CN115260351B - Method for preparing polyvinyl alcohol with polymerization degree of 80 by soap-free emulsion polymerization - Google Patents
Method for preparing polyvinyl alcohol with polymerization degree of 80 by soap-free emulsion polymerization Download PDFInfo
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- CN115260351B CN115260351B CN202210928922.3A CN202210928922A CN115260351B CN 115260351 B CN115260351 B CN 115260351B CN 202210928922 A CN202210928922 A CN 202210928922A CN 115260351 B CN115260351 B CN 115260351B
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- 238000006116 polymerization reaction Methods 0.000 title claims abstract description 86
- 239000004372 Polyvinyl alcohol Substances 0.000 title claims abstract description 72
- 229920002451 polyvinyl alcohol Polymers 0.000 title claims abstract description 72
- 238000000034 method Methods 0.000 title claims abstract description 51
- 238000007720 emulsion polymerization reaction Methods 0.000 title claims abstract description 20
- 238000006243 chemical reaction Methods 0.000 claims abstract description 34
- HEDRZPFGACZZDS-UHFFFAOYSA-N Chloroform Chemical group ClC(Cl)Cl HEDRZPFGACZZDS-UHFFFAOYSA-N 0.000 claims description 62
- 229920002689 polyvinyl acetate Polymers 0.000 claims description 55
- 239000011118 polyvinyl acetate Substances 0.000 claims description 55
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 27
- 239000012986 chain transfer agent Substances 0.000 claims description 24
- 239000003999 initiator Substances 0.000 claims description 24
- 238000003756 stirring Methods 0.000 claims description 24
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 24
- 239000008367 deionised water Substances 0.000 claims description 22
- 229910021641 deionized water Inorganic materials 0.000 claims description 22
- XTXRWKRVRITETP-UHFFFAOYSA-N Vinyl acetate Chemical group CC(=O)OC=C XTXRWKRVRITETP-UHFFFAOYSA-N 0.000 claims description 19
- ROOXNKNUYICQNP-UHFFFAOYSA-N ammonium persulfate Chemical group [NH4+].[NH4+].[O-]S(=O)(=O)OOS([O-])(=O)=O ROOXNKNUYICQNP-UHFFFAOYSA-N 0.000 claims description 18
- 238000000710 polymer precipitation Methods 0.000 claims description 18
- 230000008014 freezing Effects 0.000 claims description 17
- 238000007710 freezing Methods 0.000 claims description 17
- 230000035484 reaction time Effects 0.000 claims description 17
- 239000000839 emulsion Substances 0.000 claims description 15
- 238000006136 alcoholysis reaction Methods 0.000 claims description 14
- 238000010556 emulsion polymerization method Methods 0.000 claims description 11
- GRONZTPUWOOUFQ-UHFFFAOYSA-M sodium;methanol;hydroxide Chemical compound [OH-].[Na+].OC GRONZTPUWOOUFQ-UHFFFAOYSA-M 0.000 claims description 11
- 229910001870 ammonium persulfate Inorganic materials 0.000 claims description 9
- 238000001035 drying Methods 0.000 claims description 8
- 238000010438 heat treatment Methods 0.000 claims description 8
- 239000000376 reactant Substances 0.000 claims description 8
- 238000005406 washing Methods 0.000 claims description 7
- 239000002994 raw material Substances 0.000 claims description 5
- 238000010257 thawing Methods 0.000 claims description 4
- 238000002360 preparation method Methods 0.000 abstract description 23
- 239000000178 monomer Substances 0.000 abstract description 20
- 230000008901 benefit Effects 0.000 abstract description 4
- 229960001701 chloroform Drugs 0.000 description 31
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 22
- 238000002474 experimental method Methods 0.000 description 9
- VZGDMQKNWNREIO-UHFFFAOYSA-N tetrachloromethane Chemical compound ClC(Cl)(Cl)Cl VZGDMQKNWNREIO-UHFFFAOYSA-N 0.000 description 8
- 238000012546 transfer Methods 0.000 description 8
- 238000009776 industrial production Methods 0.000 description 7
- LSDPWZHWYPCBBB-UHFFFAOYSA-N Methanethiol Chemical compound SC LSDPWZHWYPCBBB-UHFFFAOYSA-N 0.000 description 6
- 239000000463 material Substances 0.000 description 6
- 239000003153 chemical reaction reagent Substances 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- 229920000642 polymer Polymers 0.000 description 5
- 239000000047 product Substances 0.000 description 4
- WSFSSNUMVMOOMR-UHFFFAOYSA-N Formaldehyde Chemical compound O=C WSFSSNUMVMOOMR-UHFFFAOYSA-N 0.000 description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
- 238000009826 distribution Methods 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
- 230000001276 controlling effect Effects 0.000 description 2
- 239000000835 fiber Substances 0.000 description 2
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- USHAGKDGDHPEEY-UHFFFAOYSA-L potassium persulfate Chemical compound [K+].[K+].[O-]S(=O)(=O)OOS([O-])(=O)=O USHAGKDGDHPEEY-UHFFFAOYSA-L 0.000 description 2
- 238000010992 reflux Methods 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 150000003573 thiols Chemical class 0.000 description 2
- 238000005481 NMR spectroscopy Methods 0.000 description 1
- 229920002978 Vinylon Polymers 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 239000007859 condensation product Substances 0.000 description 1
- 239000006260 foam Substances 0.000 description 1
- 238000010528 free radical solution polymerization reaction Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 238000013341 scale-up Methods 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 229920002554 vinyl polymer Polymers 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F8/00—Chemical modification by after-treatment
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F2/00—Processes of polymerisation
- C08F2/12—Polymerisation in non-solvents
- C08F2/16—Aqueous medium
- C08F2/22—Emulsion polymerisation
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F2/00—Processes of polymerisation
- C08F2/38—Polymerisation using regulators, e.g. chain terminating agents, e.g. telomerisation
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- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Polymerisation Methods In General (AREA)
- Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
Abstract
The invention provides a method for preparing polyvinyl alcohol with 80 polymerization degrees by soap-free emulsion polymerization. The invention designs and optimizes a method for preparing polyvinyl alcohol with 80 polymerization degrees by soap-free emulsion polymerization based on the principle of soap-free emulsion polymerization, and the preparation method has the advantages of higher monomer conversion rate, novel method, unique route and suitability for industrialization.
Description
The application is a divisional application, and the original application number is: 202210028968.X, filing date: 2022, 1 month 11, title: a method for preparing polyvinyl alcohol with low polymerization degree by soap-free emulsion polymerization.
Technical Field
The invention belongs to the technical field of preparation of polyvinyl alcohol with low polymerization degree, and particularly relates to a method for preparing polyvinyl alcohol with low polymerization degree by soap-free emulsion polymerization.
Technical Field
Polyvinyl alcohol, PVA for short, is a water-soluble and environment-friendly polymer with a large amount of hydroxyl groups (-OH) in the side chains. The hydroxyl has high reactivity, and can easily react with various functional reagents to generate the compound with special function. For example, polyvinyl formal (PVF) foam is a condensation product of PVA and formaldehyde under acidic conditions, and is a very important class of polymeric materials.
PVA is a water-soluble polyhydroxy polymer, the performance of which is greatly affected by the degree of polymerization, and PVA with high degree of polymerization is mainly used as fibers and films in general; the PVA with low polymerization degree has better water solubility and biocompatibility and has wide application in the aspect of non-fiber use. Meanwhile, PVA with low polymerization degree has better degradability, and meets the requirements of green environment protection, so that the PVA is paid more attention.
At present, a certain research is carried out on PVA with low polymerization degree at home and abroad, but basically, a solution polymerization method is adopted, and the research on preparing PVA with low polymerization degree by a soap-free emulsion polymerization method is relatively less.
Disclosure of Invention
In order to solve the problems in the background art, the invention provides a method for preparing polyvinyl alcohol with low polymerization degree by soap-free emulsion polymerization, which is based on the principle of the soap-free emulsion polymerization, is designed and optimized by contrast and gradient experiments, has higher monomer conversion rate, can regulate the polymerization degree of PVA by regulating the addition amount of a chain transfer agent, and has the advantages of novel method, unique route and suitability for industrial production.
In order to achieve the above object, the present invention is realized by adopting the technical scheme comprising the following technical measures.
A method for preparing PVA with low polymerization degree by soap-free emulsion polymerization comprises the steps of preparing polyvinyl acetate by a soap-free emulsion polymerization method, and performing alcoholysis on the prepared polyvinyl acetate to obtain PVA with low polymerization degree;
the polyvinyl acetate is prepared by a soap-free emulsion polymerization method, and the raw materials of the polyvinyl acetate mainly comprise the following components in parts by weight:
wherein, the total weight of the vinyl acetate monomer and the deionized water is 100 parts, and the mass ratio of the vinyl acetate monomer to the chain transfer agent is 10: (1-4);
the chain transfer agent is any one of acetone, chloroform and mercaptan.
Typically, the initiator is an initiator conventionally used in soap-free emulsion polymerization processes, and a person skilled in the art can select a suitable initiator by himself according to the state of the art in soap-free emulsion polymerization processes. For better illustrating the invention and providing a technical scheme for reference, the initiator selection can comprise ammonium persulfate, potassium persulfate and the like, and is further preferably ammonium persulfate.
The polyvinyl acetate is prepared by a soap-free emulsion polymerization method, and on the premise that the raw material components are provided by the invention, a person skilled in the art can refer to the prior art to obtain specific synthesis steps by the principle of the soap-free emulsion polymerization method. Therefore, the technical solutions provided below of the present invention are not meant to be a unique specification or limitation of the preparation method of the present invention.
However, at the same time, it should be clear to those skilled in the art that the preparation process also has a certain influence on the preparation effect of PVA with low polymerization degree, especially on the polymerization degree, monomer conversion rate, etc. of the product, so in order to obtain PVA products with better performance and lower polymerization degree, the present invention provides a preferable technical scheme in a matching way, and the preparation of polyvinyl acetate by soap-free emulsion polymerization method includes the following steps:
preheating deionized water and keeping the temperature to 70-80 ℃, adding an initiator and a chain transfer agent into the deionized water, adding a vinyl acetate monomer in a dropwise manner, stirring in the dropwise process, and continuing to react for 1-3 hours after the dropwise is finished; and after the reaction time is up, collecting emulsion obtained by the reaction, then adopting a freezing demulsification method to carry out polymer precipitation on the emulsion obtained by the reaction, and cleaning and drying the polymer precipitation to obtain the polyvinyl acetate.
Generally, the vinyl acetate monomer is added in a dropwise manner, and the dropwise time is preferably controlled within 1-3 hours when the adding mass of the vinyl acetate monomer is 100-200 g under laboratory conditions; in actual industrial production, the scale-up can be properly carried out according to actual process conditions so as to ensure industrial efficiency.
Wherein, the method for freezing and demulsification can be selected by a person skilled in the art according to the prior art of soap-free emulsion polymerization, so as to better illustrate the invention and provide a technical scheme for reference. The freezing demulsification method specifically comprises the following steps: freezing the emulsion obtained by the reaction at the temperature of-20 to 0 ℃ for 6 to 12 hours, and then thawing at normal temperature to obtain the polyvinyl acetate.
The low polymerization degree PVA is obtained by alcoholysis of the prepared polyvinyl acetate, and a person skilled in the art can refer to the prior art of alcoholysis of the polyvinyl acetate to obtain a specific alcoholysis step; therefore, the technical solutions provided below of the present invention are not meant to be a unique specification or limitation of the preparation method of the present invention.
In order to better illustrate the invention and provide a technical scheme for reference, the preparation method of the polyvinyl acetate is characterized in that the polyvinyl acetate is subjected to alcoholysis to obtain PVA with low polymerization degree, and the PVA with low polymerization degree comprises the following steps in parts by weight:
adding 30 parts of prepared polyvinyl acetate into 150-270 parts of methanol, and heating to 40-50 ℃ to completely dissolve the polyvinyl acetate; then adding 3-10 parts of sodium hydroxide methanol solution, stirring and reacting for 0.5-2 hours, washing and drying the obtained reactant after the reaction time reaches, and obtaining the PVA with low polymerization degree.
Typically, the concentration of the sodium hydroxide methanol solution is that used in conventional alcoholysis in the prior art; for better illustrating the invention, and providing a technical scheme for reference: the concentration of the sodium hydroxide methanol solution is 3-5 wt%.
The PVA with low polymerization degree prepared by the technical scheme has the polymerization degree as low as 38, and the monomer conversion rate of vinyl acetate is not lower than 90%.
Further, the chain transfer agent is added in the present invention because the chain transfer agent is effective to radical transfer the growing radicals, thereby controlling the degree of polymerization of the polymer. Therefore, in order to produce PVA with a low degree of polymerization, it is necessary to add a certain amount of a chain transfer agent. It is generally believed that the lower the degree of polymerization of the desired target product, the higher the chain transfer capability requirement, i.e., the higher the chain transfer constant, of the corresponding desired chain transfer agent to be added. However, the inventors of the present invention have found through comparative experiments that in the actual process for producing PVA with low polymerization degree, in order to obtain PVA with low polymerization degree, it is necessary to consider a series of problems such as cost of raw materials, post-treatment of products, etc. in addition to the target polymerization degree, thereby improving productivity.
The inventor of the invention selects acetone and chloroform with lower chain transfer constant and mercaptan and carbon tetrachloride with higher chain transfer constant to carry out control experiments respectively:
when the polyvinyl acetate is prepared by a soap-free emulsion polymerization method, the raw materials mainly comprise the following components in parts by weight:
the chain transfer agent is any one of acetone, chloroform, mercaptan and carbon tetrachloride.
The control experiment shows that:
TABLE 1 Effect of chain transfer agent on polymerization reactions
It is evident that, at the same amount, the thiol has the highest chain transfer constant as chain transfer agent, but the degree of polymerization of the PVA finally produced is not the lowest; meanwhile, carbon tetrachloride can be used as a chain transfer agent to prepare PVA with the lowest polymerization degree, but the actual monomer conversion rate is lower than 50%, and the production efficiency is poor; acetone as a chain transfer agent has the lowest chain transfer constant, so that the polymerization degree of PVA obtained by the preparation can be only 180 at the lowest. Meanwhile, trichloromethane and mercaptan have better monomer conversion rate, but the mercaptan has strong and unpleasant smell and is not easy to remove, and extra production cost is required to be increased in industrial production. Therefore, the trichloromethane can still prepare PVA with low polymerization degree on the premise of low chain transfer constant, and the monomer conversion rate is high, so that the trichloromethane is suitable for industrial production.
Further, when the chain transfer agent is preferably chloroform, the inventors of the present invention have further studied and found that by improving the mode of adding chloroform, it is possible to further facilitate obtaining PVA of a low polymerization degree having a narrower molecular weight distribution, thereby improving the performance of the produced PVA of a low polymerization degree:
the polyvinyl acetate is prepared by a soap-free emulsion polymerization method, and comprises the following steps:
preheating deionized water and keeping the temperature to 70-80 ℃, adding an initiator into the deionized water, then adding a vinyl acetate monomer and chloroform in a dropwise manner, stirring in the dropwise process, and continuing stirring for reaction for 1-3 hours after the dropwise is finished; and after the reaction time is up, polymer precipitation is carried out on the emulsion obtained by the reaction by adopting a freezing demulsification method, and the polymer precipitation is cleaned and dried to obtain the polyvinyl acetate.
Wherein, the vinyl acetate monomer and the chloroform are added in a dropwise manner, the dropwise rate is preferably controlled within 1-3 hours when the adding mass of the vinyl acetate monomer is 100-200 g under laboratory conditions, and the dropwise time is preferably controlled within 1-3 hours when the adding mass of the chloroform is 20-80 g; in actual industrial production, the time can be properly shortened according to actual process conditions to ensure industrial efficiency.
In the prior art, the chain transfer agent is selected to be added at one time, and at this time, the polymerization temperature is at a lower level in the early stage of the polymerization reaction, mainly because a mixed system is formed between water and chloroform, so that the azeotropic point is lower, and the reflux phenomenon appears when a reflux pipe is arranged in a container. As the reaction proceeds, polyvinyl acetate is gradually produced, and thus the azeotropic point is raised, the mechanism of which is as follows:
△T＝K f. C/M
wherein K is f As the characteristic constants of the solvents, C and M are the concentration of the solution and the molecular weight of the polymer, respectively, it can be seen from the relationship in the formula that the azeotropic point of the solution increases with increasing polymer concentration. Thus, as the polymerization proceeds, the concentration of polyvinyl acetate gradually increases, and the temperature of the system slowly increases.
By improving the preparation process, when chloroform and a monomer are continuously added together, the temperature monitoring shows that the system temperature is not obviously changed. Since a constant reaction temperature is advantageous for obtaining PVA with a narrower molecular weight distribution, the continuous dropwise addition of chloroform together with the monomer is more advantageous for obtaining PVA with high performance than the single addition of chloroform.
Further, in order to study the influence of the addition amount of the initiator, the polymerization temperature, the addition amount of chloroform, and the addition amount of the monomer on the polymerization degree of PVA as main influencing factors, the inventors of the present invention devised orthogonal experiments for the above 4 influencing factors:
TABLE 2 results of orthogonal experiments
Orthogonal experiments and their results are shown, as can be seen from the table: PVA has the relatively highest degree of polymerization when the initiator is used in an amount of 1.0 part, the polymerization temperature is 70 ℃, the chloroform is used in an amount of 4 parts, and the monomer is used in an amount of 40 parts; when the initiator amount is 1.0 part, the polymerization temperature is 75 ℃, the chloroform amount is 6 parts, and the monomer is 20 parts, the PVA has the relatively lowest polymerization degree; among the four influencing factors, the use amount of chloroform has the greatest influence on the polymerization degree of PVA, and the influence of the polymerization temperature and the monomer concentration and the initiator is the smallest. Wherein K is the sum of experimental results, and R is very bad.
For this reason, the effect of the amount of chloroform on the polymerization degree of PVA was further studied specifically, and as a result, as shown in FIG. 2 of the specification, it was apparent that the polymerization degree of PVA was reduced from 372 to 26 as the amount of chloroform was increased from 0 to 50% by weight (based on the total amount of monomer mass). Therefore, the polymerization degree of PVA can be controlled by the addition amount of chloroform.
However, when the chloroform content is too high (50 wt% or more based on the total amount of the monomers), the polymerization reaction becomes unstable, and an emulsion cannot be obtained. Therefore, when chloroform was used as the chain transfer agent, the mass ratio of vinyl acetate monomer to chloroform was 10: (1 to 4) preferably, more preferably, 10: (1-3).
The invention has the following beneficial effects:
1. the invention designs and optimizes a method for preparing PVA with low polymerization degree by soap-free emulsion polymerization through comparison and gradient experiments, and the preparation method has higher monomer conversion rate and can prepare PVA with polymerization degree as low as 38.
2. The invention preferably limits the selection of the chain transfer agent through a control experiment so as to be more suitable for industrial production.
3. In one preferable technical scheme of the invention, the preparation process is further improved, and PVA with narrower molecular weight distribution and low polymerization degree can be prepared.
4. The invention can control the polymerization degree of PVA by regulating and controlling the addition amount of the chain transfer agent, and has the advantages of novel method, unique route and suitability for industrial production.
Drawings
FIG. 1 is a nuclear magnetic resonance chart of PVA with low degree of polymerization produced in example 5 of the present invention.
FIG. 2 is a linear graph showing the effect of chloroform usage on PVA polymerization according to the present invention.
FIG. 3 is a graph showing the linear comparison of the effect of the mode of addition of chloroform according to the invention on the polymerization reaction.
Detailed Description
The invention is further illustrated by the following examples in conjunction with the accompanying drawings. It should be noted that the examples given should not be construed as limiting the scope of the present invention, but rather as merely providing for the benefit of this disclosure.
The following examples and comparative examples used the following types and sources of reagents:
vinyl acetate: industrial grade, sichuan vinylon plant; ammonium persulfate: analytically pure, methanol: analytically pure, manufactured by kelong chemical reagent factories; sodium hydroxide: analytically pure, tianjin, ruijin chemicals limited; acetone: analytically pure, manufactured by kelong chemical reagent factories; thiol: analytically pure, chengdobester reagent Co., ltd; trichloromethane: analytically pure, manufactured by kelong chemical reagent factories; deionized water: and (5) self-making.
The dried polyvinyl alcohol was measured for its intrinsic viscosity [ eta ] at 30℃by means of a Ubbelohde viscometer, and the molecular weight was calculated according to the following formula, and converted into a degree of polymerization.
[η]＝0.0665M 0.64
Examples 1 to 9
Examples 1 to 9 were prepared according to the proportions in the following table:
table 3 example data
Wherein the initiator is ammonium persulfate;
the total weight of the vinyl acetate monomer and deionized water is 100 parts, and the weight parts of the deionized water are determined by the parts of the monomers in the table;
preparation of polyvinyl acetate:
preheating deionized water and keeping the temperature to the polymerization temperature in Table 3, adding an initiator into the deionized water, adding a vinyl acetate monomer and chloroform in a dropwise manner, stirring in the dropwise process, and continuing stirring for 2.5 hours after the dropwise is finished; after the reaction time is up, polymer precipitation is carried out on the emulsion obtained by the reaction by adopting a freezing demulsification method, and the polymer precipitation is cleaned and dried to obtain polyvinyl acetate;
alcoholysis:
adding 30 parts of prepared polyvinyl acetate into 270 parts of methanol, and heating to 45 ℃ to completely dissolve the polyvinyl acetate; then adding 7 parts of 5wt% sodium hydroxide methanol solution, stirring and reacting for 2 hours, washing and drying the obtained reactant after the reaction time reaches, and obtaining the PVA with low polymerization degree.
The polymerization degree data of the resulting PVA with a low polymerization degree were prepared as shown in Table 3.
Example 10
The method for preparing PVA with low polymerization degree by soap-free emulsion polymerization comprises the following steps in parts by weight:
(1) Preparation of materials
The chain transfer agent is acetone;
the initiator is ammonium persulfate;
(2) Preparation of polyvinyl acetate
Preheating deionized water and keeping the temperature to 80 ℃, adding an initiator into the deionized water, then adding a vinyl acetate monomer and acetone in a dropwise manner, stirring in the dropwise process, and continuing stirring for reaction for 2.5 hours after the dropwise is finished; after the reaction time is up, polymer precipitation is carried out on the emulsion obtained by the reaction by adopting a freezing demulsification method, and the polymer precipitation is cleaned and dried to obtain polyvinyl acetate;
(3) Alcoholysis of
Adding 30 parts of prepared polyvinyl acetate into 270 parts of methanol, and heating to 45 ℃ to completely dissolve the polyvinyl acetate; then adding 7 parts of 5wt% sodium hydroxide methanol solution, stirring and reacting for 2 hours, washing and drying the obtained reactant after the reaction time reaches, and obtaining the PVA with low polymerization degree.
The polymerization degree of the PVA with low polymerization degree obtained by measurement is 180, and the monomer conversion rate is 90%.
Example 11
The method for preparing PVA with low polymerization degree by soap-free emulsion polymerization comprises the following steps in parts by weight:
(1) Preparation of materials
The chain transfer agent is mercaptan;
the initiator is ammonium persulfate;
(2) Preparation of polyvinyl acetate
Preheating deionized water and keeping the temperature to 80 ℃, adding an initiator into the deionized water, then adding a vinyl acetate monomer and acetone in a dropwise manner, stirring in the dropwise process, and continuing stirring for reaction for 2.5 hours after the dropwise is finished; after the reaction time is up, polymer precipitation is carried out on the emulsion obtained by the reaction by adopting a freezing demulsification method, and the polymer precipitation is cleaned and dried to obtain polyvinyl acetate;
(3) Alcoholysis of
Adding 30 parts of prepared polyvinyl acetate into 270 parts of methanol, and heating to 45 ℃ to completely dissolve the polyvinyl acetate; then adding 7 parts of 5wt% sodium hydroxide methanol solution, stirring and reacting for 2 hours, and washing and drying the obtained reactant after the reaction time reaches, thus obtaining the PVA with low polymerization degree.
The polymerization degree of the PVA with low polymerization degree obtained by measurement was 38, and the monomer conversion was 95%.
Example 12
The method for preparing PVA with low polymerization degree by soap-free emulsion polymerization comprises the following steps in parts by weight:
(1) Preparation of materials
The chain transfer agent is chloroform;
the initiator is potassium persulfate;
(2) Preparation of polyvinyl acetate
Preheating deionized water and keeping the temperature to 80 ℃, adding an initiator into the deionized water, then adding a vinyl acetate monomer and acetone in a dropwise manner, stirring in the dropwise process, and continuing stirring for reaction for 1 hour after the dropwise is finished; after the reaction time is up, polymer precipitation is carried out on the emulsion obtained by the reaction by adopting a freezing demulsification method, and the polymer precipitation is cleaned and dried to obtain polyvinyl acetate;
the freezing demulsification method specifically comprises the following steps: freezing the emulsion obtained by the reaction at the temperature of minus 20 ℃ for 12 hours, and then thawing at normal temperature to obtain polyvinyl acetate;
(3) Alcoholysis of
Adding 30 parts of prepared polyvinyl acetate into 180 parts of methanol, and heating to 50 ℃ to completely dissolve the polyvinyl acetate; then adding 5 parts of 5wt% sodium hydroxide methanol solution, stirring and reacting for 1h, and washing and drying the obtained reactant after the reaction time reaches, thus obtaining the PVA with low polymerization degree.
Example 13
The method for preparing PVA with low polymerization degree by soap-free emulsion polymerization comprises the following steps in parts by weight:
(1) Preparation of materials
The chain transfer agent is chloroform;
the initiator is ammonium persulfate;
(2) Preparation of polyvinyl acetate
Preheating deionized water and keeping the temperature to 75 ℃, adding an initiator into the deionized water, then adding a vinyl acetate monomer and acetone in a dropwise manner, stirring in the dropwise process, and continuing stirring for reaction for 2 hours after the dropwise is finished; after the reaction time is up, polymer precipitation is carried out on the emulsion obtained by the reaction by adopting a freezing demulsification method, and the polymer precipitation is cleaned and dried to obtain polyvinyl acetate;
the freezing demulsification method specifically comprises the following steps: freezing the emulsion obtained by the reaction at the temperature of minus 10 ℃ for 6 hours, and then thawing at normal temperature to obtain polyvinyl acetate;
(3) Alcoholysis of
Adding 30 parts of the prepared polyvinyl acetate into 240 parts of methanol, and heating to 40 ℃ to completely dissolve the polyvinyl acetate; then 10 parts of sodium hydroxide methanol solution with the concentration of 3wt percent is added, the mixture is stirred and reacts for 1.5 hours, and after the reaction time reaches, the obtained reactant is washed and dried, thus obtaining the PVA with low polymerization degree.
Comparative example 1
The method for preparing PVA with low polymerization degree by soap-free emulsion polymerization comprises the following steps in parts by weight:
(1) Preparation of materials
The chain transfer agent is carbon tetrachloride;
the initiator is ammonium persulfate;
(2) Preparation of polyvinyl acetate
Preheating deionized water and keeping the temperature to 70 ℃, adding an initiator into the deionized water, then adding a vinyl acetate monomer and acetone in a dropwise manner, stirring in the dropwise process, and continuing stirring for reaction for 2.5 hours after the dropwise is finished; after the reaction time is up, polymer precipitation is carried out on the emulsion obtained by the reaction by adopting a freezing demulsification method, and the polymer precipitation is cleaned and dried to obtain polyvinyl acetate;
(3) Alcoholysis of
Adding 30 parts of prepared polyvinyl acetate into 270 parts of methanol, and heating to 45 ℃ to completely dissolve the polyvinyl acetate; then adding 7 parts of 5wt% sodium hydroxide methanol solution, stirring and reacting for 2 hours, and washing and drying the obtained reactant after the reaction time reaches, thus obtaining the PVA with low polymerization degree.
The polymerization degree of the PVA with low polymerization degree obtained by measurement was 20, and the monomer conversion was 48%.
Claims (4)
1. A method for preparing polyvinyl alcohol with a polymerization degree of 80 by soap-free emulsion polymerization is characterized in that the method comprises the steps of preparing polyvinyl acetate by a soap-free emulsion polymerization method, and carrying out alcoholysis on the prepared polyvinyl acetate to obtain PVA with a low polymerization degree;
the polyvinyl acetate is prepared by a soap-free emulsion polymerization method, and the raw materials of the polyvinyl acetate mainly comprise the following components in parts by weight:
wherein the initiator is ammonium persulfate;
the chain transfer agent is chloroform;
the polyvinyl acetate is prepared by a soap-free emulsion polymerization method, and comprises the following steps:
preheating deionized water and keeping the temperature to 75 ℃, adding an initiator into the deionized water, then adding a vinyl acetate monomer and chloroform in a dropwise manner, stirring in the dropwise process, and continuing stirring for reaction for 2.5 hours after the dropwise is finished; and after the reaction time is up, polymer precipitation is carried out on the emulsion obtained by the reaction by adopting a freezing demulsification method, and the polymer precipitation is cleaned and dried to obtain the polyvinyl acetate.
2. The method according to claim 1, characterized in that the method of freeze demulsification comprises the following steps: freezing the emulsion obtained by the reaction at the temperature of 0 to minus 20 ℃ for 6 to 12 hours, and then thawing at normal temperature to obtain the polyvinyl acetate.
3. The method of claim 1, wherein the low polymerization degree PVA is obtained by alcoholysis of the prepared polyvinyl acetate, and comprises the following steps in parts by weight:
adding 30 parts of prepared polyvinyl acetate into 150-270 parts of methanol, and heating to 40-50 ℃ to completely dissolve the polyvinyl acetate; then adding 3-10 parts of sodium hydroxide methanol solution, stirring and reacting for 0.5-2 hours, and after the reaction time reaches, washing and drying the obtained reactant to obtain the PVA with low polymerization degree.
4. A method according to claim 3, characterized in that: the concentration of the sodium hydroxide methanol solution is 3-5 wt%.
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| GB894889A (en) * | 1959-08-07 | 1962-04-26 | Kurashiki Rayon Kk | Method of manufacturing polyvinyl acetate and alcohol |
| JPS63278911A (en) * | 1987-05-09 | 1988-11-16 | Nippon Synthetic Chem Ind Co Ltd:The | Manufacture of ultra-low-molecular weight polyvinyl alcohol |
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- 2022-01-11 CN CN202210028968.XA patent/CN114507307B/en active Active
- 2022-01-11 CN CN202210928961.3A patent/CN115304696B/en active Active
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| GB894889A (en) * | 1959-08-07 | 1962-04-26 | Kurashiki Rayon Kk | Method of manufacturing polyvinyl acetate and alcohol |
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| CN103030723A (en) * | 2011-09-29 | 2013-04-10 | 中国石油化工集团公司 | Preparation method of polyvinyl alcohol (PVA) with medium polymerization degree |
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| CN115260351A (en) | 2022-11-01 |
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| CN115304696B (en) | 2023-10-13 |
| CN115304696A (en) | 2022-11-08 |
| CN115197352B (en) | 2023-10-27 |
| CN114507307B (en) | 2022-08-23 |
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