Patent Grant
10011545
This application is a U.S. national stage entry under 35 U.S.C. § 371 of International Application No. PCT/EP2015/057655 filed Apr. 9, 2015, which claims priority to European application No. 14164336.1, filed on Apr. 11, 2014. The entire contents of these applications are explicitly incorporated herein by this reference.
The present invention relates to a process for the manufacture of α-iodoperfluoroalkanes and α,ω-diiodoperfluoroalkanes.
α-Iodoperfluoroalkanes and α,ω-diiodoperfluoroalkanes (herein after otherwise respectively referred to as “I-telomers” and “I2-telomers”) are useful reagents or intermediates in a variety of applications.
α-Iodoperfluoroalkanes having general formula F(CF2)nI, wherein n is typically an integer higher than 3, can be used, for example, as intermediates for the manufacture of surfactants, pesticides, electronic materials or pharmaceuticals.
α,ω-Diiodoperfluoroalkanes having formula I(C2F4)nI (with n>1) such as, for example, 1,4-diiodoperfluorobutane (C4F8I2) and 1,6-diiodoperfluorohexane (C6F12I2), can be used as chain-transfer agents in polymerization reactions, as intermediates for the manufacture of other chemicals, including bis-olefins, diacids, polymers or for the manufacture of coatings.
α-Iodoperfluoroalkanes are typically synthesized by means of a telomerization reaction of TFE with a α-iodoperfluoroalkane, preferably CF3I or CF3CF2I. Usually, the most common and industrially convenient way to initiate the reaction is the heating of the starting reactants, the heating temperature being proportional to the length of the desired telomers. The reaction can be carried out in the liquid phase at a temperature of at least 150° C. under pressure. Alternatively, the reaction can be carried out at a temperature as high as 450° C. either at atmospheric pressure, thereby providing only a monoaddition I-telomer in a single step of the reaction, or under pressure, thereby giving rise to a broad distribution of telomers. Methods for the synthesis of I-telomers are disclosed, for instance, in U.S. Pat. No. 3,404,189 (FMC CORP) Jan. 10, 1968, U.S. Pat. No. 5,268,516 U.S. Pat. No. 5,268,516 (ATOCHEM ELF SA) and WO 99/19248 (DU PONT) Apr. 22, 1999.
α,ω-Diiodoperfluoroalkanes are typically synthesized by means of a process comprising the reaction of tetrafluoroethylene (TFE) with iodine in the presence of different initiators, at different temperatures. Also in this case, on an industrial scale it is preferred to initiate the reaction by heating the reactants. TFE promptly reacts with iodine to provide C2F4I2, which is in equilibrium with TFE and iodine; C2F4I2 further reacts with TFE to provide higher-length telomers.
JP S51133206 (ASAHI GLASS CO LTD) Nov. 18, 1976 discloses a process for the preparation of I2-telomers of formula I(C2F4)nI (n=2-4) by thermal decomposition of C2F4I2. The telomerization reaction of TFE with C2F4I2 is disclosed in TORTELLI, et al. Telomerization of tetrafluoroethylene and hexafluoropropene: synthesis of diiodoperfluoroalkanes. J. Fluorine Chem. 1990, vol. 47, p. 199-210.
Example 29 of WO 98/34967 A (THE UNIVERSITY OF NORTH CAROLINA) Aug. 13, 1998 teaches to synthesize a low molecular weight polymer or oligomer [namely CF3(C2F4)nI or F(C2F4)nI] by irradiation of TFE with a UV lamp and heating at 36° C. in the presence of carbon dioxide and of a chain transfer agent such as CF3I or IF.
The main problem in the synthesis of I-telomers and I2-telomers is the handling of TFE, which is flammable and explosive; flammability and explosivity increase with temperature and pressure. Therefore, in the course of the synthesis, it is necessary to properly control temperature and pressure in order not to go beyond critical values. Normally, if temperature is increased, pressure values must be controlled in such a way as not to go beyond 400 kPa at most. This has a negative impact on the productivity of the process. Indeed, under such conditions, less TFE is available in the liquid phase to react with I2, which decreases the reaction speed. In principle, speed could be increased by increasing the TFE pressure or the temperature, but this is not possible due to safety concerns and to the occurrence of undesired side-reactions (i.e. formation of perfluorocyclobutane, TFE polymerization, formation of perfluoroalkanes and I2). Furthermore, the Applicant has observed that reaction mixtures containing TFE and I2, which form C2F4I2 and higher length telomers, are even more flammable and explosive than TFE alone. This is quite surprising, as it was expected that I2 present in such mixtures as a result of dissociation of C2F4I2 and higher length telomers would act as a radical scavenger, thereby increasing the stability of the mixture. The same increased risk of flammability and explosivity is also associated to reaction mixtures containing TFE and CF3CF2I used in the synthesis of α-iodoperfluoroalkanes, since they also give rise to a certain amount of I2, which is known to react with TFE giving rise to C2F4I2.
It is also well known (for example from FERRERO, Fabio, et al. Analysis of the self-heating process of tetrafluoroethylene in a 100-dm3-reactor. Journal of Loss Prevention in the Process Industries. 2012, vol. 25, no. 6, p. 1010-1017.) that a further major concern is represented by the MITD (minimum ignition temperature decomposition) of TFE which decreases by increasing pressure (it decreases from 260° C. at 500 kPa to 230° C. at 1,000 kPa).
EP 702666 A (DU PONT) discloses single-phase, liquid mixtures of TFE and CO2 which are said to be characterised by reduced explosivity. This document focuses on the storage and transport of the mixtures and discloses only in broad terms that TFE/CO2 mixtures can be used directly in TFE polymerization processes or as a diluent/heat sink in chemical reactions involving TFE. However, this document does not suggest any stabilizing effect of CO2 on other systems other than TFE.
There is therefore the need to provide a process for the manufacture of α-iodoperfluoroalkanes and α,ω-diiodoperfluoroalkanes, said process having high productivity and, at the same time, increased safety.
An additional drawback encountered in the manufacture of I-telomers and I 2-telomers, e.g. C4F9I, C4F8I2, C6F13I and C6F12I2, lies in the formation of an undesired side-product, perfluorocyclobutane (cy-C4F8), an inert gas having a boiling point of 6° C. The presence of this side-product in the reactor decreases the reaction speed. In order to overcome this drawback, it is necessary to purge the reactor, so as to remove cy-C4F8, and add further TFE. However, by doing this, not only cy-C4F8 is discharged from the reactor, but also TFE.
JP S53144507 (ASAHI GLASS CO LTD) discloses the preparation of 1,4-diiodo perfluorobutane by thermal decomposition of C2F4I2 in the presence of I2 and an inert gas. The inert gas has the effect of reducing the amount of cy-C4F8 formed in the course of the process. The sole inert gas mentioned in this document is nitrogen.
It would thus be desirable to provide a further, safe process for the manufacture of α-iodoperfluoroalkanes and α,ω-diiodoperfluoroalkanes also allowing to keep to a minimum the amount of cy-C4F8 formed in the reaction. It would also be desirable to provide a process that allows achieving a high productivity of telomers, in particular those having a low molecular weight.
The applicant has now found out that α-iodoperfluoroalkanes and α,ω-diiodoperfluoroalkanes of general formula:
A(C2F4)nI, (I)
wherein:
A is selected from F, CF3 and I and
n is an integer equal to or higher than 1, with the proviso that, when A is F,
n is an integer higher than 1
can be conveniently manufactured by means of a process (or “method”) which comprises heating a mixture [mixture (M1)] containing:
It has indeed been found out that the heating of mixture (M1) at a temperature equal to or higher than 130° C. in the presence of CO2 in an amount of at least 18% vol, preferably of at least 20% vol, provides advantages in terms of safety, because, in case of accidental ignition of the gas phase, there is a relevant mitigation of the maximum pressure reached in the reactor.
It has also been found out that the heating of mixture (M1) at a temperature equal to or higher than 130° C. in the presence of CO2 in an amount of at least 27% provides an additional advantage, since the mixture of reaction products obtained from mixture (M1) in the course of the process is not explosive.
Preferably, in formula (I) above, A is selected from F and I and n is an integer higher than 1. More preferably, n ranges from 2 to 4; this range is preferred in all preferred embodiments indicated below.
For the sake of clarity, when ranges are indicated in the present description, range ends are always included.
Thus, in a first embodiment, the process allows obtaining α-iodoperfluoroalkanes of formula (Ia):
A(C2F4)nI (Ia)
wherein A is F or CF3 and n is an integer equal to or higher than 1, with the proviso that, when A is F, n is an integer higher than 1. Preferably, the process allows obtaining α-iodoperfluoroalkanes (Ia*) wherein A is F and n is an integer higher than 1.
In a second embodiment, the process allows obtaining
α,ω-iodoperfluoroalkanes of formula:
I(C2F4)nI (Ib)
wherein n is an integer equal to or higher than 1, preferably higher than 1.
Manufacture of α-iodoperfluoroalkanes
The manufacture of α-iodoperfluoroalkanes of formula (Ia) as defined above according to the present invention is typically carried out at temperatures ranging from 130° C. to 500° C., the two following embodiments being preferred.
Process (A)
According to a first preferred embodiment [herein after “process (A)”], the manufacture of α-iodoperfluoroalkanes of formula (Ia) is carried out by heating a mixture (Mia) containing CF3I or CF3CF2I, TFE and CO2 at a temperature ranging from 170° C. to 250° C., preferably from 190° C. to 220° C., while feeding TFE and CO2 in the course of the process. Typically, CF3I or CF3CF2I are charged in the reactor, the temperature is raised up to 170° C.-250° C., preferably up to 190° C.-220° C., and TFE and CO2 are fed in the reactor in the course of the process.
CF3I and CF3CF2I can be manufactured according to methods known in the art, for example as disclosed in U.S. Pat. No. 3,523,140 (MONTEDISON S.P.A.) Aug. 4, 1970, U.S. Pat. No. 3,644,544 (MONTEDISON S.P.A.) Feb. 22, 1972, U.S. Pat. No. 4,922,041 (KALI CHEMIE AG) May 1, 1990, and U.S. Pat. No. 7,071,367 (HONEYWELL INT INC) Jun. 15, 2006.
Typically, TFE is added in a molar amount ranging from 0.5 to 3.0 with respect to CF3I or CF3CF2I.
The process is typically carried out for a time ranging from 1 to 12 hours, preferably from 1 to 24 hours, more preferably from 1 to 48 hours.
In any case, the amount of TFE and the reaction time will be adjusted by the skilled person according to the length of the desired telomer; the longer the reaction time and the higher the TFE amount, the higher the length of the desired telomer. The formation of the desired telomer can be monitored on withdrawn samples according to known methods.
The amount of CO2 is of at least 18%, preferably of at least 20%, more preferably of at least 27% with respect to the gas phase.
In the course of the process, the pressure in the reactor is monitored and is not allowed to go beyond 2,500 kPa by purging the reactor. Purging the reactor allows removing any cy-C4F8 formed in the course of the reaction.
Process (B)
According to a second preferred embodiment [herein after “process (B)”], the manufacture of α-iodoperfluoroalkanes of formula (Ia) is carried out by heating a mixture (M1a) containing CF3I or CF3CF2I, TFE and CO2 at a temperature ranging from 300° C. to 500° C., preferably from 350° C. to 450° C. Typically, CF3I or CF3CF2I are pumped in the reactor at temperature ranging from 300° C. to 500° C., preferably from 350° C. to 450° C., while TFE and CO2 are fed in the reactor in the course of the process.
Typically, TFE is added in a molar amount ranging from 0.5 to 3, more preferably from 0.5 to 1 with respect to CF3I or CF3CF2I. Also in this case, the amount of TFE and the reaction time will be adjusted by the skilled person according to the length of the desired telomer.
The amount of CO2 is of at least 18%, preferably of at least 20%, more preferably of at least 27% with respect to the gas phase.
In the course of the process, the pressure in the reactor is monitored and typically kept within a range of 100 kPa and 1,000 kPa.
Usually, both in process (A) and (B), one or more α-iodoperfluoroalkanes (Ia)—typically C4F9I and/or C6F13I in the manufacture of α-iodoperfluoroalkanes (Ia*)—is/are obtained as a mixture (M2a) with unreacted CF3I or CF3OF2I, TFE and with any C2F4I2 and I2 possibly formed in the course of the reaction. Mixture (M2a) may further contain cy-C4F8 and/or dimeric perfluoroalkanes. The one or more α-iodoperfluoroalkanes of formula (Ia) or (Ia*) can be isolated by fractionation techniques according to methods known in the art.
Manufacture of α,ω-iodoperfluoroalkanes
The manufacture of a α,ω-iodoperfluoroalkane of formula:
I(C2F4)nI (Ib)
wherein n is 1
(1,2-diiodotetrafluoroethane)
according to the present invention is typically carried out by contacting I2 with TFE and heating at a temperature ranging from 130° C. to 170° C. in the presence of an amount of CO2 of at least 18%, preferably of at least 20%, more preferably of at least 27% with respect to the gas phase.
The reaction is typically carried out for a time ranging from 1 hr to 6 hrs, preferably from 1 hr to 4 hrs, more preferably from 1 hr to 2 hrs. TFE and I2 are typically used in a molar ratio of about 1:1.
The manufacture of α,ω-iodoperfluoroalkanes of formula:
I(C2F4)nI (Ib)
wherein n is an integer higher than 1
according to the invention is typically carried out according to the two following embodiments.
In a first embodiment [herein after “process (C)”], a mixture (M1b) comprising C2F4I2, TFE and CO2 is heated to a temperature ranging from 170° C. to 250° C., preferably of 200° C., while feeding TFE and CO2 in the course of the process. Typically, C2F4I2 is fed in the reactor, heated to 170° C.-250° C., preferably at 200° C., and TFE and CO2 are fed in the reactor in the course of the process.
In a second embodiment [herein after “process (D)”], the heating of mixture (M1b) is carried out at a temperature in the range of 170° C.-280° C. in the presence of CO2, without feeding TFE in the course of the process.
Mixture (M1b) is typically prepared by contacting TFE with I2 in the presence of CO2, followed by heating at a temperature of 130° C., to provide a mixture [mixture (M1b)] comprising C2F4I2, TFE and I2. Mixture (M1b) can be directly subjected to the process or can be submitted to a purification step in order to reduce the amount of I2 and TFE therein contained. The purification step can be carried out according to known methods.
Process (C)
Typically, process (C) comprises the following steps:
(a1) reacting TFE with I2 in the presence of CO2 at a temperature of 130° C. to provide a mixture (M1b) of C2F4I2, TFE and I2;
(a1*) optionally purifying mixture (M1b) to reduce the amount of I2 and TFE therein contained;
(a2) heating mixture (M1b) at a temperature ranging from 170° C. to 250° C., preferably of 200° C., while feeding TFE and CO2.
Step (a1) is typically carried out for a time ranging from 1 hr to 6 hrs, preferably from 1 hr to 4 hrs, more preferably from 1 hr to 2 hrs. In step (a1), TFE and I2 are typically used in a molar ratio of about 1:1.
Step (a2) is typically carried out for a time ranging from 1 hr to 12 hrs, preferably from 1 hr to 24 hrs, more preferably from 1 hr to 48 hrs. In this step, TFE is added at a pressure ranging from 1,000 to 3,500 kPa. The reaction time and the TFE pressure will be adjusted by the person skilled in the art according to the length of the desired telomer; the longer the reaction time and the higher the TFE pressure, the higher the length of the desired telomer. The formation of the desired telomer can be monitored on withdrawn samples according to known methods.
The amount of CO2 fed in the reactor in steps (a1) and (a2) is of at least 18% vol, preferably of at least 20% vol, more preferably of at least 27% vol with respect to the gas phase of mixture (M1b).
During step (a2), the pressure in the reactor is monitored and kept at values not beyond 2,500 kPa by purging the reactor. Purging the reactor allows removing any cy-C4F8 formed in the course of the reaction.
Usually, at the end of step (a2), one or more α,ω-diiodoperfluoroalkanes of formula (I), typically C4F8I2 and/or C6F12I2, is/are obtained as a mixture [mixture (M2b)] with unreacted C2F4I2 and also with TFE and I2 formed by dissociation of C2F4I2. More typically, more α,ω-diiodoperfluoroalkanes of formula (Ib) are obtained in admixture with unreacted C2F4I2, TFE and I2. Mixture (M2b) usually contains cy-C4F8 as by-product. The one or more α,ω-diiodoperfluoroalkane of formula (Ib) can thus be isolated by submitting mixture (M2b) to a purification step. This purification step can be carried out according to known methods, for example as disclosed in JP S51133206 (ASAHI GLASS CO LTD) Nov. 18, 1976.
Process (D)
Process (D) typically comprises the following steps:
(b1) reacting TFE with I2 in the presence of CO2 at a temperature of 130° C. to provide a mixture (M1b) of C2F4I2, TFE and I2;
(b1*) optionally purifying mixture (M1b) to reduce the amount of I2 and TFE therein contained;
(b2) heating mixture (M1b) at a temperature ranging from 170° C. to 280° C., preferably from 200° C. to 250° C., more preferably from 230° C. to 250° C. in the presence of CO2, without feeding TFE.
The reaction time and reagent amounts to be used in step (b1) are the same as in step (a1).
Step (b2) is typically carried out for a time ranging from 1.5 hr to 24 hrs.
The amount of CO2 fed in the reactor in steps (b1) and (b2) is of at least 18% vol, preferably of at least 20% vol, more preferably of at least 27% vol with respect to the gas phase of mixture (M1b).
Process (D) may advantageously comprise an additional step (b2*) which comprises reducing the temperature to 130° C. and adding TFE, typically in an amount ranging from 10% to 25% wt with respect to the amount of C2F4I2 in mixture (M1b) before step (b2), in order to quench I2 formed in the reaction.
Similarly to step (a2), at the end of step (b2) or (b2*), one or more α,ω-diiodoperfluoroalkanes of formula (Ib), typically C4F8I2 and/or C6F12I2, is/are obtained as a mixture [mixture (M2b)] with unreacted C2F4I2 and also with TFE and I2 formed by dissociation of C2F4I2. More typically, more α,ω-diiodoperfluoroalkanes of formula (Ib) are obtained in admixture with unreacted C2F4I2 and also with TFE and I2 in equilibrium with C2F4I2. Mixture (M2b) may also contain cy-C4F8 as by-product. The one or more α,ω-diiodoperfluoroalkane of formula (Ib) can be thus isolated by submitting mixture (M2b) to a purification step. This purification step can be carried out according to known methods, for example as disclosed in JP S51133206 (ASAHI GLASS CO LTD) Nov. 18, 1976.
Product fractions obtained from the purification step that contain C2F4I2 and higher length telomers can be conveniently recovered and be re-cycled to steps (a2) or (b2) of process (C) or (D) respectively; thus, such fractions can be used as alternatives or in addition to a mixture (M1b) in these embodiments of the invention.
As stated above, the presence of CO2 in an amount of at least 18% vol, preferably of at least 20% vol, allows increasing the safety of the process, because it has a stabilizing effect on the mixture of products formed in the course of the reaction, in particular on mixtures of C2F4 and C2F4I2. More specifically, it has been observed that an amount of at least 18% vol, preferably of at least 20% vol, mitigates the maximum pressure reached in the reactor, while an amount of at least 27% allows avoiding the risk of explosion.
With respect to process (C), process (D) provides a further advantage, which is that of reducing the amount of undesired cy-C4F8 that forms as by-product. While in process (C) an overall weight amount of cy-C4F8 typically in the range of 35% to 40% with respect to mixture (M2b) is obtained, in process (D) the amount of this side product is below 20%. Process (D) is further advantageous in that purging the reactor during step (b2) is not required, which makes the process less troublesome and avoids losses of CO2 and TFE.
The invention and its advantages will be herein after illustrated in greater detail in the following experimental section and non-limiting examples.
Should the disclosure of any patents, patent applications, and publications which are incorporated herein by reference conflict with the description of the present application to the extent that it may render a term unclear, the present description shall take precedence.
1. General Procedure for Process (C)
A mixture (M1b) containing a definite amount of C2F4I2 was introduced in a stainless steel reactor and the temperature was raised to 200° C.; thereafter, a TFE and CO2 mixture (80:20 by vol) was fed in continuous in the reactor. Pressure was adjusted at 2,500 kPa by purging the reactor. At the end of the reaction, the reactor was cooled down to room temperature and discharged. In the course of the process, cy-C4F8, TFE and CO2 were purged from the reactor and not recovered.
2. General Procedure for Process (D)
A mixture (M1b) containing a definite amount of C2F4I2 was introduced in a stainless steel reactor and uncondensable substances were evacuated after having cooled the reactor with dry-ice. The temperature was raised to 50° C. and the pressure was equilibrated to 530 kPa with CO2 while stirring. Thereafter, the temperature was raised to 235° C., while pressure rose up to 3,000 kPa, and heating was continued until the composition of withdrawn samples revealed an amount of CO2 of at least 30% vol (about 3 hrs).
At this stage, the temperature was lowered to 130° C. and TFE was added keeping the reactor at a maximum pressure of 1,500 kPa. Thereafter, the reactor was cooled down to room temperature, purged and discharged.
3. Stability Test
The explosivity of TFE, C2F4I2 and C4F8I2 and of TFE/C2F4I2 mixtures was evaluated by measuring the pressure at explosion.
The test was performed in a vertically mounted stainless steel autoclave (0.34 L volume and 48 mm diameter).
Pressure at explosion was measured by means of a quick response pressure transducer (oscillation frequency of the membrane of 10 kHz minimum), an electronic transducer and a cathode-beam oscillograph. The pressure transducer was mounted on top of the autoclave.
An ignitor was installed at a distance of 20-30 mm from the bottom of the autoclave close to the symmetry axis. A nichrome wire (diameter: 0.25 mm; length; 4-6 mm), fused by applying a 150V, was used as the ignitor.
An electrically heated nichrome wire spiral (spiral diameter: 10-12 mm; nichrome wire diameter: 1.1 mm; number of turns: 11; spiral length: 30-35 mm) was installed at the bottom of the autoclave in order to intensify convection when mixing the tested compounds or mixtures.
Following the procedure disclosed at point 1 of the section “Material and methods”, Examples 1 and 2 were carried out in a 0.6 L stainless steel reactor with the amounts of reagents and conditions reported in Table 1 below.
At the end of the reaction, mixtures (M2b) were obtained with the compositions reported in Table 2 below.
Following the procedure disclosed at point 2 of the section “Material and methods”, Examples 3 and 4 were carried out in a 0.6 L stainless steel reactor with the amounts of reagents and conditions reported in Table 3 below.
At the end of the reaction, mixtures (M2b) were obtained with the compositions reported in Table 4 below.
Results of Stability Tests
Table 5 below reports the results of stability tests carried out on TFE alone and on mixtures of TFE with C2F4I2 or C4F8I2 at different initial temperatures and pressures (P0) in the absence of CO2. The results are expressed as the ratio between the maximum pressure reached after ignition (Pmax) and P0. For Pmax/P0 ratios lower than or equal to 1.1 the compound or the mixture is considered stable and not exploding.
The results show (see in particular entries 13-15 compared to entry 3) that mixtures of TFE and C2F4I2 have a higher Pmax/P0 ratio than TFE, so they are less safe than TFE alone. The same result was obtained with mixtures of TFE and C4F8I2 (see in particular entry 6).
Table 6 below reports instead the results of stability tests carried out on mixtures of TFE and C2F4I2 at different pressures P0 and at different concentrations of CO2.
The results show that, when the concentration of CO2 in the mixture is 18% vol, the Pmax/P0 value is significantly lower. The results further show that, when the concentration of CO2 in the mixture is 27% vol, no explosion occurs.
| Number | Date | Country | Kind |
|---|---|---|---|
| 14164336 | Apr 2014 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2015/057655 | 4/9/2015 | WO | 00 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2015/155264 | 10/15/2015 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 3404189 | Blochl | Oct 1968 | A |
| 3523140 | Cammarata et al. | Aug 1970 | A |
| 3644544 | Cammarata et al. | Feb 1972 | A |
| 4861845 | Slocum | Aug 1989 | A |
| 4922041 | Naumann et al. | May 1990 | A |
| 5268516 | Bertocchio et al. | Dec 1993 | A |
| 5345013 | Van Bramer | Sep 1994 | A |
| 7071367 | Mukhopadhyay et al. | Jul 2006 | B1 |
| Number | Date | Country |
|---|---|---|
| 51133206 | Nov 1976 | JP |
| 53144507 | Dec 1978 | JP |
| 9429250 | Dec 1994 | WO |
| 9834967 | Aug 1998 | WO |
| 9919248 | Apr 1999 | WO |
| Entry |
|---|
| Tortelli V. et al., “Telomerization of tetrafluoroethylene and hexafluoropropene: synthesis of diiodoperfluoroalkanes”, J. Fluorine Chem., 1990, vol. 47, p. 199-217. |
| “Ferrero F. et al., ““Analysis of the self-heating process of tetrafluoroethylene in a 100 dm3 reactor””, Journal of Loss Prevention in the Process Industries, 2012, vol. 25, Issue 6, p. 1010-1017—Elsevier Ltd.” |
| Number | Date | Country | |
|---|---|---|---|
| 20170029349 A1 | Feb 2017 | US |
