JPH024440A - Manufacture of capsule - Google Patents

Abstract

PURPOSE:To increase heat resistance and the like by dispersing a hydrophobic substance into water solution of a prepolymer of urea resin or melamine resin, starting formation of a resin film around the hydrophobic substance and then adding a thermoplastic high molecular material therein. CONSTITUTION:Molar ratio of formaldehyde to urea is set as 1:0-2.5 in urea resin, while molar ratio of formaldehyde to melamine is set as 2.5-7 in melamine resin, and both are prepared as water solution and reacted tor 1-3 hours at pH7.5-9, 60-80 deg.C to prepare a transparent liquid prepolymer. A hydrophobic substance is dispersed in said water solution of the prepolymer and the formation of a urea resin wall film or a melamine resin wall film is started to form around the hydrophobic substance, and then a capsule is formed by a thermoplastic high molecular water dispersion being added into the water solution. As the hydrophobic substance of core, alkylnaphthalene organic peroxide or the like is used.

Description

Detailed Description of the Invention (a) Purpose of the Invention [Field of Industrial Application] The present invention uses various hydrophobic substances, such as peroxides, amine compounds, polyisocyanates, etc. as core materials, to form thermoplastic polymers. The present invention relates to a method for producing a capsule body whose wall is made of a urea resin or melamine resin (hereinafter referred to as "urea resin etc. J") containing the following.

The capsule body obtained by the present invention not only ruptures under pressure and releases the core substance, but also partially ruptures the wall membrane by heating and gradually releases the core substance. Can be applied to materials, etc.

[Conventional technology]

Prepolymer of urea resin or melamine resin (hereinafter simply referred to as “
called "prepolymer". ) is a well-known method for encapsulating hydrophobic substances, and the resulting capsule bodies have been widely used in applications where the capsule is destroyed by pressure, such as in pressure-sensitive recording paper.

[Problem to be solved by the invention]

However, the wall membrane formed by this method is made of resin with an extremely high degree of crosslinking, and therefore it is difficult to destroy the capsule by heating, which limits the use of the capsule body.

On the other hand, methods of encapsulation using a thermoplastic wall such as gelatin, ethyl cellulose, or polystyrene have been considered, but these methods are less productive than the aforementioned capsules whose walls are made of urea resin or melamine resin. , which was disadvantageous in terms of cost.

Furthermore, the gelatin film has poor water resistance and oil resistance, and therefore the produced capsule bodies have the disadvantage of lacking stability.

(B) Structure of the invention [Means for solving the problem] The present invention involves dispersing a hydrophobic substance in an aqueous solution of a prepolymer of urea resin or melamine resin, and surrounding the hydrophobic substance with a urea resin wall. This method of manufacturing a capsule body is characterized in that after starting the formation of a membrane or a melamine resin wall membrane, an aqueous thermoplastic polymer dispersion is added to the aqueous solution.

The wall membrane of the capsule body obtained by the present invention has thermoplasticity and retains the heat resistance, water resistance, oil resistance, etc. originally possessed by urea resin, etc., and the present invention is directed to this capsule body. This makes it possible to produce commercially advantageously using a simple method.

The capsule body obtained by the present invention not only ruptures under pressure and releases the core substance, but also partially ruptures the wall membrane by heating and gradually releases the core substance, compared to conventional capsule bodies. It can be used in a wide range of applications, including adhesives, molding materials, heat-sensitive recording paper, etc.

In the case of adhesives, especially highly reactive thermosetting adhesives such as epoxy adhesives and polyurethane adhesives, curing agents such as peroxides or curing components such as amine compounds and isocyanate compounds are used in the method of the present invention. By encapsulating the adhesive, it is possible to obtain a one-component or two-component adhesive with slow-acting properties and a long pot life.

The capsule body of the present invention can also be applied to molding materials such as polyester resin for FRP and epoxy resin for mold formation.

For example, in the past, FRP was produced by applying a mixture of styrene monomer, unsaturated polyester, and peroxide to a glass fiber base material and polymerizing it. There was a problem in that the decomposition was rapidly accelerated, which further accelerated the reaction, resulting in coloring of the resulting FRP molded product.

Here, when a part of peroxide is encapsulated by the method of the present invention, the peroxide in the capsule starts to decompose only after the thermoplastic component in the capsule wall is destroyed by the heat of reaction. Therefore, the reaction as a whole can have a delayed effect.

In addition, since the thermoplastic polymer is swollen by styrene, even if all the peroxide is encapsulated, the reaction can be delayed.

The method for manufacturing a capsule body of the present invention is comprised of the following stepwise steps and technical elements.

(1) For prepolymer synthetic urea resins, the molar ratio of formaldehyde to urea is between 1.0 and 2.5, while for melamine resins, the molar ratio of formaldehyde to melamine is between 2.5 and 7.
Make an aqueous solution of both, place it in a container equipped with a rotating machine, and incubate at pH 7.5-9.60-80°C for 1-3.
By reacting for a period of time, a prepolymer in the form of a transparent aqueous solution can be obtained.

In this case, it is possible to replace a part of urea or melamine with each other, and further replace up to 30% by weight with other compounds that perform condensation reactions, such as guanamidine or p-)luenesulfonamide, to form a film. water resistance can be improved.

In order to increase the pH of the reaction system, an aqueous solution of caustic soda, aqueous ammonia, triethanolamine, etc. can be used, but triethanolamine is preferably used from the viewpoint of easy control of side reactions.

(2) For dispersion of hydrophobic substances in prepolymers (1)
A hydrophobic substance is dispersed into the aqueous prepolymer solution obtained in step 1.

When the hydrophobic substance is in powder or liquid form, it can be directly added to the aqueous solution and dispersed.

If the hydrophobic substance is in the form of coarse particles, there is a method in which it is dissolved in a hydrophobic solvent and then added.

For coarse peroxide particles, add a hydrophilic organic solvent to the aqueous prepolymer solution (or add the hydrophilic organic solvent directly to the peroxide to form a suspension and then mix together. When added to an aqueous prepolymer solution and dispersed, it can be easily made into a fine powder.

The hydrophilic organic solvent used is one that dissolves in the prepolymer aqueous solution, and specific examples include methanol, ethanol,
Examples include alcohols such as isopropanol; ester necks such as methyl acetate and ethyl acetate; ketones such as acetone, methyl ethyl ketone, and diethyl ketone; acetonitrile and dimethyl formamide; It is preferable that a capsule body having a diameter can be obtained.

The amount of these hydrophilic organic solvents used is preferably 20 to 300 parts by weight based on 100 parts by weight of the prepolymer in terms of solid content present in the reaction medium (aqueous solution). If it is less than 20 parts by weight, sufficient effects cannot be obtained, and if it exceeds 300 parts by weight, the methylenation reaction rate, that is, the encapsulation reaction rate decreases, and both are not preferred.

Note that the presence of an organic solvent that does not dissolve in the reaction medium must be avoided since the capsules will become extremely coarse particles.

Furthermore, in order to facilitate the dispersion at this stage, a nonionic or anionic surfactant or suspending agent may be added to the reaction system.

The ratio of the hydrophobic substance to the prepolymer is preferably 10 to 200 parts by weight per 100 parts by weight of the prepolymer in terms of solid content. If it exceeds 200 parts by weight, the strength of the resulting capsule film will be low;
If it is less than parts by weight, the film will be too thick and productivity will be poor.
Neither is preferable.

Furthermore, a portion of the prepolymer in the aqueous solution is condensed to produce a small amount of urea resin or melamine resin having methylene groups (hereinafter referred to as "methylene resin"), and then a hydrophobic substance is added. Dispersing is preferable than dispersing before the start of production of methylene resin because it is easier to form a dense film.

Specifically, the prepolymer aqueous solution was stirred with a homogenizer at a rotation speed of 3000 to 8000 rpm, and the pH was adjusted to 1.
, adjust to 5-4. For this pH adjustment, hydrochloric acid or sulfuric acid of about IN concentration, citric acid of a 10 to 30% by weight aqueous solution, or the like can be used.

While the prepolymer is water-soluble, the methylene resin is insoluble, and when the resin begins to form, the system becomes cloudy.
Its formation can be confirmed as it gradually becomes colloidal.

Furthermore, by filtering this, the amount produced can be confirmed.

When the production of methylene resin is confirmed by clouding of the reaction system, a fine powder or liquid hydrophobic substance is charged and dispersed by stirring for about 30 minutes to 1 hour.

Hydrophobic substances that can be used as core substances in the present invention include the following.

Those that are liquid at room temperature include alkylnaphthalene, chlorinated paraffin, soybean oil, or fragrance oil rings; esters such as acrylic esters, methacrylic esters, adipic esters, or phosphoric esters; aliphatic or aromatic amines. Compounds, polyisocyanates, etc. may be mentioned.

On the other hand, examples of substances that are solid at room temperature include organic peroxides, lead peroxide, amines, epoxy resins, magnetic powders, pigments, and finely powdered pharmaceuticals.

The amount of methylene resin present before the addition of the hydrophobic substance may be extremely small, but when the amount of the hydrophobic substance added is 100 parts by weight, it is preferably 0.1 to 20 parts by weight. If a hydrophobic substance is added to the system in the absence of methylene resin or in an amount less than 0.1 part by weight, agglomeration will occur between the hydrophobic substances, and they will either float on the liquid surface with air entrained or aggregate into lumps. However, a uniform encapsulation reaction may become impossible. Furthermore, it is preferable that the methylene resin is present in the aqueous medium before adding the hydrophobic substance.

On the other hand, if a hydrophobic substance is added in the presence of a large amount of methylene resin exceeding 20 parts by weight, it is not preferable because a capsule body containing no core substance is likely to be produced and the cost increases.

(3) Encapsulation reaction of hydrophobic substance After the above steps, when the temperature of the reaction system is adjusted to 30-60°C and stirring is continued, a film of urea resin or the like is formed around the hydrophobic substance.

If the stirring is continued for 3 to 30 hours thereafter, the coating content in the capsule increases, but the final coating content in the capsule is preferably 30 to 95% by weight.

If it is less than 30% by weight, the stability of the capsule during storage will decrease, and if it exceeds 95% by weight, the capsule will be difficult to break even at low pressure or temperature during use, and the efficiency in manufacturing the capsule will be poor. Neither is preferable.

The film content can be determined by adding a solvent in which the core substance is highly soluble to the capsule body, extracting the core substance for a long time using a Soxhlet, and measuring the remaining insoluble matter.

A feature of the present invention is that an aqueous thermoplastic polymer dispersion is added to an aqueous prepolymer solution during the formation of a capsule wall.

At this time, the timing and amount of addition of the thermoplastic polymer aqueous dispersion can be determined as appropriate depending on the purpose of use of the resulting capsule body, taking into consideration the balance between thermosetting properties due to urea resin etc. and newly imparted thermoplasticity. However, generally, when a film of urea resin or the like is formed in an amount of 10 to 60 parts by weight based on 100 parts by weight of the purest film, the thermoplastic polymer aqueous dispersion is converted into solid content. It is preferable to add 10 to 1000 parts by weight.

Specific examples of thermoplastic polymers used in the present invention include acrylic ester resins, methacrylic ester resins, vinylidene chloride resins, urethane resins, chloroprene polymers, butadiene-acrylonitrile copolymers, butadiene-styrene copolymers, Examples include emulsions of polyolefins, carboxyl-modified polyolefins, olefin-vinyl acetate copolymers, vinyl chloride-vinyl acetate copolymers, and the like.

Among these, it is preferable to use an emulsion of a thermoplastic polymer that is difficult to coagulate in an acidic aqueous medium and is not subject to modification such as hydrolysis, and specifically, vinylidene chloride resin,
Examples include emulsions of chloroprene polymers, polyolefins, and carboxyl group-modified polyolefins.

(4) Collection and drying of the capsule body After neutralizing the produced slurry with an IN aqueous solution of caustic soda, washing it thoroughly with pure water, dehydrating it with a centrifuge, and passing it through a fluidized fluid dryer or tray dryer. , a finely powdered capsule body can be obtained.

Since the capsule film partially has thermoplasticity, a strong and dense film can be preferably formed by increasing the drying temperature to near the melting point of the thermoplastic polymer.

[Effect]

In the present invention, the thermoplastic polymer aqueous dispersion needs to be present in the prepolymer aqueous solution after a wall film has been formed on the hydrophobic substance to some extent. This is because if added to the prepolymer aqueous solution from the beginning, particles of the hydrophobic substance tend to aggregate with each other, making encapsulation difficult.

[Examples and comparative examples]

The present invention will be explained in more detail by giving examples and comparative examples below.

In addition, the test method of JIS K 4810 is applied mutatis mutandis for the sensitivity test, and the measurement of Vicat softening point is according to ASTM D.
1525-70.

Example 1 700 g of a formalin aqueous solution with a concentration of 37, 262 g of urea, and 3.4 g of triethanolamine were placed in a flask equipped with a reflux condenser, and stirred at 300 rpm and 70°C for 2 hours to react. An aqueous prepolymer solution of urea-formaldehyde resin (prepolymer concentration 54.3% by weight) was obtained.

Next, 368 g of the prepolymer aqueous solution and 368 g of pure water were charged into 22 beakers at room temperature. While stirring at 400 rpm with a homogenizer, 7 cc of an aqueous IN sulfuric acid solution was added to adjust the pH to 3.0 and the reaction temperature to 37° C., resulting in white turbidity. After 1 minute, dicumyl peroxide fine powder (average particle size 100 μm) 1
After adding 2.8 g and continuing stirring for 1 hour, the temperature was raised to 40°C and the reaction was maintained for 4 hours under stirring at 5000 rpm.

Add 300g of pure water to this, remove the homogenizer, switch to a seed type stirrer, lower the rpm to 300rpm, and add low density polyolefin emulsion M-200 (
Solid content: 40% by weight, film forming temperature: 105°C, Vicat softening point: 76°C (manufactured by Mitsui Petrochemicals Ltd.) (212g) was charged and the reaction continued for an additional 15 hours to obtain a slurry.

In addition, the film content when low density polyolefin is added is 24
% by weight.

This slurry was neutralized with IN aqueous sodium hydroxide solution, washed with pure water and methanol, centrifuged, and dried for 10 minutes in a fluidized fluidized dryer with a hot air temperature of 110"C1 at the inlet and a hot air temperature of 80 to 90"C. , 80 g of capsule fine particles having a narrow average particle size of 150 μm in the particle size distribution were obtained.

This capsule body had a film content of 84% by weight, and a polyolefin content in the film of 88% by weight. In addition, this capsule body can withstand 5kg from a height of 1m in a calm sensitivity test.
I dropped the weight and could not see the sensitivity.

When the melt-flowing state of this capsule was observed using a microscope, it was found that the capsule film was destroyed at around 110°C. Note that the microscopy method is a method in which a heater is set under the sample and the sample is heated for a certain temperature increase time, and the melt flow of the sample is observed under a microscope and its temperature is measured.

These results are shown in Table 1.

Examples 2 to 4, Comparative Examples 1 to 2 The type and amount of thermoplastic polymer aqueous dispersion used instead of the low density polyolefin emulsion in Example 1, the type of core material, or the inlet hot air temperature and drying of fluidized drying Table 1 shows the results obtained when manufacturing and testing were carried out in exactly the same manner as in Example 1, except that the times were changed as shown in Table 1.

Example 5 700 g of a 37% by weight aqueous formalin solution, 132 g of melamine, and 3.4 g of triethanolamine were placed in a flask No. 11 equipped with a reflux condenser, and the mixture was heated at 300 rpm and 70"C.
The mixture was stirred for 2 hours to react, and an aqueous prepolymer solution of melamine-formaldehyde resin having a pH of 8.5 (prepolymer solid content concentration: 47.2% by weight) was obtained.

Next, 426 g of the prepolymer aqueous solution and 309 g of pure water were charged into 22 beakers at room temperature. While stirring at 500 rpm with a homogenizer, the pH was adjusted to 4.0 by adding 3 cc of an IN aqueous solution of hydrochloric acid, and the reaction temperature was heated to 40°C, resulting in white turbidity. After 1 minute, 29.8 g of triethyltetramine was charged, and stirring was continued for 1 hour, then the temperature was raised to 60°C, and the reaction was maintained for 1 hour while stirring at 5000 rpm.

Add 300g of pure water to this, remove the homogenizer, switch to a seed stirrer, lower the rpm to 300rpm, and add styrene-butadiene copolymer emulsion N1.
polLX416 (solid content 48% by weight, film formation temperature 5
0″C, glass transition temperature 39°C, manufactured by Zeon ■) 178
The reaction was continued for an additional 2 hours to obtain a slurry.

This slurry was neutralized with IN aqueous sodium hydroxide solution, washed with pure water and methanol, centrifuged, and dried for 30 minutes in a fluidized fluid dryer with a hot air temperature of 60°C at the inlet and a hot air temperature of 40 to 50°C. 130 g of capsule fine particles having an average particle size of 30 μm were obtained. Further, this capsule body had a film content of 77% by weight.

50 g of this capsule body and 50 g of bisphenol type epoxy resin Epicoat 82B (manufactured by Shell Kagaku ■) were mixed and left at 30''C for 2 months, but no hardening of the epoxy resin was observed.

Furthermore, when the melt-flow state was observed using a microscope, it was found that the capsule film was destroyed at around 70°C. These results are shown in Table 1.

Examples 6 to 7 The type and amount of thermoplastic polymer aqueous dispersion used instead of the low-density polyethylene emulsion in Example 2, the type of core material, or the inlet hot air temperature and drying time of fluidized drying were changed as shown in Table 1. Table 1 shows the results obtained when manufacturing and testing were carried out in exactly the same manner as in Example 2, except for the following.

(c) Effects of the invention The wall membrane of the capsule body obtained by the present invention has thermoplasticity and retains the heat resistance, water resistance, oil resistance, etc. originally possessed by urea resin, etc. The present invention has made it possible to commercially advantageously produce this capsule body by an hour wheel method.

The capsule body obtained by the present invention not only ruptures under pressure and releases the core substance, but also partially ruptures the wall membrane by heating and gradually releases the core substance. It can be used in highly reactive thermosetting adhesives such as polyurethane adhesives and polyurethane adhesives to produce one-component or two-component adhesives with slow-acting properties and a long pot life.

Furthermore, it can be used in polyester resins for FRP and epoxy resins for mold molding to obtain molding materials without coloring.

Claims (1)

[Claims] 1. After dispersing a hydrophobic substance in an aqueous solution of a urea resin or melamine resin prepolymer and starting the formation of a urea resin wall film or a melamine resin wall film around the hydrophobic substance,
A method for producing a capsule body, which comprises adding an aqueous thermoplastic polymer dispersion to the aqueous solution.