JPH0465405A - Production of improved acrylic elastic fine particle - Google Patents

Abstract

PURPOSE:To obtain the subject fine particles having rubber-like elasticity, excellent in strength and useful as a matting agent, etc., by dispersing a composition composed of a lower alkyl acrylate and a polyfunctional urethane (meth)acrylate monomer in a specified ratio in an aqueous solvent and polymerizing the resultant mixture under rapid stirring. CONSTITUTION:A monomer composition composed of (A) 50-99 wt. lower alkyl acrylate (e.g. methyl acrylate) and (B) 1-50 wt.%, preferably 5-30 wt.% polyfunctional urethane (meth)acrylate monomer (e.g. compound of formula) is dispersed in an aueous solvent and the resultant dispersion is subject to a polymerization condition under rapid stirring, thus obtaining the objective fine particles.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing improved acrylic elastic fine particles, and more specifically, to a method for producing improved acrylic elastic fine particles, and more particularly, to a method for producing improved acrylic elastic fine particles, and more specifically, for producing rubber-like elastic particles useful for matting agents, plastic modifiers, etc. This invention relates to a method for producing acrylic elastic fine particles which have the same properties and have excellent strength.

[Conventional technology]

In recent years, matte paints have been widely used that are made by blending particles such as fine polymer particles into the paint to eliminate the gloss on the painted surface.In particular, matte paints that contain fine particles of elastic polymers in the flexible base paint have been widely used. Matte paints with

[Invention or problem to be solved]

Urethane particles are commonly used as elastic polymer particles, but the production method is special and difficult, making them expensive and difficult to use in general-purpose fields.

In view of the above circumstances, the inventors of the present invention first proposed acrylic elastic fine particles having rubber-like elasticity, or the fine particles did not have sufficient strength, which caused the problem that the coating film was easily damaged.

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 that have excellent strength and are suitable as a matting agent for paints and a modifier for plastics.

[Means to solve the problem]

In order to achieve the above object, the present inventor has conducted various studies and found that by using polyfunctional urethane (meth)acrylate as a crosslinking agent, the present inventor has sufficient rubber elasticity and shape retention as a fissure. The present inventors have discovered that microspherical particles with excellent strength can be obtained, and have completed the present invention.

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

[For production]

The structure and operation of the present invention will be explained.

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 j-butyl acrylate.

All of these are commercially available and easily available. Among these, those with a small number of carbon atoms are preferred from the standpoint of toughness, and those with a large number of carbon atoms are preferred from the standpoint of flexibility, and are selected depending on the purpose. Moreover, two or more of these can also be used in combination.

The polyfunctional urethane (meth)acrylate monomer used in the method of the present invention includes a urethane moiety and two or more (meth)acrylate monomers.
Any material may be used as long as it has an acrylate moiety and functions as a crosslinking agent during polymerization.For example, those having the structural formulas shown in (A) to (G) below may be used. Not limited.

In addition, in order to adjust the swelling properties of the particles with solvents and the flexibility of the particles, a small amount of a general polyfunctional vinyl crosslinking agent such as divinylbenzene or ethylene glycol dimethacrylate may be used in combination.

(Margin below this page) CH2=C-COOCH2CH-CH20CO-C=C
H2(E) (C)12).

H CH2=C-C00C)12C1(-CI(20CO-
C) l=cH.

(F) (CH2)6 H (D) (cls H CH2=C-C00C)12C1(-CH20CO:l
-C=CH2(G) NH (CH2)=NH In the method of the present invention, the monomer composition contains 50 to 99% by weight of the above lower alkyl acrylate and polyfunctional urethane (
Primarily prepared from 1-50% by weight of meth)acrylate monomers. In this preparation, if the amount of polyfunctional urethane (meth)acrylate monomer is less than 1% by weight, the particle shape cannot be maintained and a sufficient matting effect cannot be obtained. Also 5
If it is more than 0% by weight, flexibility is poor and a soft feel cannot be obtained. It is preferably used in an amount of 5 to 30% by weight. During the above preparation, any polymerization initiator known in the art may be 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, the aqueous system includes a dispersant known in the art,
Surfactants and the like may optionally be used. Examples of the dispersant include polyvinyl alcohol, tertiary calcium phosphate, and metathesized magnesium pyrophosphate, and examples of the surfactant include sodium alkyl sulfate.

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

The high-speed stirring to achieve dispersion during the above 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 to 3 μm.
It is preferable to adjust it to a range of 2 to 0.3 n+/m. If the above-mentioned stirring speed is defined by the peripheral speed of the blade tip, it can be preferably about 0.5 to 5 m/s. Fine particles are generated by the above polymerization.

The fine particles obtained by the above polymerization are washed with water and
After solid-liquid separation, it is subjected to drying. If the resulting fine particles agglomerate, they can be easily returned to primary particles by dispersing them in an organic solvent such as lacquer thinner or B, T, or X.

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

〔Example〕

It is not intended that the invention be limited or described in detail with respect to the embodiments of the invention.

Example stainless steel 5I! In an autoclave, 250 g of tertiary calcium phosphate, 2500 g of water containing 0.05 g of sodium lauryl sulfate, 450 g of ethyl acrylate containing 2.2°-azobisisobutyronitrile (Ig), and a polyfunctional urethane acrylate belonging to structural formula (A) were placed in an autoclave. (Toagosei Chemical Industry Co., Ltd. Aronix M-1200) A monomer composition was prepared by mixing 50 g, and after replacing the space with nitrogen, the mixture was heated at 65°C for 5 minutes under high-speed stirring at a circumferential speed of 2.1 rn/s.
Polymerization was then carried out at 80°C for 5 hours. The obtained polymer particles had an average particle diameter of about 40 μm, and after drying, they aggregated into a lump having rubber-like elasticity.

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

In addition, 50 g of the above-mentioned dried particles, 100 g of a solution type thermoplastic polyurethane resin (2-component type, Takerac E550, manufactured by Takeda Pharmaceutical Company Ltd.), and a curing agent (Takenate E-40)
, Takeda Pharmaceutical Co., Ltd. 250g, 2-butanone for dilution 100
A paint was prepared by mixing g. When this paint was applied to a metal plate and cured by baking at 80°C for 30 minutes, a matte coating film with a soft feel was obtained. When this paint film was scratched with a fingernail, the traces were hardly noticeable, and after being left for 24 hours, the traces became even more noticeable, perhaps due to recovery due to elasticity, etc.

Comparative Example The monomer composition in Example was ethyl acrylate) 4
Polymerization, paint preparation, and coating test were carried out in the same manner, except that 50 g of ethylene glycol dimethacrylate was used.

The resulting coating was a matte coating with a soft feel, but
Scratching with fingernails left clear marks, and even after being left for 24 hours, there was almost no recovery due to elasticity, etc.

〔Effect of the invention〕

Since the present invention is configured as described above, the resulting improved acrylic elastic fine particles can be made flexible by crosslinking and polymerizing lower alkyl acrylate with a polyfunctional urethane (meth)acrylate monomer. It is possible to provide fine particles that have rubber-like elasticity by making use of properties such as elasticity and toughness while ensuring shape retention as particles, and have excellent strength. Compared to conventional acrylic elastic fine particles, friction etc. It does not leave any traces easily and can be highly marketable, so it can be expected to be used in a wide range of fields and is extremely useful industrially.

Applicant: Sekisui Plastics Co., Ltd. Agent Patent Attorney Yusuke Hiraki Same patent attorney Sadaji Ishii

Claims (1)

[Claims] A monomer composition consisting of 50 to 99% by weight of lower alkyl acrylate and 1 to 50% by weight of polyfunctional urethane (meth)acrylate monomer is dispersed in an aqueous system, and the monomer is subjected to polymerization conditions under high-speed stirring to obtain rubber-like elasticity. 1. An improved method for producing acrylic elastic fine particles characterized by obtaining fine particles having the same properties and excellent strength.