JPH0586409B2 - - Google Patents

Description

[Detailed description of the invention]

Industrial Application Field: The present invention relates to a method for producing polymer emulsions. More specifically, the present invention relates to a method for producing a polymer emulsion in which specific monomers are polymerized in a specific state. Conventional technology and its problems: Conventionally, as a temperature-sensitive substance that causes cloudiness in an aqueous solution by heating, for example, (1) a certain acrylamide or methacrylamide derivative (hereinafter abbreviated as (meth)acrylamide derivative);
(2) polymers having an ether bond in the main chain; and (3) polymers having an ether bond in the side chain. However, a method for producing a polymer emulsion that is temperature sensitive and provides a high molecular weight polymer has not been found. Means for solving the problem: The present inventors have intensively studied a method of producing a polymer by polymerizing in an emulsion state using the temperature sensitivity of a thermosensitive monomer that becomes cloudy when heated in an aqueous solution. As a result, it was discovered that by using a specific (meth)acrylamide derivative, polymerization can be suitably carried out in an emulsion state, and the present invention was achieved. That is, the present invention is based on the general formula

[Chemical formula] (In the above formula, R ₁ is hydrogen or a methyl group, and R ₂ is a propyl group or a butyl group.) A monomer represented by the following formula is dissolved in water and at a concentration that causes cloudiness At a temperature higher than
This is a method for producing a polymer emulsion characterized by homopolymerization, copolymerization, or copolymerization with other copolymerizable monomers. The monomer whose aqueous solution is temperature-sensitive and which is the object of the present invention is a (meth)acrylamide derivative represented by general formula (1) (hereinafter referred to as a temperature-sensitive monomer). Specifically, N-n-propylacrylamide, N-isopropylacrylamide, N
-n-propylmethacrylamide, N-isopropylmethacrylamide, N-n-butylacrylamide, N-sec-butylacrylamide, N-
These are tert-butyl acrylamide, N-n-butyl methacrylamide, N-sec-butyl methacrylamide, and N-tert-butyl methacrylamide. These (meth)acrylamide derivatives become cloudy when heated in an aqueous solution and exhibit temperature sensitivity. Hereinafter, the temperature at which clouding occurs will be referred to as the cloud point. The cloud point varies depending on the type of derivative, but is 0 to 90℃.
In general, N-propyl substituted products have a higher cloud point than N-butyl substituted products. In addition, the cloud point changes depending on the concentration in the aqueous solution.
Generally, the higher the concentration, the lower the cloud point. Also,
Since the N-propyl substituted product has a higher solubility in water than the N-butyl substituted product, the cloud point can be controlled over a wide temperature range. Furthermore, an aqueous solution that has become cloudy due to heating can be returned to a transparent aqueous solution by cooling it, and this process can be repeated any number of times. Next, as other monomers that can be copolymerized with the temperature-sensitive monomer described above, one or more of lipophilic monomers, hydrophilic monomers, and ionic monomers can be used. Examples of the lipophilic monomer include N,N-diethylmethacrylamide, N,N-di-n-propylacrylamide, -methacryloylpyrrolidine,
N-acryloylpiperidine, N-methacryloylpiperidine, N-acryloylhexahydroazepine, N-methacryloylhexahydroazepine, N-n-hexylacrylamide, N-n-
Hexylmethacrylamide, N-n-octylacrylamide, N-n-octylmethacrylamide, N-tert-octylacrylamide, N-n
- N-alkyl (meth)acrylamide derivatives such as dodecyl acrylamide and N-n-dodecylmethacrylamide; (meth)acrylates such as ethyl acrylate, methyl methacrylate, butyl methacrylate, butyl acrylate, lauryl acrylate, 2-ethylhexyl methacrylate, and glycidyl methacrylate; Derivatives, olefins such as ethylene, propylene, butene, acrylonitrile, methacrinitrile, vinyl acetate,
Examples include vinyl chloride, vinylidene chloride, styrene, α-methylstyrene, butadiene, and isoprene. Examples of the hydrophilic monomer include acrylamide, methacrylamide, N-methylacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, N,N-dimethylacrylamide, N,N-dimethylmethacrylamide,
N-ethylacrylamide, N,N-diethylacrylamide, N-acryloylpyrrolidine, diacetone acrylamide, methylene bisacrylamide, hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl methacrylate, hydroxypropyl acrylate, various methoxypolyethylene glycol methacrylates, various Examples include methoxypolyethylene glycol acrylate, N-vinyl-2-pyrrolidone, and vinyl acetate,
Glycidyl methacrylate or the like can also be introduced by copolymerization and hydrolyzed to impart hydrophilicity. Examples of the ionic monomer include acrylic acid, methacrylic acid, vinylsulfonic acid, allylsulfonic acid, methallylsulfonic acid, styrenesulfonic acid, 2-acrylamido-2-phenylpropanesulfonic acid, and 2-acrylamide-2- Methyl-
Acids such as propanesulfonic acid and their salts, N,
N-dimethylaminoethyl methacrylate, N,
N-diethylaminoethyl methacrylate, N,
N-dimethylaminoethyl acrylate, N,N
-dimethylaminopropylmethacrylamide,
Examples include amines such as N,N-dimethylaminopropylacrylamide and salts thereof. In addition, various acrylates, methacrylates,
It is also possible to introduce acrylamide, methacrylamide, acrylonitrile, etc. by copolymerization and hydrolyze it to impart ionicity. Among the other copolymerizable monomers mentioned above, lipophilic monomers are added to form the core of the emulsion, and are particularly useful when producing highly hydrophilic N-propyl substituted products. It is.
On the other hand, hydrophilic monomers and ionic monomers are useful for modifying the emulsion surface and stabilizing the emulsion itself. In the method for producing a polymer emulsion of the present invention, the relationship between the unsaturated amide compound represented by the above general formula and the other copolymerizable monomers described above is as follows:
The unsaturated amide compound described above generally becomes a component that forms the surface of an emulsion, and in particular, in copolymerization with a lipophilic monomer, the lipophilic monomer forms the core of the emulsion and therefore necessarily forms the surface. It turns out. In such a case, the proportion of the unsaturated amide compound can be extremely small, and it is sufficient that it is present in the monomer in an amount of 0.05% or more, preferably 0.5% or more. More preferably 10.7 as shown in Examples.
% or more. Conventional polymerization methods can be used to produce the polymer emulsion of the present invention. That is,
Water is used as the reaction medium, and specifically, ion-exchanged water, distilled water, tap water, industrial water, etc. are used. In addition, as a method for emulsifying the monomer, the temperature of water is set to be higher than the clouding point of the temperature-sensitive monomer of the present invention to make the monomer hydrophobic, or the method is carried out in combination with a hydrophobic monomer. At that time, ordinary anionic surfactants such as alkyl sulfates, alkylaryl sulfonates, fatty acid soaps, etc. may be used as emulsifiers, or the above-mentioned ionic monomers may be used. Good too. Further, as the polymerization initiator used in the polymerization, any water-soluble radical polymerization initiator such as persulfate can be used, and of course it is also possible to use a redox type initiator. Specifically, for example, ammonium persulfate, potassium persulfate, hydrogen peroxide, tert.-butyl peroxide, and reducing agents to be combined with the above-mentioned oxidizing agents as redox initiators include sulfite, hydrogen sulfite, etc. Examples include salts with low ionic valences such as iron, copper, and cobalt, organic amines such as aniline, and reducing sugars such as aldoses and ketoses.
In addition, as an azo compound, 2,2'-azobis-2
-amidinopropane hydrochloride, 2,2'-azobis-
2,4-dimethylvaleronitrile, 4,4'-azobis-4-cyanovaleic acid and its salts, etc. can be used. It is also possible to use two or more of the above polymerization initiators in combination. The polymerization temperature varies depending on the polymerization initiator used, but is usually 0 to
The temperature is 100°C, preferably in the range of 5 to 90°C. As a specific method for producing the polymer emulsion, a conventional production method can be adopted. For example, an emulsion can be produced by adding a polymerization initiator and a monomer to water all at once at a water temperature higher than the clouding point of the thermosensitive monomer, or an emulsion can be produced by adding monomers stepwise. Various methods can be adopted.
At this time, the temperature-sensitive monomer may be present in its entirety at the start of polymerization, or may be added in stages. Also,
The particle size of the emulsion can be controlled by controlling the types and amounts of temperature-sensitive monomers, ionic monomers, surfactants, etc. Generally, when the amount of these substances added is increased, the particle size becomes smaller. Function: As described above, the present invention has discovered a temperature-sensitive monomer that causes cloudiness in an aqueous solution when heated, and has also developed a new method for producing a polymer emulsion that utilizes the temperature sensitivity of the monomer. The production of the polymer emulsion of the present invention has the following effects. First, when producing a polymer emulsion in water at a temperature higher than the clouding point of the thermosensitive monomer, the polymer emulsion can be formed using the precipitated monomers as cores, which facilitates the polymerization reaction. be able to. At that time, as a monomer, a linear alkyl substituted product, that is, N-n-propyl (meth)acrylamide,
It is preferable to use N-n-butyl (meth)acrylamide because the polymer emulsion can be produced stably. Furthermore, when producing at a temperature above the cloud point of the monomer or polymer, the resulting polymer emulsion becomes an emulsion above the cloud point of the polymer, but dissolves in water below the cloud point. This state change across the cloud point can be repeated any number of times. In addition, emulsion polymerization can produce extremely high molecular weight polymers, so if the water temperature is lowered below the clouding point to make the polymer water soluble, extremely high molecular weight water-soluble polymers can be provided. The cloud point of a polymer can be controlled by changing the copolymer composition, generally increasing with copolymers with hydrophilic or ionic monomers and decreasing with copolymers with lipophilic monomers. do. Second, emulsions can be produced in such a way that the polymer of lipophilic monomers is in the core of the emulsion, while the temperature-sensitive monomer is on the surface of the emulsion, so by changing the temperature of the emulsion, the lipophilic surface of the emulsion can be and hydrophobicity can be controlled. Therefore, by utilizing the hydrophilicity/hydrophobicity of the emulsion surface, it is possible to give an emulsion a higher level of functionality than before, which allows various substances to be adsorbed and desorbed on the emulsion surface. Such changes in the hydrophilic and hydrophobic properties of the emulsion surface can be observed by measuring temperature changes in the viscosity of the emulsion aqueous solution, and generally the viscosity decreases as the temperature increases. Thirdly, in the present invention, a stable emulsion can be formed by using an ionic monomer without using a surfactant as an emulsifier, so a clean latex that is not contaminated by surfactants etc. can be provided. . The polymer produced by polymerization in the emulsion state of the present invention can be used not only as a coating material for various substances such as paper, fibers, and metals in which ordinary emulsions are used, but also as a water-soluble polymer with a very high molecular weight. This polymer is useful in the field of thickeners, polymer flocculants, and synthetic fibers, which require highly flexible polymers, and in the field of synthetic emulsions, such as diagnostic latics, which require extremely clean and highly functional properties. It is. Hereinafter, the present invention will be explained in more detail using examples. Reference Example 1 An N-n-propylacrylamide aqueous solution with a concentration of 9.05% was placed in a spectrophotometer cell, the temperature of the cell was raised by ring water, and the transmittance at 420 nm was measured. When reading from the measured value as the cloud point, the temperature between the maximum transmittance and the minimum transmittance was 45.
It was warm at ℃. The maximum transmittance at that time is 98.5%.
The minimum transmittance was 1.8%. Furthermore, upon cooling, the cloudy liquid returned to its colorless and transparent state. Reference Examples 2 to 4 Cloud points were measured in the same manner as in Reference Example 1 using the concentrations of N-n-propylacrylamide aqueous solutions shown in Table 1, and the results are shown in Table 1. In all cases, the cloudy liquid returned to its colorless and transparent color upon cooling.

[Table] Reference Example 5 An aqueous solution of N-isopropylacrylamide with a concentration of 18.2% was placed in a test tube with an inner diameter of 15 mm, a standard thermometer was inserted into the tube, and the solution was gradually heated in constant temperature water while stirring with the thermometer. It begins to become cloudy at 38.5℃,
At 44.0°C, the temperature became cloudy to the point that the mercury bulb on the thermometer could no longer be seen. On the other hand, upon cooling, the cloudy liquid returned to its colorless and transparent state. Reference Example 6 Cloud point was measured in exactly the same manner as in Reference Example 5 using an aqueous N-isopropylacrylamide solution with a concentration of 14.6%. It started to become cloudy at 48℃, and became cloudy to the point that the mercury bulb on the thermometer could no longer be seen at 78℃. Also,
Upon cooling, the cloudy liquid returned to its colorless and transparent color. Reference Example 7 Cloud point was measured in exactly the same manner as in Reference Example 5 using an aqueous N-n-butylacrylamide solution with a concentration of 3.0%. It started to become cloudy at 21℃. Even after heating, the temperature did not become cloudy to the point where the mercury bulb on the thermometer was no longer visible. Furthermore, upon cooling, the cloudy liquid returned to its colorless and transparent state. Reference Example 8 Cloud point was measured in exactly the same manner as in Reference Example 5 using an aqueous N-n-propyl methacrylamide solution with a concentration of 5.7%. It started to become cloudy at 26℃. Even after heating, the temperature did not become cloudy to the point where the mercury bulb on the thermometer was no longer visible. Furthermore, upon cooling, the cloudy liquid returned to its colorless and transparent state. Example 1 3.5 N-n-propylacrylamide in 25 ml of water
g and 0.5 g of sodium 2-acrylamido-2-phenylpropanesulfonate (hereinafter abbreviated as APPS-Na) were added, and after replacing the inside of the reactor with nitrogen,
The temperature was raised to 40°C to emulsify the reaction solution. In addition, when a part of this emulsion was separated and the temperature was gradually lowered, a phenomenon in which the state changed from cloudy to transparent at 35°C was observed, so the cloud point of the monomer in this liquid composition was confirmed. admitted that the temperature was slightly higher than 35°C. Next, 1 ml of a 5% aqueous potassium persulfate solution was added to the reaction solution to initiate polymerization, which was allowed to polymerize for 6 hours. During this time, the polymerization proceeded while the polymerization solution remained in an emulsified state and could be sufficiently stirred. When the polymerization liquid was cooled, it became transparent and could no longer be stirred. Therefore, when the polymerization solution was diluted to a concentration of 5% and its viscosity was measured using a B-type viscometer, it was 100 centipoise at 50℃, but when the temperature was lowered to 10℃, the viscosity was 6.460.
I became a centipoise. Example 2 Emulsion polymerization was carried out in the same manner as in Example 1 except that 25 ml of water, 5 g of styrene, 1.0 g of N-n-propylacrylamide and 0.5 g of APPS-Na were used. Note that the emulsion having this monomer composition did not change its cloudy state even when the temperature was lowered to 0°C.
The obtained polymer emulsion was stable even at room temperature, and when the average particle diameter was measured by a simple turbidity method, the value was 0.39μ. Example 3 44 ml of water, 4 g of N-n-butylacrylamide,
N-n-propylacrylamide 1g, APPS-
Emulsion polymerization was carried out in the same manner as in Example 1 except that 0.5 g of Na was used. Indeed, this emulsion changed from a cloudy state to a transparent state at 21°C. The resulting polymer emulsion is stable even at room temperature;
When the average particle diameter was measured using a simple turbidity method, the value was 0.66μ. Example 4 Emulsion polymerization was carried out in the same manner as in Example 9, except that 45 ml of water, 5 g of N-n-butylacrylacrylamide, and 0.5 g of APPS-Na were used. Indeed, this emulsion changed from a cloudy state to a transparent state at 19°C. The obtained polymer emulsion was stable even at room temperature, and when the average particle diameter was measured by a simple turbidity method, the value was 1.18μ. Example 5 N-n-propylacrylamide in 1700 g of water
After adding 100 g of sodium 2-acrylamido-2-phenylpropanesulfonate and 3 g of sodium 2-acrylamido-2-phenylpropanesulfonate, the inside of the reactor was purged with nitrogen gas, and then heated to 60°C.
In this state, the liquid became cloudy. Naho, this emulsion is 48
The state changed from cloudy to transparent at ℃. Next, 0.6 g of potassium persulfate was added to the reaction solution to initiate polymerization, and the polymerization was continued for 3 hours. The reaction solution formed a stable emulsion. Then, 50 g of acrylonitrile was added to the reaction solution using a pump over 30 minutes. After the addition was complete, the reaction solution was allowed to react at 60° C. for an additional 3 hours. The obtained polymer emulsion had a cloud point at 15°C, and the viscosity of the polymer emulsion was measured at each temperature using a B-type viscometer.
2.44 centipoise (cps), 2.8 cps at 40°C, at 25°C
It was 3.5cps and 7600cps at 10℃. Warm again,
When the above measurement was repeated, it was 2.4 cps at 50℃, 40
It was 2.8cps at ℃, 3.5cps at 25℃, and 7600cps at 10℃. 24 g of the polymer emulsion was placed on a 12 cm x 12 cm square Teflon sheet, and after drying at 125° C. for 2 hours, the polymer was peeled off from the Teflon sheet to obtain a sheet with a thickness of 0.2 m/m. When the sheet was immersed in water, it absorbed water. The temperature of the water to be immersed at that time
When changing the temperature to 10℃, 25℃, and 50℃ and measuring the amount of water absorbed per 1g of dry sheet, it was 4.0g at 10℃ and 4.0g at 25℃.
It was 3.0g at 50°C and 2.5g at 50°C. Comparative example 1 3.0 N-n-propylacrylamide in 23 ml of water
After replacing the inside of the reactor with nitrogen, the reaction solution was kept at 15°C. Next, 2 ml of a 10% ammonium persulfate aqueous solution and 2 ml of a 5% sodium bisulfite aqueous solution were added to the reaction solution, and polymerization was carried out at 15 to 20°C for 6 hours to form a 10% aqueous solution of N-n-propylacrylamide polymer. I got it. Note that during polymerization,
The reaction solution was colorless and transparent. The aqueous polymer solution was diluted to 5% and its viscosity was measured using a B-type viscometer and found to be 125 centipoise at 10°C. Further, when the aqueous polymer solution was heated to 50° C., the aqueous solution became cloudy, but over time the polymer precipitated and adhered to the walls of the vessel and the like.

Claims (1)

[Claims] 1. A monomer represented by the general formula: (In the above formula, R ₁ is hydrogen or a methyl group, and R ₂ is a propyl group or a butyl group.) 1. A method for producing a polymer emulsion, which comprises homopolymerizing, copolymerizing, or copolymerizing with other copolymerizable monomers at a temperature above the temperature at which the polymer emulsion becomes cloudy at its concentration.