JPS6197309A - Production of n-vinylformamide polymer - Google Patents

Abstract

PURPOSE:To produce the title high-quality polymer in high yields without using any highly toxic compound, by reacting formamide with actaldehyde, reacting the product with an alcohol, eliminating an alcohol group from the product and polymerizing the product. CONSTITUTION:Formamide is reacted with acetaldehyde in the presence of a basic catalyst to obtain N-(alpha-hydroxyethyl)formamide (A). Compound A is reacted with a prim. or sec. alcohol in the presence of an acidic catalyst to obtain an N-(alpha-alkoxyethyl)formamide (B). Compound B is heated to 250-600 deg.C in a vapor phase to obtain N-vinylformamide (C) by eliminating an alcohol group. The title polymer is produced by polymerizing compound C in the presence of a radical initiator. According to this process, it is possible to produce easily the title high-quality polymer in extremely good yield without using any highly toxic compound by the above reaction shown in the formula.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing an N-vinylformamide polymer according to the following reaction formula.

Polymers of N-vinylformamide are obtained by homopolymerization of N-vinylformamide or copolymerization with other vinyl monomers using a radical mechanism, and are widely applied to water-soluble or koji, aqueous polymer applications. can do. In particular, polyvinylamine obtained by hydrolyzing N-vinylformamide polymer can be used as a flocculant, a paper-making agent,
This will greatly contribute to the field of application of cationic polymer electrolytes such as ion exchange resins.

[Prior art]

Conventionally, the method for producing N-vinylformamide, which is a raw material monomer, is as follows: (1) Acetaldehyde cyanohydrin obtained by reacting acetaldehyde with hydrogen cyanide is used as a raw material, and formamide is reacted with the acetaldehyde cyanohydrin to produce N-(α-cyanoethyl ) formamide, and hydrogen cyanide is split from this to obtain an N-vinyl compound. (2) N-formyl-α-arani/l or N-ethylformamide and methanol are reacted with an electrode to form N-(α-methoxyethyl ) There are known methods to obtain formamide, de, and methanol from this, and to obtain N-vinyl compounds, but method (1) is difficult to manufacture due to the safety of raw materials and by-products. Polymerization of monomers that are radically polymerized is not a satisfactory method for industrially producing N-vinylformamide polymers. Method (2) is difficult to implement industrially using an electrode reaction, and cannot be used as a preliminary step for producing an N-vinylformamide polymer.

[Object of the Invention] An object of the present invention is to provide a method for producing an N-vinylformamide polymer that is industrially more advantageous than the conventional method. Therefore, the object of the present invention is to provide, as a first step, a step in which formamide and acetaldehyde are reacted in the presence of a basic catalyst to obtain N-(α- and droxyethyl)formamide.

As the second step, the 11-(α-
A step of reacting hydroxyethyl)formamide with a primary or secondary alcohol in the presence of an acidic catalyst to obtain N-(α-alkoxyethyl)formamide, the third step being the N- obtained in the second step. (α-alkoxyethyl)formamide in gas phase from 2jO to 600
℃ to perform a dealcoholization reaction to obtain N-vinylformamide; as a second step, the 11-vinylformamide obtained in the third step is polymerized in the presence of a radical initiator to obtain N-vinylformamide. This is achieved by a method for producing an N-vinylformamide polymer, which is characterized by including a step of obtaining a polymer.

[Structure of the invention]

(First Step) As the catalyst used in the reaction of formamide and acetaldehyde in the present invention, any general basic compound can be used.

These include hydroxides of alkali metals, alkaline earth metals, quaternary ammonium, etc., tertiary P amines, strong bases, ion exchange resins that act on weak bases, and weak base salts consisting of strong bases and weak acids. However, the preferred base catalyst is a weakly basic salt consisting of a strong base and a weak acid, particularly a weakly basic salt consisting of a strong base and a weak acid having a PKa value of μ to /j. Here, the PKa value is 0.0 / mot / in an aqueous solution of 8 degrees 2j
Means the value in °C. Examples of such weakly basic salts include a variety of substances, including strong bases such as hydroxides such as lithium, sodium, or potassium, organic acids, phenols, and sulfites.

Examples include salts with weak acids such as phosphorous acid, hypophosphorous acid, pyrophosphoric acid, phosphoric acid, carbonic acid, boric acid, and metasilicic acid. Weakly basic salts preferred for % are potassium carbonate, sodium carbonate, potassium phosphate, sodium phosphate, potassium pyrophosphate,
Sodium pyrophosphate.

The proportion of the weakly basic salt used as a catalyst for the reaction between formamide and acetaldehyde is usually as follows:
It is suitably selected from the range of 0.0/-10 moles, preferably o, t-r moles.

The reaction temperature between formamide and acetaldehyde is -1
Although it can be selected from a wide range of 0-600°C, it is preferably in the range of 0-40°C from the viewpoint of acetaldehyde selectivity.

The ratio of the reaction raw materials, formamide and acetaldehyde, is usually selected from the range of /:/, 0-1.0 (molar ratio), but the preferred ratio depends on the manner in which acetaldehyde is supplied to the reaction system. For example, when acetaldehyde is supplied in gaseous form, / : 1
,0~/,2 (molar ratio), if supplied in liquid form, l:
The range is i, r~≠0 (molar ratio).

The reaction between formamide and acetaldehyde can be carried out using any reaction apparatus according to various conventionally known formats, but the supply mode of acetaldehyde, if it is in a gaseous state, is as described above. It is economically advantageous because a high yield can be achieved at a usage rate of acetaldehyde close to the molar amount. A preferred reaction method is to charge a catalyst and formamide into a stirring chamber, and to continuously feed gaseous acetaldehyde in small portions into the liquid.

Although the reaction can also be carried out in the absence of a solvent, the product N-(α-hydroxyethyl)formamide has a melting point of ~s 3.1 If the reaction is carried out without a solvent at the preferred temperature of 3.1'C for a crystalline substance, the product will precipitate and solidify at the end of the reaction, so use a solvent that can disperse the crystals. It is preferable. Specific examples include aliphatic hydrocarbons such as hexane and heptane, and aromatic hydrocarbons such as benzene, toluene and xylene. The amount of solvent used is usually 0.2 to -2 to formamide.
It is appropriately selected from the range of weight times. Note that the r-medium may be added to the reaction system immediately before the crystal precipitation described below.

The reaction product of formamide and acetaldehyde, N-(
α-Hydroxyethyl) formamide is used during the reaction in which precipitation does not occur under normal conditions. Specifically, the conversion rate of formamide is 10 to 10 mol, preferably 4
It is preferable to precipitate crystals by cooling or adding crystal nuclei within the range of mortise because the yield of the product can be increased.

Therefore, after the remaining amount of acetaldehyde determined in advance is fed into the liquid as a gas and dissolved, crystals of N-(α-hydroxyethyl)formamide are precipitated according to the method described above, and then the reaction is continued. Alternatively, N-(α-hydroxyethyl)formamide can be obtained almost quantitatively by precipitating crystals in advance and then feeding the remaining amount of acetaldehyde gas into the liquid to continue the reaction. Cooling is carried out by lowering the reaction temperature to -20-2°C, preferably in the range -j to 10°C, and the addition of crystal nuclei is carried out by adding N −(α−
This is carried out by adding a small amount of (hydroxyethyl)formamide to the reaction system as crystal nuclei.

(Second step) N-(α-hydroxyethyl)formamide obtained as crystals after the reaction is hygroscopic and unstable to heat, and easily decomposes into the raw material formamide and acetaldehyde, so it is not isolated. By reacting with alcohol, decomposition reactions are completely avoided and N-(α
-alkoxyethyl)formamide can be obtained. By reacting N-(α- and droxyethyl)formamide obtained in an uncrystallized state with alcohol, it is converted into N-(α-alkoxyethyl)formamide with high selectivity, and then processed by known means such as distillation. It can be taken out.

In the method of the present invention, N-(α-hydroxyethyl) is used, but from the viewpoint of reactivity and solubility with N-(α-hydroxyethyl)formamide, alcohols having a carbon atom number of 1/-1 are preferred. Polyhydric alcohols Although this is undesirable as it gives more than one type of reactant and the product becomes complex, it does not become an obstacle to the cleavage of the alkoxy group to form N-vinylformamide.

Particularly preferred alcohols from the viewpoint of reactivity are primary alcohols having a valence of -10 carbon atoms, such as methanol, ethanol, n-propanol, n-butanol, isobutyl alcohol, comethoxyethanol, and coethoxyethanol. be.

The amount of alcohol to be used relative to M-(α-hydroxyethyl)formamide can be determined arbitrarily, but N-
(α-Hydroxyethyl)formamide is a thermally unstable compound and is difficult to recover after the reaction, so it is preferable to use the alcohol in an equimolar or excess amount.1 Usually 1.0~
Thirty times the molar amount of alcohol is used. Since M-(α- and droxyethyl)formamide is a crystalline compound, it is preferable to use the alcohol used in the reaction as a solvent, and in this case, the amount of alcohol used is 1.
It is preferably 0 to 0 times the mole.

Depending on the type of alcohol, it can easily form acetal with unreacted acetaldehyde, so in addition to the amount of alcohol mentioned above,
It is preferable to increase the amount of alcohol by twice the molar amount.

In order to minimize the amount of alcohol used, an inert solvent may be used in the reaction if appropriate.

As the catalyst used for the reaction of N-(α-hydroxyethyl)formamide and alcohol, any general acid catalyst can be used. #acid, organic acid,
Examples include ion exchange resins, solid acid catalysts, etc. that exhibit weak acidity and strong acidity, and among these, strongly acidic substances are preferably used. Examples of preferred acid catalysts include sulfuric acid, hydrochloric acid, nitric acid, hydrogen bromide, sulnic acid, methanesulfonic acid, ethanesulfonic acid, p-toluenesulfonic acid, and crosslinked polystyrenesulfonic acid. The amount of the acid catalyst used is 0.00% relative to N-(α-hydroxyethyl)formamide.
00/~lO morti, preferably ld, 0. / −
The range is 1 mole. Furthermore, when a heterogeneous catalyst such as an ion exchange resin is used, the raw material mixture can be passed through a column filled with the catalyst to cause the reaction.

The reaction between N-(α-hydroxyethyl)formamide and alcohol is easily accomplished by adding an acid catalyst to a mixture of the two or by bringing them into contact. The reaction temperature is preferably in the range of -10 to 10°C from the viewpoint of reactivity and stability of N-(α-hydroxyethyl)formamide. Particularly preferred is a range of θ to 0°C. The reaction product can also be isolated by a commonly known method such as concentration or distillation after neutralizing or separating the acid catalyst.

(Third step) N-(α-alkoxyethyl) obtained in the second step
N-vinylformamide is obtained by heating formamide in the gas phase and causing a dealcoholization reaction.

As a method for vaporizing N-(α-alkoxyethyl)formamide, a method of heating under an inert gas stream, a method of heating under reduced pressure, a method of heating under reduced pressure in the presence of an inert gas, etc. can be used. Vaporizing Temperature Company Normal 6
The dealcoholization reaction is usually carried out between 00°C and 200°C, preferably between 0°C and 600°C, preferably between +7 and 600°C. Examples of methods for heating N-(α-alkoxyethyl)formamide in the gas phase include contacting the gas with a heating furnace filled with glass, quartz, metal, etc., and contacting it with heated inert gas. can be mentioned. The residence time of gas is 0.0/~λO
Preferably, this is done in seconds.

(Shihiro step) An N-vinylformamide polymer is obtained by polymerizing the N-vinylformamide obtained in the third step in the presence of a radical polymerization initiator. N-vinylformamide can be directly polymerized in bulk without using a solvent, or N-vinylformamide polymers can be obtained by solution polymerization using various organic solvents that dissolve N-vinylformamide. It is preferable to polymerize in an aqueous solution because a polymer having an extremely high molecular weight can be easily obtained in high yield. N-vinylformamide can be copolymerized with various radically polymerizable vinyl monomers, but when copolymerized in an aqueous solution, it is copolymerized with acrylic acid or methacrylic acid and their derivatives, acrylamide or methacrylamide and their derivatives. KotoK
Higher molecular weight polymers can be obtained.

The concentration of polymerized N-vinylformamide or a mixture of N-vinylformamide and a monomer to be copolymerized in an aqueous solution is preferably 1 to 10% by weight, preferably io to 60% by weight.
It is preferable to carry out the reaction within the range of 100 to 1000 ml, and if necessary, a more hydrophilic organic solvent may be mixed. What is the pH of the aqueous solution? ~i
.

Preferably, it is adjusted to J-t.

Examples of radical polymerization initiators include oil-soluble azo compounds, water-soluble azo compounds, hydrogen peroxide, persulfates, perchlorates,
Hydroperoxide.

dialkyl peroxide, diacyl peroxide,
Ketone peroxide, alkyl perester, peroxydicarbonate, etc. are used, but azo compounds are preferred in order to obtain a high molecular weight polymer. Particularly preferred are water-soluble azo compounds. Examples of preferred water-soluble azo compounds include l'i2. Co′-7zobis(coamidinopropane) di-salt filling, azobis(M,N-dimethyleneinbutyramidine)・-ZtJjR salt, Hiroshi, San′
Examples include -Azobisu (Hiro-cyanovalerina #)-Coronatrium. The amount of the radical polymerization initiator used is o, o relative to the weight of N-vinylformamide or a mixture of N-vinylformamide and other copolymerizable monomers.
oz~! The weight percent is preferably selected in the range of 0.0j to 0.2wt.

Polymerization temperature #i can be selected in the range of 10°C to /10°C depending on the molecular weight of the desired prize material. When polymerizing in an aqueous solution, the temperature is 0°C to 10°C, preferably 0°C to 10°C.

The present invention is not limited to the polymerization method and the order of addition, but examples of aqueous solution polymerization include a method of polymerizing with stirring, a method of polymerizing adiabatically in a static container, a method of polymerizing while removing heat in a sheet form, and an oil-in-water type. Examples include a method of polymerizing in an emulsion state, a method of polymerizing in a water-in-oil emulsion, or a method of polymerizing in a dispersion state.

As a method of polymerizing with stirring, N-vinylformamide Q
An example of a method is to remove oxygen from the aqueous solution by passing a nitrogen scum through it, bring it to a predetermined temperature, add a radical polymerization initiator, and maintain the temperature at a predetermined temperature under a nitrogen gas flow.

〔Example〕

Below, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples unless the gist thereof is exceeded.

Example / (1) Synthesis of N-(α-methoxyethyl)formamide A small amount was placed in the exhaust pipe of a 21-sill flask equipped with a stainless steel stirrer, a gas inlet tube, a thermometer, and an ice-cooled condenser with an exhaust pipe. A trap containing liquid paraffin was connected.

Equipped with electromagnetic stirrer, warming device and needle valve /l
Approximately 710 tug of acetaldehyde was placed in a pressure-resistant glass reactor, and the needle pulp and gas inlet tubes of the Santsuro flask were connected with fluororesin tubes. Formamide IIzot (io moles), potassium carbonate 6,
Add t% n-hexane azot''g (!C) and stir vigorously while maintaining the temperature.

The pressure-resistant glass reactor was maintained at .mu.o.degree. C., and while acetaldehyde was being stirred, a needle valve was gradually turned on and acetaldehyde was introduced in gaseous form into the reaction solution. Observe the trap containing liquid paraffin, adjust the needle pulp and adjust the bath temperature so that the maximum amount of acetaldehyde is supplied without leaking from the trap in gaseous form. When reacted at ℃3.
In 5 hours! JOf (12 moles) of acetaldehyde was absorbed. After the supply of acetaldehyde was stopped and the mixture was stirred for an additional 30 minutes, the mixture was cooled to j'cK, and the reaction product crystallized to form a slurry. Since heat is generated due to crystallization, the mixture was cooled again to 0.degree. C., then methanol of 002 was added thereto, the temperature was raised to 20.degree. C. with stirring, and a mixture of sulfuric acid and methanol of 11 was added to obtain a clear solution. After reacting at 1°C for several hours, aqueous ammonia was added to neutralize the mixture, and the resulting inorganic substances were filtered through a Nutsche filter.

The upper n-hexane layer of the P solution was separated, concentrated using an evaporator, and then distilled under reduced pressure. As a result, N-(α-methoxyethyl)formamide containing 2.5% by weight of formamide (
Boiling point 70-73℃ 10.2rmHf) Get a tip &
, the yield relative to formamide was j, j%.

(2) On the synthesis side of N-vinylformamide, a stainless steel electric furnace with an inner diameter core-to-core length of 300 vrm was installed vertically, and the diameter/, jwl! filled with glass beads. The column temperature was maintained at 〇θ°C, and the reaction product was introduced from the top of the /≠j WPHP under reduced pressure at a rate of i,ot per minute with nitrogen gas per molecule ornt using a metering pump.

The distillate was cooled with a Dimroth and then collected into a trap cooled with dry ice. After removing methanol with an evaporator, the mixture was distilled under reduced pressure using an IOC Vigreux column. Formamide - N-vinylformamide containing 4'% (It!, 4.u/~'A
4'℃ 10. /rtanllt) 6
6/eta. This yield is 9 g based on the raw material formamide.
Corresponds to %.

(3) Synthesis example of N-vinylformamide polymer 1o equipped with a stirrer, cooling tube, nitrogen gas introduction tube, and initiator inlet
The above product 10. II, was dissolved in Jf's demineralized water and introduced. After heating to 50℃ while passing nitrogen gas, 107gJ% of N, N'
-7 Zobisusi 1 (2-amif/nopropane) Kotananohana aqueous solution 0, J
t was added and held at 50° C. for 1 hour while stirring under a gas flow. The reduced viscosity of the product was ηBp/c = 3, and the polymerization rate was 1,1. The consistent yield from raw formamide corresponds to g≠t. The consistent yield from the raw material acetaldehyde corresponds to 70%.

Example 1 N-(α-(2-methyloxy)ethyloxyformamide was synthesized under the same conditions as in Example 1, except that 2.2501 comethoxyethanol was used instead of methanol in Example 1.

Formamide-free product lλjot (boiling point 4
4~rij'C/0.6jtenet) was obtained. The yield based on formamide was rsl.

Thermal decomposition was carried out under the same conditions as in Example 1 to obtain N-vinylformamide that does not substantially contain formamide at a yield of 7%.
Synthesized with.

Polymerization was carried out under the same conditions as in Example 1 to obtain an N-vinylformamide polymer. The reduced viscosity of the product is ηBp10=4.
/, the polymerization rate was tata, j%. The consistent yield from the raw material formado corresponds to 73%. The consistent yield from the raw material acetaldehyde corresponds to 60%.

Comparative Example 1 Lactonitrile and formamide
6 10% yield from lactonitrile according to Example 1
(Literature value 1.2%), produced N-formalanine nitrile with a yield of 36% from formabad. Do this according to the example! Dehydrocyanation was carried out under the conditions of rraHf and 600° C. to obtain N-vinylformamide with a yield of 3tH (yield 4Cj% from N-formazuralanine determined from literature values).

Distilled Shun Example 1 with the same selling conditions as Example 1.

(υN-vinylformua<h' Polymerization was carried out under the same conditions as in the synthesis example of the polymer. The reduced viscosity of the product was ηep/C
= 3.2, polymerization rate is 17. It was a flathead. The consistent yield from the raw material Formabad corresponds to 1. The consistent yield from the raw material lactonitrile corresponds to 26.j%.

(Measurement of reduced viscosity) Add heavy substances/0.0% to specified food water. It was determined from the value (in seconds) measured at 0.degree. C. using an Ostwald viscometer (to=j012 seconds) after dissolving the solution at a concentration of /li/at.

(IR polymerization rate measurement) Approx.
t was dissolved in 200 rnl of precisely weighed demineralized water. After adding and dissolving sodium acetate jf. Aqueous iodine solution
ml and stored for 30 minutes. This solution was titrated with n normal aqueous sodium thiosulfate solution using starch as an indicator. A blank test was conducted under the same conditions, and the polymerization rate was calculated from the difference in titer.

〔Effect of the invention〕

According to the method for producing N-vinylformamide polymers of the present invention, acetaldehyde, formamide, and alcohol are used as raw materials without using highly toxic nitrile compounds as starting materials, and the product can be produced in extremely high yield and easily with high quality. N of
- Since vinylformado polymers can be produced, it will greatly contribute to the field of application of water-soluble and hydrophilic polymers.

Claims (1)

[Claims] (1) As a first step, a step of reacting formamide and acetaldehyde in the presence of a basic catalyst to obtain 11-(α-hydroxyethyl)formamide; as a second step, a step of obtaining 11-(α-hydroxyethyl)formamide obtained in the first step; A step of reacting (α-hydroxyethyl)formamide with a primary or secondary alcohol in the presence of an acidic catalyst to obtain N-(α-alkoxyethyl)formamide. 2 N-(α-alkoxyethyl)formamide in the gas phase
N-
The step of obtaining vinylformamide is characterized in that the fourth step includes a step of polymerizing the N-vinylformamide obtained in the third step in the presence of a radical initiator to obtain an N-vinylformamide polymer. A method for producing an N-vinylformamide polymer.