The present invention relates generally to a pigment dispersion composition suitable for use in producing gloves having a metallic lustrous appearance. BACKGROUND OF THE INVENTION

Colour on gloves are usually used to indicate material, whether they are latex or non-latex gloves. Further, it can be used to indicate purpose, such as for laboratory use, surgery use, or food preparation. Gloves with metallic lustrous appearance are desirable because of its visually pleasing appearance especially for skincare, spa, salon and other cosmetic related business.

There are a few patented technologies related to production of gloves having metallic lustrous appearance. For instance, Chinese Patent Application Publication No. CN 1807493 A disclosed a recipe and method for manufacturing a kind of rubber glove which has pearl gloss. More particularly, a pearlescent pigment dispersion composition was disclosed. The pearlescent pigment dispersion composition comprises pearlescent pigments in 20% to 40%, a dispersant in 1% to 2%, a stabilizer in 0.04% to 0.1%, and the balance being soft water. The dispersant used was methylene bis-naphthalene sulfonate, ethylene oxide, casein, or a combination thereof.

Another example is disclosed by Chinese Patent Application Publication No. CN103554568 A. More particularly, CN 103554568 A disclosed a formula of rubber gloves comprises the following components in parts by weight: 30-50% of luminous pigment, 1-2% of dispersing agent, 0.04-0.1% of stabilizing agent, 3-6% of oxidizing agent, 2-5% of zinc oxide and the balance of soft water.

In view of the above, both CN 1807493 A and CN103554568 A disclosed the use of ethylene oxide (EO) as dispersing agent. However, the addition of EO causes formation of foam in latex compounding that can contribute to formation of pinhole in gloves.

It was found that unstable pearlescent pigment often forms large amount of sediment in a latex compounding. Thus far, there is no found prior art capable of producing a pigment dispersion composition without hard sediment for a period 3 months after mixing with a latex compounding. This invention provides an alternative pigment dispersion composition suitable for use in producing gloves having a metallic lustrous appearance. More particularly, the pigment dispersion composition is able to reduce the amount of pigment sediment in a dipping tank.

SUMMARY OF THE INVENTION

One object of the present invention is to provide a pigment dispersion composition for producing gloves having a metallic lustrous appearance.

One object of the invention is to provide a pigment dispersion composition suitable for latex compounding, such that it reduces the amount of pigment sediment in a dipping tank.

One object of the present invention is to provide a coloured glove suitable for various applications such as for use in the field of cosmetic, for example, skincare, spa centres, hair or makeup salons.

At least one of the preceding objects is met, in whole or in part, by the present invention, in which one of the embodiments of the present invention is a pigment dispersion composition capable for use in producing gloves having metallic lustrous appearance, comprising: 20 to 40 wt % of pearl pigment powder; 0.01 to 10 wt% of dispersing agent; 0.01 to 10 wt% of rheology modifier and water, characterised in that the dispersing agent is sodium salt of polyacrylic acid, and maleic acid-acrylic acid copolymer, or salts derived thereof.

Preferably, the rheology modifier is a mixture comprising 0.01 to 10 wt% of pH adjuster and 0.01 to 10 wt% of thickener. Preferably, the pH adjuster is potassium hydroxide, sodium hydroxide, or ammonium hydroxide.

Preferably, the thickener is acrylic copolymer or hydroxyethylcellulose. Advantageously, the pearl pigment powder has a particle size of less than or equal to 20 μη .

BRIEF DESCRIPTION OF THE INVENTION

This invention relates to a pigment dispersion composition suitable for use in producing gloves having a metallic lustrous appearance.

Exemplary, non-limiting embodiments of the invention will be disclosed. However, it is to be understood that limiting the description to the preferred embodiments of the invention is merely to facilitate discussion of the present invention and it is envisioned that those skilled in the art may devise various modifications without departing from the scope of the appended claim. The present invention is a pigment dispersion composition comprising 20 to 40 wt % of pearl pigment powder; 0.01 to 10 wt% of dispersing agent; 0.01 to 10 wt% of rheology modifier; and water, characterised in that the dispersing agents is sodium salt of polyacrylic acid, and maleic acid-acrylic acid copolymer, or salts derived thereof.

In the preferred embodiment, the pigment dispersion composition is a dispersion having 20 to 40 % of solid content, a Brookfield viscosity less than 2000 (cP), preferably 500 to 1800 (cP), a specific gravity at 25° C of 1.1 to 1.3 g/cm ² , and a pH of 8 to 10. It is preferred that the pigment dispersion composition is stirred for 24 to 48 hours prior to use.

In accordance to preceding description, the pigment dispersion composition comprises a rheology modifier. Preferably, the rheology modifier in the present invention is a mixture comprising 0.01 to 10 wt% ofpH adjuster and 0.01 to 10 wt% of thickener. The pH adjuster provides stable pH environment while the thickener increases viscosity of the dispersion composition. This provides a stable environment for the dispersion composition. The pH adjuster can be potassium hydroxide (KOH), sodium hydroxide (NaOH), or ammonium hydroxide (NH ₄ OH). The thickener is acrylic copolymer or hydroxyethylcellulose.

The pearl pigment powder is preferably mica oxide, but not limited thereto. Pearl pigment powder having specific density of 2.9 to 3.0 g/cm ² can be used. As pearl pigment powder having a fine particle size provides better sparkling effect on the gloves, the pearl pigment powder used can be subjected to ball milling, or any suitable process in the art, so as to reduce its particle size. More preferably, the pearl pigment powder in the pigment dispersion composition has a particle size of less than or equal to 20 μηι, more particularly in a range of 5 to 20 μιη. Table 1 shows the correlation between particle size of pigment dispersion composition and its separation rate upon mixing with a compounding blend of copolymer of acrylonitrile and butadiene without milling. As a result, the dispersion is able to stay without hard sediment for a period 3 months with the separation rate less than 85mm/month. Table 1 : Correlation between particle size and separation rate of pigment dispersion composition in a preferred embodiment of the invention.

Water used in the pigment dispersion can be tap water, but not limited thereto. Alternatively, soft water can also be used due to its low concentration of ions, particularly calcium and magnesium ions. This can reduce the reaction of ions with the dispersing agent.

The aforementioned pigment dispersion composition is suitable for use in latex compounding for producing natural rubber gloves, nitrile gloves, polyisoprene glove, or polychloroprene gloves. More particularly, the pigment dispersion composition in the present invention is used for producing nitrile gloves, in which the latex compounding includes copolymer of acrylonitrile and butadiene, carboxylated copolymer of acrylonitrile and butadiene, or a mixture thereof. Preferably, 1 to 10 % by weight of the pearl pigment composition can be added into a latex compounding so as to produce gloves having metallic lustrous appearance. Higher pearl pigment dispersion composition used will give better lustrous effect on glove samples produced. Conventional glove manufacturing procedures known in the art can be applied. EXAMPLE

An exemplary embodiment of the pigment dispersion composition is disclosed.

EXAMPLE 1 At approximately 25 °C, 23 kg of pearl pigment powder having particle size of approximately 20 μηι, 1 to 10 kg of rheology modifier, 1 kg to 10 kg of dispersing agent (a mixture of sodium salt of polyacrylic acid and maleic acid-acrylic acid copolymer) were added into 60 kg of tap water in the presence of continuous stirring. A metallic white dispersion is obtained. The dispersion has 27 % of solid content, a Brookfield viscosity at 25° C of 1800 Cp, a specific gravity at 25° C of 1.10 to 1.30 g/cm ² , and a pH of 8 to 10. The dispersion was stirred for 24 to 48 hours and kept for storage. The dispersion is able to stay without hard sediment for period 3 months with the separation rate less than 85mm/month. Thereinafter, of the dispersion was added into a dipping tank having conventional latex compounding for producing nitrile rubber gloves. Procedures known in the art for producing gloves can be applied.

The present invention may be embodied in other specific forms without departing from its essential characteristics. The described embodiments are to be considered in all aspects only as illustrative and not restrictive. The scope of the invention is, therefore indicated by the appended claims rather than by the foregoing description. All changes, which come within the meaning and range of equivalency of the claims, are to be embraced within their scope.