JP2012082441A - Aqueous solution of vinylpyrrolidone-based polymer and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a simple and inexpensive means capable of suppressing the mixing of a gelled substance in powder-like PVP obtained by heating and drying an aqueous solution of PVP obtained by polymerizing a monomer such as N-vinylpyrrolidone or the like in an aqueous medium.SOLUTION: The method for manufacturing the aqueous solution of the vinylpyrrolidone-based polymer includes a step of polymerizing the monomer containing at least N-vinylpyrrolidone in the aqueous medium in the presence of hydrogen peroxide, a metal catalyst and ammonia, a step of adding a nonvolatile organic base in the aqueous solution containing the vinylpyrrolidone-based polymer obtained by the polymerization, and a step of removing the ammonia in the aqueous solution by distilling the nonvolatile organic base-added aqueous solution. The problem to be solved is achieved by the method.

Description

  The present invention relates to a vinylpyrrolidone polymer. Specifically, the present invention relates to a technique for improving the quality of a product to which a vinylpyrrolidone-based polymer is added.

  Vinylpyrrolidone polymers are widely used as additives for various products such as cosmetics, pharmaceuticals, adhesives, paints, dispersants, inks, electronic parts and the like. By adding a vinylpyrrolidone polymer, the biocompatibility, stability, hydrophilicity, etc. of these products can be improved. In addition, a crosslinked product of a vinylpyrrolidone polymer is used as a water-absorbing resin for constituting a paper diaper or the like because it exhibits water absorption and water retention.

  As a method for producing a vinylpyrrolidone-based polymer, for example, a method in which a monomer containing N-vinylpyrrolidone is polymerized in an aqueous medium in the presence of hydrogen peroxide and a base (for example, patents) is known. (Ref. 1 and 2). Such a method is widely used as a method for producing a vinylpyrrolidone polymer because it is highly safe and inexpensive.

  Further, for example, a technique described in Patent Document 3 has been proposed as an improvement of the manufacturing method described in the above-mentioned document. According to the technique described in Patent Document 3, a vinylpyrrolidone-based polymer can be produced at a low temperature and in a short time by employing a copper ammine complex salt as a polymerization initiator. Furthermore, the reaction rate can be further increased by adding ammonia to the reaction system at the start of polymerization.

German Patent No. 922378 JP 62-62804 specification JP 2002-155108 A (particularly claim 3)

  By the way, an aqueous solution (hereinafter also simply referred to as “PVP aqueous solution”) containing a vinylpyrrolidone-based polymer (hereinafter also simply referred to as “PVP”) obtained by the method of Reference 3 can be applied to various uses. For this purpose, it is generally pulverized. For the pulverization, a method of heating and drying the obtained PVP aqueous solution is usually used. By drying the aqueous solution by heating, the solvent is volatilized and powdery PVP is obtained.

  However, when the PVP aqueous solution obtained by the technique described in Document 3 is heated in the pulverization step, a water-insoluble gel-like material is mixed in the obtained powder. It is not preferable to apply the powdery PVP mixed with such a gel-like material to various uses as it is because there is a high possibility of deteriorating the quality of the product. On the other hand, it is difficult to remove the mixed gel-like material after pulverization, and depending on the application, there is a possibility that the gel-like material cannot be used due to the mixing of the gel-like material. Further, even if the gel-like material can be removed, it is preferable to further perform such a removal treatment because it causes an increase in man-hours in the manufacturing process and an increase in cost due to the installation of the treatment apparatus. Absent.

  Therefore, the present invention provides a simple and inexpensive mixture of gel-like substances into powdered PVP obtained by heating and drying a PVP aqueous solution obtained by polymerization of monomers such as N-vinylpyrrolidone in an aqueous medium. It aims at providing the means which can be suppressed by various methods.

  In order to solve the above-mentioned problems, the present inventors diligently searched for the cause of the gel-like material being mixed into the powder.

  As a result, the present inventors have caused the formic acid (HCOOH) produced with the progress of the polymerization reaction and the storage time of the PVP aqueous solution to form a gel-like product by the heat treatment in the powdering process. I found out. In addition, it has also been found that ammonia is required to coexist in an aqueous solution in order to form a gel-like material in the presence of formic acid.

  Therefore, the present inventors can prevent the formation of gel-like substances in the powdering step by suppressing the production of formic acid with the progress of the polymerization reaction and the storage time of the PVP aqueous solution based on the above findings. I found out. Furthermore, the present inventors have found that the formation of a gel-like product can be prevented by reducing the ammonia content in the aqueous PVP solution obtained by polymerization and then performing a pulverization treatment to complete the present invention. It came.

  That is, the present invention is a method for producing an aqueous vinylpyrrolidone-based polymer solution comprising a step of polymerizing a monomer containing at least N-vinylpyrrolidone in an aqueous medium in the presence of hydrogen peroxide, a metal catalyst and ammonia. A method for producing a vinylpyrrolidone-based polymer aqueous solution, wherein a singlet oxygen quencher is present in the reaction system in the polymerization step.

  The present invention also includes a step of polymerizing a monomer containing at least N-vinylpyrrolidone in an aqueous medium in the presence of hydrogen peroxide, a metal catalyst and ammonia, and a vinylpyrrolidone polymer obtained by the polymerization. A method for producing an aqueous vinylpyrrolidone polymer solution, comprising: adding a nonvolatile organic base to an aqueous solution; and distilling the aqueous solution to which the nonvolatile organic base has been added to remove ammonia in the aqueous solution. It is.

  Furthermore, the present invention is a method for storing an aqueous vinylpyrrolidone polymer solution containing a vinylpyrrolidone polymer, formic acid, and ammonia, wherein a singlet oxygen quencher is present in the aqueous solution. This is a method for storing an aqueous vinylpyrrolidone polymer solution.

  According to the present invention, when a PVP aqueous solution is pulverized by heating and drying by a simple and inexpensive method, the problem of mixing a gel-like substance into the obtained PVP is solved. Furthermore, the present invention can improve the quality of products to which PVP is added.

  In the production method of the present invention, a monomer such as N-vinylpyrrolidone is polymerized in an aqueous medium in the presence of hydrogen peroxide, a metal catalyst and ammonia. Thereby, the aqueous solution (PVP aqueous solution) containing a vinylpyrrolidone type polymer (PVP) is obtained.

  As described above, it has been found that formic acid is by-produced during the progress of the polymerization reaction. The formic acid produced as a by-product promotes the formation of a gel-like material when heated in the presence of ammonia in the pulverization step of the PVP aqueous solution. In this invention, the method of suppressing the production | generation of this gel-like substance effectively is provided.

  In addition, although the mechanism by which gel-like substances are generated by heating a PVP aqueous solution containing formic acid and ammonia is not always clear, ammonia is graft-polymerized to the polymer chain of PVP, and the two polymer chains are cross-linked. It has been estimated that a water-insoluble gel is formed. Formic acid is considered to act as a catalyst for promoting the progress of this mechanism. However, such a mechanism is merely speculation, and even if a gel-like material is generated by another mechanism, the technical scope of the present invention is not affected at all.

In the first aspect of the present invention, when a PVP aqueous solution is produced by polymerizing monomers, a singlet oxygen (hereinafter also referred to as “ ¹ Δ _g ”) quencher (hereinafter simply referred to as “quenching agent”) is used in the reaction system. (Also called). Then, the formation of formic acid during the progress of the polymerization reaction can be suppressed. As a result, the formation of a gel-like material in the pulverization process is prevented, which can contribute to the improvement of the quality of the obtained PVP.

Singlet oxygen ( ¹ Δ _g ) is a kind of active oxygen having excited electrons, and in ¹ Δ _g , the spins of two electrons in the π ^* molecular orbital are in opposite directions. The ¹ delta _g from that with an energy higher than the oxygen molecules in the ground state, is highly reactive. ¹ delta _g have electrophilic properties, particularly susceptible to react with the electron-donating large substrates.

The generation of formic acid in the polymerization reaction, ¹ delta _g generated by the decomposition of hydrogen peroxide, electron donating large, peroxide monomer by binding to the double bond of N- vinylpyrrolidone It is presumed that the mechanism is that this peroxide is decomposed to produce formic acid. Therefore, the quenching agent to the reaction system of the polymerization reaction is present, ¹ delta _g generated by the decomposition of hydrogen peroxide is trapped by the quencher, it is considered that the generation of formic acid is prevented. However, as described above, the technical scope of the present invention is not affected by the mechanism.

  In the second aspect of the present invention, ammonia is removed from the PVP aqueous solution by adding a nonvolatile organic base to the PVP aqueous solution obtained in the polymerization stage and distilling it. As described above, since the presence of ammonia is necessary for the production of the gel-like material in the powdering step, the production of the gel-like material in the powdering step is prevented and obtained according to the second aspect of the present invention. The quality of PVP can be improved.

Here, as a technique for removing ammonia from the PVP aqueous solution after the polymerization stage, a technique of simply distilling the PVP aqueous solution to volatilize the ammonia can be considered. If the PVP aqueous solution after the polymerization reaction is simply distilled, a certain amount of ammonia is volatilized, and the ammonia concentration in the aqueous solution can be reduced. However, as the base ammonia volatilizes, the pH of the aqueous solution decreases and the aqueous solution becomes acidic. As the volatilization of ammonia further proceeds, the pH of the aqueous solution moves to the acidic side (pH <7). In the acidic aqueous solution, ammonia no longer exists as a simple substance (NH ₃ ) but as an ion (NH ₄ ⁺ ) combined with a proton (H ⁺ ). This ionic form of ammonia does not volatilize by the distillation operation and remains in the aqueous solution. As a result, the formation of the gel-like material in the powdering process is not sufficiently suppressed, and the problem that the quality of the obtained PVP is still deteriorated remains.

  According to the second aspect of the present invention, such a problem can be solved. That is, by adding a non-volatile organic base, ammonia can be removed by distillation of an aqueous PVP solution without lowering the pH of the aqueous solution.

  As described above, the first and second aspects of the present invention are the same in that the causative substance for the formation of the gel-like material in the powdering step is removed.

  Next, the first aspect of the present invention will be described in detail.

  First, a monomer such as N-vinylpyrrolidone is polymerized in an aqueous medium in the presence of hydrogen peroxide, a metal catalyst and ammonia. Thereby, PVP aqueous solution is obtained.

  In this polymerization step, first, a monomer containing N-vinylpyrrolidone, hydrogen peroxide, a metal catalyst, and ammonia are prepared. Thereafter, a predetermined amount of each prepared component is added to an aqueous medium as a reaction solvent. The first aspect of the present invention is characterized in that a quencher is present in the reaction system in the polymerization stage. Details of the quencher will be described later.

  The monomer contains at least N-vinylpyrrolidone. This monomer undergoes radical polymerization in the polymerization stage to become a vinylpyrrolidone polymer. In the present application, “N-vinylpyrrolidone” means N-vinyl-2-pyrrolidone. The monomer may contain other monomer copolymerizable with N-vinylpyrrolidone, if necessary. Therefore, in the present application, “vinyl pyrrolidone polymer (PVP)” means a copolymer of N-vinyl-2-pyrrolidone and other monomers in addition to a homopolymer of N-vinyl-2-pyrrolidone. It is a concept that also includes

  Examples of monomers copolymerizable with N-vinylpyrrolidone include 1) methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, cyclohexyl (meth) acrylate, (meth) (Meth) acrylic acid esters such as hydroxyethyl acrylate; 2) (meth) acrylamide and derivatives thereof (for example, N-monomethyl (meth) acrylamide, N-monoethyl (meth) acrylamide, N, N-dimethyl (meth)) Acrylamide, etc.); 3) Basic unsaturated monomers such as dimethylaminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylamide, vinylpyridine, vinylimidazole, and salts and quaternized products thereof; 4) Vinylformamide , Vinyl acetamide, vinyl oxazolidone, etc. 5) Carboxyl group-containing unsaturated monomers such as (meth) acrylic acid, itaconic acid, maleic acid and fumaric acid and salts thereof; 6) Unsaturated anhydrides such as maleic anhydride and itaconic anhydride; 7) Vinyl esters such as vinyl acetate and vinyl propionate; 8) Vinyl ethylene carbonate and its derivatives; 9) Styrene and cocoon derivatives; 10) Ethyl (meth) acrylate-2-sulfonate and its derivatives; 11) Vinyl Sulfonic acid and derivatives thereof; 12) vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, and butyl vinyl ether; 13) olefins such as ethylene, propylene, octene, and butadiene; Among these, 1) to 8) can be preferably used from the viewpoint of excellent copolymerizability with N-vinylpyrrolidone. In addition, only 1 type of these monomers may be used independently, and 2 or more types may be used together.

  When other monomers are used as the monomer in addition to N-vinylpyrrolidone, the amount of N-vinylpyrrolidone is not particularly limited. However, from the viewpoint of sufficiently exerting the effects of the present invention, the blending amount of N-vinylpyrrolidone is preferably 60% by mass or more, more preferably 80% by mass or more, based on the total amount of monomers used. More preferably, it is 90 mass% or more.

Hydrogen peroxide is a compound represented by the chemical formula “H ₂ O ₂ ”. This hydrogen peroxide functions as a polymerization initiator for generating radicals necessary for initiation of radical polymerization in the polymerization stage. As described above, hydrogen peroxide, via the generation of singlet oxygen ⁽¹ Δ _g), believed to be involved in by-production of formic acid.

  Hydrogen peroxide may be added to the reaction system in the form of a simple gas at room temperature, or may be added in the form of an aqueous solution (hydrogen peroxide solution).

The metal catalyst has a function of promoting the polymerization of the monomer in the polymerization stage. The specific form of the metal catalyst is not particularly limited, and conventionally known knowledge can be referred to as appropriate. An example of the metal catalyst is a transition metal salt. Specific examples include carboxylates, chlorides, complex salts of transition metals such as copper, iron, cobalt, and nickel. Examples of complex salts include ammine complex salts and aco complex salts. From the viewpoint of excellent catalytic activity, an ammine complex salt of copper is preferably used as the metal catalyst. Examples of copper ammine complex salts include diammine copper salts ([Cu (NH ₃ ) ₂ ] ₂ SO ₄ .H ₂ O, [Cu (NH ₃ ) ₂ ] Cl, etc.), tetraammine copper salts ([Cu (NH ₃ ) ₄ ] SO ₄ .H ₂ O, [Cu (NH ₃ ) ₄ ] Cl _2, etc.). As for these metal catalysts, only 1 type may be used independently and 2 or more types may be used together.

  Ammonia functions as a promoter in the reaction system of the polymerization reaction. That is, when ammonia is included in the reaction system, the progress of the polymerization reaction can be further promoted as compared with the case where ammonia is not included.

  Ammonia may be added to the reaction system in the form of a gaseous simple substance at room temperature, or may be added in the form of an aqueous solution (ammonia water).

  Each component such as a monomer used for the production of PVP can be selected according to the desired form of the PVP to be produced, referring to conventionally known knowledge as appropriate.

  The aqueous medium that is a reaction solvent contains water as a main component. In some cases, the aqueous medium may further contain a solvent other than water that can be dissolved in water. Therefore, the “PVP aqueous solution” produced by the production method of the present invention can include not only a solution containing only water as a solvent, but also a solution containing another solvent that can be used in the polymerization reaction.

  Examples of the solvent other than water that can be contained in the aqueous medium include alcohols such as methanol, ethanol, isopropanol, n-butanol, and diethylene glycol. Among these, the use of an aqueous medium containing isopropanol and / or n-butanol is preferable because the boiling point of water, which is the reaction temperature, is lowered due to the azeotropic effect, and the progress of side reactions can be suppressed. In addition, as for these other solvents, only 1 type may be used independently and 2 or more types may be used together.

  The amount of each component used in the polymerization reaction is not particularly limited and can be adjusted as appropriate. For example, the monomer is about 20 to 60 parts by mass with respect to 100 parts by mass of the aqueous medium, and the hydrogen peroxide is 0.6 to 4.0 parts by mass with respect to the total amount of the monomer (of hydrogen peroxide). (Single conversion), the metal catalyst is about 200 mass ppb (metal atom conversion) with respect to the total amount of the monomer, and the ammonia is about 50 to 4000 mass ppm (a single conversion of ammonia) with respect to the total amount of the monomer. . In some cases, it is a matter of course that the blending amount of each component is out of these ranges.

  The reaction conditions in the polymerization stage are not particularly limited. The reaction temperature is preferably about 55 to 100 ° C. It is preferable to proceed the polymerization reaction at such a temperature because the amount of residual monomer can be reduced. The reaction temperature can be measured using a temperature sensor such as a K thermocouple. Further, the reaction pressure is not particularly limited, and the polymerization reaction may be carried out under any pressure condition under reduced pressure, normal pressure, or increased pressure. Furthermore, the reaction time is not particularly limited as long as the polymerization reaction can proceed sufficiently.

In the first invention, the reaction system of the polymerization step, singlet oxygen ⁽¹ delta _g) quencher (hereinafter, simply referred to as "quencher") be present. When quenching agent to the reaction system is present, by a mechanism described above, the generation of formic acid by ¹ delta _g can be suppressed. Note that the "quencher" as used herein means a substance capable of inactivating the ¹ delta _g by interaction with ¹ delta _g. Specific examples of the quencher include, for example, methionine, α-tocopherol, 1,4-diazobicyclo [2,2,2] octane (DABCO), sodium azide, β-carotene, histidine, tryptophan, superoxide dismutase ( SOD), bilirubin and the like. These quenchers may be used alone or in combination of two or more.

  The presence form of the quencher is not particularly limited, and the effect of the present invention can be obtained if the quencher is present in the reaction system at an arbitrary time from the start point to the end point of the polymerization reaction. Therefore, not only a form in which a quencher is added in advance to the reaction mixture before the start of the polymerization reaction, but also a form in which addition of the quencher is started after the polymerization reaction has progressed to some extent can be employed. Furthermore, the form which adds a quencher sequentially during a polymerization reaction may be employ | adopted. However, from the viewpoint of sufficiently exerting the effects of the present invention, it is preferable that a quencher is present in the reaction system at any point from the start point to the end point of the polymerization reaction.

Abundance of quencher is not particularly limited, the ¹ delta _g produced by the decomposition of hydrogen peroxide from the viewpoint of efficiently deactivated, the abundance of quencher in the reaction system, the total amount 100 mass of the monomers Preferably it is 0.5-2.0 mass parts with respect to a part, More preferably, it is 0.8-1.2 mass part. When the presence of the quencher is too small, it is impossible to sufficiently inactivate ¹ delta _g, there is a possibility that the generation of formic acid is not sufficiently suppressed. On the other hand, if the amount of the quencher present is too large, the polymerization time (the time required from the start to the end of the polymerization) may be extended or the reaction may be stopped in some cases. As a result, the final manufacturing cost may increase.

  In the production method of the present invention, if necessary, other additives may be added to the reaction system of the polymerization reaction. Examples of other additives include a pH adjuster, a chain transfer agent, and a buffer agent. Only one of these other additives may be added to the reaction system alone, or two or more may be added to the reaction system in combination. Further, the amount of these additives added to the reaction system is not particularly limited, and conventionally known knowledge can be appropriately referred to.

  According to the first aspect of the present invention, the content of formic acid in the produced PVP aqueous solution can be reduced by the above-described method. However, after the polymerization step, the obtained PVP aqueous solution is further treated to form formic acid. The content may be further reduced. By further reducing the formic acid content, the formation of a gel-like material in the powdering step can be more reliably prevented. Examples of such treatment include distillation purification treatment. In addition, as described above, it is possible to suppress the formation of a gel-like material in the powdering step by reducing the ammonia content in the aqueous PVP solution. Therefore, in the first of the present invention, after the polymerization step, a treatment for reducing the content of ammonia in the obtained PVP aqueous solution may be performed on the obtained PVP aqueous solution. Examples of such treatment include distillation purification treatment. As the treatment for reducing the ammonia content, the second method of the present invention described later is preferably used.

  According to the first production method of the present invention, an aqueous PVP solution in which the content of formic acid is reduced as compared with the prior art can be produced. That is, the present invention also provides a PVP aqueous solution with a reduced formic acid content. At this time, the content of formic acid in the aqueous PVP solution provided by the present invention is preferably 2000 ppm by mass or less, more preferably 1700 ppm by mass or less, and still more preferably based on the total amount of the vinylpyrrolidone polymer. It is 1500 mass ppm or less, and particularly preferably 1100 mass ppm or less. As described above, formic acid is an impurity that causes generation of a gel-like material, and therefore the smaller the formic acid content in the resulting PVP aqueous solution, the better. However, if the formic acid content is reduced to some extent, the formation of gel-like substances can be prevented. On the other hand, the lower limit of the content of formic acid is not particularly limited, but if the amount of formic acid is to be reduced too much, a large amount of singlet oxygen quencher must be added, resulting in a high manufacturing cost. In addition, the polymerization may be stopped during the polymerization. Therefore, the content of formic acid in the obtained PVP aqueous solution is preferably 100 mass ppm or more, more preferably 300 mass ppm or more, and still more preferably 900 mass ppm or more with respect to the total amount of the vinylpyrrolidone polymer. However, the technical scope of the first production method of the present invention is not limited only to the form of producing an aqueous PVP solution containing such an amount of formic acid. In some cases, an aqueous PVP solution containing an amount of formic acid outside this range may be produced. Further, the technical scope of the PVP aqueous solution of the present invention is not limited only to the form manufactured by the first manufacturing method of the present invention, and in some cases, it was manufactured by another manufacturing method. May be. In addition, as content of formic acid in manufactured PVP aqueous solution, the value measured by the method as described in the Example mentioned later shall be employ | adopted.

Moreover, since the PVP aqueous solution of the present invention employs hydrogen peroxide, which is an inorganic compound, as a polymerization initiator, it should theoretically contain no organic polymerization initiator. However, since contamination as an impurity may be considered in some cases, it is preferable that the obtained PVP aqueous solution does not substantially contain an organic polymerization initiator and / or a decomposition product thereof. In addition, “substantially not containing” means mixing less than the extent of mixing these initiators and their decomposition products into the PVP aqueous solution when an organic polymerization initiator is used as the polymerization initiator for producing the PVP aqueous solution. Means acceptable. Therefore, even if an organic polymerization initiator or a decomposition product thereof is intentionally added to the obtained PVP aqueous solution after the PVP aqueous solution is produced by the production method of the present invention, the PVP aqueous solution before the intentional addition is not subjected to the organic polymerization. So long as it does not substantially contain an initiator and / or a decomposition product thereof, it can be included in the technical scope of the present invention.
Specific examples of the “organic polymerization initiator” include azo compounds and organic peroxides. Examples of the azo compound include 2,2′-azobis (2-amidinopropane) dihydrochloride, azobis-2-methylpropionamidine hydrochloride, 2,2′-azobisisobutyronitrile, and dimethyl-2. 2,2′-azobis-2-methylpropionate, 2,2′-azobis-2-methylbutyronitrile, 2,2′-azobis-2,4-dimethylvaleronitrile, 2,2′-azobis-2 -(2-imidazolin-2-yl) propanedihydrochloride and the like are exemplified. Examples of organic peroxides include benzoyl peroxide, lauroyl peroxide, cumene hydroperoxide, t-butyl hydroperoxide, isobutyryl hydroperoxide, di-t-butyl hydroperoxide, and cyclohexanone. Peroxide, dicumyl peroxide, t-butyl cumyl peroxide, di-t-hexyl peroxide, t-butyl peroxypivalate, dibenzoyl peroxide and the like can be mentioned. However, the organic polymerization initiator is not limited to the compounds listed above.

  In addition, as an “decomposition product of an organic polymerization initiator”, a decomposition product of an azo compound generally has a structure represented by the following chemical formula:

  In the formula, R1, R2 and R3 each independently represent a nitrile group, an alkyl group, an ester group, an aryl group, an amino group, an imino group, an amide group, an alkoxyl group, an amidino group or an imidazole ring.

  Moreover, the decomposition product of the organic peroxide generally has a structure such as R1-OH, R1-O-R2, R1-H, R1-C (= O) -OH. Here, R1 and R2 have the same definition as described above. However, the decomposition product of the organic polymerization initiator is not limited to the compounds listed above.

  Next, the second aspect of the present invention will be described in detail.

  In the second of the present invention, after completion of the polymerization step, a non-volatile organic base is added to the obtained aqueous PVP solution and distilled. Thereby, ammonia is removed from the PVP aqueous solution by the mechanism described above, and a PVP aqueous solution in which the ammonia content is reduced is obtained. As a result, the formation of a gel-like material in the pulverization process can be prevented, and the quality of the obtained PVP can be improved.

  First, a monomer such as N-vinylpyrrolidone is polymerized in an aqueous medium in the presence of hydrogen peroxide, a metal catalyst and ammonia. Thereby, PVP aqueous solution is obtained. The polymerization stage of N-vinylpyrrolidone is the same as in the first aspect of the present invention except that a quencher is present in the reaction system. Therefore, detailed description is omitted here.

  In the second aspect of the present invention, a nonvolatile organic base is added to an aqueous PVP solution obtained by polymerization. The PVP aqueous solution to which the base has been added is distilled in the distillation step described later.

  In the present application, the “nonvolatile organic base” means an organic base that does not substantially volatilize in an aqueous medium when heated to the boiling point of the aqueous medium. Specific examples of the non-volatile organic base include quaternary ammonium salts and guanidine salts. Furthermore, examples of the quaternary ammonium salt include halides (eg, bromide, fluoride, chloride, iodide) such as tetramethylammonium, tetraethylammonium, tetrapropylammonium and tetrabutylammonium, and guanidine salts. Examples thereof include guanidine carbonate. These non-volatile organic bases may be used alone or in combination of two or more.

  The nonvolatile organic base may be added to the PVP aqueous solution as it is, or may be added to the PVP aqueous solution in the form of a solution dissolved in an appropriate solvent. When added in the form of a solution, a solvent that can be used as an aqueous medium in the first polymerization step of the present invention can be used as the solvent of the solution.

  The addition amount of the non-volatile organic base is not particularly limited, and can be appropriately adjusted in consideration of the ammonia content in the aqueous PVP solution and the distillation conditions in the distillation stage described later. At this time, the non-volatile organic base is preferably added so that the pH of the aqueous PVP solution is 8 or more. If the pH of the aqueous PVP solution after the addition of the base is too low, ammonia may not be sufficiently removed in the distillation stage described later. On the other hand, if the pH of the aqueous PVP solution is 8 or more, even if a base is further added, the effect is not particularly improved, and the production cost may increase.

  Subsequently, the PVP aqueous solution to which the nonvolatile organic base is added is distilled. Thereby, ammonia in PVP aqueous solution volatilizes and the content of ammonia in PVP aqueous solution can be reduced.

  Distillation conditions (eg, temperature, pressure, time, etc.) in the distillation stage are not particularly limited, and conventionally known knowledge about distillation purification of an aqueous PVP solution can be appropriately referred to.

  According to the second aspect of the present invention, an aqueous PVP solution having a reduced ammonia content is obtained by the above-described method. After the distillation step, the obtained aqueous PVP solution is further treated to contain ammonia. The amount may be further reduced. By further reducing the ammonia content, the formation of a gel-like material in the powdering process can be more reliably prevented.

  According to the second production method of the present invention, an aqueous PVP solution in which the ammonia content is reduced as compared with the prior art can be produced. Therefore, the ammonia content in the aqueous PVP solution produced by the second production method of the present invention is preferably 800 ppm by mass or less, more preferably 600 ppm by mass or less, based on the total amount of the vinylpyrrolidone polymer. is there. However, the second technical scope of the present invention is not limited only to the form of producing an aqueous PVP solution containing such an amount of ammonia, and in some cases, it contains an amount of ammonia outside this range. An aqueous PVP solution may be produced. In addition, as content of ammonia in manufactured PVP aqueous solution, the value measured by the method as described in the Example mentioned later shall be employ | adopted.

  It is also possible to use the first and second of the present invention in combination. For example, in the polymerization stage of a monomer such as N-vinylpyrrolidone, a singlet oxygen quencher is present in the reaction system to produce an aqueous PVP solution with a reduced formic acid content (first of the present invention). Then, a nonvolatile organic base is added to the obtained PVP aqueous solution and distilled to remove ammonia (second invention). Thereby, the PVP aqueous solution with which content of both formic acid and ammonia was reduced can be manufactured.

  As mentioned above, although the manufacturing method of PVP aqueous solution was demonstrated as 1st and 2nd of this invention, this application utilizes addition of the singlet oxygen quencher which is the 1st characteristic of this invention as 3rd of this invention. A method for storing an aqueous PVP solution is also provided.

As described above, in the polymerization stage, through the generation of ¹ delta _g, formic acid is causative agent of gels resulting product. This production of formic acid proceeds slightly even when the PVP aqueous solution is stored after the polymerization stage. The third aspect of the present invention prevents the formation of gel-like substances by suppressing the formation of formic acid in this storage stage.

  That is, the third aspect of the present invention is a method for storing an aqueous vinylpyrrolidone polymer solution containing a vinylpyrrolidone polymer, formic acid, and ammonia, wherein a singlet oxygen quencher is present in the aqueous solution. This is a method for storing a vinylpyrrolidone polymer aqueous solution.

  The PVP aqueous solution used in the third storage method of the present invention contains a vinyl pyrrolidone polymer, formic acid, and ammonia. The specific form of the PVP aqueous solution is not particularly limited, but preferably, the PVP aqueous solution obtained in the polymerization step of the first or second production method of the present invention is used. Since the specific form of such an aqueous PVP solution is as described above, detailed description thereof is omitted here.

  In the third aspect of the present invention, the PVP aqueous solution is stored in the presence of a quencher. Thereby, the production | generation of formic acid is suppressed by the mechanism similar to the 1st of this invention, and the increase in content of formic acid in the aqueous solution in the storage stage of PVP aqueous solution is prevented. As a result, the formation of a gel-like material in the pulverization process can be prevented, and the quality of the obtained PVP can be improved.

  Since the specific form of the quencher used in the present storage method is also as described in the first aspect of the present invention, detailed description is omitted here.

  There is no particular limitation on the form of the quencher, and the effect of the present invention can be obtained if the quencher is present in the reaction system at any time from the start to the end of storage. Accordingly, not only a form in which a quencher is added in advance to the PVP aqueous solution immediately after the polymerization stage is completed, but also a form in which addition of the quencher is started after a certain storage time has elapsed. Furthermore, the form which adds a quencher sequentially during storage may be employ | adopted. However, from the viewpoint of sufficiently exerting the effects of the present invention, any time point from the start point of storage (end point of the polymerization stage) to the end point of storage (for example, the time point used for spray drying described later) Also, it is preferable that a quencher is present in the PVP aqueous solution.

It is not particularly limited abundance quencher, from the viewpoint of deactivating the ¹ delta _g to produce efficiently by decomposition of hydrogen peroxide, the abundance of quencher in aqueous PVP solution had a nonvolatile content in the aqueous PVP solution ( The solid content is preferably 0.1 to 5.0 parts by mass, more preferably 0.3 to 2.0 parts by mass, and still more preferably 0.5 to 1.5 parts by mass with respect to 100 parts by mass. When the presence of the quencher is too small, it is impossible to sufficiently inactivate ¹ delta _g, there is a possibility that the generation of formic acid is not sufficiently suppressed. On the other hand, even if the amount of the quencher present is too large, there is no particular problem from the viewpoint of the effect of inhibiting the formation of formic acid, but there is a possibility that the manufacturing cost will increase.

  The third storage method of the present invention may be combined with the first and / or second manufacturing method of the present invention.

  For example, when it is assumed that the PVP aqueous solution is stored using the third storage method of the present invention, the PVP aqueous solution is manufactured by the first manufacturing method of the present invention, and the third storage method of the present invention is used as it is. It is convenient to store the PVP aqueous solution by. In the case of adopting such a form, it is preferable to adjust the amount of the quencher present in the reaction system in the polymerization stage of the first production method of the present invention in consideration of the storage period.

  In order to combine the third storage method of the present invention with the second production method of the present invention, an aqueous PVP solution at any time before the start of storage, during storage, or after storage according to the third of the present invention. A non-volatile base is added therein, and the aqueous solution is distilled at a desired point in time to remove ammonia (second aspect of the present invention).

  The produced PVP aqueous solution is pulverized by heat drying. Powdered PVP is produced by pulverization. The powdery PVP can be used as an additive for various applications described later.

  As described above, when formic acid and ammonia coexist when the PVP aqueous solution is heated and dried to form powder, a gel-like product is generated by cross-linking of the PVP chains and mixed into the obtained powder. On the other hand, in the PVP aqueous solution produced by the production method of the present invention described above, the content of formic acid and / or ammonia is reduced. Therefore, according to this invention, the production | generation of the gel-like substance in a powdering process is prevented.

  The specific method of heat drying is not particularly limited, and conventionally known knowledge can be appropriately referred to in the field of pulverization of the polymer solution. An example of the heat drying means is a spray drying method. However, in some cases, the PVP aqueous solution may be powdered by other means. Examples of other heat drying means include a spray drying method, a drum dryer drying method, a fluidized bed drying method, and a belt drying method.

  Moreover, the temperature conditions at the time of heat-drying are about 100-200 degreeC normally, Preferably it is 100-150 degreeC. However, it goes without saying that heat drying may be performed under temperature conditions outside this range.

  The average particle diameter of the powdery PVP obtained by pulverization is not particularly limited, and can be appropriately set according to a desired application to be added as an additive.

  If necessary, the particle size of the PVP may be controlled by subjecting the powdery PVP obtained in the powdering step by heat drying to further pulverization or granulation.

  The use of the powdery PVP obtained by the pulverization process is not particularly limited. For example, cosmetics, pharmaceuticals (including intermediates for medicines and agricultural chemicals), dispersants, foods, photosensitive electronic materials, and tackifiers. In addition to these additives, additives used in the production of filtration membranes (for example, hollow filtration membranes), and the like, they can also be used in conventionally known applications as described in JP-A-11-71414.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail using an Example and a comparative example, the technical scope of this invention is not necessarily restrict | limited only to the following form.

Example 1
Copper sulfate (0.00023 parts by mass) as a metal catalyst, water (350 parts by mass) and methionine (4.5 parts by mass) as a singlet oxygen quencher were charged into a reaction vessel, and the temperature was raised to 80 ° C. Next, while maintaining 80 ° C., monomers N-vinylpyrrolidone (450 parts by mass), 25% aqueous ammonia (3.6 parts by mass), 30% aqueous hydrogen peroxide (16.5 parts by mass) and Water (74.9 parts by mass) was added dropwise over 180 minutes. After completion of the dropwise addition, 30% hydrogen peroxide solution (2.7 parts by mass) was added equally in 3 portions at 1.5 hour intervals, and after the third addition, maintained at 80 ° C. for 1 hour, A polyvinylpyrrolidone aqueous solution was obtained. When the physical properties of the obtained aqueous polyvinylpyrrolidone solution were measured, the concentration was 50% by mass and the K value was 28. Furthermore, the content of formic acid and ammonia with respect to the total amount of polyvinylpyrrolidone in the obtained aqueous solution of polyvinylpyrrolidone was measured. The measurement results are shown in Table 1 below. The contents of formic acid and ammonia were measured by the following method.

<Method for measuring formic acid content>
The amount of formic acid in the aqueous polyvinylpyrrolidone solution obtained was ion chromatograph (Nippon Dionex Co., Ltd., “ion chromatograph system DX-500”, formic acid analysis column: ICE-AS1, eluent: 0.5 mM octanesulfonic acid. , Flow rate: 1.0 mL / min), and the formic acid content was calculated as mass ppm relative to the total amount of polyvinylpyrrolidone in the aqueous solution calculated separately.

<Measurement method of ammonia content>
The amount of ammonia in the aqueous polyvinylpyrrolidone solution obtained was ion chromatograph (Nippon Dionex Co., Ltd., “ion chromatograph system DX-500”, ammonia analysis column: IonpacCS3, eluent: 25 mM HCl / 0.1 mM diamino. Ammonia content was calculated as mass ppm with respect to the total amount of polyvinylpyrrolidone in the aqueous solution calculated separately using propionic acid / monohydrochloride, flow rate: 1.0 mL / min.

  10 g of the obtained aqueous polyvinylpyrrolidone solution was heated at 150 ° C. for 1 hour using an oven (“PH-100” manufactured by ESPEC Corporation) to obtain 5 g of a dried polyvinylpyrrolidone product. The following performance evaluation was performed using the obtained dried polyvinylpyrrolidone.

  5 g of the obtained dried polyvinylpyrrolidone was further heated at 150 ° C. for 2 hours, and then 45 g of water was added to prepare a 10 mass% aqueous solution. The presence of the gel-like substance in this aqueous solution was visually observed. The observation results are shown in Table 1 below.

Example 2
Copper sulfate (0.00023 parts by mass) and water (350 parts by mass) were charged into a reaction vessel, and the temperature was raised to 80 ° C. Next, while maintaining 80 ° C., N-vinylpyrrolidone (450 parts by mass), 25% aqueous ammonia (3.6 parts by mass), 30% hydrogen peroxide (16.5 parts by mass) and water (74.9) Parts by mass) were added dropwise over 180 minutes. After completion of the dropwise addition, 30% hydrogen peroxide solution (2.7 parts by mass) was added equally in 3 portions at 1.5 hour intervals, and after the third addition, maintained at 80 ° C. for 1 hour, A polyvinylpyrrolidone aqueous solution was obtained. When the physical properties of the obtained aqueous polyvinylpyrrolidone solution were measured, the concentration was 50% by mass, the K value was 28, and the pH was 4.3. The pH of the obtained aqueous polyvinylpyrrolidone solution was adjusted by adding guanidine carbonate, which is a non-volatile base, to pH 8 or higher, and then ammonia was removed by distillation. By the same method as in Example 1, the contents of formic acid and ammonia with respect to the total amount of polyvinylpyrrolidone in the obtained aqueous solution of polyvinylpyrrolidone were measured. The measurement results are shown in Table 1 below.

  Using the polyvinyl pyrrolidone aqueous solution after removing ammonia, a polyvinyl pyrrolodon dried product was obtained in the same manner as in Example 1 above, and re-solubility was evaluated. The observation results are shown in Table 1 below.

Example 3
Copper sulfate (0.00023 parts by mass), water (350 parts by mass) and methionine (4.5 parts by mass) were charged into a reaction vessel, and the temperature was raised to 80 ° C. Next, while maintaining 80 ° C., N-vinylpyrrolidone (450 parts by mass), 25% aqueous ammonia (3.6 parts by mass), 30% hydrogen peroxide (16.5 parts by mass) and water (74.9) Parts by mass) were added dropwise over 180 minutes. After completion of the dropwise addition, 30% hydrogen peroxide solution (2.7 parts by mass) was added equally in 3 portions at 1.5 hour intervals, and after the third addition, maintained at 80 ° C. for 1 hour, A polyvinylpyrrolidone aqueous solution was obtained. When the physical properties of the obtained aqueous polyvinylpyrrolidone solution were measured, the concentration was 50% by mass, the K value was 28, and the pH was 4.3. The pH of the aqueous polyvinylpyrrolidone solution obtained was adjusted until the pH reached 8 or more by adding guanidine carbonate, and then ammonia was removed by distillation. By the same method as in Example 1, the contents of formic acid and ammonia with respect to the total amount of polyvinylpyrrolidone in the obtained aqueous solution of polyvinylpyrrolidone were measured. The measurement results are shown in Table 1 below.

  Using the polyvinyl pyrrolidone aqueous solution after removing ammonia, a polyvinyl pyrrolodon dried product was obtained in the same manner as in Example 1 above, and re-solubility was evaluated. The observation results are shown in Table 1 below.

Comparative Example Copper sulfate (0.00023 parts by mass) and water (350 parts by mass) were charged into a reaction vessel and heated to 80 ° C. Next, while maintaining 80 ° C., N-vinylpyrrolidone (450 parts by mass), 25% aqueous ammonia (3.6 parts by mass), 30% hydrogen peroxide (16.5 parts by mass) and water (74.9) Parts by mass) were added dropwise over 180 minutes. After completion of the dropwise addition, 30% hydrogen peroxide solution (2.7 parts by mass) was added equally in 3 portions at 1.5 hour intervals, and after the third addition, maintained at 80 ° C. for 1 hour, A polyvinylpyrrolidone aqueous solution was obtained. When the physical properties of the obtained aqueous polyvinylpyrrolidone solution were measured, the concentration was 50% by mass and the K value was 28. By the same method as in Example 1, the contents of formic acid and ammonia with respect to the total amount of polyvinylpyrrolidone in the obtained aqueous solution of polyvinylpyrrolidone were measured. The measurement results are shown in Table 1 below.

  Using the obtained polyvinyl pyrrolidone aqueous solution, a dried polyvinyl pyrrolodon was obtained by the same method as in Example 1 above, and the re-solubility was evaluated. The observation results are shown in Table 1 below.

  From the results shown in Table 1, it is suggested that the presence of a singlet oxygen quencher in the reaction system during the production of the PVP aqueous solution suppresses the generation of formic acid during polymerization. Moreover, it is suggested that the ammonia in PVP aqueous solution is efficiently removed by adding and distilling a non-volatile base to PVP aqueous solution after superposition | polymerization. And it is shown that generation | occurrence | production of the gel-like substance at the time of drying of PVP aqueous solution is prevented effectively by reduction of these formic acid and / or ammonia content.

  Therefore, according to this invention, mixing of the gel-like substance to the PVP dry matter obtained by heat drying of PVP aqueous solution can be suppressed by a simple and cheap method.

Claims (2)

Polymerizing a monomer comprising at least N-vinylpyrrolidone in an aqueous medium in the presence of hydrogen peroxide, a metal catalyst and ammonia;
Adding a non-volatile organic base to an aqueous solution containing a vinylpyrrolidone-based polymer obtained by polymerization;
Distilling the aqueous solution to which the non-volatile organic base has been added to remove ammonia in the aqueous solution;
A method for producing a vinylpyrrolidone-based polymer aqueous solution.   The production method according to claim 2, wherein the nonvolatile organic base is a quaternary ammonium salt and / or a guanidine salt.