0.1 m / s. A part of the PEEK powder adheres to the inner wall of the pipe by melting and a coating is formed. The water evaporates and escapes from the pipe. The procedure is carried out for 10 minutes. Alternative to the VICOTE ^® COATINGS 700 SERIES can also do VICOTE ^® COATINGS 800 SERIES are used.

Claims (10)

A method for producing a cavity element (1) with a thermoplastic coating (2), wherein the cavity element has a cavity that is continuous through the cavity element, the surface of the cavity element delimiting the cavity being coated with a thermoplastic, the method comprising the following steps: Introduction of particles of a thermoplastic with a specific melting point into the cavity of the cavity element; and Heating the surface of the cavity element delimiting the cavity to a temperature greater than or equal to the melting point of the thermoplastic, wherein the particles of the thermoplastic are present in a fluid-suspended form when introduced into the cavity, and wherein the cavity element is a metal element. Procedure according to Claim 1 wherein the thermoplastic is a polyether ketone. Procedure according to Claim 1 or 2 wherein the particles have an average diameter in the range of 5 µm to 50 µm. Method according to one of the preceding claims, wherein the introduction of the particles takes place during or before the heating. A method according to any one of the preceding claims, wherein the particles are passed through the continuous cavity. A method according to any preceding claim, wherein the cavity element is in the form of a tube or a capillary. Procedure according to Claim 6 , in which the heating of the tube or the capillary takes place locally limited at at least one point, namely in such a way that with regard to the circumference the entire circumference, partial circumference or point, but with regard to the direction of extension of the tube or the capillary is heated in a limited area . Procedure according to Claim 7 , wherein the heating of the tube or the capillary takes place locally limited at several points, the points preferably each being the same distance from one another. Procedure according to Claim 7 , wherein the heating takes place locally limited at one point, but the point is varied along the extension direction of the tube or the capillary. Procedure according to Claim 9 wherein the location is varied such that a heat source is moved at a uniform speed along the direction of extension of the tube or capillary.

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