Method for preparing a 1,4:3,6-dianhydrohexitol diester composition

Abstract

The present invention relates to a method for preparing C13-C29 alkyl diesters of 1,4:3,6-dianhydrohexitol, a) a first step of esterifying 1,4:3,6-dianhydrohexitol with an excess of fatty acids having a C13-C29 alkyl chain to form a crude reaction product comprising C13-C29 alkyl diesters of 1,4:3,6-dianhydrohexitol and unreacted fatty acids; b) a second step of esterifying the unreacted fatty acids with a primary or aromatic diol.

Description

Technical Field

[0001] The present invention relates to a method for preparing a 1,4:3,6-dianedrohexitol alkyl diester composition and to their use in the preparation of polycarbonates, in particular for improving the melt flow of polycarbonates.

Background Art

[0002] It is known that adding an alkyl diester of 1,4:3,6-dianedrohexitol, such as isosorbide, to a polymer can facilitate its molding. At that time, they act as "plasticizers".

[0003] The most commonly used plasticizers today belong to the phthalic acid ester family (phthalates). Phthalates are low-cost and readily available on the market, but alternatives are being developed due to concerns about toxicity.

[0004] For example, European Patent No. 3 443 033 (B1) describes that the C8 / C10 alkyl diester of isosorbide, commercially available by the applicant under the trade name Polysorb ID46, facilitates their preparation, in particular by improving the melt flow of polycarbonates.

[0005] 1,4:3,6-Dianedrohexitol alkyl diesters have conventionally been prepared by esterifying 1,4:3,6-dianedrohexitol with an excess of fatty acid, typically in the presence of an acidic catalyst. The reaction crude product contains unreacted fatty acid (residual fatty acid). Since this fatty acid has an adverse effect on the use of the diester composition as a plasticizer, the reaction crude product is subjected to a distillation step or to a liquid-liquid washing step including washing with water in the presence of a weak base such as sodium bicarbonate, followed by a drying step, and is removed at the end of the esterification step.

[0006] As detailed in International Publication No. WO 2006 / 103338 (A1), certain 1,4:3,6-dianhydrohexitol diester compositions exhibit an undesirable yellow coloration, particularly when these compositions are intended for use in transparent plastics such as polycarbonates. The solution proposed in this patent document is to treat the reaction crude product with a specific acid, hypophosphorous acid, which acts as a decolorizing agent.

[0007] There is a continuing need to develop new additives for the preparation of synthetic polymers.

[0008] In the course of that research, the Applicant company found that in the process of preparing polycarbonates, C8 / C10 alkyl diesters do not have the expected effects and, in addition, color the polycarbonates. The Applicant company developed new long-chain alkyl diesters of 1,4:3,6-dianhydrohexitol. During the development, it was found that the application of a residual fatty acid removal step by liquid-liquid distillation or washing results in the decomposition of the diester fraction into monoesters and the yellowing of the product.

[0009] Therefore, there is a need to find a method that enables the preparation, on an industrial scale and in good yield, of a composition of long-chain alkyl diesters of 1,4:3,6-dianhydrohexitol that has low coloration and a minimal residual fatty acid content and can be used during the molding thereof in the preparation of polycarbonates. SUMMARY OF THE INVENTION

[0010] First Aspect According to a first aspect, the present invention is a method for preparing a composition of C13-C29 alkyl diesters of 1,4:3,6-dianhydrohexitol, comprising a) Esterifying 1,4:3,6-dianhydrohexitol with an excess of fatty acids having a C13-C29 alkyl chain to form a crude reaction product containing a C13-C29 alkyldiester of 1,4:3,6-dianhydrohexitol and unreacted fatty acids in a first step; b) Esterifying the unreacted fatty acids with a primary or aromatic diol in a second step, relates to a method.

[0011] As described above, the Applicant has found that when a composition obtained by esterifying 1,4:3,6-dianhydrohexitol with a long-chain fatty acid is purified by distillation, the resulting composition exhibits undesirable coloring. Regarding liquid-liquid washing, the Applicant has observed that the drying step applied after washing with water in the presence of a weak base generates coloring. In the case of saturated fatty acids, the resulting crude reaction product is solid and can only be washed at a temperature higher than its melting point, typically higher than 80 °C, and it has also been found to cause partial hydrolysis of the 1,4:3,6-dianhydrohexitol diester.

[0012] Without being bound by any particular theory, the inventors believe that in the prior art methods, the risk of cleavage of the diester to the monoester increases with the temperature applied during removal by distillation or liquid-liquid washing, which is considered to be higher the longer the alkyl chain.

[0013] The inventors have developed a method that, unlike prior art methods, does not require liquid-liquid distillation or washing in the removal of residual fatty acids.

[0014] The method according to the invention is simple and cost-effective to implement on an industrial scale. It is based on two sequential esterification steps.

[0015] The first step involves esterifying 1,4:3,6-dianhydrohexitol with an excess of long-chain fatty acids to obtain as much diester as possible.

[0016] The second step involves esterifying the residual fatty acids with a primary or aromatic diol to remove most, almost all, or even all of the fatty acids that did not react in the first esterification step.

[0017] This removal by esterification has the advantage of being easier to implement than removal by distillation and can be carried out directly in the esterification reactor used in the first esterification step.

[0018] Thus, the method according to the invention is advantageously a one-step process, i.e., a preparation process in which the steps are carried out continuously in the same reactor. The method according to the invention advantageously does not include an isolation, separation, or purification step by evaporation, for example, by distillation.

[0019] Furthermore, as will be detailed below, the composition obtained by the method according to the invention has little coloration and is effective in the polycarbonate preparation process.

[0020] “C13 - C29 alkyldiester” means an alkyldiester of 1,4:3,6 - dianhydrohexitol in which the alkyl group is bonded to the hydroxyl group of 1,4:3,6 - dianhydrohexitol. This C13 - C29 alkyldiester is produced by the esterification reaction of 1,4:3,6 - dianhydrohexitol with a fatty acid. The esterification reaction can be described as follows: R - OH+HO(O)C - R’ => R - O(O)C - R’+H 2 O. Thus, when the fatty acid used in the esterification has a C13 alkyl chain R’, the alkyl group of the ester is R’ and thus a C13 alkyl group. If only one of the two alcohol functional groups of the diol reacts by esterification, the ester is a monoester. If the two alcohol functional groups of the diol react in the esterification reaction, the ester is a diester. The C13 - C29 alkyldiesters of 1,4:3,6 - dianhydrohexitol can contain different alkyl groups when the diesters are obtained using two different fatty acids.

[0021] For the purposes of the present invention, the expression "fatty acid having a C13-C29 alkyl chain" means a fatty acid R'-COOH, or a mixture thereof, containing 14 to 30 carbon atoms, one carbon atom belonging to a carboxylic acid group (-COOH), and the remaining carbon atoms belonging to a substituted or unsubstituted straight-chain or branched-chain alkyl chain containing 13 to 29 carbon atoms. The alkyl chain is preferably saturated. The alkyl chain may be substituted with at least one group containing a heteroatom selected from oxygen and nitrogen, preferably a ketone or hydroxyl group or amine group. The chain may be substituted at the end of the alkyl chain by a cyclic group typically containing 5 to 12 carbon atoms, preferably 6 to 10 carbon atoms, preferably by a cyclohexane ring or cyclopentane ring, or by a C2-C4 alkyl chain linked to the fatty acid alkyl chain at two attachment points, to form an in-chain ring, preferably an in-chain cyclopropane.

[0022] Step a) In the first step, 1,4:3,6-dianhydrohexitol is esterified with an aliphatic acid having a C13-C29 alkyl chain.

[0023] 1,4:3,6-dianydrohexitol 1,4:3,6-Dianhydrohexitol is a diol having the empirical formula C 6 H 10 O 4

[0024] In the present invention, three isomers of 1,4:3,6-dianhydrohexitol, namely isosorbide, isomannide and isoidide, or a mixture thereof, are used.

[0025] Isosorbide is preferred.

[0026] Fatty acid The fatty acid preferably has a C13-C29, preferably C13-C17 alkyl chain.

[0027] As an example, the fatty acid may be selected from stearic acid (octadecanoic acid C18:0), myristic acid (tetradecanoic acid C14:0), palmitic acid (hexadecanoic acid C16:0), isopalmitic acid (14-methylpentadecanoic acid), margaric acid (heptadecanoic acid C17:0), tuberculostearic acid (10-methylstearic acid), lactobacillic acid (10-[(1R,2S)-2-hexylcyclopropyl]decanoic acid), arachidic acid (eicosanoic acid C20:0), phytic acid (3,7,11,15-tetramethylhexadecanoic acid), 11-cyclohexylundecanoic acid (11-cyclohexylundecanoic acid), or a mixture thereof.

[0028] The fatty acid is preferably a C16 or C18 fatty acid, or a mixture thereof.

[0029] Stearic acid and myristic acid are preferred.

[0030] Excess fatty acid In the first step, in order to promote the formation of C13-C29 alkyldiesters of 1,4:3,6-dianhydrohexitol and minimize the formation of the corresponding monoesters, the fatty acid having a C13-C29 alkyl chain is an excess of 1,4:3,6-dianhydrohexitol.

[0031] "Excess" means a stoichiometric excess, that is, an amount of fatty acid having a C13-C29 alkyl chain that is more than the stoichiometric amount required for the esterification reaction with all the hydroxyl groups of the 1,4:3,6-dianhydrohexitol present. In other words, in the first step of the method according to the present invention, 2y + z moles of fatty acid are preferably reacted with y moles of 1,4:3,6-dianhydrohexitol, where y and z are the number of moles, 2y represents the stoichiometric amount of fatty acid with respect to y moles of 1,4:3,6-dianhydrohexitol, and z represents the amount of fatty acid in excess with respect to the stoichiometric amount. The stoichiometric excess with respect to 1,4:3,6-dianhydrohexitol can also be expressed as a percentage using the formula (z / 2y + z) × 100.

[0032] The fatty acid is preferably in a stoichiometric excess of 10% to 100% with respect to 1,4:3,6-dianhydrohexitol. Preferably, 2.2 to 4 moles of fatty acid are reacted per mole of 1,4:3,6-dianhydrohexitol.

[0033] In other words, 1,4:3,6-dianhydrohexitol is reacted with a fatty acid, preferably at a 1,4:3,6-dianhydrohexitol / fatty acid molar ratio of 1 / 2.2 to 1 / 4.

[0034] Reaction crude For the purposes of the present invention, "reaction crude" means the product of the first step of esterifying 1,4:3,6-dianhydrohexitol with a fatty acid having a C13-C29 alkyl chain, and for which, preferably, a step of removing residual fatty acids, in particular a step of isolation, separation or purification, in particular a step of removing unreacted fatty acids by distillation or a liquid-liquid route, is not applied.

[0035] The reaction crude preferably contains an alkyldiester of 1,4:3,6-dianhydrohexitol, an alkylmonoester of 1,4:3,6-dianhydrohexitol, and unreacted fatty acid.

[0036] Step b) In the second step, the fatty acid that did not react in the first step is esterified with a primary or aromatic diol to remove as much of this fatty acid as possible from the reaction crude.

[0037] The primary or aromatic diol has a higher reactivity than the 1,4:3,6-dianhydrohexitol from step a). Preferably, the primary or aromatic diol does not transesterify with the C13-C29 alkyldiester of 1,4:3,6-dianhydrohexitol of the reaction crude obtained after step a).

[0038] Primary or aromatic diol "Diol" means a compound containing two hydroxyl groups (-OH). The compound preferably has a hydrocarbon structure typically containing from 2 to 20 carbon atoms, preferably from 2 to 12 carbon atoms.

[0039] The diol used in step b) is a primary or aromatic diol.

[0040] "Primary diol" means a diol in which the hydroxyl group is carried by a carbon atom having at least two hydrogen atoms.

[0041] "Aromatic diol" means a diol in which the hydroxyl group is carried by a carbon atom of an aromatic ring.

[0042] "Aromatic ring" means a polyunsaturated cyclic hydrocarbon structure, the ring structure of which is planar, has (4n + 2) delocalized electrons (n is an integer), has a single ring or several rings fused together, and typically contains from 5 to 12 carbon atoms, preferably from 6 to 10 carbon atoms. A preferred aromatic ring is phenyl.

[0043] The primary diol preferably contains from 2 to 20 carbon atoms, more preferably from 2 to 15 carbon atoms.

[0044] For example, the primary or aromatic diol can be selected from ethylene glycol, cyclohexanedimethanol (CHDM), neopentyl glycol (NPG), 1,4 - butanediol, 1,2 - benzenedimethanol, 1,3 - benzenedimethanol, 1,4 - benzenedimethanol, resorcinol, 1,5 - pentanediol, 1,6 - hexanediol, 1,8 - octanediol, 1,10 - decanediol, 1,12 - dodecanediol, or mixtures thereof.

[0045] Ethylene glycol is preferred.

[0046] In the second step, the primary or aromatic diol is preferably introduced in a stoichiometric ratio or a slightly deficient ratio with respect to the fatty acid that did not react in the first step, to remove substantially all of this fatty acid. Without being bound by any particular theory, the inventors believe that when the primary or aromatic diol is added stoichiometrically in excess with respect to the residual fatty acid, there is a risk that the final composition will contain the monoester of this primary or aromatic diol, which is associated with the risk of transesterification and thus the risk of forming 1,4:3,6-dianhydrohexitol monoester.

[0047] "A primary or aromatic diol in a slightly deficient ratio with respect to the fatty acid that did not react in the first step" means a stoichiometric deficiency, i.e., an amount of primary or aromatic diol that is slightly less than the stoichiometric amount required for the esterification reaction of all the hydroxyl groups of the fatty acid that did not react in the first step.

[0048] The first esterification step generally involves reacting 0.45 to 0.5 moles of the primary or aromatic diol per mole of the excess fatty acid. Typically, when the first esterification reaction in step a) is carried out using a molar amount of fatty acid that exceeds the stoichiometric amount (which can be represented as "z" as detailed above), the second esterification reaction in step b) is carried out using a molar amount of the primary diol corresponding to 45% to 50% of the molar amount of the fatty acid used in excess of the stoichiometric amount in step a). As an example, in step a), if 2.3 moles of fatty acid are introduced per mole of 1,4:3,6-dianhydrohexitol (i.e., fatty acid in excess of z = 0.3 moles), then in step b), it is preferably 0.3 × 45% = 0.135 to 0.3 × 50% (i.e., 0.3 / 2) = 0.15 moles of the primary or aromatic diol.

[0049] Esterification conditions The esterification step can be carried out under conventional conditions already used in the literature. These esterification methods are described, for example, in the literature, WO 99 / 45060 (A1) or WO 2006 / 103338 (A1).

[0050] The esterification step is preferably carried out in the presence of at least one acid catalyst.

[0051] The acid catalysts used can be of very diverse nature. For example, the acid catalyst can be selected from hypophosphorous acid, hydrochloric acid, sulfuric acid, para-toluenesulfonic acid (APTS), methanesulfonic acid (AMS), trifluoromethanesulfonic acid, trifluoroacetic acid, trichloroacetic acid, tin ethyl-2- hexanoate, phosphotungstic acid and silicotungstic acid or mixtures of these acids, or macroporous or non-macroporous resins containing at least one of these acids.

[0052] In the case of acid catalyst mixtures, they may or may not be introduced simultaneously into the reaction medium.

[0053] The mass of the acid catalyst can range from 0.05 to 20%, for example from 0.1 to 10%, of the mass of 1,4:3,6-dianhydrohexitol introduced into the reactor.

[0054] It should be noted that hypophosphorous acid can also act as a decolorizing agent. This may or may not be introduced into the reaction medium simultaneously with another acid catalyst and / or a fatty acid. According to one variant, this introduction is carried out before or at the start of the esterification reaction, i.e., before the introduction of the acid catalyst and / or the fatty acid. Advantageously, regardless of when it is introduced, hypophosphorous acid is introduced in an amount of 0.05 to 2%, preferably 0.1 to 1% on a dry weight basis relative to the dry weight of the 1,4:3,6-dianhydrohexitol used. According to another variant, hypophosphorous acid is introduced at a hypophosphorous acid / acid catalyst ratio of less than 1 / 1, whether or not it is simultaneous with the acid esterification catalyst, and the ratio is expressed as the dry weight of hypophosphorous acid relative to the dry weight of the acid catalyst. In particular, the ratio can be 0.01 / 1 to 0.9 / 1, preferably 0.02 / 1 to 0.8 / 1. When the catalyst is APTS, methanesulfonic acid, or phosphotungstic acid, the ratio can advantageously be 0.05 / 1 to 0.4 / 1.

[0055] The temperature in the reactor can be in the range of 90 to 200 °C, generally 100 to 160 °C. To carry out the esterification reaction, generally, water is removed, for example, by distilling the reaction medium, to promote diester formation. To facilitate this removal, the reaction medium can be placed under vacuum, for example, at a level in the range of 10 to 200 mbar. The reaction conditions such as the vacuum level and temperature can be changed during the reaction.

[0056] The first esterification step usually continues until a satisfactory conversion to 1,4:3,6-dianhydrohexitol diester is achieved. This can be varied over a wide range of 1 to 10 hours.

[0057] The second esterification stage generally continues until the free fatty acid is satisfactorily removed. This can be varied over a wide range of 1 to 10 hours.

[0058] By introducing a base such as soda ash in a molar amount equivalent to the molar amount of the introduced catalyst, a neutralization step can also be performed on the introduced catalyst. This neutralization step is preferably carried out after the second esterification step.

[0059] Color reducer The method according to the present invention can also include a step for decolorizing the reaction crude product from step a) using a color reducer such as activated carbon or hydrogen peroxide, or a bleaching earth such as bleaching clay, bentonite, or montmorillonite.

[0060] This step can be carried out continuously following one of steps a) and / or b). In this embodiment, the decolorizing agent is added after one of steps a) and / or b).

[0061] This step can also be carried out simultaneously with steps a) and / or b). In this embodiment, the decolorizing agent is added after the start of one of steps a) and / or b).

[0062] Treatment with activated carbon is carried out, for example, by contacting the reaction crude product with 1 to 5% by weight of activated carbon. The temperature during this treatment can be about 100 °C. The duration is generally several tens of minutes, for example, approximately 1 hour. At the end of the treatment, the activated carbon is separated by filtration. Treatment with bleaching earth is the same as treatment with activated carbon.

[0063] Conventional hydrogen peroxide decolorization treatment consists of, for example, introducing 0.5 to 2% of 100% hydrogen peroxide into the composition to be decolorized at a temperature of 90 °C to 100 °C for 30 to 60 minutes, and then stirring the composition at this temperature for 1 to 2 hours. When it is desired to combine these two types of decolorization treatments, the hydrogen peroxide treatment is preferred over the activated carbon treatment.

[0064] Preferred embodiment In a preferred embodiment, the method according to the present invention enables the preparation of a composition of C13 - C29 alkyl diesters of isosorbide, and the method is a) A first step of esterifying isosorbide with an excess of a fatty acid having a C13-C29 alkyl chain, for example, an isosorbide / fatty acid molar ratio of 1 / 2.3 to 1 / 3, to form a crude reaction product containing an alkyl diester of isosorbide and unreacted fatty acid; b) A second step of esterifying the unreacted fatty acid with a primary or aromatic diol, preferably ethylene glycol; The fatty acid having a C13-C29 alkyl chain is preferably a fatty acid having a C13, C14, C15, C16, C17 or C18 alkyl chain.

[0065] Second aspect A second object of the present invention relates to a C13-C29 alkyl diester composition of 1,4:3,6-dianhydrohexitol that can be obtained by the method of the first object of the present invention.

[0066] In fact, when the diester composition is obtained from different 1,4:3,6-dianhydrohexitols, different primary and / or aromatic diols, and / or different fatty acids having a C13-C29 alkyl chain, a very complex and diverse composition is obtained, and the composition can be more satisfactorily specified only by this preparation method.

[0067] However, the composition according to the present invention can be relatively easily specified when using a limited number of 1,4:3,6-dianhydrohexitols, primary and / or aromatic diols, and / or fatty acids having a C13-C29 alkyl chain.

[0068] Third aspect Accordingly, a third object of the present invention is a C13-C29 alkyl diester composition, based on the weight of the composition: - 35 to 85% by weight of a C13-C29 alkyl diester (A) of 1,4:3,6-dianhydrohexitol; - 10 to 50% by weight of a diester (B) of a primary or aromatic diol; - Less than 6% by weight of a C13 - C29 alkyl monoester (C) of 1,4:3,6 - dianhydrohexitol, and - Less than 3% by weight of a fatty acid (D) having a C13 - C29 alkyl chain, and The present invention relates to a composition in which the total content of a C13 - C29 alkyl diester (A) of 1,4:3,6 - dianhydrohexitol and a diester (B) of a primary or aromatic diol is 80% - 99% by weight, preferably 90% - 99% by weight. The total content of a C13 - C29 alkyl diester (A) of 1,4:3,6 - dianhydrohexitol and a diester (B) of a primary or aromatic diol is 80% - 99% by weight, preferably 90% - 99% by weight.

[0069] 1,4:3,6 - dianhydrohexitol, primary or aromatic diol, fatty acid and ester are as specified in the first object of the present invention.

[0070] The composition according to the present invention has the advantage of being light - colored.

[0071] The applicant company has also surprisingly found that a composition containing a mixture of a C13 - C29 alkyl diester of 1,4:3,6 - dianhydrohexitol and a diester of a primary or aromatic diol, obtained by removing residual fatty acids according to the prior - art methods by distillation or liquid - liquid washing, and thus containing only one or more alkyl diesters of 1,4:3,6 - dianhydrohexitol but no diester of a primary or aromatic diol, exhibits performance equivalent to or even better than that of a composition containing only one or more alkyl diesters of 1,4:3,6 - dianhydrohexitol.

[0072] The composition according to the present invention preferably contains 50 - 85% of diester (A).

[0073] The composition according to the present invention preferably contains 10 - 50%, more preferably 10 - 35% of diester (B).

[0074] The composition according to the invention preferably contains less than 5%, less than 4%, less than 3%, or less than 2% of monoester (C), typically from 0.5 to 6%, more typically from 2 to 6% of monoester (C).

[0075] The composition according to the invention preferably contains less than 2% or less than 1% of fatty acid (D), typically from 0.5 to 3%, more typically from 1 to 3% of fatty acid (D).

[0076] 1,4:3,6 - Dianhydrohexitol is preferably isosorbide.

[0077] Preferably, the alkyl diester is C13 - C17 and the fatty acid has a C13 - C17 alkyl chain.

[0078] The primary or aromatic diol is preferably ethylene glycol.

[0079] In a preferred embodiment, the composition according to the invention, based on the weight of the composition, - 35 to 85% by weight of isosorbide distearate (A) and, - 10 to 50% by weight of ethylene glycol distearate (B) and, - less than 6% by weight of isosorbide monostearate (C) and, - less than 3% by weight of stearic acid.

[0080] In a preferred embodiment, the composition according to the invention, based on the weight of the composition, - 35 to 85% by weight of isosorbide dimyristate (A) and, - 10 to 50% by weight of ethylene glycol dimyristate and, - less than 6% by weight of isosorbide monomyristate (C) and, - less than 3% by weight of myristic acid.

[0081] The relative amounts of the various esters and fatty acids can be determined by standard methods known to those skilled in the art, typically by gas chromatography or HPLC.

[0082] The composition may also contain trace amounts of monoesters (E) of primary or aromatic diols, for example, 0 to 1% by weight, preferably 0 to 0.1% by weight, based on the weight of the composition.

[0083] The composition may also contain trace amounts of primary or aromatic diols (F), for example, 0 to 1% by weight, preferably 0 to 0.1% by weight, even more preferably 0 to 0.01% by weight of primary or aromatic diols (F), based on the weight of the composition.

[0084] The total content of esters (A), (B), (C), (E), fatty acids (D) and primary or aromatic diols (F) is preferably 100%.

[0085] APHA color The composition advantageously has an APHA color index of less than 30.

[0086] The APHA color index of the composition according to the invention is preferably 10 to 30, more preferably 15 to 25, even more preferably 18 to 22.

[0087] This is particularly advantageous for using the composition according to the invention as an additive, typically as a flow agent in the production of transparent synthetic polymers such as polycarbonates.

[0088] In the present invention, the APHA color index is measured directly on a sample of the composition according to the procedure in ASTM D8005-18 of March 2018. It should be noted that some compositions may be in the form of solids having a melting point of approximately 80°C. In this case, the color index is measured according to ASTM D8005-18 of March 2018, provided that the measurement is carried out at a temperature of 90°C (i.e., a temperature higher than the melting point of the composition) so that the composition is in liquid form.

[0089] Fourth Aspect The third object of the present invention relates to the use of a composition according to the second or third object of the present invention in a method for preparing a synthetic polymer.

[0090] The composition according to the second or third object of the present invention is preferably used as a plasticizer.

[0091] "Plasticizer" generally means a product which, when mixed with a polymer in a sufficient amount, facilitates its shaping, for example by lowering the glass transition temperature of the polymer.

[0092] The composition according to the second or third object of the present invention is particularly suitable for the preparation of transparent synthetic polymers where color is an issue, for example the preparation of polycarbonates.

[0093] The composition according to the second or third object of the present invention is preferably used in a method for preparing polycarbonate, particularly during the shaping of polycarbonate, to improve the melt flow.

[0094] The method for preparing polycarbonate includes at least one step of shaping polycarbonate by extruding a mixture containing a diester composition according to the second or third object of the present invention together with polycarbonate, and the mixture typically contains 3 to 5% by weight of the composition according to the second or third object of the present invention.

[0095] The polycarbonate may be an aliphatic polycarbonate or an aromatic polycarbonate. By way of example, the polycarbonate can be an aromatic polycarbonate, typically, for example, the aromatic polycarbonate described in European Patent No. 3 443 033 (B1). The aromatic polycarbonate preferably has the formula -[CO-O-pR1-R2-pR1-O] nIt is an aromatic polycarbonate containing the monomer unit, wherein R1 represents phenyl optionally substituted by C1-C4 alkyl, R2 represents the group R3(R4R5), R3 is a carbon atom or a ring having 6 carbon atoms, R4 and R5 may be the same or different from each other, and each represents a hydrogen atom or the group (R6)n, R6 represents C1-C4 alkyl, and n represents 1, 2 or 3.

Example

[0096] Analysis method Measurement of the mass of esters and fatty acids The relative ratio of each ester is measured by gas chromatography on a Varian 3400 equipped with an FID detector and a 1077 type split / splitless injector. The column used is a DB1 manufactured by J&W Scientific with a length of 30 meters, an inner diameter of 0.32 mm, and a film thickness of 0.25 mm. The temperature conditions are: injector and detector: 300 °C, column: programmed from 100 °C to 320 °C at 7 °C / min and held at 320 °C for 15 minutes. Injection is carried out in split mode at 80 mL / min using a column head pressure of 14 psi and helium as the carrier gas.

[0097] The relative amount of diester is obtained by the ratio of the sum of the areas of the compounds corresponding to isosorbide diester to the external standard, that is, to heptadecanoic acid.

[0098] APHA color measurement The APHA color index is measured according to ASTM D8005-18, March 2018.

[0099] Example 1: Synthesis of isosorbide distearate, followed by esterification of residual fatty acids by addition of ethylene glycol (according to the present invention) 150 g of isosorbide (1 equivalent) and 876 g of stearic acid (C18:0, 3 equivalents) were introduced into a 2 L jacketed reactor. Under a nitrogen sweep, the reactor was heated to 90 °C to melt the medium. When the medium was melted, staining was performed (APHA = 17). Then, while still under nitrogen, the following were introduced: 3 wt% methanesulfonic acid (relative to isosorbide), 5 wt% hypophosphorous acid (relative to isosorbide), and 1 wt% powdered activated carbon (relative to the total mass of the feed). The medium was heated to 160 °C and then a vacuum gradient from 100 mbar to 5 mbar was applied over 1 hour.

[0100] After 2 hours, the medium was cooled to 100 °C under a nitrogen flow. Samples were taken for analysis and showed the presence of 34% fatty acids, 2% isosorbide monoester, and 64% isosorbide diester.

[0101] Then, 0.5 equivalent of ethylene glycol (relative to isosorbide) was added to the medium. The temperature was lowered to 180 °C and the medium was stirred for a further 2 hours under a vacuum of 5 mbar.

[0102] Then, the medium was cooled to 100 °C, returned to nitrogen, and stoichiometric amounts of sodium hydroxide were added to neutralize the AMS and hypophosphorous acid. The reaction medium was hot filtered (100 °C) through a Beko KD3 filter. The results are as follows (relative weight % in the composition compared to the total weight of the composition).

[0103]

Table 1

[0104] Example 2: Synthesis of isosorbide distearate and purification by distillation (comparative example) 150 g of isosorbide (1 equivalent) and 876 g of stearic acid (C18, 3 equivalents) were introduced into a 2 L jacketed reactor. Under a nitrogen sweep, the reactor was heated to 90 °C to melt the medium. When the medium melted, dyeing was carried out (APHA = 19). Then, still under nitrogen, 3 wt% methanesulfonic acid (relative to isosorbide), 5 wt% hypophosphorous acid (relative to isosorbide) and 1 wt% (relative to the total mass of the feed) of powdered activated carbon were introduced. The medium was heated to 160 °C and a vacuum gradient from 100 mbar to 5 mbar was applied over 2 hours to distill the water of the reaction product. Then, the medium was cooled to 100 °C and stoichiometric amounts of sodium hydroxide were added to neutralize the AMS and hypophosphorous acid. The reaction medium was hot filtered (100 °C) through a Beko KD3 filter. Still at 100 °C, 3000 ppm of Irganox 1010 was added.

[0105] The crude reaction product was distilled in a wiped film evaporator (distillation area: 0.0045 m 2 ) under a vacuum of 0.1 mbar at a feed rate of 1 Kg / h at 190 °C to distill off the excess fatty acid. The composition of the diester in the residue was as follows (relative weight % in the composition relative to the total weight of the composition):

[0106]

Table 2

[0107] Example 3: Varying the excess amount of fatty acid of Example 1 (according to the invention) Into a 2 L jacketed reactor, 150 g of isosorbide (1 equivalent) and 671 g of stearic acid (C18, 2.3 equivalents) were introduced. Under a nitrogen sweep, the reactor was heated to 90 °C to melt the medium. When the medium had melted, staining was carried out (APHA = 19). Then, still under nitrogen, the following were introduced: 3 wt% methanesulfonic acid (relative to isosorbide), 5 wt% hypophosphorous acid (relative to isosorbide) and 1 wt% powdered activated carbon (relative to the total mass of the charge). The medium was heated to 160 °C and then a vacuum gradient from 100 mbar to 65 mbar was applied over 2 hours.

[0108] After 2 hours, the medium was cooled to 100 °C under a nitrogen stream. Then, 0.15 equivalent of ethylene glycol (relative to isosorbide) was added to the medium. The temperature was lowered to 180 °C and the medium was stirred for a further 2 hours.

[0109] Then, the medium was cooled to 100 °C and stoichiometric amounts of sodium hydroxide were added to neutralize the AMS and hypophosphorous acid. The reaction medium was hot filtered (100 °C) through a Beko KD3 filter. The results are as follows (relative weight % in the composition compared to the total weight of the composition).

[0110]

Table 3

[0111] Example 4: Direct incorporation of a second diol, non - sequential esterification (comparative example) 150 g of isosorbide (1 equivalent) is introduced into a 2 L jacketed reactor together with 671 g of stearic acid (C18, 2.3 equivalents) and 0.15 equivalents of ethylene glycol. The reactor is heated to 90 °C under a nitrogen sweep to melt the medium. When the medium was melted, staining was performed (APHA = 19). Then, still under nitrogen, 3 wt% methanesulfonic acid (relative to isosorbide), 5 wt% hypophosphorous acid (relative to isosorbide) and 1 wt% (relative to the total input mass) of powdered activated carbon were introduced. The medium was heated to 160 °C and then a vacuum gradient from 100 mbar to 5 mbar was applied over 4 hours.

[0112] The medium was then cooled to 100 °C and stoichiometric amounts of sodium hydroxide were added to neutralize the AMS and hypophosphorous acid. The reaction medium was hot filtered (100 °C) through a Beko KD3 filter to obtain the following results (relative % of the composition):

[0113] [Table 4]

[0114] Direct incorporation of the second diol at the start increases the monoester and the residual fatty acid content.

[0115] Example 5: Synthesis of isosorbide myristate composition (according to the present invention) Stearic acid was replaced with myristic acid (C14:0) and Example 1 was reproduced. The results are as follows.

[0116] The composition of the medium is as follows (relative weight % in the composition relative to the total weight of the composition):

[0117] [Table 5]

[0118] Example 6: Synthesis of isosorbide distearate and purification by distillation (comparative example) A comparative example identical to Example 2 was produced except that stearic acid (C18:0) was replaced with myristic acid (C14:0). The results after distillation are as follows (relative weight % in the composition compared to the total weight of the composition):

[0119]

Table 6

[0120] Example 7: (According to the present invention) Example 2 was reproduced by replacing ethylene glycol with cyclohexanedimethanol (CHDM). The results are as follows (relative weight % in the composition compared to the total weight of the composition):

[0121]

Table 7

[0122] Example 8 (According to the present invention): Example 2 was reproduced by replacing ethylene glycol with neopentyl glycol (NPG). The results are as follows (relative weight % in the composition compared to the total weight of the composition):

[0123]

Table 8

[0124] Example 9 (According to the present invention): Example 2 was reproduced by replacing ethylene glycol with 1,4 - butanediol. The results are as follows (relative weight % in the composition compared to the total weight of the composition):

[0125]

Table 9

[0126] Example 10 (According to the present invention): Example 2 was reproduced by replacing ethylene glycol with 1,4-benzenedimethanol. The results are as follows (relative weight % in the composition compared to the total weight of the composition):

[0127]

Table 10

[0128] Example 11 (according to the present invention): Example 2 was reproduced by replacing ethylene glycol with resorcinol. The results are as follows (relative weight % in the composition compared to the total weight of the composition):

[0129]

Table 11

[0130] Example 12: Use in a method for preparing a polycarbonate (according to the present invention) The diester compositions of Examples 1, 3, 5 and 7 - 11 (according to the present invention) were used in a method for preparing a polycarbonate.

[0131] A mixture comprising a polycarbonate and about 0.5 wt% of the diester composition of the mixture was extruded.

[0132] The compositions of Examples 1, 3, 5 and 7 - 11 (according to the present invention) were proven to be effective in improving the melt flow of the polycarbonate. By way of example, as follows: For the compositions of Examples 1 and 3, the melt flow index (MFI) was determined according to ISO 1133 using dedicated equipment (CEAST brand, model 7024). The unfilled extruded polycarbonate has an MFI of 12.9 g / 10 min. The same polycarbonate with 0.5% addition of the composition of Example 1 has an MFI of 43.5 g / 10 min. The same polycarbonate with 0.5% addition of the composition of Example 3 has an MFI of 42.75 g / 10 min.

[0133] Furthermore, yellowing of the final product was not observed.

[0134] Example 13: Use in a method for preparing polycarbonate (comparative example) A composition of an isosorbide C8 / C10 alkyl diester commercially available under the name Polysorb ID46 by the company that is the applicant of this application was used in a polycarbonate preparation method.

[0135] The composition of Polysorb ID46 did not improve the melt flow of the polycarbonate. The diester seems to evaporate during molding due to its short alkyl chains. For example, an unadditivated extruded polycarbonate has an MFI of 12.9 g / 10 min. The same polycarbonate with 0.5% of Polysorb ID46 added has an MFI of 15.7 g / 10 min.

[0136] The polycarbonate obtained after extrusion has an undesirable yellow color.

Claims

1. A method for preparing a C13-C29 alkyl diester composition of 1,4:3,6-dianhydrohexitol, comprising: a) a first step of esterifying 1,4:3,6-dianhydrohexitol with an excess of fatty acids having a C13-C29 alkyl chain to form a reaction crude product comprising a C13-C29 alkyl diester of 1,4:3,6-dianhydrohexitol and unreacted fatty acids; b) a second step of esterifying the unreacted fatty acids with a primary or aromatic diol.

2. The method according to claim 1, wherein the 1,4:3,6-dianhydrohexitol is selected from isosorbide, isomannide, isoidide, or a mixture thereof.

3. The method according to claim 1 or 2, wherein the fatty acid is selected from stearic acid, myristic acid, palmitic acid, isopalmitic acid, margaric acid, tuberculostearic acid, lactobacillic acid, arachidic acid, phytic acid, caulmoglucuronic acid, 11-cyclohexylundecanoic acid, or a mixture thereof.

4. The method according to claim 1 or 2, wherein the primary or aromatic diol is selected from ethylene glycol, cyclohexanedimethanol (CHDM), neopentyl glycol (NPG), 1,4-butanediol, 1,4-benzenedimethanol, resorcinol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, 1,12-dodecanediol, or a mixture thereof.

5. The method according to claim 1 or 2, wherein the first and second esterification steps are carried out in the presence of an acid catalyst.

6. A C13-C29 alkyl diester composition of 1,4:3,6-dianhydrohexitol obtainable by the method according to claim 1.

7. A C13-C29 alkyl diester composition of 1,4:3,6-dianhydrohexitol, wherein based on the weight of the composition: - 35 to 90% by weight of a C13-C29 alkyl diester of 1,4:3,6-dianhydrohexitol (A); - 10 to 50% by weight of a diester of a primary or aromatic diol (B); - less than 6% by weight of a C13-C29 alkyl monoester of 1,4:3,6-dianhydrohexitol (C); - less than 3% by weight of a fatty acid having a C13-C29 alkyl chain (D). A composition in which the total content of a C13-C29 alkyl diester (A) of 1,4:3,6-dianhydrohexitol and a diester (B) of a primary or aromatic diol is 80% to 99% by weight, preferably 90% to 99% by weight.

8. The composition according to claim 6 or 7, wherein the 1,4:3,6-dianhydrohexitol is isosorbide.

9. The composition according to claim 6 or 7, wherein the alkyl diester is C13-C17 and the fatty acid has a C13-C17 alkyl chain.

10. The composition according to claim 6 or 7, wherein the primary or aromatic diol is ethylene glycol.

11. Based on the weight of the composition, - 35 to 90% by weight of isosorbide distearate (A), - 10 to 50% by weight of ethylene glycol distearate (B), - less than 6% by weight of isosorbide monostearate (C), - less than 3% by weight of stearic acid (D), and the composition according to claim 6 or 7.

12. Based on the weight of the composition, - 35 to 90% by weight of isosorbide dimyristate (A), - 10 to 50% by weight of ethylene glycol dimyristate (B), - less than 6% by weight of isosorbide monomyristate (C), - less than 3% by weight of myristic acid (D), and the composition according to claim 6 or 7.

13. The composition according to claim 6 or 7, having an APHA color index of less than 30.

14. Use of the composition according to claim 6 or 7 for improving the melt flow of polycarbonate, particularly during its molding, in a method for preparing polycarbonate.