CN109721660A - A kind of high temperature acetifies the method that technique prepares acetyl cellulose - Google Patents
A kind of high temperature acetifies the method that technique prepares acetyl cellulose Download PDFInfo
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Abstract
A kind of production method of cellulose acetate, comprising: mix cellulose at room temperature with acetum, pretreatment obtains mixture；Cooling obtains nitration mixture after acetic anhydride is mixed with acetum；The mixture is added in the nitration mixture, acidic catalyst is added to carry out acetifying reaction；The acetic acid flash distillation volatilization so that in reaction system is persistently vacuumized to the reaction system in temperature ramp de, reaches after the temperature of reaction system and stops vacuumizing after peak value acetifies temperature and the reaction was continued until acetify reaction process and terminate, obtain acetifying product；Hot water is added in product in described acetify, be warming up to peak value hydrolysis temperature and maintains a period of time, magnesium acetate is then added, continues to peak value hydrolysis temperature until hydrolysis terminates；Hydrolysate is handled to obtain cellulose acetate product.The present invention not only makes the additive amount of acidic catalyst less, but also cooling without chilled brine after reaction acetifying, and greatly reduces cooling energy consumption and production cost.
Description
Technical field
The invention belongs to acetate fiber production technical fields, are related to a kind of production method of cellulose acetate.
Background technique
Currently, the industrialized preparing process of cellulose acetate mainly uses, low temperature acetifies method and high temperature acetifies method.Due to vinegar
It is larger to change exothermic heat of reaction amount, needs in a short time that quick transport system heat, low temperature process acetify process requirement and mix reactant
Acid is pre-cooled to part of acetic acid and is crystallized, and utilizes its phase transformation absorbing reaction heat.Low temperature process nitration mixture crystallization process needs to consume
A large amount of electric energy, are unfavorable for energy conservation and environmental protection.Low temperature process needs to be added about 13% sulfuric acid catalyst, subsequent that corresponding acetic acid need to be added
Magnesium solution neutralizes, and material consumption is higher.Conventional high-temperature acetify technique (US.Pat.No.4,439,605), (US.Pat.No.2,923,
706), (Canadian.Pat.No.565,099), (US.Pat.No.3,767,642), (US.Pat.No.2,585,516) are urged
Agent consumes about 0.5-1%, but its hydrolytic process needs about 150 DEG C of high temperature and high pressure 4bar, requires all equipment and operation
It is very high.High temperature acetifies technique causes coloured product to turn to be yellow since hydrolysis temperature is very high, subsequent to need just be made with hydrogen peroxide bleaching
Its whiteness meet demand.In comparison, above-mentioned rigors are then not present in the technique of this patent exploitation, can be in lower catalysis
It is preferable to complete to acetify reaction under agent concentration, and product quality is preferable.The advantage of this method: 1. not needing for nitration mixture to be pre-chilled, section
About freezing equipment and a large amount of electric energy.2. catalyst amount is greatly decreased compared to low temperature process, magnesia is also corresponding to be reduced, material consumption drop
It is low.3. not needing to require to reduce to equipment and technological operation using high temperature and high pressure hydrolysis.4. product is not necessarily to hydrogen peroxide bleaching, subtract
Few process reduces harmful influence and uses, reduces risk.
Summary of the invention
The purpose of the present invention is to provide a kind of production method of cellulose acetate, energy consumption in the prior art and material consumption are overcome
Higher disadvantage.
To achieve the above object, the invention adopts the following technical scheme:
A kind of production method of cellulose acetate comprising following steps:
(1), cellulose is mixed at room temperature with acetum, pretreatment obtains mixture；Acetic anhydride is molten with acetic acid
It is cooling after liquid mixing, obtain nitration mixture；
(2), the mixture is added in the nitration mixture, obtains reaction mixture, be then added and account for the reaction mixing
The acidic catalyst of object 1.5-3wt% is to carry out acetifying reaction；
(3), the reaction system is persistently vacuumized so that in reaction system in the temperature ramp de for acetifying reaction
Acetic acid flash distillation volatilization reaches after the temperature of reaction system and stops vacuumizing after peak value acetifies temperature and the reaction was continued that a period of time is straight
Terminate to reaction process is acetified, obtains acetifying product；
(4), hot water is added in product in described acetify, peak value hydrolysis temperature is warming up to certain heating rate and maintains
For a period of time, magnesium acetate is then added, continues to peak value hydrolysis temperature until hydrolysis terminates；
(5), hydrolysate is handled, obtains cellulose acetate product.
Optionally, in step (1), the cellulose is vinegar-grade cellulose, selected from spoelalty pulp grade cellulose or is acetified
Grade wood pulp, derives from timber or cotton linter；And/or
In step (1), 10-20 μm of the average length 0.5-5mm of the cellulose, average diameter；And/or
In step (1), the mass percent of acetic acid is greater than 99% in acetum, i.e., using pure acetic acid；With/
Or,
In step (1), the mass ratio of cellulose and pure acetic acid is 100:(20-60), such as 100:40；And/or
In step (1), in the nitration mixture content of acetic anhydride can be 30-60wt%, for example, 45wt%, nitration mixture and
Cellulose mass ratio is 5:1-8:1.
Optionally, in step (2), the nitration mixture is cooled to -5-15 DEG C before mixing with the mixture；With/
Or,
In step (2), the pH value range of the reaction mixture is -1 to 0；And/or
In step (2), the acidic catalyst is sulfuric acid；Alternatively, the acidic catalyst uses perchloric acid, to toluene
Sulfonic acid, methanesulfonic acid.Optionally, in step (3), the peak value, which acetifies temperature, to be 55-70 DEG C, for example, 57 DEG C；With/
Or,
In step (3), acetifies in reaction process and vacuumize, absolute pressure 3-10kPa；And/or
In step (3), the concentration for collecting acetum obtained from the acetic acid of flash distillation volatilization is 95 ± 2wt%, can be with
It is a kind of mode recycled for continuing to configure mixed acid solution；
Optionally, in step (4), the hot water quality and the product quality ratio that acetifies are 5-10%；And/or
In step (4), the temperature of the hot water is 70-95 DEG C；And/or
In step (4), the heating rate is 1-1.5 DEG C/min；And/or
In step (4), the peak value hydrolysis temperature is 90-100 DEG C；And/or
In step (4), hydrolysis carries out under normal pressure, and the advantage of normal pressure is hydrolysis device normal pressure, manufacture
At low cost, easy to operate, security risk reduces；
In step (4), by the way that acetic acid is recovered under reduced pressure after hydrolysis reaction, the aqueous acetic acid concentration of recycling is
65-75% can be used as the use of subsequent technique precipitating acid, and a kind of mode recycled；
And/or in step (4), the magnesium acetate solution is 2-5%, magnesium acetate solution with the mass ratio for acetifying product
Mass fraction 20-25%.
Optionally, in step (4), it is 40-70min that the time of peak value hydrolysis temperature is maintained before magnesium acetate is added；With/
Or,
In step (4), it is 30-60min that the time of peak value hydrolysis temperature is maintained after magnesium acetate is added.
Optionally, in step (5), excessive deionized water is added in the hydrolysate, takes cellulose acetate heavy
Analysis object is simultaneously washed with deionized to pH value to be neutral, obtains the cellulose acetate product after dry.
Optionally, the filtering blocking value 42 ± 10 of the cellulose acetate product, acetylation number 55.4 ± 0.8%, characteristic
Viscosity 1.45 ± 0.1, whiteness b value 3.0 ± 0.5.
By adopting the above scheme, the beneficial effects of the present invention are:
The first, the additive amount for acetifying the required acidic catalyst (such as sulfuric acid) of reaction of the invention accounts for the amount of reaction mixture
0.5-3wt%, therefore, the additive amount of acidic catalyst is less, and subsequent product does not need to reduce process with hydrogen peroxide bleaching,
Reduce risk of explosion；
The second, peak value hydrolysis temperature of the invention is 90-100 DEG C, and hydrolysis carries out under normal pressure, does not need high pressure water
Solution requires to reduce to equipment and operation；
Acetic acid is recovered under reduced pressure in third, the present invention during high temperature acetifies, and the concentration of obtained acetic acid is about 95wt%；
By the way that acetic acid is recovered under reduced pressure after hydrolytic process, the concentration of obtained acetic acid is about 70wt%, and therefore, the present invention can be realized
Dichlorodiphenyl Acetate recycles.
4th, the present invention can take away the amount of heat that reaction is released, and the vinegar recycled and acetic acid is recovered under reduced pressure
Acid concentration is higher, may be implemented to recycle, it is therefore not necessary to which chilled brine is cooled down, it is higher industrial to avoid price
The use of refrigerator greatly reduces refrigerator power consumption and cost；
5th, method is acetified relative to low temperature, the usage amount of sulfuric acid of the invention and magnesium acetate declines 70-90wt%, greatly
Save cost of material to amplitude.The present invention can reduce sulfuric acid dosage, while product does not need hydrogen peroxide bleaching, coloured product
It is able to satisfy requirement, reduces bleaching process compared to other techniques, the use of explosive substance hydrogen peroxide is avoided, reduces and be produced into
Sheet and security risk.
Specific embodiment
The present invention provides a kind of production methods of cellulose acetate comprising following steps:
(1), cellulose is stirred at room temperature with acetum and mixes 30-40min, pretreatment obtains mixture；By vinegar
Acid anhydrides is cooling after mixing with acetum, obtains nitration mixture；
(2), it adds mixture in nitration mixture, obtains reaction mixture, be then added and account for reaction mixture 0.5-3wt%
Acidic catalyst to carry out acetifying reaction；
(3), acetifying reaction can give off heat, so that the temperature of reaction system be made to gradually rise.In the temperature for acetifying reaction
The reaction system is persistently vacuumized in uphill process so that the acetic acid in reaction system persistently flashes volatilization.Reactant to be acetified
The temperature of system, which reaches after peak value acetifies temperature, to be stopped vacuumizing, and the reaction was continued for a period of time until acetifying reaction process terminates
(such as 10-20min) obtains acetifying product；
(4), hot water is added in acetifying product, peak value hydrolysis temperature is warming up to certain heating rate and maintains one section
Then magnesium acetate is added in time, continue to peak value hydrolysis temperature until hydrolysis terminates；
(5), hydrolysate is handled, obtains cellulose acetate product.
Wherein, in step (1), cellulose is vinegar-grade cellulose, is selected from spoelalty pulp grade cellulose or vinegar-grade wood pulp,
From timber or cotton linter.
In step (1), cellulose will be ground in advance before mixing with acetic acid, so that the average grain diameter of cellulose is
Long 0.5-5mm, 10-20 μm of diameter.
In step (1), the mass percent of acetic acid is greater than 99% in the acetum that is stirred with cellulose, that is, adopts
With pure acetic acid.It is that reinforcing fiber element is acetifying the reaction work in reaction process using the purpose that acetum is stirred mixing
Property.
In step (1), the mass ratio of cellulose and acetic acid can be 100:(20-60), for example, 100:40.Acetic acid is molten
Liquid plays the role of activation, dissolution.
In step (1), the content of acetic anhydride can be 30-60wt%, preferably 45wt%, nitration mixture and fiber in nitration mixture
Plain mass ratio is 5:1-8:1.
In step (2), nitration mixture is cooled to -5-15 DEG C before mixing with mixture.
In step (2), acidic catalyst is sulfuric acid.
In step (3), by the control for reactive material and reaction condition, peak value can be made to acetify temperature in 55-70
Between DEG C, preferably 57-67 DEG C.
In step (3), acetifies in reaction process and vacuumize, absolute pressure 3-10kPa.By vacuumizing, can make to react
Acetic acid in system persistently flashes volatilization, then collects the acetic acid of volatilization, to realize recycling for Dichlorodiphenyl Acetate.
In step (3), the concentration of obtained acetum is 95 ± 2wt% after the acetic acid of collection flash distillation volatilization.It should
Acetum can be with reuse to step (2).
In step (4), the purpose that hot water is added is to enable this to acetify product hydrolysis occurs.
In step (4), the temperature of hot water is 70-95 DEG C, preferably 85-95 DEG C.In step (3), the flash distillation of acetic acid
Volatilization can take away the amount of heat for acetifying and releasing in reaction process, therefore, acetify after reaction without being cooled down, such as nothing
Chilled brine need to be used to be cooled down, this will be greatly reduced the power consumption of refrigerator.The obtained product that acetifies is not necessarily to cooling i.e.
It can directly be mixed with hot water.
In step (4), heating rate is 1-1.5 DEG C/min.After acetifying product and mixing with hot water and reach 50 ± 3 DEG C
Afterwards, it needs slowly to heat up to the mixed system.For example, peak value hydrolysis temperature can be raised the temperature in 40min.
In step (4), peak value hydrolysis temperature is 90-100 DEG C, preferably 95-100 DEG C.Peak value hydrolysis temperature is that most have
The temperature carried out conducive to hydrolysis.
In step (4), hydrolysis carries out under normal pressure, hydrolysis of the invention can under normal or reduced pressure into
Row, does not need highly pressured hydrolysis, therefore, the requirement to the operation of equipment is lower, is advantageously implemented safer production.
In step (4), by the way that acetic acid is recovered under reduced pressure in hydrolysis reaction, the concentration of obtained acetic acid is about
65-75%.
In step (4), the magnesium acetate solution and the mass ratio for acetifying product are 2-5%, and magnesium acetate refers to acetic acid
Magnesium solution.
In step (4), it can be 40-70min that the time of peak value hydrolysis temperature is maintained before magnesium acetate is added.
In step (4), it is 30-40min that the time of peak value hydrolysis temperature is maintained after magnesium acetate is added.Acetic acid is being added
The time of peak value hydrolysis temperature is maintained before maintaining the time of peak value hydrolysis temperature to be less than or equal to addition magnesium acetate after magnesium.
In step (5), the process handled hydrolysate includes: that excessive deionization is added in hydrolysate
Water is so that precipitating occurs for cellulose acetate, and taking cellulose acetate precipitating object and being washed with deionized to pH value is neutrality, in 120
Cellulose acetate product is obtained after DEG C dry 8h.
In step (5), the filtering blocking value 42 ± 10 of cellulose acetate product, acetylation number 55.4 ± 0.8%, characteristic
Viscosity 1.45 ± 0.1.
It wherein filters blocking value test method: vinegar sheet being dissolved in acetone and is configured to 9.5% strength solution, then existed with filter paper
Slurries are filtered under 1.5 atmospheric pressure, are obtained according to filtration yield.
Acetylation number %=6000* degree of substitution/(162+42* degree of substitution), degree of substitution is obtained according to acid-base titration.
Inherent viscosity: vinegar sheet is dissolved in acetone and is configured to 0.25% strength solution using Ubbelohde viscometer test acquisition.
Whiteness: color b value is tested with light splitting chromascope.
The present invention is further illustrated with reference to embodiments.
Embodiment 1
A kind of production method of cellulose acetate comprising following steps:
(1), the pure acetic acid by 10kg vinegar-grade cellulose with 4kg concentration greater than 99% mixes 30min at room temperature, to increase
Its strong reactivity, and obtain mixture；Acetic anhydride is greater than cooling after 99% pure acetic acid mixes with concentration, obtains nitration mixture,
The content of middle acetic anhydride is 41wt%；The average length 0.5-5mm of the vinegar-grade cellulose, 10-20 μm of average diameter；
(2), it after nitration mixture 56kg being cooled to 5 DEG C, feeds the mixture into nitration mixture after cooling, obtains reaction mixture,
Then acidic catalyst (sulfuric acid) 0.3kg for accounting for cellulose quality 3% is added acetify reaction, pH is added after sulfuric acid
It surveys, pH=-0.58；
(3), meeting heat release in reaction process is acetified, so that the temperature for acetifying reaction system gradually rises, and in 30min
It inside rises to peak value and acetifies temperature (57 DEG C).The reaction system is persistently vacuumized in temperature ramp de, absolute pressure 4.7kPa,
So that acetic acid in reaction system flashes volatilization, after the temperature of reaction system reach peak value acetify temperature (57 DEG C) afterwards stop taking out it is true
Empty and the reaction was continued 10min is until acetifying reaction process terminates, to obtain acetifying product；Flash distillation volatilization is collected in the process
Acetic acid 2.1kg, the concentration of obtained acetum are 95wt%；
(4), it is added hot water 4kg in acetifying product, hot water and to acetify product quality ratio be 5.7%, about since 50 DEG C
Heating, 40min are warming up to peak value hydrolysis temperature (95 DEG C) and maintain 50min, and magnesium acetate 1.6kg, magnesium acetate solution is then added
It is 2.3% with product quality ratio is acetified, continues to peak value hydrolysis temperature (95 DEG C) 40min until hydrolysis terminates；Hydrolysis
Aqueous acetic acid 2.4kg is recovered under reduced pressure after reaction, the pressure of decompression is absolute pressure 14kPa；
(5), hydrolysate is handled, the method for processing are as follows: be added in hydrolysate excessive deionized water with
It separates out vinegar sheet to come, obtains cellulose acetate precipitating object；It takes cellulose acetate precipitating object and is washed with deionized to pH value
For neutrality, cellulose acetate product is obtained after 120 DEG C of dry 8h；
After testing it is found that the filtering blocking value 42 of the cellulose acetate product of the present embodiment, acetylation number 55.4% are special
Property viscosity 1.42, whiteness 3.1.
Embodiment 2
(1) the pure acetic acid 8kg that concentration is greater than 99%, room are added into the vinegar-grade wood pulp cellulose 20kg after smashing and grinding
The lower stirring pretreatment 30min of temperature, enhances its reactivity；
(2) the mixture 113kg (nitration mixture) of acetic anhydride and acetic acid is cooled to 4.5 DEG C in the reaction vessel, wherein acetic anhydride
Accounting for mass ratio is 45%；
(3) wood pulp that pretreatment is completed is added in the nitration mixture after cooling, is then initially added into catalyst sulfuric acid
0.6kg, the dosage of sulfuric acid are the 3% of cellulose quality, and system pH is -0.32 at this time, and reaction starts.Reaction starts rear system and puts
Thermal conductivity causes system temperature to rise to 57 DEG C in 30min, and vacuum pump is opened while temperature rises and is vacuumized, absolute pressure
5.5kPa, acetic acid flash distillation volatilization in reaction system.After temperature reaches 57 DEG C, stop vacuum pump, acetifies reaction after the reaction was continued 13min
Terminate, collect the acetic acid 4.8kg of flash distillation volatilization in the process, the concentration of obtained acetum is 95.8wt%；
(4) to addition hot water 7.6kg in product is acetified, hot water, which accounts for, acetifies product quality than 5.2%, adds since about 50 DEG C
Heat, is heated to 95 DEG C in about 40min, maintains 95 DEG C about 50 minutes, is then added magnesium acetate solution 4kg, magnesium acetate solution and
Acetifying product quality ratio is 2.8%, continue to 95 DEG C about 40 minutes then reaction terminate.Hydrolysis is recycled with vacuum pump pressure to produce
Acetic acid in object, absolute pressure 12kPa take out 14min, recovery of acetic acid aqueous solution about 5.6kg, acetum concentration 66%；It is reacted after exhausting
Product is added a large amount of deionized water product vinegar sheets and starts to separate out, and vinegar sheet particle continues to be washed with deionized water, detects washing water
Until neutrality；By 120 DEG C of product vinegar sheet dry 8h, detection；
(5) products therefrom filters blocking value 40.8, acetylation number 55.0%, inherent viscosity 1.40, whiteness 2.7.
Embodiment 3
(1) the pure acetic acid 10kg that concentration is greater than 99%, room temperature are added into the vinegar-grade cellulose 20kg after smashing and grinding
Lower stirring pre-processes 40min, enhances its reactivity；
(2) the mixture 120kg (nitration mixture) of acetic anhydride and acetic acid is cooled to 7 DEG C in the reaction vessel, and wherein acetic anhydride accounts for
Than 40%；
(3) wood pulp that pretreatment is completed is added in nitration mixture after cooling, is then initially added into catalyst sulfuric acid 0.4kg,
The dosage of sulfuric acid is the 2% of cellulose quality, and system pH is -0.14 at this time, and reaction starts.Reaction, which starts rear system heat release, to be caused
System temperature rises to 55 DEG C in 36min, and vacuum pump is opened while temperature rises and vacuumizes absolute pressure 6.7kPa, reactant
Acetic acid flash distillation volatilization in being.After temperature reaches 55 DEG C, stop vacuum pump, acetifying reaction after the reaction was continued 15min terminates, in this process
The middle acetic acid 5.3kg for collecting flash distillation volatilization, the concentration of obtained acetum are 97.8wt%；
(4) to addition hot water 8.9kg in product is acetified, hot water, which accounts for, acetifies product quality than 5.9%, adds since about 52 DEG C
Heat is heated to 99 DEG C in about 44min, maintains 99 DEG C about 47 minutes, and magnesium acetate solution 3.5kg, magnesium acetate solution is then added
2.3% with product quality ratio is acetified, continue to 99 DEG C about 36 minutes then reaction terminate.It is recycled and is hydrolyzed with vacuum pump pressure
Acetic acid in product, absolute pressure 10kPa take out 15min, recovery of acetic acid aqueous solution about 6.8kg, acetum concentration 67%.Reaction product
A large amount of deionized water product vinegar sheets are added to start to separate out, vinegar sheet particle continues to be washed with deionized water, detects washing water into
Until property；By 120 DEG C of product vinegar sheet dry 8h, detection；
(5) products therefrom filters blocking value 39, acetylation number 55.8%, inherent viscosity 1.46, whiteness 2.5.
Embodiment 4
(1) the pure acetic acid 9kg that concentration is greater than 99% is added into vinegar-grade cellulose 20kg after smashing and grinding, stirs at room temperature
Pretreatment 60min is mixed, its reactivity is enhanced；
(2) the mixture 118kg (nitration mixture) of acetic anhydride and acetic acid is cooled to 12 DEG C in the reaction vessel, and wherein acetic anhydride accounts for
Than 47%；
(3) wood pulp that pretreatment is completed is added in nitration mixture after cooling, is then initially added into catalyst sulfuric acid 0.3kg,
The dosage of sulfuric acid is the 1.5% of cellulose quality, and system pH is -0.06 at this time, and reaction starts.Reaction starts rear system heat release and leads
It causes system temperature to rise to 58 DEG C in 40min, vacuum pump is opened while temperature rises and vacuumizes absolute pressure 7.4kPa, is reacted
Acetic acid flash distillation volatilization in system.After temperature reaches 58 DEG C, stop vacuum pump, acetifying reaction after the reaction was continued 10min terminates, herein mistake
The acetic acid 6.5kg of flash distillation volatilization is collected in journey, the concentration of obtained acetum is 96.2wt%；
(4) to addition hot water 9.1kg in product is acetified, hot water, which accounts for, acetifies product quality than 6.2%, adds since about 53 DEG C
Heat, is heated to 91 DEG C in about 38min, maintains 91 DEG C of about 52min, is then added magnesium acetate solution 3.1kg, magnesium acetate solution and
Acetifying product quality ratio is 2.1%, continue to 91 DEG C about 44 minutes then reaction terminate.Hydrolysis is recycled with vacuum pump pressure to produce
Acetic acid in object, absolute pressure 15kPa take out 11min, recovery of acetic acid aqueous solution about 7.0kg, acetum concentration 72%.Reaction product adds
Enter a large amount of deionized water product vinegar sheets to start to separate out, vinegar sheet particle continues to be washed with deionized water, detection washing water to neutrality
Until；By 120 DEG C of product vinegar sheet dry 8h, detection；
(5) products therefrom filters blocking value 45, acetylation number 55.3%, inherent viscosity 1.44, whiteness 3.2.
Comparison example:
(1) the pure acetic acid 8kg that concentration is greater than 99% is added into vinegar-grade cellulose 20kg after smashing and grinding, stirs at room temperature
Pretreatment 40min is mixed, its reactivity is enhanced；
(2) the mixture 110kg (nitration mixture) of acetic anhydride and acetic acid is cooled to -18 DEG C in the reaction vessel, wherein acetic anhydride
Accounting 45%；
(3) wood pulp that pretreatment is completed is added in nitration mixture after cooling, is then initially added into catalyst sulfuric acid 2.6kg,
The dosage of sulfuric acid is the 1.5% of cellulose quality, and system pH is -0.62 at this time, and reaction starts.Reaction starts rear system heat release and leads
It causes system temperature to rise to 47 DEG C in 28min, needs to enable acetylator jacket refrigerating medium while temperature rises
Circulation is to take away the heat that reaction is released.It reaches and acetifies reaction after the reaction was continued 20min after peak temperature and terminate.
(4) to addition hot water 9.1kg in product is acetified, hot water, which accounts for, acetifies product quality than 4.6%, adds since about 40 DEG C
Heat is heated to 82 DEG C in about 48min, maintains 82 DEG C of about 100min, and magnesium acetate solution 9.0kg, magnesium acetate solution is then added
It is 6.0% with product quality ratio is acetified, stirring 5min reaction terminates.Reaction product is added a large amount of deionized water product vinegar sheets and starts
It separates out, vinegar sheet particle continues to be washed with deionized water, until detecting washing water to neutrality；By 120 DEG C of product vinegar sheet dry 8h,
Detection；
(5) products therefrom filters blocking value 35, acetylation number 55.7%, inherent viscosity 1.50, whiteness 3.9.
It being needed by comparative example discovery by nitration mixture and is cooled to -18 DEG C, vinegar sheet whiteness is lower, need to consume a large amount of electric energy,
Energy consumption is higher；The equal quality wood pulp catalyst concentrated sulfuric acid and magnesium acetate consumption are significantly increased, and consume larger.
The production method of cellulose acetate provided by the present invention uses high temperature to acetify and be recovered under reduced pressure acetic acid method,
Not only make the additive amount of acidic catalyst less, but also cooling without chilled brine after reaction acetifying, greatly
Reduce cooling energy consumption；Using 3% sulfuric acid catalyst, subsequent product is needed with hydrogen peroxide bleaching, reduction process, reduction explosion wind
Danger；Hydrolysis temperature is 95 degree, does not need highly pressured hydrolysis, requires to reduce to equipment and operation.
This hair can be understood and applied the above description of the embodiments is intended to facilitate those skilled in the art
It is bright；Person skilled in the art obviously easily can make various modifications to these embodiments, and described herein
General Principle is applied in other embodiments without having to go through creative labor；Therefore, the present invention is not limited to implementations here
Example, those skilled in the art's announcement according to the present invention, improvement and modification made without departing from the scope of the present invention all should be
Within protection scope of the present invention.
Claims (14)
1. a kind of production method of cellulose acetate, which is characterized in that it includes the following steps:
(1), cellulose is mixed at room temperature with acetum, pretreatment obtains mixture；Acetic anhydride and acetum are mixed
It is cooling after conjunction, obtain nitration mixture；
(2), the mixture is added in the nitration mixture, obtains reaction mixture, acidic catalyst is added then to carry out vinegar
Change reaction；
(3), the acetic acid so that in reaction system is persistently vacuumized to the reaction system in the temperature ramp de for acetifying reaction
Flash distillation volatilization reaches after the temperature of reaction system and stops vacuumizing after peak value acetifies temperature and the reaction was continued until acetifying and reacting
Journey terminates, and obtains acetifying product；
(4), hot water is added in product in described acetify, is warming up to peak value hydrolysis temperature and maintains, magnesium acetate is then added, continue
Peak value hydrolysis temperature is maintained until hydrolysis terminates；
(5), hydrolysate is handled, obtains cellulose acetate product.
2. production method according to claim 1, it is characterised in that: in step (1), the cellulose is that vinegar-grade is fine
Dimension element；And/or
In step (1), 10-20 μm of the average length 0.5-5mm of the cellulose, average diameter；And/or
In step (1), the mass percent of acetic acid is greater than 99% in acetum；And/or
In step (1), the mass ratio of cellulose and acetic acid is 100:(20-60)；And/or
In step (1), the content of acetic anhydride is 30-60wt% in the nitration mixture, and nitration mixture and fiber quality ratio are 5:1-8:1.
3. production method according to claim 2, it is characterised in that: in step (1), the cellulose is selected from spoelalty pulp
Grade cellulose or vinegar-grade wood pulp；And/or
In step (1), the mass ratio of the cellulose and acetic acid is 100:(20-60)；And/or
The content of acetic anhydride is 30-60wt% in the nitration mixture.
4. production method according to claim 1, it is characterised in that: in step (2), the dosage of the acidic catalyst
For the 0.5-3wt% of cellulose quality；And/or
In step (2), the nitration mixture is cooled to -5-15 DEG C before mixing with the mixture；And/or
In step (2), the pH value of the nitration mixture and catalyst mixture is between -1 to 0；And/or
In step (2), the acidic catalyst is the concentrated sulfuric acid.
5. production method according to claim 1, it is characterised in that: in step (3), the peak value acetifies temperature and is
55-70℃；And/or
In step (3), acetifies and vacuumize absolute pressure in reaction process, vacuum degree 3-10kPa；And/or
In step (3), the acetic acid of flash distillation volatilization is collected, the concentration of obtained acetum is 95 ± 2wt%；And/or
In step (3), by the acetic acid reuse of the flash distillation volatilization of collection into step (2).
6. production method according to claim 5, it is characterised in that: in step (3), the peak value acetifies temperature and is
55-70℃。
7. production method according to claim 1, it is characterised in that: in step (4), the hot water quality and the vinegar
Change product quality ratio is 5-10%；And/or
In step (4), the temperature of the hot water is 70-95 DEG C；And/or
In step (4), the heating rate is 1-1.5 DEG C/min；And/or
In step (4), the peak value hydrolysis temperature is 90-100 DEG C；And/or
In step (4), hydrolysis carries out under normal pressure；And/or
In step (4), by the way that acetic acid is recovered under reduced pressure after hydrolysis reaction, the aqueous acetic acid concentration of recycling is 65-
75%；And/or
In step (4), the magnesium acetate is 2-5% with the mass ratio for acetifying product.
8. production method according to claim 1, it is characterised in that:
In step (4), tieed up before maintaining the time of peak value hydrolysis temperature to be less than or equal to addition magnesium acetate after magnesium acetate is added
Hold the time of peak value hydrolysis temperature.
9. production method according to claim 8, it is characterised in that: in step (4), maintain peak before magnesium acetate is added
The time for being worth hydrolysis temperature is 40-70min；And/or
In step (4), it is 30-60min that the time of peak value hydrolysis temperature is maintained after magnesium acetate is added.
10. production method according to claim 7, it is characterised in that:
In step (4), after acetifying product and being mixed with hot water and after reaching 50 ± 5 DEG C, which is slowly risen
Temperature.
11. production method according to claim 10, it is characterised in that:
In step (4), peak value hydrolysis temperature is raised the temperature in 30-50min.
12. production method according to claim 7, it is characterised in that: in step (4), the temperature of hot water is 70-95
℃；And/or
In step (4), peak value hydrolysis temperature is 90-100 DEG C.
13. production method according to claim 1, it is characterised in that: in step (5), add in the hydrolysate
Enter excessive deionized water, taking cellulose acetate precipitating object and being washed with deionized to pH value is neutrality, obtains institute after dry
State cellulose acetate product.
14. production method according to claim 1, it is characterised in that: the filtering blocking value of the cellulose acetate product
42 ± 10, acetylation number 55.4 ± 0.8%, inherent viscosity 1.45 ± 0.1, whiteness b value 3.0 ± 0.5.
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