JPH0578411A - Microencapsulated curing agent, its production, unsaturated polyester resin composition containing the same curing agent and method for curing and stabilizing the same - Google Patents

Abstract

PURPOSE:To obtain the subject curing agent, composed of a core substance of an organic peroxide for an unsaturated polyester resin and a film substance, soluble at a curing temperature and having the inside of a polyelectrolyte and the outside of a specific polymer, excellent in storage stability and pot life and providing sharp curing. CONSTITUTION:The objective microencapsulated curing agent is obtained by adding an organic peroxide which is a solid at ordinary temperature and has at least 5 deg.C difference between the melting point and the thermal decomposition temperature for forming a core to an aqueous solution of a substance for forming an inner film containing a polyelectrolyte, producing a liquid mixture at a temperature below the thermal decomposition temperature, then cooling the liquid mixture, forming grains composed of the organic peroxide core and the inner film, subsequently adding a monomer composed of at least one of an acrylic acid ester, a methacrylic acid ester and a vinyl aromatic compound for forming an outer resin film and forming a resin film of the polymerized monomer on the inner film. The above-mentioned curing agent is soluble at the curing temperature of the unsaturated polyester resin and contains the core substance which is the organic peroxide for curing the unsaturated polyester resin in the interior.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a curing agent for unsaturated polyester resins. Specifically, it is easy to handle and work, and is stable in the unsaturated polyester resin. When the resin is cured, a microcapsule containing a curing agent as a core substance that enables rapid curing. The present invention relates to a curing agent, a method for producing the curing agent, an unsaturated polyester resin composition containing the curing agent, a method for curing an unsaturated polyester resin, and a method for producing an unsaturated polyester resin composition having high storage stability.

[0002]

2. Description of the Related Art Conventionally, an unsaturated polyester resin is blended with glass fiber, an inorganic filler, a thickener, a stabilizer, a release agent, etc., and a curing agent is added to heat-cure or, if necessary, a curing accelerator. It is widely used for FRP molding by compounding and curing at room temperature.

Organic peroxides are generally used as a curing agent for unsaturated polyester resins, but the resin liquid containing the curing agent has a pot life, and for example, gels because it gels. The liquid cannot withstand long-term storage.
Therefore, at present, two of the resin and the curing agent or the three of the curing accelerator are mixed and used immediately before use. On the other hand, practically, there is a strong demand for a curing agent that has a long pot life of the resin liquid and that is rapidly cured at the curing temperature of the unsaturated polyester resin. In particular, a curing agent that acts at a lower temperature is desired from the viewpoint of productivity. However, the lower the curing temperature, the worse the stability of the curing agent in the resin. Various studies have been conducted for the purpose of satisfying these conflicting conditions.
As a result, it has been confirmed that the above drawbacks can be eliminated by encapsulating the curing agent in microcapsules, and in recent years, development of microencapsulated curing agents has been actively conducted. For example, JP-A-48-7086 discloses a crystalline or amorphous polymer substance obtained by natural or synthetic liquid or solid organic peroxide colored with a dye or pigment, such as gelatin or polystyrene. A curable composition comprising a coated hardener capsule and an unsaturated polyester resin, which is stable at room temperature and has curability at a predetermined temperature, is disclosed.
However, colored hardener capsules cannot be used for transparent moldings. Further, JP-A-57-12017 contains microcapsules of a liquid or solid organic peroxide having a temperature of 74 to 158 ° C. for obtaining a half-life of 10 hours and a curing accelerator such as cobalt naphthenate. Low temperature,
Unsaturated polyester resin suitable for sheet molding compound (SMC) that can be compression molded at low pressure
Furthermore, JP-A-59-502018 discloses a reinforced polyester resin containing microcapsules of a liquid or solid curing agent, which are isolated from the polyester resin until they are released under predetermined process conditions. A method of making the product is disclosed.

[0004]

However, in a microencapsulated product of an organic peroxide that is liquid at room temperature, the core substance actually gradually dissolves the membrane substance, and the stability of the core substance itself and the unsaturated polyester compounded with it are obtained. The stability of the resin composition is impaired. Further, when solid organic peroxides are directly encapsulated in microcapsules, the problems of the above-mentioned known curing agents are not solved, and it is difficult to completely cover with a film substance due to the shape and surface condition of the core substance. Has the drawback of being

Further, the curing of the unsaturated polyester resin is generally achieved by using a very small amount of the curing agent, and when the curing agent is microencapsulated, the resin which is not microencapsulated at all is a resin. If it is contained in the composition, it will start to cure and the storage stability will be significantly impaired. Further, when the hardener is coated with a strong film, there is a possibility that hardening delay or uneven hardening may occur during hardening. In this way, simply encapsulating the curing agent
It is not easy to obtain an unsaturated polyester resin composition which cures rapidly upon curing and has good storage stability.

Further, in SMC obtained by blending unsaturated polyester resin with glass fiber, filler, etc.,
When the hardener is microencapsulated, the microcapsules are destroyed by friction of the reinforcing agent, and it is difficult to maintain the above performance. Further, it is not easy to completely destroy the capsule film and effectively disperse the curing agent in the resin only by applying pressure or heating.

[0007]

Means for Solving the Problems The present inventors have found that the handling and workability are good, the storage stability of the resin is not impaired when the resin is mixed with an unsaturated polyester resin, and the resin is promptly cured upon curing. Moreover, as a result of research for the purpose of developing a curing agent for unsaturated polyester resin in which an organic peroxide that enables uniform curing is encapsulated in a microcapsule, a specific organic peroxide can be obtained by a specific means. The present invention has been completed by confirming that the purpose can be achieved by the encapsulated curing agent.

That is, the present invention is (a) solid at room temperature,
A core substance which is an unsaturated polyester resin curing organic peroxide having a difference between the melting point and the thermal decomposition temperature of at least 5 ° C .;
(B) Unsaturated polyester resin, which has no reactivity with the core substance, is solid at room temperature, has a property of dissolving at the unsaturated polyester resin curing temperature, the inner coating is made of a polymer electrolyte, and the outer coating is Microencapsulating curing agent for unsaturated polyester resin consisting of a film substance covering a core substance consisting of one or more of acrylic acid ester, methacrylic acid ester and vinyl aromatic; A core-forming organic peroxide, which is a solid and has a difference between the melting point and the thermal decomposition temperature of at least 5 ° C., is added to form a liquid mixture at a temperature equal to or lower than the thermal decomposition temperature, and then the liquid mixture is cooled to cool the organic mixture. Particles composed of a peroxide core and an inner film are formed, and then at least one kind of a monomer for forming an outer resin film is added to form a monomer-polymerized resin film on the inner film. Method for producing microencapsulating curing agent for unsaturated polyester resin; unsaturated polyester resin composition comprising unsaturated polyester resin and the aforementioned microencapsulating curing agent; curing unsaturated polyester resin with curing agent of the present invention The present invention relates to a method and a method for producing an unsaturated polyester resin composition having high storage stability, which comprises adding the curing agent of the present invention to an unsaturated polyester resin.

The core substance used in the present invention is at room temperature (2
It is an organic peroxide that is solid at 0 ° C., and examples thereof include dimyristyl peroxydicarbonate, didecyl peroxy carbonate, and dicetyl peroxy carbonate as peroxydicarbonates, and dicumyl peroxide, α, Examples of ketone peroxides such as α'-bis (t-butylperoxy) -m-isopropylbenzene and α, α'-bis (t-butylperoxy) -p-isopropylbenzene include cyclohexanone peroxide and 1,1-dihydroxydicyclohexyl. Peroxyesters such as peroxides include 2,5-dimethyl 2,5-di (benzoylperoxy) hexane and di-t-butyldiperoxyisophthalate, and peroxyketals include
1,1-bis (t-butylperoxy) cyclododecane, 1,3-diphenyl 2,2-bis (t-butylperoxy) propane, 1-phenyl 3,3-bis (t-butylperoxy) butane, 1- Benzoyl 2-methyl 2,2-bis (t-butylperoxy) ethane, 1,1
Examples of diacyl peroxides such as -bis (t-butylperoxy) cyclododecane include didecanoyl peroxide, dilauroyl peroxide, bis (o-methylbenzoyl) peroxide, and bis (m-methylbenzoyl).
Hydroperoxides such as peroxide are 2,5
-Dihydroperoxy 2,5-dimethylhexane α-,
Examples thereof include α'-bis (hydroperoxy) -m-isopropylbenzene and the like, and if they satisfy the above-mentioned conditions, they can be used as a mixture of two or more kinds thereof or a mixture with another diluent medium.

Curing of the unsaturated polyester resin is initiated by heating, but the intermediate temperature curing of 50 to 100 ° C. and 1
It is classified as high temperature curing that cures at 00 ° C or higher. In the former case, the organic peroxide which is a curing agent is preferably peroxydicarbonates, diacyl peroxides, ketone pesoxides, peroxyketals, hydrooyl oxides or peroxyesters, and used alone or in combination with a curing accelerator. To be done. The latter is preferably peroxyketals, peroxyesters or dialkyl peroxides.

Table 1 shows melting points and thermal decomposition temperatures of typical organic peroxides. Regarding the melting point of the organic peroxide,
It is possible to mix and lower other substances and it can be used within a range that does not hinder the practice of the present invention.
However, in this case, the range of the melting point is widened, and therefore it is preferable to use them alone if further rapid curing is expected. The thermal decomposition temperature is the heating test method described in the magazine "Safety Engineering" (Hiro Kitagawa et al .: Safety Engineering, Vol. 4, No. 2, P133-1).
34, 136, 1965), and specifically means the temperature at which decomposition of the organic peroxide begins to occur rapidly when the temperature of the organic peroxide is increased at a constant rate. ..

[Table 1]

Next, a method for producing the microencapsulated curing agent of the present invention will be described. That is, the above-mentioned organic peroxide which is solid at room temperature and has a difference between the melting point and the thermal decomposition temperature of at least 5 ° C. is used to form a fine particle melt of 1 to 200 μm above the melting point and below the thermal decomposition temperature in an aqueous system. It is generated, and its surface is covered with a polymer electrolyte by a coacervation method which is a known microencapsulation method to form an inner film. Details of the coacervation method are described in "Latest Microencapsulation Technology" by Sogo Gijutsu Center. As the polyelectrolyte in the coacervation method, for example, gelatin, casein, gum arabic,
Sodium alginate, carboxymethyl cellulose, polyvinyl alcohol, methyl vinyl ether, maleic anhydride copolymer and the like can be used, and can be cured with formaldehyde, glutaraldehyde and the like. Then, an outer film-forming monomer and a polymerization initiator are added and polymerized at a temperature equal to or lower than the melting point of the organic peroxide, and the organic peroxide covered with the polyelectrolyte is further converted into a polymer of the monomer. By covering with an outer coating, the microencapsulating curing agent for unsaturated polyester resin of the present invention having a particle size of 1 to 200 μm can be obtained.

Specific examples of the monomer used for the production of the polymer forming the outer film in the present invention are as follows. Methyl acrylate and / or methyl methacrylate [hereinafter collectively referred to as (meth) acrylate). The same applies hereinafter], ethyl (meth) acrylate, (meth)
Lower alkyl (meth) acrylates such as n-propyl acrylate, (meth) acrylate-n-butyl,
Higher alkyl (meth) acrylic acid esters such as (meth) acrylic acid-n-hexyl, (meth) acrylic acid-2-ethylhexyl, and lauryl (meth) acrylate, diethylene glycol di (meth) acrylate, di (meth) acrylic Acid triethylene glycol, di (meth) acrylic acid decaethylene glycol, di (meth) acrylic acid 1,3
-Multifunctional (meth) acrylic acid esters such as butylene, trimethylolpropane tri (meth) acrylate, pentaerythryl tetra (meth) acrylate, diethylene glycol di (meth) acrylate, styrene, α-methyl Examples include vinyl aromatics such as styrene, vinyltoluene, and divinylbenzene. One or two or more of these monomers are appropriately selected and used, but it is preferable to use another functional monomer in order to increase the denseness of the outer coating.

The outer film is formed by polymerizing the above-mentioned monomer using an organic peroxide or a water-soluble inorganic peroxide by a redox system in which heat or a reducing agent is used in combination.

The unsaturated polyester resin used in the present invention is (a) an unsaturated dibasic acid such as maleic anhydride, maleic acid, fumaric acid, mesaconic acid, tetraconic acid, itaconic acid, chlorinated maleic acid and saturated dibasic acid. Phthalic acid as acid, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, halogenated phthalic anhydride, adipic acid, succinic acid, sebacic acid and polyhydric alcohol ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, butylene glycol, Neopentyl glycol, hexylene glycol,
Hydrogenated bisphenol A, 2,2-di (4-hydroxyethoxyphenyl) propane, 2,2-di (4-hydroxyethoxyphenyl) propane, ethylene oxide,
Propylene oxide, etc. at a specific ratio under a nitrogen stream 17
It is a mixture of an alkyd resin obtained by dehydration condensation at 0 to 200 ° C. and (b) a crosslinkable monomer such as styrene, o-chlorostyrene, vinyltoluene, methyl methacrylate, diallyl phthalate and triallyl isocyanate.

The curing agent obtained by microencapsulation used in the present invention can be used alone or in combination with a curing accelerator which forms a redox system. Examples of the curing accelerator include cobalt naphthenate. Examples thereof include metal salts of higher fatty acids, thioureas such as benzoylthiourea and ethylenethiourea, ethylenediamine, L-ascorbic acid and sodium p-toluenesulfinate. Since accelerated curing differs depending on the combination with a curing agent, it is necessary to select it appropriately.

In the curing agent for unsaturated polyester resin comprising the microencapsulated curing agent and the curing accelerator forming the redox system of the present invention, the organic peroxide content and the curing accelerator in the microencapsulated curing agent are Of 90/10 to 10/90 depending on the desired cure rate.
It can be selected in the ratio of (weight ratio).

In the unsaturated polyester resin composition of the present invention, the pure content of the organic peroxide in the curing agent for unsaturated polyester resin is 0.1 to 5 parts by weight, preferably 100 parts by weight of the resin. 0.5 to 3 parts by weight. 0.1
If it is less than 5 parts by weight, the action as a curing agent is insufficient, and if it is used in excess of 5 parts by weight, the action of the curing agent is equivalent to that of 5 parts by weight, which is not economically preferable.

In the unsaturated polyester resin composition of the present invention, glass fibers such as roving cloth, chopped strands and chopped strand mats, or reinforcing agents such as carbon fibers, calcium carbonate and clay are used for the purpose of improving the strength of molded articles. , A filler such as aluminum hydroxide can be blended, and the blending amount is 1 of the total amount.
It is 0 to 90% by weight, and if the amount is too small or too large, the strength of the molded product is remarkably reduced, which is not preferable. Further, depending on the purpose, thickeners such as oxides or hydroxides of alkaline earth metals such as magnesium oxide, low shrinkage agents such as thermoplastic resins, copolymers thereof, block / graft copolymers, stearin, etc. A release agent such as zinc acid or a polymerization inhibitor such as benzoquinone can be used.

The curing temperature of the unsaturated polyester resin in the present invention can be appropriately selected according to each molding method and is expressed as a molding temperature. For example, molding of resin concrete, continuous molding of corrugated sheet or flat plate, filament winding molding or resin injection molding is performed at 50 to 100 ° C., and peroxydicarbonates, diacyl peroxides, ketone peroxides, peroxyketals, hydroperoxides are formed. Alternatively, a curing agent obtained by microencapsulating an organic peroxide of peroxyesters is used alone or in combination with a curing accelerator that forms a redox system. Further, SMC, bulk molding compound (BMC) or matched die molding is performed at 100 ° C. or higher, and a curing agent in which peroxyketals, peroxyesters or dialkyl peroxides are microencapsulated is used.

[0021]

As described above, the microencapsulated curing agent of the present invention has several excellent characteristics because it is obtained by using a specific means for a specific organic peroxide. There is.

First, in the microencapsulated curing agent of the present invention, a core substance is a solid organic peroxide, and a polymer electrolyte such as gelatin is formed as an inner film around the core substance, and an acrylic acid ester, a methacrylic acid ester and a vinyl aroma are used. Since the membrane material having a polymer of one kind or a mixture thereof as an outer coating forms a thin partition wall that is insoluble and impermeable, the microcapsules themselves have excellent storage stability, and a microencapsulated curing agent. Curing agents consisting of curing accelerators are much more storage stable than curing agents consisting of the same non-microencapsulated organic peroxide and curing accelerator. Further, the microencapsulated curing agent of the present invention has a spherical appearance because the outer layer is covered with a lipophilic resin film,
Compared to a microencapsulating curing agent in which the same organic peroxide is covered only with a polyelectrolyte such as gelatin, the filtration and drying times during production are shorter, so handling and workability are better, and unsaturated polyester resin Good dispersibility.
Further, the unsaturated polyester resin composition of the present invention obtained by mixing a microencapsulated curing agent or a curing agent composed of a microencapsulated curing agent and a curing accelerator with an unsaturated polyester resin is a microcapsule film material. In order to prevent the penetration of the crosslinkable monomer in the unsaturated polyester resin by the polymer of a certain polyelectrolyte and the above-mentioned monomer, the same non-microencapsulated organic peroxide or a curing agent consisting of it and a curing accelerator is mixed. A resin composition obtained by
And a resin composition prepared by coating the same organic peroxide only with a polyelectrolyte such as gelatin, or a resin composition obtained by mixing a curing agent containing the same and a curing accelerator, and having a much longer pot life or a felt. Have a life.

When the solid organic peroxide undergoes a physical change from the solid state to the liquid state at the melting point, it causes a rapid volume increase. That is, when the unsaturated polyester resin is cured, the microencapsulated curing agent of the present invention liquefies the organic peroxide which is the core substance by heating, and increases the volume to destroy the membrane substance and rapidly destroy the film. It enables curing of the saturated polyester resin. Further, the destruction is promoted by pressure, mechanical friction and the like.

Thus, the microencapsulated curing agent of the present invention and the unsaturated polyester resin composition containing the same have excellent handling and workability, excellent storage stability, and a long pot life / shell life. When curing, it enables a sharp curing reaction at the start.

[0025]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples. In the examples, parts represent parts by weight. [Production of Microencapsulated Curing Agent for Unsaturated Polyester Resin of the Present Invention] Example 1 8 g of gelatin, 8 g of gum arabic and 500 g of water were added to a 4-necked flask equipped with a stir bar, thermometer and reflux condenser. And mix, and while stirring, bring the temperature in the system to 45 ° C.,
50 g of dimyristyl peroxydicarbonate was added to this aqueous solution. Next, the temperature in the system is adjusted to 50 ° C. to melt the dimyristyl peroxydicarbonate, and after stirring for about 5 minutes, a 50% acetic acid aqueous solution is added to adjust the pH to 4.4.
Adjusted to. After this, the temperature of the solution is kept at 10 ° C for about 20 minutes.
Lowered. Then, 6 ml of 37% aqueous formaldehyde solution was added and stirred for 4 minutes, and then the pH was adjusted to 9.0 with 10% aqueous sodium hydroxide solution and stirred for 2 hours. Next, 250 g of water was added, the temperature was raised to 35 ° C., 1% aqueous solution of polyvinyl alcohol was added, and then methyl methacrylate (M
MA) and trimethylolpropane triacrylate (TM)
PT) mixture (MMA / TMPT = 2/8, no weight)
250 g and diisobutyryl peroxide (trade name Perloyl IB, manufactured by NOF CORPORATION) were added to the mixture of MMA and TMPT in an amount of 2% by weight, and the mixture was heated at 35 ° C. for 4 hours to polymerize MMA and TMPT to form an outer polymer. A film was formed. Dimyristyl peroxy which is not encapsulated with a mixed solution of n-hexane and ethanol (mixing ratio 50/50, volume ratio) after being filtered through a polypropylene filter cloth (trade name P254, Shikishima Canvas Co., Ltd.) for 15 minutes. The dicarbonate was washed. Then, it was dried to obtain 273 g of a curing agent having an average particle size of 50 μ which was microencapsulated with an inner gelatin film and an outer polymer film containing 15.8% of pure dimyristyl peroxydicarbonate. Electron microscope (J
It was found by observation with EOL JSM-T300, manufactured by JEOL Ltd. that each particle had a uniform spherical shape.

Example 2 In accordance with Example 1 except that the ratio of MMA to TMPT was changed to 5/5 (weight ratio) in Example 1, 15.9% pure dimyristyl peroxydicarbonate was contained. 274 g of a curing agent having an average particle diameter of 55 μm was obtained. Example 3 An average particle size containing 15.1% of pure dimyristyl peroxydicarbonate according to Example 1 except that the ratio of MMA to TMPT was changed to 8/5 (weight ratio). 250 g of 60 μ hardener was obtained. Example 4 In Example 1, the amount of the mixture of MMA and TMPT was adjusted to 10
In the same manner as in Example 1 except that the amount was changed to 0 g, 132 g of a curing agent containing 26.8% of pure dimyristyl peroxydicarbonate and having an average particle diameter of 70 μm was obtained.

Example 5 In Example 1, the amount of the mixture of MMA and TMPT was changed to 35.
According to the same manner as in Example 1 except that the amount was changed to 40 g, 40 g of a curing agent containing 66.6% of pure dimyristyl peroxydicarbonate and having an average particle size of 75 μ was obtained. Example 6 In Example 1, cyclohexanone peroxide was used as the organic peroxide, melted at 75 ° C., and 250 g of a mixture of styrene and divinylbenzene (5/5, weight ratio) was used as the outer film forming monomer. Butyl peroxy 2-ethylhexanoate (trade name perbutyl O,
(Nippon Yushi Co., Ltd.) was added to the monomer mixture in an amount of 1% by weight, and the mixture was heated at 75 ° C. for 5 hours to polymerize the monomer. 270 g of curing agent containing 5% and having an average particle diameter of 55 μ
Got

[Production of Unsaturated Polyester Resin Composition of the Present Invention] Example 7 A curing agent in which 100 parts of a reactive unsaturated polyester resin in an ortho type is microencapsulated with dimyristyl peroxydicarbonate obtained in Example 1. 2.5 as pure content
To obtain an unsaturated polyester resin composition. This composition is then applied to # 450 Glass Mat 2
It was laminated on one sheet and wrapped with a polyester film, and the time until gelation occurred in an incubator at 10 ° C. was measured, and the time was defined as the pot life. The results are shown in Table 2. Example 8 The pot life was measured according to Example 7 except that the curing agent obtained in Example was used. The results are shown in Table 2. Example 9 The pot life was measured according to Example 7 except that the curing agent obtained in Example 3 was used. The results are shown in Table 2.

Example 10 The pot life was measured according to Example 7 except that the curing agent obtained in Example 4 was used. The results are shown in Table 2. Example 11 The pot life was measured according to Example 7 except that the curing agent obtained in Example 5 was used. The results are shown in Table 2. Example 12 A curing agent was obtained by mixing 100 parts of the cyclohexanone peroxide microencapsulating curing agent obtained in Example 6 with 20 parts of cobalt naphthenate. Next, 100 parts of the ortho-based reactive unsaturated polyester resin was mixed with 16 parts of the above-mentioned curing agent to give an unsaturated polyester resin composition, and the pot life was measured in the same manner as in Example 7. The results are shown in Table 2.

[Curing Method for Unsaturated Polyester Resin Composition of the Present Invention] Example 13 100 parts of ortho-based reactive unsaturated polyester resin was mixed with 1 part of the microencapsulated curing agent obtained in Example 5 in a pure content. To obtain an unsaturated polyester resin composition. Then, this composition was laminated on three pieces of # 450 glass mat, and a thermocouple was inserted and cured in a convection constant temperature bath at 60 ° C. to obtain gel time (GT) and curing time (C
T) and hardness were measured. The results are shown in Table 3.

Comparative Example 1 The pot life was measured according to Example 7 except that 2.5 parts of non-microencapsulated dimyristyl peroxydicarbonate was used as a curing agent. The results are shown in Table 2.
Shown in. Comparative Example 2 Example 1 except that 2.1 parts of non-microencapsulated cyclohexanone peroxide was used as the curing agent.
The pot life was measured according to 3. The results are shown in Table 2. Comparative Example 3 80 g of microcapsules containing 15.5% of pure methyl ethyl ketone peroxide were obtained according to Example 1 except that methyl ethyl ketone peroxide (trade name Permec N, manufactured by NOF CORPORATION) was used as the organic peroxide and washed with ethanol. It was Since the core substance is a liquid organic peroxide, the microcapsule film is easily broken in the washing process, and the yield is considerably deteriorated. Then, the pot life was measured according to Example 12 except that microencapsulated methyl ethyl ketone peroxide was used as a curing agent. The results are shown in Table 2.

Comparative Example 4 316 g of 5.06% gelatin aqueous solution and 316 g of 5.06% arabic gum aqueous solution were mixed, the temperature of the system was raised to 45 ° C. with stirring, and 100 g of dimyristyl peroxycarbonate was added to this aqueous solution. .. Further, 400 g of distilled water at 60 ° C. was added to bring the temperature in the system to 50 ° C. to melt the dimyristyl peroxycarbonate. After melting and stirring for 5 minutes, add 50% acetic acid aqueous solution to adjust pH to 4.4.
Adjusted to. After this, the temperature of the solution is kept at 20 ° C for about 20 minutes.
Lowered. Then, 6 ml of 37% aqueous formaldehyde solution was added and stirred for 4 minutes, and then the pH was raised to 9.0 using 10% aqueous sodium hydroxide solution and stirred for 15 minutes. A dimyristyl peroxycarbonate dispersion having an average particle diameter of 30 μm was obtained by the above treatment. 33 ° C warm water 1
Washed twice with 000ml, polypropylene filter cloth (P
254) for 3 hours. Then, the non-encapsulated dimyristyl peroxycarbonate was washed with a mixed solution of n-hexane and ethanol (polymerization ratio 50:50, volume ratio). Then, it was dried to obtain 70 g of a curing agent having an average particle diameter of 35 μm which was microencapsulated with a gelatin film containing 85% by weight of pure dimyristyl peroxycarbonate. Observation with an electron microscope revealed that the particles were clustered in a tuft of grapes. The pot life was measured according to Example 7 except that 3 parts of the obtained curing agent was used. The results are shown in Table 2.

Comparative Example 5 GT, CT and hardness were measured according to Example 5 except that 1 part of non-microencapsulated dimyristyl peroxydicarbonate was used as a curing agent. The results are shown in Table 3.
Shown in.

[Table 2]

[Table 3]

From Table 2, the unsaturated polyester resin containing the microencapsulated curing agent of the present invention alone or the curing agent combined with the curing accelerator forming the redox system has a much longer pot life than the comparative examples. It was confirmed that it was stabilized. Further, in Table 3, it is a measure of the sharpness of the rising of the curing (CT-GT) / CT
It was confirmed that the curing agent of the present invention was fast-curing because the value of was smaller than that of the comparative example.

Claims (6)

[Claims] 1. A core material which is (a) an organic peroxide for curing an unsaturated polyester resin which is solid at room temperature and has a difference between a melting point and a thermal decomposition temperature of at least 5 ° C., and (b) an unsaturated polyester. Resin, having no reactivity with the core substance, being solid at room temperature and having a property of dissolving at the unsaturated polyester resin curing temperature, the inner film is a polyelectrolyte, the outer film is an acrylic ester, a methacrylic acid ester and A microencapsulating curing agent for unsaturated polyester resin, which comprises a film material covering the core substance made of a polymer of one kind or a mixture of two or more kinds of vinyl aromatic. 2. A core-forming organic peroxide, which is solid at room temperature and has a difference between the melting point and the thermal decomposition temperature of at least 5 ° C., is added to the aqueous solution of the inner film-forming substance, and the temperature is lower than the thermal decomposition temperature. Forming a liquid mixture, then cooling the liquid mixture to form particles consisting of an organic peroxide core and an inner coating,
Next, at least one of the monomers for forming the outer resin film is added,
A method for producing a microencapsulated curing agent for unsaturated polyester resin by forming a monomer-polymerized resin film on the inner film. 3. A curing agent for unsaturated polyester resin comprising the microencapsulated curing agent for unsaturated polyester resin according to claim 1 and a redox curing accelerator. 4. An unsaturated polyester resin composition comprising an unsaturated polyester resin and the curing agent according to claim 1 or 3. 5. A method for curing an unsaturated polyester resin, which comprises curing the unsaturated polyester resin with the curing agent according to claim 1. 6. A method for producing an unsaturated polyester resin composition having high storage stability, which comprises adding the curing agent according to claim 1 to an unsaturated polyester resin.