JPS6128440A - Preparation of ph-responsive microcapsule - Google Patents

Abstract

PURPOSE:To obtain a microcapsule releasing a core substance in a neutral or acidic aqueous solution, by dispersing the core substance in a solvent having a specific copolymer dissolved therein and further dispersing the prepared dispersion throughtout a solvent mixture consisting of an oil component and a dispersing solvent. CONSTITUTION:A copolymer is prepared from at least one basic monomer represented by formula (wherein R is hydrogen or a methyl group and R<1> and R<2> are an 1-3C alkyl group), at least one water-insoluble or hardly water-soluble monomer and at least one water-soluble monomer. A core substance is dispersed in the dispersing solvent in which this copolymer was dissolved and the obtained dispersion is further dispersed in a solvent mixture consisting of an oil component and a dispersing solvent and the dispersing solvent is subsequently removed to prepare a pH-responsive microcapsule. This microcapsule is insoluble in an alkali aqueous solution but dissolved in a neutral or acidic aqueous solution to release the core substance.

Description

[Detailed description of the invention] Production! The present invention relates to a method for producing pi-sensitive microphones and capsules, and more specifically, they are substantially insoluble in alkaline solutions, soluble in neutral solutions, and exhibit selective solubility depending on pH. The present invention relates to a method for producing microcapsules shown in the accompanying drawings.

The microcapsules are useful, for example, as laundry aids for use with alkaline detergents.

By forming microcapsules using the active ingredient as a core material and using a pH-sensitive material as a coating material, the core material can be released depending on the pH condition of the solution.

One use of such microcapsules is as a laundry aid for use with alkaline detergents. Generally, the washing process using a washing machine consists of water pouring, washing 1, dehydration, rinsing, and dehydration, and washing aids such as fabric softeners are added after washing is completed to maximize their effects. Traditionally, it was common for housewives to operate each washing machine in sequence, and in such cases, they would first add detergent to complete the washing process, and then add fabric softener, bleach, and starch during the rinsing process. The addition of laundry aids such as these was not very burdensome and there was no great resistance. However, recently, as semi-automatic and fully automatic washing machines have become popular, housewives are now freed from half-way operations, but this has not yet been possible due to the addition of auxiliary agents. .

■ If you use microcapsules coated with a polymer that is virtually insoluble in alkaline washing liquids but soluble in neutral rinsing liquids, the laundry aid components can be removed from the alkaline washing liquid during washing. The auxiliary agent component can be eluted into the rinsing solution during the rinsing process, thereby effectively demonstrating the effect of the auxiliary agent, and eliminating the need for laundry auxiliary agents that conventionally had to be added during the rinsing process. Since it is effectively blended from the beginning, the trouble of adding auxiliary agents can be saved.

Several polymers whose solubility changes with pH have been known. For example, polyvinyl acetal diethylaminoacetate is insoluble in water in a neutral range, but soluble in water in an acidic range from pH 5.8. In addition, the copolymer of vinylpyridine and acrylic acid is p
It is soluble in water with a pH below H4 and above 7.4, and is insoluble in water in the P)l range between them. However, no polymer has been known so far that is insoluble in alkaline water, soluble in neutral to acidic water, and whose solubility changes in a narrow pH range. The present applicant previously proposed such a copolymer and a laundry aid coated with it in Japanese Patent Application No. 58-247997.

However, when a core material such as a laundry aid is coated with this copolymer, in order to effectively exhibit the effect of the core material, it is necessary that the core material be covered as completely as possible with the coating agent.

Additionally, coatings with small particle sizes are often required. For example, laundry aids absorb and remain on clothes after washing.
Because it is taken to the rinsing process after dehydration, it has high adsorption to clothing and does not give the user a foreign body sensation.
The particle size should be as small as possible.

An object of the present invention is to provide a method for producing microcapsules that sufficiently covers and protects the core material in an alkaline aqueous solution and releases the core material in a neutral to acidic aqueous solution.

Another object of the present invention is to provide a manufacturing method that can efficiently obtain microcapsules with a small particle size.

That is, the method for producing pH-sensitive microcapsules of the present invention is characterized by including the following steps (a) and (b).

(a) A step of dispersing the core substance in a dispersion solvent containing a copolymer containing the following monomers (A), CB), and (C) a dissolved therein.

(A) At least one basic monomer represented by general formula I
species (wherein R is hydrogen or a methyl group, R1 and R
(2 is an alkyl group having 1 to 3 carbon atoms, respectively) (B) at least one water-insoluble or poorly water-soluble monomer; (C) at least one water-soluble monomer; (b) obtained in step (a); A step of further dispersing the dispersion liquid in a mixed solvent of oil and a dispersion solvent, and then removing the dispersion solvent.

The basic monomer (A) represented by the above general formula (I) is a main monomer component for obtaining the pH-sensitive copolymer used in the present invention, and includes N,N-dimethylaminoethyl acrylate, N,N-dimethylaminoethyl methacrylate, N,N-diethylaminoethyl acrylate and N,N-diethylaminoethyl methacrylate are suitable, and these may be used alone or in combination of two or more.

The water-insoluble or poorly water-soluble monomer of component (B) has a pH of
A component that contributes to expanding the insoluble pH range of the sensitive copolymer, and specific examples include one selected from acrylic esters, methacrylic esters, crotonic esters, itaconic esters, vinyl acetate, and styrene. Or two or more types can be mentioned. When each alkyl ester of acrylic acid, methacrylic acid, crotonic acid, or itaconic acid is used as monomer (B), if the carbon chain length of the alkyl group bonded to the ester becomes long, the resultant copolymer may be dissolved in a slightly alkaline aqueous solution. It is preferable that these alkyl groups have 1 to 8 carbon atoms, since the dissolution in the alkyl group becomes slow.

Particularly preferred representative examples include methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate and ethyl methacrylate.

The water-soluble monomer (C) is a component that contributes to expanding the soluble p)I region of the p)l-sensitive copolymer, and specific examples include N,N-dimethylaminopropylacrylic acid (or methacrylic acid) amide, N,N-dimethylaminoacrylic acid (or methacrylic acid) amide, 2-hydroxyethylacrylic acid (or methacrylic acid), 2-
One or two types selected from esters of hydroxypropyl acrylic acid (or methacrylic acid), polyethylene glycol or methoxypolyethylene glycol (average number of added moles of ethylene glycol p = 2 to 30) and acrylic acid or methacrylic acid The above can be mentioned.

The copolymerization ratio of these monomers can be appropriately selected depending on the setting of the insoluble pH region and the soluble pH region necessary for the intended use of the microcapsules of the present invention. When using microcapsules as a laundry aid, the pH should be approximately 9.
It is preferable that it is insoluble in alkaline water with a pH of 5 or more, soluble in slightly alkaline or acidic water with a pH of about 8.5 or less, and has a high solubility ratio in the presence of a surfactant. In order to obtain such microcapsules, Q / (Q + m + n) = 0.08 in general formula (II)
~0.45, ya/(Q +m+n) =0.1~0
．． It is appropriate that Q is in the range of 65, preferably Q
/ (ffi +i++n) = 0.1~0.4, m/
(Q + m + n) = 0.15 to 0.55.

(In the formula, B umbrella and C11 represent structural units derived from monomers (B) and (C), respectively.) Furthermore, the degree of polymerization #+m+n is suitably 100 to 50,000, preferably 300 to 20,000. It is.

The copolymer used in the present invention can be obtained by conventional radical polymerization under normal pressure or increased pressure. As the polymerization solvent, acetone, benzene, toluene, chloroform, ethyl acetate, isopropanol, dimethylformamide, dimethyl sulfoxide, a mixed solvent thereof, or a water-containing solvent can be used. As the radical polymerization initiator, azobisisobutyronitrile, triphenylmethylazobenzene, etc. can be used, and the amount used is selected within the range of 2 to 100 mmol based on the total amount of monomers.

The polymerization temperature and time vary depending on the polymerization solvent and monomer combination used, but generally 5 to 20 hours at 40 to 90°C is appropriate. The monomer concentration varies depending on the type of solvent used, polymerization temperature and initiator used, but is usually in the range of 20 to 80% by weight.

The production method of the present invention uses the above-mentioned PH-sensitive copolymer to obtain microcapsules by a method classified as an in-liquid drying method. First, the above-mentioned copolymer is dissolved in a solvent for dispersing the core material. do. Next, the core material is dispersed in this solvent by stirring or the like to obtain a dispersion. As the dispersion solvent, one that dissolves the copolymer and disperses the core substance is used, and specifically, the above-mentioned polymerization solvents and alcohols can be used, and among them, acetone is preferable. The concentration of the copolymer in the dispersion solvent is suitably about 1 to 70% by weight, preferably 5 to 50% by weight. Further, the amount of the core material to be dispersed is likely to be about 0.2 to 10 times the amount of the polymer.

The core material is appropriately selected depending on the use of the microcapsules, and a typical example is use as a laundry aid. As laundry aids, di-long-chain alkyldimethylammonium salts,
1-Methyl-1-long-chain alkanoylaminoethyl-2-
Softening agents such as long-chain alkylimidazolinium salts, mixtures of di-long-chain alkyldimethylammonium salts and fatty acid salts, antifoaming agents such as silicone oil, and bleaching agents such as hypochlorites, percarbonates, and organic peracids. Examples include agents, thickening agents, blue tinting agents, optical brighteners, enzymes, and the like. The particle size of the core substance is appropriately selected depending on the application, but in the case of laundry aids, it is 10 to 500 μm.
Approximately m is suitable.

Next, the dispersion in which the core material is dispersed is redispersed in a mixed solvent of oil and a dispersion solvent. As the oil, oils that are liquid at room temperature such as liquid paraffin and vegetable oil can be used, and liquid paraffin is preferred. Liquid paraffin is an oil made from refined saturated hydrocarbons, and various grades can be used, but preferably one with a viscosity of 100 cst (37
, 8°C) or less.

The mixing ratio of oil and dispersion solvent is a weight ratio of dispersion solvent/dispersion solvent.
A suitable range of oil content is 0.01 to 0.2, preferably 0.03 to 0.1. If it is less than 0.01, agglomeration of the dispersed particles will occur, and if it exceeds 0.2, it will take a long time to remove the dispersion solvent, which is not preferable.

The mixed solvent of oil and dispersion solvent does not necessarily have to be dissolved in each other, and the polymerization solvent may be dispersed in the oil. The ratio of the dispersion liquid to the mixed solvent used is preferably a weight ratio of dispersion liquid/mixed solvent=O, 1 to 0.7.

Microcapsules are then obtained by removing the dispersion solvent from the resulting dispersion.

The dispersion solvent can be removed by heating or reducing pressure. The appropriate heating temperature is 40 to 60°C, and the vacuum removal can be carried out at room temperature or at 40 to 50°C at 20 to 60 cmHg. Microcapsules are recovered by separation means such as filtration,
It is then washed.

Transfer 1 The present invention is a method for producing microcapsules by applying an in-liquid drying method.

A dispersion liquid in which the core substance is dispersed in a dispersion solvent containing a dissolved copolymer is dispersed in a mixed solvent of oil and a dispersion solvent, and then the solvent is removed, whereby film formation occurs and the core substance is removed. Coated with copolymer. At this time, if the dispersion liquid is simply dispersed in oil, the dispersed particles will significantly aggregate and form large clumps, making it impossible to obtain good microcapsules.

On the other hand, when a mixed solvent of oil and a dispersion solvent is used, the dispersed particles do not aggregate and a good micro force cell can be obtained. The resulting microcapsules exhibit pH sensitivity.

Crab" 1 According to the production method of the present invention, it is possible to efficiently produce microcapsules that are insoluble in an alkaline aqueous solution, dissolve in a neutral or acidic aqueous solution to release a core substance, and have a minute particle size. I can do it.

In particular, this microcapsule is useful as an additive for alkaline detergents used for washing clothes, etc. by using a laundry aid as a core material.

(Left below) NuJIL Example 1 Distearyldimethylammonium chloride fine powder (
100 mesh sieve) was dispersed in 70 g of a 20% by weight acetone solution of a water-soluble polymer having the following structure.

CQ/ (Q+m+n)=0.35, m/ (A0m+
n) = 0.45, n + m + n = 1800~
1500) This dispersion was then mixed with liquid paraffin (viscosity 14
cst, 37.8° C.) and 24 g of acetone.

Subsequently, 30 to 50 csH was added at room temperature while continuing to stir.
The pressure was reduced for about 4 hours at a degree of vacuum of 1.3 g. The dispersed particles did not aggregate to form large clumps during the vacuum. After completing the decompression, the particles were separated by filtration with paper, and further washed with n-hexane to obtain particles with a particle size of 20 to 2 coated with a water-soluble polymer.
00μ microcapsules were obtained. The microcapsules can be used as a laundry aid to impart softness to clothing.

Example 2 Instead of removing acetone by reduced pressure in Example 1,
Acetone was removed by heating to 55° C. and stirring for about 5 hours. The other operations were the same as in Example 1. As a result, as in Example 1, good microcapsules were obtained without particle aggregation.

Comparative Example 1 When the same operation was performed as in Example 1 except that liquid paraffin was used instead of the rough-in-acetone mixed solvent, the dispersed particles agglomerated in the liquid paraffin to form a mass of number 1. microcapsules were formed, and good microcapsules could not be obtained.

Example 3 The same procedure as in Example 1 was carried out except that silicone oil was used instead of the distearyldimethylammonium chloride fine powder. As a result, there is no agglomeration of particles and the particle size is 5.
Good microcapsules of 0 to 300 μm were obtained.

The detergent containing these microcapsules had good foam removal during rinsing.

Example 4 The same operation as in Example 2 was carried out except that sodium percarbonate (passed through an I00 mesh sieve) was used instead of the distearyldimethylammonium chloride fine powder in Example 2. As a result, there was no agglomeration of particles and the particle size was 50~ Good microcapsules of 200 μm were obtained.

Claims (1)

[Claims] 1. (A) General formula (I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) (In the formula, R is hydrogen or a methyl group, and R^1 and R^2 are each of which is an alkyl group having 1 to 3 carbon atoms; (B) at least one water-insoluble or poorly water-soluble monomer; and (C) at least one water-soluble monomer. The core substance is dispersed in a dispersion solvent in which a copolymer containing a copolymer is dissolved, and then the resulting dispersion is further dispersed in a mixed solvent of an oil and a dispersion solvent, and then the dispersion solvent is removed. A method for producing characterized pH-sensitive microcapsules.