Multilayered pipe and method of manufacturing the same

Abstract

The present invention concerns a multilayered pipe comprising an inner basis layer (1) and an outer layer (2), the inner basis layer (1) and the outer layer (2) comprising polypropylene, and with a reinforcement layer (3, 6) reinforced with mineral fibers and located between the inner basis layer (1) and the outer layer (2), wherein at least one layer of the pipe located between the inner basis layer (1) and the outer layer (2) is a barrier layer (3) comprising polyamide.

Claims

1. Multilayered pipe comprising: an inner basis layer and an outer layer, the inner basis layer and the outer layer comprising polypropylene, and a reinforcement layer reinforced with mineral fibers and located between the inner basis layer and the outer layer, wherein at least one layer of the pipe located between the inner basis layer and the outer layer is a barrier layer comprising polyamide, wherein the mineral fibers have a mean length of 100-3000 microns, and wherein the mineral fibers are basalt fibers.

2. Multilayered pipe according to claim 1, wherein the polyamide in the barrier layer is polycaprolactam (PA6) or its copolymer.

3. Multilayered pipe according to claim 1, wherein the mineral fibers form a weight content of 10-15 wt % of the reinforcement layer.

4. Multilayered pipe according to claim 1, wherein the thickness of the reinforcement layer lies within a range of 25-40% of the total thickness of the pipe.

5. Multilayered pipe according to claim 1, wherein the mineral fibers lies in a range of 4-6% of the volume of the entire pipe.

6. Multilayered pipe according to claim 1, wherein the mineral fibers have a diameter of 7-20 microns.

7. Multilayered pipe according to claim 1, wherein the barrier layer and the reinforcement layer are formed as a single layer.

8. Multilayered pipe according to claim 1, wherein the reinforcement layer is located between the barrier layer and the outer layer or between the inner basis layer and the barrier layer.

9. Multilayered pipe according to claim 1, wherein the reinforcement layer comprises polypropylene.

10. Multilayered pipe according to claim 1, comprising at least one of: an additional inner adhesive layer, located inside of and adjacent to the barrier layer in a radial direction of the pipe, and an additional outer adhesive layer, located outside of and adjacent to the barrier layer in a radial direction of the pipe.

11. Multilayered pipe according to claim 1, wherein the inner basis layer and/or the outer layer is made of polypropylene copolymer, PPR or PPRCT.

12. Multilayered pipe according to claim 1, wherein the barrier layer comprises nanofillers, wherein the nanofillers comprise at least one of wollastonite or montmorillonite.

13. Multilayered pipe according to claim 1, comprising an additional outside layer comprising polyethylene and located radially outside of the outer layer.

14. Multilayered pipe according to claim 1, comprising an additional inside inliner layer located radially inside of the inner basis layer and comprising a material selected from the group consisting of PVDF, PPSF, PPSU and any combination thereof.

15. Multilayered pipe according to claim 1, wherein the reinforcement layer and the barrier layer are formed as a single layer, wherein the pipe consists of three layers arranged in the following order from inside to outside in the radial direction of the pipe: the inner basis layer, the single layer and the outer layer.

16. Multilayered pipe according to claim 1, consisting of four layers arranged in the following order from inside to outside in the radial direction of the pipe: the inner basis layer, the reinforcement layer, the barrier layer and the outer layer; or the inner basis layer, the barrier layer, the reinforcement layer, and the outer layer.

17. Multilayered pipe according to claim 1, consisting of six layers arranged in the following order from inside to outside in the radial direction of the pipe: the inner basis layer, the reinforcement layer, the inner adhesive layer, the barrier layer, the outer adhesive layer and the outer layer; or the inner basis layer, the inner adhesive layer, the barrier layer, the outer adhesive layer, the reinforcement layer, and the outer layer.

18. Multilayered pipe according to claim 1, the multilayered pipe prepared by one of an extrusion process, an injection-molding process and a blow-molding process.

19. Multilayered pipe according to claim 1, wherein the mineral fibers are aminosilane treated mineral fibers.

20. The multilayered pipe according to claim 1, wherein the mineral fibers have a mean length of 400-2000 microns.

21. A multilayered pipe comprising: an inner basis layer comprising polypropylene; an outer layer comprising polypropylene; and a combined barrier and reinforcement layer located between the inner basis layer and the outer layer, wherein the combined layer is reinforced with mineral fibers and comprises polyamide, wherein the mineral fibers have a mean length of 100-3000 microns, and wherein the mineral fibers are basalt fibers.

22. The multilayered pipe according to claim 21, further comprising at least one of: an additional inner adhesive layer, located inside of and adjacent to the combined layer in a radial direction of the pipe, and an additional outer adhesive layer, located outside of and adjacent to the combined layer in a radial direction of the pipe.

23. The multilayered pipe according to claim 21, further comprising an additional outside layer comprising polyethylene and located radially outside of the outer layer.

24. The multilayered pipe according to claim 21, further comprising an additional inside inliner layer located radially inside of the inner basis layer and comprising a material selected from the group consisting of PVDF, PPSF, PPSU and any combination thereof.

25. The multilayered pipe according to claim 21, wherein the thickness of the combined layer lies within a range of 25-40% of the total thickness of the pipe.

26. The multilayered pipe according to claim 21, wherein the volume of the mineral fibers lies in a range of 4-6% of the volume of the entire pipe.

27. The multilayered pipe according to claim 21, wherein the mineral fibers have a mean length of 400-2000 microns.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 depicts a three layered-pipe configuration according to an embodiment of the present invention.

(2) FIG. 2 depicts a five layered-pipe configuration according to an embodiment of the present invention.

(3) FIG. 3A depicts a four layered-pipe configuration according to an embodiment of the present invention.

(4) FIG. 3B depicts a four layered-pipe configuration according to an embodiment of the present invention.

(5) FIG. 4A depicts a six layered-pipe configuration according to an embodiment of the present invention.

(6) FIG. 4B depicts a six layered-pipe configuration according to an embodiment of the present invention.

DETAILED DESCRIPTION

(7) FIG. 1 depicts a preferred embodiment of the present invention being a three-layer pipe configuration. The pipe comprises an inner basis layer 1, an outer layer 2, as well as a barrier layer 3, which is also a reinforced layer.

(8) The basis layer 1 and the outer layer 2 both comprise polypropylene random copolymer (PPR). However, variants of these embodiments alternatively or additionally comprise a different polypropylene in the broad sense of the term, such as one or several materials classified to be of the type ‘polypropylene random crystallinity temperature’ (PPRCT).

(9) The barrier layer 3 comprises polypropylene and the polyamide PA6, and it is reinforced with basalt fibers with a weight content of around 13 wt % with respect to the barrier layer 3. The basalt fibers have a diameter of about 11-12 microns and a mean length of about 1150-12500 microns. The thickness of the barrier layer 3 amounts to about 28% of the total thickness of the pipe, and the total volume of the basalt fibers amounts to about 5% of the total volume of the entire pipe.

(10) The reinforced barrier layer 3 is advantageous over a non-reinforced barrier layer, as it promotes especially high resistance against shrinking effects in a welding portion of the pipe. In particular, the presence of the basalt fibers in the barrier layer 3 compensates for the polyamide's susceptibility to the occurrence of shrinking effects, namely in a welding portion.

(11) As the polyamide and the basalt fibers are mixed in a composite compound layer, the synergetic effect between the two compounds is especially pronounced in this embodiment.

(12) Thus, the pipe depicted in FIG. 1 shows beneficial welding properties, and it provides an effective shielding effect by virtue of the barrier layer 3, the risk of a deterioration of the shielding effect, especially in the proximity of welding zones being severely reduced. In particular, thermal expansion forces which might promote shrinking effects are uniformly distributed across a larger area of the pipe. The pipe's barrier effects can thus be kept intact across the entire zone. Forces promoting shrinking effects are effectively equalized due to the synergetic effect occurring between the polyamide and the basalt fibers in the reinforced barrier layer 3.

(13) The presence of the basalt fibers also reduces the affinity of the barrier layer 3 for thermal expansion in general, and it improves the impact strength of the pipe. In this way, the barrier layer's resistivity against varying environmental conditions, especially very high, low or varying temperatures, can be further improved not only in welding zones, but in the whole pipe. In addition, the reduction of impact strength allows to raise the maximum pressure of fluids transported through the multilayered pipe, yet again offering the possibility of using smaller pipes as opposed to pipes known from the prior art for similar applications involving the same demands regarding maximum pressure. In this way, pipe constructions can be maintained in more compact constructional spaces, hence assisting modern and compact space-efficient building technology.

(14) Also the embodiment of the present invention depicted in FIG. 2 comprises a reinforced barrier layer 3, comprising polypropylene, PA6 as a polyamide, as well as basalt fibers, present with a weight content of about 13-14 wt %. The thickness of the barrier layer 3 amounts to about 30% of the total thickness of the pipe. The volume of the basalt fibers amounts to about 5% of the total volume of the pipe. The advantageous properties of this pipe are similar to those explained with regard to the previous embodiment, so that not all of the advantages will be explained again. Reference is made to the previous explanations.

(15) Additionally, the embodiment of FIG. 2 comprises an inner adhesive layer 4, located between inner basis layer 1 and the barrier layer 3, as well as an outer adhesive layer 5, located between the barrier layer 3 and the outer layer 2. Both the inner and outer adhesive layers 4, 5 comprise polypropylene copolymer grafted with maleic anhydrite.

(16) The adhesive layers 4, 5 promote a strong adhesive cohesion between the barrier layer 3 and the inner and outer layers 1, 2, respectively.

(17) Also the pipe of FIG. 2 prevents against shrinking effects occurring in a welding portion of the pipe. The basalt fibers in the barrier layer compensate for the barrier layer's susceptibility to shrinking effects. Nevertheless, also the five-layer pipe can be cost-efficiently manufactured, while providing a shielding effect by virtue of the barrier layer 3. Said barrier layer 3 is less prone to display any form of leakage in the proximity of a welding portion of the pipe, due to the reinforcement with the fibers. Hence, forces which might lead to shrinking effects in known pipes are distributed across a larger area (also in the barrier layer 3), keeping the pipe's barrier effects intact across the entire area.

(18) The five-layered pipe of FIG. 2 is especially advantageous, as it exhibits excellent stiffness and barrier properties, thermal expansion properties and crack resistance properties, while ensuring a very strong cohesive structure of the pipe, thus further promoting longevity of the pipe. Such high-quality pipes are especially advantageous for use in high-quality building construction.

(19) FIGS. 3A and 3B of the present application depict embodiments of the present invention consisting of four-layer pipe configurations.

(20) The advantageous properties of the pipes of FIGS. 3A and 3B are similar to those explained with regard to the previous embodiments, so that not all of the advantages will be explained anew and reference is made to the previous explanations.

(21) The pipe depicted in FIG. 3A consists of four layers arranged in the following order from inside to outside in a radial pipe direction: an inner basis layer 1, a reinforcement layer 6, a barrier layer 3, and an outer layer 2.

(22) The inner basis layer 1 and the outer layer 2 are configured analogously as in the case of the embodiments depicted in FIGS. 1 and 2. The barrier layer 3 comprises polypropylene and the polyamide PA6. The reinforcement layer 6 of this embodiment comprises polypropylene and is reinforced with basalt fibers with a weight content of around 10.5 wt %, the basalt fibers having a mean diameter of about 11-12 microns and a mean length of about 1100-1300 microns. The thickness of the barrier layer 3 amounts to about 31% of the total thickness of the pipe. The volume of the basalt fibers amounts to about 5% of the total volume of the pipe.

(23) A difference between the configurations depicted in FIGS. 3A and 3B is that the order of the barrier layer 3 and the reinforcement layer 6 is reversed in the radial direction of the pipe. In other words, the pipe depicted in FIG. 3B consists of four layers arranged in the following order from inside to outside in a radial pipe direction: an inner basis layer 1, a reinforcement layer 6, a barrier layer 3, and an outer layer 2

(24) The configurations of FIGS. 3A and 3B are especially advantageous, as the separate formation of the barrier layer and the reinforcement layer 6 is cost-efficient. Nevertheless, the interaction between the compensatory effects of the barrier layer 3 and of the reinforcement layer 6 is strong.

(25) FIGS. 4A and 4B of the present application depict embodiments of the present invention consisting of six-layer pipe configurations.

(26) The advantageous properties of the pipes of FIGS. 4A and 4B are similar to those explained with regard to the previous embodiments, so that not all of the advantages will be explained again. Reference is made to the previous explanations.

(27) A difference between the configurations depicted in FIGS. 4A and 4B is that the order of the barrier layer 3 and the reinforcement layer 6 is reversed in the radial direction of the pipe.

(28) The pipe of FIG. 4A consists of six layers arranged in the following order from inside to outside in the radial direction of the pipe: an inner basis layer 1, an inner adhesive layer 4, a barrier layer 3, an outer adhesive layer 5, a reinforcement layer 6, and an outer layer 2.

(29) The pipe of FIG. 4B consists of six layers arranged in the following order from inside to outside in the radial direction of the pipe: an inner basis layer 1, a reinforcement layer 6, an inner adhesive layer 4, a barrier layer 3, an outer adhesive layer 5, and an outer layer 2. This arrangement has the additional advantage that the barrier layer 3 is additionally protected by a radially outer reinforcement layer 6. This further lowers the chance of polyamide getting mixed with polypropylene during welding.

(30) Both in the pipe of FIG. 4A and of 4B, the barrier layer 3 comprises polypropylene and the polyamide PA6. The reinforcement layer 6 of comprises polypropylene and is reinforced with basalt fibers with a weight content of around 12 wt % with respect to the reinforcement layer 6 as a whole, the basalt fibers having a mean diameter of about 11-12 microns and a mean length of about 1100-1300 microns. The thickness of the barrier layer 3 amounts to about 37% of the total thickness of the pipe, and the volume of the basalt fibers amounts to about 5% of the total volume of the pipe.

(31) The pipes depicted in FIGS. 4A and 4B provide a good balance between barrier effects, good weldability without the need to peel off an part of the outer layers, good thermal expansion properties, stiffness, crack prevention, easy and cost-efficient manufacturability, resistance against shrinkage effects in molded sections, suitability to be employed under extreme environmental temperature and/or moisture conditions or strongly varying environmental conditions, wherein the thermal expansion properties are especially effectively reduced, and the barrier properties are strongly enhanced. Additionally, the six-layered pipe exhibits remarkably low brittleness.

(32) The following tests have been carried out. Six layer embodiments were used, wherein the oxygen barrier fulfilled the norm DIN 4726/ISO 21003 (permeability lower than 3.6 mg/m.sup.2 day). These tests revealed that the pipes according to the present invention display about three times smaller thermal expansion coefficients compared to monolayer pipes known from the prior art. Specifically, thermal longitudinal expansion coefficients using pipes with basalt fiber filler levels of 10% to 30% were measured in a range of about 3.Math.10.sup.−5 to 6.5.Math.10.sup.5 mm/mm/° C. for temperature ranges between 25° C. and 80° C.

(33) Standard tests for the pressure performances according to the norm 1501167 under 4.3 MPa/95° C. were carried out for six layer pipe embodiments and for three layer basalt fiber filled pipes without a barrier layer. The six layer pipes according to the present invention could sustain pre-defined pressure performances for an about 10% longer period of time, taking the number of hours until failure into account.

(34) In central heating installations, the stiffness and the impact strength of the six layer embodiments were compared with basalt filled pipes without a barrier layer and with six layer basalt filled pipes with an EVOH oxygen barrier layer. The stiffness of the six layer pipes according to the present invention was about 40% higher. The impact strength was increased by about 70% with respect to the basalt filled pipes without a barrier and by about 90% with respect to the six layer basalt filled pipes with an EVOH oxygen barrier.

(35) Moreover, the impact strengths (in Joules) were measured for a six layer pipe according to the present invention including 14% basalt fibers and for a six layer basalt filled pipe with an EVOH barrier using H50 as a test, described in the norm EN1411, performed at 0° C.:

(36) TABLE-US-00001 Thickness (barrier) PA barrier EVOH barrier 0.00 (without barrier) 4.9 4.9 0.10 7.9 4.9 0.20 8.3 4.4 0.30 9.3 4.4 0.40 10.3 4.4 0.50 10.8 3.9

(37) In addition, their permeabilities (measured in mg/m.sup.2 day) were measured using a method fulfilling the norm ISO17455:

(38) TABLE-US-00002 Thickness (barrier) PA barrier EVOH barrier 0.00 (without barrier) 7.84 7.84 0.10 3.32 1.15 0.20 1.19 0.05 0.30 0.49 not measured 0.40 0.12 not measured 0.50 0.04 not measured

(39) Finally, their pressure performance (measured in number of hours until failure; hoop stress 4.3 MPa at 95° C.) was measured using a method fulfilling the norm ISO1167 with an average of 10 samples per pipe:

(40) TABLE-US-00003 Thickness (barrier) PA barrier EVOH barrier 0.00 (without barrier) 1441 1441 0.10 1554 321 0.20 1572 84 0.30 1301 not measured 0.40 984 not measured 0.50 522 not measured

(41) Each and every one of the embodiments of the pipe according to the present invention depicted in FIGS. 1 to 4B was manufactured using injection-molding, and the basalt fibers were in each case chemically treating by aminosilane in order to promote a good adhesion of the basalt fibers to polypropylene. In the case of the embodiments wherein the barrier layer is a reinforced layer, a good adhesion between the basalt fibers and PA6 can also be realized.

(42) While the embodiments depicted in FIGS. 1 to 4B all comprise basalt fibers for reinforcing the reinforcement layer, it is to be understood that also other mineral fibers such as carbon fibers, glass fibers, or a mixture of these fibers, may be used to reinforce the reinforcement layer in variants of these embodiments. However, glass fibers are preferable, and basalt fibers are especially preferable, due to their specific material properties such as tensile strength, their workability and the costs involved in the manufacturing steps.

(43) While the embodiments of FIGS. 1 to 4B merely comprise basalt fibers as reinforcing fibers, it is to be understood that variations of these embodiments can be realized, additionally comprising nanofillers, for example wollastonite or montmorillonite. The weldability, resistance against shrinkage effects in the proximity of a welding zone and thus prevention of barrier effect deteriorations is further promoted by virtue of the presence of nanofillers, and they also further promote a reduction of the thermal expansion of the pipe and an improvement of its impact strength.

(44) Although the inner basis layer and the outer layer of the embodiments depicted in FIGS. 1-4B comprise PPR, the skilled person will readily conceive variations, wherein any one of the two layer alternatively or additionally comprises: polyvinylidene fluoride (PVDF), polyvinylidene chlorate (PVdC), polyphenylene sulfide (PPS) or polyphenylsulfone (PPSF or PPSU). Any one of these compounds or a combination thereof increases the temperature and chemical resistance of the layer and thus of the entire pipe.

(45) Many additional variations and modifications are possible and are understood to fall within the framework of the invention.