METHOD FOR PRODUCING A MULTILAYER PIPE CONTAINING MICROFIBERS, AND SUCH A PIPE

Abstract

A method for producing a multilayer pipe with an outer layer which forms a pipe outer contour, an inner layer which forms a pipe inner contour, and at least one intermediate layer by means of a centrifugal casting process. A mixture of resin and microfibers is supplied to a rotating die in order to form the inner layer, and a specified separation of the resin and the microfibers is produced by controlling the die rotational speed during a specified time such that the content of the microfibers in a boundary layer, which starts from the pipe inner contour, is lower than the content in a stability layer facing the intermediate layer. The invention likewise relates to a corresponding multilayer pipe.

Claims

1. A method for producing a multilayered pipe having an outer layer forming an outer pipe contour, an inner layer forming an inner pipe contour, and at least one intermediate layer, said method comprising a centrifugal casting process including: forming the inner layer by feeding a mixture of resin and microfibers into a rotating die; and separating the resin and the microfibers by controlling the rotational speed of the die during a predetermined time.

2. The method according to claim 1, wherein the mixture is at least predominantly comprised of microfibers having a length less than 4000 m.

3. The method according to claim 1, wherein the mixture is comprised of microfibers having an average length between 50 m and 500 m.

4. The method according to claim 1, wherein the microfibers are at least predominantly formed from glass fibers.

5. The method according to claim 1, wherein the mixture contains an amount from 5% to 50% of microfibers.

6. A multilayered pipe comprising: an outer layer forming an outer pipe contour; an inner layer forming an inner pipe contour; and at least one intermediate layer, wherein the inner layer is formed from resin and microfibers, and the amount of the microfibers is lower in a boundary layer starting from the inner pipe contour than in a stability layer facing the intermediate layer.

7. The multilayered pipe according to claim 6, wherein the microfibers at least predominantly have a length less than 4000 m.

8. The multilayered pipe according to claim 6, wherein the microfibers have an average length between 50 m and 500 m. cm 9. The multilayered pipe according to claim 6, wherein the microfibers are at least predominantly formed from glass fibers.

10. The multilayered pipe according to claim 6, wherein the inner layer contains an amount from 5% to 50%, of microfibers.

11. The multilayered pipe according to claim 6, wherein the inner layer has a thickness d.sub.L between 0.1 mm and 5 mm, and the boundary layer has a thickness d.sub.g less than d.sub.L/2.

Description

[0024] Further advantages, features, and properties of the invention follow from the description of preferable exemplary embodiments as well as with reference to the drawing. This shows in:

[0025] FIG. 1 a cross-sectional view of an embodiment of a wall of a pipe according to the invention

[0026] FIG. 2a an enlarged view A of the wall according to FIG. 1 upon deposition of an inner layer

[0027] FIG. 2b an enlarged view A of the wall according to FIG. 1 at separation.

[0028] Identical or identically acting components in the figures are marked with the same reference signs.

[0029] FIG. 1 gives an enlarged, sectional view of a pipe formed from several intermediate layers 4 and an outer layer 2 covering the intermediate layers 4 outwardly, and an inner layer 3 covering the intermediate layers 4 inwardly.

[0030] The intermediate layers 4 have different functions so as to stably form the pipe 1. They consist in part of resin, filler, and glass fibers called rovings.

[0031] The pipe 1 is made in a centrifugal method or centrifugal casting method as is basically described in EP 0 360 758 B1. With a die, the layers starting with the outer layer 2 via different intermediate layers 4 to the inner layer 3 are cast in a rotating die.

[0032] The material of the different layers is introduced via a lance to the die, wherein in each case a mixture of the components of the different layers is fed to the die. Examples of mixture ratios are given in FIG. 1 in percentages.

[0033] The special feature of the pipe 1 according to the embodiment lies in the introduction of the inner layer 3, which in contrast to the prior art is introduced as a mixture of resin 5 and microfibers 6. The microfibers 6 are arranged in the resin 5 such that initially they are arranged according to FIG. 2a in an equal distribution over the thickness d.sub.i of the inner layer 3. By rotation of the die, a centrifugal force is produced, by which the microfibers 6 due to the higher density are separated in the inner layer, and the microfibers move in the direction of the outside of the pipe.

[0034] After a separation time, during which in particular the resin 5 also slowly hardens, a boundary layer 3g is formed, which is predominantly made of resin with a higher resin percentage than an adjoining stability layer 3s with a thickness d.sub.s. The stability layer 3s based on the plurality of microfibers 6, has a greater stability than the boundary layer 3g. The boundary layer 3g on the other hand at the tube inner contour 1i has an extremely smooth surface.

[0035] Thus the inner layer 3 in contrast to the previous inner layers 3 has better pipe properties with the effect that the pipe 1 generally can be made thinner.

[0036] The microfibers are designed as glass fibers. The mixture of microfibers 6 and resin 5 fed for the inner layer 3 via the lance has a mixture ratio of 1:2 (one part microfiber to two parts resin).

LIST OF REFERENCE SIGNS

[0037] 1 pipe
1i pipe inner contour
1a pipe outer contour
2 outer layer
3 inner layer
3g boundary layer
3s stability layer
4 intermediate layer(s)
5 resin
6 microfibers
d.sub.L thickness of inner layer
d.sub.g thickness of boundary layer
d.sub.s thickness of stability layer