JPH0410882B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a water-soluble polymer having good water solubility and high molecular weight. For example, acrylamide polymers, acrylamide-based copolymers of acrylamide and other polymerizable monomers, or alkaline hydrolysates thereof have traditionally been used as paper strength agents, thickeners, soil conditioners, and wastewater. Widely used as a processing agent or crude oil recovery agent. Methods for producing these acrylamide-based water-soluble polymers include bulk polymerization, suspension polymerization, emulsion polymerization, and solution polymerization, but essentially high molecular weight polymers are mainly used, so in general, In most cases, the aqueous solution polymerization method is used. The molecular weight is extremely high due to the aqueous solution polymerization method.
In order to obtain a polymer with good water solubility, it is necessary to prevent the crosslinking reaction in the polymerization stage, that is, the three-dimensional network reaction as much as possible. Care must also be taken to prevent crosslinking reactions during the drying stage. The crosslinking reaction of these polymers is accelerated as the concentration during the polymerization reaction increases, and as the temperature during the drying stage increases, so relatively little effort is required to prevent these undesirable crosslinking reactions. Polymerization under mild conditions, such as relatively low monomer concentrations or drying under mild temperature conditions, may be desirable. However, in recent years, these polymers are desired to be in powder form rather than in aqueous solutions;
The above-mentioned conditions in which the crosslinking reaction is difficult to occur are economically undesirable. Therefore, we aim to reduce utility costs at the powder stage by polymerizing at the highest monomer concentration possible.
In addition, technological development is underway to prevent the crosslinking reaction. Techniques are being developed to prevent crosslinking of polymers, such as by methods of preventing abnormal increases in polymer concentration. In view of the above circumstances, the present inventors carried out polymerization at the highest possible monomer concentration, and conducted extensive research in order to produce a water-soluble polymer with an extremely high molecular weight and excellent water solubility. As a result, in a method for producing a water-soluble high molecular weight polymer by holding a water-soluble vinyl monomer aqueous solution in a thin layer on a solid support and polymerizing it, the monomer aqueous solution no longer flows freely. At the time, it was discovered that the above object could be achieved by coating the surface of a polymer gel with a compound obtained by alkylene oxide addition that is sparingly soluble or essentially insoluble in water and then continuing the polymerization. , completed the invention. That is, in the present invention, when the aqueous monomer solution no longer flows freely, the polymer gel is coated with a compound obtained by addition of an alkylene oxide that is sparingly soluble or essentially insoluble in water. It is possible to suppress the abnormally high concentration caused by evaporation of the monomer aqueous solution due to the heat generated as the polymerization progresses. It is possible to prevent a decrease in the rate and degree of polymerization, and also to prevent the polymer surface from dissolving or becoming slimy due to condensed water, which is often seen in the humid atmosphere used in conventional methods. In addition, the compound obtained by adding alkylene oxide, which is poorly soluble or essentially insoluble in water and coated on the polymer surface, eliminates adhesion of particles to each other during the drying stage, improves drying efficiency, and breaks the polymer gel. It can sometimes be a commonly used lubricant or antiblocking agent. Examples of the water-soluble vinyl monomer used in the present invention include water-soluble vinyl monomers such as acrylamide, methacrylamide, acrylic acid, methacrylic acid, vinyl sulfonic acid, acrylamide-methylpropylsulfonic acid, and itaconic acid; salts of (meth)acrylic acid dialkylaminoalkyl esters, acidic salts thereof or quaternary products thereof, dialkylaminoalkylacrylamides, acidic salts thereof or quaternary products thereof, diallylamine acid salts, diallyldialkylammonium salts, etc. Examples include, but are not limited to, diallylamines.
These may be used alone or in combination of two or more. The water-soluble vinyl monomers include monomers that are essentially insoluble in water, such as acrylonitrile, (meth)acrylates, vinyl acetate, to the extent that the resulting polymer is water-soluble. Hydrophobic monomers such as styrene can be blended. Examples of the solid support used in the present invention include, but are not limited to, containers in the shape of a dish, square, or cylinder, or a movable belt. Examples of compounds obtained by addition of alkylene oxide that are sparingly soluble or essentially insoluble in water used in the present invention include aliphatic alcohols having 1 to 20 carbon atoms, alkylphenols such as nonylphenol, octylphenol, and dodecylphenol. fatty acids having 4 to 22 carbon atoms such as lauric acid, myristic acid, palmitic acid, stearic acid, and oleic acid; polyols such as glycerin, trimethylolpropane, pentaerythritol, and sorbitol; or partial fatty acids of these polyols. Examples include, but are not limited to, compounds that are poorly soluble or essentially insoluble in water, such as esters to which alkylene oxide is added. Further, these may be used alone or in combination of two or more. The molecular weight of the compound obtained by the alkylene oxide addition is not particularly limited, but a molecular weight of about 500 to 20,000 is usually used. When using such compounds, those having high fluidity may be used as they are, or may be diluted with a solvent or made into an aqueous dispersion. On the other hand, those with low fluidity, such as those in the form of grease or those with high viscosity, may be dissolved in a diluent such as oil or alcohol, or may be used as an aqueous dispersion. The amount of the compound to be used may be sufficient to cover the entire surface of the polymer gel, and generally the object of the present invention can be achieved even if a very thin film is formed. Generally 0.01-5% based on polymer gel
(wt%, the same applies hereinafter), preferably 0.1 to 1.0%. If the amount used exceeds 5%, the water solubility of the polymer is impaired, and when an aqueous solution is prepared, cloudiness or suspension may occur, or the alkylene oxide addition compound used may float on the surface of the aqueous solution. It's dull and undesirable. The alkylene oxide is a compound containing an epoxy ring, such as propylene oxide, butylene oxide, or epichlorohydrin, and as long as the compound produced by addition polymerization is poorly soluble or essentially insoluble in water, ethylene Alkylene oxide, which is highly hydrophilic, such as oxide, may be used. In the present invention, an aqueous solution is prepared from the water-soluble vinyl monomer, held in a thin layer on the solid support, and then polymerized to produce a water-soluble high molecular weight polymer. The concentration of an aqueous solution prepared from a water-soluble vinyl monomer is related to the solubility of the monomer used, and although it cannot be limited, it is desirable to make it as high as possible. For example, in the case of acrylamide alone, it contains 20 to 50%, preferably 25 to 45%, of acrylamide and other anionic or nonionic vinyl monomers such as sodium acrylate, acrylic acid alkyl ester, acrylonitrile, etc. In some cases, it is usually 20 to 60%, preferably 30 to 50%. In addition, in the case of a single cationic water-soluble vinyl monomer such as an acid salt or a quaternized product of dialkylaminoalkyl methacrylate,
Usually 65-85%, preferably 70-80%. When it contains acrylamide and the above cationic water-soluble vinyl monomer, it is usually 50 to 85%, preferably
It is 60-80%. The aqueous solution is held in a thin layer on the solid support, and the thickness of the thin layer is usually about 3 to 30 mm, preferably about 5 to 15 mm. When the thickness is less than 3 mm, productivity becomes extremely poor and it is economically unfavorable. Moreover, if it exceeds 30 mm, it becomes difficult to remove the polymerization heat generated in the polymerization step, and the water solubility of the resulting polymer may be significantly reduced, which is not preferable. The aqueous monomer solution held on the solid support can be prepared by thermal polymerization using a thermal polymerization initiator such as a known persulfate or an azo initiator, or by a known persulfate/amine or persulfate/ redox polymerization method using redox polymerization initiator such as sulfite;
Polymerization is carried out by conventional methods such as photopolymerization using a photopolymerization initiator such as benzoin or benzoin alkyl ether or radiation polymerization until it no longer flows freely. At that point, an aqueous dispersion of the compound obtained by alkylene oxide addition, which is sparingly soluble or essentially insoluble in water, is applied or sprayed to coat the polymer gel, which is no longer free-flowing. It is supplied by methods such as Thereafter, polymerization is continued to produce a water-soluble polymer with good water solubility and high molecular weight. In addition, in the polymerization stage,
Supplying hot or cold water from the bottom of the solid support,
It is preferred to control the heat generated by polymerization. In addition, the monomer aqueous solution no longer flows freely,
Until coating with the above compound, it is necessary to shield the polymerization atmosphere with an inert gas in order to remove dissolved oxygen in the monomer aqueous solution and oxygen in the polymerization atmosphere. After that, the film can block the outside air, so the introduction of inert gas can be reduced to a very small amount or stopped. Polymerization usually requires about 30 to 180 minutes. When the polymerization is carried out by ultraviolet irradiation, there is almost no induction time until the polymerization starts, and since the polymerization starts almost simultaneously with the ultraviolet irradiation, the monomer aqueous solution does not flow freely quickly. Therefore, the alkylene oxide adduct used in the present invention can be applied and coated almost simultaneously with the monomer aqueous solution, which is preferable because the operation is simple. Furthermore, the time required for polymerization is shorter and more effective than thermal polymerization. Next, the manufacturing method of the present invention will be explained based on Examples. Examples 1 to 4 and Comparative Examples 1 to 2 A polymerization apparatus with a jacket (length 200 mm, width 300 mm, height 50 mm) was installed in a small box-shaped room that could be sealed with nitrogen gas.
mm square container (without top lid) was installed. 150 g of acrylamide from which dissolved oxygen was sufficiently removed using nitrogen gas in a deoxidizing tank (cylindrical type with a capacity of 1);
38g of acrylic acid, 20g of caustic soda in deionized water
Add 5 ml of 5% potassium persulfate aqueous solution and 5 ml of 5% sodium sulfite aqueous solution to the monomer aqueous solution dissolved in 275 g, continue deoxidizing with nitrogen gas for several minutes, and then place in a room sealed with nitrogen gas. It was introduced into the installed polymerization apparatus and polymerization was started. Water at 25°C was passed through the jacket. Polymerization started after about 10 minutes, and the aqueous monomer solution gradually thickened. When 15 minutes had passed after the start of polymerization, the monomer aqueous solution was in a state of gradual fluidity. At this point, the entire surface of the polymer gel is coated with a compound obtained by alkylene oxide addition that is sparingly soluble or essentially insoluble in water (hereinafter referred to as alkylene oxide adduct) shown in Table 1. After coating the nitrogen gas as thinly as possible, the introduction of nitrogen gas was stopped and the polymerization was continued until 180 minutes after the start of polymerization.
Polymerization was completed within minutes. After observing the obtained polymer gel, it was cut into small pieces using a meat grinder and dried at 80°C for 120 minutes to obtain a powder product. The polymerization rate, intrinsic viscosity, and water solubility of the obtained powder product were measured by the following methods. The results are shown in Table 1. (Polymerization rate) Measured by KBrO ₃ method. (Intrinsic viscosity) Using a Canon Fuenske viscosity tube, 1N-
Measured in NaCl solution at 30°C. (Water solubility) Collect 0.1g of the obtained powdered polymer and add it to 100% of distilled water.
g, put it in a magnetic stirrer (approximately
500 rpm) for 5 hours to dissolve, and visually determine the amount of undissolved swelling substance present in the solution,
Determine water solubility. The sorbitol/butylene oxide/propylene oxide adduct in Table 1 is a block adduct, and the ratio of butylene oxide/propylene oxide is a weight ratio. Examples 5 to 8 and Comparative Examples 3 to 4 Examples 1 to 4 and Comparative Examples 1 to 2, except that the introduction of nitrogen gas was not stopped after applying the alkylene oxide adduct. 5-8 and Comparative Examples 3-4 Polymer gels were produced and observed in the same manner as in Examples 1-4 and Comparative Examples 1-2, respectively. The result is the first
Shown in the table.

【table】

[Table] Examples 9 to 12 and Comparative Examples 5 to 6 Instead of the monomer aqueous solution used in Examples 1 to 4 and Comparative Examples 1 to 2, N at a concentration of 75% was adjusted to PH4 with a 10% aqueous hydrochloric acid solution. ,N,N-Trimethylaminoethyl methacrylate chloride aqueous solution of 500 ml was used. In Examples 9 to 12 and Comparative Examples 5 to 6, polymer gels were produced in the same manner as in Examples 1 to 4 and Comparative Examples 1 to 2, respectively. After observation, the mixture was ground into small pieces using a meat grinder, dried at 80°C for 120 minutes to obtain a powder, and the polymer properties were measured. The results are shown in Table 2. Examples 13-16 and Comparative Examples 7-8 Examples 9-12 and Comparative Examples 5-6, except that the introduction of nitrogen gas was not stopped after applying the alkylene oxide adduct. In Examples 13 to 16 and Comparative Examples 7 to 8, polymer gels were produced and observed in the same manner as in Examples 9 to 12 and Comparative Examples 5 to 6, respectively. The results are shown in Table 2.

【table】

【table】

Claims (1)

[Claims] 1. A method for producing a water-soluble high molecular weight polymer by holding a water-soluble vinyl monomer aqueous solution in a thin layer on a solid support and polymerizing the monomer aqueous solution freely. At the point at which it stops flowing, the surface of the polymer gel is coated with a compound obtained by addition of an alkylene oxide that is sparingly soluble or essentially insoluble in water, and then the polymerization is continued. A method for producing a water-soluble polymer with good quality and high molecular weight. 2. The method according to claim 1, wherein the water-soluble vinyl monomer is acrylamide or a water-soluble vinyl monomer containing acrylamide as a main component. 3. The method according to claim 1, wherein the polymerization is carried out by irradiation with ultraviolet rays.