JPH07242703A - Polymerization of acrylamide monomer - Google Patents

Abstract

PURPOSE:To obtain a polymer of a high molecular weight and a high rate of dissolution by (co)polymerizing acrylamide in an aqueous medium in the presence of a specific organic peroxide, a polyethylenepolyamine and an azoic initiator at a specific pH. CONSTITUTION:Acrylamide alone or a mixture of 25mol% or more of acrylamide with other monomer(s) is polymerized in an aqueous medium in a system of insufficient polymerization heat removal in the presence of 0.5-50ppm of an organic hydroperoxide with a 10-hr half-life temperature of 150 deg.C or above, 1-50ppm of a polyethylenepolyamine as a redox initiator, and 1-1,000ppm of an azoic initiator with a 10-hr half-life temperature of 30-100 deg.C, based on the reaction mixture, at pH7-10.5. The polymerization is initiated at 0-25 C and the temperature difference upon completion of the polymerization is 25-100 deg.C. tert-Butyl hydroperoxide, etc., are used as the organic hydroperoxide, triethylenetetramine, etc., as the polyethylenepolyamine, and azobisisobutyronitrile, etc., as the azoic initiator. The polymer is stable when dried.

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention provides an acrylamide polymer having a high molecular weight and good solubility, which is suitable for a flocculant, a papermaking sticky agent, a papermaking retention improver, and a petroleum recovery thickener. And a method for polymerizing an acrylamide-based monomer.

[0002]

2. Description of the Related Art Most of high molecular weight polyacrylamides or copolymers of acrylamides used for flocculants have a molecular weight of more than 10 million. As a means for obtaining such a high molecular weight polymer, a monomer is polymerized in an aqueous solution, the obtained aqueous gel is crushed by a meat grinder type extruder to be shaped into granules, and dried with hot air. Is common.

The monomer concentration in this aqueous solution polymerization is
From the viewpoints of the production amount per volume of the polymerization container and the drying load of the aqueous gel, the higher one is preferable. However, in the case of a high molecular weight acrylamide polymer, the viscosity of the system becomes very high with the progress of the polymerization reaction, and for example, an aqueous gel having a polymer concentration of 25% by weight becomes a raw rubber-like elastic body. Therefore, since stirring is practically impossible, the heat of polymerization is not removed and the temperature is often left to rise.For example, when the concentration of the charged acrylamide monomer is 25% by weight, the temperature rise of the reaction system is about 75%. Reaches ℃. Therefore, in order to keep the temperature of the system at the completion of the polymerization in an aqueous solution polymerization below 100 ° C and to adopt the highest possible monomer concentration in order to increase productivity, the polymerization initiation temperature must be as low as 0 to 10 ° C. I don't get it.

As an initiator used in such a wide temperature range, a redox type initiator has been favorably used because of its low activation energy. However, when attempting to synthesize a high molecular weight polymer, lowering the initiator concentration leads to an increase in the content of unreacted monomer, and when the monomer concentration is high, the final temperature due to the heat of polymerization increases and the redox reaction increases. A crosslinking reaction due to a highly-reactive radical generated by homolysis of an oxidant component of the system initiator, for example, persulfate, will occur at the same time, resulting in a decrease in the solubility of the resulting polymer.

In order to solve such a problem, Japanese Patent Publication Sho
In Japanese Patent Publication No. 47-26430, an azo compound is used in combination with an oxidation-reduction initiator in an amount insufficient to complete the polymerization of a monomer in an aqueous solution by itself, and polymerization in a high temperature range is performed by a redox initiator. It is proposed to avoid azo compounds.

On the other hand, in JP-B-60-8688, an azo initiator is used in combination with a sufficient amount of a redox initiator (the amount which can complete the polymerization by itself) in the presence of 2-mercaptobenzimidazole. Thus, at a low temperature in the initial stage of polymerization and at a high monomer concentration, the radicals derived from the redox initiator are generated in a high temperature range where an undesirable reaction by the redox initiator becomes active while ensuring a sufficient polymerization rate. Is inactivated with 2-mercaptobenzimidazole and the polymerization is completed with an azo-based initiator.

However, even in these methods, it is difficult to sufficiently reduce the overlap between the polymerization region of the redox type initiator and the polymerization region of the azo type initiator, and the decrease of the molecular weight is caused in the polymerization region in which both the initiators are involved. Therefore, it was still difficult to obtain a high molecular weight polymer.

On the other hand, the raw rubber-like aqueous gel obtained by aqueous solution polymerization is shaped into particles with a diameter of several mm by a meat grinder type extruder, dried with hot air at a temperature of several hundreds of tens of degrees, and ground to give a polymer. However, in this drying step, there is a problem that the polymer is considered to be partially crosslinked due to the residual oxidant component and the solubility of the obtained polymer is lowered.

[0009]

DISCLOSURE OF THE INVENTION The present invention is directed to a production method involving the above-mentioned conventional techniques, Japanese Patent Publication No. 47-26430 and Japanese Patent Publication No. 60-8688, that is, a system in which the heat of polymerization is insufficiently removed, or In the manufacturing method in which an adiabatic system is subjected to aqueous solution polymerization at a high monomer concentration, and the resulting aqueous gel is heated and dried to obtain an acrylamide polymer, it has a higher molecular weight and better solubility than these conventional techniques. The subject is to obtain an acrylamide polymer.

[0010]

The present invention is directed to the initiation of a redox system comprising, as a component, an oxidizer which is volatile in the polymerization on the low temperature side and has a very high decomposition temperature in the above-mentioned polymerization process accompanied by an increase in temperature. The azo initiator shares the high temperature side with the agent, and the active temperature range of the redox initiator is adjusted to pH.
It is intended to solve all of the above problems by reducing by adjustment and appropriately controlling the overlap between the temperature range and the temperature range in which the azo initiator is active.

That is, the present invention removes heat of polymerization of acrylamide alone or a monomer mixture of 25 mol% or more of acrylamide and at least one monomer copolymerizable therewith in an aqueous medium. When the polymerization reaction is carried out in an insufficient system, the decomposition half-life is 10 for the reaction mixture.
Organic hydroperoxide with a temperature of 150 ℃ or higher
A redox initiator consisting of 0.5 to 50 ppm and polyethylene polyamine 1 to 50 ppm and an azo initiator having a half-life of 10 hours at a temperature of 30 to 100 ° C. and 10 to 1000 ppm are present.
A method for polymerizing an acrylamide-based monomer, which comprises polymerizing at a pH of 7 to 10.5.

The polymerization initiator system of the present invention exhibits a peculiar polymerization behavior depending on pH, and the adjustment of this pH is particularly important. That is, when the pH of the charged solution for polymerization is less than 7, the polymerization is almost completed only with this redox initiator, and since it is an adiabatic system, a temperature rise commensurate with the heat of polymerization is observed. However, when the pH is raised above 7, the polymerization does not complete and stops halfway. That is, the temperature rise is stopped at a temperature lower than the temperature reached when the polymerization is completed,
The temperature at which the temperature rise stops becomes lower as the pH rises. On the other hand, the initial polymerization rate until the termination of polymerization is p
It rises with an increase in H and reaches a peak at around pH 10.5. When an azo initiator exhibiting polymerization activity is used in combination from around the temperature at which the polymerization by the redox initiator is stopped, the system temperature rises to a temperature at which the polymerization is completed at any pH. This peculiar phenomenon due to pH has not been reported so far and is completely unexpected.

Although the reason for this is not clear, the protonation state of the polyalkylene polyamine changes with pH, and the rate at which acrylamide gradually Michael-adds to the polyalkylene polyamine during the temperature rising process of the polymerization is pH. It is presumed that the change may be the cause.

The present invention skillfully utilizes such a unique phenomenon to specify the polymerization conditions under which a polymer having a high molecular weight and good solubility can be obtained. Usually, at a low temperature and a high monomer concentration at the initial stage of polymerization, a polymer having a very high molecular weight is produced, and the solubility of the polymer is often poor. It is presumed that this is partly because a polymer having an abnormally high molecular weight is produced. According to the present invention, a sufficient polymerization rate can be maintained by performing the polymerization in the range of pH 7 to 10.5,
Moreover, in the process of gradually raising the temperature, the polymerization by the redox initiator is stopped at a certain temperature (polymerization rate) before the completion of the polymerization, and the subsequent polymerization in a high temperature region overlaps with the polymerization by the redox initiator. Since it can be handed over to the azo initiator in a small amount, an abnormally high molecular weight polymer is not produced and the crosslinking reaction due to the oxidant component of the redox initiator does not occur simultaneously. . Therefore, it is possible to obtain a high-molecular weight polymer having good solubility and, surprisingly, in a shorter time than ever.

The acrylamide monomer in the present invention refers to a monomer mixture consisting of acrylamide alone or 25 mol% or more of acrylamide and at least one monomer copolymerizable therewith. Examples of monomers copolymerizable with acrylamide include acrylic acid, methacrylic acid, and 2
-Acrylamido-2-methylpropanesulfonic acid and salts thereof, dimethylaminoethyl methacrylate,
Diethylaminoethyl methacrylate and quaternary ammonium salts thereof, water-soluble monomers such as methacrylamide, and acrylonitrile, styrene, lower alkyl esters of acrylic acid and methacrylic acid, etc., as long as they do not impair the water-solubility of the resulting polymer. Can also be used.

The system in which the heat of polymerization is insufficiently removed in the present invention is a system in which the heat of polymerization is not sufficiently removed including a complete adiabatic system, and the polymerization reaction is carried out in a completely adiabatic polymerization vessel, or In a polymerization vessel in which the heat of polymerization is not sufficiently removed, the above-mentioned monomer
It is carried out on an aqueous solution of 10 to 70% by weight, preferably 10 to 35% by weight. The complete heat-insulating container referred to here is a container that does not exchange heat between the inside and outside of the polymerization system, but it is a container such as a Dewar bottle or a container with a heating jacket and the internal temperature The temperature may be externally heated from the jacket following the rise in the temperature to reduce the temperature difference between the central portion and the peripheral portion of the polymerization container as much as possible. Further, the polymerization container in which the heat of polymerization is not sufficiently removed refers to a container kept warm by a substance or a heat insulating material which hinders heat conduction, but it may be a plastic container. The present invention provides a monomer concentration,
Although it depends on the composition and the degree of removal of the heat of polymerization, it is particularly suitable when the polymerization initiation temperature is 0 to 25 ° C. and the temperature difference in the reaction system between the initiation of polymerization and the completion of polymerization is 25 to 100 ° C. .

As the organic hydroperoxide, which is the oxidant component of the redox initiator, the temperature at which the half-life is 10 hours is 150, considering that the harmful radicals are rarely generated even at the maximum temperature during drying. It exceeds ℃.
Examples of such compounds include tert-butyl hydroperoxide, cumene hydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide, 1,1,1.
3,3-tetramethylbutyl hydroperoxide and the like.

As the polyethylene polyamine as the reducing agent component, triethylene tetramine, tetraethylene pentamine and pentaethylene hexamine are preferable. You may use these individually or in mixture of 2 or more types.

The amount of the reducing agent and the oxidizing agent is 0.5 ppm to 50 ppm with respect to the polymerization charge composition liquid, and the ratio is 1:10 to weight ratio.
Use in the range of 10: 1.

Iron is often used in combination with the redox initiator, but in the present invention, polymerization takes place without addition of iron. However, it is preferable to add a water-soluble salt of iron within a range of 1 ppm or less as iron to a composition containing a polymerization charge, in which a good result is obtained.

Suitable azo initiators have a half-life of 10 hours at a temperature of 30 to 100 ° C, preferably 40 to 80 ° C. However, since it is an aqueous solution polymerization, it is desirable that the necessary amount is uniformly dissolved or dispersed in water. For example,
2,2′-azobis (2-amidinopropane) 2 hydrochloride, 4,4′-azobis (4-cyanovaleric acid) and the like, and azobisisobutyronitrile can also be used.

The amount of the azo initiator is in the range of 10 to 1000 ppm with respect to the polymerization charge composition liquid.

The pH of the polymerization charge liquid is in the range of pH 7 to 10.5, preferably pH 8 to 1 in consideration of the temperature at which the azo initiator to be used becomes active and the molecular weight of the polymer produced and the solubility of the polymer. You can search for the optimum point in the range of 10. As described above, when the overlap between the polymerization temperature range of the redox initiator and the polymerization temperature range of the azo initiator is large, the molecular weight does not become high. The transfer to the system initiator does not proceed smoothly, the polymerization time becomes long, and the solubility deteriorates.

Further, since amine is used as the reducing agent component, the pH is changed by adding the initiator. for that reason,
PH of carbonate, hydrogencarbonate, boric acid, etc.
It is desirable to add a buffer.

The polymer according to the present invention has a sufficiently high dry stability, and is a dry insolubilizing agent which is conventionally known, for example, 2-mercaptobenzimidazole, thiodipropionic acid, phosphorous acid, nitrilotris. The combined use of propionamide, hindered phenols and the like can further enhance the drying stability. After the polymerization, the obtained aqueous gel may be dried, pulverized and the like according to a conventional method.

[0026]

As described above, according to the present invention, as compared with the conventional production method, insolubilization of the polymer due to crosslinking or the like is less likely to occur even during the polymerization and under severe drying conditions, and the product weight is high even though it has a high molecular weight. A polymer having a high dissolution rate of the coalesced powder can be obtained in a short polymerization time.

[0027]

EXAMPLES The present invention will be specifically described below with reference to examples. Parts are parts by weight.

Reference Examples 1-10 Water 77 parts, acrylamide 23 parts, sodium acetate
0.06 part was dissolved, and the pH was adjusted to a predetermined value while cooling to 10 ° C when transferred to a Dewar bottle. This was transferred to a Dewar bottle equipped with a thermometer, the system was replaced with nitrogen, and then tert-butyl hydroperoxide 0.003
Part, tetraethylenepentamine 0.003 part, iron pyrophosphate
0.0002 parts was added and the temperature in the center of the Dewar bottle was recorded over time. Table 1 shows the relationship among pH, final temperature / time, and polymerization rate.

[0029]

Examples 1-5 and Comparative Examples 1-2 pH 6, 7, 8, 9, 10, 10.5 and 11 in the above reference examples.
In the example of, the azo initiator, 4,4′-azobis (4-
(Cyanovaleric acid) was added in an amount of 0.05 parts to adjust the pH, and the procedure was the same as in Reference Example. After the polymerization, the aqueous gel was crushed into particles having a diameter of several mm with a meat grinder, dried at 60 ° C. for 16 hours, and crushed with a Wiley crusher to a particle size of 2 mm or less. The obtained polymer powder was dissolved in 4% saline to a concentration of 1%, and the Brookfield viscosity (hereinafter, abbreviated as viscosity in 4% saline) was measured. In addition, in 500 g of pure water, 0.1%
After dissolving to a concentration, the mixture was filtered through a wire mesh of 80 mesh to observe the dissolved state and insoluble matter. The results are shown in Table 2.

Table 2 ──────────────────────────────────── Example pH reached temperature / time 4% Saline viscosity Viscosity Dissolved state Insoluble Swelling gel (℃ / min) (cp) ─────────────────────────────────── ── Comparative Example 1 6.0 77/216 Not measurable Approximately 70 times Swelling without dissolution ─────────────────────────────── ────── Example 1 7.0 77/112 3,300 Slightly poor 20g Example 2 8.0 77/77 3,500 Good 5g Example 3 9.0 77/66 3,900 Good None Example 4 10.0 77/109 4,000 Good 10g Example 5 10.5 77/183 4,200 Somewhat poor 35 g ──────────────────────────────────── Comparative example 2 11.0 77 / 226 Not measured, defective 120g ─────────────────────── ────────────

Example 6 60 parts of water, 4.1 parts of acrylic acid and 18.9 of acrylamide
Part of the solution and pour with sodium hydroxide solution while cooling.
H was set to 9.5. Example 1 with 100 parts of water
Except that 0.06 parts of azobisamidinopropane dihydrochloride was used in place of 4,4'dicyanovaleric acid of ~ 5.
It carried out like Example 1-5. The viscosity of the obtained acrylamide / acrylic acid copolymer in saline was 3,500 cp, and it was completely dissolved in pure water at a concentration of 0.1% for 30 minutes by stirring.

Comparative Example 3 23 parts of acrylamide, 0.03 part of 2-mercaptobenzimidazole and 0.02 part of 4,4'-azobis (4-cyanovaleric acid) were dissolved in 77 parts of water and adjusted to pH7.
Potassium persulfate 0.003 in a Dewar bottle under nitrogen at 10 ° C
And 0.045 parts of dimethylaminopropionitrile were added to carry out polymerization. A polymer powder was obtained from the obtained aqueous gel in the same manner as in Examples 1 to 5. The viscosity of this in 4% saline is 2,6
It was 00cp.

Example 7 and Comparative Example 4 The same procedure as in Example 3 was carried out except that 0.05 part of thiodipropionic acid was added to the polymerization charge solution to adjust the pH under the conditions of Example 3. The viscosity of the obtained polymer in 4% saline solution is
It was 3,350 cp. The polymer powder obtained here and the polymer powder obtained in Comparative Example 3 were heated in a hot air dryer at 100 ° C. and sampled at regular intervals to obtain 500 g of pure water.
In the medium, 0.1% concentration was used for stirring and dissolution for 4 hours, followed by filtration through an 80-mesh wire net to measure the weight of the insoluble swollen gel. The results are shown in Table 3.

Table 3 ──────────────────────────────── Insoluble swollen gel (g) ─────── ───────────────────────── Heating time (hr) 0 3 6 9 12 ─────────────── ───────────────── Example 7 Sample of this Example <1 <1 <1 <1 2 Comparative Example 4 Sample of Comparative Example 3 2 4 10 16 20 ─── ─────────────────────────────

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yu Nagahara 10-1 Daikokucho, Tsurumi-ku, Yokohama-shi, Kanagawa Nitto Chemical Industry Co., Ltd. Central Research Laboratory

Claims (5)

[Claims] 1. Acrylamide alone or 25 mol%
The above acrylamide and a monomer mixture consisting of at least one of the monomers copolymerizable therewith, in an aqueous medium,
When carrying out the polymerization reaction in a system in which the heat of polymerization is not sufficiently removed, the temperature at which the decomposition half-life becomes 10 hours is 1 for the reaction mixture.
A redox initiator consisting of 0.5 to 50 ppm of organic hydroperoxide at 50 ° C or higher and 1 to 50 ppm of polyethylene polyamine and an azo initiator having a half-life of 10 hours at a temperature of 30 to 100 ° C and 10 to 1000 ppm are present, and the pH is set to 7 A method for polymerizing an acrylamide-based monomer, characterized in that the polymerization is performed at -10.5. 2. The temperature at the start of the polymerization is 0 to 25 ° C., and the temperature difference in the reaction system at the start of the polymerization and at the completion of the polymerization is 25 to 25 ° C.
The method for polymerizing an acrylamide monomer according to claim 1, which is 100 ° C. 3. The organic hydroperoxide is selected from tertiary butyl hydroperoxide, cumene hydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide and 1,1,3,3-tetramethylbutylhydroperoxide. The method for polymerizing an acrylamide monomer according to claim 1, wherein 4. The method for polymerizing an acrylamide monomer according to claim 1, wherein the polyethylene polyamine is selected from triethylene tetramine, tetraethylene pentamine and pentaethylene hexamine. 5. The azo initiator is selected from 2,2′-azobis (2-amidinopropane) dihydrochloride, 4,4′-azobis (4-cyanovaleric acid) and azobisisobutyronitrile. The method for polymerizing an acrylamide monomer according to claim 1, wherein