FI108849B - Method and apparatus for coating a body rotating about an axis - Google Patents

Abstract

The coating of rotating members (1) with a reaction mixture forming polyurethane can be improved by using as the application nozzle a slot die (3) which is set at an angle alpha parallel to the axis of rotation of the member (1), and by the reaction rate of the reaction mixture and the relative movement being coordinated with the circumferential speed of the rotating member (1) in such a way that the successive windings overlap in an imbricated form and join one another seamlessly. <IMAGE>

Description

108849

Method and apparatus for coating a rotating body

The invention relates to a method and apparatus for coating a rotatable body around a shaft, wherein a relative movement in the direction of the axis of rotation occurs between the body and the nozzle ejecting the reactive mixture forming the polyurethane so that the coating is carried out by screw threads.

Coating rotary bodies by this method is well known, and the method can also be used to make hollow bodies, particularly tubes, by coating a removable core or mandrel.

15 There are problems with the conditions imposed by variables such as circumferential velocity and movement of the piece or nozzle. In particular, there is a risk of air entanglements and insufficient threading of individual threads. Therefore, in the manufacture of tubes for coating the core, an attempt has already been made to place the reactive mixture on the carrier tape and to wrap it around the core, thereby filling the gap between the turns with the reactive mixture (EP 0 523 509 A2). Of course, filling the gap requires a more complicated method and equipment. Furthermore, this method is not suitable for coating articles because the carrier tape cannot be dispensed with.

The task is to improve the method mentioned at the beginning so that flawless coatings can be economically produced.

The present invention relates to a method for coating an article rotating about an axis, wherein a relative movement in the direction of the axis of rotation occurs between the article and the nozzle ejecting the reactive mixture forming polyurethane, so that the coating 35 is carried out by helical, overlapping threads. The method of 2 108849 is characterized by the use of a wide slot nozzle disposed at an angle α in the direction of the axis of rotation, whereby the reaction speed and relative motion of the reactant mixture is adapted to the circumferential velocity of the rotating body such that successive threads overlap and interconnect a is fitted at an angle of the shoulder formed during the coating so that the nozzle opening is at a distance of 1 to 10 mm from the application site and the peripheral velocity is set at the largest diameter of the applied coating to less than the outlet velocity of the responsive mixture from the wide nozzle.

| The invention also relates to a device for coating a rotatable body with a polyurethane-responsive mixture as described above, comprising bearing and rotating actuation of the part, and a wide-slot nozzle, wherein either the wide-gap nozzle is provided with a drive actuator or | 20 operating in the direction of the rotation axis.

| The apparatus is characterized in that the wide-slot nozzle and: '·· the surface to be coated forms a sharp angle a in the direction opposite to the feed direction.

! The ratio of the length of the wide opening nozzle outlet to • · »· 25 width may be 10 to 300, preferably 100 to 250.

The new method is particularly suited to • coating rolls with polyurethane elastomers, such as steel, transfer and transportation, and paper. . industry is done. In addition, it can be used for ] · 30 exterior coated tubes for industrial and off-sho • • re applications and internally coated tubes for hydraulic transfer of granular goods; If necessary, the surfaces to be coated must first be fitted with an adhesive.

I * .. *! * 35 3 108849

The new method can also be used to make tubes or other hollow bodies by coating a removable core. In this case, the release agent must be applied to the core or wrapped within the separation film.

Finally, a new method can be used to provide the pipes with a heat insulating polyurethane foam wrap. Compared to known methods, it is striking that the threads are not twisted side by side, but overlapping. Actually, in this method, there is a risk of il-10 inclusions and the risk of individual threads being unrelated is very close. More surprisingly, no air inclusions occur and the threads merge without forming a cladding or seam and form a sufficiently smooth surface of the coating. It has been shown that the new method is not only suitable for the inner and outer coating of rotationally symmetrical pieces, but also for pieces of diameter! varies in length and / or cross direction. It is a good idea to use this method in program control. With irregularly shaped bodies, it is necessary to always guide the algal nozzle to the same distance and the same slope; * ·· relative to the surface to be coated. Of course, the width of the nozzle limits the uneven shape of the pieces. By changing angle a, it is also possible to make the desired ones · '· *; 25 different thicknesses of coatings.

.:. A significant variable in the process is the outlet viscosity of the reacting mixture from the wide-gap nozzle. It is often necessary to achieve the desired coating thickness. , need to reshape the nozzle. Therefore, it may be necessary to * · '· 30 replace the nozzle with another nozzle or make ... "the nozzle slot adjustable in height and width, which may be extremely difficult as the nozzle interior.". should be matched accordingly.

It is particularly advantageous to use wide-mouth mouthpieces · ”35 thims to ensure that the alloy outlet rate of 4 108849 nozzle slots is the same throughout and that the outgoing mixture is equally old at each slit, j Generally, the slit height can be low at low viscosities but high viscosity 5 bindings to be great. In this way, the pressure drop of the nozzle remains relatively small so that no high pressure mixing heads are required when dispensing the reactive components, but generally more advantageous low pressure mixing heads. However, the advantage of high pressure mixing heads is the self-cleaning performed by the pushing-piston.

The overlapping threads are physically and at least partially chemically linked to each other. In external coatings, the shrinkage tension causes shrinkage and affects the reaction against thermal expansion due to heat generation. This results in shear stresses that support the described event without forming a cladding or seam.

The method is suitable for coating or fabricating articles of various diameters. Large diameters-20 use slower responsive systems than smaller diameters. When wiping the pieces from the inside, the heat generation should be adjusted so that no excessive shrinkage tension is formed, that is to say using pre-reactive products as much as possible. 25 polymers.

The novel process can also be used to treat systems containing fillers, primarily glass spheres, hollow glass spheres and glass fibers up to 6 mm in length. However, coarse-mesh webbing, fiberglass wings, yarns, etc. may also be formatted with the coating.

• •• j The angle a is adjusted to form the coating. ·· *. shoulder. The angle α is preferably 5 to 40 °, particularly preferably less than 25 °.

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Because the angle of the shoulder can be empirically calculated and determined, it is known in advance from other variables, leaving the nozzle to be set and coated! angle between surface. In this way, with the exception of the time required to achieve the desired thickness from the moment of actuation, a uniform distance of the nozzle opening from the coating point is achieved. The distance is 1 - 10 mm.

According to a particularly preferred embodiment of the method, the wide slot nozzle is disposed on a plane parallel to the axis of rotation 10 so that the coating film stretches out of the nozzle according to the wrapping angle.

It has proved possible to achieve a high quality, non-air-tight coating with this measure.

15 For wide coating, the nozzle is conveniently located in the top, upwardly rotating quarter, and in the interior, for coating, the bottom, upwardly rotating quarter. This promotes the threading of the threads to a very different degree.

The peripheral velocity is set at the aperture of the coating to be applied: * · at the extreme diameter less than the outlet velocity of the reactive mixture from the wide-slot nozzle.

.This procedure avoids the feared formation of cup-25 at the edges of the applied dressing film.

»· ·

Reactive mixtures with a pouring time of 0.3 seconds to 10 minutes are primarily treated.

It has proved to be particularly easy to handle self-reactive mixtures of such casting time and; This means that the individual threads, which are scaly overlapping. **., Are joined and merged to form a uniform coating.

I 35 108849 i

It is clear that the coating thickness must first be established at the beginning of the application. Therefore, when coating rolls, a coating width which is so palpable is always required greater than the subsequent working width of the coating, so that the 5 coating thickness build-up and release regions are outside.

The device for coating a rotatable body with a polyurethane-responsive composition comprises bearing and rotatable actuation of the body, and a wide-slot nozzle provided with a feed drive acting on the axis of rotation of the body or associated with a driving force acting along the axis of rotation.

15 What is new here is that the wide slot nozzle and the surface to be coated form a sharp angle α which opens in a direction opposite to the feed direction.

This gives the advantageous effects described in connection with the new process.

In the drawings, a new device is represented by the formula with the exemplary embodiment of the exterior coating of the pipe: and another embodiment of the exterior coating of the pipe, and is illustrated by! in the future.

Figure 1 shows the coating of the outside of the pipe. Fig. 2 shows an end view of the same device, Fig. 3 shows a longitudinal section of a device for coating,

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Fig. 4 shows the end of the same device.

| · In Figs. 1 and 2, tube 1 is bearing not shown i; · *: in a left rotating device. A longitudinally displaceable mixing head 2 is provided along the longitudinal axis of the tube 1 with a wide-slot nozzle 3. The feed is carried out at a constant speed of 35. The wide-slot nozzle is positioned at an angle of 15 ° with the tube pi 7108849 and is positioned at an angle of 85 ° β above the upwardly rotating quarter of the tube 1 at an angle of 85 °. The applied mixture layer is designated 4.

In Figures 3 and 4, tube 31 is mounted on rollers 32 and rotating rollers 33. Through tube 31, a support arm 35 is mounted on rotated rollers 34 to which a mixing head 36 is provided with a wide slot nozzle 37. longitudinally and forming an angle of 8 ° with its inner wall. The applied mixture layer is designated 38.

Example 1

A steel roll with a core diameter of 240 mm is sandblasted and rolled with about 75 g / m 2 two-component adhesive. The track has a track length of 1,400 mm.

With a 125 x 0.6 mm wide slot nozzle, a 23 mm thick PUR elastomer layer is applied by applying a reactive mixture of the composition shown below. The nozzle is mounted longitudinally parallel to the roll and · · perpendicular to an angle of 15 ° with its lower edge hanging about 5 mm above the roll surface. The point of impact of the reactive mixture is about 85 ° from the horizontal axis of the roll. The roll speed is 13 min-1, feed rate is 208 mm / min and total yield is 4,270 g / min.

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The reactive mixture has the following composition:

Component A: '· 30 85 parts of a polyether consisting of trimethylpropyl! of tile, propylene oxide (85% by weight) I and ethylene oxide (15% by weight), OH number: * ··. 35.15 parts of diethyl toluylenediamine (mixture of isomers: 35), 108849 l 0.05 parts of diazabicyclooctane, viscosity 1 (25 ° C) 1050 mPas.

| Component B: Reaction product of 100 parts of a polyether consisting of 1,2-propylene! niglycol and propylene oxide, OHIO Chapter 56, 79 parts diphenylmethane diisocyanate (70% by weight 4,4'-MDI, 30% by weight 2,4'-MDI), NCO content 12.2% , viscosity 15 (25 ° C) 1600 mPas.

Mixing ratio: 100 parts of component A, 84 parts of component B.

20 Operating time 5 seconds.

; ·· Elastomer Properties: * · Hardness (Shore A) 90,) Tensile strength (MPa) 20, 25 elongation at break (%) 450.

,. Example 2 '!!! A steel roll with a core diameter of 260 mm * is coated with a 22 mm thick coating. The roll speed is 28 min-1 and the wide-slot nozzle feed is 30182 mm / min. The nozzle setting angle α was set at 17 °.

• * i * * j »i * I 9 108849 The following composition is used:

Component A:! 100 parts prepolymer containing 9.8% by weight of NCO 5 consisting of 4,4'-diphenylmethane diisocyanate and polyether carbonate having an average molecular weight of 2,000.

Component B: 19.5 parts of 3,5-bis-thiomethyl-toluylenediamine (mainly 2,4-diamine compound).

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Component C: 15 parts of a polyol-amine mixture consisting of 1.5 parts of diethyl toluylenediamine having an NH number of 630 and 3.5 parts of polyether 'carbonate having an average molecular weight of 2,000.

20

Component A is dosed at 90 ° C; 3,000 g / min, component B at 25 ° C 585 g / min · ** and component C at 50 ° C 150 g / min.

, * Example 3: ·. *. 25 In order to provide a steel tube of nominal size 360 mm and length 5000 mm · · »mm with a 15 mm inner liner, the following procedure is used: ♦ ·» * The same composition as in Example 1 is used.

Spray on a sandblasted surface and / * · J 30 or roll 80 g / m 2 adhesive. After a predetermined hour of drying time, a mechanical mixing head mounted on a bracket with a wide, ··· slotted nozzle (100 x 0.6 mm) in the direction of the tube is rotated to an angle of 10 ° and pulled through the tube in a horizontal direction. : '· 35 at a speed of 300 mm / min with its lower edge 5 mm from the inside of the I 10104949 tube. The tube is attached to the rotation device and is rotated at 36 rpm. Polyol A 2 860 g / min and isocyanate prepolymer B 2 400 5 g / min are metered into the mixing head mixing chamber and continuously mixed. The coating finishes after 17 minutes.

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Claims (4)

A method of coating a body rotating about a shaft (1.31), wherein between the body (1.31) and a nozzle (3.37) ejecting a polyurethane-forming reaction mixture, a relative movement in the direction of the axis of rotation takes place. space, such that the coating is in the form of helical, overlapping windings, characterized by using a wide slit nozzle 10 (3.37) which is placed parallel to the axis of rotation at an angle α, whereby the reaction rate of the reaction mixture and the relative motion is adapted to the peripheral velocity of the rotating body (1.31) in such a way that the successive windings 15 are interlaced with scallop overlapping and seamlessly with each other, and that the winke a is adapted to the winkein of the shoulder formed at the coating so that the nozzle opening has a distance of 1 - 10 mm from the application site, and that the circumferential velocity at the largest diameter of the applied coating gene is set less than the outlet rate of the reaction mixture from the wide slit nozzle (1.37). 2. A process according to claim 1, characterized in that reaction mixtures with a casting time of 0.3 seconds to 10 minutes are processed. I I 3. Device for coating one around a shaft • | A rotary body (1.31) having a polyurethane-forming reaction mixture according to claim 1 or 2, which comprises a bearing and a rotary drive device for the body (33) and a wide slit nozzle (3,37). wherein either the wide slit nozzle (3.37) is provided with a 1 t actuating actuator operating parallel to the axis of rotation of the body (1,31) or wherein the tile> ···> (1,31) is arranged in a direction parallel to the ') the rotary shaft acting forcing drive, characterized in that the wide slit nozzle (3.37) has an inset. The surface to be coated on the body (1,31) includes a forward, angular angle α opening. 4. Apparatus according to claim 3, characterized in that the wide-slot nozzle (3.37) is arranged in a tab parallel to the axis of rotation. i IM · i | j I »* * II» I t I