Patent Application
20200172671
The present invention relates to a process for preparing a semiaromatic copolyamide by implementing a specific aliphatic acid, and also to the use of this acid as a chain limiter for the semiaromatic copolyamide and to the use of the copolyamide. The invention also relates to a composition comprising such a copolyamide and also to the uses of this composition.
It is known practice to use stearic acid as a chain limiter in the synthesis of semiaromatic polyamides. Specifically, polyamide synthesis is performed by polycondensation of a diacid and of a diamine, an amino acid or a lactam. Thus, the amine functions react with the acid functions to form the amide group. In order to better control this polycondensation, it is known practice to add to the reaction medium a monocarboxylic acid which reacts with the amine functions present in the medium and thus blocks the polycondensation.
It is known practice to use monocarboxylic acids, such as stearic acid or benzoic acid, for the synthesis of semiaromatic polyamide, in particular of the polyamide PA 11/10.T, i.e. the polyamide derived from the polycondensation of 11-aminoundecanoic acid, 1,10-decanediamine and terephthalic acid. Now, the formation of foam in large amount and especially of stearic acid has been observed in the industrial synthesis of this copolyamide.
Despite the addition of an antifoam to the reaction medium, an increase in the level of the product is observed in the reactor. As a result, to avoid entraining matter or its solidification in the top of the reactor, it is necessary to reduce the total feedstock introduced.
Thus, there is a real need to find a synthetic process that does not lead to the formation of foam in the reaction medium. The Applicant has found, surprisingly, that the use of a linear C1-C7 aliphatic acid as chain limiter, contrary to fatty acids and aromatic carboxylic acids, can prevent this phenomenon of foam and can thus avoid the use of an antifoam in the course of this synthetic process.
Consequently, the invention relates to the process for preparing a semiaromatic copolyamide comprising at least two units corresponding to the following general formula A/10.T in which
A subject of the invention is also the use of a linear C1-C7 aliphatic acid as a chain limiter in the synthesis of the copolyamide as defined above for substantially reducing the level of foaming during the polycondensation of a semiaromatic copolyamide in a reactor.
Other characteristics, aspects and advantages of the present invention will emerge even more clearly on reading the description and the examples that follow.
The Process
The invention relates to a process for preparing a semiaromatic copolyamide comprising at least two units corresponding to the following general formula A/10.T in which
The inventors have thus found that the use of a short-chain (C1-C7) linear C1-C7 aliphatic acid, as a chain limiter, in particular acetic acid, allows the industrial preparation of a semiaromatic copolyamide by substantially reducing the level of foaming in the reactor during the step of polycondensation of the comonomers relative to the level observed without the linear C1-C7 aliphatic acid.
Advantageously, the short-chain (C1-C7) linear C1-C7 aliphatic acid is a monoacid.
The term “substantially” should be understood as meaning a reduction of at least 10% in the level of foaming relative to the level observed without the linear C1-C7 aliphatic acid. The use of a linear aliphatic acid limits the phenomenon of foaming and thus prevents the entrainment of matter or its solidification in the top of the reactor and thus avoids the need to reduce the total feedstock of comonomers introduced, thus allowing a saving in time and cost during the preparation of the same amount of semiaromatic copolyamide.
Consequently, the presence of a linear aliphatic acid in said process makes it possible to perform the process on a large reactor size, in any event on a size greater than that used in the absence of said linear aliphatic acid even in the presence of an antifoam.
Thus, for example, for a reactor with a capacity of 1 ton, a reduction of at least 10% in the level of foaming in said reactor makes it possible to introduce therein at least 100 kg more of monomers.
In one embodiment, the polycondensation step is performed in the absence of antifoam.
Another advantage of the invention is thus the possible suppression of the use of an antifoam, thus allowing a saving in the cost of the process.
In another embodiment, an antifoam is also used, especially in a weight proportion relative to the total weight of all the constituents introduced into the reactor of from 1 to 500 ppm, in particular from 10 to 250 ppm and more particularly from 10 to 50 ppm.
The antifoams usually used are optionally based on silicon, especially crude silicone oils, or in the form of aqueous dispersions, such as Silikonol 1000, Tegiloxan AV1000, Silcolapse RG22 or EFKA™ 2720 (BASF).
Advantageously, the level of foaming is reduced by at least 10%, especially by at least 20%, in particular by 20% to about 30% relative to the level observed without the linear C1-C7 aliphatic acid. As a function of the presence or absence of antifoam, the observed reduction in the level of foaming is more or less pronounced, but it is in any case at least 10% in the absence of antifoam.
All the percentages of reduction of foaming in the description are given relative to the level observed without the linear C1-C7 aliphatic acid, irrespective of the presence or absence of antifoam.
In one embodiment, said polycondensation step is performed in a single step in the same reactor at a temperature from 200 to 300° C., in particular above the melting point of the semiaromatic copolyamide, at a pressure which may rise up to 30 bar and gradually reduced down to a pressure less than or equal to atmospheric pressure so as to complete the polymerization.
The reaction temperature in this polycondensation step must be higher than the melting point of the semiaromatic copolyamide in order for stirring to be able to be performed.
Said reaction thus produces as intermediates semiaromatic oligomers, which, by condensation with each other, lead directly to the semiaromatic copolyamide in the same reactor.
The level of foaming is thus lowered by at least 10%, especially by at least 20% and in particular by 20% to about 30% in said reactor.
Optionally, the polymer may be removed from said reactor at a pressure above atmospheric pressure. The polymerization may then be optionally completed by a step of extrusion at a temperature above the melting point, or by a step of heating at a temperature below the melting point of the copolyamide according to a “solid-state polymerization” process.
In another embodiment, the polycondensation step is performed in three steps and comprises the following steps:
Optionally, the polymer after completion of the polymerization in step c. may be removed from said polymerizer at a pressure above atmospheric pressure. The polymerization may then be optionally completed by a step of extrusion at a temperature above the melting point, or by a step of heating at a temperature below the melting point of the copolyamide according to a “solid-state polymerization” process.
The first step corresponds to the formation in the concentrator of the semiaromatic prepolymer with a molecular mass (Mn) from about 1000 to 8000 as determined by NMR.
The second step corresponds to the transfer of the semiaromatic prepolymer into a polymerizer. As a general rule, this step is accompanied by a pressure reduction, and the semiaromatic copolyamide is then formed in the third step by condensation of the prepolymer on itself by heating especially above the melting point of the polymer. Advantageously, the heating temperature to obtain the semiaromatic copolyamide in this third step is 10° C. higher than the melting point of said copolyamide.
In one embodiment, the reduction in the level of foaming takes place at least during the first step, in the concentrator, and is in particular at least 10%, especially at least 20%, in particular from 20% to about 30%.
Advantageously, the reduction in the level of foaming takes place during the first step in the concentrator, and is in particular at least 10%, especially at least 20%, in particular from 20% to about 30%, and also during the third step in the polymerizer, and is in particular at least 10%, especially at least 19%, in particular from 19% to about 30%.
Advantageously, the linear C1-C7 aliphatic acid is in a weight proportion relative to the total weight of all the constituents introduced into the reactor of from 0.1% to 3%, in particular from 0.1 to 1%.
Preferably, the linear C1-C7 aliphatic acid is chosen from acetic acid, propanoic acid and butanoic acid, and a mixture thereof. Preferentially, acetic acid or propanoic acid is used, in particular acetic acid.
As more particularly regards the meaning of the unit A, when A represents an amino acid, it may be chosen from 9-aminononanoic acid (A=9), 10-aminodecanoic acid (A=10), 12-aminododecanoic acid (A=12) and 11-aminoundecanoic acid (A=11) and also derivatives thereof, especially N-heptyl-11-aminoundecanoic acid.
Instead of one amino acid, a mixture of two, three or more amino acids may also be envisaged. However, the copolyamides formed would then comprise three, four, or more units, respectively.
When A represents a lactam, it may be chosen from pelargolactam, decanolactam, undecanolactam and lauryllactam (A=12).
Preferably, A denotes a unit obtained from a monomer chosen from 11-aminoundecanoic acid (denoted 11), 12-aminododecanoic acid (denoted 12) and lauryllactam (denoted L12).
Preferably, A denotes 11-aminoundecanoic acid (denoted 11).
The invention also relates to the semiaromatic copolyamides that may be obtained via the industrial process defined above, especially to 11/10.T.
A subject of the invention is also the use of a linear C1-C7 aliphatic acid as a chain limiter in the synthesis of the copolyamide as defined above, for substantially reducing the level of foaming in a reactor during the step of polycondensation of the comonomers relative to the level observed without the linear C1-C7 aliphatic acid.
Advantageously, the linear C1-C7 aliphatic acid is a monoacid.
Advantageously, the use of a linear C1-C7 aliphatic acid defined above is performed in the absence of antifoam.
Advantageously, the linear C1-C7 aliphatic acid may be used in a process in which the polycondensation step is performed in the same reactor in a single step as defined above, or in a process in which the polycondensation step is performed in three steps as defined above.
Advantageously, the level of foaming observed, with the use of a linear C1-C7 aliphatic acid defined above, is reduced by at least 10%, especially by at least 20%, in particular by 20% to about 30% relative to the level observed without the linear C1-C7 aliphatic acid.
Advantageously, the linear C1-C7 aliphatic acid is in a weight proportion relative to the total weight of all the constituents introduced into the reactor of from 0.1% to 3%, in particular from 0.1 to 1%.
Advantageously, the linear C1-C7 aliphatic acid is chosen from acetic acid and propanoic acid, and in particular the linear C1-C7 aliphatic acid is acetic acid.
Advantageously, the use of a linear C1-C7 aliphatic acid defined above is performed with a copolyamide 11/10.T.
The examples that follow serve to illustrate the invention without, however, being limiting in nature.
Comparison of the level of foaming during the preparation of a PA 11/10T (0.7/1 mol %) in the presence of stearic acid or acetic acid in a process comprising a polycondensation step in three steps.
The comonomers comprising stearic acid or acetic acid, sodium hypophosphite, Silikonol 1000 and water in proportions as defined in Table I below are introduced into the concentrator and heated at a temperature from 200 to 300° C. at a pressure from 20 to 30 bar to form a prepolymer, and the prepolymer is then transferred into a polymerizer and the prepolymer is then heated in the polymerizer at a temperature from 200° C. to 300° C. at a pressure of 20 to 30 bar, and the pressure is then gradually reduced to atmospheric pressure.
The level of foaming is determined by means of a detector for measuring the maximum level of the reaction medium in the concentrator and in the polymerizer for each compound (Example 1 and comparative example).
The same type of result was observed with a one-step process in a single reactor.
| Number | Date | Country | Kind |
|---|---|---|---|
| FR14.62304 | Dec 2014 | FR | national |
This application in a Continuation Application of, and claims benefit to, copending application number U.S. Ser. No. 15/535,269, filed Jun. 12, 2017; which claimed benefit, under U.S.C. § 119 or § 365 of PCT Application Number PCT/FR2015/053389, filed Dec. 9, 2015, and French Patent Application Number FR14.62304, filed Dec. 12, 2014. The disclosure of each of these applications is incorporated herein by reference in its entirety for all purposes.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 15535269 | Jun 2017 | US |
| Child | 16783366 | US |
