JPH0510386B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing an acrylamide-based polymer stabilized against thermal decomposition. Acrylamide-based polymers are widely used in many industrial fields such as flocculants, paper-making agents, soil conditioners, thickeners, and oil recovery agents. In this way, acrylamide-based polymers have achieved promising results in a wide variety of applications.
However, this polymer has serious drawbacks and may not be able to fully demonstrate its inherent ability. That is, this disadvantage is that this polymer is more susceptible to thermal decomposition than other polymers. For example, even when an aqueous solution of an acrylamide polymer is left at room temperature, it is often observed that the aqueous solution viscosity value is maintained only for a short time, and especially at relatively high temperatures, this tendency of performance deterioration is accelerated. In extreme cases, it may become impossible to use it for the intended purpose. especially,
When injecting crude oil underground in the form of an aqueous solution as a forced recovery agent, the temperature of the underground oil layer is approximately 40 to 100°C, and the injected acrylamide polymer aqueous solution flows underground from the injection well to the production well. Because acrylamide-based polymers remain in the oil layer for a long period of time, ranging from several months to several tens of months, users demand that the quality of acrylamide-based polymers be guaranteed during that period. Therefore, the challenge faced by acrylamide polymer manufacturers is to minimize the deterioration of polymer quality over time in this temperature range. Conventionally, in order to solve such problems, studies have been conducted on anti-deterioration agents. For example, 2-mercaptobenzimidazole and its derivatives are described as effective in JP-A-54-83048, thiourea and its derivatives in JP-A-49-27662, and methoxyphenol etc. are described as effective in JP-A-57-159839. ing. In addition, U.S. Pat.
It is described that 1,3-benzotriazole and 2-(2-hydroxyphenyl)benzotriazole are effective. However, it would be desirable to be able to impart thermal stability to the polymer itself without the addition of such antidegradants. An object of the present invention is to provide a method for producing a water-soluble high molecular weight acrylamide polymer with good thermal stability. The present invention provides the following method for producing a stabilized acrylamide polymer. Acrylamide-based polymers, at least
A method for producing a stabilized acrylamide polymer, which comprises adding 0.5% by weight of a water-soluble vinyl monomer. Acrylamide polymerization processed by the method of the present invention involves acrylamide, methacrylamide or a mixture thereof, or one of these and other copolymerizable vinyl monomers, such as (meth)acrylic acid or its salts, (meth) ) acrylonitrile,
2-acrylamido-2-methylpropanesulfonic acid or its salt, dimethylaminoethyl (meth)acrylate, lower alkyl acrylate, vinylpyridine, acid salt or quaternary salt of dialkylaminoalkyl (meth)acrylate, or dialkylaminoalkyl A polymer, copolymer or copolymer containing a predominant amount of (meth)acrylamide moiety obtained by polymerizing or copolymerizing a mixture with 50% by weight or less of an acid salt or quaternary salt of (meth)acrylamide by a well-known method. It is a mixture of these. It also includes copolymers obtained by converting a part of the amide group into other functional groups through polymer reactions such as hydrolysis, methylolation, or Mannitz formation, such as (meth)acrylamide homopolymers. . The molecular weight of these polymers is not particularly limited, and the effects of the present invention are better expressed in polymers with relatively high molecular weights. Specifically, it is preferable to have a weight average molecular weight of at least 5 million. The weight average molecular weight can be measured by the light scattering method or the intrinsic viscosity [η] method (the value of [η] is determined using a 1N sodium sulfate aqueous solution and an Ubbelohde viscometer or Canon Fuenske viscometer in a constant temperature bath at 30°C. The weight average molecular weight for acrylamide homopolymer is [η]=3.73×10 ^-4 [MW] _0.66 (
This is a value obtained using 1N−NaNO ₃ ) at 30°C. )by. A water-soluble vinyl monomer is added to these acrylamide-based polymers or their aqueous solutions in an amount of at least 0.5% by weight of the polymer, preferably 1.0 to 5.0% by weight. If the amount added is less than 0.5%, the improvement in thermal stability will not be sufficient, and if it exceeds 5.0% by weight, not only will no further improvement in stability be expected, but the viscosity properties per unit active ingredient will decrease. cause The above amount of water-soluble vinyl monomer can be added to the acrylamide polymer or its solution by various methods. One method is to add the water-soluble vinyl monomer of the present invention as it is or as a solution or dispersion to this aqueous polymer solution (which may be in the form of a gel depending on the molecular weight or concentration of the polymer). It is. When this aqueous polymer solution is to be prepared by dissolving a solid polymer, the water-soluble vinyl monomer must be mixed with the solid polymer (gel or powder) in advance using a mixer, blender, etc., or water as a solvent must be prepared in advance. The solution is to dissolve the water-soluble vinyl monomer in the water. The acrylamide polymer aqueous solution may be a solution obtained after completion of polymerization, a solution obtained by concentrating or diluted solution, or a solution obtained by dissolving a solid polymer at the time of use. Water-soluble vinyl monomers include acrylamide, methacrylamide (meth)acrylic acid or its salt, (meth)acrylonitrile, 2-acrylamido-2-methyl-propanesulfonic acid or its salt, dimethylaminoethyl (meth)acrylate, acrylic Examples include acid lower alkyl esters, vinyl pyridine and other water-soluble vinyl monomers. These vinyl monomers can be used alone or as a mixture. Furthermore, the monomer may be of the same type as the monomer used in the polymerization, or may be of a different type. Although the molecular weight of the polymer obtained by the method of the present invention is not particularly limited, the effects of the present invention are better expressed in a polymer having a relatively high molecular weight. Specifically, at least
Preferably, it has a weight average molecular weight of 5 million.
The weight average molecular weight can be measured by the light scattering method or the intrinsic viscosity [η] method (the value of [η] is determined using a 1N sodium sulfate aqueous solution and an Ubbelohde viscometer or Canon Fuenske viscometer in a constant temperature bath at 30°C. In the case of acrylamide homopolymer, the weight average molecular weight is [η] = 3.73×10 ^-4 [MW] _0.66 (30℃, 1N-
This is the numerical value obtained by NaNO ₃ ). )by. Acrylamide-based polymers obtained by the method of the present invention are widely used in fields such as flocculants, paper-making agents, soil conditioners, thickeners, and oil recovery agents.
In these applications, the polymer is used as an aqueous solution. The water used for dissolving this polymer may be city water, industrial water, river water, underground water, or water containing various soluble substances dissolved therein (the type and amount of the dissolved substances are determined based on the acrylamide-based polymer). It goes without saying that the material must not be of a type that would cause the precipitation of An example of such water is “produced water” obtained from oil fields.
and “fresh water”. The concentration of the acrylamide polymer aqueous solution to be stabilized, which is the object of the present invention, varies depending on the molecular weight, but
Approximately 0.01~ for polymers with a molecular weight of 5 million or more
It is usually about 1.0% by weight. The cause of the quality deterioration of acrylamide-based polymers in an aqueous solution state during use is not clear, but it is thought that the deterioration of the polymer is due to radical reactions involving oxidizing substances contained in the polymer or dissolved oxygen. It can be inferred that this radical causes chain transfer to the added water-soluble vinyl monomer, thereby preventing the polymer itself from decomposing. According to the invention, a thermal stability effect is obtained by adding at least 0.5% by weight, preferably 1.0 to 5.0% by weight (based on the polymer) of a water-soluble vinyl monomer to the acrylamide-based polymer. The stabilizing effect of the present invention can be obtained not only near room temperature but also at a high temperature of 90°C. EXAMPLES The present invention will be explained in more detail with reference to Examples below. Example 1 and Comparative Example 1 An acrylamide polymer powder product consisting of 82 mol% acrylamide and 18 mol% Na acrylate obtained using a known radical polymerization method (in a 1N-naCl aqueous solution at a concentration of 0.1% by weight, 25℃Brutskfield rotational viscometer B8L type with adapter 60rpm
6.0cps under conditions of “Texaco Redu
After preparing a 0.1% by weight aqueous polymer solution, the viscosity of this solution was measured to determine the initial viscosity (AO), and a portion of this aqueous solution was taken to prepare the water-soluble vinyl monomer of the present invention. Add it, put it in a heat-resistant test bottle, seal it, measure the viscosity (A) after treatment at 90℃, and show the change over time as viscosity retention percentage (A/Ao x 100).
1 and Table 2. Note that Table 1 also shows the viscosity retention percentage of those without the addition of water-soluble vinyl monomer. Composition of “Texaco Redu Water” NaCl 0.1714 (wt%) CaCl ₂ 0.0039 (〃) Na ₂ SO ₄ 0.0083 (〃) MgCl ₂ 0.00636 (〃) NaHCO ₃ 0.1553 (〃) Na ₂ CO ₃ 0.00378 (〃)

【table】

[Table] As is clear from the results in Table 1, especially
The addition of 1.0% by weight or more of acrylamide and sodium acrylate improves the thermal stability of acrylamide-based polymers. Example 2 Example 1 was repeated except that the water-soluble vinyl monomer used in Example 1 was replaced with various vinyl monomers shown in Table 2.

[Table] As is clear from Table 2, the addition of water-soluble vinyl monomers other than the constituent monomers of the polymer also
Contributes to improving the thermal stability of acrylamide polymers.

Claims (1)

[Claims] 1. A method for producing a stabilized acrylamide polymer, which comprises adding at least 0.5% by weight of a water-soluble vinyl monomer to the acrylamide polymer. 2 The water-soluble vinyl monomer is added to the polymer in a proportion of 1.0 to
The method according to claim 1, wherein 5.0% by weight is added. 3. The method according to claim 1 or 2, wherein the water-soluble vinyl monomer is added to the aqueous solution of the acrylamide polymer.