PRODUCTION OF DERIVATIVES OF LACTIDE, PRODUCTION OF

LACTIDES, AND USE OF LACTIDE IN FOODS AND

TO PRODUCE POLYMERS

Field of Invention

The present invention relates to processes for producing derivatives of lactide, processes for preparing a lactide, and use of a lactide prepared by the processes in food compositions, and to produce polymers.

Background

There is a need for new processes for producing derivatives of lactides that are useful for various purposes, and processes for producing lactides that can be used in preparing food compositions, and to produce polymers.

Summary of the Invention

The invention relates to producing derivatives of lactide, such as lactamides, acrylic acid, acid anhydrides, esters, propylene glycol, pyruvic acid and esters thereof and starch modified by lactide. The lactides that are used may be prepared by any process and include lactides prepared by the novel processes described in the invention. Also, this invention relates to the use of lactides produced by the processes described in the invention in the preparation of food compositions, and to produce polymers.

Detailed Description of the Invention The invention relates to producing derivatives of lactide, such as lactamides, acrylic acid, acid anhydrides, esters, propylene glycol, pyruvic acid and esters thereof, and starch modified by lactide. Any lactide may be utilized in producing the derivatives, including lactide prepared by the novel processes of the present invention. Also, this invention relates to the use of lactides produced by the processes described in the invention in the preparation of food compositions, and to produce polymers.

The derivatives of lactide include lactamides, acrylic acid, acid anhydrides, esters, propylene glycol, pyruvic acid and esters thereof, and starch modified by lactide.

Lactamides From Lactide

The present invention provides a process for producing lactamides comprising reacting a lactide with ammonia or an amine, in the presence of a catalyst. The amine suitable for use in the reaction with lactide includes amines having the formula R ₁ R ₂ NH, where R ₁ and R ₂ are individually similar or dissimilar, and represent hydrogen, a C ₁ -C ₂₀ alkyl group, linear or branched, optionally substituted by a halogen, alkoxy, hydroxyl, thiol, sulfonate ester, or nitro group, or a C ₄ -C ₂₀ aryl group, optionally substituted by a halogen, alkoxy, hydroxyl, thiol, sulfonate ester, or nitro group. Exemplary of the amines suitable for use include, but are not limited to, methylamine, dimethyl amine, trirnethylamine, ethylamine, diethylamine, triethylamine, hydroxylamine, methoxylamine, ethoxylamine, ethanolamine, and diethanolamine. The amine used in the reaction with lactide may be a diamino compound having the formula R ₁ R ₂ NR ₃ NR ₄ Rs where R ₁ , R ₂ , R ₃ , R ₄ and R ₅ are individually similar or dissimilar, and represent hydrogen, except for R ₃ , an C ₁ -C ₂₀ alkyl group, linear or branched, optionally substituted by a halogen, alkoxy, hydroxyl, thiol, sulfonate ester, or nitro group, or a C ₄ -C ₂₀ aryl group, optionally substituted by a halogen, alkoxy, hydroxyl, thiol, sulfonate ester, or nitro group. Exemplary of amines suitable for use herein are ethylenediamine, hexamethylenediamine, methyl-1, 3-propanediamine, 1, 6-hexanediamine, diaminopropane, diaminobutane, diaminopentane, and diaminocyclohexane. The amine suitable for use may also include a triamino compound such as diethylenetriamine, aminoethylpiperazine, and nitrogen heterocycles such as piperazine, pyridine, pyrole and imidazole.

The catalyst used in producing the lactamides can be any acid or base catalyst. Exemplary of the acid catalysts are mineral acids, such as sulfuric acid and phosphoric acid. Exemplary of the base catalysts are sodium hydroxide and potassium hydroxide. The process for producing lactamides may be carried out batch wise, semi- continuously, or continuously. The process may be carried out in any suitable apparatus. Exemplary of such apparatus are stirred tank reactors and column type reactors.

The process of the present invention is generally carried out at a temperature ranging from about 20°C to 300 ⁰ C, more particularly from about 100°C to about 250 ⁰ C. There is no specific residence time required for the process of the present invention, other than the residence time be adequate to allow the intended product to be produced.

Preferably, the residence time for the process of the present invention ranges from about 0.1 to 10 hours.

Propylene Glycol From Lactide The present invention provides a process for producing propylene glycol comprising hydrogenating lactide in the presence of a catalyst, either in a liquid phase or in a gas phase.

Any suitable hydrogenation catalyst may be used in the process for producing the propylene glycol. Exemplary of the catalysts are metals such as ruthenium, rhodium, rhenium, palladium, platinum, nickel, cobalt, molybdenum, tungsten, titanium, zirconium, niobium, vanadium, chromium, manganese, osmium, iridium, iron, copper zinc, silver, and gold. Compounds of the metals may also be used, provided the hydrogenation of lactide may be successfully achieved. The compounds of the metals suitable for use include, but are not limited to, oxides, hydroxides, halides, nitrates, carboxylates, and the like. The metals or compounds of the metals may be utilized as the hydrogenation catalyst, either supported or unsupported, and either singly or in combination.

If the catalyst is used in supported form, any conventional method may be used to prepare the supported catalysts. For example, the metals and metal compounds may be impregnated into the support, or deposited onto the support. In general, the supported catalysts comprise up to about 50% by weight of metal or metal compound, preferably up to about 20% by weight. Any suitable support material may be used in preparing the supported catalysts. Exemplary supports that may be used herein include, but are not limited to, ^, alumina, titania, silica, zirconia, carbon, carbon black, graphite, silicate, zeolite, aluminosilicate, and the like. The hydrogenation process for preparing the propylene glycol may be carried out in either gas phase or liquid phase. If a liquid phase is used, the liquid phase includes, but is not limited to, water, an organic solvent that is not hydrogenatable, such as any aliphatic or aromatic hydrocarbon, alcohol, or either, and mixtures of water and organic solvents. The hydrogenation may be carried out batch wise, semi-continuously, or continuously. The process of the present invention may be carried out in any suitable apparatus. Exemplary of such apparatus are stirred tank reactors, trickle-bed reactors, high pressure hydrogenation reactors, and the like.

The hydrogenation process for producing prophylene glycol is generally carried out at a temperature ranging from about 2O ⁰ C to about 25O ⁰ C, more particularly from about 100 ⁰ C to about 200°C. Further, the hydrogenation process is generally carried out in a pressure range of from about 20 psi to about 4000 psi (pound per square inch), and more particularly, in a pressure range of from about 500 psi to about 2000 psi. There is no specific residence time required for the process for producing prophylene glycol, other than the residence time be adequate to allow the intended product to be produced. However, the residence time for the process generally ranges from about 1 to 10 hours.

Esters from Lactide

The present invention provides a process for producing esters from lactide comprising reacting lactide with an alcohol, in the presence of a catalyst.

The following alcohols are suitable for use in the esterification reaction with lactide. The alcohol used in the reaction may have the formula ROH, wherein R is a C ₁ - C ₂₆ alkyl group, linear or branched, optionally substituted by halogen, alkoxy, or hydroxyl, thiol, sulfonate ester or nitro groups, or a C ₄ -C ₂₆ aryl group, optionally substituted by halogen, alkoxy, or hydroxyl, thiol, sulfonate ester, or nitro groups. Alcohols having from 1 to 7 carbon atoms, that include methanol to heptanol, are particularly useful. The alcohols can be primary, secondary or tertiary. Suitable alcohols also include any diols or polyols, such as glycols, 1,3-propanediol, 1,4-butanediol, 1,2-propanediol, and mixtures thereof.

The catalyst used in the process for producing esters may be any suitable esterification catalyst. Suitable esterification catalysts for the process include acidic inorganic and acidic organic compounds such as alumina, titania, silica, zirconia, silicates, zeolites, aluminosilicate, and the like, acidic polymeric compounds such as resins, and mineral acids. Useful mineral acids include acids such as sulfuric or phosphoric acid. Exemplary acid resin catalysts include commercially available compounds such as acidic AMBERLYST® resins (available from Rohm and Haas Co.; Philadelphia, PA), NAFION™ resins (available from DuPont; Wilmington, DE) and acidic DOWEX ™ resins (available from Dow Chemical Co., Midland, MI).

The esterification may be carried out batch wise, semi-continuously, or continuously. The process may be carried out in any suitable apparatus. Exemplary of such apparatus are stirred tank reactors and column reactors, and the like.

The esterification process is generally carried out at a temperature ranging from about 20°C to about 200°C, more particularly from about 2O ⁰ C to about 100°C. There is no specific residence time required for the process, other than the residence time be adequate to allow the intended product to be produced. The residence time for the process ranges from about 1 to 10 hours, in general.

Acid Anhydrides From Lactide

The present invention provides a process for producing acid anhydrides comprising reacting an organic acid with lactide.

Any organic acid may be used in the process for producing acid anhydrides. Suitable organic acids include monoacids such as formic acid, acetic acid, glycolic acid, pyruvic acid, propionic acid, 3-hydroxypropionic acid, butyric acid and valeric acid, di- acids such as malonic acid, maleic acid, fumaric acid, malic acid, succinic acid, itaconic acid, adipic acid, tartaric acid, methylglutaric acid, and phthalic acid, and tri-acids such as citric acid.

The reaction of the process for preparing anhydrides may be carried out batch wise, semi-continuously, or continuously. The process may be carried out in any suitable apparatus. Exemplary of such apparatus are stirred tank reactors and column reactors, and the like.

The process is generally carried out at a temperature ranging from about 2O ⁰ C to about 200 ⁰ C, more particularly from about 2O ⁰ C to about 100 ⁰ C. There is no specific residence time required for the process, other than the residence time be adequate to allow the intended product to be produced. The residence time for the process ranges from about 1 to 10 hours, in general.

Modification of Starch By Lactide

The present invention provides a process for producing modified starch comprising reacting starch with lactide. The reaction results in a modified starch that has a lactate group attached to the starch. The modified starch can lower gelatinization temperature, improve paste clarity, and provide stability to retrogradation and freeze-thaw-stability. A catalyst may be used to facilitate the reaction of the starch with lactide.

The catalyst used in the process of the present invention may be any suitable esterification catalyst. Suitable catalysts for the process include acidic inorganic and acidic organic compounds such as alumina, titania, silica, zirconia, silicates, zeolites, aluminosilicate, and the like, acidic polymeric compounds such as resins, and mineral acids. Useful mineral acids include acids such as sulfuric or phosphoric acid. Exemplary acid resin catalysts include commercially available compounds such as acidic AMBERLYST® resins (available from Rohm and Haas Co.; Philadelphia, PA), NAFION™ resins (available from DuPont; Wilmington, DE) and acidic DOWEX ™ resins (available from Dow Chemical Co., Midland, MI).

The starch used in the process of the present invention can be any starch such as corn starch, wheat starch, potato starch, rice starch, soybean starch, and mixtures thereof.

The process comprising reacting starch with lactide, may be carried out in the presence of a solvent that is suitable to allow the reaction to occur such that the product will be produced. Suitable solvents include, but are not limited to water, organic compounds such as any aliphatic or aromatic hydrocarbons, halogenated aliphatic or aromatic hydrocarbons, ketones, esters, amides, esters, and a mixture of water and organic solvents. The solvent is typically used in an amount ranging from about 1% to about 99% by weight, based on the starch and lactide. The reaction of the present invention may be carried out batch wise, semi- continuously, or continuously. The process of the present invention may be carried out in any suitable apparatus. Exemplary of such apparatus are stirred tank reactors and column reactors, and the like.

The process of the present invention is generally carried out at a temperature ranging from about 20°C to about 200°C, more particularly from about 20°C to about 100°C. There is no specific residence time required for the process of the present invention, other than the residence time be adequate to allow the intended product to be

produced. The residence time for the process of the present invention ranges from about 1 to 10 hours, in general.

Acrylic Acid From Lactide The present invention provides a process for producing acrylic acid from lactide in the presence of a catalyst.

The catalyst to be used in the production of acrylic acid from lactide is any suitable catalyst that will effectuate conversion of lactide to acrylic acid.

Suitable catalysts for the process include acidic catalyst, such as acidic inorganic and acidic organic compounds. Examples of the acidic catalyst include mineral acids, alumina, titania, silica, zirconia, silicates zeolites, aluminosilicate, acidic polymeric resins and the like. Useful mineral acids include acids such as sulfuric or phosphoric acid. Exemplary acidic resin catalysts include commercially available compounds such as NAFION™ resins (available from DuPont; Wilmington, DE) and acidic DOWEX ™ resins (available from Dow Chemical Co., Midland, MI). Suitable catalysts for the process include basic catalyst, such as basic inorganic and basic organic compounds. Examples of basic catalyst include metal hydroxides, metal oxides, amines and the like. Suitable catalysts for the process also include neutral compounds, such as metal phosphates, metal carboxylates, nitrates, sulfates, molybdates, and the like. The process of the present invention may be carried out batch wise, semi- continuously, or continuously. The process of the present invention may be carried out in any suitable apparatus. Exemplary of such apparatus are stirred tank reactors, trickle-bed reactors, pressure reactors, and the like.

The process of the present invention is generally carried out at a temperature ranging from about 2O ⁰ C to about 400°C, more particularly from about 100 ⁰ C to about 300 ⁰ C. There is no specific residence time required for the process of the present invention, other than the residence time be adequate to allow the intended product to be produced. The residence time for the process of the present invention ranges from about 1 to 10 hours, in general.

Pyruvic Acid From Lactide

The present invention provides a process for producing pyruvic acid comprising oxidation of lactide, using air or an oxygen containing gas, in the presence of a catalyst, in a liquid phase or a gas phase. The catalyst used in the process of the present invention may be any suitable oxidation catalyst. Exemplary of the catalysts are metal oxides, metal phosphates and other metal compounds such as hydroxides, halides, nitrates, carboxylates, and molybdates, and a mixture thereof. The metal can be selected from vanadium, molybdenum, tungsten, palladium, platinum, iron, silver, nickel, cobalt, ruthenium, rhodium, rhenium, titanium, zirconium, niobium, chromium, manganese, osmium, iridium, copper, zinc, and gold, and the like. The oxidation catalyst may be used in supported form or unsupported form. The catalysts may be used singly, or as a mixture of catalysts. If desired a promoter, that promotes or enhances the reaction and/or the yield of the reaction, may be used. When used, the promoter is present in an amount of from about 0.001% to about 10%, based on the amount of catalyst used. The promoter may be selected from the elements of Bi, K, Cs, Mg, Sb, As, P, Al, Ce, Ba, B, Sr, Ca, Ge, Cu, Mn, and Sm. Also, any compound of these metals is suitable for use herein provided that the oxidation of lactide either in a liquid or gas phase, to prepare pyruvic acid, may be successfully achieved. The catalyst may be utilized in supported or unsupported form. If utilized in supported form, any method may be used for preparing the supported catalyst. For example, the supported catalyst may be produced by impregnation of the support, or deposition on the support. The supported catalyst generally comprises up to about 50% by weight of catalyst, preferably up to about 20% by weight of catalyst. Any suitable support material may be utilized. For examples, supports that may be used herein include, but are not limited to, alumina, titania, silica, zirconiz, carbons, carbon blacks, graphites, silicates, zeolites, aluminosilicate, and the like.

The oxidation process is carried out either in liquid phase or gas phase. If a liquid phase is used, the liquid phase includes water, organic solvents that are not oxidized in the process, such as any aliphatic or aromatic hydrocarbons, halogenated aliphatic or aromatic hydrocarbons, ketones, esters, and ethers, and mixtures of water and organic solvents.

The oxidation process may be carried out batch wise, semi-continuously, or continuously. The process may be carried out in any suitable apparatus. Exemplary of such apparatus are stirred tank reactors, trickle-bed reactors, reaction columns, high- pressure reactors, and the like. The oxidation process of the present invention is generally carried out at a temperature ranging from about 2O ⁰ C to about 45O ⁰ C, more particularly from about 100 ⁰ C to about 250 ⁰ C. Further, the oxidation process of the present invention is generally carried out in a pressure range of from about atmospheric pressure to about 1000 psi (pound per square inch), and preferably, in a pressure range of from about atmospheric pressure to about 500 psi. There is no specific residence time required for the process of the present invention, other than the residence time be adequate to allow the intended product to be produced. The residence time for the process of the present invention ranges from 1 to 10 hours, in general.

Any known process for producing lactide may be used herein to obtain the lactide utilized in producing the products described herein.

Moreover, the present invention provides novel processes for preparing a lactide. In one embodiment, the novel process for producing lactide includes ammonium lactate fermentation, extractive salt splitting and direct distillation operations. In another embodiment, the novel process for producing lactide includes calcium lactate fermentation, salt swapping, extractive salt splitting and direct distillation. The novel processes are described in detail as follows.

In the process for preparing the lactide, there is first produced lactic acid. The lactic acid is produced by fermentation of a sugar, such as dextrose, sucrose, or polysaccharides such as a starch, in a typical fermentation reactor, in the presence of a suitable microorganism. Any suitable microorganism can be used that results in the preparation of a fermentation broth containing lactic acid. Exemplary microorganisms include, but are not limited to, some of the Lactobacillus genus, the Streptococcus genus, the Rhizopus genus, the Bacillus genus, and the Leuconostoc genus. The lactic acid produced in the fermentation reactor is neutralized by reaction with ammonia and ammonium hydroxide, or calcium hydroxide, calcium oxide, and calcium carbonate, to produce ammonium lactate, or calcium lactate.

In one embodiment, during the fermentation process for production of ammonium lactate, biomass is formed. The biomass is removed by any suitable technique, such as, for example, by flocculation and filtration. Color bodies, if formed, are removed by any technique, such as by use of activated carbon or ion exchange resins. To the ammonium lactate broth there is added an organic extractant followed by heating to split the ammonium lactate to lactic acid and ammonia.

Suitable organic extractants are capable of dissolving the lactic acid. In addition, the extractants in another embodiment have boiling points sufficiently high that boil-off during the process for recovering the lactic acid, is avoided. One class of useful extractants includes organic amines that are immiscible in water. Preferably, the amines have a total of at least 18 carbon atoms. The amines also preferably have boiling points greater than 100 ⁰ C (measured at a pressure of 1 atmosphere) and more preferably greater than 175°C (measured at a pressure of 1 atmosphere). Primary, secondary, and tertiary amines, as well as quaternary amine salts, can be used, with tertiary amines being preferred. The nitrogen atom of the amine may be substituted with groups including alkyl, aryl (e.g., phenyl), and aralkyl (e.g. benzyl) groups. These groups, in turn, may be straight chain or branched, and may be substituted or unsubstituted. Examples of substituted groups include halogenated groups (e.g., hydroxyalkyl groups such as hydroxyethyl and hydroxypropyl). The groups may be the same as, or different from, each other.

Alkyl groups are preferred, particularly higher alkyl groups (e.g., having at least 8 carbon atoms, and preferably between 8 and 14 carbon atoms, inclusive). Examples of useful alkyl amines include trialkyl amines such as trioctyl amine, tridecyl amine, tridodecyl amine, and combinations thereof. A second class of useful extractants includes solvating extractants such as carbon- oxygen extractants, phosphorus-oxygen extractants, phosphine sulfide extractants, and alkyl sulfide extractants. Specific examples of useful carbon-oxygen extractants include alcohols (e.g., alkyl alcohols having between 8 and 14 carbon atoms, inclusive, such as octanol, decanol, and dodecanol), ethers (e.g., alkyl ethers such as dibutylcarbitol), ketones (e.g. decanone), and amides (e.g., N, N-dialkyl amides such as N, N-dibutyl formamide, N, N-dibutyl acetamide, N, N-dibutyl propionamide, N,N-dipropyl propionamide, and N, N-di-n-butyl lactamides). Specific examples of useful phosphorus-

oxygen extractants include phosphorus esters (e.g., alkyl phosphates such as tri-n- butylphosphate, dibutylbutylphosphonate, and dimethylmethylphosphonate), and phosphine oxides, (e.g., tri-n-octylphophine oxide). Specific examples of useful phosphine sulfides include tri-isobutylphosphine sulfide. Specific examples of useful alkly sulfides include dihexyl sulfide and diheptyl sulfide.

Any of the above-described extractants may be used alone or in combination. For example, it may be useful to combine an organic amine extractant with an alkyl alcohol having between 8 and 14 carbon atoms, inclusive. The alcohol facilitates separation of the acid during the extractive salt-splitting process. The fermentation broth in the presence of the organic extractant is heated to split the ammonium salt and thereby produce the acid in combination with the organic extractant and other fermentation broth contents. The temperature should be high enough to accomplish salt splitting efficiently, yet below the temperature at which the lactic acid, organic extractant, or both decompose or otherwise degrade. In general, suitable reaction temperatures range from about 20°C to about 200°C, with temperatures in the range from about 110°C to about 12O ⁰ C, and about 40 ⁰ C to about 120 ⁰ C being preferred. The reaction may be carried out at atmospheric pressure or under reduced pressure such as 100 mm Hg. Reduced pressures are preferred because they enable lower reaction temperatures to be used. The salt-splitting reaction produces ammonia as a by-product, which is then separated and removed from the reactor, e.g., by heating, applying a vacuum, adding an inert gas such as nitrogen, or a combination thereof to strip the ammonia from the remainder of the reaction mixture. If desired, the ammonia may be recycled and added to the fermentation reactor. The above procedure may be referred to as an extractive salt-splitting process to produce lactic acid. As described, the extractive salt-splitting process combines salt- splitting and extraction, in the presence of an extractant. The ammonium lactate is split to lactic acid and ammonia. The split lactic acid is extracted into an extractant phase and released ammonia is stripped from the system. The removed ammonia is recovered and recycled to the fermentation process.

The lactic acid and extractant combination is then distilled as described herein in the presence of a suitable catalyst to produce a lactide. The separated extractant may be recycled to the extractive salt-splitting process.

In the present process, lactide is produced from the lactic acid loaded extractant, in the presence of a catalyst, in that the lactide is obtained by distillation. The catalyst used in the lactide production from lactic acid loaded extractant may comprise at least one metal or metal compound selected from a group consisting of IA group, HA group, HIA group, IVA group, VA group, IB group, IEB group, IVB group, VB group, VD3 group, VHB group, VHI group in the periodic table, or mixtures thereof. For a catalyst comprising a metal or metal compound selected from IA group, examples include a hydroxide, such as sodium hydroxide, potassium hydroxide, and lithium hydroxide, salts of the metals with weak acid, such as sodium lactate, sodium acetate, sodium citrate, sodium carbonate, sodium butyrate, sodium stearate, sodium octylate, potassium lactate, potassium acetate, potassium stearate, potassium octylate, and alkoxides of the metals, such as sodium methoxide, sodium ethoxide, potassium methoxide and potassium ethoxide, and mixtures thereof.

For a catalyst comprising a metal or metal compound selected from HA group, examples include a hydroxide, such as calcium hydroxide, magnesium hydroxide, an oxide such as calcium oxide, potassium oxide, a salt with organic acid, such as, calcium lactate, calcium acetate, calcium citrate, potassium lactate and a mixture thereof.

For a catalyst comprising a metal or metal compound selected from HIA group, examples include an oxide, such as aluminum oxide, gallium oxide, a salt with organic acid, such as aluminum lactate and a mixture thereof.

For a catalyst comprising a metal or metal compound selected from IVA group, examples include tin dust, tin halide, an oxide, such as tin oxide, silicon oxide, germanium oxide, organic tin compound derived from organic acids, such as tin lactate, tin acetate, tin butyrate, tin octylate, tin tartrate, tin stearate, tin oleate, butyltin, and a mixture thereof. For a catalyst comprising a metal or metal compound selected from VA group, examples include an oxide, such as antimony oxide, and bismuth oxide, and a mixture thereof.

For a catalyst comprising a metal or metal compound selected from IB group, examples include an oxide, such as cupper oxide, silver oxide, and a salt with organic acid, such as cupper lactate, and mixtures thereof.

For a catalyst comprising a metal or metal compound selected from IDB group, examples include zinc oxide, zinc halide and organic zinc compound, such as zinc lactate, zinc acetate and zinc octylate, and mixtures thereof.

For a catalyst comprising a metal or metal compound selected from IVB group, examples include an oxide, such as titanium oxide, zirconium oxide, and organic titanium or zirconium compounds such as tetrapropyl titanate, zirconium isopropoxide, and mixtures thereof.

For a catalyst comprising a metal or metal compound selected from VB group, examples include an oxide such as vanadium oxide, niobium oxide and a salt with organic acid such as vanadium lactate and niobium lactate, and mixtures thereof.

For a catalyst comprising a metal or metal compound selected from VIB group, examples include an oxide, such as chromium oxide, molybdenum oxide, tungsten oxide, and a salt with organic acid such as molybdenum lactate, and mixtures thereof.

For a catalyst comprising a metal or metal compound selected from VIIB group, examples include an oxide, such as manganese oxide, rhenium oxide and a salt with organic acid such as manganese lactate, and mixtures thereof. For a catalyst comprising a metal or metal compound selected from VII group, examples include an oxide, such as iron oxide, cobalt oxide, nickel oxide, ruthenium oxide, rhodium oxide, and a salt with organic acid such as iron lactate, cobalt lactate and nickel lactate, and mixtures thereof.

The process of lactide formation and distillation from the lactic acid loaded extractant, may be carried out batch wise, semi-continuously, or continuously.

Furthermore, the lactide formation and distillation may be carried out in any conventional distillation apparatus, or passed through a distillation column packed with catalyst, preferably at a reduced pressure of about 0.01 to about 100 mm Hg, and preferably at an elevated temperature of about 14O ⁰ C to about 200°C. The lactide may be collected fractionally with water generated from the formation of the lactide from the lactic acid loaded extractant at the top part of the distillation column, and the extractant may be

collected at the bottom of the distillation column. The extractant may be recycled to the extractive salt-splitting stage for reuse.

The process for lactide formation and distillation may be carried out generally at a temperature ranging from about 50 ⁰ C to about 300°C, preferably from about 100°C to about 200 ⁰ C. The process for lactide formation is preferably carried out at a pressure ranging from about 0.01 mm Hg to atmospheric pressure. There is no specific residence time required for the process, other than the residence time be adequate to allow the intended product to be produced. Preferably, the residence time for the process ranges from about 0.1 to about 10 hours. If desired, the lactide produced from the lactic acid, by distillation, can be purified. The purification may be carried out by re-crystallization in an organic solvent, such as, for example, ketone. Alternatively, the lactide may be washed with the organic solvent to further purify the lactide.

In another embodiment, lactic acid is produced by a method that involves production of calcium lactate by fermentation. The lactic acid is produced from the calcium lactate by a method that also comprises a salt swapping process, an extractive salt splitting process, and a distillation process.

The salt swapping process involves changing one salt to another salt by reaction with a salt swap agent. In the present embodiments, the salt swapping process involves converting calcium lactate in the fermentation broth to ammonium lactate or alkyl ammonium lactate, by reacting the calcium lactate in the broth with a combination of ammonia and carbon dioxide gases, ammonium bicarbonate, ammonium carbonate, or a mixture of an at least partially water soluble amine and carbon dioxide. It is advantageous to react the calcium lactate in the broth with a mixture of an at least partially water soluble amine and carbon dioxide, to produce an alkyl ammonium lactate and calcium carbonate. It is easier to handle the amine, rather than ammonia. Further, an alkyl ammonium lactate can be split at milder conditions of temperature and pressure, to lactic acid and an amine in the extractive salt splitting process as compared to ammonium lactate. Most of the at least partially water soluble amines are liquid at ambient temperature, and are easier to handle than ammonia gas. Any at least partially water soluble amines may be used in the salt swapping process. For example, suitable amines include, but are not limited to, methylamine, ethylamine, butylamine, ethanolamine, dimethylamine, diethylamine, dibutylamine,

methylethanolamine, trimethylamine, triethylamine, diaminopropane, diaminobutane, piperazine, and the like.

The salt swap process may be carried out, under any conditions, by mixing the reactants. The salt swap reaction may be carried out batch wise, semi-continuously, or continuously. The salt swap process of the present invention may be carried out in any suitable apparatus. Exemplary of such apparatus are stirred tank reactors and column type reactors. There is no specific residence time required for the process of the present invention, other than the residence time be adequate to allow the intended product to be produced. More particularly, the residence time for the process of the present invention ranges from 1 minute to 4 hours.

The extractive salt splitting involves splitting an ammonium lactate or an alkyl ammonium lactate into lactic acid, and ammonia or an amine, in the presence of an organic extractant. The extractive salt splitting may be carried out in a conventional distillation device or by using a wipe-film distillation device or a short pass distillation device at reduced pressure and elevated temperature. The extractive salt splitting process may also be carried out by using steam stripping or gas stripping at elevated temperature. Any organic extractant that is capable of dissolving the lactic acid may be used in the extractive salt splitting process herein. Examples of suitable extractants are, but not limited to, the following extractants. One class of useful extractants includes organic amines that are immiscible in water. Preferably, the amines have a total of at least 18 carbon atoms. The amines may have boiling points greater than 100°C (measure at a pressure of 1 atmosphere) or more preferably, greater than 175°C (measured at a pressure of 1 atmosphere). Primary, secondary, and tertiary amines, as well as quaternary amine salts, can be used, with tertiary amines being preferred. The nitrogen atom of the amine may be substituted with groups including alkyl, and aryl (e.g., benzyl) groups. These groups, in turn, may be straight chain or branched, and may be substituted or unsubstituted. Examples of substituted groups include halogenated groups (e.g., halogenated alkyl groups) and hydroxyl-containing groups (e.g., hydroxyalkyl groups such as hydroxyethyl and hydroxypropyl). The groups may be the same as, or different from, each other.

Alkyl groups are preferred, particularly higher alkyl groups (e.g., having at least 8 carbon atoms, and preferably from 8 to 14 carbon atoms). Examples of useful alkyl

amines include trialkyl amines such as trioctyl amine, tridecyl amine, tridodecyl amine, and combinations thereof.

A second class of useful extractants includes solvating extractants such as carbon- oxygen extractants, phosphorus-oxygen extractants, pjosphine sulfide extractants, and alkyl sulfide extractants. Specific examples of useful carbon-oxygen extractants include alcohols (e.g., alkyl alcohols having from 8 to 14 carbon atoms, such as octanol, decanol, and dodecanol), ethers (e.g., alkyl ethers such as dibutylcarbitol), ketones (e.g., decanone), esters (e.g. octyl lactate, decyl lactate, and trioctyl timellitate) and amides (e.g., N,N- dialkyl amides such as N,N-dibutyl formanide, N,N-dibutyl acetamide, N,N-dibutyl propionamide, N,N-dipropyl propionamide, and N,N-di-n-butyl lactamide). Specific examples of useful phosphorus-oxygen extractants include phosphorus esters (e.g., alkyl phosphates such as tri-n-butylphosphate, dibutylbutylphosphonate, and dimethylmethylphosphonate(, andphosphine oxides (e.g., tri-n-octylphosphine oxide). Specific examples of useful phosphine sulfides include tri-isobutylphosphine sulfide. Specific examples of useful alkyl sulfides include dihexyl sulfide and diheptyl sulfide.

Any of the above-describe extractants may be used alone or in combination with other components. For example, it may be useful to combine an organic amine extractant with an alkyl alcohol having from 8 to 14 carbon atoms. The alcohol facilitates separation of the acid during the extractive salt-splitting process. If necessary, diluent can be used with the extractant to reduce the viscosity of the organic phase. Enhancers, such as octanol, decanol, or dodecanol, may be also be added to increase the acid extraction.

Ammonium lactate or alkyl ammonium lactate in the broth is heated in the presence of the organic extractant to split the ammonium lactate or alkyl ammonium lactate and thereby produce the lactic acid in combination with the organic extractant and other fermentation broth contents. The reaction temperature and time are selected based upon the lactic acid reactant. The temperature should be high enough to accomplich salt splitting efficiently, yet below the temperature at which the lactic acid, organic extractant, or both decompose or otherwise degrade. In general, suitable reaction temperatures range from about 2O ⁰ C to about 200°C, with temperatures in the range from about 40°C to about 120°C being preferred. The reaction may be carried out at atmospheric pressure or under reduced pressure, preferably less than 100mm Hg. Reduced pressures are preferred because the enable lower reaction temperatures to be used.

The extractive salt-splitting reaction produces ammonia or an amine as a byproduct, which is then separated and removed from the reactor, e.g., by heating, applying a vacuum, adding an inert gas such as nitrogen, or a combination thereof to strip the ammonia or amine from the remainder of the reaction mixture. If desired, the ammonia or amine may be recycled.

The above procedure may be referred to as an extractive salt-splitting technique to produce lactic acid. As described, the extractive salt-splitting process combines salt- splitting and extraction, in the presence of an extractant. The ammonium lactate is split to lactic acid and ammonia. The split lactic acid is extracted into an extractant phase and released ammonia is stripped from the system. The removed ammonia is recovered and recycled to the fermentation process.

The lactic acid-extractant combination is then distilled as described herein in the presence of a suitable catalyst to produce a lactide. The separated extractant may be recycled to the estractive salt-splitting process. In the present process, lactide is produced from the lactic acid loaded extractant, in the presence of a catalyst, in that the lactide is obtained by distillation. The catalyst used in the lactide production from lactic acid loaded extractant may comprise at least one metal or metal compound selected from a group consisting of IA group, HA group, IIIA group, IVA group, VA group, IB group, IIB group IVB group, VB group, VIB group, VIIB group, VBIII group in the periodic table, or mixtures thereof.

For the catalyst comprising a metal or metal compound selected from IA group, examples include a hydroxide, such as sodium hydroxide, potassium hydroxide, and lithium hydroxide, salts of the metals with weak acid, such as sodium lactate, sodium acetate, sodium citrate, sodium carbonate, sodium butyrate, sodium stearate, sodium octylate, potassium lactate, potassium acetate, potassium stearate, potassium octylate, and alkoxides of the metals, such as sodium methoxide, sodium ethocide, potassium methoxide and potassium ethoxide, and mixtures thereof.

For a catalyst comprising a metal or metal compound selected from EA group, examples include a hydroxide, such as calcium hydroxide, magnesium hydroxide, an oxide such as calcium oxide, potassium oxide, a salt with organic acid, such as, calcium lactate, calcium acetate, calcium citrate, potassium lactate and a mixture thereof.

For a catalyst comprising a metal or metal compound selected from IDA group, examples include an oxide, such as aluminum oxide, gallium oxide, a salt with organic acid, such as aluminum lactate and a mixture thereof.

For a catalyst comprising a metal or metal compound selected from IVA group, examples include tin dust, tin halide, an oxide, such as tin oxide, silicon oxide, germanium oxide, organic tin compound derived from organic acids, such as tin lactate, tin acetate, tin butyrate, tin octylate, tin tartrate, tin stearate, tin oleate, butyltin, and a mixture thereof.

For a catalyst comprising a metal or metal compound selected from VA group, examples include an oxide, such as antimony oxide, and bismuth oxide, a mixture thereof. For a catalyst comprising a metal or metal compound selected from IB group, examples include an oxide, such as copper oxide, silver oxide, and a salt with organic acid, such as copper lactate, and mixtures thereof.

For a catalyst comprising a metal or metal compound selected from HB group, examples include zinc oxide, zinc halide and organic zinc compound, such as zinc lactate, zinc acetate and zinc octylate, and mixtures thereof.

For a catalyst comprising a metal or metal compound selected form IVB group, examples include an oxide, such as titanium oxide, zirconium oxide, and organic titanium or zirconium compounds such as tetrapropyl titanate, zirconium isopropoxide, and mixtures thereof. For a catalyst comprising a metal or metal compound selected from VB group, examples include an oxide such as vanadium oxide, niobium oxide and a salt with organic acid such as vanadium lactate and niobium lactate, and mixtures thereof.

For a catalyst comprising a metal or metal compound selected from VIB group, examples include an oxide, such a chromium oxide, molybdenum oxide, tungsten oxide, and a salt with organic acid such as molybdenum lactate, and mixtures thereof.

For a catalyst comprising a metal or metal compound selected from VIIB group, examples include an oxide, such as manganese oxide, rhenium oxide and a salt with organic acid such as manganese lactate, and mixtures thereof.

For a catalyst comprising a metal or metal compound selected from VII group, examples include an oxide, such as iron oxide, cobalt oxide, nickel oxide, ruthenium oxide, rhodium oxide, and a salt with organic acid such as iron lactate, cobalt lactate and nickel lactate, and mixtures thereof.

The process of lactide formation and distillation from the lactic acid loaded extractant, may be carried out batch wise, semi-continuously, or continuously. Furthermore, the lactide formation and distillation may be carried out in any conventional distillation apparatus, or passed through a distillation column packed with catalyst, preferably at a reduced pressure of about 10 to about 100mm Hg, and preferably at an elevated temperature of about 140°C to about 200°C. The lactide is collected fractionally with water generated from the formation of the lactide from the lactic acid loaded extractant at the top part of the distillation column, and the extractant is collected at the bottom of the distillation column. The extractant may be recycled to the extractive salt- splitting stage for reuse.

The process for lactide formation and distillation is carried out generally at a temperature ranging from about 50°C to about 300°C, preferably form about 100°C to about 200°C. The process is preferably carried out at a pressure ranging from about 0.01mm Hg to atmospheric pressure. There is no specific residence time required for the process, other than the residence time be adequate to allow the intended product to be produced. Preferably, the residence time for the process ranges from about 0.1 to about 10 hours. If desired, the lactide produced from the lactic acid, by distillation, can be purified. The purification may be carried out by re-crystallization in an organic solvent, such as , for example, an alcohol, an ether, or a ketome. Alternatively, the lactide may be washed with the organic solvent to further purify the lactide.

The present processes for producing lactide have been found to be advantageous relative to a known process for producing lactide. According to the known process, lactide is produced by the dehydration of lactic acid to form linear polyesters of lactic acid or polylactic acid. Then, lactide is distilled from the polylactic acid, under reduced pressure and at elevated temperatures of about 140°C to about 200 ⁰ C in the presence of a catalyst. This is considered a reversible depolymerization of the linear polyesters. The known process for producing lactide involves calcium lactate fermentation, acidification, filtration of solids from solution, washing of solids, evaporation, lactic acid extraction, and back extraction, entrainment removing, ion exchanging, dehydration to polylactic acid, and lactide distillation. This is a lengthy and expensive process. Moreover, the known process involves calcium sulfate (or gypsum) waste material, is costly in terms of chemical usage, such as calcium oxide, calcium hydroxide, and sulfuric acid, requires

handling of gypsum waste, such as filtration and solid wash, loss of lactic acid in the solid waste, large amount of water evaporation, and disposal of the waste.

By contrast, the present processes for producing the lactide, that may be used in preparing derivatives of lactide, is short, simple and economically improved. Among the various advantages of the present processes, there have been provided methods for producing lactides from lactic acid, without having to form a polyester of the lactic acid or polylactic acid, as part of the process.

It is expected that the lactides produced by the processes described herein will be suitable for use in any application where lactides are presently utilized. In particular, it is expected that the lactide produced by the present processes described herein will be suitable for use in some food applications as for example, a food preservative, a pH regulating agent, a coagulating agent, an acidulant, and an auxiliary expanding agent.

Moreover, the lactide produced by the novel processes described herein may be utilized in the preparation of high molecular weight polylactide, polymers, or lactide copolymers. The polymers and copolymers may be produced using any technique known in the art for producing the polymers and copolymers from lactides.

Typically, lactide is fed to a polymerization reactor in the presence of catalyst at elevated temperature to produce the polylactide polymers. Optionally, a non-lactide monomer may be added with lactide to the polymerization reactor to produce the copolymer. Many copolymers of polylactide are known to the art, for example, copolymers with glycolide, γ-butyrolactone, β-caprolactone, α-hydroxybutyric acid, α- hydroxyvaleric acid, α-hydroxycaproic acid, α-hydroxyoctanoic acid, and the like.

The polymerization reactor can be a stirred tank rector, capable of operating at elevated temperature ranging from 100 ⁰ C to 25O ⁰ C, preferably from 15O ⁰ C to 200 ⁰ C, and a pressure ranging from below atmospheric pressure to 100 psi (pound per square inch), preferably from atmosphere pressure to 50 psi. The catalyst used in the polymerization of lactide may be any suitable polymerization catalyst, such as alumina, silica, zirconia, organic aluminum compounds and organic tin compounds.

The invention has been described with reference to various specific and illustrative embodiments and techniques. However, one skilled in the art will recognize that many variations and modifications may be made while remaining within the spirit and scope of the invention.