JPH0689087B2 - Method for producing urethane-acrylic elastic fine particles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a method for producing urethane-acrylic elastic fine particles. More specifically, the present invention relates to a method for producing urethane-acrylic elastic fine particles that have affinity for urethane resins and are useful as erasers and plastic modifiers.

(B) Conventional technology and its problems In recent years, paints containing fillers such as polymer fine particles to erase the marks on the coated surface are widely used. Especially, urethane-based flexible paints have elasticity. A vanishing paint with a velvet-like or suede-like feel containing urethane fine particles is drawing attention. The above-mentioned elastic urethane fine particles used for this can be obtained by pulverization or synthesis under suspension in a liquid phase. Fine pulverization is difficult. In addition, even in the synthesis in a liquid phase suspension, the manufacturing conditions such as poor dispersion stability at the time of synthesis and difficulty in removing the dispersion stabilizer are difficult and expensive, so that the application is limited to fields with high added value. I will end up.

In view of the above circumstances, the inventor of the present invention, as a result of earnest research to further improve the compatibility with urethane resin based on the previously proposed acrylic elastic fine particles having rubber-like elasticity, has been identified. The present inventors have found that microparticles having rubber-like elasticity with excellent affinity for urethane resin can be produced from a monomer composition containing the acrylate mixture as a main component, and completed the present invention.

(C) Means and Actions for Solving the Problems Thus, according to the present invention, polyglycol mono (meth) acrylate, polyfunctional urethane (meth) acrylate, and vinyl-based copolymerizable with them, which are added as necessary. It is characterized in that a monomer composition comprising a monomer is dispersed in an aqueous system, and the composition is subjected to polymerization conditions under high-speed stirring to obtain fine particles having affinity with a urethane resin and having rubber-like elasticity. A method for producing urethane-acrylic elastic fine particles is provided.

As the polyglycol mono (meth) acrylate used in the method of the present invention, a polyglycol mono (meth) acrylate having a hydroxyl group at the terminal and having a sufficient degree of polymerization so as to impart sufficient elasticity to the final product is selected. Examples of such a material include polyethylene glycol (meth) acrylate, polypropylene glycol mono (meth) acrylate, polyethylene glycol polypropylene glycol mono (meth) acrylate, polyethylene glycol polytetramethylene glycol mono (meth) acrylate, and the like.
The degree of polymerization of these polyglycol chains is preferably 5 or more. These polyglycol mono (meth) acrylates can be used in combination of two or more kinds.

The polyfunctional urethane (meth) acrylate used in the method of the present invention may be any one as long as it can function as a cross-linking agent during polymerization and can impart an affinity with the urethane resin to the final product. Examples thereof include, but are not limited to, those having the structural formulas shown below.

In the method of the present invention, a monomer composition is prepared by using the polyglycol mono (meth) acrylate and the polyfunctional urethane (meth) acrylate as main components.
In this preparation, a small amount of a monofunctional or polyfunctional vinyl-based monomer copolymerizable with these may be used in order to further adjust the flexibility and to supplement the crosslinking effect of the polyfunctional urethane (meth) acrylate. In the preparation of the monomer composition, the polyglycol mono (meth) acrylate is preferably used in an amount of 30% by weight or more, more preferably 50% by weight or more, from the viewpoint of rubber-like elasticity of the final product. preferable. On the other hand, polyfunctional urethane (meth) acrylate is 1 to 25 in terms of affinity with the final product urethane resin and function as a cross-linking agent during polymerization.
It is preferably used in weight percent. That is, when the content is 1% by weight or less, the particle shape cannot be maintained and a sufficient effect of erasing the particles cannot be seen. On the other hand, if it is more than 25% by weight, the flexibility of the particles is poor and a soft feeling cannot be obtained. Furthermore 3 to 15% by weight
More preferably, it is used in a ratio of. In addition, a polymerization initiator known in the art is optionally used in the monomer composition. Examples of the polymerization initiator include organic peroxides such as benzoyl peroxide and azo initiators such as 2,2'-azobisisobutyronitrile.

In the present invention, the monomer composition prepared as described above is dispersed in an aqueous system and subjected to aqueous suspension polymerization under high speed stirring. At this time, in the water system, a dispersant known in the art,
A surfactant or the like may be optionally used in combination. Examples of the dispersant include polyvinyl alcohol, tricalcium phosphate, metathesis method magnesium pyrophosphate, and the like, and examples of the surfactant include sodium alkyl sulfate.

The above-mentioned polymerization is carried out by dispersing water containing a dispersant and a monomer composition containing a polymerization initiator under high-speed stirring into fine droplets and subjecting them to polymerization conditions. Examples of the polymerization conditions include heating the dispersed water system at 40 to 100 ° C. for 1 to 10 hours.

The high-speed stirring for achieving dispersion during the polymerization depends on the volume and shape of the reaction system, so the stirring speed cannot be limited,
The average particle size of the finally obtained fine particles is from 2 to 2 μm.
It is preferably adjusted to be in the range of 2 to 0.3 m / m. If the stirring speed is defined by the peripheral speed of the blade tip, 0.5 to 5 m / s can be cited as a preferable value. Fine particles are generated by the above-mentioned polymerization.

The fine particles obtained by the above polymerization are washed with water according to a conventional method,
After solid-liquid separation, it is dried. When the fine particles obtained at this time agglomerate, they can be easily returned to the primary particles by dispersing them in an organic solvent such as alcohol, ester or ketone.

By the above treatment, elastic fine particles having excellent affinity with the urethane resin and having rubber-like elasticity can be obtained.

(D) Action According to the present invention, the polyglycol mono (meth) acrylate polymerization component of the obtained polymer has a large plasticity, thereby mainly imparting rubber-like elasticity, and at the same time, the polyglycol part and urethane of the same polymer. It is presumed that the part has a structure similar to that of the urethane resin, and as a result, affinity with the urethane resin is considered to occur. Furthermore, it is presumed that a part of the hydroxyl groups at the polyglycol end reacts with the isocyanate in the urethane-based paint to increase the strength between the urethane coating particles.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited thereto.

(E) Example 1 In a stainless steel 5 autoclave, polypropylene glycol monomethacrylate (500 g of metathesis method magnesium pyrophosphate 50 g, water containing 3.5 g of sodium lauryl sulfate 2500 g, polypropylene glycol monomethacrylate containing 1 g of 2,2'-azobisisobutyronitrile ( n: 5
6) A monomer composition comprising 450 g and 50 g of a polyfunctional acrylic urethane acrylate represented by the following structural formula (G) was prepared, the space was replaced with nitrogen, and then a high speed stirring at a peripheral speed of 2.8 m / s was performed. Polymerization was carried out at 5 ° C for 5 hours and then at 100 ° C for 3 hours. The obtained fine particles had an average particle size of about 35 μm, and after drying, they were aggregated into a mass having rubber-like elasticity. It was confirmed that when a part of the agglomerates here was immersed in isopropanol, it returned to the primary particles with slight stirring.

Further, a coating material was prepared by mixing 50 g of the above-mentioned fine particles after drying and 200 g of a solution type thermoplastic polyurethane resin [one-pack type, Takelac E-365, Takeda Pharmaceutical Co., Ltd.]. When this paint was applied to a metal plate and baked and cured at 150 ° C. for 30 minutes, a matte coating film having a soft feeling was obtained. Furthermore, even when this coating film was repeatedly bent, whitening, cracks, and separation of fine particles did not occur.

Example 2 The monomer composition of Example 1 was prepared by adding 100 g of polypropylene glycol monomethacrylate (n = 12), 300 g of polyethylene glycol monomethacrylate (n = 7-9),
Polyfunctional acrylic urethane represented by the following structural formula (D) 10
Same polymerization except changing to 0g, average particle size about 30μ
m fine particles were obtained.

50 g of the above-mentioned fine particles after drying, 100 g of solution type thermoplastic polyurethane resin (two-pack type, Takelac E-550 Takeda Chemical Industries, Ltd.), curing agent (Takenate E-40 Takeda Pharmaceutical Co., Ltd.) 25 g, A paint was prepared by mixing 100 g of 2-butanone for dilution, and the paint was applied to a metal plate and baked and cured at 80 ° C. for 30 minutes to obtain a matte paint film having a soft feeling. This coating film was free from whitening, cracking, and particle peeling even after repeated bending.

(F) Effect of the Invention According to the method of the present invention, urethane-acrylic fine particles having a rubber-like elasticity excellent in affinity with a urethane resin can be produced by a relatively simple and inexpensive method. Further, it is possible to provide elastic fine particles useful for a wide range of applications such as a matting agent and a plastic modifier.

Claims (1)

[Claims] 1. A monomer composition comprising a polyglycol mono (meth) acrylate, a polyfunctional urethane (meth) acrylate, and a vinyl monomer copolymerizable with them, which is added as necessary, is dispersed in an aqueous system, A method for producing urethane-acrylic elastic fine particles, which comprises subjecting the composition to polymerization conditions under high-speed stirring to obtain fine particles having affinity with a urethane resin and rubber-like elasticity.