Resin dispersion, coating materials, laminates, and process for production of the same

Abstract

To provide an aqueous dispersion of a resin wherein dispersed particles are stable with fine particle sizes and whereby bleeding out is suppressed, which is thus useful as e.g. a surface treating agent, an adhesive or a coating material for a polyolefin substrate.A resin dispersion having, dispersed in water with a 50% particle diameter of at most 0.5 μm, a polymer (C) having a hydrophilic polymer (B) or an acidic group bonded to a propylene / α-olefin copolymer (A) as a copolymer of propylene with an α-olefin other than propylene, wherein the copolymer (A) has a propylene content of at least 50 mol % and less than 100 mol %, and the copolymer (A) has a weight average molecular weight Mw of at least 10,000 and a molecular weight distribution Mw / Mn of at most 3.5; and the resin dispersion has a surfactant content of at most 15 parts by weight per 100 parts by weight of the polymer (C); and a coating material or laminate, made by using such a dispersion.

Description

TECHNICAL FIELD[0001]The present invention relates to an aqueous resin dispersion containing a propylene polymer, a coating material containing it, and a laminate; and processes for their production.BACKGROUND ART[0002]Polyolefins such as propylene polymers or propylene-α-olefin copolymers are inexpensive and yet excellent in mechanical properties, heat resistance, chemical resistance, water resistance, etc., and thus, they are used in various fields. However, such polyolefins have no polar groups in their molecules and thus are usually of low polarity and difficult to bond or apply for coating, and their improvements have been desired. Accordingly, various methods have been tried such as a method for chemical treatment of the surface of a polyolefin molded product with a reagent or the like, or a method for oxidation treatment of the surface of a molded product by such a means as corona discharge treatment, plasma treatment or flame treatment. However, such methods not only require...

AI Technical Summary

Benefits of technology

[0043]According to the present invention, the polymer (C) is excellent in dispersibility in water and thus has merits such that the dispersed particle sizes are fine, the particle size distribution can be made narrow, and it can be dispersed stably. Further, it can be dispersed by adding substantially no or a very small amount of a surfactant, and thus, there is a merit such that it is possible to suppress bleeding out of the surfactant which used to be problematic, and it is possible to obtain a coated product having an excellent appearance. Accordingly, the aqueous dispersion can be used also for an application where an organic solvent solution has been used for coating, such being advantageous also from the viewpoint of the safety and hygiene. Further, it is not an organic solvent solution, and it is thereby possible to reduce the discharge of VOC (volatile organic chemical substances), such being advantageous also from the environmental aspect. Yet, it is possible to obtain an aqueous dispersion having excellent characteristics containing substantially no chlorine. In a case where no chlorine is contained, there is no problem such as dioxin, toxicity or the like, such being very advantageous from the environmental viewpoint.

[0044]Further, as compared with a propylene homopolymer having a stereoregularity of the same level, the propylene / α-olefin copolymer (A) has high solubility in a solvent, is excellent in dispersibility in water and has a low melting point, whereby there is a merit such that the resin dispersion employing it is capable of lowering the baking temperature after coating.

[0045]Further, according to the process for producing the resin dispersion of the present invention, it is possible to easily obtain an excellent aqueous resin dispersion wherein the dispersed particle sizes are fine, the particle size distribution is narrow, and the resin particles are stably dispersed.

[0046]Further, the coating film obtained by applying a coating material containing the resin dispersion of the present invention is excellent in the water resistance, moisture resistance, oil resistance (gasohol resistance) and chemical resistance. Therefore, it is suitable for use in a coating method of finishing by coating only once, e.g. using a solvent lacquer coating material.

[0047]And, the obtained coating film exhibits good adhesion to a polyolefin base material or a plastic base material containing e.g. a polyolefin and can be formed also on a hardly adhesive substrate such as an untreated polypropylene to which adhesion or coating is usually difficult.

[0048]Further, when the polymer (C) in the resin dispersion of the present invention is used in combination with another resin to form a composite resin dispersion, it is possible to improve the physical property values derived from such another resin, specifically to improve the strength, water resistance, weather resistance, abrasion resistance, solvent resistance, etc. of the coating film.

Problems solved by technology

However, such polyolefins have no polar groups in their molecules and thus are usually of low polarity and difficult to bond or apply for coating, and their improvements have been desired.

However, such methods not only require special apparatus but also the effects for improving the coating property or the adhesive property have not been necessarily adequate.

However, such a resin dispersion has had a problem that in order to make dispersed particle sizes to be fine, it is required to add a large amount of a surfactant, and consequently, a coating material employing such a resin dispersion is poor in water resistance or chemical resistance.

On the other hand, if the amount of the surfactant is reduced, the particle sizes of dispersed resin tend to be large, and there has been a problem in storage stability.

However, the dispersed particle sizes of the ethylene copolymer or polypropylene homopolymer can not be said to be sufficiently fine, and it is not possible to form the dispersion without using a surfactant at all.

However, the molecular weight of the raw material to be used is very low at a level of 6,500, whereby the aqueous dispersion is inferior in the adhesion to the polyolefin substrate, water resistance and chemical resistance.

However, it is still essential to use a surfactant, the stability is poor with large particle sizes, and there still remain such a problem as bleeding out due to the surfactant or poor chemical resistance.

However, it is still essential to use a surfactant, and there still remains such a problem as bleeding out.