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 .
DETAILED ACTION
Claims 1, 2, 6 and 14 of J. Sui, US 18/030,004 (Feb. 15, 2022) are pending and under examination. Claims 1, 2, 6 and 14 are rejected.
Withdrawal Claim Objections
Objection to claim 1 on the grounds that Applicant is required to remove the claim 1 term “by means of” is withdrawn in view of Applicant’s amendment.
Withdrawal Rejections 35 U.S.C. 112(b)
Rejection of claims under 35 U.S.C. 112(b) as indefinite is withdrawn in view of Applicant’s amendments.
New Claim Rejections 35 U.S.C. 112(b)
The following is a quotation of 35 U.S.C. 112(b):
(b) CONCLUSION. — The specification shall conclude with one or more claims particularly pointing out and distinctly claiming the subject matter which the inventor or a joint inventor regards as the invention.
Pursuant to 35 U.S.C. 112(b), the claim must apprise one of ordinary skill in the art of its scope so as to provide clear warning to others as to what constitutes infringement. MPEP 2173.02(II); Solomon v. Kimberly-Clark Corp., 216 F.3d 1372, 1379, 55 USPQ2d 1279, 1283 (Fed. Cir. 2000). A claim is indefinite when it contains words or phrases whose meaning is unclear. MPEP § 2173.05(e) (citing In re Packard, 751 F.3d 1307, 1314, 110 USPQ2d 1785, 1789 (Fed. Cir. 2014)).
Unclear Antecedent Basis “a divided wall”
Claims 1, 2, 6 and 14 are rejected under 35 U.S.C. 112(b) as indefinite because independent claim 1 recites two instances of a “divided wall” as follows:
Claim 1 . . . wherein each of the first divided wall column and the second divided wall column comprises:
(a) a divided wall provided vertically inside a column shell, defining a divided wall section between an upper undivided section as a rectifying zone and a lower undivided section as a stripping zone;
(b) a divided wall section located between the rectifying zone and the stripping zone having a vertical dividing wall dividing an inner space of the divided wall section into a pre-fractionation zone at one side of the dividing wall and a main fractionation zone at the other side of the dividing wall;
. . .
and it is not clear whether the second recitation of “a vertical dividing wall” is a different “wall” from the first recitation of “a dividing wall” for the following reasons. The disclosed specification embodiment, with reference to the specification Figure, indicates that these two claim 1 instances refer to the same dividing wall. Specification at page 7. However, the plain claim 1 language indicates two different dividing walls within the same column. In view of mutually exclusive interpretations, claim 1 is unclear.
As discussed in the MPEP a lack of clarity could arise where a claim refers to "said lever" or "the lever," where the claim contains no earlier recitation or limitation of a lever and where it would be unclear as to what element the limitation was making reference. MPEP § 2173.05(e). Similarly, if two different levers are recited earlier in the claim, the recitation of "said lever" in the same or subsequent claim would be unclear where it is uncertain which of the two levers was intended. MPEP § 2173.05(e). A claim which refers to "said aluminum lever," but recites only "a lever" earlier in the claim, is indefinite because it is uncertain as to the lever to which reference is made. MPEP § 2173.05(e).
Dependent claims 2, 6 and 14 do not cure the issue. Furthermore, other instances of improper articles (i.e., “a” and/or “the”) and antecedent basis are also present in claim 1. This rejection can be obviated, for example, by amending as proposed below.
Claim 1 A continuous process for preparing substantially pure p-phenylenediamine and highly pure o-phenylenediamine from a reaction product stream by a first divided wall column a second divided wall column and at least one stage suspension-based melt crystallization system,
wherein each of the first divided wall column and the second divided wall column comprise[[s]]:
(a) a divided wall provided vertically inside [[a]] the column shell, defining a divided wall section between an upper undivided section as a rectifying zone and a lower undivided section as a stripping zone;
(b) a divided wall section located between the rectifying zone and the stripping zone having [[a]] the
. . .
As well as Applicant’s claim review to correct any other instances.
Maintained 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 set forth in Graham v. John Deere Co., 383 U.S. 1, 148 USPQ 459 (1966), that are applied for establishing a background for determining obviousness under AIA 35 U.S.C. 103(a) 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 and 14 are rejected under AIA 35 U.S.C. 103 as being unpatentable over L. Lei et al., CN 101250113B (2010) (“Lei”); L. Xinli et al, CN 105906512A (2006) (“Xinli”); H. Ling et al., 48 Industrial & Engineering Chemistry Research, 6034-6049 (2009) (“Ling”); and M. Errico et al., 87 Chemical Engineering Research and Design, 1649-1657 (2009) (“Errico”).
Claim 2 is obvious as above, in further view of R. Benzie et al., GB 1,430,366 (1976) (“Benzie”).
Claim 6 is obvious as above in further view of J. Chaty et al., An engineering study of the rotary drum crystallizer, AIChE Journal, 74-78 (1964) (“Chaty”) and M. van der Gun et al., 56 Chemical Engineering Science, 2831-2388 (2001) (“van der Gun”).
L. Lei et al., CN 101250113B (2010) (“Lei”)
An English-machine language translation (using Google Translate) is attached as the second half of reference Lei. Lei thus consists of 14 total pages (including the English-language portion). Accordingly, this Office action references Lei page numbers in the following format “xx of 14”.
Lei teaches that p-phenylenediamine is a widely used intermediate that can be used to produce dyes, pigments, hair dyes, rubber antioxidants, para-aramid, and the raw material for producing polyurethane, p-phenylenediisocyanate. Lei at page 10 of 14, [0003]. Lei teaches that usually, p-phenylenediamine is prepared by reducing p-nitroaniline after ammoniation of p-nitrochlorobenzene and in order to obtain high-purity p-phenylenediamine raw material, the p- phenylenediamine product obtained by such reduction needs to be purified and refined. Lei at page 10 of 14, [0003].
Lei teaches melt crystallization by adding p-phenylenediamine, obtained from distillation, to a crystallizer, heating to 143 °C to melt the material completely, obtain a constant temperature, and cool the melt at rate of 2-5 °C per hour to 140 °C, then slowly cool at a rate of 1-3 °C per hour, cool to 120-125 °C and keep for 5 to 12 hours, open the valve to discharge the mother liquor after crystallization, and obtain the p-phenylenediamine crystal layer 1. Lei at page 11 of 14, [0023]. Lei next teaches gradient heating of the obtained crystals (sweating) and discharging the sweating residue and obtaining a phenylenediamine crystal layer 2. Lei at page 11 of 14, [0024]. Next Lei teaches repeating the above steps 1-3 times, where the p-phenylenediamine melt obtained in the previous stage is mixed with part of the sweating liquid of the secondary melt crystallization, and the melt crystallization is repeated as the raw material of the secondary melt crystallization to obtain a product of the desired purity, thereby obtaining a p-phenylenediamine crystal layer 3. Lei at page 11 of 14, [0024].
Lei teaches that the process of rectifying (distilling) followed by melt crystallization to refine p-phenylenediamine, by controlling operating parameters, can yield 99.99-99.999% high-purity, high-quality p-phenylenediamine product. Lei at page 4, last paragraph.
In Embodiment 1, Lei teaches that phenylenediamine obtained from catalytic hydrogenation p-nitroaniline and freed of moisture and solvent, is mixed with the mother liquor of the first stage melt crystallization is distilled in a first distillation tower, at about 0.096 MPa, where low-boiling point substances and other fore-fractions are removed by vacuum distillation. Lei at page 12 of 14. The bottom liquid enters a second distillation tower, and the p-phenylenediamine is distilled out by rectification and condensed to obtain p-phenylenediamine with a purity of 99%. Lei next teaches melt crystallization of this 99% pure stream, mixed with recycles from a previous melt crystallization (1200 kg), by melt crystallization. Lei at page 12 of 14.
The Examiner summarizes Lei Embodiment 1 as follows:
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Differences between Lei at Claim 1
Lei teaches the claim 1 limitation of “by means of two withdrawn from the side-draw of the first divided wall column”.
L. Xinli et al, CN 105906512A (2006) (“Xinli”)
An English-machine language translation (using Google Translate) is attached as the second half of reference Xinli. Xinli thus consists of 18 total pages (including the English-language portion). Accordingly, this Office action references Xinli page numbers in the following format “xx of 18”.
Xinli teaches that phenylenediamine is an important chemical intermediate, and is divided into three isomers: m-phenylenediamine, o-phenylenediamine and p-phenylenediamine, and because the boiling point difference between the phenylenediamine isomers distillation separation can be difficult. Xinli at page 13 of 18. Xinli teaches
[0007] a single tower separation device for phenylenediamine isomers, wherein the separation device comprises a main distillation tower, a condenser. a reboiler, a crystallizer and a mother liquor buffer tank, wherein a plurality of trays are provided in the main distillation tower, a mixed diamine feed pipe is provided in the middle portion of the main distillation tower. The bottom of the main distillation tower is connected to a m-phenylenediamine discharge pipe via a circulation pump, the m-phenylenediamine discharge pipe is provided with circulation pipe, the circulation pipe is connected to the bottom of the main distillation tower via a reboiler, the top of the main distillation tower is provided with a tower top gas phase pipe, the tower top gas phase pipe is connected to an o-phenylenediamine discharge pipe via a condenser, the upper portion of the main distillation tower is provided with an intermediate extraction pipe, the intermediate extraction pipe is connected to the crystallizer, the bottom of the crystallizer is provided with a p-phenylenediamine discharge pipe and a mother liquor circulation pipe, and the mother liquor circulation pipe is connected to the main distillation tower via a mother liquor buffer tank and a mother liquor delivery pump.
Xinli at page 13 of 18 (emphasis added). Xinli teaches Fig. 1. Xinli at page 15 of 18, 1st paragraph. Xinli teaches that Figure 1 is a simplified structural diagram of the apparatus of the present invention, where 1 Main finishing tower, 2 Condenser, 3 Reboiler, 4 Circulation pump, 5 Crystallizer, 6 Mother liquor buffer tank, 7 Mother liquor delivery pump, 8 Mixed diamine feed pipe, 9 Tower top gas phase pipe, 10 Vacuum pump, 11 Reflux pipe, 12 o-phenylenediamine discharge pipe, 13 Tower bottom circulation tank, 14 m-phenylenediamine discharge pipe, 15 Circulation pump outlet pipe, 16 Reboiler discharge pipe, 17 Intermediate extraction pipe, 18 Mother liquor discharge pipe, 19 p-phenylenediamine discharge pipe, 20 Mother liquor pump inlet pipe, 21 Mother liquor return pipe. Xinli at page 15 of 18 (referring to Fig. 1).
Xinli further teaches that the p-phenylenediamine discharged from tower is subject to a melt crystallization and recycle steps in the following passage.
the p-phenylenediamine liquid extracted from the middle extraction pipe 17 at the top of the rectifying tower 1 is passed into the crystallizer 5 for crystallization operation. The crystallization temperature of the crystallizer 5 is 50-110° C. The crystallization cooling rate of the crystallizer 5 is 1-10° C./hour. After the crystallization mother liquor mainly containing o-phenylenediamine and a small amount of m-phenylenediamine and p-phenylenediamine enters the mother liquor surge tank 6 for buffering, it is returned to the main rectifying tower 1 through the mother liquor delivery pump 7. Then, the crystallizer 5 is subjected to a temperature-raising and sweating operation. The sweating temperature-raising rate of the crystallizer 5 is 1-10° C/hour. After heating and curing, the product p-phenylenediamine is obtained and extracted from the p-phenylenediamine discharge pipe 19. The liquid rich in p-phenylenediamine is extracted from the top of the rectifying tower 1. The high-quality p-phenylenediamine product is isolated by crystallization technology. The crystallization mother liquor returns to the main rectifying tower 1.
Xinli at page 16 of 18 (emphasis added). The above Xinli crystallization is clearly, per claim 1 a “suspension-based melt crystallization” because no solvent is present.
Differences between Xinli at Claim 1
Xinli teaches purification of phenylenediamine by distillation coupled with melt crystallization. Xinli differs from claim 1 in that Xinli teaches a single distillation tower/column that is not a “divided wall column”, whereas claim 1 requires two operatively coupled divided wall columns.
H. Ling et al., 48 Industrial & Engineering Chemistry Research, 6034-6049 (2009) (“Ling”)
Ling teaches that the divided-wall column is a practical way to implement the topology of the Petlyuk column that features two columns (a prefractionator into which the feed is introduced and a main column from which a sidestream product is withdrawn) with interconnected vapor and liquid streams arising from a single reboiler and a single condenser. Ling at Abstract. Ling teaches that the divided-wall column splits the middle section of a single column into two sections by inserting a vertical wall in the vessel at an appropriate position, not necessarily at the diameter. Ling at page 6034, col. 1.
Ling teaches that in operation of a divided-wall column, feed is introduced into the prefractionator side of the wall and a sidestream is removed from the other side. Ling at page 6034, col. 1. Ling teaches that the sidestream (withdrawal point) is mostly the intermediate boiling component of the ternary mixture, the lightest component goes overhead in the distillate product, and the heaviest component goes out in the bottoms product. Id. And at the bottom of the divided-wall section, the vapor is split between the two sides in proportion to the cross-sectional area of each side, which is fixed by the physical location of the wall. Id. And at the top of the divided-wall section, the liquid coming down from the rectifying section can be split between the two sides of the wall by using a total liquid trap-out tray and sending part of the total liquid to the prefractionator side (LP) and the rest to the sidestream side. Id. at page 6034, col. 2. Ling teaches that Figure 1 gives the optimum economic design of the divided-wall column based on minimizing total annual cost, which includes both energy and capital costs. Ling at page 6038, col. 1 (referring to Fig. 1 at page 6035). Ling Fig. 1 comports with instant specification Fig. 1. Ling teaches that the number of trays (horizontal perforated plates) in the four column sections, the location of the feed inlet and sidestream withdrawal, the vapor split, and the liquid split can be varied to find the minimum total annual cost (TAC) design that produces the specified product purities. Ling at page 6038, col. 1.
M. Errico et al., 87 Chemical Engineering Research and Design, 1649-1657 (2009) (“Errico”)
Similar to Ling, Errico teaches that the divided wall column (DWC) to separate three components in a single distillation tower is receiving increasing interest in industrial applications due to the potentiality in energy and capital cost savings. Errico at Abstract. Errico teaches that the divided wall column is realized including the prefractionator in the main column and the resulting configuration, reported in Errico Fig. 1b, consists of a single shell column with a partitioning wall that separates the feed location from the side draw of the middle boiling component, and where the liquid reflux from the condenser and the vapour from the reboiler are splitted through on the two sides of the wall. Errico at page 1650, col. 2.
Errico teaches that the divided wall column (DWC) to separate three components in a single distillation tower is receiving increasing interest in industrial applications due to the potentiality in energy and capital cost savings. Errico at Abstract. Errico teaches that significant energy reduction was achieved with DWC structures, while the saving in capital costs is lower than the 30% value reported in most of the specialized literature. Id.
R. Benzie et al., GB 1,430,366 (1976) (“Benzie”)
Benzie is cited here with respect to instant claim 2. Benzie teaches synthesis of phenylenediamine by reacting nitrous acid with aniline to give a mixture of diazoaminobenzene and aniline, treating the said mixture so as to isomerize the diazoaminobenzene therein to aminoazobenzene, reduction with hydrogen in the presence of a hydrogenation catalyst to give a mixture of p-phenylenediamine and
aniline, and separating the p-phenylenediamine. Benzie at page 1, col. 1, lines 15-33. Benzie teaches that o- phenylenediamine is a side product. Benzie at page 2, col. 2, lines 95-100.
With regard to the process of Benzie, the current specification teaches that:
However, during the diazotization of aniline with a nitrogen oxide-containing gas and the rearrangement of the 1,3-diphenyltriazene, side-reactions leading to the formation of polynuclear (chiefly binuclear) by-products such as diphenylamine and aminobiphenyls, particularly 2- aminobiphenyl, may occur. Also, yield losses to the undesired o-aminoazobenzene isomer may result. As is described in British Pat. No. 1,430,366, several% by weight of o-phenylenediamine as a by-product is unavoidably contained in the final reaction product. The said final reaction product which is essentially free of aniline can contain, for example, 70 to 85% by weight of p-phenylenediamine, 4 to 15% by weight of o-phenylenediamine, 0 to 15% by weight of aminobiphenyls, 0 to 8% by weight of diphenylamine, 0 to 2% by weight of aniline, 0 to 2% by weight of biphenyl and 0 to 2% by weight of tars.
Specification at pages 1-2 (emphasis added). Thus, the specification teaches that the reaction product of Benzie, is the same reaction product of instant claim 2.
Obviousness Rational
Claim 1 requires process steps (i)-(iv)
1. . . . . wherein the continuous process comprises:
(i) continuously introducing the reaction product stream into an inlet of the pre-fractionation zone of the first divided-wall column;
(ii) withdrawing a concentrated p-phenylenediamine product stream from the side-draw outlet of the first divided-wall column and subsequently subjecting the withdrawn stream to a further purification step comprising at least one stage of suspension-based melt crystallization to obtain a substantially pure p-phenylenediamine product stream;
(iii) feeding the overhead product stream from the fist divided-wall column to an inlet of the pre-fractionating zone of the second divided-wall column; and
(iv) obtaining a highly pure o-phenylenediamine product stream as a side draw from the main fractionation zone of the second divided wall column.
It is first noted that the “continuous process” of claim 1 as amended, does not incorporate the specification embodiment where phenylenediamine flows from the second divided wall column back to the first divided wall column.1 In other words claim 1 does not require that steps (i)/(ii) are connected with steps (iii)/(iv) as part of the continuous process. Rather, per claim 1 step (ii), a side stream is withdrawn from the first divided wall column and subject to melt recrystallization to a give first portion of purified p-phenylenediamine; and, per claim 1 steps (iii) and (iv) a top stream is removed from the first divided wall column and subject to purification in a second divided wall column and to give a second portion of purified p-phenylenediamine.
Claim 1 is obvious because one of ordinary skill is motivated to modify Lei’s continuous melt crystallization purification of phenylenediamine by replacing the distillation tower in Lei with a divided wall column, for example, either of the following divided wall columns:
(1) the divided wall column depicted in Ling at page 6035, Fig. 1; or
(2) the column of Xinli, modified by inserting a dividing wall,
because both Ling and Errico teach that properly optimized divided wall columns offer efficient separation and potentiality in energy and capital cost savings. To summarize this first proposed modification of Lei, one of ordinary skill is motivated to first distill the phenylenediamine stream by way of a divided wall tower and thereafter subject the distilled product to the Xinli suspension-based melt crystallization. Xinli at page 16 of 18. This meets the following claim 1 limitations:
claim 1 . . . (i) continuously introducing the reaction product stream into an inlet of the pre-fractionation zone of the first divided-wall column;
(ii) withdrawing a concentrated p-phenylenediamine product stream from the side-draw outlet of the first divided-wall column and subsequently subjecting the withdrawn stream to a further purification step comprising at least one stage of suspension-based melt crystallization to obtain a substantially pure p-phenylenediamine product stream;
One of ordinary skill is further motivated to, as the same time, collect a top stream from the first divided wall column which will comprise p-phenylenediamine enriched in the lower-boiling o-phenylenediamine.2 One of ordinary is then motivated to subject this o/p-phenylenediamine stream to a second divided wall distillation in order to improve the recovery of p-phenylenediamine.
This meets the following additional claim 1 limitations:
(iii) feeding the overhead product stream from the fist divided-wall column to an inlet of the pre-fractionating zone of the second divided-wall column; and
(iv) obtaining a highly pure o-phenylenediamine product stream as a side draw from the main fractionation zone of the second divided wall column.
The claim 1 limitation of “wherein the concentrated p-phenylenediamine product stream is withdrawn from the side-draw of the first divided wall column” is met because both the Ling and Xinli columns comprise a side outlet for withdrawal of the product stream. See Ling at page 6035, Fig. 1; Xinli at page 9 of 18, Fig. 1. In regard to this claim 1 side-draw limitation, Ling teaches that:
One practical implementation of the Petlyuk column is the divided-wall column that splits the middle section of a single column into two sections by inserting a vertical wall in the vessel at an appropriate position, not necessarily at the diameter. Feed is introduced into the prefractionator side of the wall. A sidestream is removed from the other side.
Ling at page 6034, col. 1. Each and every limitation of claim 1 is met and is therefore obvious over the cited art.
Claim 2 is obvious as above, in further view of Benzie, for the following reasons. One of ordinary skill is motivated to purify the phenylenediamine product stream of Benzie as proposed above. As noted above, the instant specification teaches that Benzie’s phenylenediamine product stream meets the purity percentages of claim 2. Specification at pages 1-2. Once a reference teaching product appearing to be substantially identical is made the basis of a rejection, and the examiner presents evidence or reasoning to show inherency, the burden of production shifts to the applicant. MPEP § 2112(V) (citing In re Best, 562 F.2d 1252, 1255, 195 USPQ 430, 433-34 (CCPA 1977). It is appropriate to look to the instant specification for evidence that a claimed feature is inherent in the prior art. See, MPEP § 2112.02(I) (discussing Ex parte Novitski, 26 USPQ2d 1389 (Bd. Pat. App. & Inter. 1993)
Claim 6 is obvious because one of ordinary skill is motivated employ a drum crystallizer, which as taught by Chaty, employs a scraper blade, which removes the crystal deposit in a liquid free, convenient form. J. Chaty et al., An engineering study of the rotary drum crystallizer, AIChE Journal, 74-78 (1964) (“Chaty”). One of ordinary skill further is motivated to feed the crystallizer suspension, obtained by way of the Chaty drum crystallizer, into a wash column to remove the mother liquor by filtration in further view of M. van der Gun et al., 56 Chemical Engineering Science, 2831-2388 (2001) (“van der Gun”) Reference van der Gun teaches that melt crystallization is a commonly used technique to obtain high-purity products and teaches a continuous process that combines a solidification step and a purification step (Fig. 1), where the produced solids, of the same composition as the feed, are purified in a gravity wash column. van der Gun at page 2381, col. 1. Reference van der Gun teaches purification by way of a gravity wash column can be explained using Fig. 2. van der Gun at page 2382. One of ordinary skill thereby meets each and every limitation of claim 6.
Claim 14 is obvious because Ling (directed to divided wall columns) teaches that the number of trays (where “trays” are known in the art of divided wall columns as horizontal perforated plates) in the four column sections, the location of the feed inlet and side-stream withdrawal, the vapor split, and the liquid split can be varied to find the minimum total annual cost (TAC) design that produces the specified product purities. Ling at page 6038, col. 1. The Trays taught by Ling meet the claim 14 limitation of “random packings, structured packings and any combinations thereof’.
Applicant’s Argument
Applicant argues that Lei discloses that the p-phenylenediamine stream enriched at the top of the second conventional distillation column is withdrawn and subsequently purified by melt crystallization. Lei describes the use of sweating steps, which strongly indicates that the method is implemented as layer crystallization or falling-film crystallization, since suspension-based melt crystallization does not employ sweating. However, p-phenylenediamine has a melting point of approximately 144 °C, and each sweating stage unavoidably subjects the material to elevated temperatures for extended periods. Reply at paragraph bridging pages 8-9.
In response, both Lei and Xinli teach, per claim 1, “suspension-based melt crystallization” because a heated melt (i.e., solventless phenylenediamine) and suspension are involved in Lei and Xinli and in both processes, crystals formed are kept in suspension and are allowed to grow by sub-cooled temperature.3 Sweating can be used with both suspension and layer melt crystallization. See e.g., M. Matsuoka et al., 166 Journal of Crystal Growth, 1035-1039 (1996) (stating in the Abstract “[t]hese two facts lead to the conclusion that the overall efficiency for the purification by sweating is higher for the suspension crystallization than the layer one”). The specification gives no details or discussion of what a “suspension-based melt crystallization” is or how it differs from a layer crystallization.
Applicant further argues that the act of removing the concentrated p-phenylenediamine from the second distillation column implies that the phenylenediamines first undergo evaporation in the initial distillation column, then condensation in the downstream condenser, and subsequently re-evaporation in the second distillation column. This sequence of repeated phase changes exposes p-phenylenediamine to elevated temperatures over an extended overall residence time. Because phenylenediamines are thermally sensitive, increasing their cumulative residence time across multiple high-temperature unit operations such as two distillation columns followed by multistage melt crystallization substantially elevates the extent of thermal degradation and consequently promotes tar formation. Reply page 9.
In response, this appears to be mere attorney argument because no evidence/references are cited contraindicating distillation of phenylenediamine. MPEP § 2145(I). Rather, the cited art suggests distillation for purification of phenylenediamine.
Applicant argues that that Xinli's disclosure employs a single conventional distillation column to separate the close boiling mixture of phenylenediamine isomers, where the p-phenylenediamine side-draw for is positioned unfavorably above the feed inlet, such that Xinli's process must employ a very high reflux ratio and elevated temperatures, which can promote tar formation. Reply at page 10.
In response, the proposed practice of the cited art employes a divided wall column. Ling teaches that the sidestream (withdrawal point) is mostly the intermediate boiling component of the ternary mixture, the lightest component goes overhead in the distillate product, and the heaviest component goes out in the bottoms product. Ling at page 6034, col. 1. And at the bottom of the divided-wall section, the vapor is split between the two sides in proportion to the cross-sectional area of each side, which is fixed by the physical location of the wall. Id. And at the top of the divided-wall section, the liquid coming down from the rectifying section can be split between the two sides of the wall by using a total liquid trap-out tray and sending part of the total liquid to the prefractionator side (LP) and the rest to the sidestream side. Id. at page 6034, col. 2. Ling teaches that Figure 1 gives the optimum economic design of the divided-wall column based on minimizing total annual cost, which includes both energy and capital costs. Ling at page 6038, col. 1 (referring to Fig. 1 at page 6035). In view of Ling, one of ordinary skill is motivated to position the p-phenylenediamine withdrawal at the point of the divided wall column having a the most favorable reflux ratio for p-phenylenediamine.
Applicant argues that the concept of a divided-wall distillation column (DWC) has existed for decades but despite long-standing academic interest, industrial adoption of DWCs has remained very limited: as of 2019, “only slightly more than 300 industrial DWC units had been implemented worldwide”, a negligible fraction compared with the hundreds of thousands of conventional distillation columns in operation globally. Reply at page 11 (citing G. Lukač et al., 147 Chemical Engineering Research and Design, 367-377 (2019) (“Lukač”)). Applicant argues that this demonstrates that DWCs are not broadly applicable to all separation problems; rather, their practical use is restricted to a relatively small subset of systems that satisfy strict thermodynamic and operational criteria. Id.
This argument is not persuasive for the following reasons. First, Applicant does not cite the particular portion of Lukač relied upon. It is believed that Applicant is citing the following Lukač excerpt.
The most promising in this respect is the Dividing Wall Column (DWC) technology, which, proven in more than 300 applications worldwide, uses approximately 30% less energy, capital investment and plot area com-pared with a conventional distillation arrangement.
Lukač at page 367, col. 1 (emphasis added). Lukač does state “only slightly more” as argued by Applicant. Furthermore, Lukač clearly does not teach away from the claimed divided wall column because this reference does not criticize, discredit or otherwise discourage investigation into the invention claimed. MPEP § 2145(X)(D)(1).4 Rather, Lukač motivates one of ordinary skill in the art to employ divided wall columns in view capital savings.
Applicant argues that person of ordinary skill in the art could not reasonably infer from Ling or Errico that DWCs are applicable to this specific class of aromatic diamines, because successful implementation of a DWC depends on highly specific parameters particular to phenylenediamine. Reply at pages 11-12.
In response, Ling or Errico provide sufficient motivation to explore divided wall columns in the purification of phenylenediamine. For example, Errico teaches that the divided wall column (DWC) to separate three components in a single distillation tower is receiving increasing interest in industrial applications due to the potentiality in energy and capital cost savings. Errico at Abstract. Errico teaches that significant energy reduction was achieved with DWC structures, while the saving in capital costs is lower than the 30% value reported in most of the specialized literature. Id.
Applicant’s additional arguments are addressed above.
Conclusion
Applicant's amendment necessitated the new ground(s) of rejection presented in this Office action. Accordingly, THIS ACTION IS MADE FINAL. See MPEP § 706.07(a). Applicant is reminded of the extension of time policy as set forth in 37 CFR 1.136(a).
A shortened statutory period for reply to this final action is set to expire THREE MONTHS from the mailing date of this action. In the event a first reply is filed within TWO MONTHS of the mailing date of this final action and the advisory action is not mailed until after the end of the THREE-MONTH shortened statutory period, then the shortened statutory period will expire on the date the advisory action is mailed, and any nonprovisional extension fee (37 CFR 1.17(a)) pursuant to 37 CFR 1.136(a) will be calculated from the mailing date of the advisory action. In no event, however, will the statutory period for reply expire later than SIX MONTHS from the mailing date of this final action.
Any inquiry concerning this communication or earlier communications from the examiner should be directed to ALEXANDER R PAGANO whose telephone number is (571)270-3764. The examiner can normally be reached 8:00 AM through 5:00 PM.
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ALEXANDER R. PAGANO
Examiner
Art Unit 1692
/ALEXANDER R PAGANO/Primary Examiner, Art Unit 1692
1 The specification teaches the following embodiment of tandem continuous operation of the first and second divided wall columns, which is not incorporated into claim 1.
A multi-component feed stream 10 is then separated by the mass transfer within the four operating zones into three product streams, i.e. an overhead product stream 33, a bottoms product stream 45 and a side-draw product stream 34. The said reaction product stream combining with stream 46 is continuously fed through feed stream 2 into the pre-fractionation zone 19 of the first divided wall column . . . and the purge stream 25 discharged from the crystallization system 23 is recycled to stream 46.
Specification at pages 7-8.
2 The boiling points of p-phenylenediamine is approximately 267 °C, while the boiling point of o-phenylenediamine is about 256-258 °C. See, m-, o-, and p-Phenylenediamine, Organic Methods Evaluation Branch OSHA Analytical Laboratory Salt Lake City, Utah (1991).
3 Melt crystallization can be either a suspension or layer-based. M. Kapembwa, Heat and Mass Transfer Effects of Ice Growth Mechanisms in Water and Aqueous Solutions (2013) (see page 11). In layered crystallization processes, crystals grow on a cooled surface and the crystalline product is separated from its residue melt by mechanical means. Id. In suspension-based melt crystallization, crystals formed are kept in suspension and are allowed to grow by sub-cooled temperature of the mother liquor. Id.
4 A reference teaches away when a person of ordinary skill, upon reading the reference, would be discouraged from following the path set out in the reference, or would be led in a direction divergent from the path that was taken. UCB, Inc. v. Actavis Labs. UT, Inc., 65 F.4th 679, 692 (Fed. Cir. 2023) (citation omitted); MPEP § 2145(X)(D)(1). By contrast, a reference does not teach away if it merely expresses a general preference for an alternative invention but does not criticize, discredit or otherwise discourage investigation into the invention claimed. Id.