CN113603809A - Preparation method of sodium alginate with low ethanol residue - Google Patents
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- CN113603809A CN113603809A CN202111024650.6A CN202111024650A CN113603809A CN 113603809 A CN113603809 A CN 113603809A CN 202111024650 A CN202111024650 A CN 202111024650A CN 113603809 A CN113603809 A CN 113603809A
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- C08B37/00—Preparation of polysaccharides not provided for in groups C08B1/00 - C08B35/00; Derivatives thereof
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- C08B—POLYSACCHARIDES; DERIVATIVES THEREOF
- C08B37/00—Preparation of polysaccharides not provided for in groups C08B1/00 - C08B35/00; Derivatives thereof
- C08B37/006—Heteroglycans, i.e. polysaccharides having more than one sugar residue in the main chain in either alternating or less regular sequence; Gellans; Succinoglycans; Arabinogalactans; Tragacanth or gum tragacanth or traganth from Astragalus; Gum Karaya from Sterculia urens; Gum Ghatti from Anogeissus latifolia; Derivatives thereof
- C08B37/0084—Guluromannuronans, e.g. alginic acid, i.e. D-mannuronic acid and D-guluronic acid units linked with alternating alpha- and beta-1,4-glycosidic bonds; Derivatives thereof, e.g. alginates
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Abstract
The invention discloses a preparation method of sodium alginate with low ethanol residue, belonging to the technical field of chemical product preparation. The method comprises the steps of carrying out neutralization reaction on alginic acid and sodium hydroxide in an ethanol water solution, and then carrying out centrifugation, granulation, first vacuum drying, first rehydration, second vacuum drying, second rehydration, third vacuum drying and third rehydration to obtain the sodium alginate. According to the invention, the residual quantity of ethanol in the sodium alginate can be reduced to below 50ppm by carrying out three times of vacuum drying and two times of rehydration and alcohol removal treatment on the sodium alginate, so that a high-quality sodium alginate product is obtained.
Description
Technical Field
The invention belongs to the technical field of chemical product preparation, and particularly relates to a preparation method of sodium alginate with low ethanol residue.
Background
Sodium alginate has wide application in the fields of food, pharmaceutical preparations, printing and spinning industry, pharmaceutical industry and the like. At present, the preparation method of sodium alginate mainly comprises two methods of solid phase neutralization and liquid phase neutralization. The solid phase neutralization is generally to directly carry out solid stirring neutralization on alginic acid and sodium carbonate or sodium hydroxide, and the reaction has the disadvantages of insufficient uniformity, poor product color difference, more impurities, more residual alkali, poor neutralization uniformity and low quality, and is mainly used for industrial products with low requirements. The high-quality sodium alginate such as food-grade or pharmaceutical-grade sodium alginate is mainly prepared by adopting a liquid phase neutralization method, taking ethanol as a neutralization medium to neutralize alginic acid and sodium hydroxide to generate sodium alginate, and obtaining a product after centrifugal drying. The water content of sodium alginate is required to be controlled below 15% by the national standard, and the water content is generally controlled to be 10-15% in consideration of the drying cost (the lower the water content is, the more difficult the drying is) and the raw material cost. The existing drying technology mainly adopts boiling drying or fluidized bed drying, and directly dries the prepared sodium alginate (the ethanol content is 1000-2000ppm) to the moisture content of below 15%, and the operation leads the ethanol residue in the sodium alginate to be higher (the ethanol residue is 500-1000 ppm). Taking fluidized bed drying as an example, the drying time of sodium alginate is about 20-30min, after drying to the moisture content of below 15%, the ethanol cannot be completely volatilized because the particles also contain certain moisture, and long-time high-temperature drying can cause the viscosity of the product to be reduced and the quality to be unqualified, so that the high-requirement application occasions cannot be met.
Disclosure of Invention
In order to solve the defects in the prior art, the invention provides a preparation method of sodium alginate with low ethanol residue, which can obtain high-quality sodium alginate with low ethanol residue.
The technical scheme of the invention is as follows:
a preparation method of sodium alginate with low ethanol residue comprises the following steps:
(1) vacuum drying the sodium alginate granules prepared by the liquid phase neutralization method to reduce the water content to 8-9%;
(2) introducing saturated water vapor into the dried sodium alginate granules in the step (1) to enable the sodium alginate granules to absorb moisture and rehydrate until the water content is 30%;
(3) vacuum drying the sodium alginate granules subjected to moisture absorption and rehydration in the step (2) to reduce the water content to 5-7%;
(4) introducing air with the humidity of 80% into the dried sodium alginate granules in the step (3) to enable the sodium alginate granules to absorb moisture and rehydrate until the moisture content is 20%;
(5) vacuum drying the sodium alginate granules subjected to moisture absorption and rehydration in the step (4) to reduce the water content to 2-3%;
(6) and (5) introducing air with the humidity of 60% into the dried sodium alginate granules in the step (5) to balance the water content, so that the required water content of the sodium alginate granules is achieved.
On the basis of the scheme, the steps for preparing the sodium alginate particles by the liquid phase neutralization method are as follows:
carrying out neutralization reaction on alginic acid, ethanol water solution and sodium hydroxide according to the mass ratio of 1:1.2-1.5: 0.18-0.23; after the neutralization reaction is finished, centrifuging the reaction solution by using a centrifugal machine, and removing redundant ethanol water solution to obtain sodium alginate with the water content of 50-60%; and then granulating the sodium alginate by using a screw extrusion device to form sodium alginate granules.
In a specific embodiment, the mass ratio of alginic acid, aqueous ethanol solution and sodium hydroxide is 1:1.2: 0.23.
On the basis of the scheme, the water content of the alginic acid is 60-70%.
On the basis of the scheme, the concentration of the ethanol water solution is 65-75%.
On the basis of the above scheme, the sodium hydroxide is 36 DEG BeNaOH.
On the basis of the scheme, the particle size of the sodium alginate particles is 2-3 mm.
On the basis of the scheme, the saturated water vapor is pure normal-temperature saturated water vapor, and the water vapor can be prepared by utilizing an ultrasonic humidifier.
On the basis of the scheme, the temperature of vacuum drying is 70-90 ℃.
In one technical scheme, the preparation method of the sodium alginate with low ethanol residue comprises the following steps:
(1) neutralization
Neutralizing alginic acid with the water content of 60-70%, ethanol water solution with the concentration of 65-75% and sodium hydroxide according to the mass ratio of 1:1.2-1.5: 0.18-0.23;
(2) centrifugation
After the neutralization is finished, centrifuging the reaction solution by using a centrifugal machine, and removing redundant raw materials and ethanol water solution to obtain sodium alginate with the water content of 50-60%;
(3) granulating
Granulating sodium alginate by using a screw extrusion device, wherein the particle size is 2-3 mm;
(4) first vacuum drying
Putting the granulated sodium alginate granules into vacuum drying equipment with a stirring function for vacuum drying, and stopping drying when the water content of the sodium alginate is reduced to 8-9%;
(5) first rehydration
Introducing pure normal-temperature saturated water vapor into the vacuum drying equipment by using a fan, and starting stirring to ensure that the sodium alginate particles absorb moisture and rehydrate, wherein the water content reaches 30%;
(6) second vacuum drying
Carrying out vacuum drying on the sodium alginate granules subjected to the first rehydration in a vacuum drying device, and stopping drying when the water content of the sodium alginate granules is reduced to 5-7%;
(7) second rehydration
Introducing air with the humidity of 80% into a vacuum drying device for moisture absorption and rehydration to enable the water content of the sodium alginate particles to reach 20%;
(8) third vacuum drying
Vacuum drying the sodium alginate granules subjected to the second rehydration in a vacuum drying device, and stopping drying when the water content of the sodium alginate granules is reduced to 2-3%;
(9) third time rehydration
And (3) introducing air with the humidity of 60% into the vacuum drying equipment to carry out moisture balance, so that the sodium alginate particles reach the required moisture content.
The sodium alginate product prepared by the method is a high-quality sodium alginate product, has the ethanol residual quantity of less than 50ppm, and can be applied to the fields of food or medicine.
The invention has the beneficial effects that:
according to the invention, the residual quantity of ethanol in the sodium alginate can be reduced to below 50ppm by carrying out three times of vacuum drying and two times of rehydration and dealcoholization treatments on the sodium alginate, so that a high-quality sodium alginate product is obtained; meanwhile, the vacuum drying can also reduce the drying temperature condition, and prevent the molecular chain from breaking caused by long-time high-temperature drying of the product, thereby avoiding the defects of thermal degradation, quality reduction and the like of the product caused by repeated high-temperature heating, and maximally proving the product quality.
The principle of removing the ethanol residue through vacuum drying is that the vacuum drying can more quickly transfer the water in the particles under the negative pressure state, the ethanol content is reduced, and the saturated steam repeatedly enters and exits the particles to dilute the ethanol residue, so that the ethanol residue of the sodium alginate product is reduced. The effect cannot be achieved by pure vacuum drying, multiple times of rehydration drying are needed, and the low ethanol residue of the sodium alginate can be realized only by taking away ethanol through water migration.
Detailed Description
Terms used in the present invention have generally meanings as commonly understood by one of ordinary skill in the art, unless otherwise specified. The present invention will be described in further detail with reference to the following data in conjunction with specific examples. The following examples are intended to illustrate the invention and are not intended to limit the scope of the invention in any way.
Example 1
100kg of alginic acid with the water content of 60 percent, 120kg of ethanol aqueous solution with the concentration of 65 percent and 23kg of 36 DEG BeNaOH are neutralized; after the neutralization is finished, centrifuging the reaction solution by using a centrifuge at 4000rpm, and removing redundant ethanol aqueous solution to obtain sodium alginate with the water content of about 50%; granulating sodium alginate by using spiral extrusion equipment, wherein the particle size is 3 mm; putting the granulated sodium alginate granules into vacuum drying equipment with a stirring function to carry out vacuum drying at 70 ℃, wherein the vacuum degree is-0.1 MPa, and stopping drying when the water content of the sodium alginate granules is reduced to 8%; detecting the ethanol residue of the sodium alginate granules at the moment to be 900 ppm; introducing pure normal-temperature saturated water vapor into the vacuum drying equipment by using a fan, and starting stirring to ensure that the sodium alginate particles absorb moisture and rehydrate, wherein the water content reaches 30%; vacuum drying the sodium alginate granules subjected to the first rehydration at 70 ℃ in a vacuum drying device, wherein the vacuum degree is-0.1 MPa, and stopping drying when the water content of the sodium alginate granules is reduced to 5%; detecting the ethanol residue of the sodium alginate granules at the moment to be 200 ppm; introducing air with the humidity of 80% into a vacuum drying device for moisture absorption and rehydration to enable the water content of the sodium alginate particles to reach 20%; vacuum drying the sodium alginate granules subjected to the second rehydration in a vacuum drying device at 70 ℃, wherein the vacuum degree is-0.1 MPa, and stopping drying when the water content of the sodium alginate granules is reduced to 2%; detecting the ethanol residue of the sodium alginate granules at the moment to be 20 ppm; and (3) introducing air with the humidity of 60% into the vacuum drying equipment to carry out moisture balance, so that the sodium alginate particles reach the moisture content of 10%.
Example 2
200kg of alginic acid with the water content of 65 percent, 260kg of ethanol water solution with the concentration of 70 percent and 40kg of 36 DEG Besodium hydroxide are neutralized; after the neutralization is finished, centrifuging the reaction solution by using a centrifuge at 4000rpm, and removing redundant ethanol aqueous solution to obtain sodium alginate with the water content of about 55%; granulating sodium alginate by using spiral extrusion equipment, wherein the particle size is 3 mm; putting the granulated sodium alginate granules into a vacuum drying device with a stirring function to carry out vacuum drying at the temperature of 80 ℃, wherein the vacuum degree is-0.1 MPa, and stopping drying when the water content of the sodium alginate granules is reduced to 8%; detecting the ethanol residue of the sodium alginate granules at the moment to be 1200 ppm; introducing pure normal-temperature saturated water vapor into the vacuum drying equipment by using a fan, and starting stirring to ensure that the sodium alginate particles absorb moisture and rehydrate, wherein the water content reaches 30%; vacuum drying the sodium alginate granules subjected to the first rehydration in a vacuum drying device at 80 ℃, wherein the vacuum degree is-0.1 MPa, and stopping drying when the water content of the sodium alginate granules is reduced to 6%; detecting the ethanol residue of the sodium alginate granules at the moment to be 300 ppm; introducing air with the humidity of 80% into a vacuum drying device for moisture absorption and rehydration to enable the water content of the sodium alginate particles to reach 20%; vacuum drying the sodium alginate granules subjected to the second rehydration in a vacuum drying device at 80 ℃, wherein the vacuum degree is-0.1 MPa, and stopping drying when the water content of the sodium alginate granules is reduced to 3%; detecting the ethanol residue of the sodium alginate granules at the moment to be 40 ppm; and (3) introducing air with the humidity of 60% into the vacuum drying equipment to carry out moisture balance, so that the sodium alginate particles reach the moisture content of 10%.
Example 3
100kg of alginic acid with the water content of 70 percent, 150kg of ethanol water solution with the concentration of 75 percent and 18kg of 36 DEG BeNaOH are neutralized; after the neutralization is finished, centrifuging the reaction solution by using a centrifuge at 4000rpm, and removing redundant ethanol aqueous solution to obtain sodium alginate with the water content of about 60%; granulating sodium alginate by using spiral extrusion equipment, wherein the particle size is 2 mm; putting the granulated sodium alginate granules into vacuum drying equipment with a stirring function to carry out vacuum drying at 90 ℃, wherein the vacuum degree is-0.1 MPa, and stopping drying when the water content of the sodium alginate granules is reduced to 9%; detecting the ethanol residue of the sodium alginate granules at the moment to be 1500 ppm; introducing pure normal-temperature saturated water vapor into the vacuum drying equipment by using a fan, and starting stirring to ensure that the sodium alginate particles absorb moisture and rehydrate, wherein the water content reaches 30%; vacuum drying the sodium alginate granules subjected to the first rehydration at 90 ℃ in a vacuum drying device, wherein the vacuum degree is-0.1 MPa, and stopping drying when the water content of the sodium alginate granules is reduced to 7%; detecting the ethanol residue of the sodium alginate granules at the moment to be 350 ppm; introducing air with the humidity of 80% into a vacuum drying device for moisture absorption and rehydration to enable the water content of the sodium alginate particles to reach 20%; vacuum drying the sodium alginate granules subjected to the second rehydration in a vacuum drying device at 90 ℃, wherein the vacuum degree is-0.1 MPa, and stopping drying when the water content of the sodium alginate granules is reduced to 3%; detecting the ethanol residue of the sodium alginate granules at the moment to be 50 ppm; and (3) introducing air with the humidity of 60% into the vacuum drying equipment to carry out moisture balance, so that the sodium alginate particles reach the moisture content of 10%.
Comparative example 1
100kg of alginic acid with the water content of 60 percent, 120kg of ethanol aqueous solution with the concentration of 65 percent and 23kg of 36 DEG BeNaOH are neutralized; after the neutralization is finished, centrifuging the reaction solution by using a centrifuge at 4000rpm, and removing redundant ethanol aqueous solution to obtain sodium alginate with the water content of about 50%; granulating sodium alginate by using spiral extrusion equipment, wherein the particle size is 3 mm; putting the granulated sodium alginate granules into a fluidized bed dryer for hot air drying at 130 ℃, and stopping drying when the water content of the sodium alginate granules is reduced to 13%; the ethanol residue in the sodium alginate granules was 1500 ppm.
The physical properties of the sodium alginate products prepared in examples 1-3 and comparative example 1 are shown in table 1.
TABLE 1
| Colour(s) | Viscosity of the oil | |
| Example 1 | White colour (Bai) | 960cps |
| Example 2 | White colour (Bai) | 930cps |
| Example 3 | White to milky white | 890cps |
| Comparative example 1 | Milk white to light yellow | 780cps |
The foregoing is directed to preferred embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow. However, any simple modification, equivalent change and modification of the above embodiments according to the technical essence of the present invention are within the protection scope of the technical solution of the present invention.
Claims (10)
1. A preparation method of sodium alginate with low ethanol residue is characterized by comprising the following steps:
(1) vacuum drying the sodium alginate granules prepared by the liquid phase neutralization method to reduce the water content to 8-9%;
(2) introducing saturated water vapor into the dried sodium alginate granules in the step (1) to enable the sodium alginate granules to absorb moisture and rehydrate until the water content is 30%;
(3) vacuum drying the sodium alginate granules subjected to moisture absorption and rehydration in the step (2) to reduce the water content to 5-7%;
(4) introducing air with the humidity of 80% into the dried sodium alginate granules in the step (3) to enable the sodium alginate granules to absorb moisture and rehydrate until the moisture content is 20%;
(5) vacuum drying the sodium alginate granules subjected to moisture absorption and rehydration in the step (4) to reduce the water content to 2-3%;
(6) and (5) introducing air with the humidity of 60% into the dried sodium alginate granules in the step (5) to balance the water content, so that the required water content of the sodium alginate granules is achieved.
2. The method for preparing sodium alginate with low ethanol residue as claimed in claim 1, wherein the liquid phase neutralization method is used for preparing sodium alginate granules as follows:
carrying out neutralization reaction on alginic acid, ethanol water solution and sodium hydroxide according to the mass ratio of 1:1.2-1.5: 0.18-0.23; after the neutralization reaction is finished, centrifuging the reaction solution, and removing the redundant ethanol water solution to obtain sodium alginate with the water content of 50-60%; then granulating the sodium alginate to form sodium alginate granules.
3. The method for preparing sodium alginate with low ethanol residue as claimed in claim 2, wherein the mass ratio of alginic acid, ethanol aqueous solution and sodium hydroxide is 1:1.2: 0.23.
4. The method for preparing sodium alginate with low ethanol residue as claimed in claim 2, wherein the water content of alginic acid is 60-70%.
5. The method for preparing sodium alginate with low ethanol residue as claimed in claim 2, wherein the concentration of the ethanol aqueous solution is 65-75%.
6. The method for preparing sodium alginate with low ethanol residue as claimed in claim 2, wherein the sodium hydroxide is 36 ° Bee sodium hydroxide.
7. The method for preparing sodium alginate with low ethanol residue as claimed in claim 1, wherein the temperature of vacuum drying is 70-90 ℃.
8. The method for preparing sodium alginate with low ethanol residue as claimed in claim 1, wherein the saturated water vapor is pure normal temperature saturated water vapor.
9. Sodium alginate with low ethanol residue prepared by the method of any one of claims 1 to 8.
10. Use of sodium alginate according to claim 9 in the food or pharmaceutical field.
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