JP2014043538A - Method for producing water-soluble polymer, and water-soluble polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for efficiently producing a water-soluble polymer having excellent workability when dissolving in an aqueous solvent, allowing easy preparation of an aqueous solution with high viscosity, and sufficiently reducing amounts of residual monomers and water-insoluble parts.SOLUTION: When polymerizing a monomer aqueous solution including polymerizable unsaturated monomers by a continuous-system belt polymerization machine, at least part of an area between inputting the monomer aqueous solution on a belt and starting polymerization is heated to a temperature over 40°C using heating means.

Description

  The present invention relates to a method for producing a water-soluble polymer, and a water-soluble polymer obtained thereby. More specifically, it is a water-soluble polymer that can be used as a raw material for various industrial products such as thickeners and flocculants and cataplasms in the pharmaceutical field, and a method for producing the same. The present invention relates to a water-soluble polymer that is excellent in workability at the time and has a sufficiently reduced amount of residual monomer and water-insoluble matter, and a method that can efficiently produce the polymer.

  High molecular weight homopolymers or copolymers having (meth) acrylate as the main monomer are widely used as thickeners, pressure-sensitive adhesives, flocculants and the like. Also in the pharmaceutical field, it is used as an additive or hydrophilic ointment base for the purpose of improving the adhesiveness and water retention of poultices and poultices, and some are used as food additives. In these fields, in particular, there is a concern that the remaining monomers and harmful metals may adversely affect the living body, so that it is required to reduce their amounts as much as possible. In addition, it is required to have a small amount of insoluble matter and to have excellent solubility in water and workability at the time of dissolution, but it has been difficult to produce a polymer that simultaneously satisfies these physical property values.

  By the way, as a polymerization method for producing these water-soluble polymers, a bulk polymerization method, a suspension polymerization method, an emulsion polymerization method, a slurry polymerization method, an aqueous solution polymerization method and the like are generally mentioned. Among these, a water-soluble polymerizable monomer represented by (meth) acrylic acid (salt) (hereinafter also referred to as “(meth) acrylic acid and / or a salt thereof”) monomer as a monomer. When a saturated monomer is a main component, the most widely used is an aqueous solution polymerization method. That is, according to the aqueous solution polymerization method, a known radical polymerization initiator is added to an aqueous solution of a polymerizable monomer and heated appropriately (called thermal polymerization) if necessary, or light having a wavelength in the near ultraviolet to ultraviolet region is used. By irradiation (referred to as photopolymerization), the polymer is obtained as a hydrogel. This water-containing gel-like polymer can be made into a powder by finely granulating using a crusher, an extruder, a cutter, a kneader, etc., followed by drying and pulverization. Since this powder is easily re-dissolved when added to water, it can be used as a thickener, an adhesive, an aggregating agent, or the like.

  Various methods for producing water-soluble polymers by such aqueous solution polymerization methods have been proposed. For example, in Patent Document 1, a solution containing sodium acrylate as a monomer is polymerized by irradiating ultraviolet rays on a belt polymerization machine, or by heating from the outside in a mold-type casting polymerization machine. A method for producing a high molecular weight acrylic water-soluble polymer with a sufficiently reduced insoluble content is obtained by extruding the water-containing gel thus obtained with a specific power of 0.06 to 0.14 kwh / kg. It is disclosed. Moreover, in patent document 2, while making the pH of the polymerization liquid containing a monomer component into 7-14, the belt surface uses a stainless steel belt polymerization machine, the gel thickness is 8-50 mm, and the polymerization peak temperature is 85 ° C. A method for producing a low-adhesive (meth) acrylic acid (salt) -based water-soluble polymer hydrated gel by performing polymerization under the following control is disclosed.

Japanese Patent Laid-Open No. 2007-112946 JP 2009-19181 A

  A water-soluble polymer obtained by a conventionally studied method as described above usually exhibits a high aqueous solution viscosity. Such a water-soluble polymer is generally known to have a thickening action and an aggregating action that improve as the degree of polymerization increases, that is, as the molecular weight increases. In particular, branching and crosslinking reactions occur in the polymer in the latter half of the period or in the drying process, resulting in a decrease in water solubility or formation of insoluble matter. Workability and performance may be insufficient.

  In addition, when dissolving a water-soluble polymer in water, a method in which the polymer is gradually added and dissolved while stirring an aqueous solvent is generally used. In this case, the water-soluble polymer obtained by the conventional method as described above is used. When a water-soluble polymer is used, as the viscosity of the aqueous solution increases as the polymer dissolves, the liquid surface tends to lift up while being wound around the stirring shaft (so-called the Weisenberg phenomenon or the Weisenberg effect). Turned out to be. If the Weisenberg phenomenon of the aqueous solution is high, if the stirring speed is increased to increase the dissolution rate or dissolution amount, the amount of wrapping around the shaft will increase further. On the contrary, the dissolution efficiency decreases. In addition, since a large amount of dirt is generated in the apparatus due to the solution adhering to the seal portion of the shaft, the manufacturing cost may increase due to an increase in the frequency of cleaning operations.

  Moreover, in many of the water-soluble polymers obtained by conventional methods, the aqueous solution generally tends to exhibit high thixotropic properties. The higher the thixotropy of the aqueous solution, the higher the shear force applied, the lower the viscosity and the easier it will be to handle, but the shear force is weak or when left standing, the viscosity is high and the fluidity is poor. It may be difficult to work.

  Therefore, the present invention can sufficiently improve the workability at the time of dissolution while the desired aqueous solution viscosity is sufficiently expressed and the Weisenberg phenomenon that occurs during dissolution in an aqueous solvent can be greatly reduced. An object of the present invention is to provide a high-molecular-weight water-soluble polymer which can greatly reduce the thixotropic property and improve the handling workability of the aqueous solution after dissolution, and at the same time satisfy at least these contradictory physical properties. Another object of the present invention is to provide a method for efficiently producing a water-soluble polymer that satisfies the above physical property values and has a sufficiently reduced amount of residual monomer and water-insoluble matter. .

  In order to solve the above-mentioned problems, the present inventors have conducted intensive studies. As a result, when the aqueous monomer solution is polymerized with a continuous belt polymerization machine, the polymerization starts after the aqueous monomer solution is charged onto the belt. Surprisingly, by heating at least a part of the region until it is heated to a specific temperature, the Weisenberg phenomenon when the obtained polymer is dissolved in water, and the thixotropic property of the aqueous solution after dissolution In addition, it has been found that the polymer obtained by the conventional method such as Patent Documents 1 and 2 can be greatly reduced compared to the case of using the polymer obtained by the conventional method, and that the viscosity of the aqueous solution after dissolution is as high as that of the conventional method. The headline and the present invention were completed.

  That is, the present invention is a method for producing a water-soluble polymer comprising a step of polymerizing a monomer aqueous solution containing a polymerizable unsaturated monomer with a continuous belt polymerizer, Among the polymerization regions starting from the above, at least part of the region from the charging point of the monomer aqueous solution to the polymerization start point is heated to a temperature exceeding 40 ° C. using a heating means.

  In the present invention, in the polymerization region starting from the charging point of the monomer aqueous solution, it is preferable to heat the region from the starting point to at least 50%. By setting such a region to 50% or more of the total polymerization region, the polymerization reaction is easily stabilized, and a water-soluble polymer can be efficiently produced as the polymerization time is shortened.

  In the present invention, it is preferable that heating using the heating means is performed at the lower part of the belt. By doing in this way, the water-soluble polymer which transferred heat more uniformly with respect to monomer aqueous solution from the heat source, and was stable in quality can be manufactured continuously.

  Furthermore, in the present invention, the monomer aqueous solution preferably has a pH of 11.0 to 13.0. According to the findings from the study of the present inventor, as will be described later, when the pH exceeds the range, that is, when the pH is less than 11.0 or more than 13.0, the polymerization is delayed and the desired physical properties are obtained. There is a possibility that the polymer may not be obtained.

  Further, in the present invention, a water-soluble polymer having a 0.2 mass% aqueous solution viscosity of 500 mPa · s or more, a Weisenberg value of 10 mm or less and / or a thixotropy value of 50 or less is obtained by the above production method. Can be provided. By satisfying the above range, it is excellent in workability when preparing an aqueous solution by dissolving in an aqueous solvent, despite having high viscosity, and the solution after dissolution can be easily handled. It can be used suitably for a use.

  According to the present invention, the workability when dissolving in an aqueous solvent is excellent, a high-viscosity aqueous solution can be easily prepared, and the amount of residual monomer and water-insoluble matter is sufficiently reduced. A water-soluble polymer can be produced efficiently.

  Since the water-soluble polymer (for example, acrylate-based water-soluble polymer) obtained by the production method of the present invention is such a high quality, it is used for pharmaceuticals, paints, civil engineering / architecture, etc. In general industrial use, it can be suitably used in various fields as a thickener, an adhesive, a flocculant, a hygroscopic agent, a desiccant, a surface modifier and the like. Furthermore, as a thickener and a loosening accelerator that require higher quality in terms of viscosity and residual monomer amount, etc., it is suitable for food additives for food and feed, feed additives, etc. Can be used.

It is process drawing which shows the suitable form of the manufacturing method of this invention. It is a side surface conceptual diagram which shows the one aspect | mode of the belt polymerization machine used with the manufacturing method of this invention. It is the schematic which shows the superposition | polymerization area | region of this invention.

  Hereinafter, the present invention will be described in detail.

  The production method according to the water-soluble polymer of the present invention preferably includes these steps in the order of polymerization, extrusion, drying, pulverization, and classification, and the water-soluble polymer thus produced is a dry powder. Since it is obtained as a body form, it is preferable in terms of handling workability when used for various purposes. Among the steps in the production method of such a water-soluble polymer, in the production method of the present invention, in particular, a step of polymerizing a monomer aqueous solution containing a polymerizable unsaturated monomer with a continuous belt polymerization machine. In the method, at least a specific region of the polymerization region starting from the charging point of the monomer aqueous solution is heated to a specific temperature. More specifically, it is characterized in that at least a part of the region from the charging point of the monomer aqueous solution to the polymerization starting point is heated to a temperature exceeding 40 ° C. using a heating means. By passing through such a polymerization step, it becomes possible not only to continuously and efficiently produce a polymer, but also to obtain a water-soluble polymer that can solve the above-mentioned problems. it can.

(1) Monomer The advantageous polymer obtained by the method of the present invention is obtained by polymerizing an aqueous monomer solution containing a polymerizable unsaturated monomer as an essential component, preferably water-soluble polymerizable. It is a water-soluble polymer obtained by polymerizing an aqueous monomer solution containing an unsaturated monomer as an essential component.

  In the present invention, a polymerizable unsaturated monomer is essentially used as a monomer. Among these monomers, if a polymerizable unsaturated monomer containing an acid group is an essential component, a large osmotic pressure is expressed due to the dissociation of the acid group. It is preferable because it is excellent. Although it does not specifically limit as an acid group prescribed | regulated by this invention, A carboxyl group, a sulfonic acid group, a phosphoric acid group etc. are mentioned.

  These acid group-containing unsaturated monomers are preferably monomers containing an acid group among monomers having an unsaturated double bond (ethylenically unsaturated monomer). Specifically, (meth) acrylic acid, maleic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, 2- (meth) acryloylethanesulfonic acid, 2- (meth) acryloylpropanesulfonic acid, 2- ( (Meth) acrylamido-2-methylpropanesulfonic acid, vinylsulfonic acid, styrenesulfonic acid and / or a salt thereof. One of these monomers may be used alone, or two or more may be used. You may use together. Among them, (meth) acrylic acid, 2- (meth) acrylamido-2-methylpropanesulfonic acid and / or a salt thereof are preferable from the viewpoint of water performance and water absorption characteristics, and (meth) acrylic acid and / or a salt thereof is preferable. Further preferred is acrylic acid and / or a salt thereof. That is, the polymer obtained in the present invention includes a poly (meth) acrylic acid (salt) -based polymer obtained by polymerizing a monomer having a (meth) acrylic acid (salt) -based monomer as an essential component. A polyacrylic acid (salt) polymer obtained by polymerizing a monomer having an acrylic acid (salt) monomer as an essential component is particularly preferred.

  Further, in the repeating unit, (meth) acrylic acid and / or a salt thereof as a monomer is preferably 30 mol% or more, more preferably 50 mol% or more, further preferably 60 mol% or more, and even more. It is preferably 70 mol% or more, particularly preferably 80 mol% or more, and most preferably (meth) acrylic acid and / or a salt thereof to 100 mol%.

  In obtaining the polymer of the present invention, it is preferable to contain (meth) acrylic acid (salt) in all the monomer components. In this case, other components other than (meth) acrylic acid (salt) are preferable. The saturated monomer is preferably used in an amount of 70 mol% or less, more preferably 40 mol% or less, and still more preferably 20 mol% or less. Specific examples of the copolymerizable monomer that can be contained as necessary include (anhydrous) carboxyl group-containing polymerizable monomers such as maleic acid, fumaric acid, crotonic acid, and itaconic acid; vinyl sulfonic acid, Sulfonic acid groups such as methallylsulfonic acid, allylsulfonic acid, 2- (meth) acrylamide-2-methylpropanesulfonic acid, (meth) acryloxyalkanesulfonic acid, 3- (meth) allyloxy-2-hydroxypropanesulfonic acid Containing polymerizable monomer; N-vinyl-2-pyrrolidone; N-vinylacetamide, (meth) acrylamide, N-isopropyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, tertiary butyl (meth) Amide monomers such as acrylamide; allyl alcohol, 2-hydroxyethyl (meth) acrylate , Hydrophilic unsaturated monomers such as methoxypolyethylene glycol (meth) acrylate, polyethylene glycol (meth) acrylate, 3-methyl-3-buten-1-ol (isoprenol), glycerol mono (meth) acrylate, and the like Nitrile monomers such as acrylonitrile; hydrophobic monomers such as methyl (meth) acrylate, ethyl (meth) acrylate, vinyl acetate, styrene, etc., including two or more if necessary It may be a thing. In the case of producing a water-soluble polymer, among these copolymerizable monomers, a hydrophobic monomer tends to inhibit the water-solubility of the polymer. A polymerizable monomer is preferably used, and among them, carboxyl group-containing polymerizable monomers such as (anhydrous) maleic acid, fumaric acid, crotonic acid, itaconic acid and the like are particularly preferable.

  The acid group of the monomer may be unneutralized (that is, the neutralization rate or degree of neutralization is 0 mol%), and may be neutralized with a monovalent and / or divalent or higher cation. However, it is preferably neutralized as a monovalent salt. The neutralization rate is preferably 80 to 105 mol%, more preferably 90 to 103 mol%, and still more preferably 95 to 101 mol%. Here, the neutralization rate is the content ratio of the neutralized group when the sum of the acid group of the polymer and the neutralized group is 100 mol%.

  The group in the neutralized form is a group in which a dissociable hydrogen ion in an acid group is substituted with another cation. Therefore, for example, the monomer component forming the acrylic acid (salt) polymer contains x mol of acrylic acid, y mol of sodium acrylate as a salt of acrylic acid, and n mol of nonionic monomer. Is completely polymerized, the nonionic monomer is not ionic and is not in a neutralized form, so the degree of neutralization is determined by the following formula.

上記式において、分母はアクリル酸（塩）系重合体の製造に使用した酸基量と中和された形態の基量とのモル数としての和である。分子は中和された形態の基量と中和点を越えて存在する余剰のカチオンとのモル数としての和である。上記式により中和度（中和された形態の基の含有割合）をモル％として得ることができる。

In the above formula, the denominator is the sum as the number of moles of the acid group amount used in the production of the acrylic acid (salt) polymer and the neutralized base amount. The molecule is the sum of the neutralized form base weight and the excess cation present beyond the neutralization point in moles. According to the above formula, the degree of neutralization (the content ratio of the neutralized group) can be obtained as mol%.

  Preferred monovalent salts include alkali metal salts, ammonium salts and amine salts. More preferred are sodium salt, potassium salt, lithium salt and ammonium salt. Particularly preferred is a sodium salt.

  The basic substance used for neutralization is not particularly limited, but includes alkali metal hydroxides such as sodium hydroxide, potassium hydroxide and lithium hydroxide, sodium carbonate (hydrogen), potassium carbonate (hydrogen) and the like. Monovalent basic substances such as carbonic acid (hydrogen) salt and ammonia are preferred, and sodium hydroxide is particularly preferred.

  The neutralization may be performed by adding a basic substance to the polymer after polymerization (hydrogel polymer), and in the form of a salt as a monomer when preparing an aqueous monomer solution before polymerization. The polymerization may be performed using the monomer of the monomer, or may be performed in the middle of the polymerization of the monomer aqueous solution, but the neutralized monomer is used from the viewpoint of improvement in productivity and physical properties. That is, it is preferable to polymerize using a (partial) neutralized salt of an acid group-containing unsaturated monomer as a monomer, and to polymerize using an acrylic acid (partial) neutralized salt as a monomer. It is particularly preferable to do this.

  According to the above neutralization, the pH of the aqueous monomer solution in the present invention and the hydrogel polymer obtained by polymerizing it is preferably 10.0 or more, more specifically, pH 10.0. It is preferably in the range of ˜13.5, more preferably in the range of pH 11.0 to 13.0. If the pH of the monomer aqueous solution exceeds the above range, the polymerization time may be extended and the productivity may be significantly reduced.

(2) Other Additives In the present invention, preferably, in an aqueous monomer solution containing (meth) acrylic acid (salt) as a polymerizable monomer, ethylene glycol, propylene glycol, glycerin, monosaccharide, sugar alcohol , At least one water-soluble compound selected from the group consisting of oligosaccharides and polyvinyl alcohol having a saponification degree of 70% or more (hereinafter, these compounds may be referred to as water-soluble compounds (A)) in the aqueous solution. On the other hand, you may superpose | polymerize by making 0.5-10.0 mass% coexist.

  In carrying out the present invention, particularly when producing a water-soluble polymer, the water-soluble compound (A) that is allowed to coexist in the monomer aqueous solution does not decrease the polymerization rate and is branched at the end of the polymerization reaction. A polymer that does not cause undesired side reactions such as a cross-linking reaction and is highly water-soluble and has a high degree of polymerization, and has a sufficiently reduced amount of water-insoluble components and residual monomers. Can be an important additive in the production of. Specific examples of the water-soluble compound (A) include compounds having two or more hydroxyl groups in one molecule as shown below.

  That is, examples of the water-soluble compound (A) include ethylene glycol, propylene glycol, glycerin, monosaccharide (eg, pentose such as arabinose and xylose; hexose such as galactose, glucose, mannose and fructose; 6-deoxyglucose, 6-deoxyta Deoxyhexoses such as loose; uronic acids such as glucuronic acid, galacturonic acid, etc.), sugar alcohols (eg erythrol, arabinitol, xylitol, sorbitol, galactitol, mannitol, boremitol, octitol etc.), oligosaccharides (eg sucrose, maltose, cellobiose) Disaccharides such as lactose and agarobiose; trisaccharides such as maltotriose; tetrasaccharides such as maltotetraose) and a saponification degree of 70% or more (preferably 95% or more) Polyvinyl alcohol, etc. These may be used alone may also be used in combination of two or more. Among these, ethylene glycol, propylene glycol, glycerin and sugar alcohols exhibiting excellent compatibility with (meth) acrylic acid (salt), which is the main polymerizable monomer, are particularly preferable. It is recognized as a food additive and is a highly safe glycerin for the human body.

  Moreover, it is preferable to set the addition amount of this water-soluble compound (A) to the range of 0.5-10.0 mass% with respect to monomer aqueous solution, and 1.0-5.0 mass% is more preferable. 2.0 to 3.5% by mass is more preferable. When the addition amount exceeds 10.0% by mass, the amount of the monomer remaining in the polymer may be 1.0% by mass or more, which is not preferable. An object of the present invention is to provide a water-soluble polymer excellent in water solubility, in which the amount of monomer remaining in the polymer is sufficiently reduced and the water-insoluble matter is also sufficiently reduced. In order to obtain it, it is preferable to set the addition amount of the water-soluble compound (A) within the above-mentioned range.

  In the present invention, if necessary, deodorants, antibacterial agents, fragrances, inorganic powders such as silicon dioxide and titanium oxide, polysaccharides such as starch and cellulose and derivatives thereof, hydrophilic polymers such as polyvinyl alcohol, Thermoplastic resins such as polyethylene and polypropylene, foaming agents, pigments, dyes, hydrophilic short fibers, plasticizers, chain transfer agents such as hypophosphorous acid (salts), etc., 5% by mass or less, preferably May be contained in an amount of 1% by mass or less. In addition, a water-absorbing resin or a water-soluble resin, for example, polysaccharides such as starch and cellulose, and derivatives thereof, polyvinyl alcohol, and the like are used in the amount of 0 to 50 with respect to the monomers at the start of polymerization and the hydrous gel during polymerization or after polymerization. It may be present in an amount of 0.1% to 30% by mass (with respect to the monomer), and may be a composition with a graft polymer or a polymer thereof.

  In order to obtain a polymer in the form of a dry powder as a product, as shown in FIG. 1, the processing steps include these steps in the order of polymerization, extrusion (or gel crushing), drying, pulverization, and classification. Is preferred. That is, a kneading process for the purpose of extrusion, crushing, and / or mixing with various additives is provided between the polymerization process and the drying process, and the hydrogel polymer obtained by polymerization is finely divided. Is preferable. Here, the polymerization step is a step of polymerizing a monomer component mainly composed of acrylic acid (salt), for example, by polymerizing the monomer component in an aqueous solution in the presence of a polymerization initiator. The extrusion, crushing, and kneading steps are performed in the subsequent drying step while applying specific power to the hydrated gel polymer obtained in the polymerization step (hereinafter also simply referred to as “gel” or “hydrated gel”). This is a step of crushing the gel so that it is easily dried. The drying step is a step of drying the crushed water-containing gel, and the pulverization step is a step of crushing the dried product into a certain size (particle size). By classifying in this classification step, a polymer that can be suitably used in various fields is obtained.

  The polymerization process, extrusion / crushing / kneading process, drying process, crushing process and classification process in the production method of the present invention will be described in detail below.

(3) Polymerization step As described above, the present invention is characterized by the polymerization step. That is, in this invention, the method of superposing | polymerizing monomer aqueous solution by the stationary polymerization by a continuous belt polymerization method is employ | adopted.

  The monomer concentration in the monomer aqueous solution at the time of polymerization is preferably 20 to 60% by mass. More preferably, it is 25-55 mass%, More preferably, it is 30-50 mass%. In addition, the density | concentration of said monomer component is calculated | required as mass ratio of the polymerizable monomer with respect to the mass of monomer aqueous solution (a solvent is included) containing the monomer component used for superposition | polymerization.

  The above-mentioned continuous belt polymerization method, which is one form of the static polymerization method, is the introduction of an aqueous monomer solution to which a thermal decomposition type or photodecomposition type polymerization initiator is added onto an endless belt, and heating or light irradiation. This is a preferred method in which the polymerization can be started by (preferably ultraviolet irradiation) and the product can be continuously produced. As an example, a polymerization reaction using a belt polymerization machine as shown in FIG. 2 is a preferred embodiment of the present invention. One.

  The polymerization method by photopolymerization using a belt polymerization machine is described in detail in Japanese Patent Application Laid-Open No. 2010-155901, Japanese Patent Application Laid-Open No. 2012-25818, etc. previously filed by the present inventors. These methods can also be suitably employed in the present invention.

  The polymerization initiator used in the present invention is appropriately selected depending on the form of polymerization. Examples of such polymerization initiators include thermal decomposition polymerization initiators, photodecomposition polymerization initiators, and redox polymerization initiators.

  Examples of the thermal decomposition polymerization initiator include persulfates such as sodium persulfate, potassium persulfate, and ammonium persulfate; peroxides such as hydrogen peroxide, t-butyl peroxide, and methyl ethyl ketone peroxide. . Examples of the redox polymerization initiator include a system in which a reducing compound such as L-ascorbic acid or sodium bisulfite is used in combination with the persulfate and / or peroxide. Examples of the photodegradable polymerization initiator include benzoin derivatives, benzyl derivatives, acetophenone derivatives, benzophenone derivatives, and azo compounds. Specific examples include various compounds described in the above-mentioned previous application (Japanese Patent Laid-Open No. 2012-25818). Among these photodegradable polymerization initiators, azo-based water-soluble compounds, particularly 2,2 ′ -Azobis (2-amidinopropane) and its hydrochloride, sulfate, acetate, 4,4'-azobis (4-cyanovaleric acid) and the like are preferable. The thermal decomposition type polymerization initiator and the photodecomposition type initiator may be used alone or in combination of two or more. Furthermore, a heat decomposable polymerization initiator and a photodegradable polymerization initiator can be used in combination. In the case of using a photodegradable polymerization initiator, the amount of residual monomer and insoluble matter in the resulting water-soluble polymer may increase. It is preferable to use an agent.

  As the usage-amount of the said polymerization initiator, it is preferable that it is 0.0001-1g with respect to 1 mol of monomer components used for superposition | polymerization, Furthermore, 0.001-0.5g. Thereby, the weight average molecular weight and the polymerization rate of the polymer can be made sufficiently high.

  The method for adding the polymerization initiator is not particularly limited, and it may be added to the raw material monomer aqueous solution in advance and dissolved. The polymerization initiator aqueous solution may be added separately from the raw material monomer aqueous solution. These may be put on the belt of the polymerization machine at the same time, but in the former case, the monomer aqueous solution preparation container and the piping for charging are charged before the polymerization machine is charged. In the latter case, the raw material monomer aqueous solution and the polymerization initiator are not sufficiently mixed, and the polymerization may be uneven and the desired polymer may not be obtained. There is. Therefore, an aqueous solution of a polymerization initiator is prepared separately from the raw material monomer aqueous solution, and these are mixed before being put on the belt of the polymerization machine, for example, uniformly mixed in the pipe immediately before being charged ( A method of line mixing) is preferable.

  In the present invention, a chain transfer agent can be used in combination with the polymerization initiator. By using an appropriate amount of chain transfer agent, a polymer having a larger mass average molecular weight can be produced, and as a result, the effects of the present invention can be more fully exhibited.

  Examples of the chain transfer agent include sulfur-containing compounds such as thioglycolic acid, thioacetic acid, and mercaptoethanol; phosphorous compounds such as phosphorous acid and sodium phosphite; hypophosphorous acid such as hypophosphorous acid and sodium hypophosphite Preferred compounds are alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol and n-butyl alcohol. Among these, hypophosphorous acid compounds are preferable. More preferred is sodium hypophosphite. The amount of the chain transfer agent used may be appropriately set depending on the polymerization concentration, a combination with a polymerization initiator, etc., but is preferably 0.0001 g or more with respect to 1 mol of the monomer component used for the polymerization. Moreover, 0.2 g or less is preferable. Further, it is more preferably 0.001 g or more and 0.15 g or less, and particularly preferably 0.005 g or more and 0.10 g or less.

  As the solvent used in the monomer aqueous solution, water is most preferable, and an aqueous mixed solvent in which water and a hydrophilic organic solvent are appropriately used may be used. As the hydrophilic organic solvent, alcohols such as methanol and ethanol; ketones such as acetone, lower ethers and the like are preferable.

  In the aqueous solution polymerization, it is preferable to carry out the polymerization in a state in which dissolved oxygen dissolved in the monomer aqueous solution is removed in advance by, for example, a method of bubbling nitrogen gas. The dissolved oxygen concentration in the aqueous monomer solution when introduced into the polymerization machine is preferably 8 ppm or less, and more preferably 6 ppm or less.

  The temperature of the aqueous monomer solution used for polymerization, that is, when charged on the belt polymerization machine is preferably 5 to 60 ° C, more preferably 10 to 50 ° C, and further preferably 20 to 40 ° C. . If the temperature of the aqueous monomer solution is less than 5 ° C., it may take a long time to start polymerization, and the residual monomer amount may increase. Furthermore, in order to overcome this, if the polymer is heated at a high temperature, a rapid polymerization reaction may occur, so that a polymer having the desired physical properties may not be obtained. On the other hand, belt polymerization is attempted to complete the polymerization reaction while maintaining a mild state. Lowering the transport speed of the machine leads to an increase in manufacturing cost, which is not preferable. Further, when the temperature of the monomer aqueous solution exceeds 60 ° C., a rapid polymerization reaction occurs, so that not only a polymer having desired physical properties may not be obtained, but also a large amount of insoluble matter may be generated. Furthermore, since polymerization occurs in the piping for introducing the monomer aqueous solution to cause clogging and continuous stable production may be difficult, it is not preferable.

  In the present invention, when the monomer aqueous solution is polymerized by the continuous belt polymerization machine, at least a specific region of the polymerization region starting from the charging point of the monomer aqueous solution is heated to a specific temperature. In addition, the superposition | polymerization area | region in this invention shall mean the area | region shown below.

  The starting point in the polymerization region referred to in the present invention refers to the point where the aqueous monomer solution is introduced onto the belt of the polymerization machine, that is, the 11 position shown in FIG. The end point of the polymerization region is based on the contact point (position 14 in FIG. 3) between the rotary drive drum (or pulley) on the belt traveling direction side (polymer gel discharge side) and the belt. The point closer to the starting point side by the radius length of the driving drum than the point, that is, 13 positions shown in FIG. That is, the traveling direction length in the polymerization region referred to in the present invention is a distance from 11 to 13 as shown in FIG. Further, the width of the polymerization region includes at least the width when spread on the belt after the monomer aqueous solution is added, and is narrower than the width of the belt. In the case of producing a polymer continuously and stably, since it is common to operate so that the width of the polymerization region is always in a substantially constant state, the polymerization region in the present invention is simply The distance from 11 to 13 in the length of the polymerization belt in the traveling direction may be indicated.

  The polymerization initiation point refers to the point where the polymerization of the monomer in the aqueous solution started after the monomer aqueous solution was put on the belt of the polymerization machine, and the 12 positions shown in FIG. Point to. The polymerization start point 12 is a point where a state change such as white turbidity, foaming, liquid viscosity increase, liquid temperature increase occurs after the monomer aqueous solution is put on the belt, and the liquid temperature is a contact type or non-contact type. It can be measured with a temperature sensor, and appearance changes such as cloudiness, foaming, and increase in liquid viscosity can usually be observed visually or with a monitor. The position of the polymerization start point 12 depends on the type of monomer used, the monomer concentration in the aqueous monomer solution, the type and amount of the polymerization initiator, the temperature of the aqueous monomer solution, and the heating means described later. It varies arbitrarily depending on the polymerization conditions such as the degree of heating and the belt traveling speed of the belt polymerization machine, and is not uniquely determined. In the present invention, the polymerization start point 12 is preferably in the polymerization region, that is, between the start point 11 and the end point 13 and between the start point 11 and less than 50% in the traveling direction. More preferably, it is between up to 25%, more preferably up to 30%, even more preferably up to 25%, most preferably up to 10%.

  In the present invention, in particular, at least a part of the region from the monomer aqueous solution introduction point (starting point) 11 to the polymerization start point 12 in the polymerization region is heated to a temperature exceeding 40 ° C. using a heating means. By carrying out like this, the start and progress of superposition | polymerization can be performed smoothly, and the water-soluble polymer of this invention can be manufactured efficiently and stably. Further, the obtained water-soluble polymer can greatly reduce the Weisenberg phenomenon when dissolved in water, and the thixotropic property of the aqueous solution after dissolution, and the resulting aqueous solution has a high viscosity, and further remains. Since the amount of monomer and insoluble matter is small, it can be suitably used for various applications.

  In the present invention, at least a part of the region from the starting point to the polymerization start point may be heated, and any point may be heated as long as it is within the range of the region. The region to be heated is preferably a region including at least the starting point, more preferably a region from the starting point to the polymerization starting point, further preferably a region exceeding the polymerization starting point from the starting point, and polymerization from the starting point. It is particularly preferable that the region includes a region up to the starting point and before and after both points.

  Moreover, in this invention, the said area | region is heated to the temperature exceeding 40 degreeC. When the heating temperature is 40 ° C. or lower, since the start of polymerization tends to be delayed, not only the production efficiency may be lowered, but also the performance of the obtained water-soluble polymer, specifically, when dissolved in water The Weisenberg phenomenon and thixotropy of the aqueous solution after dissolution may become high, which is not preferable. The heating temperature should just exceed 40 degreeC, 40 degreeC-100 degreeC is preferable, 45-70 degreeC is more preferable, 50-60 degreeC is further more preferable.

  In the present invention, it is preferable to heat at least 50% of the monomer aqueous solution introduction point (starting point) 11 in the polymerization region. That is, when the starting point of the polymerization region is 0% and the end point is 100%, it is preferable to heat at least the region from the starting point to the polymerization starting point to half the polymerization region. More specifically, in addition to at least a part of the region from the starting point to the polymerization start point, it is preferable to heat at least a part of the region exceeding the polymerization start point and half of the polymerization region. Furthermore, it is more preferable to heat the entire region from the starting point to the half of the polymerization region beyond the polymerization start point. Further, in the polymerization region, it is more preferable to heat a region up to at least 75% from the starting point, more preferably to heat a region up to 85%, and to heat a region up to 100%, that is, the entire polymerization region. Even more preferably. By performing such heating, the polymerization can proceed more smoothly, and the water-soluble polymer of the present invention can be produced efficiently and stably.

  The heating means used in the present invention is not particularly limited, and various heat sources such as an electric heater, a far-infrared heater, hot water, and various heat media can be used. Among these, it is preferable to use warm water from the viewpoint of heat transfer efficiency and safety, and from the viewpoint that the medium can be recovered and reused. It is preferable to use hot water having a temperature exceeding 40 ° C. because the present invention can be easily and reliably carried out. The temperature of warm water is preferably more than 40 ° C to 100 ° C, more preferably 45 to 70 ° C, and further preferably 50 to 60 ° C. The heating using the heating means may be performed from the upper part of the belt and the monomer aqueous solution or water-containing gel, but is preferably performed at the lower part of the belt. That is, it is particularly preferable to spray from the lower part of the belt so that the hot water directly contacts the lower surface of the belt.

  In the present invention, a means for cooling in the latter half of the polymerization region may be used. About the area | region in the case of cooling, it is preferable that it is a 50-100% area | region in the superposition | polymerization area | region which makes the starting point of monomer aqueous solution the starting point, It is more preferable that it is a 75-100% area | region, 85- More preferably, the region is 100%. By the cooling means, undesired side reactions such as self-crosslinking between polymers and generation of insoluble matter can be suppressed. As the cooling means, like the heating means, means for spraying water from the lower part of the belt is preferable. Moreover, as cooling temperature, 40 degrees C or less is preferable, 0-40 degreeC is more preferable, 15-38 degreeC is further more preferable, and 30-35 degreeC is especially preferable. In addition, it is not necessary to perform cooling by a cooling means, such as a method of heating the entire polymerization region as described above.

  In the present invention, after the monomer aqueous solution is put on the belt, the time required for the portion to pass through the end point of the polymerization region as the polymerization proceeds, that is, the residence time of the monomer aqueous solution in the polymerization region is as follows. Although not particularly limited, it is preferably in the range of 30 to 90 minutes. If the residence time is shorter than 30 minutes, the progress of polymerization may not be completed and the remaining amount of unreacted monomer may increase. Further, if the residence time is longer than 90 minutes, the production efficiency is lowered, which is not preferable. The lower limit of the residence time is more preferably 35 minutes or more, the upper limit is more preferably 75 minutes or less, and even more preferably 60 minutes or less.

  The specification of the continuous belt polymerization machine used in the present invention is not particularly limited, but is the length in the direction of travel in the polymerization region, that is, from the point of introduction (starting point) of the aqueous monomer solution. It is preferable that the distance to the end point of the polymerization region be 2 to 30 m, and more preferably 5 to 20 m. In order to make the residence time within a preferable range using such a belt polymerization machine, the belt conveyance speed is preferably 0.02 to 1.0 m / min, and 0.05 to 0.6 m / min. It is more preferable to set it as min, and it is still more preferable to set it as 0.15-0.5 m / min. Moreover, about the width | variety of a superposition | polymerization area | region, it is less than the width | variety of the belt to be used, it is preferable that it is 0.2-3.0 m, and it is more preferable that it is 0.5-2.0 m.

  By performing the polymerization as described above, it is possible not only to continuously and efficiently produce the water-soluble polymer according to the present invention, but also to solve the problems noted in the present invention. Can be obtained.

  In addition, when performing photopolymerization as said superposition | polymerization system, or when performing photopolymerization in addition to a heating, it is preferable to irradiate near ultraviolet rays to monomer aqueous solution. Also, for example, in the above photopolymerization, polymerization is performed by irradiating with relatively low-intensity near-ultraviolet rays in the presence of a photodegradable polymerization initiator, and then irradiating with relatively high-intensity near-ultraviolet rays. It is preferable that the method includes a step of completing the process. By irradiating near-ultraviolet rays having different intensities in two stages as described above, the polymerization of the monomer is promoted, and the resulting water-soluble polymer can be made high in quality as described above.

As the step of polymerizing by irradiating near-ultraviolet rays in the first stage, the irradiation intensity is preferably 10 W / m ² or less. If it exceeds 10 W / m ² , the amount of light is too high to obtain a sufficiently high viscosity polymer, and the insoluble content may not be reduced. The upper limit of the irradiation intensity is more preferably 8W / ^{m 2} or less, 6W / ^{m 2} or less is more preferred. Moreover, as a lower limit, it is preferable that it is 1 W / m < ² > or more. If it is less than 1 W / m ² , the polymerization reaction may not be promoted sufficiently. The lower limit is more preferably 1.5 W / ^{m 2} or more, 2W / ^{m 2} or more is more preferable.

In the first polymerization step, the irradiation time of near ultraviolet rays of 10 W / m ² or less is preferably 5 minutes or more. If the irradiation time is less than 5 minutes, the polymerization reaction cannot be promoted sufficiently, and a desired polymer may not be obtained. The irradiation time is more preferably 10 minutes or more, and further preferably 15 minutes or more. The upper limit of the irradiation time is preferably less than 100 minutes. When the irradiation time is 100 minutes or more, not only the productivity is lowered but also the effect of the obtained polymer may not be sufficiently obtained. . The upper limit is more preferably less than 80 minutes, and further preferably less than 60 minutes.

As a step of completing the polymerization by irradiating near-ultraviolet rays in the second stage, it is preferable that the irradiation intensity exceeds 10 W / m ² . When it is 10 W / m ² or less, there is a possibility that the remaining amount of monomer cannot be sufficiently reduced because the amount of light is too low. More preferably in excess of 12W / ^{m 2,} still more preferably in excess of 15W / ^{m 2.} The upper limit is preferably 100 W / m ² or less. If it exceeds 100 W / m ² , the irradiation intensity is too strong and the molecular weight may be lowered. More preferably, it is 80 W / m < ² > or less, More preferably, it is 50 W / m < ² > or less. The irradiation time of the near-ultraviolet rays in the second stage is not particularly limited as long as it is an irradiation time that can sufficiently reduce the remaining monomer, but it is preferably 1 to 30 minutes. More preferably, it is 2-20 minutes, More preferably, it is 3-15 minutes.

  As the apparatus for irradiating near ultraviolet rays in the polymerization step, for example, a high pressure mercury lamp, a low pressure mercury lamp, a metal halide lamp, a fluorescent chemical lamp, a fluorescent blue lamp and the like are suitable. Specifically, Neoarc (N), Neoarc (W), Neoarc (WW), Master Color CDM (3000K), Master Color CDM (4200K), Neoarc Beam (N), Neoarc Beam (WW), Neoarc Beam (for outdoor use), Neoarc E Base (N), Neoarc E Base (WW), HQI Lamp (D), HQI Lamp (NDL), HQI Lamp (WDL), Dyna Beam 2, Sunlight Lamp, HL-Neohalide 2 ( Transparent type), HL-Neohalide 2 (Diffusion type), HL-Neohalide (Transparent type), HL-Neohalide (Diffusion type), Neohalide lamp (Transparent type), Neohalide lamp (Diffusion type), Color HID lamp (B ), Color HID lamp (G), neo-color (high color rendering), neo-color (high saturation), HL-neol D, Twin Neolux L, Twin Neolux, HL-Neolux, Neolux, Fluorescent Mercury Lamp, Incandescent Fluorescent Mercury Lamp, Transparent Mercury Lamp, Black Light Mercury Lamp, Chalkless Mercury Lamp, etc. . Further, the wavelength region of near ultraviolet rays is preferably 300 nm or more and preferably 500 nm or less. When ultraviolet rays having a wavelength of less than 300 nm are irradiated, the polymerization reaction may be accelerated, and the amount of residual monomer may be small and a water-soluble polymer capable of expressing a high aqueous solution viscosity may not be obtained.

In the present invention, the near-ultraviolet light irradiation intensity is the light irradiation intensity measured at the upper surface of the monomer aqueous solution irradiated with near ultraviolet light, that is, the surface of the monomer aqueous solution. The light irradiation intensity can be measured with the following light meter.
Apparatus: UV meter Manufacturer: Custom Co., Ltd. Model: Main unit UVA-365
Sensor UV sensor (Spectra response 300nm to 400nm)
In addition, as a problem related to the intensity of near-ultraviolet rays, it is difficult to control the polymerization if the intensity is too high, that is, for example, the problem of bumping of the monomer aqueous solution accompanying the rapid start of reaction, and the insoluble matter increases. There is a quality problem that tends to be. By reducing the strength first and then increasing the strength, it is possible to advantageously cope with such a problem.

  As a method for changing the intensity of near-ultraviolet rays, a method using ultraviolet lamps having different irradiation intensities, a method of increasing or decreasing the irradiation intensity by inverter control, a light reducing plate such as a punching metal (translucent light) between the ultraviolet lamp and the polymerization liquid. For example, a method of installing a plate). Even if the same lamp is used, the irradiation intensity can be changed as appropriate by using a plurality of different light-attenuating plates. Can be irradiated.

  In addition, when the photopolymerization method as described above is employed, or when the thermal polymerization method and the photopolymerization method are used in combination, the amount of residual monomer and insoluble matter in the obtained water-soluble polymer may increase. Therefore, in the present invention, it is preferable to employ only a thermal polymerization method by heating with a heating means.

  In the production of the water-soluble polymer in the present invention, if rapid heat generation occurs during polymerization or the polymerization peak temperature becomes too high, such as gel foaming, polymer branching, self-crosslinking, or increase in molecular weight distribution, etc. It is preferable to control the reaction temperature, particularly the peak temperature during polymerization, as much as possible because an undesirable side reaction may occur and it may not be possible to efficiently produce a product with stable quality in a high yield. . The peak temperature during polymerization is preferably suppressed to 95 ° C. or lower. When the peak temperature of the polymerization solution exceeds 95 ° C., the polymerization reaction proceeds excessively, and the aqueous solution viscosity of the resulting polymer may not be sufficiently high. More preferably, it is 90 degrees C or less, More preferably, it is 85 degrees C or less. As a minimum of peak temperature, what is necessary is just the temperature from which the aqueous solution viscosity of the polymer obtained is sufficient, and it is preferable that it is 50 degreeC or more. More preferably, it is 60 degreeC or more, More preferably, it is 70 degreeC or more. There is no time limit to reach the peak temperature.

(4) Extrusion / Crushing / Kneading Step The water-containing gel-like polymer obtained in the polymerization step may be dried as it is, but if necessary, chopped or finely granulated using a gel crusher or an extruder. It is preferable to dry after the formation. Further, various additives may be mixed before drying the hydrogel polymer, and the gel can be shredded and granulated simultaneously with mixing in a kneader used at that time. Thus, the hydrogel polymer obtained by aqueous solution polymerization has a mass average particle diameter (specified by wet sieving classification) of about 0.1 mm to about 50 mm, more preferably 0.2 to 10 mm, by a predetermined method. Can be broken into pieces of about 0.5 to 5 mm and dried in a subsequent drying step.

  Therefore, fine graining can be performed by various methods. For example, a screw type extruder having a porous structure of an arbitrary shape can be used to extrude and crush while applying specific power. When extruding, crushing, and mixing in this step, generally one or more rotating shafts having a spiral shape or a number of uneven shapes on its internal structure, or having a plurality of rotary blades for cutting and mixing are used. Various devices having a complicated inner surface shape can be used.

  Although it does not specifically limit as a shape of the hydrated gel crushed in the said process, For example, a granular form, a pellet form, string shape etc. are suitable, and the magnitude | size is also not specifically limited. Since these crushed water-containing gels are made porous by containing air in the extruder, the drying property is improved. The crushed hydrogel is reduced in weight when dried, which is advantageous for transportation and storage.

  Further, in this step, when the hydrogel polymer is treated at a temperature exceeding 60 ° C., the molecular weight of the polymer decreases, and at a temperature below 30 ° C., there is a risk that the residual monomer may not be sufficiently reduced. Therefore, in order to acquire the effect of this invention, it is preferable that the process temperature (gel retention temperature) in this process shall be 30-60 degreeC.

(5) Drying step The hydrogel polymer obtained in the polymerization step, preferably, the hydrogel polymer crushed in the extrusion / pulverization / kneading step, is dried in the drying step to obtain a polymer. A dry product is preferred. There are various drying methods such as heat drying, hot air (ventilation) drying, vacuum drying, infrared drying, microwave drying, drum dryer drying, azeotropic dehydration with hydrophobic organic solvents, and high humidity drying using high-temperature steam. However, it is preferably hot-air drying with a gas having a dew point of 40 to 100 ° C., more preferably a dew point of 50 to 90 ° C. Furthermore, it is preferable to dry using a belt dryer while passing hot air over the belt.

  The drying temperature is not particularly limited, but is preferably within the range of 100 to 250 ° C, more preferably 120 to 230 ° C, still more preferably 140 ° C to 200 ° C, and even more preferably 150 ° C to 180 ° C. It may be within the range. In particular, in the case of hot air drying, the hot air temperature is preferably within the range of 100 to 250 ° C, more preferably 120 to 230 ° C, still more preferably 140 ° C to 200 ° C, and even more preferably within the range of 150 ° C to 180 ° C. It should be inside. The drying time is appropriately determined and is not particularly limited, but is preferably 10 seconds to 2 hours, more preferably 1 minute to 1.5 hours, and particularly preferably 10 minutes to 1 hour.

  The surface temperature of the hydrogel immediately before entering the dryer is preferably 40 to 110 ° C, more preferably 60 to 100 ° C. When the temperature is lower than 40 ° C., a balloon-like dry product is formed at the time of drying, and a large amount of fine powder is generated at the time of pulverization.

  The time from when the hydrogel is discharged from the polymerizer, preferably after the hydrogel is crushed until it enters the dryer is shorter from the viewpoint of coloring the polymer. It is preferably within 2 hours, more preferably within 1 hour, further preferably within 30 minutes, particularly preferably within 10 minutes, and most preferably within 2 minutes.

  In the drying step, the solid content after drying is 80% by mass or more, more preferably 85% by mass or more, 90% by mass or more, from the physical properties of the polymer obtained, and also from the ease of pulverization in the subsequent step. It is particularly preferable to dry to 92 to 98% by mass.

(6) Grinding step In the present invention, it is preferable that the water-containing gel dried in the drying step is crushed into a certain size (particle size) in the pulverization step. The apparatus used in the pulverization process is not particularly limited, and a commonly performed method is adopted. For example, a vibration mill, a roll granulator, a knuckle type pulverizer, a high-speed rotary pulverizer (pin mill, hammer mill, screw mill, roll mill) A cylindrical mixer or the like can be used.

(7) Classification process In this invention, it is preferable that the granular material crushed by the said grinding | pulverization process adjusts a particle size by a classification process. The classification method is also not particularly limited, and a commonly performed method such as sieving using a sieve is employed. Specifically, for example, when the size range of the granular material (also referred to as a pulverized product) obtained in the pulverization step is set to 150 to 500 μm, the pulverized product is first generated using a sieve having an opening of a 500 μm sieve. After sieving, the crushed product that has passed through the sieve is sieved with a sieve having a 150 μm sieve opening. The ground product remaining on the 150 μm sieve becomes the product polymer within the desired particle size range.

(8) Others The polymer obtained through the above steps may be used in the form of a product as it is, and other additives may be mixed for the purpose of improving dispersibility, fluidity and other required performances. Further, the surface of the polymer particles mixed with the additive may be modified to obtain a product. For example, for the purpose of improving the hydrophilicity and water dispersibility of the water-soluble polymer, the water-soluble compound (A) as described above may be further added and mixed.

  As other additives, water-insoluble fine particles such as hydrophilic amorphous silica, reducing agents, antibacterial agents, deodorants, chelating agents, polyvalent metal compounds, etc. may be added. Is preferably 0.001 to 20 parts by mass, more preferably 0.01 to 10 parts by mass, and particularly preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of the polymer.

  It is desirable that the mixing device used when mixing the polymer and various additives has a large mixing force in order to mix both uniformly and reliably. Examples of the mixing apparatus include a cylindrical mixer, a double wall conical mixer, a V-shaped mixer, a ribbon mixer, a screw mixer, a fluidized-type furnace rotary disk mixer, and an airflow mixer. A double-arm kneader, an internal mixer, a pulverizing kneader, a rotary mixer, a screw extruder, a turbulizer, and the like are suitable.

(9) Water-soluble polymer As described above, the water-soluble polymer obtained by the production method of the present invention sufficiently exhibits a desired aqueous solution viscosity and is generated upon dissolution in an aqueous solvent. The Weisenberg phenomenon can be greatly reduced to improve workability during dissolution, and the thixotropy of the resulting aqueous solution can also be greatly reduced to improve the handling workability of the aqueous solution after dissolution. It has an excellent effect of satisfying physical property values at the same time. Further, the water-soluble polymer of the present invention satisfies the above physical property values, and the amount of residual monomer and water insoluble matter is sufficiently reduced.

  The residual monomer concentration of the water-soluble polymer according to the present invention is preferably less than 1.0% by mass, more preferably 0.9% by mass or less, further preferably 0.5% by mass or less, and 0.4% by mass. The following are even more preferred: It is preferable to make the residual monomer concentration less than 1.0% by mass because it is excellent in safety in actual use in various uses, particularly in medical use, food use, feed use and the like. The residual monomer concentration (also referred to as residual monomer amount) as used in the present invention is the official standard for food additives 7th edition 436, 437, or the 10th edition of the feed additive component specifications, etc. It is measured by the following method described in the section of sodium polyacrylate, purity test on pages 239 and 240.

(Measurement method of residual monomer amount)
In the case of hydrous gel, about 1 g of gel in terms of solid content, and in the case of powdery dry polymer which is the final product form, about 1 g as a powder is accurately weighed and placed in a 300 ml iodine bottle, Add 100 ml and let it melt for about 24 hours with occasional shaking. To this solution, add exactly 10 ml of potassium bromate / potassium bromide test solution, shake well, add 10 ml of acid (usually hydrochloric acid) quickly, immediately seal and shake again well, then top of the iodine bottle About 20 ml of potassium iodide test solution is put in the tube and left in the dark for 20 minutes. Next, loosen the stopper and pour the potassium iodide reagent solution, immediately seal it and shake well, then titrate with 0.1 mol / l sodium thiosulfate solution (indicator starch reagent solution 2 mL). Separately, a blank test is performed in the same manner, and the content is obtained by the following formula.

（ただし、ａ：空試験における０．１ｍｏｌ／ｌチオ硫酸ナトリウム溶液の消費量（ｍｌ）、ｂ：本試験における０．１ｍｏｌ／ｌチオ硫酸ナトリウム溶液の消費量（ｍｌ））
また、本発明によって得られる水溶性重合体の水不溶解分の量は、３．０ｇ以下が好ましく、２．５ｇ以下がより好ましく、１．５ｇ以下がさらに好ましく、０．５ｇ以下がさらにより好ましい。水不溶解分の量を３．０ｇ以下の範囲とすることで、水系溶媒に溶解した後の溶液の高粘度化を図ることができるとともに、低不溶解分のものとなるため、各種用途に好適に用いることができる、優れた品質を有するものとなる。例えば、パップ剤として使用した場合には、少ない使用量で水溶性重合体の作用効果を十分に発揮することが可能となり、より均質な膏体が得られることとなる。なお、本発明でいう水不溶解分は以下の方法により測定される。

(However, a: consumption of 0.1 mol / l sodium thiosulfate solution in the blank test (ml), b: consumption of 0.1 mol / l sodium thiosulfate solution in the test (ml))
Further, the amount of water-insoluble portion of the water-soluble polymer obtained by the present invention is preferably 3.0 g or less, more preferably 2.5 g or less, further preferably 1.5 g or less, and even more preferably 0.5 g or less. preferable. By making the amount of water insolubles in the range of 3.0 g or less, it is possible to increase the viscosity of the solution after being dissolved in an aqueous solvent, and because it is of low insoluble content, It has excellent quality that can be suitably used. For example, when used as a poultice, it is possible to sufficiently exhibit the action and effect of the water-soluble polymer with a small amount of use, and a more uniform plaster can be obtained. The water-insoluble matter referred to in the present invention is measured by the following method.

(Measurement method of water insoluble matter)
In a beaker having a capacity of 500 ml, 500 g of ion-exchanged water is added, and 1.0 g of a dried product of the water-soluble polymer sample is added to the ion-exchanged water while stirring using a magnetic stirrer so that mamako cannot be formed. Next, the mixture was stirred (100 rpm) at 30 ° C. for 2 hours using a jar tester (manufactured by Miyamoto Riken Co., Ltd., model JMD-6ES), and then filtered using a 32 mesh filter to obtain a water-containing state. Remove insoluble material. Then, this insoluble matter is weighed immediately (within 1 minute) so as not to dry, and this weighed value (g) is taken as the water insoluble matter. The filtration and weighing are performed at 25 ° C. and a relative humidity of 60%.

  The aqueous solution viscosity of the water-soluble polymer according to the present invention is preferably 500 mPa · s or more, more preferably 600 mPa · s or more and 700 mPa · s or more. Since the obtained aqueous solution has such a high viscosity, high performance can be expressed with a small amount of use, and therefore it can be suitably used for various applications. In addition, the aqueous solution viscosity concerning this invention is measured and calculated | required with the following method.

(Measurement method of aqueous solution viscosity)
Take 499.0 g of ion-exchange water in a 500 ml beaker and stir with a magnetic stirrer to dry the water-soluble polymer (after the polymerization, the hydrogel is cut into a width of about 5 mm, a length of about 40 mm, and a thickness of about 2 mm. , 1.0g of powder one by one on a wire mesh, dried in a constant temperature drier at 190 ° C for 2 hours, pulverized and classified to 20-60 mesh, so that Mamako cannot be added and dissolved. . Next, using a jar tester (Miyamoto Riken Co., Ltd., model JMD-6ES), the mixture is stirred at 180 rpm for 50 minutes. After adjusting the temperature of this aqueous solution to 30 ° C., the viscosity of the aqueous solution was measured using a B-type viscometer (manufactured by Tokyo Keiki Co., Ltd., model: BL-II type, rotor: No. 2, rotation speed: 30 rpm).

  The Weisenberg characteristic of the water-soluble polymer according to the present invention is preferably 10 mm or less as a Weisenberg value, more preferably 8 mm or less, further preferably 6 mm or less, and still more preferably 5 mm or less. By having such a Weisenberg value, workability when dissolving a water-soluble polymer in an aqueous solvent is excellent, so work can be performed efficiently when used in various applications, and work time can be shortened. Is also connected. The Weisenberg value according to the present invention means a value measured and determined by the following method.

(Calculation method of Weisenberg value)
In an atmosphere of room temperature (about 25 ° C.), 20 ml of methanol is put into a 500 ml beaker, and an amount of water-soluble polymer is added to the amount of 1.00 g in terms of solid content. While stirring this mixture at 500 rpm using a stirrer, 480 ml of pure water is added. After confirming that the liquid after mixing has dissolved uniformly, the beaker is transferred to a jar tester (Miyamoto Riken Co., Ltd., model JMD-6ES) and set. The hot water bath temperature of the jar tester is set to 30 ° C., stirring is started at 180 rpm, and the appearance during stirring is taken 50 minutes after the start of stirring. In the photographed image, the ratio between the diameter of the stirring shaft and the winding height of the liquid was calculated, and the actual winding height was obtained from the actual diameter value of the stirring shaft, and this was used as the Weisenberg value. In addition, said solid content conversion value was calculated | required from the drying loss after drying the obtained water-soluble polymer for 240 minutes at 105 degreeC using a constant temperature dryer.

  The thixotropic property of the water-soluble polymer according to the present invention is preferably 50 or less, more preferably 40 or less, still more preferably 35 or less, and even more preferably 30 or less as a thixotropy value. By having such a thixotropy value, it is excellent in workability at the time of handling the solution after dissolving the water-soluble polymer, so that the work can be carried out efficiently when used in various applications. The thixotropy value according to the present invention means a value measured and calculated by the following method.

(Calculation method of thixotropy value)
Under an atmosphere of room temperature (about 25 ° C.), 40 ml of methanol is put into a 500 ml beaker, and an amount of water-soluble polymer in an amount of 2.50 g in terms of solid content is charged therein. While stirring the mixture at 500 rpm using a stirrer, 460 ml of pure water is added. After confirming that the liquid after mixing has dissolved uniformly, the beaker is transferred to a jar tester (Miyamoto Riken Co., Ltd., model JMD-6ES) and set. The hot water bath temperature of the jar tester was set to 30 ° C., and the mixture was stirred at 180 rpm for 50 minutes. The liquid after stirring was used as a sample liquid, and a fan VG meter (manufactured by Fann Instrument Company, model: 35, rotor radius: 18.415 mm, bob radius: 17.245 mm, bob height: 38 mm) was used. Thus, the viscosity was measured. A fixed amount (300 ml) of the sample solution is put in a sample cup for the VG meter, and the sample solution is set on the VG meter so that the surface of the sample solution is in contact with the score line of the rotor. Set the rotary knob to 600 rpm, turn the motor switch to the “Hi” side, rotate it, and read the measured value. After 10 seconds, the rotary knob is set to 3 rpm, the motor switch is turned to the “Lo” side, and the measured value is read. Each read value is multiplied by a viscosity coefficient (100 when the rotational speed is 3 rpm, and 0.5 when the rotational speed is 600 rpm) to obtain the viscosity at each rotational speed. Subsequently, the viscosity value at 3 rpm was divided by the viscosity value at 600 rpm, and the obtained value was defined as a thixotropy value. In addition, said solid content conversion value was calculated | required from the drying loss after drying the obtained water-soluble polymer for 240 minutes at 105 degreeC using a constant temperature dryer.

EXAMPLES Hereinafter, although an Example is hung up and this invention is demonstrated further in detail, this invention is not limited only to these Examples. Unless otherwise specified, “part” means “part by mass” and “%” means “% by mass”.
Hereinafter, the belt polymerization machine used for the polymerization will be described with reference to FIG. 2 and FIG. 3, but the belt polymerization machine that can be used in the present invention is not limited to the form shown in these drawings. As long as the conditions specified in (1) can be satisfied, they can be used in the same manner.

  The belt 1 is made of an endless belt made of SUS301 and having a width of 1200 mm. A weir (edge rope: not shown) having a height of 50 mm is provided on the belt 1, and the distance between the two weirs, that is, the polymerization region. The distance corresponding to the width was 800 mm. The belt 1 is supported by two rotary drive drums (or pulleys) 2 on the monomer aqueous solution input side and the water-containing polymer gel discharge side, and is held in a tensioned state so that the belt surface It is possible to maintain the level. Further, the length in the traveling direction in the polymerization region referred to in the present invention, that is, the distance from the introduction point 11 of the monomer aqueous solution to the end point 13 of the polymerization region was 7 m. Further, a hood 6 is provided at the upper part of the belt, and nitrogen is continuously supplied so that the oxygen concentration in the space in the hood at the upper part of the belt is 4% by volume or less. A spray nozzle 3 is provided at the lower part of the belt so that hot water is heated for heating and, optionally, water of 35 ° C. or lower is sprayed from below the belt onto the lower surface of the belt. . The sprayed water is collected from the lower part of the belt. Further, a scraper 4 is attached to the belt polymerization machine outlet, and the hydrogel after polymerization is discharged without remaining on the belt surface. Further, near ultraviolet lamps 5 (for example, trade name: black light, product number: FHF32BLB, manufactured by Toshiba Lighting & Technology Co., Ltd.) are attached to the upper part of the belt in order to perform photopolymerization as necessary. The light intensity was controlled by adjusting the amount of light with an inverter. The belt was continuously operated at a speed of 109 mm / min.

[Example 1]
After adding 45 parts of glycerin to 2440 parts of an aqueous solution of 37% sodium acrylate having a neutralization rate of 100%, a small amount of ion-exchanged water was added to adjust the total amount to 2500 parts. Nitrogen bubbling was performed on the mixed solution, so that the dissolved oxygen concentration in the solution was 6 ppm to obtain a monomer aqueous solution. Separately, an aqueous solution of sodium persulfate 5% was prepared as a polymerization initiator. When the monomer aqueous solution and the polymerization initiator solution are continuously charged into the belt polymerization machine, the polymerization initiator aqueous solution is 0.610 parts per 200 hours of the monomer aqueous solution per unit time. In order to always mix at the ratio of, it was charged while mixing in the pipe. The thickness of the gel as the polymerization progressed was 20 mm.

  The concentration of sodium acrylate in the monomer aqueous solution was 36%. The concentration of glycerin in the aqueous monomer solution was 5.0%. The amount of sodium persulfate added was 0.04 g per mole of sodium acrylate. The pH of the aqueous monomer solution was 12.0.

  Further, in the entire region from the charging point of the monomer aqueous solution to the end point of the polymerization region, 41 ° C. warm water was sprayed from the lower part of the polymerization belt toward the lower surface of the belt and heated.

  In this way, the hydrogel containing sodium polyacrylate was discharged from the rear part of the belt polymerization machine. The obtained water-containing gel was crushed using a meat chopper (manufactured by Hiraga Corporation, model: AEZ10S, die diameter: 4.5 mm), dried at 200 ° C. for 40 minutes using a dryer, and then crushed on a table After pulverizing with a machine (manufactured by Sunbeam, product number: Osterizer 16 SPEED-BLENDER), and classifying with a sieve of 20 mesh (aperture 0.85 mm), a 20-mesh pass water-soluble polymer (1) was obtained. .

  Each physical property of the water-soluble polymer (1) was measured in accordance with the above-described methods, such as the water-insoluble content, the residual monomer content, the aqueous solution viscosity, the Weisenberg value, and the thixotropic value. The results are shown in Table 1.

[Example 2]
Polymerization was performed in the same manner as in Example 1 except that glycerin was 3.1% in the concentration of the monomer aqueous solution, the gel thickness was 15 mm, and the temperature of the hot water was 50 ° C. By treating in the same manner as in Example 1, a water-soluble polymer (2) was obtained. Table 1 shows the results of measuring the physical properties of the water-soluble polymer (2).

[Example 3]
Polymerization is carried out in the same manner as in Example 2 except that the temperature of the hot water is 55 ° C., and the resulting hydrogel is treated in the same manner as in Example 1 to obtain a water-soluble polymer (3). It was. Table 1 shows the results of measuring the physical properties of the water-soluble polymer (3).

[Example 4]
The temperature of the hot water is 60 ° C., and the spray area of the hot water is an area from the origin of the polymerization area to 75%, and in the remaining polymerization area, that is, the area of 75 to 100% from the origin of the polymerization area, from the lower part of the polymerization belt Polymerization was carried out in the same manner as in Example 2 except that water at 30 ° C. was sprayed toward the lower surface of the belt, and the resulting hydrogel was treated in the same manner as in Example 1 to obtain a water-soluble polymer. (4) was obtained. Table 1 shows the results of measurement of physical properties of the water-soluble polymer (4).

[Example 5]
Polymerization was carried out in the same manner as in Example 4 except that the pH of the aqueous monomer solution was 11.0 and the temperature of the hot water was 55 ° C., and the resulting hydrogel was treated in the same manner as in Example 1. As a result, a water-soluble polymer (5) was obtained. Table 1 shows the results of measuring the physical properties of the water-soluble polymer (5).

[Example 6]
Polymerization was carried out in the same manner as in Example 5 except that the pH of the monomer aqueous solution was changed to 13.0, and the resulting hydrogel was treated in the same manner as in Example 1 to obtain a water-soluble polymer ( 6) was obtained. Table 1 shows the results of measurement of physical properties of the water-soluble polymer (6).

[Example 7]
The temperature of the hot water is 63 ° C., and the spray area of the hot water is an area from the origin of the polymerization area to 50%, and the remaining polymerization area, that is, the area of 50 to 100% from the origin of the polymerization area, Polymerization was carried out in the same manner as in Example 2 except that water at 30 ° C. was sprayed toward the lower surface of the belt, and the resulting hydrogel was treated in the same manner as in Example 1 to obtain a water-soluble polymer. (7) was obtained. Table 1 shows the results of measuring the physical properties of the water-soluble polymer (7).

[Example 8]
After adding 18 parts of glycerin to 1950 parts of an aqueous solution of 37% sodium acrylate having a neutralization rate of 100%, a small amount of ion-exchanged water was added to adjust the total amount to 2500 parts. Nitrogen bubbling was performed on the mixed solution, so that the dissolved oxygen concentration in the solution was 6 ppm to obtain a monomer aqueous solution. Separately, a 5% aqueous solution of 2,2′-azobis (2-amidinopropane) dihydrochloride (manufactured by Wako Pure Chemical Industries, Ltd., trade name V-50) was prepared as a polymerization initiator. When the monomer aqueous solution and the polymerization initiator solution are continuously charged into the belt polymerization machine, the polymerization initiator aqueous solution is 0.610 parts per unit time with respect to 160 parts of the monomer aqueous solution. In order to always mix at the ratio of, it was charged while mixing in the pipe. The thickness of the gel accompanying the progress of polymerization was 15 mm.

  The concentration of sodium acrylate in the monomer aqueous solution was 36%. The concentration of glycerin in the aqueous monomer solution was 2.5%. The amount of 2,2′-azobis (2-amidinopropane) dihydrochloride added was 0.05 g with respect to 1 mol of sodium acrylate. The pH of the aqueous monomer solution was 10.0.

  Further, in the entire region from the charging point of the monomer aqueous solution to the end point of the polymerization region, 45 ° C. warm water was sprayed from the lower part of the polymerization belt toward the lower surface of the belt and heated.

  Thus, the water-containing polymer containing sodium polyacrylate was discharged from the rear part of the belt polymerization machine, and the water-containing gel thus obtained was treated in the same manner as in Example 1 to obtain a water-soluble polymer (8). Got. Table 1 shows the results of measuring the physical properties of the water-soluble polymer (8).

[Comparative Example 1]
Polymerization was carried out in the same manner as in Example 1 except that the temperature of the hot water was 38 ° C. to obtain a comparative water-soluble polymer (1). Table 2 shows the results of measurement of physical properties of the comparative water-soluble polymer (1).

[Comparative Example 2]
According to Example 10 of patent document 1 (Unexamined-Japanese-Patent No. 2007-112946), sodium acrylate was superposed | polymerized by the stationary thermal-polymerization method in the casting reaction container. The obtained hydrogel was treated in the same manner as in Example 1 to obtain a comparative water-soluble polymer (2). Table 2 shows the results of measurement of physical properties of the comparative water-soluble polymer (2).

[Comparative Example 3]
According to Example 1 of patent document 2 (Unexamined-Japanese-Patent No. 2009-19181), sodium acrylate was superposed | polymerized by the photopolymerization method using a photoinitiator and ultraviolet irradiation on the belt polymerization machine. The obtained hydrogel was treated in the same manner as in Example 1 to obtain a comparative water-soluble polymer (3). Table 2 shows the results of measurement of physical properties of the comparative water-soluble polymer (3).

  According to the production method of the present invention, it is excellent in workability when dissolving in an aqueous solvent, can easily prepare a high-viscosity aqueous solution, and has a sufficient amount of residual monomer and water-insoluble matter. A reduced water-soluble polymer can be continuously and stably produced efficiently. Therefore, the water-soluble polymer obtained in the present invention is a thickener, adhesive for foods, paints, civil engineering / architecture, food additives for food and feed, feed additives, and other general industrial applications. It can be suitably used in various fields as an agent, flocculant, hygroscopic agent, desiccant, surface modifier and the like.

1: Polymerization belt 2: Rotation drive drum (pulley)
3: Spray nozzle 4: Scraper 5: Near UV lamp 6: Hood 7: Light reduction plate (translucent plate)
8: Water-soluble polymer-containing gel 11: Point of introduction of monomer aqueous solution (starting point of polymerization region)
12: Polymerization start point 13: Polymerization region end point 14: Contact between the rotary drive drum and the belt

Claims (5)

  A method for producing a water-soluble polymer comprising a step of polymerizing a monomer aqueous solution containing a polymerizable unsaturated monomer with a continuous belt polymerization machine, wherein a polymerization region starts from the charging point of the monomer aqueous solution Among these, a method for producing a water-soluble polymer is characterized in that at least a part of a region from the charging point of the monomer aqueous solution to the polymerization starting point is heated to a temperature exceeding 40 ° C. using a heating means.   The production method according to claim 1, wherein in the polymerization region starting from the charging point of the monomer aqueous solution, the region from the starting point to at least 50% is heated.   The manufacturing method according to claim 1 or 2, wherein heating using the heating means is performed at a lower portion of the belt.   The manufacturing method in any one of Claims 1-3 whose pH of monomer aqueous solution is 11.0-13.0.   A water-soluble polymer obtained by the production method according to any one of claims 1 to 4, wherein the 0.2 mass% aqueous solution viscosity is 500 mPa · s or more, the Weisenberg value is 10 mm or less, and / or the thixotropy value is 50. A water-soluble polymer that is:

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