JPS635130B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing capsules having walls made of polyvinyl alcohol polymers. More specifically, in an aqueous medium, as curing agent components A and B of an aqueous polyvinyl alcohol polymer solution,
The combination of curing agent components of the polyvinyl alcohol polymer aqueous solution is such that A and B do not have the property of curing the polyvinyl alcohol polymer aqueous solution when used alone, but exhibit curing performance only when used together. In the method of forming a capsule having a wall made of a polyvinyl alcohol polymer using a polyvinyl alcohol polymer, a water-insoluble capsule core material is dispersed in an aqueous solution of a polyvinyl alcohol polymer containing only A of the curing agent and having a cloud point. By keeping the temperature of the entire system above the clouding point of the polyvinyl alcohol polymer aqueous solution, a concentrated aqueous solution of the polyvinyl alcohol polymer appears as a separate phase around the core substance, and further, among the curing agent components, A polyvinyl alcohol polymer aqueous solution containing only B and having a clouding point is continuously added to the system, and a polyvinyl alcohol polymer is formed around the core material by the action of the curing agent components A and B. The present invention relates to a capsule manufacturing method characterized by curing a concentrated aqueous solution. A method for producing microcapsules by liquid-liquid phase separation in an aqueous medium using a polyvinyl alcohol polymer as a wall material has been patented in France.
1304891, Special Publication 47-26575, Special Publication 47-51712, Special Publication
47-51713, etc. However, in these methods, the polyvinyl alcohol polymer used is water-soluble in the temperature range from 0°C to 100°C, and a single aqueous solution of polyvinyl alcohol cannot be made into a liquid without the aid of a third substance.
It was not possible to separate the liquid phase. That is, in the conventional method, in order to cause liquid-liquid phase separation, it was essential to add a third substance that induces phase separation to the polyvinyl alcohol polymer aqueous solution. Such phase separation inducing agents include inorganic salts such as sodium sulfate, organic solvents that are water-soluble and non-solvents for polyvinyl alcohol such as isopropyl alcohol, or water-soluble and incompatible with polyvinyl alcohol such as gum arabic. Polymers, etc. are used. These phase separation inducers cannot serve as wall-forming materials, but become impurities in the polyvinyl alcohol-based polymer that is the wall-forming material. Therefore, it is necessary to remove impurities by processing such as washing after capsule formation, and the process is complicated. In addition, the obtained microcapsules tend to become porous because the phase separation inducing agent mixed in the capsule wall membrane is removed during the process of removing impurities, and the core substance tends to leak. In addition, in these methods, it is difficult to adjust the addition rate and amount of the phase separation inducer, and if the addition rate is too fast or the amount added is too large, the capsules tend to aggregate and form grape clusters. If the speed is slowed or the amount added is reduced, there is a drawback that encapsulation takes a long time. Furthermore, in these methods, even if the addition rate and amount of the phase separation inducer are appropriately adjusted, if the concentration of the core substance in the system is increased, the concentration of polyvinyl alcohol as the wall film material will be increased accordingly. As a result, the viscosity of the system increases and the fluidity of the system decreases, causing the entire system to become agglomerated.
It was virtually impossible to do anything beyond that. On the other hand, in JP-A No. 54-139885, a polyvinyl acetal resin having a cloud point is used as a wall material, and a capsule is formed around an isocyanate compound as a core material through phase separation due to the cloud point in an aqueous medium. A method is disclosed. However, in this method, the entire amount of the polyvinyl acetal resin that forms the film is encapsulated in an aqueous solution containing the isocyanate compound from the beginning, similar to the method using the phase separation inducer described above. As a method for fixing the polyvinyl acetal resin formed on the surface, a method has been adopted in which an inorganic substance or its salts having a large coagulation value is added to the polyvinyl acetal resin. Such inorganic substances or their salts include sodium sulfate, ammonium sulfate, potassium sulfate, etc., which have no chemical reactivity with polyvinyl acetal resin, or magnesium sulfate, aluminum sulfate, boric acid, borax, anhydrous Only compounds such as silicic acid, silica gel, and titanate, which have only weak chemical reactivity in aqueous solution and do not have the ability to harden polyvinyl acetal resin, are disclosed. . Therefore, the obtained capsules can be obtained by operations such as washing after capsule formation, or by operations such as using the capsules in an aqueous medium different from the capsule formation system after capsule formation (1) These salts (2) The membrane easily dissolves in water. (3) Even if it does not dissolve in water, the membrane swells with water and becomes porous. (4) The membrane strength decreases. It has disadvantages such as the membrane is easily destroyed. Furthermore, in this method, it is expected that the polyvinyl acetal resin will be immobilized by the reaction between the isocyanate compound as the core substance and the polyvinyl acetal resin. However, in general, when mutually insoluble compounds react at the interface between the capsule core material and the capsule wall membrane to form a film, the mass transfer of the reacting compounds is restricted, so only a very thin film on the order of millimicrons is possible. film thickness and film strength cannot be adjusted. In addition, the inorganic substance or its salt having a large coagulation value with respect to the polyvinyl acetal resin used in this method has the ability to significantly lower the clouding point of the aqueous solution of the polyvinyl acetal resin. Therefore, the addition of such inorganic substances or salts with a large coagulation value drastically changes the phase separation equilibrium, causing the polyvinyl acetal resin in the dilute aqueous solution to rapidly and non-uniformly appear as a concentrated phase, making the system unstable. Due to the need for stable conditions, it is virtually impossible to implement such a method industrially. Furthermore, in this method, if the concentration of the core substance in the system is increased, it becomes necessary to increase the concentration of the membrane material in order to maintain a constant film thickness, but in the case of phase separation due to cloud point, the concentration of the membrane material is high. As the dilute phase concentration increases during phase separation, the efficiency as a membrane material decreases, and the viscosity of the system increases, reducing the fluidity of the system.
The entire system tends to form agglomerates, and the core substance concentration is reduced to 30%.
It was virtually impossible to increase the amount by volume %/system or more. The object of the present invention is to overcome the above-mentioned drawbacks,
In particular, a method for producing capsules with a tightly hardened, dense wall membrane that is completely insoluble in water using a simple operation, including a system containing a high concentration of core material without the addition of phase separation inducers, etc. It is about providing. As a result of various studies, the present inventors have found that A and B are a polyvinyl alcohol polymer that has a cloud point when made into an aqueous solution, and the curing agent components A and B of the polyvinyl alcohol polymer aqueous solution. By using a combination of curing agent components of a polyvinyl alcohol polymer aqueous solution, each of which does not have the property of curing the polyvinyl alcohol polymer aqueous solution when used alone, but exhibits curing performance only when used together. Among the agent ingredients, A
By dispersing a water-insoluble capsule core material in an aqueous polyvinyl alcohol polymer solution containing only polyvinyl alcohol and having a cloud point, and maintaining the temperature of the entire system above the cloud point of the polyvinyl alcohol polymer aqueous solution, A concentrated aqueous solution of a polyvinyl alcohol-based polymer is caused to appear as a separated phase around the core material, and an aqueous polyvinyl alcohol-based polymer solution containing only B of the curing agent components and having a clouding point is continuously added to the system. discovered that the above object could be achieved by curing the concentrated aqueous solution phase of the polyvinyl alcohol polymer formed around the core material by the action of curing agent components A and B, and completed the present invention. I came to the point. The first important feature of the present invention is that the capsules obtained are encapsulated without using any phase separation inducing agent or coagulant, which become impurities in the capsule wall film, and hardened with a hardening agent. has a dense wall that is stable against water and has a low degree of porosity. The second important feature of the present invention is that by continuously adding an aqueous solution of a polyvinyl alcohol polymer having a cloud point to the system, most of the polyvinyl alcohol polymer can undergo phase separation due to the cloud point. Polyvinyl alcohol-based polyvinyl alcohol is continuously formed as a wall film around the core material by the oxidation process, and is continuously cured by the curing agent components A and B, so that it does not form a wall film in the system but exists as a dilute aqueous solution. The concentration of the polymer can always be kept very low and therefore the viscosity of the system can be encapsulated while maintaining low fluidity even in systems with a high content of core material. The advantage is that it can be encapsulated without any loss. If a polyvinyl alcohol polymer without a cloud point is used and continuous addition is carried out in the same way as in the present invention, the concentration of polyvinyl alcohol that does not form a wall film in the system will increase, and the entire system will coagulate into lumps, making it difficult to form capsules. I can't get it. In this specification, "cloud point" represents the following temperature. That is, the polyvinyl alcohol polymer used in the present invention dissolves uniformly in water at low temperatures to form a transparent homogeneous solution, but when the temperature rises, microdroplets of a concentrated aqueous solution of the polyvinyl alcohol polymer disperse in water. The system becomes cloudy. The temperature at which cloudiness begins is called the cloud point. The state of the system of the present invention at this cloud point is not so-called solid-liquid phase separation but liquid-liquid phase separation, which means that if left in a cloudy state for a long time at a temperature above the cloud point, the polyvinyl alcohol polymer will form. This is confirmed by the fact that the microdroplets of the concentrated aqueous solution gradually settle and separate into two transparent layers, with the upper layer being a dilute aqueous solution and the lower layer being a concentrated aqueous solution. The polyvinyl alcohol polymer used in the present invention can be used as long as it has a total of vinyl alcohol units and vinyl acetate units of 60 mol% or more and has a cloud point when made into an aqueous solution.
For example, partially saponified polyvinyl alcohol with a degree of saponification of 60 to 85 mol%, ethylene and/or an alkyl group having 1 to 20 carbon atoms in the side chain by copolymerization.
Partially or fully saponified modified polyvinyl alcohol obtained by introducing 0.1 to 20 mol% of hydrophilic groups, partially saponified modified polyvinyl alcohol obtained by introducing 0.1 to 5 mol% of hydrophilic groups by copolymerization, 0.1 to 20 mol% of hydrophilic groups and ethylene and/or alkyl groups with 1 to 20 carbon atoms in the side chain.
Partially or completely saponified modified polyvinyl alcohol obtained by introducing 0.1 to 20 mol% of the lactone ring, or partially or completely saponified polyvinyl alcohol having a lactone ring of 1 to 40 mol% can be suitably used. These polyvinyl alcohol-based polymers are made by (1) homopolymerizing vinyl acetate and then saponifying it (2) having ethylene, an olefinically unsaturated compound having an alkyl group having 1 to 20 carbon atoms in the side chain, and a hydrophilic group. Copolymerizing vinyl acetate with one or more compounds selected from the group consisting of olefinic unsaturated compounds and saponifying the mixture. (3) Copolymerizing vinyl acetate and an olefinic unsaturated compound having a carboxyl group or a carboxylic acid ester group. ,
It can be obtained by saponification or, if necessary, subsequent acid treatment or heat treatment. Examples of the olefinic unsaturated hydrocarbons having an alkyl group include α-olefins such as 1-octadecene, 1-hexadecene, 1-dodecene, and 1-octene, vinyl stearate, vinyl laurate, vinyl versatate, and vinyl propiodine. Vinyl esters such as Nate, stearyl acrylate,
lauryl acrylate, octyl acrylate,
Acrylic esters such as butyl acrylate, methacrylic esters such as stearyl methacrylate, lauryl methacrylate, octyl methacrylate, butyl methacrylate, vinyl ethers such as stearyl vinyl ether, lauryl vinyl ether, butyl vinyl ether, etc., with an alkyl group having 1 to 20 carbon atoms in the side chain. Compounds with In addition, examples of the olefinic unsaturated hydrocarbons having a hydrophilic group include acrylic acid, methacrylic acid,
Carboxyl group-containing compounds such as maleic acid, maleic anhydride, itaconic acid, fumaric acid and their esters, sulfonic acid compounds such as vinyl sulfonate and allyl sulfonate, their esters and alkali metal salts, vinylpyrrolidone, acrylamide, N -Nitrogen-containing compounds such as substituted acrylamide and vinylpyridine are used. Further, as the olefinic unsaturated compound having a carboxyl group or a carboxylic acid ester group, (meth)acrylic acid, maleic acid, maleic anhydride, itaconic acid, fumaric acid, and esters thereof are used. In general, the lower the saponification degree, the higher the ethylene content, the degree of modification by alkyl groups, and the higher the lactone ring content, the lower the cloud point of an aqueous solution at the same concentration, and the higher the degree of modification by hydrophilic groups, the lower the cloud point. It tends to be higher. If the degree of saponification and degree of modification are outside the above range, the cloud point of the aqueous solution with a concentration of 1 to 10% will change.
When the temperature reaches 100℃ or higher, the cloud point virtually disappears, or
Alternatively, it is not suitable for the purpose of the present invention because it is insoluble in cold water and it is difficult to obtain a homogeneous solution. in general,
There is a relationship between the cloud point and the concentration of the polyvinyl alcohol polymer aqueous solution: as the concentration of the polyvinyl alcohol polymer increases, the cloud point temporarily decreases, but as the concentration further increases, the cloud point increases. be. Therefore, the optimum operating temperature for encapsulation can be arbitrarily selected by changing the properties of the polyvinyl alcohol polymer used and the concentration of the polyvinyl alcohol polymer aqueous solution; point is 10℃
It is preferable to employ operating conditions such as to exist between -80<0>C. In general, there is a relationship between the concentration of polyvinyl alcohol polymer and the concentration of polyvinyl alcohol polymer in a concentrated aqueous solution that has phase-separated at a temperature above the cloud point, such that the lower the concentration, the higher the concentration of the concentrated phase that has phase-separated. There is. For these reasons, in order to efficiently form a wall film using a polyvinyl alcohol polymer, it is preferable that the concentration of the polyvinyl alcohol polymer aqueous solution used when dispersing the core material is 0.05 to 5%. The concentration of the polyvinyl alcohol polymer aqueous solution used when dispersing the core material may be adjusted to 0.05 to 5% before phase separation occurs.
In order to increase the efficiency of dispersing the core substance, when a polyvinyl alcohol polymer is used at a high concentration, it can be diluted with water to bring the concentration within the above range. On the other hand, the polyvinyl alcohol polymer aqueous solution that is continuously added to the system only needs to be adjusted so that it undergoes phase separation when added to the system, but when added to the system it immediately disperses uniformly and maintains a uniform phase separation state. It is more preferable that Therefore, the aqueous solution of polyvinyl alcohol polymer that is added continuously has a cloud point that is higher than the operating temperature used for phase separation of the system, and when it is added to the system, it is diluted by the water in the system. Therefore, it is preferable to use a highly concentrated aqueous solution that has a cloud point lower than the operating temperature and undergoes phase separation. In the method of the present invention, when the amount of core material used is constant, as the amount of polyvinyl alcohol polymer used increases, the thickness of the wall of the resulting capsule increases; There is a relationship that as the amount used decreases, the thickness of the wall membrane decreases. Therefore, the thickness of the capsule membrane can be varied by changing the ratio of the polyvinyl alcohol polymer to the core material. The method of the present invention is preferably carried out under conditions such that the polyvinyl alcohol polymer accounts for 5 to 50% by weight based on the core material. The combination of curing agent components A and B of the polyvinyl alcohol polymer capsule wall film in the method of the present invention includes a combination of an acid and a dialdehyde compound such as glyoxal and glutaraldehyde, or a combination of a dialdehyde compound and an acid; A combination of acid and urea and/or melamine and formalin, alkali and divinyl sulfone, methyl vinyl ketone and diacetone acrylamide, etc., with two or more microcondensation-reactive groups or microcondensation-reactive groups and aldol condensation-reactivity. A combination of a compound having a group, a combination of an alkali and an epichlorohydrin compound, etc. are used.
In the case of partially saponified polyvinyl alcohol-based polymers, the method of using an alkali as one of the curing agent components may cause the polyvinyl alcohol-based polymer to be saponified and the cloud point to change. It is preferable to use it in the case of When these curing agent components are used alone, they do not have the ability to make the polyvinyl alcohol polymer aqueous solution insoluble in water and further harden it, but when both of them coexist, they exhibit curing performance for the first time, and the curing agent components The organic compound component reacts with the polyvinyl alcohol polymer, such as addition and crosslinking, to make the polyvinyl alcohol polymer wall film water-insoluble and further harden. The amount of the curing agent component varies depending on the wall strength required by the intended use of the capsule, but the amount of organic compound component that reacts with the polyvinyl alcohol polymer such as addition and crosslinking is usually 0.1 to the polyvinyl alcohol polymer.
Used in amounts of ~50% by weight. The amount of components of the curing agent that are considered to act catalytically, such as acids and alkalis, is preferably kept to a small amount as long as the progress of the reaction can be maintained at a sufficiently rapid rate in order to avoid undesirable side effects. The core material encapsulated within the capsule of the present invention is
Substances suitable for the process of the present invention include petroleum, kerosene, gasoline, naphtha, mineral oils such as paraffin oil, fish oil, and lard oil, as long as they are substantially water-insoluble and can be used in either solid or liquid form. Animal oils such as fallen raw oil, linseed oil, soybean oil, castor oil, etc.
Vegetable oils such as corn oil, biphenyl derivatives,
Examples include organic solvents such as phthalate esters. Further, polymers, adhesives, dyes, fragrances, pigments, agricultural chemicals, medicines, etc. can also be dissolved or dispersed in these substances. Furthermore, when dispersing these core materials in the polyvinyl alcohol polymer aqueous solution, a small amount of another dispersant, such as an anionic surfactant or a nonionic surfactant, may be added. In addition, one or more anionic compounds selected from the group consisting of alkylbenzenesulfonic acids, alkylsulfates, alkylbenzenesulfonic acids, naphthalenesulfonic acid formalin condensates, dialkylsulfosuccinic acids, and alkali metal salts thereof. Adding a surfactant or one or more cationic surfactants selected from the group consisting of imidazoline derivatives, alkylpyridinium salts, alkylamine salts, and alkylammonium salts to an aqueous polyvinyl alcohol polymer solution, Although it can be used as an agglomeration inhibitor for capsule particles, it is desirable to keep the amount added as small as possible. Since these anionic surfactants and cationic surfactants have the effect of raising the cloud point of an aqueous solution containing a polyvinyl alcohol polymer, they can also be effectively used as cloud point regulators. Additionally, a small amount of an antifoaming agent in an aqueous polyvinyl alcohol-based polymer solution can be added to the system. As these antifoaming agents, silicone antifoaming agents are preferable because they have a high antifoaming effect and do not cause any undesirable side effects. The capsules according to the present invention may be used in the form of a powder by curing the polyvinyl alcohol polymer wall film and then drying, or they may be used in a suspended state in water without being filtered or dried. According to the method of the present invention, capsules having a diameter of 1 to 5000 microns can be made arbitrarily, and the resulting capsules are used in fields such as pressure-sensitive copying paper, thermal paper, agricultural chemicals, fragrances, adhesives, and medicine. You can. Hereinafter, the present invention will be explained in more detail with reference to Examples. In addition, "part" in an Example shows a weight part. Example 1 7.5 parts of a 15% (by weight) aqueous solution of partially saponified polyvinyl alcohol having a degree of saponification of 70 mol% and a degree of polymerization of 850 was diluted with water to prepare 225 parts of an aqueous solution ().
Additionally, 50% (by weight) glutaraldehyde is added to 30 parts of a 15% (by weight) aqueous solution of the polyvinyl alcohol.
Add 1.5 parts of an aqueous solution () with a cloud point of 43 °C
31.5 copies were created. Aqueous solution () 31.5 in 225 parts of water
The cloud point of the system was 23 in the entire concentration range from the time when 1 drop was added to the time when 31.5 parts were added.
It existed in the range of ℃~33℃. Furthermore, the cloud point of the system was 23°C to 33°C in the entire concentration range up to the addition of 31.5 parts of the aqueous solution () to 225 parts of the aqueous solution (225).
existed within the range of Add 0.5 parts of 63% (by weight) nitric acid to 225 parts of the aqueous solution (225 parts) to adjust the pH to 2.5, add 45 parts of isopropylbenzene (boiling point 152°C), and stir vigorously at 20°C to make oil droplets with a diameter of about 50μ. An oil-in-water dispersion was prepared.
Then, the temperature was raised to 40°C while stirring slowly. 40
After reaching the temperature, 31.5 parts of an aqueous solution () at 20°C was added dropwise over 1.5 hours. After the completion of the dropping, heating was continued for an additional hour to advance the curing reaction. After this, it was dried at 80°C for 2 hours. The obtained capsules were spherical capsules with a particle diameter of about 50 μm and no aggregated particles. This was heated at 95° C. for 2 days, but there was no weight loss of isopropylbenzene. Further, no change was observed in the capsules even after immersion in water for 2 days. The method of the present invention is superior to conventional methods in terms of ease of producing non-agglomerated capsules, and the capsules obtained also have dense wall membranes, excellent retention of core substances, and excellent water resistance. For the sake of illustration, capsules produced by the conventional method are listed in Table 1 as a comparative example.

[Table] Comparative example of observing changes in pucelle 1 Saponification degree 98.5 mol%, polymerization degree 1750, no cloud point, 5.625 parts and 50% polyvinyl alcohol
(Weight) Add 45 parts of isopropylbenzene to 156 parts of an aqueous solution containing 1.5 parts of glutaraldehyde.
An oil-in-water dispersion with an oil droplet diameter of approximately 50 μm was prepared by vigorous stirring at ℃. Then slowly heat to 40℃ while stirring.
100 parts of 10% (by weight) sodium sulfate as a phase separation inducer was added dropwise at a rate of 0.5 parts per minute for 200 minutes to form capsules having polyvinyl alcohol walls swollen with water. When this capsule was observed under a microscope, it was found to be in the shape of a bunch of grapes with a particle diameter of 500 to 1000 microns, consisting of dozens of small capsule particles aggregated. After adding 0.5 parts of 63% (by weight) nitric acid to this suspension of capsule particles and carrying out a curing reaction for 3 hours to harden the polyvinyl alcohol wall film,
It was filtered, washed with water, and dried at 80°C for 2 hours. The obtained capsules were agglomerated particles with a particle size of 500-1000μ. Table 1 shows the weight loss when this was heated at 95°C for 2 days. Further, when this capsule was immersed in water for 2 days, no change was observed in the capsule. Comparative Example 2 Encapsulation was carried out in the following manner using a polyvinyl acetal resin having a clouding point when made into an aqueous solution. Polyvinyl butyl acetal (manufactured by Sekisui Chemical Co., Ltd.,
W-201) was diluted with water to prepare 156 parts of an aqueous solution containing 5.625 parts of polyvinyl butyl acetal.
45 parts of isopropylbenzene was added to this and vigorously stirred at 20°C to prepare an oil-in-water dispersion with an oil droplet diameter of approximately 50μ. Next, the temperature was raised to 33° C. with gentle stirring, and stirring was continued at this temperature for 2 hours to phase-separate the polyvinyl butyl acetal aqueous solution. Furthermore, as a coagulant for polyvinyl butyl acetal, 5
% (by weight) 100 parts of sodium sulfate at a rate of 0.5 parts per minute
It was added dropwise over 2.00 minutes. At this point, the capsules were in the shape of a bunch of grapes with particle diameters of 100 to 500 μm, in which several small particle capsules were aggregated. After filtering, it was briefly washed with warm water at 5.0°C and dried at 80°C for 2 hours. The obtained capsules were agglomerated particles with a particle size of 100-500μ. Table 1 shows the weight loss when this was heated at 95°C for 2 days. Also, add 2 capsules to water.
When soaked for several days, the wall film gradually dissolved and isopropylbenzene separated. Example 2 2.7 parts of a 15% (weight) aqueous solution of partially saponified polyvinyl alcohol having a degree of saponification of 72 mol% and a degree of polymerization of 700 was diluted with water to make 158 parts. 63% (weight) to this
0.64 parts of nitric acid was added to adjust the pH to 2.0 to create an aqueous solution (). Further, 3.7 parts of 50% (by weight) glutaraldehyde was added to 76 parts of a 15% (by weight) aqueous solution of the polyvinyl alcohol to prepare an aqueous solution () having a cloud point of 45°C. Aqueous solution () in 158 parts of water
When adding 79.7 parts, from the time of adding one drop, 79.7
The cloud point of the system was in the range of 25°C to 35°C over the entire concentration range up to the point where 50% of the solution was added. In addition, the cloud point of the system is
It existed in the range of 25°C to 35°C. Add 116 parts of alkylnaphthalene (manufactured by Soken Chemical, trade name KSKoil No. 330) to 158 parts of the aqueous solution (),
By stirring vigorously at 20°C, an oil-in-water dispersion with an oil droplet size of 20-40μ was prepared. Then, the temperature was raised to 40°C while stirring slowly. After reaching 40°C, 79.7 parts of a 20°C aqueous solution () was added dropwise over 3 hours. After the completion of the dropping, heating was continued for an additional hour to advance the curing reaction. Capsules with a particle size of 20-40μ
A capsule slurry containing 32% (by weight)/system was obtained. Comparative Example 3 When made into an aqueous solution, the degree of saponification is 88 mol% and the degree of polymerization is 1750 as polyvinyl alcohol with no cloud point.
This was carried out in the same manner as above using polyvinyl alcohol. In this case, the entire system agglomerated and no capsule particles were obtained. Comparative Example 4 Using polyvinyl alcohol with a degree of saponification of 88 mol% and a degree of polymerization of 1750 and no cloud point, the core material was 32%.
(Weight)/system In order to obtain capsules from the system containing the system, encapsulation was carried out as follows. An aqueous solution containing 11.8 parts of the polyvinyl alcohol and 3.7 parts of 50% (by weight) glutaraldehyde.
116 parts of alkylnaphthalene was added to 138 parts and stirred vigorously to prepare an oil-in-water dispersion having an oil droplet diameter of 20 to 40 μm. Next, the temperature was raised to 40°C with gentle stirring, and 100 parts of a 10% (by weight) aqueous solution of sodium sulfate was added dropwise at a rate of 0.5 parts per minute over 200 minutes as a phase separation inducer. I couldn't get it. Comparative Example 5 Encapsulation was carried out in the following manner using an aqueous solution of a polyvinyl acetal resin having a cloud point in order to obtain capsules from a system containing 32% (by weight) of a core material. An aqueous solution containing 11.8 parts of polyvinyl acetoacetal by diluting polyvinyl acetoacetal (Vinizol K manufactured by Daido Kasei Co., Ltd.) with water.
138 parts were made at room temperature. Then, the mixture was heated to 43° C. to cause phase separation, and 116 parts of alkylnaphthalene was added with vigorous stirring to prepare an oil-in-water dispersion having an oil droplet diameter of 20 to 40 μm. When this system was slowly stirred at 43° C. for 2 hours, an aggregate of capsules consisting of several small particles agglomerated was generated. Another 5% (weight)
200 parts of 100 parts of sodium sulfate aqueous solution at a rate of 0.5 parts per minute
When the mixture was added dropwise for minutes, the entire system agglomerated into a lump and no capsules were obtained. Example 3 Saponification degree of 71 mol%, polymerization degree of 700, 50% to 8 parts of a 10% (weight) aqueous solution of partially saponified polyvinyl alcohol
% (by weight) of glutaraldehyde aqueous solution 6 parts, 5
% (by weight) of sodium dodecylbenzenesulfonate aqueous solution and 66 parts of water to form an aqueous solution ()
80.31 copies were created. Further, 2.3 parts of a 5% (by weight) sodium dodecylbenzenesulfonate aqueous solution was added to 60 parts of a 10% (by weight) aqueous solution of the polyvinyl alcohol to prepare 62.3 parts of an aqueous solution (). 5%
(weight) of sodium dodecylbenzenesulfonate
When the aqueous solution () was added to 80.31 parts of water containing 0.31 parts, the cloud point of the system was in the range of 45°C to 55°C over the entire concentration range from the time when 1 drop was added to the time when 62.3 parts were added. In addition, the cloud point of the system existed in the range of 45°C to 55°C in the entire concentration range up to the addition of 62.3 parts of the aqueous solution (2) to the aqueous solution (2). Add 80 parts of alkylnaphthalene (manufactured by Soken Chemical Co., Ltd., trade name: KSK oil No. 330) containing 2% (by weight) of crystal violet lactone to 80.31 parts of the aqueous solution (), stir vigorously at 20°C, and add 5 to 10μ of oil. An oil-in-water dispersion with a droplet size was prepared. Then, the temperature was raised to 60°C while stirring slowly. After reaching 60℃, 20
An aqueous solution prepared by adding 3.6 parts of N/2 sulfuric acid to 62.3 parts of an aqueous solution ( ) at 0.degree. C. was added dropwise over 3 hours. After the dropwise addition was completed, heating was continued for an additional hour to advance the curing reaction. Neutralize the system by adding 0.36 parts of a 5N aqueous solution of caustic soda, and remove 35% of the capsules with a particle size of 5-10μ.
A capsule slurry containing (weight)/system was obtained.
The obtained capsule slurry was coated on a base paper with a basis weight of 40 g/m ² at a solid content of 6 g/m ² and then the coated paper was layered with the clay paper prepared as described below, and when written with a pencil, a clear blue colored image was obtained. gave. For the viscous paper, 100 parts of activated clay was dispersed using a homogenizer in 300 parts of water containing 5 parts of a 40% (by weight) aqueous solution of caustic soda, and then 40 parts of Dowratex 636 (trade name, styrene-butadiene latex manufactured by Dow Chemical Company) was added. It was prepared by applying it to a solid content of 12 g/m ² on base paper having a basis weight of 50 g/m ² . As a comparative example, polyvinyl alcohol with a degree of saponification of 98.5 mol% and a degree of polymerization of 1750 was used as a polyvinyl alcohol that does not have a cloud point when made into an aqueous solution.
This was done in the same manner as above. In this case, the entire system agglomerated and no capsule particles were obtained. Example 4 158 parts of an aqueous solution containing 4 parts of a 10% (by weight) aqueous solution of partially saponified polyvinyl alcohol with a degree of saponification of 80 mol% and a degree of polymerization of 2000 and 3 parts of urea was prepared.
Furthermore, 7.5 parts of 37% (by weight) formalin was added to 58 parts of a 10% (by weight) aqueous solution of the polyvinyl alcohol to prepare 59.8 parts of an aqueous solution () having a cloud point of 45°C. Aqueous solution in 158 parts of water containing 3 parts of urea ()
The cloud point of the system was 38°C in the entire concentration range from the time when 1 drop was added to the time when 59.8 parts were added.
Existed in the range of ~40°C. Also aqueous solution () 158
The cloud point of the system was in the range of 38 to 40°C in the entire concentration range up to the addition of 59.8 parts of the aqueous solution. Add 0.1 part of 63% (by weight) nitric acid to 158 parts of aqueous solution () to adjust the pH to 3.5, and make liquid paraffin in which 20% (by weight) linalool (lily of the valley scented fragrance, manufactured by Kuraray Co., Ltd.) is dissolved. Added 58 copies,
By stirring vigorously at 20°C, an oil-in-water dispersion with an oil droplet size of 50 to 100 μm was prepared. Then, the temperature was raised to 43°C while stirring slowly. After the temperature reached 43°C, 59.8 parts of a 20°C aqueous solution () was added dropwise over 3 hours. After the dropping was completed, heating was continued for another 1 hour to advance the curing process. After this, it was dried at 80°C for 1 hour. The obtained capsules were spherical capsules with a particle size of 50 to 100 μm. When the capsule was broken under pressure, the scent of lily of the valley was released. Example 5 2400 g of methanol, 1545 g of vinyl acetate, 0.7 g of itaconic acid and 55 g of vinyl versatate, 10 g of azobisisobutyronitrile in 5 flasks.
and polymerized at 60° C. for 5 hours while continuously adding 20.6 g of itaconic acid. This copolymer was saponified in methanol with caustic soda to obtain a modified polyvinyl alcohol containing 1 mol % of itaconic acid and 1.5 mol % of vinyl versatate as copolymer components. The degree of saponification of this modified polyvinyl alcohol is 98.5 mol%, and the viscosity of a 4% aqueous solution at 20°C is
It was 10 centipoise. 10% (by weight) of this modified polyvinyl alcohol
4 parts of the aqueous solution was diluted with 154 parts of water containing 0.3 parts of caustic soda to prepare 158 parts of the aqueous solution (). Further, 58 parts of a 10% (by weight) aqueous solution (aqueous solution ()) of the modified polyvinyl alcohol was prepared. When the aqueous solution () is added to 158 parts of water, from the time when 1 drop is added
The cloud point of the system was in the range of 49°C to 57°C over the entire concentration range up to the addition of 58 parts. In addition, the cloud point of the system existed in the range of 49°C to 57°C in the entire concentration range up to the addition of 58 parts of the aqueous solution (2) to 158 parts of the aqueous solution (158). Dioctyl phthalate 55% in aqueous solution () 158 parts
The mixture was stirred vigorously at 20°C to prepare an oil-in-water dispersion having an oil droplet diameter of 50 to 100μ. Then, the temperature was raised to 60°C while stirring slowly. After reaching 60°C, an aqueous solution prepared by adding 2.4 parts of methyl vinyl ketone to 58 parts of a 20°C aqueous solution was added dropwise over 4 hours. After the dropping was completed, heating was continued for another 2 hours to advance the curing process. The obtained capsules have a particle size of
It was a mononuclear capsule of 50-100μ. Example 6 200 g of methanol, 800 g of vinyl acetate and 0.3 azobisisobutyronitrile in an autoclave
g was introduced, ethylene gas was introduced, and the reaction was carried out at 60° C. for 4 hours under a pressure of 10 kg/cm ² to produce an ethylene-vinyl acetate copolymer. This was saponified in methanol using caustic soda to obtain modified polyvinyl alcohol containing 10 mol% of ethylene as a copolymer component. 10% (by weight) of this modified polyvinyl alcohol
4 parts of the aqueous solution was diluted with 154 parts of water containing 0.3 parts of caustic soda to prepare 158 parts of the aqueous solution (). Further, 58 parts of a 10% (by weight) aqueous solution (aqueous solution ()) of the modified polyvinyl alcohol was prepared. When the aqueous solution () is added to 158 parts of water, from the time when 1 drop is added
The cloud point of the system was in the range of 30°C to 43°C in the entire concentration range up to the addition of 58 parts. Further, the cloud point of the system existed in the range of 30°C to 43°C in the entire concentration range up to the addition of 58 parts of the aqueous solution (2) to 158 parts of the aqueous solution (2). Monoethylbiphenyl 50 to 158 parts of aqueous solution ()
of the mixture and stirred vigorously at 20°C to prepare an oil-in-water dispersion having an oil droplet diameter of 100 to 500μ. Then, the temperature was raised to 45°C while stirring slowly. After reaching 45°C, an aqueous solution prepared by adding 2.4 parts of methyl vinyl ketone to 58 parts of a 20°C aqueous solution was added dropwise over 4 hours. After the dropping was completed, heating was continued for another 2 hours to advance the curing process. The obtained capsules have a particle size of
It was a mononuclear capsule of 100-500μ. Comparative Example 6 Instead of the aqueous solution ( ) used in Example 1,
Example 1 was carried out as in Example 1, except that 31.5 parts of an aqueous solution containing only 1.5 parts of 50% (by weight) glutaraldehyde was used. The obtained capsules were spherical capsules with a particle size of 50μ without agglomeration, but the concentration of polyvinyl alcohol that forms the wall film was not sufficient, and the strength of the capsule wall film was therefore low, so it was heated at 95°C for 2 days. The weight loss of isopropylbenzene at 87
%, which was extremely large. Comparative Example 7 Aqueous solution () used in Example 1 and 15% (by weight) of polyvinyl alcohol in the aqueous solution ()
30 parts of the aqueous solution and used as a new aqueous solution ()' (i.e., when the entire amount of polyvinyl alcohol used is used at once), and only 1.5 parts of 50% (by weight) glutaraldehyde is added. The same procedure as in Example 1 was carried out except that 31.5 parts of the aqueous solution (2) was added in the same manner as in Example 1. The obtained capsules contained many aggregated particles, and the weight loss of isopropylbenzene when heated at 95° C. for 2 days was extremely large at 70%.

Claims (1)

[Scope of Claims] 1. In an aqueous medium, as curing agent components A and B of a polyvinyl alcohol polymer aqueous solution, A and B
However, by using a combination of curing agent components of a polyvinyl alcohol polymer aqueous solution, each of which does not have the property of curing the polyvinyl alcohol polymer aqueous solution by itself, but exhibits curing performance only when used together. In a method for forming a capsule having a wall made of an alcoholic polymer, a water-insoluble capsule core material is dispersed in an aqueous solution of a polyvinyl alcohol-based polymer containing only A among the curing agent components and having a clouding point. By keeping the overall temperature above the clouding point of the polyvinyl alcohol polymer aqueous solution, a concentrated aqueous solution of the polyvinyl alcohol polymer appears as a separate phase around the core material, and furthermore, only B of the curing agent components is allowed to appear. A concentrated aqueous solution of a polyvinyl alcohol-based polymer containing a polyvinyl alcohol-based polymer having a cloud point is continuously added to the system, and is formed around the core material by the action of curing agent components A and B. A capsule manufacturing method characterized by curing. 2. An aqueous solution of a partially saponified polyvinyl alcohol polymer having a saponification degree of 50 to 85 mol% as an aqueous solution of a polyvinyl alcohol polymer having a cloud point, and having a cloud point between 10°C and 80°C. A method for manufacturing a capsule according to claim 1, which comprises using a method for manufacturing a capsule according to claim 1. 3. The method for producing capsules according to claim 1, which comprises using a combination of an acid and a dialdehyde compound as the curing agent components A and B of the polyvinyl alcohol polymer. 4. A group consisting of alkyl sulfonic acids, dialkyl sulfosuccinic acids, alkyl sulfuric esters, alkylbenzenesulfonic acids, and alkali metal salts of naphthalene sulfonic acid formalin condensates is added to a polyvinyl alcohol polymer aqueous solution containing a core substance in a dispersed state. one or more anionic anti-aggregating agents selected from the group consisting of imidazoline derivatives, alkyl ammonium salts, alkyl pyridinium salts and alkyl amine salts; The method for manufacturing a capsule according to claim 1, characterized in that the capsules are coexisting with each other. 5 As a polyvinyl alcohol polymer aqueous solution that is continuously added to the system, the cloud point of this aqueous solution is higher than the phase separation operation temperature of the system, and phase separation occurs when it is added to the system and diluted with water in the system. A method for producing capsules according to claim 1, characterized in that a concentrated aqueous solution having a cloud point lower than the operating temperature is used.