CN109061042A - A kind of method of unstable hydroxy radical content in measurement polyformaldehyde - Google Patents
A kind of method of unstable hydroxy radical content in measurement polyformaldehyde Download PDFInfo
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Abstract
The invention discloses it is a kind of measurement polyformaldehyde in unstable hydroxy radical content method, include the following steps, 1) take quality be m the polyformaldehyde sample after being dried, into polyformaldehyde sample be added ammonia spirit reacted, obtain reaction solution；2) sodium sulfite aqueous solution is added into reaction solution, obtains prepare liquid；3) prepare liquid is titrated with the acid standard solution that concentration is C, and records the volume V of acid standard solution used in titration process；If acid standard solution used is unitary acidity standard solution, unstable hydroxy radical content in polyformaldehyde sample is obtained according to such as following formula (I)；If acid standard solution used is binary acidic standard solution, unstable hydroxy radical content in polyformaldehyde sample is obtained according to such as following formula (II).The present invention provides the judgement of the superiority and inferiority of a kind of pair of polyformaldehyde polymerization technique, regulation operating condition, coordination production and finished product control have the measuring method of the unstable hydroxy radical content of directive significance.
Description
Technical field
The present invention relates to a kind of measurement method of unstable hydroxy radical content, more particularly to a kind of polyformaldehyde slurry sample and
The measuring method of hydroxy radical content in powder sample.
Background technique
The unstable hydroxyl of its slurry and powder is the unstable base of copolymerized methanal molecular chain-end in process of producing polyformaldehyde
Group, content number indicate polymerization reaction degree during synthesizing polyoxymethylene strand.Hydroxy radical content is lower, shows to gather
Close reaction more sufficiently, completely, long-chain molecule is more, and subsequent finished product stability is stronger, better quality；Conversely, then showing to need to adjust
So that material polymerize completely, reduction small-molecule substance increases strand, makes finished pellets performance indexes polymerization process condition
It is up to standard, provide quality goods or brilliant.
Therefore, how in the short time content of unstable hydroxyl in process of producing polyformaldehyde is determined, to judge that technique is poly-
The superiority and inferiority of reaction is closed, regulation operating condition, coordination production and finished product control seem especially urgent.
Summary of the invention
The present invention provides unstable hydroxy radical contents in a kind of measurement polyformaldehyde slurry sample and polyformaldehyde powder sample
Method.
In order to achieve the object of the present invention, present invention employs the following technical solutions:
A kind of method of unstable hydroxy radical content in measurement polyformaldehyde, comprising the following steps:
1) taking quality is the polyformaldehyde sample after being dried of m, and ammonia spirit is added into the polyformaldehyde sample
It is reacted, obtains reaction solution；The drying process be by the polyformaldehyde sample less than 100 DEG C at a temperature of it is dry to perseverance
Weight；Preferably, temperature is 50-80 DEG C；
2) sodium sulfite aqueous solution is added into the reaction solution, obtains prepare liquid；
3) prepare liquid is titrated with the acid standard solution that concentration is C, and records acid standard used in titration process
The volume V of solution；
If acid standard solution used is unitary acidity standard solution, the polyformaldehyde sample is obtained according to such as following formula (I)
Unstable hydroxy radical content in product:
X=3*C*V*M/ (5*1000*m) * 100% (I)
If acid standard solution used is binary acidic standard solution, the polyformaldehyde sample is obtained according to such as following formula (II)
Unstable hydroxy radical content in product:
X=6*C*V*M/ (5*1000*m) * 100% (II)
C: acid concentration of standard solution, mol/L；
V: the volume of the acid standard solution of consumption, ml are titrated；
M: the molal weight of formaldehyde, g/mol；
M: the quality of polyformaldehyde sample, g.
Method provided by the invention is specifically related to following reaction mechanism during the reaction:
(1) unstable hydroxyl present in polyformaldehyde and ammonium hydroxide react
6HCHO+4NH3·H2O=(CH2)6N4+10H2O
(2) formaldehyde and sodium sulfite react:
HCHO+Na2SO3+H2O=NaOH+CH2(NaSO3)OH
(3) six methylamines of intermediate product react (by taking hydrochloric acid as an example) with sour:
(CH2)6N4+6H2O+4HCL=6HCHO+4NH4CL
(4) sodium hydroxide and hydrochloric acid react:
NaOH+HCL=NaCL+H2O
Contain hemiacetal structure in the end group of polyformaldehyde, contains unstable hydroxyl in hemiacetal structure, in the condition of heating
Down can the gradually depolymerization from the hemiacetal of its end group, can take off releasing formaldehyde from molecular chain-end, and the formaldehyde that do not take off
Amount is the content of hydroxyl unstable on original polyformaldehyde end group.Therefore, after ammonia spirit being added into polyformaldehyde, Ke Yifa
Raw above-mentioned reaction.The present invention titrates to obtain the sodium hydroxide of reaction generation in the way of acid base titration by acidity standard solution
Amount, then again by reaction present in quantitative relation obtain it is unstable in polyformaldehyde slurry sample or polyformaldehyde powder sample
The content of hydroxyl.
By above-mentioned reaction mechanism it is found that according to acid standard solution be unitary acidity standard solution, for example, hydrochloric acid or
Nitric acid, then the molar ratio of unitary acidity standard solution and unstable hydroxyl in polyformaldehyde is 5:3, i.e., unstable hydroxyl in polyformaldehyde
The content of base be consumption acid standard solution 3/5, under similarly；According to acid standard solution be binary acidic standard it is molten
Liquid, for example, carbonic acid or sulfuric acid, then the molar ratio of binary acidic standard solution and unstable hydroxyl in polyformaldehyde is 5:6；So
Afterwards, the content of unstable hydroxyl in polyformaldehyde is calculated by the meter of acid standard solution used.
Polyformaldehyde sample can be dried before the assay, so that a part is attached to wet poly- first in process of production
Can be removed from preceding workshop section's bring free formaldehyde by controlling in 100 DEG C or less heat drying polyformaldehyde samples on aldehyde material
Free formaldehyde, avoid interference measurement unstable hydroxyl production formaldehyde as a result, and drying control temperature at 100 DEG C hereinafter, can be
Remove free formaldehyde while guarantee do not occur sample measurement reaction before because drying temperature height due to shift to an earlier date from unstable hydroxyl take off
Formaldehyde out ensure that the accuracy of measurement result, exclude error and interference；Above-mentioned drying temperature is preferably 50-80 DEG C, such as
60 DEG C, 75 DEG C；In drying process process, dry constant weight is that the weight of polyformaldehyde sample at least no longer changes in 3min.
Preferably, the unitary acidity standard solution is hydrochloric acid standard solution or nitric acid standard solution, the binary acid
Property standard solution be sulfuric acid standard solution.
Preferably, the concentration of the unitary acidity standard solution and the binary acidic standard solution is 1mol/L, will be upper
The concentration for stating standard solution is set as 1mol/L, convenient for faster and more accurately calculating target value.
Preferably, the polyformaldehyde sample is polyformaldehyde slurry sample or polyformaldehyde powder sample, the polyformaldehyde slurry
Material sample is specially the copolymerized methanal initial product generated after metaformaldehyde is copolymerized with dioxolane；Wherein, containing by copolymerization first
The small sheet and the block-like solid of powder that aldehyde is formed, a small amount of formaldehyde in water and water, the partial size of the polyformaldehyde powder sample
Less than 0.5mm, preferably 0.1-0.4mm, such as 0.2mm, 0.3mm.
Preferably, the reaction temperature in step 1) is 120-200 DEG C, reaction time 30-60min；Reaction temperature is into one
Preferably 150-180 DEG C of step, for example, 160 DEG C, 170 DEG C；Reaction time is more preferably 40-50min；For example, 42min,
44min.Above-mentioned reaction preferably carries out in closed system, simultaneously as ammonium hydroxide has the chemical property for being highly soluble in water, because
This, does not consider the volatilization loss of ammonium hydroxide under high temperature.
Preferably, the ammonia spirit in step 1) is ammonium hydroxide methanol solution, and the mass concentration of the ammonium hydroxide methanol solution is
0.2%-1%, preferably 0.4%-0.8%, for example, 0.5%；Wherein, the mass concentration of ammonia spirit is 20%-30%, excellent
It is selected as 25-28%, generally prepares ammonium hydroxide methanol solution, solubility using commercially available ammonia spirit in continuous mode of the present invention
Generally 28%；Methanol solution is using pure methanol solution, mass concentration 100%.Measurement side provided by the present invention
Method is acted on by hydroxyl unstable in ammonium hydroxide and sample first, and the dosage of sample is few, required ammonium hydroxide methanol solution amount
Seldom, and not influence subsequent acid base titration as a result, should not be excessive using the unsuitable overrich of concentration of ammonia spirit, dosage, as long as
It can guarantee to react completely with hydroxyl unstable in polyformaldehyde sample.The first of ammonium hydroxide has been used in method provided by the invention
Alcoholic solution, it is therefore prevented that formaldehyde present in reaction system polymerize, and influences testing result.
Preferably, the concentration of step 2) sulfite sodium water solution is 1mol/L.
Preferably, the prepare liquid is titrated using automatical potentiometric titrimeter in step 3).Method of the invention using
Potentiometric titration determines the instrument of titration end-point by measuring potential change in titration process, instrument can set pre- titration,
The functions such as default endpoint titration, blank titration or manual titration can voluntarily generate dedicated titration mode, and measurement result is more acurrate, more
It is easy to control.The automatical potentiometric titrimeter used in step 3) of the present invention can have above-mentioned function selected from any on the market
Potentiometric titrimeter, for example, the combination electrode automatical potentiometric titrimeters of logical 848 production of Switzerland ten thousand.
Using above-mentioned technical solution, have the following technical effect that:
The present invention using the method for acid base titration to being detected in polyformaldehyde slurry sample or powder sample, can be quick
The content for determining unstable hydroxyl present in product, further improves working efficiency, is the excellent of polyformaldehyde polymerization technique
Bad judgement, regulation operating condition, coordination production and finished product control have directive significance.
The present invention carries out titration detection hydroxy radical content using acid standard solution, and method is simple and easy to get, and accuracy is high, measurement
Cost is relatively low；Meanwhile reagent solution needed for preparing reaction can be used as needed, chemical physical property is steady within effective time
It is fixed, it is unlikely to deteriorate.
Specific embodiment
In order to better understand the present invention, below with reference to the embodiment content that the present invention is furture elucidated.
One, following each example Instrumental equipment and raw material sources information:
Electronic balance: plum Teller-support benefit, precision 0.0001g；
Automatical potentiometric titrimeter: Switzerland ten thousand logical 848, combination electrode；
High-pressure heater: U.S. PARR4848
Electric heating convection oven: room temperature -- 250 DEG C
Polyformaldehyde slurry sample: Ningxia Coal Industry Group coal chemical industry branch company of Shenhua；
Polyformaldehyde powder sample: Ningxia Coal Industry Group coal chemical industry branch company of Shenhua；
Chemical reagent used in other in various embodiments of the present invention is this field conventional reagent, and pureness specifications used are equal
It is pure to analyze.
Two, solution used in following each examples is formulated as follows
1,1mol/L sodium sulfite solution
Accurately weigh sodium sulfite 126.04g be added 500ml distilled water dissolve and stir it is completely limpid to solution, shift simultaneously
It is settled in 1000ml volumetric flask；It is spare.
2,0.5% ammonium hydroxide methanol solution:
It takes 2780ml methanol to be added in 5000ml beaker, then 47ml, the addition of commercially available 28.0% ammonium hydroxide is taken to have been charged into methanol
5000ml beaker in, stirring and dissolving is simultaneously transferred in 5000ml volumetric flask after being cooled to room temperature, and is settled to distilled water
5000ml graduation mark, it is spare；The ammonium hydroxide methanol of other concentration can be made according to the method described above.
3,1mol/L hydrochloric acid standard solution:
1000ml measuring bottle is taken, takes 86 ± 5ml concentration 35-37% concentrated hydrochloric acid that measuring bottle is added after 500 ± 10ml distilled water is added
In, it is diluted with water groove, and stir about 30 minutes；It is spare.
4, sulfuric acid standard solution:
1000ml measuring bottle is taken, takes 98% concentrated hydrochloric acid of 54.3ml concentration to be added in measuring bottle after 500 ± 10ml distilled water is added, adds
Water is diluted to groove, and stir about 30 minutes；It is spare.
5, nitric acid standard solution:
1000ml measuring bottle is taken, takes 65% concentrated hydrochloric acid of 69.7ml concentration to be added in measuring bottle after 500 ± 10ml distilled water is added, adds
Water is diluted to groove, and stir about 30 minutes；It is spare.
Polyformaldehyde sample one is the Ningxia Coal Industry Group coal chemical industry branch company of Shenhua of same batch, undried processing
The polyformaldehyde slurry sample of production；Polyformaldehyde sample two is the Shenhua Ningxia Coal Industry Group coal of same batch, undried processing
The polyformaldehyde powder sample of chemical industry branch company production.
Embodiment 1
1) polyformaldehyde sample one is dried at 55 DEG C to constant weight, it is 18 minutes time-consuming；It is poly- after accurately weighing 1.02g drying
Formaldehyde sample one places it in reaction vessel while being added the ammonium hydroxide methanol solution 100ml that total mass concentration is 0.5%, adds
Heat obtained reaction solution to constant temperature 45 minutes after 180 DEG C；
2) reaction solution is cooled to room temperature and is transferred in titration cup, the sodium sulfite solution of 20ml is added, stir 3 points
Clock obtains prepare liquid；
3) constant-current titration is carried out with the standard hydrochloric acid solution that concentration is 1mol/L, the results show that standard hydrochloric acid solution used
Volume be 1.11ml.
Above-mentioned data are substituted into formula I, X=3*C*V*M/ (5*1000*m) * 100%
=3*1*1.11*30/ (5*1000*1.02) * 100%
=1.95%
Embodiment 2
1) polyformaldehyde sample one is dried at 75 DEG C to constant weight, it is 12 minutes time-consuming；It is poly- after accurately weighing 1.02g drying
Formaldehyde sample one places it in reaction vessel while being added the ammonium hydroxide methanol solution 100ml that total mass concentration is 0.7%, adds
Heat obtained reaction solution to constant temperature 45 minutes after 180 DEG C；
2) reaction solution is cooled to room temperature and is transferred in titration cup, the sodium sulfite solution of 20ml is added, stir 3 points
Clock obtains prepare liquid；
3) constant-current titration is carried out with the standard hydrochloric acid solution that concentration is 1mol/L, the results show that standard hydrochloric acid solution used
Volume be 1.09ml.
Above-mentioned data are substituted into formula I, X=3*C*V*M/ (5*1000*m) * 100%
=3*1*1.09*30/ (5*1000*1.02) * 100%
=1.93%
Comparative example 1-1
1) 1.02g polyformaldehyde sample one is directly accurately weighed, place it in reaction vessel while total mass concentration is added
For 0.5% ammonium hydroxide methanol solution 100ml, constant temperature 45 minutes, obtain reaction solution after being heated to 180 DEG C；
2) reaction solution is cooled to room temperature and is transferred in titration cup, the sodium sulfite solution of 20ml is added, stir 3 points
Clock obtains prepare liquid；
3) constant-current titration is carried out with the standard hydrochloric acid solution that concentration is 1mol/L, the results show that standard hydrochloric acid solution used
Volume be 1.19ml.
Above-mentioned data are substituted into formula I, X=3*C*V*M/ (5*1000*m) * 100%
=3*1*1.19*30/ (5*1000*1.01) * 100%
=2.12%
Comparative example 2-1
1) 1.02g polyformaldehyde sample one is directly accurately weighed, place it in reaction vessel while total mass concentration is added
For 0.7% ammonium hydroxide methanol solution 100ml, constant temperature 45 minutes, obtain reaction solution after being heated to 180 DEG C；
2) reaction solution is cooled to room temperature and is transferred in titration cup, the sodium sulfite solution of 20ml is added, stir 3 points
Clock obtains prepare liquid；
3) constant-current titration is carried out with the standard hydrochloric acid solution that concentration is 1mol/L, the results show that standard hydrochloric acid solution used
Volume be 1.18ml.
Above-mentioned data are substituted into formula I, X=3*C*V*M/ (5*1000*m) * 100%
=3*1*1.18*30/ (5*1000*1.02) * 100%
=2.08%
Embodiment 3
1) polyformaldehyde sample two is dried at 80 DEG C to constant weight, it is 15 minutes time-consuming；It is poly- after accurately weighing 1.02g drying
Formaldehyde sample two places it in reaction vessel while being added the ammonium hydroxide methanol solution 100ml that total mass concentration is 0.8%, adds
Heat obtained reaction solution to constant temperature 45 minutes after 180 DEG C；
2) reaction solution is cooled to room temperature and is transferred in titration cup, the sodium sulfite solution of 20ml is added, stir 3 points
Clock obtains prepare liquid；
3) constant-current titration is carried out with the standard hydrochloric acid solution that concentration is 1mol/L, the results show that standard nitric acid solution used
Volume be 1.02ml.
Above-mentioned data are substituted into formula I, X=3*C*V*M/ (5*1000*m) * 100%
=3*1*1.06*30/ (5*1000*1.02) * 100%
=1.87%
Comparative example 3-1
1) 1.02g polyformaldehyde sample two is directly accurately weighed, place it in reaction vessel while total mass concentration is added
For 0.8% ammonium hydroxide methanol solution 100ml, constant temperature 45 minutes, obtain reaction solution after being heated to 180 DEG C；
2) reaction solution is cooled to room temperature and is transferred in titration cup, the sodium sulfite solution of 20ml is added, stir 3 points
Clock obtains prepare liquid；
3) constant-current titration is carried out with the standard hydrochloric acid solution that concentration is 1mol/L, the results show that standard hydrochloric acid solution used
Volume be 1.11ml.
Above-mentioned data are substituted into formula I, X=3*C*V*M/ (5*1000*m) * 100%
=3*1*1.11*30/ (5*1000*1.02) * 100%
=1.96%
Comparative example 3-2
Using number of patent application: CN201511021353.0, name of patent application are as follows: gaseous formaldehyde in a kind of polyformaldehyde
In content assaying method and collection device, mentions measuring method measurement for the 0128th section the 0133rd section of page-the 8 of page 7 of specification and gather
The content of free formaldehyde in formaldehyde sample two, after measured, result are 0.0859% (859ppm).
Embodiment 4
1) polyformaldehyde sample two is dried at 90 DEG C to constant weight, it is 12 minutes time-consuming；It is poly- after accurately weighing 1.02g drying
Formaldehyde sample two places it in reaction vessel while being added the ammonium hydroxide methanol solution 100ml that total mass concentration is 0.4%, adds
Heat obtained reaction solution to constant temperature 45 minutes after 180 DEG C；
2) reaction solution is cooled to room temperature and is transferred in titration cup, the sodium sulfite solution of 20ml is added, stir 3 points
Clock obtains prepare liquid；
3) constant-current titration is carried out with the standard hydrochloric acid solution that concentration is 1mol/L, the results show that standard nitric acid solution used
Volume be 1.03ml.
Above-mentioned data are substituted into formula I, X=3*C*V*M/ (5*1000*m) * 100%
=3*1*1.03*30/ (5*1000*1.01) * 100%
=1.83%
Comparative example 4-1
1) 1.02g polyformaldehyde sample two is directly accurately weighed, place it in reaction vessel while total mass concentration is added
For 0.4% ammonium hydroxide methanol solution 100ml, constant temperature 45 minutes, obtain reaction solution after being heated to 180 DEG C；Reaction is placed it in hold
The ammonium hydroxide methanol solution 100ml that total mass concentration is 0.3% is added in device simultaneously, constant temperature 45 minutes, obtain after being heated to 180 DEG C
Reaction solution；
2) reaction solution is cooled to room temperature and is transferred in titration cup, the sodium sulfite solution of 20ml is added, stir 3 points
Clock obtains prepare liquid；
3) constant-current titration is carried out with the standard hydrochloric acid solution that concentration is 1mol/L, the results show that standard nitric acid solution used
Volume be 1.07ml.
Above-mentioned data are substituted into formula I, X=3*C*V*M/ (5*1000*m) * 100%
=3*1*1.07*30/ (5*1000*1.01) * 100%
=1.90%
Comparative example 4-2
Using number of patent application: CN201511021353.0, name of patent application are as follows: gaseous formaldehyde in a kind of polyformaldehyde
In content assaying method and collection device, mentions measuring method measurement for the 0128th section the 0133rd section of page-the 8 of page 7 of specification and gather
The content of free formaldehyde in formaldehyde sample two, after measured, result are 0.0667% (667ppm).
The determination condition and result of above-described embodiment and comparative example are as shown in the table:
Table 1
From the data of embodiment 3, comparative example 3-1 and comparative example 3-2 it is found that unstable hydroxyl contains in polyformaldehyde sample two
Amount difference is 1.96%-1.87%=0.09% (900ppm), and the error rate that two methods measure is (900-859)/900=
4.56%；From the data of embodiment 4, comparative example 4-1 and comparative example 4-2 it is found that unstable hydroxyl contains in polyformaldehyde sample two
Amount difference is 1.90%-1.83%=0.07% (700ppm), and the error rate that two methods measure is (700-667)/700=
4.71%；Above-mentioned correlation data it is found that polyformaldehyde sample two before it is dried, after the difference of unstable hydroxy radical content that measures and dry
Dry preceding polyformaldehyde powder sample is almost the same using the content for the free formaldehyde that above patent document measures, and the error rate measured exists
In the range of the error of permission, the accuracy of the method for the present invention measurement is illustrated.
To sum up, using it is provided by the invention measurement polyformaldehyde sample in unstable hydroxy radical content measuring method can compared with
The accounting that hydroxyl in sample is determined in short time, can preferably instruct the adjustment of polymerization technique reaction condition, guarantee output
Polyformaldehyde sample quality.
Claims (8)
1. a kind of method of unstable hydroxy radical content in measurement polyformaldehyde, it is characterised in that: include the following steps,
1) taking quality is the polyformaldehyde sample after being dried of m, and ammonia spirit is added into the polyformaldehyde sample and carries out
Reaction, obtains reaction solution；The drying process be by the polyformaldehyde sample less than 100 DEG C at a temperature of it is dry to constant weight；
Preferably, temperature is 50-80 DEG C；
2) sodium sulfite aqueous solution is added into the reaction solution, obtains prepare liquid；
3) prepare liquid is titrated with the acid standard solution that concentration is C, and records acid standard solution used in titration process
Volume V；
If acid standard solution used is unitary acidity standard solution, obtained in the polyformaldehyde sample according to such as following formula (I)
Unstable hydroxy radical content:
X=3*C*V*M/ (5*1000*m) * 100% (I)
If acid standard solution used is binary acidic standard solution, obtained in the polyformaldehyde sample according to such as following formula (II)
Unstable hydroxy radical content:
X=6*C*V*M/ (5*1000*m) * 100% (II)
C: acid concentration of standard solution, mol/L；
V: the volume of the acid standard solution of consumption, ml are titrated；
M: the molal weight of formaldehyde, g/mol；
M: the quality of polyformaldehyde sample, g.
2. according to the method described in claim 1, it is characterized by: the unitary acidity standard solution is hydrochloric acid standard solution
Or nitric acid standard solution, the binary acidic standard solution are sulfuric acid standard solution.
3. according to the method described in claim 2, it is characterized by: the unitary acidity standard solution and the binary acidic mark
The concentration of quasi- solution is 1mol/L.
4. according to the method described in claim 3, it is characterized by: the polyformaldehyde sample is polyformaldehyde slurry sample or poly- first
Aldehyde powder sample.
5. method according to claim 1-4, it is characterised in that: the reaction temperature in step 1) is 120-200
DEG C, reaction time 30-60min.
6. according to the method described in claim 5, it is characterized by: ammonia spirit in step 1) is the methanol solution of ammonium hydroxide,
The total mass concentration of the methanol solution of the ammonium hydroxide is 0.2%-1%, preferably 0.4%-0.8%；Wherein, the matter of ammonia spirit
Amount concentration is 20%-30%, and the mass concentration of methanol solution is 100%.
7. according to the method described in claim 6, it is characterized by: the concentration of step 2) sulfite sodium water solution is 1mol/
L。
8. according to the method described in claim 7, it is characterized by: in step 3) using automatical potentiometric titrimeter titration it is described to
Survey liquid.
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