阅读说明：本技术 一种工业甘氨酸的生产方法 (Production method of industrial glycine ) 是由 贾京潭 冯贝 张晓慧 段兰 段永丽 于 2020-12-30 设计创作，主要内容包括：本发明公开了一种工业甘氨酸的生产方法,包括以下步骤：S1、原料配比：取甲醇1-5重量份、亚铁氰化钾1-5重量份、氯化铵3-7重量份、活性炭1-3重量份、乌洛托品溶液1-5重量份、去离子水1-10重量份、纯水20-50重量份,氯乙酸1-5重量份；S2、混合析出：将乌洛托品溶液1-3重量份、纯水20-25重量份加入混料机中混合,混合1-3min后加入活性炭1-3重量份,再次混合1-3min后对混合物进行电渗析出,得出二次加工乌洛托品溶液,通过将乌洛托溶液与纯水进行混合,对乌洛托溶液进行稀释,减少乌洛托溶液的使用量,同时通过活性炭进行过滤,产品含杂质极低,品质较高,甘氨酸纯度可达99%,且对乌洛托溶液使用量较少,通过氯乙酸溶液替代乌洛托溶液的使用量,降低成本,提高生产效率。(The invention discloses a production method of industrial glycine, which comprises the following steps: s1, mixing the following raw materials: taking 1-5 parts by weight of methanol, 1-5 parts by weight of potassium ferrocyanide, 3-7 parts by weight of ammonium chloride, 1-3 parts by weight of activated carbon, 1-5 parts by weight of urotropine solution, 1-10 parts by weight of deionized water, 20-50 parts by weight of pure water and 1-5 parts by weight of chloroacetic acid; s2, mixing and precipitating: adding 1-3 parts by weight of urotropine solution and 20-25 parts by weight of pure water into a mixer for mixing, adding 1-3 parts by weight of activated carbon after mixing for 1-3min, carrying out electroosmosis precipitation on the mixture after mixing for 1-3min again to obtain secondary processing urotropine solution, diluting the urotropine solution by mixing the urotropine solution with the pure water, reducing the using amount of the urotropine solution, filtering by using the activated carbon, and obtaining a product with extremely low impurity content, high quality, 99% purity of glycine, less using amount of the urotropine solution, replacing the using amount of the urotropine solution by using chloroacetic acid solution, reducing the cost and improving the production efficiency.)

1. The method for producing the industrial glycine is characterized by comprising the following steps of:

s1, mixing the following raw materials: taking 1-5 parts by weight of methanol, 1-5 parts by weight of potassium ferrocyanide, 3-7 parts by weight of ammonium chloride, 1-3 parts by weight of activated carbon, 1-5 parts by weight of urotropine solution, 1-10 parts by weight of deionized water, 20-50 parts by weight of pure water and 1-5 parts by weight of chloroacetic acid;

s2, mixing and precipitating: adding 1-3 parts by weight of urotropine solution and 20-25 parts by weight of pure water into a mixer for mixing, adding 1-3 parts by weight of activated carbon after mixing for 1-3min, mixing again for 1-3min, and performing electroosmosis precipitation on the mixture to obtain secondary processed urotropine solution;

s3, chloroacetic acid preparation: adding 1-5 parts by weight of chloroacetic acid and 15 parts by weight of pure water into a mixer, and mixing to obtain a chloroacetic acid solution;

s4, reaction mixing: adding liquid ammonia into the solution of the secondary processed urotropine, pumping into a mixer, controlling the temperature at 70-75 ℃, and adding chloroacetic acid solution after 30min to obtain a mixed solution;

s5, filtering: filtering the mixed solution for 3-5 times by a rough filter screen, filtering for 3-5 times by a refined filter screen, and filtering for 1-3 times by a refined filter screen, wherein 1-5 parts by weight of ammonium chloride are added during the filtering and mixing to obtain a refined mixed solution;

s6, cooling: electroosmosis separating out the mixed solution for 30-35min, pouring into a cooler, cooling to 20-25 deg.C, and keeping the temperature for half an hour to obtain crystal;

s7, removing mother liquor: putting the crystals into a centrifugal machine, and throwing off mother liquor through the centrifugal machine to obtain a filter cake;

s8, washing and drying: and washing the filter cake by methanol, putting the washed filter cake into a dryer for drying, and drying to obtain a finished product of glycine.

2. The method for producing industrial glycine as claimed in claim 1, wherein: the mixer in the S2 is a gravity-free mixer, the rotating speed of the mixer is 300-500r/min, and the mixing temperature is 50-65 ℃.

3. The method for producing industrial glycine as claimed in claim 1, wherein: the mixer in the S3 is a centrifugal heating mixer, the rotating speed is 600-.

4. The method for producing industrial glycine as claimed in claim 1, wherein: the mesh number of the crude filter screen in the S5 is 300-500 meshes, the mesh number of the refined filter screen is 800-1000 meshes, and 1-2 parts by weight of ammonium chloride and 1-3 parts by weight of ammonium chloride are respectively added during the secondary filtration and the fourth filtration of the crude filter screen.

5. The method for producing industrial glycine as claimed in claim 1, wherein: the cooler in the S6 adopts a vacuum type rapid cooler, the cooling time is 30-50min, the cooling temperature is 20-25 ℃, and the heat preservation temperature is 22-23 ℃.

6. The method for producing industrial glycine as claimed in claim 1, wherein: the centrifuge in the S7 adopts a gravity-free centrifuge, and the rotating speed is 800-.

7. The method for producing industrial glycine as claimed in claim 1, wherein: and the dryer in the S8 adopts a continuous disc dryer to heat and dry the filter cake, and the heating temperature is 50-70 ℃.

8. The method for producing industrial glycine as claimed in claim 1, wherein: and the activated carbon in the S2 is used for decoloring the solution, and the activated carbon is taken out after mixing for 1.5-2 min.

Technical Field

The invention relates to the technical field of production of glycine, in particular to a production method of industrial glycine.

Background

Glycine, also known as glycine, is a non-essential amino acid in humans. Glycine is an amino acid which is most simple in structure in an amino acid series and is not necessary for human bodies, has acidic and basic functional groups in molecules, can be ionized in water, has strong hydrophilicity, belongs to polar amino acids, is soluble in polar solvents but is insoluble in nonpolar solvents, has higher boiling point and melting point, is solid glycine crystal or white crystalline powder of white monoclinic system or hexagonal system, is odorless and nontoxic, is soluble in water, and is almost insoluble in ethanol or diethyl ether. The amino acid is used for pharmaceutical industry, biochemical test and organic synthesis, is an amino acid which has the simplest structure and is not necessary for human body in amino acid series, has acidic and basic functional groups in molecules, can be ionized in water, has strong hydrophilicity, belongs to nonpolar amino acid, is soluble in polar solvent but insoluble in nonpolar solvent, has higher boiling point and melting point, and can lead glycine to present different molecular forms through the adjustment of the acidity and the basicity of aqueous solution.

The invention is disclosed in China: CN103467324A discloses a preparation method of N, N-dimethylglycine suitable for industrial production, chloroacetic acid and dimethylamine directly carry out nucleophilic substitution reaction to generate N, N-dimethylglycine, released hydrogen chloride is absorbed by free dimethylamine to generate dimethylamine hydrochloride, and the N, N-dimethylglycine is directly obtained by a concentration method by utilizing the difference of solubility, thereby overcoming the problems of incomplete desalting by using an organic solvent and high desalting cost by using electrodialysis, but having certain problems, although the method directly obtains the N, N-dimethylglycine by a concentration method by utilizing the difference of solubility, the method overcomes the problem of incomplete desalination by using an organic solvent, however, the production period of the method is too long, the drying is only 5-7 hours, and the time is wasted, so that the method for producing the industrial glycine is provided.

Disclosure of Invention

Technical problem to be solved

Aiming at the defects of the prior art, the invention provides a production method of industrial glycine.

(II) technical scheme

In order to achieve the purpose, the invention provides the following technical scheme: a production method of industrial glycine comprises the following steps:

s1, mixing the following raw materials: taking 1-5 parts by weight of methanol, 1-5 parts by weight of potassium ferrocyanide, 3-7 parts by weight of ammonium chloride, 1-3 parts by weight of activated carbon, 1-5 parts by weight of urotropine solution, 1-10 parts by weight of deionized water, 20-50 parts by weight of pure water and 1-5 parts by weight of chloroacetic acid;

s2, mixing and precipitating: adding 1-3 parts by weight of urotropine solution and 20-25 parts by weight of pure water into a mixer for mixing, adding 1-3 parts by weight of activated carbon after mixing for 1-3min, mixing again for 1-3min, and performing electroosmosis precipitation on the mixture to obtain secondary processed urotropine solution;

s3, chloroacetic acid preparation: adding 1-5 parts by weight of chloroacetic acid and 15 parts by weight of pure water into a mixer, and mixing to obtain a chloroacetic acid solution;

s4, reaction mixing: adding liquid ammonia into the solution of the secondary processed urotropine, pumping into a mixer, controlling the temperature at 70-75 ℃, and adding chloroacetic acid solution after 30min to obtain a mixed solution;

s5, filtering: filtering the mixed solution for 3-5 times by a rough filter screen, filtering for 3-5 times by a refined filter screen, and filtering for 1-3 times by a refined filter screen, wherein 1-5 parts by weight of ammonium chloride are added during the filtering and mixing to obtain a refined mixed solution;

s6, cooling: electroosmosis separating out the mixed solution for 30-35min, pouring into a cooler, cooling to 20-25 deg.C, and keeping the temperature for half an hour to obtain crystal;

s7, removing mother liquor: putting the crystals into a centrifugal machine, and throwing off mother liquor through the centrifugal machine to obtain a filter cake;

s8, washing and drying: and washing the filter cake by methanol, putting the washed filter cake into a dryer for drying, and drying to obtain a finished product of glycine.

Preferably, the mixer in S2 is a gravity-free mixer, the rotation speed of the mixer is 300-500r/min, and the mixing temperature is 50-65 ℃.

Preferably, the mixer in S3 is a centrifugal heating mixer, the rotating speed is 600-900r/min, the temperature is 30-50 ℃, and the total mixing time is 1-1.5 h.

Preferably, the mesh number of the crude filter screen in S5 is 300-500 mesh filter screen, the refined filter screen is 800-1000 mesh filter screen, and 1-2 parts by weight of ammonium chloride and 1-3 parts by weight of ammonium chloride are respectively added during the secondary filtration and the fourth filtration of the crude filter screen.

Preferably, the cooler in S6 is a vacuum type rapid cooler, the cooling time is 30-50min, the cooling temperature is 20-25 ℃, and the heat preservation temperature is 22-23 ℃.

Preferably, the centrifuge in the S7 adopts a gravity-free centrifuge, and the rotating speed is 800-.

Preferably, the dryer in S8 adopts a continuous disc dryer to heat and dry the filter cake, and the heating temperature is 50-70 ℃.

Preferably, the activated carbon in the S2 is used for decoloring the solution, and the activated carbon is taken out after mixing for 1.5-2 min.

(III) advantageous effects

Compared with the prior art, the invention provides a production method of industrial glycine, which has the following beneficial effects: through mixing urotropine solution and pure water, dilute the urotropine solution, reduce the use amount of urotropine solution, filter through active carbon simultaneously, and add liquid ammonia through appearing and mix, filter the mixed solution after the mixture is accomplished, obtain refined mixed solution, and through obtaining the crystal after cooling down, the crystal is got out glycine after getting rid of the mother liquor stoving, the product contains impurity extremely low, the production quality is higher, glycine purity can reach 99%, and less to urotropine solution use amount, through the use amount that chloroacetic acid solution replaced urotropine solution, and reduce cost, the production time is shorter, and production efficiency is improved.

Drawings

FIG. 1 is a schematic flow chart of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example one

Referring to fig. 1, the present invention provides a technical solution: a production method of industrial glycine comprises the following steps:

s1, mixing the following raw materials: taking 1 part by weight of methanol, 1 part by weight of potassium ferrocyanide, 3 parts by weight of ammonium chloride, 1 part by weight of activated carbon, 1 part by weight of urotropine solution, 1 part by weight of deionized water, 20 parts by weight of pure water and 1 part by weight of chloroacetic acid;

s2, mixing and precipitating: adding 1 part by weight of urotropine solution and 20 parts by weight of pure water into a mixer, mixing for 1min, adding 1 part by weight of activated carbon, mixing for 1min again, and performing electroosmosis precipitation on the mixture to obtain secondary processing urotropine solution;

s3, chloroacetic acid preparation: adding 1 part by weight of chloroacetic acid and 15 parts by weight of pure water into a mixer, and mixing to obtain a chloroacetic acid solution;

s4, reaction mixing: adding liquid ammonia into the solution of the secondary processed urotropine, pumping into a mixer, controlling the temperature at 70 ℃, and adding chloroacetic acid solution after 30min to obtain a mixed solution;

s5, filtering: filtering the mixed solution for 3 times by a rough filter screen, filtering the mixed solution for 3 times by a refined filter screen for 1 time, and adding 1 part by weight of ammonium chloride and mixing the ammonium chloride and the refined filter screen together to obtain a refined mixed solution;

s6, cooling: carrying out electroosmosis precipitation on the mixed solution, pouring the mixed solution into a cooler after 30min of precipitation, reducing the temperature to 20 ℃, and keeping the temperature for half an hour to obtain crystals;

s7, removing mother liquor: putting the crystals into a centrifugal machine, and throwing off mother liquor through the centrifugal machine to obtain a filter cake;

s8, washing and drying: and washing the filter cake by methanol, putting the washed filter cake into a dryer for drying, and drying to obtain a finished product of glycine.

In this embodiment, specifically: in S2, the mixer is a gravity-free mixer, the rotating speed of the mixer is 300r/min, and the mixing temperature is 50 ℃; the gravity-free mixer makes full use of the convection mixing principle, namely, the material is thrown upwards in the mixer to form a flowing layer, so that instant weightlessness is generated, the optimal mixing effect state is achieved, in the flowing layer field, the material overcomes centrifugal force at a certain peripheral speed, the material is mixed more quickly, and the material mixing quality is improved.

In this embodiment, specifically: in S3, the mixer is a centrifugal heating mixer, the rotating speed is 600r/min, the temperature is 30 ℃, and the total mixing time is 1 h.

In this embodiment, specifically: in S5, the coarse filter screen is 300 meshes, the fine filter screen is 800 meshes, and 1 weight part of ammonium chloride are respectively added during the secondary filtration and the fourth filtration of the coarse filter screen.

In this embodiment, specifically: the cooler in S6 adopts a vacuum type rapid cooler, the cooling time is 30min, the cooling temperature is 20 ℃, and the heat preservation temperature is 22 ℃.

In this embodiment, specifically: the centrifuge in S7 adopts a gravity-free centrifuge with a rotation speed of 800r/min, the centrifuge is a machine for separating each component in liquid and solid particles or a mixture of liquid and liquid by utilizing centrifugal force, the centrifuge is mainly used for separating the solid particles from the liquid in suspension or separating two liquids which have different densities and are not mutually soluble in emulsion, thereby separating mother liquor from crystals.

In this embodiment, specifically: s8, heating and drying a filter cake by a continuous disc dryer at 50 ℃ by using a dryer; the disc type continuous drier is a high-efficiency conduction type continuous drying device, and the unique structure and the working principle determine that the disc type continuous drier has the characteristics of high thermal efficiency, low energy consumption, small occupied area, simple configuration, convenient operation and control, good operation environment and the like, does not need to be provided with a cyclone dust collector which is necessary to be configured for spray drying, and does not use hot air as a heating medium, so that the product loss caused by entrainment of tail gas due to poor separation of the hot air and dust can be avoided.

In this embodiment, specifically: and (5) decolorizing the solution by using activated carbon in S2, mixing for 1.5min, and taking out the activated carbon.

Example two

Referring to fig. 1, the present invention further provides a technical solution: a production method of industrial glycine comprises the following steps:

s1, mixing the following raw materials: taking 4 parts by weight of methanol, 3 parts by weight of potassium ferrocyanide, 3 parts by weight of ammonium chloride, 2 parts by weight of activated carbon, 3 parts by weight of urotropine solution, 5 parts by weight of deionized water, 30 parts by weight of pure water and 3 parts by weight of chloroacetic acid;

s2, mixing and precipitating: adding 2 parts by weight of urotropine solution and 22 parts by weight of pure water into a mixer for mixing, adding 2 parts by weight of activated carbon after mixing for 2min, mixing again for 2min, and performing electroosmosis precipitation on the mixture to obtain secondary processing urotropine solution;

s3, chloroacetic acid preparation: adding 3 parts by weight of chloroacetic acid and 15 parts by weight of pure water into a mixer, and mixing to obtain a chloroacetic acid solution;

s4, reaction mixing: adding liquid ammonia into the solution of the secondary processed urotropine, pumping into a mixer, controlling the temperature at 72 ℃, adding chloroacetic acid solution after 30min, and obtaining mixed solution;

s5, filtering: filtering the mixed solution for 4 times by a rough filter screen, filtering the mixed solution for 4 times by a refined filter screen for 2 times, and adding 3 parts by weight of ammonium chloride during the filtering and mixing to obtain a refined mixed solution;

s6, cooling: carrying out electroosmosis precipitation on the mixed solution, pouring the mixed solution into a cooler after 33min of precipitation, reducing the temperature to 22 ℃, and keeping the temperature for half an hour to obtain crystals;

s7, removing mother liquor: putting the crystals into a centrifugal machine, and throwing off mother liquor through the centrifugal machine to obtain a filter cake;

s8, washing and drying: and washing the filter cake by methanol, putting the washed filter cake into a dryer for drying, and drying to obtain a finished product of glycine.

In this embodiment, specifically: in S2, the mixer is a gravity-free mixer, the rotating speed of the mixer is 400r/min, and the mixing temperature is 60 ℃; the gravity-free mixer makes full use of the convection mixing principle, namely, the material is thrown upwards in the mixer to form a flowing layer, so that instant weightlessness is generated, the optimal mixing effect state is achieved, in the flowing layer field, the material overcomes centrifugal force at a certain peripheral speed, the material is mixed more quickly, and the material mixing quality is improved.

In this embodiment, specifically: in S3, the mixer is a centrifugal heating mixer, the rotating speed is 700r/min, the temperature is 40 ℃, and the total mixing time is 1.3 h.

In this embodiment, specifically: in S5, the coarse filter screen is 400 meshes, the fine filter screen is 900 meshes, and 1.5 parts by weight of ammonium chloride and 2 parts by weight of ammonium chloride are respectively added during the secondary filtration and the fourth filtration of the coarse filter screen.

In this embodiment, specifically: the cooler in S6 adopts a vacuum type rapid cooler, the cooling time is 40min, the cooling temperature is 22 ℃, and the heat preservation temperature is 22 ℃.

In this embodiment, specifically: the centrifuge in S7 adopts a gravity-free centrifuge with a rotation speed of 900r/min, the centrifuge is a machine for separating each component in liquid and solid particles or a mixture of liquid and liquid by utilizing centrifugal force, the centrifuge is mainly used for separating the solid particles from the liquid in suspension, or separating two liquids which have different densities and are not mutually soluble in emulsion, thereby separating mother liquor from crystals.

In this embodiment, specifically: s8, heating and drying a filter cake by a continuous disc dryer at the heating temperature of 60 ℃ by using the dryer; the disc type continuous drier is a high-efficiency conduction type continuous drying device, and the unique structure and the working principle determine that the disc type continuous drier has the characteristics of high thermal efficiency, low energy consumption, small occupied area, simple configuration, convenient operation and control, good operation environment and the like, does not need to be provided with a cyclone dust collector which is necessary to be configured for spray drying, and does not use hot air as a heating medium, so that the product loss caused by entrainment of tail gas due to poor separation of the hot air and dust can be avoided.

In this embodiment, specifically: and (5) decolorizing the solution by using activated carbon in S2, mixing for 1.7min, and taking out the activated carbon.

EXAMPLE III

Referring to fig. 1, the present invention further provides a technical solution: a production method of industrial glycine comprises the following steps:

s1, mixing the following raw materials: taking 5 parts by weight of methanol, 5 parts by weight of potassium ferrocyanide, 7 parts by weight of ammonium chloride, 3 parts by weight of activated carbon, 5 parts by weight of urotropine solution, 10 parts by weight of deionized water, 50 parts by weight of pure water and 5 parts by weight of chloroacetic acid;

s2, mixing and precipitating: adding 3 parts by weight of urotropine solution and 25 parts by weight of pure water into a mixer, mixing for 3min, adding 3 parts by weight of activated carbon, mixing for 3min again, and performing electroosmosis precipitation on the mixture to obtain secondary processing urotropine solution;

s3, chloroacetic acid preparation: adding 5 parts by weight of chloroacetic acid and 15 parts by weight of pure water into a mixer, and mixing to obtain a chloroacetic acid solution;

s4, reaction mixing: adding liquid ammonia into the solution of the secondary processed urotropine, pumping into a mixer, controlling the temperature at 75 ℃, and adding chloroacetic acid solution after 30min to obtain a mixed solution;

s5, filtering: filtering the mixed solution for 5 times by a rough filter screen, filtering the mixed solution for 3 times by a refined filter screen after filtering the mixed solution for 5 times by the rough filter screen, and adding 5 parts by weight of ammonium chloride to filter and mix the mixture to obtain a refined mixed solution;

s6, cooling: carrying out electroosmosis precipitation on the mixed solution, pouring the solution into a cooler after 35min of precipitation, reducing the temperature to 25 ℃, and keeping the temperature for half an hour to obtain crystals;

s7, removing mother liquor: putting the crystals into a centrifugal machine, and throwing off mother liquor through the centrifugal machine to obtain a filter cake;

s8, washing and drying: and washing the filter cake by methanol, putting the washed filter cake into a dryer for drying, and drying to obtain a finished product of glycine.

In this embodiment, specifically: in S2, the mixer is a gravity-free mixer, the rotating speed of the mixer is 500r/min, and the mixing temperature is 65 ℃; the gravity-free mixer makes full use of the convection mixing principle, namely, the material is thrown upwards in the mixer to form a flowing layer, so that instant weightlessness is generated, the optimal mixing effect state is achieved, in the flowing layer field, the material overcomes centrifugal force at a certain peripheral speed, the material is mixed more quickly, and the material mixing quality is improved.

In this embodiment, specifically: in S3, the mixer is a centrifugal heating mixer, the rotating speed is 900r/min, the temperature is 50 ℃, and the total mixing time is 1.5 h.

In this embodiment, specifically: in S5, the coarse filter screen is 500 meshes, the fine filter screen is 1000 meshes, and 2 weight parts of ammonium chloride and 3 weight parts of ammonium chloride are respectively added during the secondary filtration and the fourth filtration of the coarse filter screen.

In this embodiment, specifically: the cooler in S6 adopts a vacuum type rapid cooler, the cooling time is 50min, the cooling temperature is 25 ℃, and the heat preservation temperature is 23 ℃.

In this embodiment, specifically: the centrifuge in S7 is a gravity-free centrifuge with rotation speed of 1200r/min, and is a machine for separating liquid and solid particles or components in a mixture of liquid and liquid by centrifugal force, and is mainly used for separating solid particles from liquid in suspension or separating two liquids which have different densities and are insoluble with each other in emulsion, so as to separate mother liquor from crystals.

In this embodiment, specifically: s8, heating and drying a filter cake by a continuous disc dryer at the heating temperature of 70 ℃; the disc type continuous drier is a high-efficiency conduction type continuous drying device, and the unique structure and the working principle determine that the disc type continuous drier has the characteristics of high thermal efficiency, low energy consumption, small occupied area, simple configuration, convenient operation and control, good operation environment and the like, does not need to be provided with a cyclone dust collector which is necessary to be configured for spray drying, and does not use hot air as a heating medium, so that the product loss caused by entrainment of tail gas due to poor separation of the hot air and dust can be avoided.

In this embodiment, specifically: and (5) decolorizing the solution by using the activated carbon in the S2, mixing for 2min, and taking out the activated carbon.

In conclusion, the working principle and the working process of the production method of the industrial glycine comprise that when the production method is used, the urotropine solution is mixed with pure water, the urotropine solution is diluted, the using amount of the urotropine solution is reduced, meanwhile, the activated carbon is used for filtering, liquid ammonia is added for mixing through precipitation, the mixed solution is filtered after mixing is completed, a refined mixed solution is obtained, crystals are obtained after cooling, the crystals are removed from mother liquor and dried, the glycine is obtained, the impurity content of the product is extremely low, the quality is high, the purity of the glycine can reach 99%, the using amount of the urotropine solution is small, the chloroacetic acid solution replaces the using amount of the urotropine solution, and the cost is reduced.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.