CN112707983A - Low-viscosity polyvinyl alcohol and production method thereof - Google Patents
Low-viscosity polyvinyl alcohol and production method thereof Download PDFInfo
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- CN112707983A CN112707983A CN201911019273.XA CN201911019273A CN112707983A CN 112707983 A CN112707983 A CN 112707983A CN 201911019273 A CN201911019273 A CN 201911019273A CN 112707983 A CN112707983 A CN 112707983A
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- 229920002451 polyvinyl alcohol Polymers 0.000 title claims abstract description 72
- 239000004372 Polyvinyl alcohol Substances 0.000 title claims abstract description 71
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 35
- 238000000034 method Methods 0.000 claims abstract description 21
- 230000014759 maintenance of location Effects 0.000 claims abstract description 16
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 126
- 238000006116 polymerization reaction Methods 0.000 claims description 122
- XTXRWKRVRITETP-UHFFFAOYSA-N Vinyl acetate Chemical compound CC(=O)OC=C XTXRWKRVRITETP-UHFFFAOYSA-N 0.000 claims description 53
- 238000006136 alcoholysis reaction Methods 0.000 claims description 49
- ZCHPKWUIAASXPV-UHFFFAOYSA-N acetic acid;methanol Chemical compound OC.CC(O)=O ZCHPKWUIAASXPV-UHFFFAOYSA-N 0.000 claims description 39
- 229920002554 vinyl polymer Polymers 0.000 claims description 38
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 27
- 229920002689 polyvinyl acetate Polymers 0.000 claims description 27
- 239000011118 polyvinyl acetate Substances 0.000 claims description 24
- 239000002245 particle Substances 0.000 claims description 19
- 239000007788 liquid Substances 0.000 claims description 18
- 238000002156 mixing Methods 0.000 claims description 18
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 16
- 239000003999 initiator Substances 0.000 claims description 13
- 230000008569 process Effects 0.000 claims description 12
- 239000010408 film Substances 0.000 claims description 10
- 238000010528 free radical solution polymerization reaction Methods 0.000 claims description 9
- GRONZTPUWOOUFQ-UHFFFAOYSA-M sodium;methanol;hydroxide Chemical compound [OH-].[Na+].OC GRONZTPUWOOUFQ-UHFFFAOYSA-M 0.000 claims description 9
- 230000009471 action Effects 0.000 claims description 8
- 238000007664 blowing Methods 0.000 claims description 8
- 238000001035 drying Methods 0.000 claims description 8
- VRGKJPUAYZXEGD-UHFFFAOYSA-N ethenyl acetate;methanol Chemical compound OC.CC(=O)OC=C VRGKJPUAYZXEGD-UHFFFAOYSA-N 0.000 claims description 8
- 238000010992 reflux Methods 0.000 claims description 8
- 239000010409 thin film Substances 0.000 claims description 6
- ZACVGCNKGYYQHA-UHFFFAOYSA-N 2-ethylhexoxycarbonyloxy 2-ethylhexyl carbonate Chemical compound CCCCC(CC)COC(=O)OOC(=O)OCC(CC)CCCC ZACVGCNKGYYQHA-UHFFFAOYSA-N 0.000 claims description 5
- 238000001704 evaporation Methods 0.000 claims description 5
- 230000008020 evaporation Effects 0.000 claims description 5
- 239000000203 mixture Substances 0.000 claims description 5
- 239000002904 solvent Substances 0.000 claims description 5
- AVXWWBFBRTXBRM-UHFFFAOYSA-N 3-bromopyridine-4-carboxylic acid Chemical compound OC(=O)C1=CC=NC=C1Br AVXWWBFBRTXBRM-UHFFFAOYSA-N 0.000 claims description 4
- 238000004321 preservation Methods 0.000 claims description 4
- 239000002994 raw material Substances 0.000 claims description 4
- 238000010298 pulverizing process Methods 0.000 claims description 3
- NOBYOEQUFMGXBP-UHFFFAOYSA-N (4-tert-butylcyclohexyl) (4-tert-butylcyclohexyl)oxycarbonyloxy carbonate Chemical compound C1CC(C(C)(C)C)CCC1OC(=O)OOC(=O)OC1CCC(C(C)(C)C)CC1 NOBYOEQUFMGXBP-UHFFFAOYSA-N 0.000 claims description 2
- 239000003054 catalyst Substances 0.000 claims description 2
- 239000012934 organic peroxide initiator Substances 0.000 claims description 2
- 125000000864 peroxy group Chemical group O(O*)* 0.000 claims description 2
- 239000003505 polymerization initiator Substances 0.000 claims description 2
- YPVDWEHVCUBACK-UHFFFAOYSA-N propoxycarbonyloxy propyl carbonate Chemical compound CCCOC(=O)OOC(=O)OCCC YPVDWEHVCUBACK-UHFFFAOYSA-N 0.000 claims description 2
- 238000000746 purification Methods 0.000 claims description 2
- 238000000926 separation method Methods 0.000 claims description 2
- AQKYLAIZOGOPAW-UHFFFAOYSA-N 2-methylbutan-2-yl 2,2-dimethylpropaneperoxoate Chemical compound CCC(C)(C)OOC(=O)C(C)(C)C AQKYLAIZOGOPAW-UHFFFAOYSA-N 0.000 claims 1
- 238000003825 pressing Methods 0.000 claims 1
- 238000009776 industrial production Methods 0.000 abstract description 3
- 238000000465 moulding Methods 0.000 abstract description 3
- 239000000428 dust Substances 0.000 description 19
- 239000000463 material Substances 0.000 description 15
- -1 smoothness Substances 0.000 description 5
- 238000009833 condensation Methods 0.000 description 4
- 230000005494 condensation Effects 0.000 description 4
- 239000000843 powder Substances 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 3
- 238000011109 contamination Methods 0.000 description 3
- 238000000227 grinding Methods 0.000 description 3
- 239000000123 paper Substances 0.000 description 3
- 238000005086 pumping Methods 0.000 description 3
- 239000000654 additive Substances 0.000 description 2
- 239000000853 adhesive Substances 0.000 description 2
- 230000001070 adhesive effect Effects 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 238000010276 construction Methods 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000000835 fiber Substances 0.000 description 2
- 239000000543 intermediate Substances 0.000 description 2
- 150000002978 peroxides Chemical class 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 238000011084 recovery Methods 0.000 description 2
- 239000004753 textile Substances 0.000 description 2
- YQTCQNIPQMJNTI-UHFFFAOYSA-N 2,2-dimethylpropan-1-one Chemical group CC(C)(C)[C]=O YQTCQNIPQMJNTI-UHFFFAOYSA-N 0.000 description 1
- 229920002978 Vinylon Polymers 0.000 description 1
- 230000006978 adaptation Effects 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 239000000084 colloidal system Substances 0.000 description 1
- 239000002537 cosmetic Substances 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 239000002270 dispersing agent Substances 0.000 description 1
- 239000003814 drug Substances 0.000 description 1
- 238000009713 electroplating Methods 0.000 description 1
- 239000003995 emulsifying agent Substances 0.000 description 1
- 239000004744 fabric Substances 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000012567 medical material Substances 0.000 description 1
- 238000005272 metallurgy Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 238000007639 printing Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 238000012216 screening Methods 0.000 description 1
- 238000004513 sizing Methods 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
- 229920003169 water-soluble polymer Polymers 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
- 239000002023 wood Substances 0.000 description 1
Classifications
-
- 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
- C08F118/00—Homopolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an acyloxy radical of a saturated carboxylic acid, of carbonic acid or of a haloformic acid
- C08F118/02—Esters of monocarboxylic acids
- C08F118/04—Vinyl esters
- C08F118/08—Vinyl acetate
-
- 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
- C08F2/04—Polymerisation in solution
- C08F2/06—Organic solvent
-
- 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
- C08F6/00—Post-polymerisation treatments
- C08F6/001—Removal of residual monomers by physical means
- C08F6/003—Removal of residual monomers by physical means from polymer solutions, suspensions, dispersions or emulsions without recovery of the polymer therefrom
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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)
- Dispersion Chemistry (AREA)
- Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
Abstract
The invention belongs to the technical field of polyvinyl alcohol, and particularly relates to low-viscosity polyvinyl alcohol and a production method thereof. The ratio of the 10-20 mesh retention to the 10-mesh retention of the polyvinyl alcohol is 0.6-1.2. The invention realizes the industrial production of the ultra-low viscosity PVA02 series, and improves the molding methods of other low viscosity polyvinyl alcohol products, namely PVA04 series and PVA03 series.
Description
Technical Field
The invention belongs to the technical field of polyvinyl alcohol, and particularly relates to low-viscosity polyvinyl alcohol and a production method thereof.
Background
Polyvinyl alcohol (PVA) is a water-soluble high molecular polymer and is prepared by carrying out alcoholysis polymerization on vinyl acetate. The polyvinyl alcohol has better strong adhesion, flexibility of a coating film, smoothness, oil resistance, solvent resistance, colloid protection, gas barrier property, wear resistance and water resistance after special treatment. Therefore, the polyvinyl alcohol has wide application, and the downstream products thereof comprise vinylon, coatings, adhesives, fiber pulp, paper treatment agents, emulsifiers, dispersants, films, medical materials and construction automobile modified materials, and the application fields relate to the industries of textile, food, medicine, construction, wood processing, paper making, printing, agriculture, metallurgy and the like ("the production status and market prospect of polyvinyl alcohol", weshandon et al, chemical intermediates, 2006, 12 th, page 4, left column, 1 st line 1 to 2 nd line 5, and published 2006, 12 th and 31 th).
The performance of polyvinyl alcohol is determined by factors such as polymerization degree, viscosity and alcoholysis degree. Generally, the degree of polymerization varies in direct proportion to the viscosity index ("current state of production and market prospect analysis of polyvinyl alcohol", jamenfen, etc., yunnan chemical, vol.39, No. 5, p.36, right column, No. 1, lines 3-5, publication date 2012, 10, 31).
At present, the development trend of the world polyvinyl alcohol industry is to develop into two stages of high and low, namely, a high-polymerization degree (high viscosity) and a high-alcoholysis degree (high viscosity) high-precision product and a low-polymerization degree (low viscosity) and low-alcoholysis degree special product (the current production situation and market prospect of polyvinyl alcohol, Weshaodong et al, chemical intermediates, No. 12 in 2006, No. 4, left column, No. 3, lines 2-5, and published 2006, No. 12 and 31).
Low viscosity polyvinyl alcohol means a viscosity of 6.0 (10)-3pa · s) or less (measured at 4% by mass at room temperature) ("water-soluble polymer polyvinyl alcohol type trademark and use", WanhonanPaper chemicals, stage 3 of 2003, page 45, right column, paragraph 4, lines 3-4, published date 2003, 12 months and 31 days). The low-viscosity polyvinyl alcohol products mainly comprise series products such as PVA05, PVA04, PVA03 and the like, the main products comprise 098-05, 088-05, 098-04, 088-03 and the like, and the low-viscosity polyvinyl alcohol products are mainly used in the fields of textile sizing agents, medical cosmetics, adhesives, paper processing, building additives, electrolytic plating additives and the like (CN 104558319A).
However, when the conventional process is used for producing the low-viscosity polyvinyl alcohol product, the product is difficult to form and has serious pulverization, and the production of the low-viscosity polyvinyl alcohol product is always restricted.
In order to solve the problem, patent document CN104558319A discloses a method for improving the molding of low-viscosity polyvinyl alcohol, which uses vinyl acetate as a raw material and methanol as a solvent to produce polyvinyl acetate by solution polymerization, wherein the polymerization rate of the vinyl acetate is 90% to 99%, and the concentration of the alcoholysis polyvinyl acetate is 40% to 60%, so as to achieve the purpose of improving the molding of low-viscosity PVA. The method has certain effect on low-viscosity PVA05 series and PVA04 series, but has limited effect on PVA03 series and is not applicable to PVA02 series with low viscosity because a belt alcoholysis machine is generally adopted in an alcoholysis process in the production process of polyvinyl alcohol and has limited length, and a polyvinyl alcohol pre-blank cannot be solidified when the method is used for production.
Disclosure of Invention
In view of the above, the present invention provides a polyvinyl alcohol.
In order to achieve the purpose, the technical scheme of the invention is as follows:
the ratio of 10-20 mesh retention to 10 mesh retention of polyvinyl alcohol is 0.6-1.2.
Further, the bulk density of the polyvinyl alcohol is 0.4 to 0.5g/mL (the density of water is 1g/mL, the bulk density is 0.4 to 0.5 g/mL).
The bulk density is a mass per unit volume obtained immediately after filling a container with a material freely.
The invention also aims to protect the production method of the polyvinyl alcohol, which takes vinyl acetate as a raw material and methanol as a solvent, comprises the steps of polymerization, rectification and alcoholysis, wherein the polymerization rate of the vinyl acetate is 90-99%, and the polyvinyl acetate-methanol solution from the bottom of a rectifying tower is placed in a film evaporator to be treated until the mass concentration of the polyvinyl acetate is 48-65%.
The inventor unexpectedly discovers that in the research process, by using vinyl acetate as a raw material and methanol as a solvent, the method comprises the steps of polymerization, rectification and alcoholysis, wherein the polymerization rate of the vinyl acetate is 90-99%, and a polyvinyl acetate-methanol solution from the bottom of a rectifying tower is placed in a thin film evaporator to be treated until the mass concentration of the polyvinyl acetate is 48-65%; the method for producing the polyvinyl alcohol can realize the production of PVA02 series.
Further, the thin film evaporator is a wiped film evaporator.
Further, the temperature of the thin film evaporator is controlled to be 70-90 ℃, and the evaporation capacity is controlled to be 10-25 wt%.
Further, the amount of the polymerization initiator is 0.01-0.5% by mass of the vinyl acetate.
Further, the initiator adopts an organic peroxide initiator.
Further, the organic peroxy initiator includes one or more of bis (2-ethylhexyl) peroxydicarbonate, bis (4-tert-butylcyclohexyl) peroxydicarbonate, bis (3,5, 5-trimethylhexanoyl) peroxide, dipropyl peroxydicarbonate, and pivaloyl peroxypivalate.
Further, the organic peroxy-type initiator includes bis (2-ethylhexyl) peroxydicarbonate.
Further, the temperature of the polymerization reaction is 60-70 ℃ and the time is 2.5-6 hours.
Further, the rectification is to introduce methanol steam into a rectifying tower to realize the separation and purification of the polyvinyl acetate, the temperature is controlled to be 60-68 ℃, and the reflux ratio of the rectifying tower is 0.1-1.2.
And further, the alcoholysis is carried out by mixing a polyvinyl acetate methanol solution of a polymerization product with a 30g/L NaOH methanol solution and then carrying out alcoholysis, wherein the molar ratio of NaOH to polyvinyl acetate is 0.001:1-0.01:1, the alcoholysis temperature is 30-45 ℃, and the alcoholysis time is 20-40 minutes.
Further, the production method of the polyvinyl alcohol also comprises preheating at 55-60 ℃ before polymerization.
Furthermore, the production method of the polyvinyl alcohol also comprises the steps of crushing, squeezing and drying, wherein the drying temperature is 90-120 ℃, and the drying time is 3-5 hours.
Further, the production method of the polyvinyl alcohol comprises the following steps:
after passing through a preheater, a vinyl acetate methanol solution with the mass concentration of 30-40% enters a first polymerization kettle, and solution polymerization is carried out under the action of an initiator; when the polymerization rate reaches 25.0% -35.0%, the polymerization liquid is sent into a second polymerization kettle for continuous polymerization, so that the polymerization rate is increased to 90% -99%, and the polymerization reaction of the vinyl acetate is carried out in a methanol solution; arranging a countercurrent condenser on the polymerization kettle to condense the evaporated vinyl acetate and methanol vapor and return the condensed vapor to the polymerization kettle, and adopting jacket warm water for heat preservation to stabilize the polymerization reaction temperature at 60-70 ℃, wherein the total polymerization time is 2.5-6 hours, and the polymerization rate of vinyl acetate is 90-99%;
adding the polyvinyl acetate-methanol solution from the second polymerization kettle into a rectifying tower, blowing methanol steam from the bottom of the tower to distill an azeotropic liquid of unreacted vinyl acetate forming methanol, and taking out the methanol solution of the polyvinyl acetate from the bottom of the tower; the polyvinyl acetate-methanol solution coming out from the tower bottom enters a film evaporator to be processed until the mass concentration of polyvinyl acetate is 48-65%;
conveying the polyvinyl acetate-methanol solution to a mixer through a conveying pump, centrifugally mixing the polyvinyl acetate-methanol solution with 30g/L NaOH-methanol solution in the mixer, uniformly mixing, conveying the mixture on a belt of an alcoholysis machine, conveying the mixture on the belt, wherein the alcoholysis reaction temperature is 35-45 ℃, and the alcoholysis time is 25-40 minutes; and (3) PVA is precipitated and solidified in the conveying process, a plate-shaped object is formed at the outlet of the alcoholysis machine, then the plate-shaped object is crushed into strips by a first crusher, the strips are crushed into particles by a second crusher, the particles are sent to a squeezer, and then the particles are sent to a dryer for drying, so that the catalyst is obtained.
The invention has the beneficial effects that:
the invention realizes the industrial production of the ultra-low viscosity PVA02 series.
The invention improves the forming methods of other low-viscosity polyvinyl alcohol products PVA04 series and PVA03 series.
The method for producing the low-viscosity polyvinyl alcohol has the advantages of good product forming performance, greatly reduced product pulverization, reduced product loss and stable production operation. The reuse rate of the reuse liquid can reach 60-90%.
The invention effectively reduces the amount of PVA powder brought into the recovery rectification system along with the waste liquid system, and improves the operation period of the recovery rectification system; after the pressure conveying system operates stably, white pollution of PVA dust to the surrounding environment is effectively reduced; meanwhile, the water quality pollution caused by the 'white' pollution along with rainwater is eliminated.
The invention effectively solves the problems of high pressure feeding failure rate and large loss of low-viscosity products, reduces about 10 tons of materials blown out each year due to pressure feeding failure, and has direct economic benefit of about 15-16 ten thousand per year.
Detailed Description
The examples are provided for better illustration of the present invention, but the present invention is not limited to the examples. Therefore, those skilled in the art should make insubstantial modifications and adaptations to the embodiments of the present invention in light of the above teachings and remain within the scope of the invention.
The following alcoholysis levels and viscosities were as per part 2 of GB/T12010.2-2010 Plastic polyvinyl alcohol Material (PVAL): performance measurement is carried out;
the following whiteness is detected according to GB/T7351-1997 fiber and polyvinyl alcohol resin;
the following methods for measuring bulk density were used: pouring the PVA product into a 100ml dry measuring cylinder by a natural pouring method and weighing;
the following particle size distributions were tested by dry screening, specifically: the PVA product is passed through a series of standard sieves with different mesh sizes, and is divided into a plurality of size fractions, which are respectively weighed to obtain the particle size distribution expressed by mass fraction.
Example 1
The production of the PVA088-04 product comprises the following specific steps:
after passing through a preheater (55-60 ℃), a vinyl acetate-methanol solution with the mass concentration of 50-53% enters a first polymerization kettle, and solution polymerization is carried out under the action of a bis (2-ethylhexyl) peroxydicarbonate initiator with the mass concentration of 0.01-0.5 wt% (based on the mass percentage of vinyl acetate);
when the polymerization rate reaches 25.0-35.0%, the polymerization liquid is sent into a second polymerization kettle for continuous polymerization, so that the polymerization rate is increased to about 90-99%, and the polymerization reaction of the vinyl acetate is carried out in a methanol solution;
arranging a countercurrent condenser on the polymerization kettle to condense the evaporated vinyl acetate and methanol vapor and return the condensed vapor to the polymerization kettle, and adopting jacket warm water for heat preservation to stabilize the polymerization reaction temperature at 65-67 ℃, wherein the total polymerization time is 4.5-5 hours, and the polymerization rate of vinyl acetate VAc is 90-99%;
and adding the polyvinyl acetate-methanol solution from the second polymerization kettle into a first rectifying tower (the temperature is controlled to be 60-68 ℃, the reflux ratio of the rectifying tower is 0.1-1.2), blowing methanol steam from the tower bottom to distill an azeotropic liquid of unreacted vinyl acetate forming methanol, taking out the polyvinyl acetate-methanol solution with the mass concentration of 40-46% from the tower bottom, and sending the obtained polyvinyl acetate-methanol solution with the mass concentration of 40-46% into a scraper film evaporator (the temperature is controlled to be 70-90 ℃, and the evaporation amount is controlled to be 10-25 wt%) to be treated until the mass concentration of polyvinyl acetate PVAc is 48-60 wt%.
Conveying the polyvinyl acetate-methanol solution to a mixer through a conveying pump, centrifugally mixing the polyvinyl acetate-methanol solution with 30g/L NaOH-methanol solution in the mixer (the molar ratio of NaOH to polyvinyl acetate is 0.001:1-0.01:1), uniformly mixing, conveying on a belt of an alcoholysis machine, carrying out alcoholysis reaction at 35-40 ℃ for 25-35 minutes;
polyvinyl alcohol PVA is precipitated and solidified in the conveying process, an elastic and thick plate-shaped object is formed at the outlet of the alcoholysis machine, then the plate-shaped object is crushed into strips by the first crusher, the strips are crushed into particles by the second crusher, the particles are conveyed into a squeezer and then conveyed into a drier to be dried for 3 to 5 hours at the temperature of 90 to 120 ℃, and finally, a qualified polyvinyl alcohol product (the alcoholysis degree is 87.5 to 89.0 mol percent, and the viscosity is 3.5 to 5.0mPa.s) is obtained.
The PVA088-04 product has compact appearance, white color, no powdering and good moldability. Analyzing the vibrating screen material: the ratio of 10-20 mesh retention to 10 mesh retention is 0.6-1.2, the bulk density is 0.4-0.5g/ml (density of water is 1, bulk density is 0.4-0.5), and the whiteness index is 6.6.
The original PVA088-04 product has more dust, the dust at the position of a vibrating screen is large, the rotary valve in the pressure-feed chamber leaks materials, the tail gas pipe of the cyclone separator is damaged, and the dust damaged by the bag collector of the cyclone separator and the like causes white pollution caused by PVA in the pressure-feed chamber and outdoors.
PVA088-04 was produced in the manner of this example, with substantially no dust emission from the vibrating screen, and with substantially no white contamination caused by PVA indoors and outdoors in the pumping chamber.
Comparative example 1
The production of the PVA088-04 product comprises the following specific steps:
after passing through a preheater (55-60 ℃), a vinyl acetate-methanol solution with the mass concentration of 50-53% enters a first polymerization kettle, and solution polymerization is carried out under the action of a bis (2-ethylhexyl) peroxydicarbonate initiator with the mass concentration of 0.01-0.5 wt% (based on the mass percentage of vinyl acetate);
when the polymerization rate reaches 25.0-35.0%, the polymerization liquid is sent into a second polymerization kettle for continuous polymerization, so that the polymerization rate is increased to about 90-99%, and the polymerization reaction of the vinyl acetate is carried out in a methanol solution;
arranging a countercurrent condenser on the polymerization kettle to condense the evaporated vinyl acetate and methanol vapor and return the condensed vapor to the polymerization kettle, and adopting jacket warm water for heat preservation to stabilize the polymerization reaction temperature at 65-67 ℃, wherein the total polymerization time is 4.5-5 hours, and the polymerization rate of vinyl acetate VAc is 90-99%;
adding the polyvinyl acetate-methanol solution from the second polymerization kettle into a first rectifying tower (the temperature is controlled at 60-68 ℃, the reflux ratio of the rectifying tower is 0.1-1.2), blowing methanol steam from the tower bottom to distill an azeotropic liquid of unreacted vinyl acetate forming methanol, and obtaining the polyvinyl acetate-methanol solution with the mass concentration of 40-46% at the tower bottom;
conveying the polyvinyl acetate-methanol solution to a mixer through a conveying pump, centrifugally mixing the polyvinyl acetate-methanol solution with 30g/L NaOH-methanol solution in the mixer (the molar ratio of NaOH to polyvinyl acetate is 0.001:1-0.01:1), uniformly mixing, conveying on a belt of an alcoholysis machine, carrying out alcoholysis reaction at 35-40 ℃ for 25-35 minutes;
polyvinyl alcohol PVA is precipitated and solidified in the conveying process, a plate-shaped object with larger elasticity and thickness is formed at the outlet of the alcoholysis machine, then the plate-shaped object is crushed into strips by a first crusher, the strips are crushed into particles (many are not cut and are adhered) by a second crusher, the particles are sent into a squeezer and then sent into a drier to be dried for 3 to 5 hours at 90 to 120 ℃, and finally, a qualified polyvinyl alcohol product (the alcoholysis degree is 87.5 to 89.0 percent mol, and the viscosity is 3.5 to 5.0mPa.s) is obtained.
The PVA088-04 product has compact appearance, light yellow color and coexisting adhered grains and fine powder. Analyzing the vibrating screen material: the ratio of 10-20 mesh retention to 10 mesh retention was 1.36, the bulk density was 0.58g/ml (density of water was 1, bulk density was 0.4-0.5), and the whiteness index was 16.7.
The PVA088-04 product has much dust, the dust at the site vibrating screen is large, the rotary valve in the pressure conveying chamber leaks materials, and a large amount of PVA dust exists in the pressure conveying chamber and the pressure conveying chamber.
Example 2
The production of the PVA088-03 product comprises the following specific steps:
after passing through a preheater (55-60 ℃), a vinyl acetate methanol solution with the mass concentration of 48-50% enters a first polymerization kettle, and solution polymerization is carried out under the action of a 0.01 wt% -0.5 wt% (based on the mass percentage of vinyl acetate) bis (3,5, 5-trimethylhexanoyl) peroxide initiator;
when the polymerization rate reaches 25.0-35.0%, the polymerization liquid is sent into a second polymerization kettle for continuous polymerization, so that the polymerization rate is increased to about 90-99%, and the polymerization reaction of the vinyl acetate is carried out in a methanol solution;
arranging a countercurrent condenser on the polymerization kettle to make the evaporated vinyl acetate and methanol steam return to the polymerization kettle after condensation, and adopting jacket warm water to keep the temperature of the polymerization reaction stable at 65-67 ℃, wherein the total polymerization time is 4.5-5 hours, and the polymerization rate of vinyl acetate VAC is 90-99%;
adding the polyvinyl acetate-methanol solution from the second polymerization kettle into a first rectifying tower (the temperature is controlled to be 60-68 ℃, the reflux ratio of the rectifying tower is 0.1-1.2), blowing methanol steam from the tower bottom to distill an azeotropic liquid of methanol formed by unreacted vinyl acetate, taking out the polyvinyl acetate-methanol solution with the mass concentration of 38-43% from the tower bottom, and sending the polyvinyl acetate-methanol solution with the mass concentration of 38-43% into a scraper film evaporator (the temperature is controlled to be 70-90 ℃, and the evaporation amount is controlled to be 10-25 wt%) to be treated until the mass concentration of polyvinyl acetate PVAc is 48-60%;
conveying the polyvinyl acetate-methanol solution to a mixer through a conveying pump, centrifugally mixing the polyvinyl acetate-methanol solution with 30g/L NaOH-methanol solution in the mixer (the molar ratio of NaOH to polyvinyl acetate is 0.001:1-0.01:1), uniformly mixing, conveying on a belt of an alcoholysis machine, carrying out alcoholysis reaction at 35-40 ℃ for 25-35 minutes;
PVA is precipitated and solidified in the conveying process, an elastic and thick plate-shaped object is formed at the outlet of the alcoholysis machine, then the plate-shaped object is crushed into strips by a first crusher, the strips are crushed into particles by a second crusher, the particles are conveyed into a squeezer and then conveyed into a dryer to be dried for 3 to 5 hours at the temperature of between 90 and 120 ℃, and finally a qualified polyvinyl alcohol product (the alcoholysis degree is between 87.5 and 89.0 percent mol, and the viscosity is between 3.5 and 5.0mPa.s) is obtained.
The PVA088-03 product has compact appearance, white color, no powdering and good formability. Analyzing the vibrating screen material: the ratio of 10-20 mesh retention to 10 mesh retention is 0.6-1.2, the bulk density is 0.49g/ml (density of water is 1, bulk density is 0.4-0.5), and the whiteness index is 6.9.
The original PVA088-03 product has more dust, the dust at the position of a vibrating screen is large, the rotary valve in the pressure-feed chamber leaks materials, the tail gas pipe of the cyclone separator is damaged, and the dust damaged by the bag collector of the cyclone separator and the like causes the white pollution caused by PVA in the pressure-feed chamber and outdoors.
PVA088-03 was produced in the manner of this example, with substantially no dust emission from the vibrating screen, and with substantially no white contamination caused by PVA both indoors and outdoors in the pumping chamber.
Comparative example 2
The production of the PVA088-03 product comprises the following specific steps:
after passing through a preheater (55-60 ℃), a vinyl acetate methanol solution with the mass concentration of 48-50% enters a first polymerization kettle, and solution polymerization is carried out under the action of a 0.01 wt% -0.5 wt% (based on the mass percentage of vinyl acetate) bis (3,5, 5-trimethylhexanoyl) peroxide initiator;
when the polymerization rate reaches 25.0-35.0%, the polymerization liquid is sent into a second polymerization kettle for continuous polymerization, so that the polymerization rate is increased to about 90-99%, and the polymerization reaction of the vinyl acetate is carried out in a methanol solution;
arranging a countercurrent condenser on the polymerization kettle to make the evaporated vinyl acetate and methanol steam return to the polymerization kettle after condensation, and adopting jacket warm water to keep the temperature of the polymerization reaction stable at 65-67 ℃, wherein the total polymerization time is 4.5-5 hours, and the polymerization rate of vinyl acetate VAC is 90-99%;
adding the polyvinyl acetate-methanol solution from the second polymerization kettle into a first rectifying tower (the temperature is controlled at 60-68 ℃, the reflux ratio of the rectifying tower is 0.1-1.2), blowing methanol steam from the tower bottom to distill an azeotropic liquid of unreacted vinyl acetate forming methanol, and obtaining the polyvinyl acetate-methanol solution with the mass concentration of 38-43% at the tower bottom;
conveying the polyvinyl acetate-methanol solution to a mixer through a conveying pump, centrifugally mixing the polyvinyl acetate-methanol solution with 30g/L NaOH-methanol solution in the mixer (the molar ratio of NaOH to polyvinyl acetate is 0.001:1-0.01:1), uniformly mixing, conveying on a belt of an alcoholysis machine, carrying out alcoholysis reaction at 35-40 ℃ for 25-35 minutes;
PVA is precipitated and solidified during the conveying process, a thick plate-shaped object with larger elasticity is formed at the outlet of the alcoholysis machine, then the plate-shaped object is crushed into strips by a first crusher, the strips are crushed into particles (many are not cut and are adhered) by a second crusher, the particles are sent into a squeezer and then sent into a dryer to be dried for 3 to 5 hours at 90 to 120 ℃, and finally, a qualified polyvinyl alcohol product (the alcoholysis degree is 87.5 to 89.0 percent mol, and the viscosity is 3.5 to 5.0mPa.s) is obtained.
The appearance of the produced PVA088-03 product is a mixture of particles and powder, and the color is yellowish. Analyzing the vibrating screen material: the ratio of 10-20 mesh retention to 10 mesh retention was 0.48, the bulk density was 0.61g/ml, 0.4-0.5g/ml (density of water was 1, bulk density was 0.4-0.5), and the whiteness index was 17.8.
The PVA088-03 product has more dust, the dust raised at the site vibrating screen is large, the rotary valve in the pressure conveying chamber leaks materials, the pressure conveying is difficult, more dust runs out of a bag collector and other positions of a cyclone separator, and more PVA powder exists in the pressure conveying chamber and the pressure conveying chamber.
Example 3
The production of the PVA098-02 product comprises the following specific steps:
after passing through a preheater (55-60 ℃), a vinyl acetate methanol solution with the mass concentration of 40% -45% enters a first polymerization kettle, and solution polymerization is carried out under the action of a 0.01 wt% -0.5 wt% (based on the mass percentage of vinyl acetate) peroxide bis (3,5, 5-trimethylhexanoyl) initiator;
when the polymerization rate reaches 25.0-35.0%, the polymerization liquid is sent into a second polymerization kettle for continuous polymerization, so that the polymerization rate is increased to about 90-99%, and the polymerization reaction of the vinyl acetate is carried out in a methanol solution;
arranging a countercurrent condenser on the polymerization kettle to make the evaporated vinyl acetate and methanol steam return to the polymerization kettle after condensation, and adopting jacket warm water to keep the temperature of the polymerization reaction stable at 65-67 ℃, wherein the total polymerization time is 4.5-5 hours, and the polymerization rate of vinyl acetate VAC is 90-99%;
adding the polyvinyl acetate-methanol solution from the second polymerization kettle into a first rectifying tower (the temperature is controlled at 60-68 ℃, the reflux ratio of the rectifying tower is 0.1-1.2), blowing methanol steam from the tower bottom to distill an azeotropic liquid of methanol formed by unreacted vinyl acetate, taking out the polyvinyl acetate-methanol solution with the mass concentration of 35-40% from the tower bottom, and sending the obtained polyvinyl acetate-methanol solution with the mass concentration of 35-40% into a scraper film evaporator (the temperature is controlled at 70-90 ℃, and the evaporation amount is controlled at 10-25 wt%) to treat the polyvinyl acetate PVAc with the mass concentration of 52-63%.
Conveying the polyvinyl acetate-methanol solution to a mixer through a conveying pump, centrifugally mixing the polyvinyl acetate-methanol solution with 30g/L NaOH-methanol solution in the mixer (the molar ratio of NaOH to polyvinyl acetate is 0.001:1-0.01:1), uniformly mixing, conveying on a belt of an alcoholysis machine, carrying out alcoholysis reaction at 35-40 ℃ for 25-35 minutes;
PVA is precipitated and solidified in the conveying process, an elastic and thick plate-shaped object is formed at the outlet of the alcoholysis machine, then the plate-shaped object is crushed into strips by a first crusher, the strips are crushed into particles by a second crusher, the particles are conveyed into a squeezer and then conveyed into a dryer for drying, and finally a qualified polyvinyl alcohol product (the alcoholysis degree is 98.5-100% mol, and the viscosity is 2.5-3.5mPa.s) is obtained.
The PVA098-02 product has compact appearance, transparency, white color, no powdering and good formability. Analyzing the vibrating screen material: the ratio of 10-20 mesh retention to 10 mesh retention was 1.04, and the bulk density was 0.503g/ml (density of water was 1, bulk density was 0.4-0.5). The whiteness index was 6.2.
The embodiment realizes the industrial production of the ultra-low viscosity 098-02PVA, and solves the problems that the original low viscosity product is produced, the product has more dust, the dust at the vibrating screen is large, the rotary valve in the pressure feed chamber leaks materials, the tail gas pipe of the cyclone separator is damaged, the dust damaged at the cloth bag collector of the cyclone separator and the like causes white pollution caused by the PVA in the pressure feed chamber and outdoors, and the like.
PVA098-02 was produced in the manner of this example, and the vibrating screen was substantially free from dust, and the inside and outside of the pumping chamber were substantially free from white contamination caused by PVA.
Comparative example 3
The production of the PVA098-02 product comprises the following specific steps:
after passing through a preheater (55-60 ℃), a vinyl acetate methanol solution with the mass concentration of 40% -45% enters a first polymerization kettle, and solution polymerization is carried out under the action of a 0.01 wt% -0.5 wt% (based on the mass percentage of vinyl acetate) peroxide bis (3,5, 5-trimethylhexanoyl) initiator;
when the polymerization rate reaches 25.0-35.0%, the polymerization liquid is sent into a second polymerization kettle for continuous polymerization, so that the polymerization rate is increased to about 90-99%, and the polymerization reaction of the vinyl acetate is carried out in a methanol solution;
arranging a countercurrent condenser on the polymerization kettle to make the evaporated vinyl acetate and methanol steam return to the polymerization kettle after condensation, and adopting jacket warm water to keep the temperature of the polymerization reaction stable at 65-67 ℃, wherein the total polymerization time is 4.5-5 hours, and the polymerization rate of vinyl acetate VAC is 90-99%;
adding the polyvinyl acetate-methanol solution from the second polymerization kettle into a first rectifying tower (the temperature is controlled at 60-68 ℃, the reflux ratio of the rectifying tower is 0.1-1.2), blowing methanol steam from the tower bottom to distill the azeotropic liquid of the unreacted vinyl acetate forming methanol, and obtaining the polyvinyl acetate-methanol solution with the mass concentration of 35-40% at the tower bottom;
conveying the polyvinyl acetate-methanol solution to a mixer through a conveying pump, centrifugally mixing the polyvinyl acetate-methanol solution with 30g/L NaOH-methanol solution in the mixer (the molar ratio of NaOH to polyvinyl acetate is 0.001:1-0.01:1), uniformly mixing, conveying on a belt of an alcoholysis machine, carrying out alcoholysis reaction at 35-40 ℃ for 25-35 minutes;
PVA is partially separated out and solidified in the conveying process, but the material is too soft and elastic, and the belt alcoholysis machine cannot convey the PVA. It is impossible to produce.
Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.
Claims (14)
1. Polyvinyl alcohol, characterized in that the ratio of 10-20 mesh retention to 10 mesh retention is 0.6-1.2.
2. The polyvinyl alcohol of claim 1, wherein the bulk density of the polyvinyl alcohol is from 0.4 to 0.5 g/mL.
3. The method for producing polyvinyl alcohol according to claim 1 or 2, wherein vinyl acetate is used as a raw material, methanol is used as a solvent, the method comprises the steps of polymerization, rectification and alcoholysis, the polymerization rate of the vinyl acetate is 90% -99%, and a polyvinyl acetate-methanol solution from the bottom of the rectification tower is placed in a thin film evaporator to be treated until the mass concentration of the polyvinyl acetate is 48% -65%.
4. A production method according to claim 3, wherein the thin film evaporator is a wiped film evaporator.
5. The production method according to claim 3 or 4, wherein the temperature of the thin film evaporator is controlled at 70 to 90 ℃ and the evaporation amount is controlled at 10 to 25% wt.
6. The production method according to any one of claims 3 to 5, wherein the amount of the polymerization initiator is 0.01 to 0.5% by mass based on vinyl acetate.
7. The production method according to claim 6, wherein the initiator is an organic peroxide initiator.
8. The production method according to claim 7, wherein the organic peroxy-based initiator comprises one or more of bis (2-ethylhexyl) peroxydicarbonate, bis (4-tert-butylcyclohexyl) peroxydicarbonate, bis (3,5, 5-trimethylhexanoyl) peroxide, dipropyl peroxydicarbonate, and tert-amyl peroxypivalate.
9. A production process according to any one of claims 6 to 8, wherein the polymerization is carried out at a temperature of 60 to 70 ℃ for 2.5 to 6 hours.
10. The production method according to any one of claims 3 to 9, wherein the rectification is to introduce methanol vapor into a rectification tower to realize separation and purification of polyvinyl acetate, the temperature is controlled to be 60-68 ℃, and the reflux ratio of the rectification tower is 0.1-1.2.
11. The production method of any one of claims 3 to 10, wherein the alcoholysis is carried out by mixing a methanol solution of polyvinyl acetate of the polymerization product with a methanol solution of NaOH of 30g/L, wherein the molar ratio of NaOH to polyvinyl acetate is 0.001:1-0.01:1, the alcoholysis temperature is 30-45 ℃, and the alcoholysis time is 20-40 minutes.
12. The production method according to any one of claims 3 to 11, further comprising preheating at 55 to 60 ℃ before the polymerization.
13. The process according to any one of claims 3 to 12, further comprising the steps of pulverizing, pressing, and drying, wherein the drying temperature is 90 to 120 ℃ and the time is 3 to 5 hours.
14. The production method according to any one of claims 3 to 13, characterized by comprising the steps of:
after passing through a preheater, a vinyl acetate methanol solution with the mass concentration of 30-40% enters a first polymerization kettle, and solution polymerization is carried out under the action of an initiator; when the polymerization rate reaches 25.0% -35.0%, the polymerization liquid is sent into a second polymerization kettle for continuous polymerization, so that the polymerization rate is increased to 90% -99%, and the polymerization reaction of the vinyl acetate is carried out in a methanol solution; arranging a countercurrent condenser on the polymerization kettle to condense the evaporated vinyl acetate and methanol vapor and return the condensed vapor to the polymerization kettle, and adopting jacket warm water for heat preservation to stabilize the polymerization reaction temperature at 60-70 ℃, wherein the total polymerization time is 2.5-6 hours, and the polymerization rate of vinyl acetate is 90-99%;
adding the polyvinyl acetate-methanol solution from the second polymerization kettle into a rectifying tower, blowing methanol steam from the bottom of the tower to distill an azeotropic liquid of unreacted vinyl acetate forming methanol, and taking out the methanol solution of the polyvinyl acetate from the bottom of the tower; the polyvinyl acetate-methanol solution coming out from the tower bottom enters a film evaporator to be processed until the mass concentration of polyvinyl acetate is 48-65%;
conveying the polyvinyl acetate-methanol solution to a mixer through a conveying pump, centrifugally mixing the polyvinyl acetate-methanol solution with 30g/L NaOH-methanol solution in the mixer, uniformly mixing, conveying the mixture on a belt of an alcoholysis machine, conveying the mixture on the belt, wherein the alcoholysis reaction temperature is 35-45 ℃, and the alcoholysis time is 25-40 minutes; and (3) PVA is precipitated and solidified in the conveying process, a plate-shaped object is formed at the outlet of the alcoholysis machine, then the plate-shaped object is crushed into strips by a first crusher, the strips are crushed into particles by a second crusher, the particles are sent to a squeezer, and then the particles are sent to a dryer for drying, so that the catalyst is obtained.
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