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...
Reexamination Certificate
1999-02-10
2001-07-17
Mulcahy, Peter D. (Department: 1713)
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...
C525S077000
Reexamination Certificate
active
06262160
ABSTRACT:
DESCRIPTION
1. Technical Field
The present invention relates to: a water base adhesion promotor for improving the paint adhesion to polypropylene materials; and a method for coating to polypropylene materials using the promotor.
2. Background Art
Polyolefins such as polypropylene are comparatively cheap and has excellent properties such as formability and chemical resistance, so they are widely used in the industrial fields including the automobile industry. The amount thereof as used tends to increase, because their recycling is possible and because their prices are low. Polypropylene materials are, for example, used for exterior decoration parts of automobiles, such as bumpers and molds, and their surfaces are usually coated to both improve their weather resistance and give the design property thereto.
The polypropylene material is inferior in wettability. Therefore, when being coated with a paint, the polypropylene material undergoes the following treatments: first, a degreasing treatment with a water base cleaning agent and a pretreatment to enhance the wettability using a surface-active agent, and then coating and baking treatments of a primer, and then a coating treatment of a paint. Incidentally, the coating treatment of the primer is carried out to enhance the adhesion of paints, but, in fact, as much as about 70% of the amount of the primer as used is blown off and therefore is not effectively used, thus resulting in high coating cost. Furthermore, there are problems in that: the primer needs to be baked after being coated, so a large baking furnace is needed and the equipment cost is therefore high.
From the above circumstances, it is desired to develop a method for coating to polypropylene materials without coating the primer.
DISCLOSURE OF THE INVENTION
Object of the Invention
An object of the present invention is to provide: a water base adhesion promotor to enhance the paint adhesion to polypropylene materials instead of the primer coating; and a method for coating to polypropylene materials using the promotor.
Summary of the Invention
The present inventors made various examinations and experiments to solve the above problems. As a result, they attained the present invention by finding that: a composition, comprising a grafted polypropylene chloride of high adhesion to polypropylene materials, an amine-neutralized water-soluble resin of high water resistance, and a wettability-improving agent, could enhance the paint adhesion to polypropylene materials, so that the primer coating could be omitted.
That is to say, a water base adhesion promotor for polypropylene, according to the present invention, comprises:
a grafted polypropylene chloride, which includes a polypropylene chloride moiety and a maleic anhydride moiety as bonded thereto, and which has a chlorine content of 15~25 weight % and a maleic anhydride moiety content of 1~5 weight %;
an amine-neutralized water-soluble resin;
a wettability-improving agent; and
water;
and is characterized by having:
a combination ratio of 25~90 weight % as of the grafted polypropylene chloride to the total of the grafted polypropylene chloride and the amine-neutralized water-soluble resin;
a combination ratio of 2.5~6.0 weight % as of the wettability-improving agent to the entirety of the promotor; and
a solid content of 2~10 weight % of the entirety of the promotor.
A method for coating to polypropylene materials, according to the present invention, comprises:
a pretreatment step in which a polypropylene material is beforehand washed, and then immersed into the above water base adhesion promotor, and then dried; and
a coating step in which a paint is coated to the material after the pretreatment step.
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, each component, constituting the present invention water base adhesion promotor for polypropylene, is explained in detail, and then the water base adhesion promotor for polypropylene and the method for coating to polypropylene materials are explained.
(Grafted Polypropylene Chloride):
The grafted polypropylene chloride, as used in the present invention, is a component to enhance the adhesion to polypropylene materials. The grafted polypropylene chloride is a polypropylene derivative which includes a polypropylene chloride moiety and a maleic anhydride moiety as bonded thereto, and is usually used in the form of an emulsion having the high handling property.
The polypropylene chloride moiety is a moiety comprising a polypropylene having at least one chlorine atom as a substituent. In addition, the maleic anhydride moiety is a moiety as obtained by grafting maleic anhydride, and has a cyclic acid anhydride group (deriving from maleic anhydride) and/or two free carboxyl groups.
The grafted polypropylene chloride is a product by reacting a polypropylene upon maleic anhydride and chlorine to internally graft the polypropylene, and is, for example, produced by reacting chlorine and maleic anhydride upon a polypropylene. Incidentally, whichever of chlorine and maleic anhydride may be reacted earlier than the other. The reaction with chlorine is, for example, carried out by introducing a chlorine gas into a solution including a polypropylene. In addition, the reaction with maleic anhydride is, for example, carried out by reacting maleic anhydride upon a polypropylene (or its chloride) in the presence of a peroxide.
The chlorine content in the grafted polypropylene chloride is in the range of 15~25 weight %, preferably 18~22 weight %. In the case where the chlorine content is less than 15 weight %, the melting point of the grafted polypropylene chloride is so high that the crystallization easily occurs and that the emulsification is difficult, thus resulting in depression of the storage stability of the resultant water base adhesion promotor. On the other hand, in the case where the chlorine content exceeds 25 weight %, the grafted polypropylene chloride is noncrystalline, thus resulting in depression of the adhesion and the water resistance.
The maleic anhydride moiety content in the grafted polypropylene chloride is in the range of 1~5 weight %, preferably 3~4.5 weight %. In the case where the maleic anhydride moiety content is less than 1 weight %, the emulsification is difficult, thus resulting in depression of the storage stability of the resultant water base adhesion promotor. On the other hand, in the case where the maleic anhydride moiety content exceeds 5 weight %, the acid anhydride group content is too much, thus resulting in depression of the adhesion and the water resistance.
The weight-average molecular weight of the grafted polypropylene chloride is not especially limited, but is preferably in the range of 20,000~100,000, more preferably 30,000~80,000. In the case where the weight-average molecular weight is less than 20,000, the promotor might swell with a solvent for a top paint, so that the adhesion might be deteriorated. On the other hand, the weight-average molecular weight exceeds 100,000, the viscosity of the resultant water base adhesion promotor might be so high that the emulsification might be difficult and that the storage stability might be low.
(Amine-neutralized Water-soluble Resin):
The amine-neutralized water-soluble resin, as used in the present invention, is a resin as water-solubilized by neutralization with an amine, and is a film-formable component having high water resistance. Incidentally, for example, water-soluble resins, which are not obtained by the amine neutralization, such as polyethylene glycol and polyvinylpyrrolidone, merely have low water resistance, because, even after film formation by drying, such water-soluble resins remain and retain its water solubility. In comparison, the amine-neutralized water-soluble resin, as used in the present invention, displays high water resistance, because it volatilizes the amine in the drying step, and thus loses the water solubility.
The amine-neutralized water-soluble resin, as used in the present invention, is not especially limited if it is a resin as neutralized with an amine, and examples thereof
Igarashi Kazuo
Kamei Sawako
Kawano Shinnosuke
Komatsu Yasunori
McBride Laura
Mulcahy Peter D.
Nippon Bee Chemical Co., LTD
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