Descargar Pe-design 8 Con Crack
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"1. A polymer composition for the manufacture of pipes having a design stress of at least 9.0 MPa (PE112) and a slow crack propagation resistance of at least 1000 hours at 4.9 MPa loop [sic] stress at 80ºC temperature, measured according to ISO 13479:1997, comprising 92-99%wt of a bimodal ethylene polymer and 1-8%wt of carbon black, said composition being characterised by having MFR5 measured according to ISO 1133 in the range 0.15 to 0.30 g/10 min and a density in the range 955 to 965 kg/m**(3), said polymer being composed of 42-55%wt of a low molecular weight ethylene homopolymer having MFR2 measured according to ISO 1133 in the range 350 to 1500 g/10 min and 58-45%wt of a high molecular weight copolymer of ethylene with 1-hexene, 4-methyl-1-pentene, 1-octene and/or 1-decene.
- Standard ISO 13479:1997 (D11) which according to claim 1 was used to measure the slow crack resistance at 4.9 MPa only referred to PE 80 and PE 100 resins whereas the patent related to PE112 grade resins. Since D11 stated in Annex A that the test was applicable to other polymer materials, the argument of the patent proprietor that the skilled person would know how to develop test parameters and specifications for PE112 resins was accepted.
- Although only a single example (example 4) met the product requirements of claim 1 and showed a slow crack propagation resistance of at least 1000 hours, the evidence of the patent as well as the explanation in D16 strongly suggested that the amount of comonomer together with other properties such as MFR5 and density were essential in order to obtain the required combination of design stress and slow crack propagation resistance. The application as filed together with general knowledge of the field put the skilled person into a position to understand these aspects.
"A pipe having a design stress of at least 9.0 MPa (PE112) and a slow crack propagation resistance of at least 1000 hours at 4.9 MPa hoop stress at 80ºC temperature measured according to ISO 13479:1997, formed of a polymer composition comprising 92 to 99 wt.-% of a bimodal ethylene polymer and 1 to 8 wt.-% of carbon black, wherein said polymer composition being characterized by having MFR5 measured according to ISO 1133 in the range of 0.15 to 0.30 g/10min, an FRR21/5 of at least 38, and a density in the range 955 to 965 kg/m**(3), and wherein said bimodal ethylene polymer which has a density of at least 953 kg/m**(3) is composed of 42-55 wt.-% of a low molecular weight ethylene homopolymer having MFR2 measured according to ISO 1133 in the range of 350 to 1500 g/10min and 58-45 wt.-% of a high molecular weight copolymer of ethylene with 1-hexene, 4-methyl-1-pentene, 1-octene and/or 1-decene."
(b) Examples 3 and 4 failed to disclose how the polymers had been prepared beyond a teaching that these polymers had been prepared under "slightly different" conditions to those of "Example 1" (by which it was assumed that "Example 2" was meant since Example 1 related to preparation of the catalyst, not to a polymer). The polymer composition of Example 2 had an MFR5 falling outside the scope of the claim but nevertheless resulted in a pipe with the required slow crack propagation resistance at 4.9 MPa hoop stress. In contrast example 3 having a MFR5 value within the scope of the claim resulted in a pipe with slow crack propagation resistance at 4.9 MPa of 965 hours, i.e. below the limit of 1000 hours given in the claim. Arguments of the respondent that 965 hours would be considered as equivalent to 1000 hours by rounding were not consistent with the fact that in the patent the slow crack propagation resistance data was reported to a precision of four significant figures.
The submission of the respondent that the compositions of the examples would inherently result in the required design stress was not credible. In making this argument the respondent had relied on the values of slow crack propagation resistance at 4.9 MPa. However the claim required that the composition resulted in pipes which exhibited both the specified slow crack resistance and the specified design stress, indicating that each of these properties related to different aspects of the composition's characteristics.
(d) Design stress was a known evaluation criterion for pipes, as explained in D12, referred to in the patent, and D13, which also gave the relationship between the Minimum Required Strength (MRS) and the hydrostatic design stress (page 4, section 3.6) as well as the design coefficient, which should be greater than 1,25. Even if design stress was not reported in the examples of the patent, the information contained in D13 demonstrated that it could be derived from other reported properties, in particular the slow crack propagation resistance values. These data showed that the materials of the examples would result in the specified design stress requirements.
2.2.2 According to paragraph  of the patent in suit, the problem with achieving this aim had been that when increasing the density of the bimodal polyethylene to improve design stress, the slow crack growth properties had been lost. The patent then states in paragraph  that this problem had now been overcome and that it was possible to attain a design stress of 9.0 MPA or even 10.0 MPA when the pipe comprised a composition including 92-99% by weight of a particular bimodal ethylene polymer and 1-8% by weight of carbon black.
2.2.5 In paragraph  it is stated that "It should be noted that the composition of the present invention is characterised not by any single one of the above defined features, but by their combination. By this unique combination of features it is possible to obtain pressure pipes of superior performance, particularly with regard to design stress, processability, rapid crack propagation (RCP) resistance, design stress rating, impact strength, and slow crack propagation resistance."
2.3.8 The reported properties of the polymer composition of example 3 are all within the scope of claim 1. However as regards the pipe properties, the value for slow crack propagation resistance - "Notch 4.9 MPa, 80ºC" - is reported as being 965 hours which is below the specified minimum value of 1000 hours defined in the claim.
The submission of the respondent that the value of 965 hours would, on the basis of rounding conventions, be interpreted as equivalent to 1000 and hence within the scope of the claims is inconsistent with the disclosure of the patent in suit. The data for slow crack propagation resistance at both stresses investigated are reported to four significant figures suggesting that the method employed provides results to said level of precision. Consequently there is no reason or justification derivable from the data reported in the patent to interpret a value of 965 as being, within the limits of the precision of the measurement method employed, indistinguishable from a value of 1000 hours.
Thus ordering the examples in order of increasing comonomer content, which in all examples is within the preferred range of 0.1-1.0 mol%, gives a sequence of 4(2(3 by the numbers of the examples. The trend exhibited by the properties of the compounded resin MFR5 and MFR21 is however 4(3(2. On the other hand, the values reported for slow crack propagation at 4.6 MPa and 4.9 MPa do not follow this trend and furthermore each follows different trends:
2.4.4 According to the respondent, since the claim specifies that the pipes resulting from the claimed composition have a given design stress, it has to be assumed that this requirement is met by all the examples and further that the design stress can be inferred or derived from the reported value of crack propagation resistance.
2.4.7 Also the reference by the respondent to a calculation from known properties, such as slow crack propagation resistance, based on D13, cannot be accepted since there is no indication of such a calculation in the patent in suit.
This paper discusses the adequateness of the steady state flat crack criterion for crack propagation in Engineered Cementitious Composites. The requirement of a minimum complementary energy for the fiber bridging curve is found not to be relevant in the aim of controlling the crack opening under crack propagation. 2b1af7f3a8