JP2004083619A - Water-soluble polymer powder and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide N-isopropylacrylamide polymer powder as a water-soluble polymer used as a temperature-sensitive shader, a temperature sensor, a humidity sensor, a temperature-sensitive aqueous gel, a cosmetic additive, a pharmaceutical sustained release carrier, a skin plaster additive, etc., comprising an N-isopropyl(meth)acrylamide as a main monomer and having temperature sensitivity with a small amount of the residual monomer. <P>SOLUTION: The powder is obtained by polymerizing the N-isopropylacrylamide monomer using a water-soluble redox initiator according to an aqueous solution polymerization, especially under conditions of ≤18 mass% of concentration in the aqueous solution, ≤10°C polymerization initiation temperature and ≤40°C polymerization peak temperature and then depositing the produced polymer in warm water at ≥40°C. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is a water-soluble, temperature-sensitive water-soluble body used for temperature-sensitive light-shielding bodies, temperature sensors, humidity sensors, temperature-sensitive aqueous gels, cosmetic additives, pharmaceutical sustained-release carriers, skin patch additives, and the like. The present invention relates to a polymer powder, more particularly, to an N-isopropylacrylamide polymer powder and a method for producing the same.
[0002]
[Prior art]
An N-isopropylacrylamide-based polymer having N-isopropylacrylamide or N-isopropylmethacrylamide as a main constituent monomer, for example, an N-isopropylacrylamide polymer has a transition temperature of about 32 ° C. Although it has a property, it has a special reversible property that it precipitates in a high-temperature region, and is attracting attention as a temperature-sensitive material.
[0003]
As a method for producing a polymer containing N-isopropylacrylamide or N-isopropylmethacrylamide as a main constituent monomer, a method such as reverse phase suspension polymerization or precipitation polymerization in addition to aqueous solution polymerization is known.
[0004]
For example, Japanese Patent Application Laid-Open No. 2000-230008 discloses an aqueous solution polymerization method using an azo-based initiator, and Japanese Patent Publication No. 04-68321 discloses a precipitation polymerization using a benzene solvent. JP-A-60-120710 discloses precipitation polymerization using an alkyl acetate solvent, and JP-A-60-120710 discloses reverse phase suspension polymerization.
[0005]
[Problems to be solved by the invention]
However, the N-isopropylacrylamide-based polymer obtained by the reversed-phase suspension polymerization or the precipitation polymerization contains the solvent used for the polymerization, and even after powdering, the residual solvent is completely removed. This residual solvent has a drawback that the content of the residual monomer is a serious problem in certain applications.
[0006]
In addition, in the method by aqueous solution polymerization, although there is no problem of the residual solvent, there is generally a tendency that the residual monomer is large, and the temperature-sensitive aqueous gel, cosmetic additive, pharmaceutical sustained release carrier, skin patch When used as an additive for additives, etc., one of the major requirements is that the amount of residual monomers is small. Therefore, it is required to reduce residual monomers in a polymer by aqueous solution polymerization.
[0007]
Therefore, Japanese Patent Application Laid-Open No. 08-59709 discloses that a polymer having a small amount of residual monomer is obtained by polymerizing an N-substituted acrylamide-based monomer in isopropyl acetate using a water-soluble initiator and then removing the solvent. Is disclosed, but the amount of residual monomer is on the order of several hundreds to several thousands, which is still insufficient.
[0008]
In view of such circumstances, the present invention provides an N-isopropylacrylamide-based polymer powder as a temperature-sensitive water-soluble polymer having N-isopropylacrylamide or N-isopropylmethacrylamide as a main monomer having few residual monomers. We considered to do it.
[0009]
As a result, an N-isopropylacrylamide-based monomer is subjected to aqueous solution polymerization under specific conditions, and the resulting polymer is precipitated with warm water. The inventors have found that the present invention can be obtained and completed the present invention.
[0010]
[Means for Solving the Problems]
That is, the invention described in claim 1 of the present invention
A method for producing a water-soluble polymer powder, comprising polymerizing an N-isopropylacrylamide-based monomer in an aqueous solution using a water-soluble redox initiator, and precipitating the resulting polymer with warm water of 40 ° C. or more. .
[0011]
The invention described in claim 2 of the present invention
The method for producing a water-soluble polymer powder according to claim 1,
The N-isopropylacrylamide-based monomer,
It is characterized by being N-isopropylacrylamide or N-isopropylmethacrylamide.
[0012]
Further, the invention described in claim 3 of the present invention is:
The method for producing a water-soluble polymer powder according to claim 1,
The N-isopropylacrylamide-based monomer,
It is mainly characterized in that it is mainly composed of N-isopropylacrylamide or N-isopropylmethacrylamide and contains a vinyl polymerizable monomer.
[0013]
Further, the invention described in claim 4 of the present invention is:
The method for producing a water-soluble polymer powder according to claim 2,
The aqueous solution polymerization,
The concentration of N-isopropylacrylamide in an aqueous solution is 18% by mass or less, the polymerization initiation temperature is 10C or less, and the polymerization peak temperature is 40C or less.
[0014]
Further, the invention according to claim 5 of the present invention provides:
The method for producing a water-soluble polymer powder according to claim 1,
The water-soluble redox initiator,
At least one or more oxidizing substances selected from persulfates, hydrogen peroxide, and hydroperoxides;
It is characterized by comprising at least one or more reducing substances selected from ferrous salt compounds, sulfite compounds, bisulfite compounds, and organic reducing agents.
[0015]
Further, the invention described in claim 6 of the present invention is:
A water-soluble polymer powder prepared by the production method according to claim 1.
[0016]
Furthermore, the invention according to claim 6 of the present invention provides:
A water-soluble polymer powder comprising an N-isopropylacrylamide-based monomer as a constituent monomer and a residual monomer of 100 ppm or less.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
The temperature-sensitive water-soluble polymer powder of the present invention may be a monomer of N-isopropylacrylamide or N-isopropylmethacrylamide (hereinafter, both acryl and methacryl are collectively referred to as (meth) acryl), or It is obtained by subjecting an N-isopropylacrylamide-based polymer containing these as a main component and containing a vinyl polymerizable monomer to aqueous solution polymerization under specific conditions, and precipitating the obtained polymer with warm water.
[0018]
That is, in the present invention, in addition to the N-isopropyl (meth) acrylic monomer, as long as the heat sensitivity is not impaired, the composition mainly contains N-isopropyl (meth) acrylamide and contains a vinyl polymerizable monomer. Although a polymer can be used, a polymer of N-isopropyl (meth) acrylamide alone, which is sensitive to heat, particularly a polymer of N-isopropylacrylamide alone is preferable for the present invention.
[0019]
Other than the above-mentioned N-isopropyl (meth) acrylamide, those used as vinyl polymerizable monomers include Nn-propyl (meth) acrylamide and N-ethyl (meth) acrylamide having a transition temperature with respect to water. , N-cyclopropyl (meth) acrylamide, N-isobutyl (meth) acrylamide, N-pentyl (meth) acrylamide, N-cyclohexyl (meth) acrylamide and the like.
[0020]
Further, for example, water-soluble monomers such as acrylic acid and its salts, acrylamide, N-vinylpyrrolidone, itaconic acid and its salts, maleic acid and its salts, methacrylic acid and its salts, and methacrylamide are also included.
[0021]
These vinyl polymerizable monomers are used for adjusting the transition temperature and the like, but since they tend to impair the heat sensitivity, it is preferable to use as little as possible, specifically, It is at most 20 parts by mass, more preferably at most 10 parts by mass, based on 100 parts by mass of N-isopropyl (meth) acrylamide.
[0022]
The method for producing the N-isopropyl (meth) acrylamide polymer in the present invention is an aqueous solution polymerization of the above-mentioned monomer group.
[0023]
In the polymerization of an aqueous solution of N-isopropyl (meth) acrylamide, the concentration of the aqueous solution is an important reaction factor. For example, in the case of an N-isopropylacrylamide monomer, its solubility in water is about 20% by mass or more. When the temperature is approximately 25 ° C. or lower, a solid-liquid two phase is formed. When the temperature exceeds 25 ° C., a liquid-liquid two phase is formed, and a uniform polymerization system becomes difficult. The concentration is preferably 18% by mass or less, 10% by mass or more, more preferably 10 to 15% by mass. When the monomer concentration exceeds 18% by mass, it takes too much time to dissolve the monomer in water, and when the monomer concentration is less than 10% by mass, the yield of the polymer is reduced.
[0024]
In the present invention, the method for polymerizing N-isopropyl (meth) acrylamide is a method in which an aqueous solution of the above-mentioned monomer is polymerized with a water-soluble redox initiator.
[0025]
The oxidizing substance of the water-soluble redox initiator is at least one selected from persulfates, hydrogen peroxide and hydroperoxides, and the reducing substances are ferrous compounds and sulfurous acids. It is preferable to use at least one selected from salt compounds, bisulfite compounds, and organic reducing agents such as alcohols and polyamines.
[0026]
A combination of a metal salt or ammonium salt of persulfuric acid as an oxidizing substance and a metal salt or ammonium salt of sulfurous acid as a reducing substance and / or a metal salt or ammonium salt of bisulfite is relatively inexpensive and an organic compound-based compound. This is more preferable because undesirable decomposition products are not produced as compared with the water-soluble redox initiator of the above.
[0027]
In the present invention, the water-soluble azo initiator is generally toxic to decomposition products, reaction products, undecomposed residues, and the like resulting therefrom, and contains polymers such as pharmaceuticals, quasi-drugs, and cosmetics. It is desirable to avoid using it in the present invention, as its use is undesirable.
[0028]
The amount of the water-soluble redox initiator to be added in the present invention is preferably 0.01 to 1.0 part by mass when the total amount of the monomers is 100 parts by mass. The polymerization is liable to be inhibited by the polymerization inhibitor and dissolved oxygen contained in the monomer, and if it exceeds 1.0 part by mass, the degree of polymerization is undesirably low.
[0029]
Further, the number of parts of the reducing substance to be added is preferably such that the molar equivalent ratio of the oxidizing substance to the reducing substance is 1.0: 1.0 to 5.0, more preferably 1.0: 1.5 to 3.0. In the case where the amount of the reducing substance is small, a sufficient redox system cannot be obtained. On the other hand, when the amount of the reducing substance is large, for example, in the case of sulfite or bisulfite, depending on the residue, It is not preferable because sulfur dioxide is generated, causing odor and irritation to mucous membranes.
[0030]
In the present invention, the polymerization initiation temperature is preferably adjusted to a temperature of 10 ° C. or lower, more preferably to a temperature of 8 ° C. or lower and 3 ° C. or higher. When the polymerization is started in a state where the polymerization initiation temperature exceeds 10 ° C. In many cases, the residual monomer exceeds 100 ppm with respect to 100% by mass of the obtained polymer, and even if the polymerization initiation temperature is controlled to less than 3 ° C., the residual monomer is substantially reduced accordingly. It is not preferable because both are meaningless.
[0031]
Further, the polymerization peak temperature in the present invention is preferably controlled at a temperature of 40 ° C. or lower, and more preferably at a temperature of 30 ° C. or lower. When the polymerization peak temperature is controlled at a temperature higher than 40 ° C. However, the amount of residual monomer relative to 100% by mass of the obtained polymer often exceeds 100 ppm, which is not preferable. On the other hand, if the temperature is controlled to be lower than 15 ° C., the residual monomer is not substantially reduced, so that it has no meaning and is not preferable.
[0032]
After the polymerization temperature showed a peak, it was cooled down to about the same as the external temperature, and at the stage when the polymerization was almost completed, a water-soluble redox initiator was added as an additional catalyst to reliably reduce residual monomers. However, in this case, the same initiator system is desirable, and other initiator systems may be used. However, the addition amount is about 1/10 to half of the number of parts used for the polymerization.
[0033]
The N-isopropylacrylamide-based polymer powder in the present invention is prepared by throwing the polymer aqueous solution obtained under the above conditions into warm water at a temperature of 40 ° C. or higher to precipitate the solution, using a usual method, for example, pressurizing, depressurizing and After solid-liquid separation by normal pressure filtration or the like, it can be obtained by drying and pulverizing with a usual dryer.
[0034]
【Example】
Hereinafter, the water-soluble polymer powder having temperature sensitivity of the present invention and a method for producing the same will be described more specifically with reference to Examples and Comparative Examples.
The residual monomer and viscosity of the prepared polymer powder were measured by the following methods.
[0035]
<Method for measuring residual monomer>
0.1 g of the polymer powder was dissolved in 10 ml of pure water, and 10 ml of methyl alcohol was added to the aqueous solution to precipitate a polymer, which was filtered through a 45 μm filter. It was measured by chromatography (hereinafter abbreviated as HPLC).
Water / methanol (8/2) solvent or water / acetonitrile (8/2) solvent was used for the mobile phase of HPLC. Detection was performed at 230 nm with a UV detector, and a calibration curve was obtained using a standard substance. And the amount of residual monomer was determined.
[0036]
<Measurement of viscosity>
A 10% by mass aqueous solution was prepared and measured using a Brookfield viscometer (hereinafter abbreviated as a B-type viscometer).
[0037]
<Example 1>
A jacketed 10-liter glass flask equipped with a thermometer, a nitrogen inlet tube, a stirring blade and a reflux tube was charged with 1.2 kg of N-isopropylacrylamide monomer and 6.8 kg of ion-exchanged water. Was rotated at 100 rpm, and nitrogen was blown at a flow rate of 1 L / min for 1 hour or more.
Cool water is supplied to the jacket to cool the internal temperature to a temperature of 5 ° C., and the supply of cold water is stopped. Was added, nitrogen was blown in at a flow rate of 0.2 L / min, and stirring was continued at a stirring blade rotation speed of 100 rpm.
Approximately 4 hours later, the peak temperature (temperature: 29.2 ° C.) was reached, and aging was performed for another 4 hours.
[0038]
The aqueous solution of ammonium peroxosulfate was prepared by dissolving 1.8 g of ammonium peroxosulfate in 60 g of ion-exchanged water, and the aqueous solution of sodium bisulfite was prepared by dissolving 1.8 g of sodium bisulfite in 60 g of ion-exchanged water. .
The molar ratio between the oxidizing substance and the reducing substance is 1.0: 2.2.
[0039]
The polymerization solution obtained above is poured into a large amount of pure water warmed to a temperature of about 70 ° C. to precipitate and precipitate a polymer. The obtained precipitate is dried at a temperature of 80 ° C. for 12 hours, and then crushed with a crusher. Powdered by machine.
The viscosity of 10% by mass of the obtained polymer powder was 350 mPa · s, and the residual monomer was 30 ppm.
[0040]
<Example 2>
Polymerization was carried out in the same manner as in Example 1. Two hours after the peak temperature was reached, 1 g of ammonium peroxosulfate and 1 g of sodium bisulfite were added as additional catalysts, and the mixture was further aged for 2 hours. Other operations such as powdering were performed in the same manner as in Example 1.
The viscosity of 10% by mass of the obtained polymer powder was 300 mPa · s, and the residual monomer was 10 ppm.
[0041]
<Comparative Example 1>
A polymer powder was obtained in the same manner as in Example 1, except that the temperature at the start of polymerization was 15 ° C. In addition, about 3 hours after the peak temperature, a temperature of 41.8 ° C. was recorded. The viscosity of 10% by mass of the obtained polymer powder was 180 mPa · s, and the residual monomer was 430 ppm.
[0042]
<Comparative Example 2>
Polymerization was carried out in the same manner as in Example 1 except that the polymerization was started at a temperature of 60 to 65 ° C. using 7 g of 2,2′-azobis (2-amidinopropane) dihydrochloride as a polymerization initiator. did.
Polymerization was started immediately after the addition of the polymerization initiator, and the polymer was precipitated due to the high temperature. The rotation speed of the stirring blade was increased to 300 rpm, and stirring was continued at a temperature of 60 ° C. for 10 hours. Solid-liquid separation was performed while the temperature was high, and a powder product was obtained in the same manner as in the example.
The viscosity of the obtained polymer powder at 10% by mass was 150 mPa · s, and the residual monomer was 12,350 ppm.
[0043]
<Comparative Example 3>
Methyl alcohol was used as a solvent instead of pure water. As an initiator, 1.2 g of 2,2′-azobis (2,4-dimethylvaleronitrile) was used, and polymerized for 10 hours at the reflux temperature of methyl alcohol. After cooling, the polymer solution was poured into a 10-fold amount of hot water at a temperature of 60 ° C. to precipitate a polymer. The polymer was separated into solid and liquid, and then powdered in the same manner. The viscosity of the obtained polymer powder at 10% by mass was 250 mPa · s, and the residual monomer was 7,970 ppm.
Further, 10 g of the obtained polymer powder was redissolved in 50 ml of methyl alcohol, and poured into 10 times the amount of hot water at a temperature of 60 ° C. to precipitate again, and powdered similarly.
The residual monomer in the obtained polymer powder was 630 ppm.
[0044]
【The invention's effect】
According to the present invention, a monomer aqueous solution mainly composed of N-isopropylacrylamide is polymerized with a water-soluble redox initiator at a polymerization peak temperature of 40 ° C. or lower, particularly at a polymerization start temperature of 10 ° C. or lower, An N-isopropylacrylamide polymer powder having a residual monomer of 100 ppm or less is obtained.
[0045]
The obtained polymer containing N-isopropylacrylamide as a main monomer having a small amount of residual monomers is a water-soluble polymer having a temperature sensitivity, and is a temperature-sensitive light shield, a temperature sensor, a humidity sensor, and a temperature-sensitive aqueous solution. It can be suitably used for gels, cosmetic additives, pharmaceutical sustained-release carriers, skin patch additives and the like.

Claims (7)

A method for producing a water-soluble polymer powder, comprising subjecting an N-isopropylacrylamide-based monomer to aqueous solution polymerization using a water-soluble redox initiator, and precipitating the resulting polymer with warm water of 40 ° C or higher. The N-isopropylacrylamide-based monomer,
The method for producing a water-soluble polymer powder according to claim 1, wherein the method is N-isopropylacrylamide or N-isopropylmethacrylamide. The N-isopropylacrylamide-based monomer,
The method for producing a water-soluble polymer powder according to claim 1, wherein the method mainly comprises N-isopropylacrylamide or N-isopropylmethacrylamide and contains a vinyl polymerizable monomer. The aqueous solution polymerization,
3. The method according to claim 2, wherein the concentration of N-isopropylacrylamide in the aqueous solution is 18% by mass or less, the polymerization initiation temperature is 10C or less, and the polymerization peak temperature is 40C or less. Manufacturing method of molecular powder. The water-soluble redox initiator,
At least one or more oxidizing substances selected from persulfates, hydrogen peroxide, and hydroperoxides;
3. The method according to claim 1, comprising at least one reducing substance selected from a ferrous salt compound, a sulfite compound, a bisulfite compound, and an organic reducing agent. 4. Manufacturing method of water-soluble polymer powder. A water-soluble polymer powder prepared by the production method according to claim 1. A water-soluble polymer powder comprising an N-isopropylacrylamide-based monomer as a constituent monomer and a residual monomer of 100 ppm or less.