CN111718432B - Method for coagulating natural latex by adopting high-pressure carbon dioxide - Google Patents
Method for coagulating natural latex by adopting high-pressure carbon dioxide Download PDFInfo
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- CN111718432B CN111718432B CN202010667571.6A CN202010667571A CN111718432B CN 111718432 B CN111718432 B CN 111718432B CN 202010667571 A CN202010667571 A CN 202010667571A CN 111718432 B CN111718432 B CN 111718432B
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- C08C—TREATMENT OR CHEMICAL MODIFICATION OF RUBBERS
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Abstract
The invention provides a method for coagulating natural latex by adopting high-pressure carbon dioxide, belonging to the technical field of natural latex coagulation. The method for coagulating the natural latex by using the high-pressure carbon dioxide comprises the following steps of: and introducing carbon dioxide under a closed condition until the pressure is 10-30 MPa, and solidifying the natural latex to obtain the rubber clot. The invention adopts high-pressure carbon dioxide to solidify natural latex, the solidification speed of the latex is high, the whole process is carried out in a closed reaction kettle, water-insoluble non-glue components (such as protein, phosphate and the like) in the latex are reserved to the maximum extent, and the high performance of the product is kept; in addition, as the carbon dioxide is a chemical inert gas, the natural rubber latex is coagulated under the protection of the carbon dioxide, the components in the natural rubber latex are not damaged, the original state can be kept, the finally prepared natural rubber product has good quality, and a new thought is provided for the coagulation of the natural rubber latex.
Description
Technical Field
The invention relates to the technical field of natural latex solidification, in particular to a method for solidifying natural latex by adopting high-pressure carbon dioxide.
Background
The natural rubber latex flowing out from the rubber tree is coagulated into coagulum, and then the coagulum can enter the working procedures of thinning, pressing crepe and dehydration, hammer milling and granulation and drying, and finally a solid natural rubber product (crude rubber) is prepared. The natural latex contains rubber hydrocarbon and water as main components and also contains 5% of non-rubber components, and the electric double layer protection formed by the components ensures that the fresh latex keeps a stable emulsion state. The natural latex coagulation is mainly caused by breaking the charge balance of a latex system by adopting a chemical, biological or physical method, and currently, chemical and biological coagulation methods such as acid coagulation, inorganic salt coagulation, microbial coagulation, natural coagulation, enzyme coagulation and the like are commonly used. In addition, there are physical coagulation methods such as thermal coagulation of matured latex using a small thermal gel machine; the patents reported are: (1) a method (CN 101519461B) for solidifying natural rubber emulsion by microwave radiation comprises subjecting natural rubber emulsion to microwave radiation treatment under flowing or static state to obtain flocculent gel, solidifying and aging to obtain coagulum; (2) a method (CN 102477109A) for promoting the coagulation of natural rubber latex by vacuum, which uses a small amount of acetic acid as a primer, and utilizes the vacuum technology to make the particles in the latex instantaneously break and the latex lose stability and coagulate; (3) a jet coagulating method for natural rubber latex (CN 103275248B) features that a pressure pump is used to pressurize the natural rubber latex, which is then jetted via jet orifice into gasifying chamber to form natural rubber microgel particles. Further, physical methods for coagulating natural rubber latex include freezing, stirring and the like, but physical coagulation methods are relatively little studied in general.
High pressure carbon dioxide has been used in research on sterilization as early as 1951 (Frase rD. bursting bacteria by release of gas pressure [ J ] Nature,1951,167(4236):33-34.), and the application of high pressure carbon dioxide or supercritical carbon dioxide in the rubber industry mainly focuses on research on graft synthesis of ionomers or preparation of composite materials, desulfurization regeneration of rubber powder and waste tire rubber, preparation of rubber or polymer foam materials, diffusion, degradation and stripping of rubber in supercritical carbon dioxide fluid, and the like. At present, there is no report on coagulation of natural latex with high-pressure carbon dioxide.
Disclosure of Invention
The invention aims to provide a method for coagulating natural latex by adopting high-pressure carbon dioxide, which has high coagulation speed and good quality of prepared natural rubber products.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a method for coagulating natural latex by adopting high-pressure carbon dioxide, which comprises the following steps:
and introducing carbon dioxide under a closed condition until the pressure is 10-30 MPa, and solidifying the natural latex to obtain the rubber clot.
Preferably, the natural rubber latex is natural rubber latex with ammonia content of 0-0.45% and dry rubber content of more than or equal to 25% in percentage by mass.
Preferably, the solidification is carried out under a constant temperature condition, and the constant temperature is 25-40 ℃.
Preferably, the constant temperature is realized by a water bath environment.
Preferably, the solidification is carried out under a standing condition, and the standing time is 1-5 hours.
Preferably, the closed conditions are provided by a reaction kettle.
Preferably, after the pressure is reached, maintaining the pressure for 5-10 min.
Preferably, after the rubber coagulum is obtained, the rubber coagulum is subjected to thinning, pressing and creping for dehydration, granulation and drying in sequence to obtain the natural rubber product.
Preferably, the drying temperature is 60-100 ℃.
The invention provides a method for coagulating natural latex by adopting high-pressure carbon dioxide, which comprises the following steps: and introducing carbon dioxide under a closed condition until the pressure is 10-30 MPa, and solidifying the natural latex to obtain the rubber clot. The invention adopts high-pressure carbon dioxide to solidify natural latex, the solidification speed of the latex is high, the whole process is carried out in a closed reaction kettle, water-insoluble non-glue components (such as protein, phosphate and the like) in the latex are reserved to the maximum extent, and the high performance of the product is kept; in addition, as the carbon dioxide is a chemical inert gas, the natural latex is coagulated under the protection of the carbon dioxide, the components in the natural latex are not damaged, the original state can be kept, the prepared natural rubber product has good quality, and a new thought is provided for the coagulation of the natural latex. The results of the examples show that the properties of the natural rubber products produced by coagulating the rubber coagulum obtained by the process of the invention are excellent.
In the method, no coagulant is added in the solidification process, and the generated wastewater can directly enter a wastewater treatment link without neutralization.
Detailed Description
The invention provides a method for coagulating natural latex by adopting high-pressure carbon dioxide, which comprises the following steps:
and introducing carbon dioxide under a closed condition until the pressure is 10-30 MPa, and solidifying the natural latex to obtain the rubber clot.
In the present invention, unless otherwise specified, all the starting materials required for the preparation are commercially available products well known to those skilled in the art.
In the invention, the natural latex is fresh natural latex collected on the same day, and in order to ensure that the natural latex does not deteriorate before processing, ammonia water is added into the fresh natural latex for preservation, so that the pH value of the latex is alkaline. In the invention, the ammonia content of the natural rubber latex is 0-0.45% by mass, more preferably 0-0.1% by mass, and the dry rubber content is preferably not less than 25%. The process of adding the ammonia water is not particularly limited, and the natural latex with the ammonia content can be obtained. The invention can ensure the quality of the fresh natural latex by controlling the ammonia content and the dry rubber content of the natural latex within the range.
In the present invention, the ammonia content and dry rubber content of the natural latex are based on natural latex raw materials, and when the natural latex within the above content range is used as a raw material, the natural latex can be coagulated as it is or after the natural latex raw material is diluted, preferably. The invention has no special limitation on the dilution process and the dilution multiple, and can be adjusted according to the actual requirement.
In the present invention, the sealing condition is preferably provided by a reaction kettle, that is, in the present invention, the natural rubber latex is preferably placed in the reaction kettle, and after the reaction kettle is sealed, carbon dioxide is introduced into the reaction kettle. The reaction kettle is not particularly limited in the present invention, and may be a reaction kettle known in the art, and in the embodiments of the present invention, the reaction kettle is made of stainless steel, and has a volume of 2.5L, 10L or 30L.
The flow of the introduced carbon dioxide is not specially limited, the required pressure in the reaction kettle can be achieved, and the pressure is preferably 15-25 MPa and more preferably 20MPa after the carbon dioxide is introduced; and after the pressure is reached, preferably maintaining the pressure for 5-10 min, and more preferably 6-8 min. The invention preferably adopts a pump to realize the process of introducing the carbon dioxide; the pump is not specially limited, and any pump capable of introducing carbon dioxide to reach the required pressure can be realized. The present invention can shorten the coagulation time of natural latex by controlling the pressure.
As the natural latex contains about 70 percent of water, the invention adopts carbon dioxide to pressurize so as to increase the solubility of the carbon dioxide in the natural latex, the generated carbonic acid can neutralize ammonia (ammonia added for fresh keeping) in the natural latex and break the charge balance of a natural latex system so as to cause the natural latex to be coagulated; meanwhile, the carbon dioxide pressurization can generate an extrusion effect on rubber particles in the natural latex, so that the rubber particles are forced to be accumulated together to accelerate the solidification speed of the latex, and the solidification of the natural latex is finally realized.
In the invention, the solidification is preferably carried out under a constant temperature condition, and the constant temperature is preferably 25-40 ℃, and more preferably 28-31 ℃; the constant temperature is preferably realized through a water bath environment, namely, the reaction kettle is placed in a water bath for solidification. The present invention can prevent the natural latex from being denatured by overheating by controlling the temperature within the above range.
In the invention, the solidification is preferably carried out under a standing condition, and the standing time is preferably 1-5 h, and more preferably 2-3 h. During the standing, the natural latex slowly and sufficiently coagulated.
And after the solidification is finished, releasing pressure and recovering carbon dioxide to obtain the rubber clot.
In the present invention, after the rubber coagulum is obtained, the process for preparing natural rubber from the rubber coagulum is preferably to perform thinning, creping and dewatering, granulation and drying on the rubber coagulum in sequence to obtain a natural rubber product. The process of the present invention for the thinning, creping, dewatering and pelletizing is not particularly limited, and any process known in the art may be used to obtain the natural rubber product. In the invention, the drying temperature is preferably 60-100 ℃, and more preferably 70-80 ℃; the drying time is not particularly limited in the present invention, and a natural rubber product can be obtained according to a process well known in the art.
The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. 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 1
Taking 2kg of fresh natural latex with ammonia content of 0.05% and dry rubber content of 31.20% collected on the same day, putting the fresh natural latex into a 2.5L stainless steel reaction kettle, closing a reaction kettle cover, adjusting a constant temperature water bath to control the temperature to be 30 ℃, introducing carbon dioxide into the reaction kettle after the temperature is constant, keeping the pressure in the reaction kettle to 10MPa for 5min, closing a valve, standing for 5h under a pressure state, decompressing and recovering the carbon dioxide to obtain the rubber clot.
Example 2
According to the mass percentage content, 5kg of fresh natural latex with 0.1% of ammonia content and 32.78% of dry rubber content collected on the same day is taken, 3.2kg of water is added, the dry rubber content is diluted to 20%, the diluted dry rubber is placed into a 10L stainless steel reaction kettle, a reaction kettle cover is closed, a constant temperature water bath is adjusted to control the temperature to be 30 ℃, after the temperature is constant, carbon dioxide is introduced into the reaction kettle, the pressure in the reaction kettle reaches 20MPa and is maintained for 10min, a valve is closed, standing is carried out for 4h under the pressure state, the pressure is released, and the carbon dioxide is recovered, so that the rubber clot is obtained.
Example 3
According to the mass percentage content, 20kg of fresh natural latex with 0.08 percent of ammonia content and 27.94 percent of dry rubber content collected on the same day is taken, 2.35kg of water is added, the dry rubber content is diluted to 25 percent and is placed into a 30L stainless steel reaction kettle, the cover of the reaction kettle is closed, a constant temperature water bath is regulated to control the temperature to be 30 ℃, after the temperature is constant, carbon dioxide is introduced into the reaction kettle, the pressure in the reaction kettle reaches 30MPa and is maintained for 10min, a valve is closed, the reaction kettle is kept still for 3h under the pressure state, the pressure is released, and the carbon dioxide is recovered, so that the rubber clot is obtained.
Comparative example 1
The natural latex is coagulated by an acid coagulation method: according to the mass percentage, 5kg of fresh natural latex with 0.05 percent of ammonia content and 31.20 percent of dry rubber content collected on the same day is taken, 2070mL of water and 730mL of formic acid solution with the mass concentration of 2 percent are added to ensure that the latex has the solidification concentration of 20 percent, and the latex is placed in a plastic tray for standing and solidification for 16 hours to obtain the rubber clot.
Performance testing
The rubber coagulum prepared in example 1 is subjected to thinning, creping, dewatering and granulation in sequence, and then is dried in a vacuum drying oven at 70 ℃, and the obtained natural rubber product is marked as NR-h 1;
the rubber coagulum prepared in example 2 is subjected to thinning, creping, dewatering and granulation in sequence, and then is dried in a vacuum drying oven at 80 ℃ to obtain a natural rubber product, which is marked as NR-h 2;
the rubber coagulum prepared in example 3 was successively subjected to thinning, creping, dewatering and granulation, and then dried in a vacuum drying oven at 90 ℃ to give a natural rubber product designated as NR-h 3.
The rubber coagulum prepared in comparative example 1 was subjected to thinning, creping, dewatering and granulation in this order, and then dried in a vacuum drying oven at 80 ℃ to give a natural rubber product designated as NR-a.
The natural rubber products prepared from the rubber clots of examples 1-3 and comparative example 1 were tested for their performance by a conventional method, and the results of the test for measuring the vulcanization performance of the rubber were shown in Table 1, according to the ACS I pure rubber formulation (100.00 parts of natural rubber, 6.00 parts of zinc oxide, 3.50 parts of sulfur, 0.50 parts of stearic acid, and 0.50 parts of MBT) specified in NY/T1403-2007.
TABLE 1 Performance data for Natural rubber products prepared in examples 1-3 and comparative example 1
As can be seen from the data in Table 1, the indexes such as PRI, tensile strength and the like of the natural rubber products prepared by the rubber coagulums of the embodiments 1 to 3 are obviously superior to those of the acid coagulation sample of the comparative example 1, and the method for coagulating the natural rubber latex by using the carbon dioxide provided by the invention does not influence the performance of the natural rubber products.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (9)
1. A method for coagulating natural rubber latex with high pressure carbon dioxide comprising the steps of:
and introducing carbon dioxide under a closed condition until the pressure is 10-30 MPa, and solidifying the natural latex to obtain the rubber clot.
2. The method according to claim 1, wherein the natural rubber latex is a natural rubber latex having an ammonia content of 0 to 0.45% and a dry rubber content of 25% or more, in terms of mass percentage.
3. The method according to claim 1, wherein the solidification is carried out under a constant temperature condition, and the temperature of the constant temperature is 25-40 ℃.
4. The method of claim 3, wherein said constant temperature is achieved by a water bath environment.
5. The method according to claim 3, wherein the solidification is carried out under a standing condition, and the standing time is 1-5 hours.
6. The method of claim 1, wherein the closed conditions are provided by a reaction vessel.
7. The method according to claim 1, wherein the pressure is maintained for 5 to 10min after the pressure is reached.
8. The method according to any one of claims 1 to 7, wherein after obtaining the rubber coagulum, the rubber coagulum is subjected to thinning, creping and dewatering, granulating and drying in sequence to obtain a natural rubber product.
9. The method according to claim 8, wherein the drying temperature is 60 to 100 ℃.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202010667571.6A CN111718432B (en) | 2020-07-13 | 2020-07-13 | Method for coagulating natural latex by adopting high-pressure carbon dioxide |
| AU2020223672A AU2020223672B1 (en) | 2020-07-13 | 2020-08-26 | Method for coagulating natural rubber latex using high-pressure carbon dioxide |
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| CN202010667571.6A CN111718432B (en) | 2020-07-13 | 2020-07-13 | Method for coagulating natural latex by adopting high-pressure carbon dioxide |
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1539867A (en) * | 2003-04-21 | 2004-10-27 | 佛山市华昊化工有限公司电化厂 | New method-carbonating method for agglomerating MBS latex |
| CN102378782A (en) * | 2009-03-17 | 2012-03-14 | 朗盛德国有限责任公司 | Method for producing polymeric solids |
| JP2012158667A (en) * | 2011-01-31 | 2012-08-23 | Toyo Tire & Rubber Co Ltd | Unvulcanized diene-based rubber coagulation, method for producing the same, unvulcanized rubber composition and pneumatic tire |
| CN103275248A (en) * | 2013-05-16 | 2013-09-04 | 海南大学 | Natural latex jet-flow solidification method |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA2035604A1 (en) * | 1990-02-16 | 1991-08-17 | Robert W. Coyle | Purification of latex |
| WO2020109267A1 (en) * | 2018-11-27 | 2020-06-04 | Covestro Deutschland Ag | Method for preparing track bed |
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2020
- 2020-07-13 CN CN202010667571.6A patent/CN111718432B/en active Active
- 2020-08-26 AU AU2020223672A patent/AU2020223672B1/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1539867A (en) * | 2003-04-21 | 2004-10-27 | 佛山市华昊化工有限公司电化厂 | New method-carbonating method for agglomerating MBS latex |
| CN102378782A (en) * | 2009-03-17 | 2012-03-14 | 朗盛德国有限责任公司 | Method for producing polymeric solids |
| JP2012158667A (en) * | 2011-01-31 | 2012-08-23 | Toyo Tire & Rubber Co Ltd | Unvulcanized diene-based rubber coagulation, method for producing the same, unvulcanized rubber composition and pneumatic tire |
| CN103275248A (en) * | 2013-05-16 | 2013-09-04 | 海南大学 | Natural latex jet-flow solidification method |
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