JPH03220246A - Microcapsuled amine curative - Google Patents

Abstract

PURPOSE:To prepare the title curative giving an adhesive excellent in the storage stability at room temp. and adhesive properties under heating by microcapsuling an amine curative having a specified m.p. as the core material with a thermoplastic resin having a specified softening point as the shell material. CONSTITUTION:The title curative is prepd. by microcapsuling an amine curative having an m.p. of 40-150 deg.C (e.g. hexamethylenediamine) as the core material with a thermoplastic resin having a softening point of 40-200 deg.C (e.g. polyvinyl butyral) as the shell material by solvent evaporation spray drying, etc. The prepd. curative is mechanically stable at room temp., breaks the capsule and releases the curative component when heated to a temp. higher than the softening point of the resin, thus enabling the production of an adhesive excellent in the storage stability, adhesive properties, etc.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention is always useful! Mechanically stable at temperatures (usually below 40°C),
Regarding microcapsule type amine curing agents whose capsules are destroyed by heating and the curing agent is released, if such microcapsules are used, it is possible to obtain, for example, epoxy resin adhesives having excellent storage stability.

[Conventional technology]

Resins such as epoxy, urethane, and polysulfide resins are used in adhesives, sealants, etc., and their applications are diversifying. Encapsulation has been attempted (for example, Japanese Patent Laid-Open No. 76935/1983).

[Problem to be solved by the invention]

Such microcapsules have hard wall materials and easily break under external pressure to release the curing agent, so they have poor storage stability when used as adhesives.Furthermore, since they are encapsulated using an interfacial polymerization method, they are difficult to manufacture during production. There was a problem of poor workability.

In addition, particularly highly reactive amine curing agents are difficult to select for wall materials and to encapsulate, so there are currently no practical ones.

[Means to solve the problem]

The present invention was made to solve these problems, and provides a mechanically stable microcapsule type amine curing agent.

That is, the present invention uses an amine curing agent with a melting point of 40 to 150°C as a core material, and a wall material enclosing the core material has a softening point of 40°C.
The present invention relates to a microcapsule type amine curing agent characterized by being a thermoplastic resin having a temperature of 0 to 200°C.

The amine curing agent as the core material of the present invention is used at room temperature (usually 2
It is solid at a temperature of 0 to 40°C) and has a melting point of 40 to 150°C, preferably 60 to 100°C. At temperatures below 40°C, the core material collapses and the mechanical strength of the resulting capsule decreases.
If the temperature exceeds 150°C, it will be difficult for the curing agent to be released when the capsule is destroyed.

Specific examples of such amine-based curing agents include polymethylene diamines such as hexamethylene diamine, octamethylene diamine, and decane methylene diamine, aromatic amines such as metaphenylene diamine, diaminodiphenyl/thane, and diaminodiphenylsulfone, and bis(4 -aminocyclohexyl)methane, polyamide polyamine, and the like.

The wall material used in the present invention has a softening point of 40 to 200°C,
Preferably it is a thermoplastic resin having a temperature of 60 to 150°C.

In particular, thermoplastic resins having a softening point higher than the melting point of the amine curing agent are preferred. Here, the softening point is VtCA
It was measured by the T method.

If the softening point is less than 40°C, the capsule will lack mechanical strength during storage, and if it exceeds 200°C, it will be difficult to break the capsule, which is not preferred. In addition, if the softening point of the thermoplastic resin is lower than the melting point of the amine curing agent, the resin will soften first during heating, and the melted interior will remain unreacted, resulting in poor adhesive properties and water resistance after curing. This is not desirable as it affects the

Specific examples of thermoplastic resins include polyvinyl butyral, polyamide resin, polysulfone resin, polycarbonate resin, cellulose acetate resin, polyvinyl chloride,
Polyethylene, hydroxypropyl methyl cellulose phthalate, ethyl cellulose, cellulose propionate, cellulose butyrate, polyvinyl formal, polymethyl methacrylate, polystyrene, polyester,
Examples include polybutadiene, polyethersulfone, phenoxy resin, ethylene-vinyl acetate copolymer, vinyl chloride-propylene-vinyl acetate copolymer, butyl methacrylate, styrene-butyl methacrylate copolymer, and the like.

Further, such a thermoplastic resin is soluble in a low boiling point solvent and can be further powdered at room temperature (for example, 20° C.). Here, the low-boiling point solvent is one that dissolves the thermoplastic resin described below, which is a wall material, and is preferably 100°C or less, preferably 40 to 8
Those having a boiling point of 0°C are used. in particular,
Examples include methylene chloride, methanol, ethanol, and acetone.

In the microcapsule type curing agent of the present invention, the wall material encapsulates the amine curing agent, and the volume ratio of the core material to the wall material is 1:0.5 to 1:10, preferably 1: 2-1:5
It is. If the wall material is too small, it may not be able to cover the core material, and if it is too large, the wall material may not break even if heated, and the core material may not flow out.

In addition, the average particle diameter is 100 μm or less, preferably 10 μm or less.
~70 μm. If the particles become coarse particles of 100 μm or more, the properties of the cured product may deteriorate.

The average particle diameter was determined by observing the sample dry using a microscope (optical microscope and electron microscope).
It was obtained by measuring the particle size distribution using the t diameter.

Such microcapsule-type curing agents are mechanically stable under normal atmospheric temperatures, for example, below 40°C, and when heated above the softening point of the thermoplastic resin, the capsules break and the curing agent contained therein is released. .

The microcapsule type curing agent of the present invention can be encapsulated by a conventional method, such as a solvent evaporation method or a spray drying method.

In the solvent evaporation method, a thermoplastic resin and an amine curing agent are first dissolved in a low boiling point solvent. In this case, the blending ratio (volume ratio) is thermoplastic resin: curing agent = 1 to 10:1, and solid content (thermoplastic resin + curing agent): solvent = 4 to 20:1.
It is preferable to set it to 00. The amount of thermoplastic resin dissolved is
It is preferable that the amount is greater than the amount of amine-based hardening agents; if it is too small, complete encapsulation may not be possible, or the capsules will be thin and mechanically unstable. On the other hand, if it is too large, the wall material becomes too thick and it becomes difficult to release the curing agent.

Also, if the solid content is low, the capsules will be fine, and if the solid content is high, the capsules will be coarse.

This solution is dispersed in the presence of an emulsifier such as sodium oleate or sodium dodecyl sulfate to form an emulsion, and then gradually heated (i.e.,
30-40°C) to evaporate the solvent. After cooling,
A microcapsule type curing agent can be obtained by drying the powder obtained by filtration and washing.

In addition, in the spray drying method, a solution consisting of a thermoplastic resin, an amine curing agent, and a low boiling point solvent is prepared in the same manner as above.
Can be encapsulated by spraying in the dryer.

The blending ratio of the solution in this case may be the same as in the case of the solvent evaporation method, but if the solid content is too large, stringing may easily occur at the spray nozzle opening. The drying temperature is usually 70 to 90°C, a two-fluid spray nozzle is used, and the air pressure is 1 to 2 kg/tyi.

〔Effect of the invention〕

The microcapsule type amine curing agent of the present invention is mechanically stable, so when used as an adhesive composition, it has excellent storage stability at room temperature (usually below 40°C), and the capsules are destroyed by heating. Hardener is released.

When such a curing agent is incorporated into a composition such as an epoxy resin, an adhesive having excellent storage stability and adhesive properties can be obtained.

〔Example〕

Example 1 Polyvinyl butyral (VI
Softening point by CAT method: 60-70℃, acetyl group: 3-5
■ol! , butyral group 70ao 1% or more, remainder hydroxyl group) 10g, dodecane methylene diamine (melting point 72'
C) 10g of methanol 18011I! , dissolved in.

The above solution 50s+1! and 500 liters of liquid paraffin (
The mixture was dispersed at a rotational speed of 2000 to 3000 rpm to form an emulsion at a rotational speed of 2000 to 3000 rpm.

After sufficient dispersion, the mixture was gradually heated (40 to 60° C.) for about 5 to 10 hours while being dispersed to volatilize methanol.

The above solution was filtered after being left to cool, and the powder obtained by washing with xylene several times was vacuum dried at room temperature to obtain a microcapsule type amine curing agent.

Example 2 Nylon (nylon 11, nylon 12 copolymer) (V
20g of m-phenylenediamine (melting point: 62°C) was mixed with methanol 200n+/
dissolved in.

Add 50 ml of the above solution to 0.5-t% sodium oleate.
, 500 ml of silicone oil (viscosity at 20°C = 1-5 centivoise) at a rotational speed of 2000-30
It was dispersed and emulsified at 00 rpm.

After sufficient dispersion, the mixture was gradually heated (40 to 50° C.) for about 5 to 10 hours while being dispersed to volatilize methanol.

Then, in the same manner as in Example 1, a microcapsule type amine curing agent was obtained.

Example 3 20 g of polyvinyl butyral used in Example 1 and 15 g of diaminodiphenylmethane (melting point 89° C.) were dissolved in 100 al of methylene chloride.

50 nl of the above solution was added to 500 mg of water at a rotation speed of 200.
The mixture was dispersed and emulsified at 0 to 3000 rpm, and then the same procedure as in Example 1 was carried out to obtain a microcapsule type amine curing agent.

Example 4 The solution prepared in Example 3 was microencapsulated by a spray drying method. The spray conditions are shown below.

Drying temperature near 0~90℃ Spray nozzle Conifluid nozzle air pressure: 1.2~1.8 kg/cj Comparative example Ethylene-vinyl acetate copolymer Softening point by CVICAT method less than 40℃, vinyl acetate 281%, average by osmotic pressure method Molecular weight 14000) 10 g, Dode, l'J
7 lOg of methyleneamine, 100ml of methylene chloride
dissolved in.

A microcapsule type amine curing agent was obtained in the same manner as in Example 1 using the above solution.

The properties and characteristics of the microcapsules obtained in the above Examples and Comparative Examples, and the storage stability and adhesive strength when used as a latent curing agent of an epoxy resin adhesive were evaluated by the following method, The results are shown in the table.

(1) Average particle size Observe the sample dry using an optical microscope, and
Particle size was measured by t diameter.

(2) 20 parts by weight of the obtained microcapsules are dispersed in 100 parts by weight of a storage-stable bisphenol A type epoxy resin (liquid at room temperature, epoxy equivalent: about 190) using a planetary mixer.

After dispersion, it was stored at 40°C, and the viscosity after 3 weeks was evaluated based on the following criteria to see how much it had increased from the initial level.

○: No change ×: The viscosity increased by 2 times or more. The viscosity was measured using a Koka type flow tester at 20°C, a load of 1 kg, and a die diameter of 1 m.

(3) Adhesive Strength 20 parts by weight of the obtained microcapsules and 4 parts by weight of aloesil were dispersed in 100 parts by weight of the same epoxy resin as above using a planetary mixer to prepare an adhesive.

In accordance with JIS-6850, two 5 pcc-sp steel plates (100 x 25 x 1.6 t m) were bonded together using the above adhesive to prepare a test piece, heated and cured at 150°C for 1 hour, and then measured at room temperature. did.

(Margin below)

Claims (2)

[Claims] (1) An amine curing agent with a melting point of 40 to 150°C is used as a core material, and a wall material enclosing the core material has a softening point of 40 to 20°C.
A microcapsule type amine curing agent characterized by being a thermoplastic resin at 0°C. (2) The microcapsule type amine curing agent according to claim 1, which is mechanically stable at room temperature, and when heated above the softening point of the thermoplastic resin, the capsules break and the curing agent is released.