JPS6312085B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention uses an aqueous suspension polymerization method that uses water as a medium and uses a water-soluble redox catalyst to produce an AN polymer having an acrylonitrile (hereinafter abbreviated as AN) content of 85% by weight or more, and which has a large energy-saving and rationalization effect. This relates to a method for producing by a coalescence production method, and its purpose is to obtain a polymer with excellent permeability, dehydration properties, and drying properties in aqueous suspension polymerization using a water-soluble redox catalyst. In addition, this polymer can be subjected to the usual excessive dehydration operation, that is, with an overpressure difference of 1.1 Kg/cm ² G or less, or centrifugally dehydrated with a centrifugal force of 1000 g or less, until the water content is 10 to 10.
The aim is to obtain a 150% by weight (dry basis) hydrous polymer. Used for manufacturing molded products such as fibers
It is advantageous to produce AN polymers by aqueous suspension polymerization, but when producing AN polymers by aqueous suspension polymerization, the polymerization product is usually filtered, washed,
Drying is often required after dehydration. Therefore, it is extremely preferable to obtain a polymer obtained by aqueous suspension polymerization that has good overwashing and dehydration properties and also has good drying properties from the viewpoint of economy and energy saving. Alternatively, the polymer product obtained by aqueous suspension polymerization may be subjected to a pressure difference of 1.1 Kg/cm ² G or less, or
Polymers that can be centrifugally dehydrated with a centrifugal force of 1000 g or less and have a water content of 10 to 150% by weight (dry basis) have particularly excellent drying properties and are excellent in energy saving effects. Based on the above-mentioned concept, the present inventors have completed the present invention as a result of intensive study on a method for producing an AN-based polymer that can achieve the above-mentioned purpose.The gist of the invention is that the AN content is 85% or more and other monomers in a proportion of 15% by weight or less, and the electrolyte concentration
In a system of 0.12 mol/or less, the weight ratio of water to the monomer is 3.5 or less, and the equivalent ratio of reducing agent/oxidizing agent is in the range of 1.0 to 12.0. Moisture content is 10 to 150% by weight (dry basis) by centrifugal dehydration at a pressure of 1.1 Kg/cm ² G or less or centrifugal force of 1000 g or less.
A method for producing an acrylonitrile polymer is provided. The AN polymer according to the present invention has AN alone or a known monomer as the second and third components.
A polymer with an AN content of 85% by weight or more, containing 1 to 15% by weight of neutral monomers such as vinyl acetate, methyl acrylate, and methyl methacrylate as known monomers.
0.1 to 5% by weight of acidic monomers such as methallyl sulfonic acid and p-sulfophenyl methallyl ether;
It may contain 1 to 15% by weight of a basic monomer such as dimethylaminoethyl methacrylate, and 1 to 15% by weight of acrylamide or methacrylamide. Moreover, it is not limited to these. As the water-soluble redox catalyst for the present invention, commonly known catalysts can be used. For example, as redox catalysts, potassium persulfate and acidic sodium sulfite, ammonium persulfate, sulfite anhydride, and caustic soda,
Combinations of hydrogen peroxide and acidic sodium sulfite, hydroxylamine sulfonate and acidic sulfite, etc. can be used, but are not limited thereto. The electrolyte concentration of the polymer relating to the present invention shall be defined and calculated by the following formula. In this case, the electrolyte includes water-soluble acids or alkalis such as sulfuric acid, nitric acid, sulfurous acid, caustic soda, and soda carbonate, and water-soluble salts such as sodium chloride, sodium sulfate, and ammonium sulfate. Note that when acid and alkali are charged at the same time, the calculated molar concentration of the water produced by neutralization is subtracted from the electrolyte concentration [mol/]. For example, anhydrous sulfite 0.05 mol/min and caustic soda 0.07
When charged into a polymerization system at mol/min, calculate according to the following formula. Electrolyte molar concentration in the polymerization system = Anhydrous sulfite molar concentration + Caustic soda molar concentration - Produced water molar concentration = 0.05 + 0.07 - 0.05 = 0.07 Electrolyte concentration in the polymerization system [mol/] = (Polymerization system relative to the water charged to the polymerization system Molar concentration of catalyst and electrolyte charged in [mol/
) The electrolyte concentration in the polymerization system must be 0.12 mol/or less; if it exceeds 0.12 mol/, the dehydration and overwashing properties of the produced polymer will be insufficiently improved. Furthermore, the weight ratio of water to the monomer (water/monomer ratio) charged into the polymerization system is desirably 3.5 or less, preferably 3.2 or less; if it exceeds 3.5, the polymer product obtained by the above-mentioned present invention The effects of improving dehydration and overwashing properties become insufficient. Furthermore, in the present invention, the equivalent ratio of the reducing agent/oxidizing agent of the redox catalyst is
It is necessary to keep it between 1.0 and 12.0. In order to reduce the electrolyte concentration in the polymerization system, it is effective to lower the equivalent ratio of reducing agent/oxidizing agent, but reducing this ratio below 1.0 generally reduces the thermal stability of the resulting polymer. Also, the degree of polymerization tends to be excessive, which is not preferable. On the other hand, if the reducing agent/oxidizing agent equivalent ratio is made larger than 12.0, the amount of catalyst used increases to obtain a polymer with a degree of polymerization within the normal range, and the electrolyte concentration in the polymerization system is reduced to 0.12 mol/min.
It becomes difficult to maintain the temperature below, which is not desirable. Therefore, in the present invention, it is necessary to maintain the reducing agent/oxidizing agent equivalent ratio of the redox catalyst between 1.0 and 12.0. In order to maintain the electrolyte concentration in the polymerization system at 0.12 mol/lower, in addition to keeping the reducing agent/oxidizing agent ratio within the specified range, a trace amount of a water-soluble heavy metal salt such as a trace amount of ferrous sulfate or copper sulfate may be used in combination. The amount of catalyst used can also be reduced by the combined use of small amounts of chain transfer agents, such as mercaptans. It is also possible to use a small amount of surfactant in the polymerization. The polymerization degree of the polymer according to the present invention is preferably in the range of 0.12 to 0.25 in terms of specific viscosity (value at 25° C. of a 100 ml dimethylformamide solution of 0.1 g of the polymer). In the present invention, by keeping the electrolyte concentration in the polymerization system at 0.12 mol/or less and by keeping the weight ratio of water to the monomer at 3.5 or less, the dehydration and drying properties of the resulting polymer are improved. The bulk density increases and the effects of the present invention can be obtained. In this case, the produced polymer particles become denser, the particle shape approaches a spherical shape, and the bulk density of the produced polymer increases,
As a result, it is thought that the overwashing properties, dehydration properties, and drying properties of the produced polymer are improved, but the details of the cause are not necessarily clear. In the present invention, the produced polymer product is dehydrated using a commonly known rotary vacuum filtration machine or a centrifugal dehydrator, and when passing through a rotary vacuum filtration machine,
The pressure difference, that is, the pressure difference between the suction side and the overcake surface is
If using centrifugal dehydration, dehydrate with centrifugal force of ^1000g or less, and reduce the water content to 10~1.1Kg/cm2G.
150% by weight (dry basis). The polymer product polymerized by the polymerization method of the present invention has good dehydration properties, and can have a water content of 10 to 150% by weight by the commonly known over-dehydration operation and conditions as described above. The water content after dehydration according to the present invention varies depending on the polymer composition, degree of polymerization, and polymerization conditions, and also varies depending on overpressure when using a vacuum filtration machine and centrifugal force when using a centrifugal dehydrator. That is, for a polymer having a certain polymer composition and degree of polymerization, the lower the electrolyte concentration in the polymerization system and the lower the water/monomer weight ratio supplied to the polymerization system, the better the dehydration properties of the polymer will be. Therefore, a polymer with a low water content can be obtained, and the dehydration property, that is, the water content, changes depending on the combination of the electrolyte concentration and the weight ratio of feed water/monomer. Further, when using a vacuum filtration machine, the larger the overpressure is, and when using a centrifugal dehydrator, the larger the centrifugal force is, the lower the water content of the polymer can be obtained. The AN polymer having a water content of 10 to 150% by weight according to the present invention has a relatively low water content and a high drying rate, so it has a large energy saving effect. The AN polymer of the present invention with a moisture content of 10 to 150% by weight has an excellent drying rate, but this is due to the particle shape of the polymer of the present invention and the moisture content of 10 to 150% by weight.
It is thought that this is related to the state of water present when dehydrated to 150% by weight, but the details are not necessarily clear. The content of the present invention will be explained by way of examples. [Example] A polymerization reactor with a capacity of 80 and equipped with a stirrer was charged with 30% of ion-exchanged water (PH3), and a monomer having a composition of 90% AN by weight and 10% by weight of vinyl acetate was added to acidic sulfite at a rate of 333g/min. Sodium 5.18g/min, potassium persulfate 1.77g/min, ferrous sulfate (FeSO ₄
7H ₂ O) 0.001 g/min, sulfuric acid 0.52 g/min, and ion exchange water 1058 g/min. The polymerization temperature was maintained at 50°C, each feed solution was continuously supplied, and the polymerization product was continuously taken out from the overflow port. The amount of stagnant liquid in the polymerization reactor was maintained at 80 ml, and sufficient stirring was performed continuously. Several hours after the start of polymerization, the polymerization reaction reached steady state. The electrolyte concentration in the polymerization system when a steady state was reached was calculated using the following formula. Polymerization electrolyte concentration [mol/] = (5.18/1058) (1/104) (10 ³ ) + (1.77/1058)
(1/270) (10 ³ ) + (0.52/1058) (1/98) (10 ³ ) = 0.0582 The reducing agent/oxidizing agent equivalent ratio was calculated from the following formula. Reducing agent/oxidizing agent equivalent ratio = (5.18/104)/(1.77/270) = 7.60 When a steady state is reached, the polymerization product is taken out, overwashed and dried using the method described in the text, and the dried polymer powder is When the bulk density was measured, it was 0.41.
On the other hand, the aqueous suspension of the polymerization product that had reached a steady state was subjected to an over-dehydration test using Toyo Paper No. 2 (diameter 9 cm) with a Buchner To at a vacuum degree of 400 mmHg. That is, after suctioning off an amount of the polymerization product such that the cake thickness after filtration is 10 mm, it is washed with ion-exchanged water of 5 times the weight of the polymer, and then dehydrated until cracks are formed in the cake. Moisture content and residual sodium in the cake were measured. During this overtest, the degree of vacuum on the suction side was maintained at 400 mmHg. An over-dehydration test was also conducted on the aqueous suspension of the polymerization product of the comparative example under the same conditions. To measure the residual sodium, use the washed and dehydrated cake.
After drying to a constant weight at 105℃, take 5g and put it in a platinum crucible.
After heating and carbonization, it was further incinerated at 800°C in an electric furnace, dissolved in diluted hydrochloric acid, diluted with water, and the amount of sodium was determined by flame spectroscopy. The results of the above-mentioned excessive dehydration test are as follows: The polymer of the example has a significantly lower water content than the polymer of Comparative Example 1 or 2, and has excellent dehydration properties. It can be seen that the polymers of the Examples were washed at a higher speed than the polymers of the Comparative Examples, and that the washing was carried out satisfactorily even though the residual sodium content after washing was almost the same and the washing speed was high.

【table】

[Table] A drying test of the polymer was also conducted. That is, the aqueous suspension of the polymerization product that has reached a steady state is passed through a rotary vacuum filtration machine at a vacuum level of 400 mmHg using a gold cloth (S-618, 127 x 124 pieces/inch) as a cloth, and then the amount of the polymer is 5 times that of the polymer. After washing with ion-exchanged water of
After spreading to a thickness of cm, the temperature is 85-86℃ and the humidity is about 6g.
A drying test was conducted by supplying air from below the net under the conditions of H ₂ O/Kg dry air and an air supply amount of approximately 2 tons/hr.m ² .
On the other hand, the same test was conducted on the polymerization product of Comparative Example. The test results are as shown below, and it can be seen that the polymer of the example has a shorter drying time than the polymer of the comparative example, even though the polymer weight per unit volume of dehydrated cake is 1.35 times greater.

[Comparative example 1]

Ion-exchanged water (PH
3) A monomer having the same composition as in the example was charged at a rate _of 280 g/min _. O) 0.0007g/min, sulfuric acid 0.55
The supply of ion-exchanged water was started at a rate of 1,176 g/min, and polymerization was carried out in the same manner as in Examples. The electrolyte concentration in the polymerization system when a steady state was reached was calculated using the following formula. Polymerization electrolyte concentration [mol/] = (5.5/1176) (1/104) (10 ³ ) + (1.45/1176)
(1/270) (10 ³ ) + (0.55/1176) (1/98) (10 ³ ) = 0.054 After reaching steady state, take out the polymerization product,
The bulk density of the dried polymer powder, which was overwashed and dried according to the method described in the text, was measured to be 0.33. [Comparative Example 2] Ion-exchanged water (PH
3) Acidic sodium sulfite was added at a rate of 333 g/min to monomers having the same composition as in the example.
16.2g/min, potassium persulfate 1.60g/min, ferrous sulfate (FeSO ₄ 7H ₂ O) 0.001g/min, sulfuric acid 0.86
The supply of ion-exchanged water was started at a rate of 1,058 g/min, and polymerization was carried out in the same manner as in Examples. The electrolyte concentration in the polymerization system when a steady state was reached was calculated using the following formula. Polymerization electrolyte concentration [mol/] = (16.2/1058) (1/104) (10 ³ ) + (1.60/1058)
(1/270) (10 ³ ) + (0.86/1058) (1/98) (10 ³ ) = 0.161 After reaching steady state, take out the polymerization product,
The bulk density of the dried polymer powder, which was overwashed and dried according to the method described in the text, was measured to be 0.33. As is clear from the comparison between Examples and Comparative Examples above, when the supplied water/monomer weight ratio is 4.2 as in Comparative Example 1, even if the electrolyte concentration in the polymerization system is sufficiently low, the polymer dehydration The improvement and increase in polymer bulk density are insufficient, and the effects of the present invention cannot be expected.
Furthermore, as in Comparative Example 2, even when the supplied water/monomer weight ratio is 3.2, the electrolyte concentration in the polymerization system is 0.160.
mol/, the improvement in polymer dehydration property and the increase in polymer bulk density are insufficient. The unique effects of the present invention can be obtained by controlling the supplied water/monomer weight ratio to 3.5 or less and by controlling the electrolyte concentration in the polymerization system to 0.12 mol/less or less, as in the present invention. The method for measuring the bulk density of a polymer in the present invention is as follows. Using Toyo Paper No. 2, the sufficiently uniformly mixed polymerization product aqueous suspension was heated with a Buchner funnel at a pressure of 400 mm.
After filtration with Hg and subsequent washing with ion-exchanged water of 10 times the weight of the polymer, the polymer was dried at room temperature under reduced pressure until it reached a constant weight, and the dried polymer was loosened by hand.
Sieve through a mesh sieve to remove a small amount of coarse particles and measure the bulk density. Fill a 2 mm thick cylindrical container A with an inner diameter of 68 mm and a depth of 68 mm with a 3 mm diameter hole in the center of the bottom by pressing the bottom hole with your finger and filling it with polymer powder. Cylindrical container B with an outer diameter of 67 mm, a depth of 67 mm, and a wall thickness of 1 mm.
, then turn it upside down, release the finger pressing the hole in the bottom, and transfer the polymer from container A to container B. Place container B on a horizontal floor and stroke the rim of the container with a round, straight stick to remove excess polymer in container B. Next, the weight of container B containing the polymer is measured. Calculate the bulk density using the formula below. Bulk density = (weight g of container B containing polymer) - (container B
weight g)/(inner volume of container B cc)

Claims (1)

[Claims] 1 Electrolyte concentration 0.12 mol/composition consisting of 85% by weight or more of acrylonitrile and 15% by weight or less of other monomers.
In the following aqueous systems, the weight ratio of supplied water to monomer is 3.5 or less, and the equivalent ratio of reducing agent/oxidizing agent is
By supplying the polymer with a composition of 1.0 or more and 12.0 or less, the polymerization product was continuously polymerized at a pressure difference of 1.1Kg/cm ² G.
Water content is 10 to 150% by weight by centrifugal dehydration at the following pressure or centrifugal force of 1000 g or less.
(Dry basis) A method for producing an acrylonitrile polymer, characterized by obtaining a polymer.