Acrylic polymer fine particles and plastisol using the same

Abstract

Acrylic polymer fine particles which comprise primary particles P of 250 nm or more in average particle diameter having a core shell structure and plastisols prepared using the same. In the fine particles, a core polymer C and a shell polymer S are copolymers of the following monomer mixtures Mc and Ms, respectively, and the weight ratio of Mc and Ms is 10/90-90/10: Mc: methyl methacrylate 20-85 mol % (meth)acrylic ester of C2-C8 aliphatic alcohol and/or aromatic alcohol 15-80 mol % other copolymerizable monomers not more than 30 mol %; , when the total amount of these monomers is 100 mol %; Ms: methyl methacrylate 20-79.5 mol % (meth)acrylic ester of C2-C8 aliphatic alcohol and/or aromatic alcohol 5-40 mol % a monomer containing carboxyl group or sulfonic acid group 0.5-10 mol % other copolymerizable monomers not more than 30 mol %.

Description

[0001] This application is a continuation-in-part of PCT / JP99 / 03468 filed on Jun. 29, 1999. Japanese Patent Application No. 10-199473 filed on Jul. 01, 1998, from which this application has the benefit of the priority date, is herein incorporated by reference.[0002] The present invention relates to acrylic fine particles having a core-shell structure. Particularly, it relates to a plastisol comprising acrylic polymer fine particles dispersed in a plasticizer. More particularly, it relates to a plastisol which is excellent in storage stability and in retention of plasticizer after film formation by heating.[0003] Plastisols comprising polymer fine particles dispersed in plasticizers as media are utilized in a wide variety of industrial fields and have very high industrial values. Especially, plastisols prepared using vinyl chloride polymer fine particles are known as vinyl chloride sols and are used in various fields such as wall papers, undercoats for automobiles, body sealers for a...

AI Technical Summary

Benefits of technology

0018] The object of the present invention is to provide at an industrially practical level a novel plastisol which contains no vinyl chloride polymer and is satisfactory in storage stability and retainability of plasticizers.

Problems solved by technology

However, as for products made using vinyl chloride sols, there has been the problem that when they are incinerated, hydrogen chloride gas is generated to seriously damage incinerators.

Moreover, recently, there are problems of acid rain and, furthermore, adverse effects on human bodies and earth environment of the highly toxic dioxin generated upon incineration.

However, for the production of these materials, the existing productive facilities for vinyl chloride sols cannot be utilized, and, thus, an enormous facility investment is required for industrial utilization of these materials.

Moreover, one-pack type urethane materials have many problems such as insufficient storage stability due to increase of viscosity, toxicity and high cost.

The epoxy materials also have problems of high cost and considerably inferior properties to vinyl chloride sols.

Problems of the aqueous emulsions are that they cannot be used for thick coating, blisters that occur in the coating films with evaporation of water, and poor water resistance of the coating films.

The silicone materials are also high in cost and cannot be a substitute material for vinyl chloride sols from the points of their properties.

Therefore, it is considerably difficult to substitute these materials for vinyl chloride sols.

However, these plastisols containing essentially a vinyl chloride polymer still produce toxic gases upon incineration like the conventional vinyl chloride sols.

Therefore, the above-mentioned environmental problems have not yet been solved.

The polymer used in this patent publication comprises particles of uniform structure, and in the case of the acrylic polymer, storage stability of plastisol and plasticizer retainability of the coating film cannot be realized with particles of uniform structure, and, hence, the storage stability of or properties of the coating film formed from the plastisol proposed in the above patent publication tend to be extremely deteriorated.

This is because unlike vinyl chloride polymers, acrylic polymers only have weak van der Waals cohesive force between molecules, and, hence, when a composition high in compatibility with plasticizer is used, the plasticizer readily penetrates between the molecules to cause plasticization, namely, gelation, which lead to deteriorated storage stability.

However, a polymer low in compatibility with plasticizer has good storage stability, nevertheless, the coating film obtained by application and heating of the sol (hereinafter referred to as "gelling film") has considerably low retainability of plasticizer resulting in bleed out of plasticizer from the gelling film with lapse of time.

As explained above, in the case of an acrylic sol prepared using acrylic polymer fine particles, the storage stability and the plasticizer retainability are contrary to each other and polymer particles of uniform structure cannot retain both of them.

However, since the polymer proposed in the patent publication is low in compatibility with plasticizer, and, especially, copolymerization ratio of methyl methacrylate in the shell portion is high, its plasticizing state becomes inferior and it fails to form good coating films when a plasticizer with low polarity such as a phthalic ester plasticizer is used.

Accordingly, the effect of improving storage stability, which is expected as a role of the shell portion, is very low.

Furthermore, the shell portion introduced by the alkali hydrolysis has much increased acid value and very low compatibility with the plasticizer to cause considerable deterioration of film-formability.

Moreover, since such shell portion with high acid value contributes for polymer particles in the plastisol to form structural viscosity, there is the problem of deterioration in operability due to an increased viscosity of the plastisol.

The shell having very low compatibility is advantageous for storage stability, nevertheless, has the tendency of becoming inferior in various performances such as film-formability of sol, and strength, elongation, transparency, adhesion to substrate, sound insulation and vibration-damping properties of the resulting coating film.

Especially, since the plastisol is inferior in retention of plasticizers, it tend to cause bleed out of the plasticizers and thus not practical.

However, since extremely excellent properties of a polymer are demanded for putting it to practical use, the polymers proposed in the above patent publications, in this respect, are not optimized in balancing of compatibility with plasticizers and are at low levels in both the storage stability and the plasticizer retainability and, therefore, unsuitable for industrial practical use.