Extrusion process for the preparation of alkali metal carbonate, bicarbonate and sesquicarbonate formulations using a dissolved functionalizing agent

Abstract

A process for preparing a formulation comprising an alkali metal salt selected from the group consisting of alkali metal bicarbonate salts, alkali metal carbonate salts, alkali metal sesquicarbonate salts and combinations thereof, wherein said process includes: (a) dissolving a functionalizing agent in a solvent; (b) mixing the alkali metal salt with the solution comprising the functionalizing agent that a paste-like composition is formed; (c) extruding the paste-like composition to obtain filaments or granules; (d) at least partially removing the solvent from the filaments or granules. A powder, filaments and granules are obtainable from said process and may be used in various applications such as in plastic foaming or in food and feed leavening compositions.

Claims

1. A process for preparing a formulation for foaming plastics, the formulation consisting of an alkali metal salt, a functionalizing agent, and optionally water, wherein the alkali metal salt is selected from the group consisting of alkali metal bicarbonate salts, alkali metal sesquicarbonate salts and combinations thereof, wherein said process comprises: (a) dissolving the functionalizing agent in water to obtain a solution, the solution consisting of water and the functionalizing agent in an amount of at least 20 g per 100 g water; (b) mixing the alkali metal salt with the solution in a weight ratio so that a paste-like composition consisting of the alkali metal salt, the functionalizing agent and water, is formed; (c) extruding the paste-like composition to obtain a powder, filaments or granules consisting of water, the alkali metal salt and the functionalizing agent, wherein the alkali metal salt is present in the paste-like composition in an amount of at least 75% by weight; and (d) at least partially removing the water from the powder, filaments or granules to obtain a powder, filaments or granules consisting of the alkali metal salt, the functionalizing agent, and optionally water, wherein the functionalizing agent is a polymer selected from the group consisting of polyvinylalcohol (PVOH), a polyglycol, polyethylene glycol (PEG), a polysaccharide, polyacrylic acid (PAA), poly(acrylic acid-co-maleic acid), polyethylenimine, polyvinylpyrrolidone (PVP), N-(2-Hydroxypropyl) methacrylamide (HPMA), poly-galactomannane, and combinations thereof.

2. The process of claim 1, wherein the polymer is a polysaccharide selected from the group consisting of hydrolyzed starch, carboxymethylcellulose (CMC), arabic gum, carrageenan, guar gum, locust bean gum, xanthan gum, and combinations thereof.

3. The process according to claim 1, wherein the functionalizing agent is PVOH, wherein the solution at step a) consists of 20 to 40 g of PVOH per 100 g of water, and wherein the mixing of the alkali metal salt with the solution of PVOH at step b) is at a weight ratio of at least 1/1 to at most 3/1 of alkali metal salt to the solution.

4. The process according to claim 1, wherein the filaments or granules are further milled.

5. A process for preparing a formulation for foaming plastics, the formulation consisting of an alkali metal salt a functionalizing agent, and optionally water, wherein the alkali metal salt is selected from the group consisting of alkali metal bicarbonate salts, alkali metal sesquicarbonate salts and combinations thereof, wherein said process comprises: (a) dissolving the functionalizing agent in water to obtain a solution comprising the functionalizing agent in an amount of 20 to 40 g per 100 g water; (b) mixing the alkali metal salt with the solution comprising the functionalizing agent in a weight ratio of at least 1/1 to at most 3/1 of alkali metal salt to the solution comprising the functionalizing agent so that a paste-like composition comprising the alkali metal salt and the functionalizing agent is formed; (c) extruding the paste-like composition to obtain a powder, filaments or granules comprising water, the alkali metal salt and the functionalizing agent, wherein the alkali metal salt is present in the paste-like composition undergoing extrusion in an amount of at least 75% by weight; and (d) at least partially removing the water from the powder, filaments or granules to obtain a powder, filaments or granules comprising the alkali metal salt and the functionalizing agent, wherein the functionalizing agent is polyvinylalcohol (PVOH).

6. A process for preparing a formulation for foaming plastics, the formulation comprising sodium bicarbonate, a functionalizing agent, and optionally water, wherein the functionalizing agent increases the CO.sub.2 release beginning temperature and/or the CO.sub.2 release maximum temperature of the sodium bicarbonate when used for foaming plastics, and wherein said process comprises: (a) dissolving the functionalizing agent in water to obtain a solution comprising the functionalizing agent in an amount of at least 20 g per 100 g water; (b) mixing the sodium bicarbonate with the solution comprising the functionalizing agent in a weight ratio so that a paste-like composition comprising the sodium bicarbonate and the functionalizing agent is formed; (c) extruding the paste-like composition to obtain a powder, filaments or granules comprising water, the sodium bicarbonate and the functionalizing agent, wherein the sodium bicarbonate is present in the paste-like composition undergoing extrusion in an amount of at least 75% by weight; and (d) at least partially removing the water from the powder, filaments or granules to obtain a powder, filaments or granules comprising the sodium bicarbonate and the functionalizing agent, wherein the functionalizing agent is polyvinylalcohol (PVOH), wherein the solution at step a) comprises 20 to 40 g of PVOH per 100 g of water, and wherein the mixing of the alkali metal salt with the solution of PVOH at step b) is at a weight ratio of at least 1/1 to at most 3/1 of alkali metal salt to the solution.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) As mentioned above, the present invention relates to a process for preparing a formulation comprising an alkali metal salt selected from the group consisting of alkali metal bicarbonate salts, alkali metal carbonate salts, alkali metal sesquicarbonate salts and combinations thereof, wherein said process comprises: (a) dissolving a functionalizing agent in a solvent to obtain a solution comprising the functionalizing agent; (b) mixing the alkali metal salt with the solution comprising the functionalizing agent in a weight ratio so that a paste-like composition comprising the alkali metal salt and the functionalizing agent is formed; (c) extruding the paste-like composition to obtain a powder, filaments or granules comprising the solvent, the alkali metal salt and the functionalizing agent; (d) at least partially removing the solvent from the powder, filaments or granules to obtain filaments or granules comprising the alkali metal salt and the functionalizing agent.

(2) In a preferred embodiment of the present invention, the functionalizing agent is a polymer selected from the group consisting of polyvinylalcohol (PVOH), a polyglycol, polyethylene glycol (PEG), a polysaccharide, polyacrylic acid (PAA), poly(acrylic acid-co-maleic acid), polyethylenimine, polyvinylpyrrolidone (PVP), N-(2-Hydroxypropyl) methacrylamide (HPMA), poly-galactomannane, and combinations thereof.

(3) The polysaccharide is preferably selected from the group consisting of hydrolyzed starch, carboxymethylcellulose (CMC), arabic gum, carrageenan, guar gum, locust bean gum, xanthan gum (such as e.g., rhodopol), and combinations thereof.

(4) A particularly preferred functionalizing agent is polyvinylalcohol (PVOH).

(5) In a further preferred embodiment of the present invention, the functionalizing agent is a resin acid. The resin acid is preferably a tricyclic diterpene carboxylic acid, preferably belonging to the abietane diterpene group.

(6) In a further preferred embodiment of the invention, the functionalizing agent is an amino-acid. Preferably, the amino acid is selected from the group consisting of selected from the group consisting of casein, gelatin, glycine, proline, hydroxyproline, glutamic acid, alanine, arginine, aspartic acid, lysine, pectin, serine, leucine, valine, phenylalanine, threonine, isoleucine, hydroxylysine, methionine, histidine, tyrosine, and combinations thereof.

(7) The functionalizing agent can also be a water-soluble inorganic salt with the proviso that the water-soluble salt is not sodium silicate. Preferably, the water-soluble inorganic salt is selected from the group consisting of silicates (excluding sodium silicate), NaCl, KCl, MgCl.sub.2, sodium phosphate, borates, nitrates, nitrites, sulfates, sulfites and combinations thereof.

(8) Preferably, the paste-like composition undergoing extrusion comprises 0.1% to 60%, preferably 0.5% to 55%, more preferably 1.0% to 50%, even more preferably 2.0% to 45% by weight of the functionalizing agent. If present in an amount of less than 0.1% by weight, the functionalizing agent is less efficient in terms of the provision of a paste-like composition. More than 60% by weight of the functionalizing agent are disadvantageous for cost reasons.

(9) Preferably, the paste-like composition undergoing extrusion comprises at least 40%, more preferably at least 50%, even more preferably at least 60%, even more preferably at least 65%, even more preferably at least 70%, even more preferably at least 75%, even more preferably at least 80%, and even more preferably at least 85% by weight of the alkali metal salt.

(10) The alkali metal salt is preferably a bicarbonate or a sesquicarbonate salt, in particular sodium bicarbonate or sodium sesquicarbonate. Particularly preferred is sodium bicarbonate.

(11) The alkali metal salt particles preferably have a medium particle size (D50 in weight) of less than 300 ?m, preferably less than 200 ?m, more preferably less than 130 ?m. The particles typically have a medium particle size (D50 in weight) of at least 10 ?m, or at least 20 ?m, or at least 30 ?m, or at least 40 ?m, or at least 50 ?m. The medium particle size (D50 in weight) of the particles may range from 10-300 ?m, or 20-200 ?m, or 30-150 ?m, or 50-130 ?m. The particle size distribution can be determined according to ISO 13320. For example, the weight-average diameter D50 value can be measured by laser diffraction and scattering on a Malvern Mastersizer S particle size analyser using an HeNe laser source having a wavelength of 632.8 nm and a diameter of 18 mm, a measurement cell equipped with a backscatter 300 mm lens (300 RF), and MS 17 liquid preparation unit, and an automatic solvent filtration kit (ethanol kit) using ethanol saturated with the alkali metal salt (wet method).

(12) The solvent of the process of the present invention is selected from the group consisting of methanol, ethanol and water. Preferably, the solvent is water.

(13) In a preferred embodiment of the invention, the solution comprising the functionalizing agent at step a) comprises at least 5 g, more preferably at least 10 g, even more preferably at least 20 g of the functionalizing agent per 100 g of water.

(14) In a further preferred embodiment of the process of the present invention, the solution comprising the functionalizing agent at step a) comprises at most 100 g, more preferably at most 50 g, even more preferably at most 40 g of the functionalizing agent per 100 g of water.

(15) Preferably, the weight ratio of alkali metal salt particles to the solution comprising the functionalizing agent is at least 1/3 to at most 4/1, more preferably at least 1/1 to at most 4/1, even more preferably 1/1 to at most 3/1.

(16) In a particularly preferred process of the present invention, the functionalizing agent is PVOH, and the solution comprising the functionalizing agent at step a) comprises 20 to 40 g of PVOH per 100 g of water, and the mixing of the alkali metal salt particles with the solution of PVOH at step b) is at a weight ratio of at least 1/1 to at most 3/1 of alkali metal salt particles to the solution comprising the functionalizing agent. If functionalizing agent, water and alkali metal salts are used in these amounts and ratios, a paste-like composition is obtained that shows excellent homogeneity.

(17) Preferably, at step (b), a third compound selected among a mineral compound, an organic compound, and mixtures thereof, is added to the alkali metal salt or to the solution comprising the functionalizing agent to obtain the paste-like composition.

(18) The mineral compound is preferably silica, zeolite, calcium carbonate, and/or the organic compound is preferably citric acid.

(19) In the process for preparing an alkali metal bicarbonate formulation by extrusion, all suitable extrusion procedures as known in the art can be used.

(20) The extrusion step (c) of the present invention is preferably performed on a screw extruder, or a twin screw extruder.

(21) After extrusion, the solvent is at least partially removed from the powder, filaments or granules obtained from the extrusion process. The removal of the solvent is preferably performed at a temperature higher than 50? C.

(22) The process of the present invention allows the control of the shape and size of the resulting formulation, which can be obtained as a powder, or as filaments or granules as described above. The ability to control shape and size of the alkali metal bicarbonate formulation of the present invention is advantageous with respect to the various applications of alkali metal bicarbonates as known in the art. Preferably, the granules or filaments obtained by the process of the present invention have a diameter of 100 ?m to 100 mm, more preferably of 200 ?m to 50 mm, even more preferably 500 ?m to 5 mm, or of 1 mm to 2 mm.

(23) Powders obtained from the extrusion process or by further milling the filaments or granules obtained from the extrusion process comprise particles with a medium particle size (D50 in weight) in the range of 1 ?m to 2 mm, preferably of 10 ?m to 500 ?m. The particle size distribution can be determined according to ISO 13320.

(24) The present invention furthermore relates to a powder, granules or filaments comprising a functionalizing agent and an alkali metal salt selected from the group consisting of alkali metal bicarbonate salts, alkali metal carbonate salts, alkali metal sesquicarbonate salts and combinations thereof, preferably obtainable by the process as described above.

(25) Preferably, the powder, granules or filaments comprise at least 40%, more preferably at least 50%, even more preferably at least 60%, even more preferably at least 65%, even more preferably at least 70%, even more preferably at least 75%, even more preferably at least 80%, and even more preferably at least 85% by weight of the alkali metal salt, and 0.1% to 60%, preferably 0.5% to 55%, more preferably 1.0% to 50%, even more preferably 2.0% to 45% by weight of the functionalizing agent, and at most 49.9%, preferably at most 24.9%, more preferably at most 14.9% by weight of water.

(26) Preferably, the granules or filaments of the present invention have a diameter of 100 ?m to 100 mm, more preferably of 200 ?m to 50 mm, even more preferably 500 ?m to 5 mm, or of 1 mm to 2 mm. The length-to-diameter ratio of the filaments or granules may range from about 0.4 to about 4.

(27) Preferably, the powder, granules or filaments of the present invention comprise at least 40% by weight of alkali metal bicarbonate, at least 5% and at most 55% by weight of PVOH, and at most 55% by weight of water.

(28) Preferably, the alkali metal salt is a bicarbonate or a sesquicarbonate salt, particularly a sodium bicarbonate or sodium sesquicarbonate. Particularly preferred is sodium bicarbonate.

(29) The powder, granules or filaments obtainable by the process of the invention show an excellently increased dissolution time. The powder, granules or filaments of the present invention show a dissolution time of at least 30 seconds, preferably at least 100 seconds, more preferably at least 200 seconds.

(30) The powder, granules or filaments obtainable from the processes of the invention also show excellent CO.sub.2 release properties. CO.sub.2 release of the formulation obtained from the process of the present invention begins at a temperature of at least 120? C., preferably at a temperature of at least 125? C., more preferably at a temperature of at least 130? C., even more preferably at a temperature of at least 135? C., and particularly preferably at a temperature of at least 140? C., as determined by the TGA method described above. The CO.sub.2 release typically has its maximum at a temperature of at least 150? C., preferably at a temperature of at least 155? C., more preferably at a temperature of at least 160? C., even more preferably at a temperature of at least 165? C., and particularly preferably at a temperature of at least 170? C., as determined by the TGA method described above.

(31) These advantageous properties of the formulation as described above and as obtainable by the process of the invention make it possible to envisage various applications for this alkali metal bicarbonate formulation. The present invention therefore further relates to the use of the powder, granules and filaments as described above, in plastic processing, plastic foaming, flue gas cleaning, pharmaceutical or cosmetics compositions, detergency compositions, food and feed leavening compositions, food and feed supplement additive or food and feed pH buffer in particular for aquatic animal or for fish.

(32) The following examples are given by way of non-limiting illustration of the present invention, and variations thereof that are readily accessible to a person skilled in the art.

EXAMPLES

Example 1: Determination of the Optimal Ratio of Functionalizing Agent, Water and Alkali Metal Salt

(33) Polyvinylalcohol (KURARAY, Poval 4-88) was mixed with water at room temperature (20 to 30? C.) and stirred for 2 h. Sodium bicarbonate (SOLVAY BICAR? TEC 0/13) was added to the polyvinylalcohol solution while continuing stirring for another 10 minutes. The homogeneity of the resulting paste-like compositions was determined as indicated in Table 1 below. + means excellent homogeneity, ? means acceptable homogeneity.

(34) TABLE-US-00001 TABLE 1 Sodium Homogeneity PVOH Water Bicarbonate of the Entry [%] [%] [%] composition 1 5 20 75 + 2 5 45 50 ? 3 10 40 50 + 4 10 65 25 ?

(35) The compositions obtained in entries 1 and 3 were paste-like and showed excellent homogeneity. The polyvinylalkohol concentration in both formulations was 25 g per 100 g water, and the ratio of PVOH solution and sodium bicarbonate was 1/3 (entry 1) and 1/1 (entry 3), respectively.

Example 2: Flow Resistance and Friability of Extrusion Products

(36) Polyvinylalcohol (KURARAY, Poval 4-88) was mixed with water at room temperature (20 to 30)? C. and stirred for 2 h. Different amounts of sodium bicarbonate were added to the polyvinylalcohol solution while stirring for another 10 minutes to obtain three paste compositions (compositions 1 to 3). The composition of compositions 1 to 3 is shown in the following Table 2.

(37) TABLE-US-00002 TABLE 2 Water PVOH Bicarbonate PVOH Bicarbonate Composition [g] [g] [g] [%] [%] 1 40 10 100 6.67 66.67 2 40 10 150 5.00 75.00 3 40 10 200 4.00 80.00

(38) Compositions 1 to 3 were submitted to extrusion using a syringe. The extrusion products were investigated with respect to their flow resistance and friability. The results are shown in the following Table 3, wherein ++ means excellent. + means very good, ? means acceptable.

(39) TABLE-US-00003 TABLE 3 Flow Composition resistance Friability 1 ? ? 2 + + 3 ++ ++

(40) Extrusion products with very good and excellent flow resistance and friability were particularly obtained with compositions 2 and 3 wherein the amount of bicarbonate was 75% and 80% by weight, respectively.

Example 3: Dissolution Time and CO.SUB.2 .Release of Extrusion Products

(41) 10 g polyvinylalcohol (KURARAY, Poval 4-88) were dissolved in 40 ml of water at room temperature (20 to 30)? C. while stirring for 2 h until complete dissolution of the polyvinylalcohol was achieved. 200 g of sodium bicarbonate were mixed with the resulting solution, and stirring was continued for 10 minutes, resulting in the formation of a homogenous paste-like composition comprising the sodium bicarbonate and the polyvinylalkohol.

(42) The paste-like composition was submitted to extrusion using a syringe resulting in the formation of filaments 2 mm in diameter that where cut at about 3 to 5 mm in length. Water was subsequently removed from the filaments at a temperature of 60? C.

(43) Dissolution time and CO.sub.2 release temperature of the formulation was determined as described above. The results are given in the following Table 4.

(44) TABLE-US-00004 TABLE 4 Concentration TGA CO.sub.2 TGA CO.sub.2 [g of release release functionalizing beginning maximum Functionalizing agent on kg Dissolution temperature temperature agent formulation] Time [s] [? C.] [? C.] Polyvinyl alcohol 60 203.0 143.1 174.8 TGA method: 35 to 250? C./ 10? C./min

(45) The result obtained in Example 3 shows that dissolution times of more than 200 seconds can be achieved when polyvinylalcohol is used as the functionalizing agent in the extrusion process of the present invention.

(46) The CO.sub.2 release begins at a temperature of approximately 143? C., and has its maximum at approximately 175? C.

Example 4: Decomposition Kinetics

(47) The following Table 5a shows five sodium bicarbonate products (entries 1 to 5) comprising different functionalizing agents that were obtained by the extrusion process according to the invention.

(48) The sodium bicarbonate products according to entries 1 and 2 of Table 5a were obtained by means of extrusion using a syringe. The procedure followed was similar to the procedure described under Example 2, using polyvinylalcohol (PVOH) (entry 1) and rhodopol (entry 2) in the amounts indicated in entries 1 and 2 of Table 5a (based on 200 g of sodium bicarbonate) as the functionalizing agents.

(49) The sodium bicarbonate product according to entry 3 of Table 5a was obtained by means of a continuous mixing/extrusion process. Mass flow amounts of bicarbonate were between 10 and 30 kg/h. Functionalizing agents were added as indicated in the Table 5a (entries 3 10). The temperature applied in the process was between 30 and 100? C. The residence time was between 2 to 20 minutes.

(50) The sodium bicarbonate product according to entry 4 of Table 5a was obtained by means of a continuous mixing/extrusion process, which was carried out as described for the product according to entry 3, using PEG4000 as the functionalizing agent. The resulting product was subsequently milled using a Planetary ball mill providing the product according to entry 4 of Table 5a.

(51) The reference product is SOLVAY BICAR? TEC 0/13 (Table 5, entry 5).

(52) TABLE-US-00005 TABLE 5a Functionalizing Agent Entry Process (FA) [wt. %] 1 Extrusion (syringe) Polyvinylalcohol 10 2 Extrusion (syringe) Rhodopol 0.6 (Xanthan gum family) 3 Extrusion Polyvinylalkohol 5 (continuous mixing/extrusion) 4 Extrusion + PEG4000 10 Milling 5 BICAR? ? ?

(53) Decomposition kinetics of the sodium bicarbonate products indicated in Table 5a were measured by means of a thermal balance analyzer (Moisture Analyzer Mettler Toledo HX204). 2 to 3 g of the product was uniformly spread on an aluminum pan, and put in the moisture analyzer, which was rapidly heated to the desired temperature of 140? C.

(54) t95% [s] is the decomposition time at a temperature T (i.e. 140)? C. where 95% of the final loss is reached at the desired temperature; a [% wt/s] is the line slope between the point of 15% and 95% of the decomposition kinetics at a temperature T (i.e. 140)? C.

(55) The results are given in the following Table 5b.

(56) TABLE-US-00006 TABLE 5b Entry 140? C. t95 [s] 140? C. a [% wt/s] 1 1250 0.026 2 1200 0.026 3 1690 0.024 4 1105 0.030 5 1070 0.030

(57) All the sodium bicarbonate products comprising a functionalizing agent show increased gas release times at temperatures of 140? C. compared to the reference SOLVAY BICAR? TEC 0/13.