Pressure vessel

Abstract

This invention relates to a pressure vessel comprising a hollow body comprising endless fibers embedded in a thermoplastic polymer, in which the thermoplastic polymer comprises one or more polyamides containing one or more aliphatic monomeric units, wherein the one or more polyamides have a CH2-ratio of at least 5.5 and less than 10, calculated by □ identifying the number of different aliphatic monomeric units in the one or more polyamides; □ determining the number of CH2 groups per aliphatic monomeric unit for each of these different aliphatic monomeric units; □ calculating the sum of the so determined numbers of CH2 groups; □ dividing said sum by the number of different aliphatic monomeric units in the one or more polyamides; taking into account only the aliphatic monomeric units present in the one or more polyamides in an amount of at least 10 wt % with respect to the total weight of the one or more polyamides.

Claims

1. A pressure vessel comprising: a hollow body comprising a thermoplastic matrix and 10 and 65 volume % of endless fibers, based on total volume of the endless fibers and the thermoplastic matrix of the hollow body, embedded in the thermoplastic matrix, wherein the endless fibers are selected from the group consisting of glass fibers, carbon fibers and combinations thereof, and wherein the thermoplastic matrix comprises one or more polyamides containing one or more aliphatic monomeric units, wherein the one or more polyamides are selected from the group consisting of PA610, PA612 as well as blends and copolyamides thereof, and wherein the one or more polyamides have a CH2-ratio of at least 5.5 and less than 10, calculated by (i) identifying the number of different aliphatic monomeric units in the one or more polyamides; (ii) determining the number of CH2 groups per aliphatic monomeric unit for each of these different aliphatic monomeric units; (iii) calculating the sum of the so determined numbers of CH2 groups; and (iv) dividing said sum by the number of different aliphatic monomeric units in the one or more polyamides; taking into account only the aliphatic monomeric units present in the one or more polyamides in an amount of at least 10 wt % with respect to the total weight of the one or more polyamides, and wherein the pressure vessel has a burst pressure of at least 25 bar as measured according to the hydrostatic pressure burst test described in ECE R110.

2. The pressure vessel according to claim 1, further comprising a liner formed of a material comprising a metal and/or a thermoplastic polymer selected from the group consisting of PA-6, PA-66, PA-410, ethylene vinyl alcohol and combinations thereof.

3. The pressure vessel according to claim 1, wherein the CH2-ratio is between 5.6 and 9.5.

4. The pressure vessel according to claim 1, wherein burst pressure of the pressure vessel is at least 300 bar, as measured according to the hydrostatic pressure burst test described in ECE R110.

5. The pressure vessel according to claim 1, wherein the thermoplastic matrix comprises one or more polyamides containing monomeric units derived from aliphatic monomers in an amount of at least 60 wt % with respect to the total weight of the thermoplastic matrix.

6. The pressure vessel according to claim 1, wherein the thermoplastic matrix further comprises a heat stabilizer, a flame retardant and/or a colorant.

7. The pressure vessel according to claim 1, wherein the thermoplastic matrix comprises at least 60 wt % PA-410 with respect to the total weight of thermoplastic matrix, and wherein the hollow body comprises between 20 and 55 vol % of the endless fibers with respect to the total volume of the endless fibers and the thermoplastic matrix of the hollow body.

8. The pressure vessel according to claim 1, wherein the pressure vessel is a pressurized tank for compressed natural gas (CNG) tank or a pressurized tank for hydrogen gas.

Description

EXAMPLES

(1) Measurements were performed on various thermoplastic matrices in order to show their suitability for use in a thermoplastic composite pressure vessel. Various polyamides with various CH2-ratios were tested. Results are given in Table 2.

(2) Acid resistance test: 15 Izod bars with the polyamides as described in Table 2, were exposed to a solution of 30% H2SO4 in a petri-dish. The level of liquid was 2 mm so that the 4 mm thick bars were immersed on one side only. Separate petri-dishes were used for every take-out time (25, 50 and 100 hrs). After immersion, the bars were washed with an excess of water taking care that the upper half did not come in contact with the strong acid. After washing, the bars were dried with paper. Flexural test according to ISO178: the acid treated surface faced downward during the flexural test (non-exposed side facing up-wards).

(3) Table 2 clearly indicates that polyamides with a CH2-ratio between 5.5 and less than 10, exhibited a combination of high acid resistance and good structural integrity. A good structural integrity is observed when the flex modulus is sufficient high in combination with a higher HDT. Examples 1 to 4 all exhibited a sufficient high flex modulus in combination with a high HDT, which makes them good candidates to be employed in a vessel according to the invention.

(4) The most preferred polyamide being PA-410, example 1, clearly combines a high flex modulus with high HDT, which surprisingly when employed in a vessel, showed a very strong and robust vessel.

(5) A hollow body was prepared by wrapping a tape comprising PA-6. Subsequently a tape comprising 65 wt % endless glass fibers and 35 wt % PA-410 was wrapped, based on the total weight of the tape around a mandrel and using heat to consolidate these wrappings. The vessel was created by attaching bosses to the hollow body, as known in the prior art. The vessel was filled with natural gas and the vessel was subjected to the Bonfire test. This test is described in ECE R110. In short, during Bonfire test, a vessel while containing gas, is subjected to 850° C. at the outside of the vessel. A vessel passes the test if the vessel does not explode, but the vessel vents the contained gas through a pressure relief device. Surprisingly, the vessel produced with a thermoplastic matrix comprising one or more polyamides containing one or more aliphatic monomeric units, wherein the one or more polyamides have a CH2-ratio of at least 5.5 and less than 10 taking into account only the aliphatic monomeric units present in the one or more polyamides in an amount of at least 10 wt % with respect to the total weight of the one or more polyamides, passed the Bonfire test, even though the melting temperature of PA-410 is 248° C., thus substantially lower than the heat the vessel was subjected to. This is a major achievement as the vessel according to the invention allows for thermoplastic composite pressure vessels which can contain high amounts of gasses or liquids while maintaining a high safety standard and after the life time the vessel may be recycled into prime applications, which was not possible for thermoset tanks.

(6) TABLE-US-00002 TABLE 2 Various polyamides and results comparative comparative exam- comparative comparative example A example B ple 1 example 2 example 3 example 4 example C example D ISO PA-6 PA-66 PA-410 PA-610 PA-612 PA-1010 PA-11 PA-12 CH2-ratio 5 5 6 7 8 9 10 11 flex modulus (GPa) ISO178 2.84 2.94 2.7 2.05 2.38 1.74 1.31 permeability CNG 0.1 0.6 @25 C. (cm3.mm/m2/day/bar) permeability H2 1.1E−16 6.7E−16 @20° C. (mol/m/s/Pa) flex modulus after 0.84 0.88 2.02 1.35 1.89 100 hrs acid exposure (GPa) retention after H2SO4 29.8 29.9 74.5 65.9 79.2 exposure (%) HDT 0.45 MPa ISO-R-75 150 215 175 140 135 110 145 135 method B HDT 1.8 MPa ISO-R-75 50 75 75 55 62 50 50 55 method A Melting temperature 222 262 248 222 218 202 189 179 (° C.)