JPH0757782B2 - Method for producing improved acrylic elastic fine particles - Google Patents

Description

TECHNICAL FIELD The present invention relates to an improved method for producing acrylic elastic fine particles, and more specifically, to a rubber-like elasticity useful for matting agents, plastic modifiers and the like. The present invention relates to a method for producing acrylic elastic fine particles having excellent strength.

[Conventional technology]

In recent years, matting paints have been widely used in which paints such as polymer particles are blended to deluster the coated surface. Particularly, soft touch feeling is achieved by blending elastic polymer particles into a flexible base coating material. Matte paints that have a lot of attention are attracting attention.

[Problems to be Solved by the Invention]

As the elastic polymer fine particles, urethane fine particles are generally used, but they are expensive and difficult to use in a general-purpose field because they are special and difficult to produce. In view of the above circumstances, the present inventor has previously proposed acrylic elastic fine particles having rubber-like elasticity, but has a problem that the coating film is easily damaged because the strength of the fine particles is not sufficient.

It is an object of the present invention to solve these problems of the prior art and to provide a method for producing acrylic elastic fine particles, which has excellent strength and is suitable as a matting agent for paints and a plastic modifier.

[Means for Solving the Problems]

In order to achieve the above-mentioned object, the present inventor has conducted various studies, and by using a polyfunctional urethane (meth) acrylate as a crosslinking agent, has sufficient rubber elasticity and shape retention as a filler, Moreover, they have found that fine spherical particles having excellent strength can be obtained, and completed the present invention.

That is, the present invention is a lower alkyl acrylate 50-99
% By weight, polyfunctional urethane (meth) acrylate monomer 1
-50% by weight of a monomer composition dispersed in an aqueous system, under high-speed stirring, subjecting the monomer to polymerization conditions, rubber-like elasticity, and an improved characteristic characterized by obtaining excellent strength The gist is a method for producing acrylic elastic fine particles.

[Work]

 The configuration and operation of the present invention will be described.

The lower alkyl acrylate used in the method of the present invention is
It means acrylic acid esterified with an alkyl group having 1 to 4 carbon atoms, and examples thereof include methyl acrylate, ethyl acrylate, n-butyl acrylate, and i-butyl acrylate. All of these are generally commercially available and easily available. Among these, those having a small carbon number are preferable from the viewpoint of toughness, and those having a large carbon number are preferable from the viewpoint of flexibility, and they are selected according to the purpose. Moreover, these can also be used in combination of 2 or more types.

The polyfunctional urethane (meth) acrylate monomer used in the method of the present invention may be any as long as it has a urethane moiety and two or more (meth) acrylate moieties and functions as a crosslinking agent during polymerization. . For example, those having the structural formulas shown in (A) to (G) below can be mentioned, but the invention is not limited thereto.

Further, in order to adjust the swelling property of the particles with a solvent and the flexibility of the particles, a small amount of a general polyfunctional vinyl-based crosslinking agent such as divinylbenzene or ethylene glycol dimethacrylate may be used in combination.

_{(A) CH 2 = CHCOO-} R'-OOCNHR-NHCOO- ( _{polyol) -OOCNH n R-NHCOO-R'OCOCH} = CH 2 In the method of the present invention, the monomer composition is mainly prepared from 50 to 99% by weight of the lower alkyl acrylate and 1 to 50% by weight of the multifunctional urethane (meth) acrylate monomer. In this preparation, when the amount of the polyfunctional urethane (meth) acrylate monomer is 1% by weight or less, the particle shape cannot be maintained and a sufficient matting effect cannot be obtained. On the other hand, when it is 50% by weight or more, the softness is poor and a soft feeling cannot be obtained. It is preferably used in an amount of 5 to 30% by weight. In the above preparation, a polymerization initiator known in the art is optionally used. Examples of the polymerization initiator include organic peroxides such as benzoyl peroxide and azo initiators such as 2,2'-azobisisobutyronitrile.

In the method of the present invention, the monomer composition prepared as described above is dispersed in an aqueous system under high speed stirring and subjected to aqueous suspension polymerization. At this time, in the water system, a dispersant known in the art,
A surfactant or the like may be optionally used. 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 into fine monomer droplets under high-speed stirring and subjecting them to polymerization conditions. Examples of the polymerization conditions include heating the 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 2-3 μm to 0.2
It is preferably adjusted to be in the range of 0.3 m / m. If the stirring speed is defined by the peripheral speed of the blade tip, about 0.5 to 5 m / s can be mentioned as a preferable one. 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. If 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 lacquer thinner BTX.

By the above treatment, acrylic fine elastic particles having rubber-like elasticity and excellent strength can be obtained.

〔Example〕

Examples of the present invention will be described in detail, but the present invention is not limited thereto.

Example 2500 g of water containing 250 g of tricalcium phosphate and 0.05 g of sodium lauryl sulfate in a stainless steel 5 autoclave,
Monomer composition in which 450 g of ethyl acrylate containing 1 g of 2,2′-azobisisobutyronitrile and 50 g of polyfunctional urethane acrylate belonging to structural formula (A) (Aronix M-1200, Toagosei Kagaku Kogyo Co., Ltd.) are mixed. Was prepared, and the space was replaced with nitrogen, then at 65 ° C under high-speed stirring with a peripheral speed of 2.1 m / s.
Polymerization was carried out for 5 hours and then at 80 ° C. for 5 hours. The obtained polymer particles had an average particle diameter of about 40 μm and after drying were agglomerated into a mass having rubber-like elasticity.

It was confirmed that when a part of this agglomerate was immersed in 2-butanone, it was dispersed with slight stirring and returned to primary particles.

Further, 50 g of the fine particles of the dried product, 100 g of a solution type thermoplastic polyurethane resin (two-pack type, Takelac E-550, manufactured by Takeda Pharmaceutical Co., Ltd.), a curing agent (Takenate E-40, 250 g manufactured by Takeda Pharmaceutical Co., Ltd.) A coating material was prepared by mixing 100 g of 2-butanone for dilution.
When baked and cured for 30 minutes, a matte coating film having a soft feeling was obtained. When the coating film was scratched with a nail, the traces were hardly noticeable, and when left for 24 hours, the traces were less noticeable because of recovery due to elasticity or the like.

Comparative Example The monomer composition in Example was treated with ethyl acrylate 450.
g, the same polymerization, coating material adjustment and coating test were conducted except that ethylene glycol dimethacrylate was changed to 50 g.

The coating film obtained was a matte coating film with a soft feeling,
The scratches were clearly left by scratching with nails, and recovery by elasticity etc. was hardly seen even after standing for 24 hours.

〔The invention's effect〕

Since the present invention is configured as described above, the improved acrylic elastic fine particles obtained are obtained by subjecting a lower alkyl acrylate to a cross-linking / polymerization treatment with a polyfunctional urethane (meth) acrylate monomer to give a softening property by the acrylate. It is possible to provide fine particles that have rubber-like elasticity and excellent strength while ensuring shape retention as particles while making use of properties such as toughness and toughness, and to provide friction and the like in comparison with conventional acrylic elastic fine particles. The traces due to are hardly left, and high commercial property can be imparted, and it can be expected to be used in a wide range of fields, and is extremely useful in industry.

Claims (1)

[Claims] 1. Lower alkyl acrylate 50 to 99% by weight,
A monomer composition consisting of 1 to 50% by weight of a polyfunctional urethane (meth) acrylate monomer is dispersed in an aqueous system and stirred under high speed.
An improved method for producing acrylic elastic fine particles, characterized in that fine particles having rubber-like elasticity and excellent strength are obtained by subjecting the monomer to polymerization conditions.