DETAILED ACTION
Notice of Pre-AIA or AIA Status
The present application, filed on or after March 16, 2013, is being examined under the first inventor to file provisions of the AIA .
Continued Examination Under 37 CFR 1.114
A request for continued examination under 37 CFR 1.114, including the fee set forth in 37 CFR 1.17(e), was filed in this application after final rejection. Since this application is eligible for continued examination under 37 CFR 1.114, and the fee set forth in 37 CFR 1.17(e) has been timely paid, the finality of the previous Office action has been withdrawn pursuant to 37 CFR 1.114. Applicant's submission filed on 01/12/2026 has been entered.
Claim Rejections - 35 USC § 103
The following is a quotation of 35 U.S.C. 103 which forms the basis for all obviousness rejections set forth in this Office action:
A patent for a claimed invention may not be obtained, notwithstanding that the claimed invention is not identically disclosed as set forth in section 102, if the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains. Patentability shall not be negated by the manner in which the invention was made.
The factual inquiries for establishing a background for determining obviousness under 35 U.S.C. 103 are summarized as follows:
1. Determining the scope and contents of the prior art.
2. Ascertaining the differences between the prior art and the claims at issue.
3. Resolving the level of ordinary skill in the pertinent art.
4. Considering objective evidence present in the application indicating obviousness or nonobviousness.
Claims 1-7, 11-13, 15, 17 and 19-26 are rejected under 35 U.S.C. 103 as being unpatentable over Yahaya et al. US 2018/0345229 A1 and in view of Wu et al. Synthesis and properties of cardo-type polyimides containing hydroxyl groups for application in specific detection of fluoride ion, Dyes and Pigments 173, 2020, 107924.
Yahaya teaches co-polyimide membranes for separating components of sour natural gas where embodiments can include at least three distinct moieties polymerized together, the moieties including a 2,2' -bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) based moiety; a 9,9-bis(4-aminophenyl) fluorene (CARDO) based moiety; and 2,3,5,6-tetramethyl-1,4-phenylenediamine (durene diamine) based moiety (Abstract and reference claim 1).
Reference Wu teaches synthesis and properties of cardo-type polyimides containing hydroxyl groups (Title) which can be used for gas separation membranes (page 4, 2nd col, last sentence of 2nd para).
Regarding claims 1-7, 11-12, 17, 19-20 and 22-23, Yahaya discloses preparation of aromatic co-polyimide dense film membrane (instant claim 23) where a random co-polyimide 6FDA-durene/CARDO (3:1) is synthesized such that the molar ratio of the durene diamine based moiety to the CARDO based moiety is 3:1, which will result in structural repeat unit corresponding to Formula (I) to Formula (II) in a molar ratio of about 3:1 (paras [0045], [0047], page 5 Table 1, 1st entry, reference claim 3). The structure of the repeat units are presented in reference Figure 1 as depicted below.
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Yahaya is silent on the presence of specific -OH substitution on the fluorene moiety (R3 and R4) as required by the claims, however highlights that various chemical modifications including substitution of pertinent moieties can be carried out to improve the performance of co-polyimides (paras 15, 16 and 33). Yahaya additionally guides a skilled artisan to functionalize the copolyimide moieties with polar functional groups to manage crosslinking of the polymers in order to enhance the separation performance and optimize copolyimides for gas separation (paras [0045] and [0068]).
A person having ordinary skill in the art would look to analogous copolyimide art which employs polar functional groups to further optimize the polyimide properties. Refence Wu teaches substantially similar cardo-type polyimides containing hydroxyl groups (Title and Abstract), and discloses copolyimide such as PI-3 which is derived from monomers 9,9-bis(4-aminophenyl)-2,7-dihydroxy-fluorene (AHF) and 6FDA, as shown (page 3, Fig 2 (c)):
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Advantageously, Wu provides the motivation for incorporating hydroxyl polar groups into the polyimide chains as it helps to improve solubility, thermal and mechanical properties since the hydroxyl groups provide strong intermolecular associations through forming H-bond interactions (Introduction, second para).
It would be obvious to combine Yahaya in view of Wu where in the random co-polyimide 6FDA-durene/CARDO (3:1), the CARDO units are substituted with hydroxyl groups at the same position as taught by Wu. Such a co-polymer meets the claimed requirements structural repeat units corresponding to Formulae (I),(I-B), (II), (II-B), where X and Y are C (CF3)2 (instant claims 5-7), A is phenylene substituted with four methyl groups, such that R5 is methyl (instant claims 2-4, 17 and 19) and n=4 (instant claim 20) R3 and R4 are -OH, a =0 (instant claim 11), and where the structural repeat units of Formula (I) and the Formula (II) are present in a molar ratio of about 3:1 (instant claims 12) (and where also the structural repeat units corresponding to Formula (I-B) and the Formula (II-B) are in a molar ratio of about 3:1 (instant claims 17 and 22).
It would have been obvious to one of ordinary skilled in the art before the effective filing date of the invention to have substituted Yahaya’s CARDO based moieties with polar hydroxyl substituents as taught by Wu for the same application of creating polyimides with improved thermal and mechanical properties.
Regarding claims 13 and 21, Yahaya discloses random copolyimides 6FDA-durene/CARDO with molar ratio of 3:1, 1:1 and 1:3 (reference claim 3, 4 and 5 and page 6, Table 2), and further adds (para [0056]) that the content of CARDO in the copolymer of CARDO and durene was varied from about 25 mol % to about 75 mol %, which will lead to random copolyimides 6FDA-durene/CARDO with molar ratio of 1:3 to 3:1, which encompasses the claimed requirement of 2:1 (para [0056]). "[A] prior art reference that discloses a range encompassing a somewhat narrower claimed range is sufficient to establish a prima facie case of obviousness." In re Peterson, 315 F.3d 1325, 1330, 65 USPQ2d 1379, 1382-83 (Fed. Cir. 2003). See MPEP 2144.05 I.
Regarding claim 15, Yahaya teaches block copolymer 6FDA-durene)/(6FDA-CARDO)(15,000)/(15,000), such that the total Mn would be 30,000 (para [0052]). Obvious composition of Yahaya in view of Wu, would be such that the copolymer as discussed when addressing claim 1 is adjusted to have Mn of 30,000, thus making the claimed requirement obvious.
Regarding claim 24, Yahaya teaches the creation of co-polyimide membrane where the film is solution cast, and dried under vacuum at elevated temperature to remove any residual solvent, thereby generating a membrane with almost 100 wt% of the polymer, which meets the claimed requirement (Yahaya para [0055]).
Regarding claims 25-26, Yahaya teaches the membrane and the method for separating the components of a sour natural gas feed (see reference claims 1 and 11). Yahaya further discloses that the feed gas is passed through the membrane at different gas feed pressure, and that the simulated sour gas consists of 10 vol % of both CO2 and H2S in the feed gas prior to passing the membrane, making the claimed requirement obvious (para [0062] and Table 7, with 10 vol% H2S).
Claim 16 is rejected under 35 U.S.C. 103 as being unpatentable over Yahaya in view of Wu, as applied to claim 1 above, and further in view of Blinka et al. US 5,042,992.
Regarding claim 16, Yahaya in view of Wu is silent on the number-average molecular weight of the copolyimide per the claimed limitation. Yahaya highlights the use of the co-polyimides based membranes for gas separation (Title and Abstract). Yahaya further notes that various modifications and changes can be made within the scope of the disclosure (para [0073]). In order to optimize the performance of the gas separation membrane a skilled artisan would seek guidance from analogous art such as Blinka which also teaches polyimide based semipermeable membranes (Abstract). Blinka recommends a molecular weight in the range of 30,000-500,000, as the specified range of molecular weight is more suited in preparing gas separation membranes as compared to lower molecular weight polyimides which are useful for films, adhesives or coatings (col 3, lines 20-27).
It would have been obvious to one of ordinary skilled in the art before the effective filing date of the invention to have adjusted the number molecular weight of the copolyimide of Yahaya in view of Wu to 100,000 g/mol as taught by Blinka (which is within Blinka’s recommended range) for the same application of creating membranes which are suited for gas separation.
Response to Arguments
Applicant's arguments filed on 01/12/2026 have been fully considered but they are not persuasive.
Applicant reiterates (page 7 of 11) that primary reference Yahaya does not disclose or suggest that the CARDO moiety is substituted with -OH groups as required by the amended claims. Applicant adds that Yahaya only mentions an alkyl substituted CARDO as an example, and that the exemplified compounds of Yahaya are unsubstituted CARDO.
As discussed in the rejection while Yahaya does not specify -OH substitution on CARDO moiety, Yahaya provides appropriate guidance for an artisan skilled in the art to
chemically modify with functional groups which include polar groups to manage the crosslinking of the co-polyimides by including substitution of pertinent moieties to optimize copolyimides to enhance their gas separation performance (paras 15, 16, 33, 45 and 68). This would encourage a skilled practitioner in the art to sought out similar CARDO based copolyimides which employ polar functional groups to optimize the polyimide properties.
Applicant further discusses (pages 8 and 9 of 11) that the secondary reference Wu which teaches -OH substituted CARDO monomers should not be utilized to teach the required substitution on CARDO monomers since the effects of incorporating hydroxyl groups into the polymer backbone can be unpredictable. Applicant provides two literature references Alaslai et al. Macromol Rapid Commun. (2017) 38, 1700303 and Alaslai et al. J. Membrane Sci. (2016) 505, 100-107; to provide evidence that the hydroxyl functionalization of the copolyimides decreases the permeability.
With regard to literature reference Alaslai et al. Macromol Rapid Commun. (2017) 38, 1700303, while it is acknowledged lower gas permeability was observed for hydroxy functionalized 6FDA-DAT1-OH vs its unsubstituted counterpart 6FDA-DAT1 due to tighter chain packing. The triptycene based monomers (DAT1 and DAT1-OH) as shown below are different from the CARDO based copolyimides as taught by Yahaya and Wu. The presence of hydroxyl substitution cannot be generalized to any aromatic ring based diamine structures, since the 3D steric conformation of the triptycene based monomer is different than the CARDO monomer and the ring position of the -OH groups would also play a role in the interchain packing efficiency.
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With respect to reference Alaslai et al. J. Membrane Sci. (2016) 505, 100-107, the reference discloses hydroxyl functionalized m-phenylene diamine moieties which are part of the polyimide, as depicted below. It is observed that introducing increasing amounts of hydroxyl groups in the m-phenylene diamine units, reduces gas permeability. It is again noted that the m-phenylene diamines does not share structural similarity or steric conformation arrangement with the CARDO based monomers and thus a direct comparison of the structure packing efficiency and its impact on permeability cannot be made.
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Based on the data presented by the above two literature references, applicant argues that the mere presence of hydroxyl groups would be expected to decrease the permeability of the polyimides. The applicants found that hydroxyl groups behaved differently than expected and the permeability coefficients of the claimed membranes increased, due to the special arrangement of hydroxyl groups. Applicant adds (page 9 and 10 of remarks) that permeability coefficients of the membranes of the present application (Example 10) are higher as compared to those of similar membranes in Yahaya without the hydroxyl substituents (Table 2).
It can be observed that the 6FDA-durene/6FDA-CARDO(OH) and 6FDA-DAM/6FDA-CARDO(OH) (last three entries in Table 2, instant specification) show increased permeability in comparison to 6FDA-CARDO (Row 3, Table 2). However, the comparative example 6FDA-CARDO is missing both hydroxyl groups as well as additional durene (or DAM) monomers. As can be seen from Rows 1 and 2 (Table 2), the polyimides with durene and DAM have increased levels of permeability coefficients. Thus, it is unclear in the inventive examples (last three rows, Table 2) if the increased permeability is due to the presence of durene or DAM monomers in the copolyimide backbone or due to the presence of hydroxyl groups in the CARDO moieties. Applicants have not laid the requisite foundation upon which to conclude that the demonstrated results are “really unexpected”. It is also highlighted that the copolyimides derived from teachings of Yahaya and Wu would have substantially similar gas transport properties as the instant inventive examples since they possess the same copolyimide backbone and the same position of the -OH groups in the CARDO moieties.
Applicant further adds that one of skill in the art would not look to Wu to modify the membranes of Yahaya, as Wu is directed to CARDO-type polyimides containing hydroxyl groups that are useful as chemosensors and that the membranes of Wu are
not used for gas separation applications. Wu clearly discusses in Introduction (second para, first sentence), the use of functional polyimides containing hydroxyl groups for gas separation membranes. Wu further adds in page 4, (second column, second para, last sentence) that the CARDO hydroxyl functionalized polyimides may be used for gas separation membranes. Thus, both Yahaya and Wu disclose the utilization of CARDO based polyimides for gas separation membranes.
Applicant’s arguments against both Yahaya and Wu are found to be unconvincing, and the literature references did not provide sufficient evidence to show a nexus between the claimed invention. References Yahaya and Wu (and Blinka) continue to provide the foundation for maintaining the rejection of the amended claims.
Conclusion
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/HEIDI R KELLEY/ Supervisory Patent Examiner, Art Unit 1765
/S.M.D./
Examiner
Art Unit 1765