Emulsion and production process therefor

Details Emulsion and production process therefor Emulsion and production process therefor

1999-03-09

2001-07-10

Cain, Edward J. (Department: 1714)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

At least one aryl ring which is part of a fused or bridged...

C524S535000, C524S832000

Reexamination Certificate

active

06258889

ABSTRACT:

TECHNICAL FIELD
The present invention relates to an improvement for an emulsion used for coating a surface of plastic materials such as polyolefin and a production process therefor.
BACKGROUND ART
Plastic materials used for automobile bumpers, molds and so on, generally, have bad wetting for coating compositions such as paint compositions and primer compositions and are inferior for coating. Especially, as polyolefin resins such as a polypropylene resin do not have polar groups in molecules and are chemically inactive, the plastic materials of polyolefin resin materials are much inferior for coating and adhesion to coating compositions.
Since the coating compositions in which the medium is an organic solvent have problems in flammability and since their solvents have high VOC ratios coating compositions made of an emulsion with an aqueous medium have been developed. However, this emulsion is low in coating and adhesion performance in comparison with the coating compositions in which the medium is an organic solvent.
To solve the problem of coating with the emulsion, JP-A-05-214188 discloses raising polarity by chlorinating polyolefin which is the main material of the coating compositions. However, as polyolefin chloride has low cohesion, its adhesion is insufficient. Then, JP-A-03-182534 discloses to improve adhesion by grafting polyolefin chloride with unsaturated polycarboxylic acid and/or acid anhydride. However, grafting with unsaturated polycarboxylic acid and/or acid anhydride which have high water-solubility, produces another problem of lowering the water-resistance of films.
Polyolefin chloride has high hydrophobicity and it is therefore difficult to disperse in water stably. JP-A-06-080738 discloses a technique to polymerize a reactive emulsifier made of acrylic resin based polymer, and when needed, other reactive monomers in a water medium under the existence of polyolefin and to improve water dispersion stability of polyolefin. This technique is to improve water dispersion stability of the emulsion by covering a polyolefin with an emulsifier by means of using the reactivity of an acrylic resin based polymer. However, an acrylic resin based polymer which has high hydrophilicity and polyolefin which has low polarity are incompatible. Therefore, an emulsion composition stabilized by an acrylic resin based polymer emulsifier has two problems. The first is stability with the passage of time (storage stability) of the water dispersion, and the second is that a coated film obtained from this is muddy. It is therefore required to improve the water dispersion of polyolefin chloride by another means.
As for polyolefin chloride, since the levels of coated film strength and weather resistance are low, there are cases where it is necessary to improve coated film strength and weather resistance by using polyolefin chloride together with an acrylic resin or other resin. In this case, it is difficult to use these together because polyolefin chloride and an acrylic resin or other resin are incompatible. Then, JP-A-05-209006 suggests choosing an acrylic resin which has comparatively good compatibility and grafting polyolefin chloride with this acrylic resin. This technique has the desired effects of using polyolefin chloride and acrylic resin together by grafting the acrylic resin and, further, maintains compatibility between polyolefin chloride and the acrylic resin or other resin using the compatibility improving effect of a grafted acrylic resin. However, in the grafting of an acrylic resin to polyolefin chloride, as there is a quantitative limit to compatibility, it becomes impossible to increase the amount of an acrylic resin and, further, there are not so many kinds of (meth) acryl based oligomers which have good compatibility with polyolefin chloride.
DISCLOSURE OF THE INVENTION
Objects of the Invention
An object of the present invention is to provide an emulsion and production process therefor, where the emulsion sufficiently coats and adheres to polyolefin materials, is highly water dispersible, has good storage stability and has excellent compatibility with an acrylic resin and other resins.
SUMMARY OF THE INVENTION
An emulsion according to the present invention comprises:
a styrene-acryl-acid grafted polyolefin chloride, which includes a polyolefin chloride structure moiety (
1
), an acid anhydride and/or carboxylic acid structure moiety (
2
) bonded to the moiety (
1
) and a styrene-acryl based polymerization chain moiety (
3
) bonded to the moiety (
2
) and wherein some of the acid anhydride groups and/or carboxylic acid groups remain, wherein a ratio of the moiety (
2
) to a sum of the moiety (
1
) and the moiety (
2
) is 1-10 weight %;
an emulsifier;
a basic substance that includes at least one of an amine compound and ammonia; and water.
It is preferable that a ratio of a sum of the moiety (
1
) and the moiety (
2
) to the moiety (
3
) is 10-200 weight %.
It is preferable that, in a sum of the moiety (
1
) and the moiety (
2
), the chlorine content ratio is 10-40 weight % and the molecular weight is 3000-200000.
It is preferable that the moiety (
3
) includes a styrene based monomer unit (
3
a
) at 10-70 weight % of the whole moiety (
3
).
A production process of an emulsion according to the present invention comprises:
a suspension preparing step of obtaining a suspension including:
a precursor, which includes a polyolefin chloride structure moiety (
1
) and an acid anhydride and/or carboxylic acid structure moiety (
2
) bonded to the moiety (
1
), wherein a ratio of the moiety (
2
) to a sum of the moiety (
1
) and the moiety (
2
) is 1-10 weight %;
a styrene based monomer;
a first acryl based monomer, which has a group reactable with the moiety (
2
);
a second acryl based monomer, which does not have a group reactable with the moiety (
2
);
an emulsifier;
a basic substance including at least one of an amine compound and ammonia;
an oil soluble polymerization initiator; and
water; and
a reaction step of heating the suspension and grafting a styrene-acryl based polymerization chain to the precursor.
It is preferable that the suspension preparing step comprises the step of obtaining a homogeneous solution of the precursor by mixing the precursor at least with a styrene based monomer, a first acryl based monomer and a second acryl based monomer and further comprises the step of obtaining the suspension by mixing the homogeneous solution at least with water.
DETAILED DESCRIPTION OF THE INVENTION
[Emulsion]
An emulsion according to the present invention comprises a styrene-acryl-acid grafted polyolefin chloride (hereinafter, called merely “grafted polyolefin chloride”), an emulsifier, a basic substance and water.
Hereinafter, the respective components making up this emulsion composition are explained in detail.
(Grafted Polyolefin Chloride)
Grafted polyolefin chloride used in the present invention is the main material of an emulsion according to the present invention and includes a polyolefin chloride structure moiety (
1
), an acid anhydride and/or carboxylic acid structure moiety (
2
) and a styrene-acryl based polymerization chain moiety (
3
). The moiety (
2
) is bonded to the moiety (
1
) as the main chain. The moiety (
2
) is, also, bonded to the moiety (
3
) excluding some of the acid anhydride groups and/or carboxylic acid groups.
As the grafted polyolefin chloride includes the polyolefin chloride structure moiety (
1
), the emulsion sufficiently coats polyolefin material.
As the acid anhydride and/or carboxylic acid structure moiety (
2
) is bonded to the moiety (
1
), the polyolefin chloride structure moiety (
1
) as the main material of an emulsion composition has, also, sufficient adhesion to polyolefin material.
Where moiety (
2
) is bonded to moiety (
1
), some of the acid anhydride groups and/or carboxylic acid groups remain and any remaining group becomes a free group and/or carboxyl anion by a reaction with a basic substance and exhibits water solubility. Therefore, the polyolefin chloride structure moiety (
1
) can be easily emulsified and ha

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