Title:  Process for producing a solvent-less O/W type emulsion

United States Patent:  6,153,657

Assignee:  Hodogaya Chemical Co., Ltd. (Kanagawa, JP)

Filed:  June 1, 1998

Foreign Application Priority Data:  Jun 02, 1997[JP] (9-143684); Jun 06, 1997[JP] (9-149645)

An organic solvent-less O/W type emulsion having an excellent stability for storage and water-dilution is produced by a specific process in which (1) a mixture of (a) water with (b) an oily substance selected from oily effective materials and oily liquid materials, the oily substance and water being capable of forming an interface therebetween, (c) a high molecular weight surfactant and (d) a low molecular weight surfactant is stirred at a temperature of 40^oC. or less, to provide an O/W type emulsion; (2) the emulsion is heated to gel the emulsion; (3) the gel is heated to phase invert from O/W to W/O; (4) the W/O emulsion is cooled to a temperature below the gelling temperature; and (5) the resultant O/W emulsion is further stirred, and optionally in or after the cooling step (4), a particulate solid substance or an aqueous suspension thereof is mixed with the emulsion.

SUMMARY OF THE INVENTION

The above-mentioned object can be attained by the process of the present invention for preparing a solvent-less O/W type emulsion, which comprises the steps of:

(1) mixing (a) water with (b) an oily substance comprising at least one member selected from the group consisting of oily effective materials and oily liquid materials, the oily substance and water being capable of forming an interface therebetween, (c) a high molecular weight surfactant and (d) a low molecular weight surfactant, at a temperature of 40^oC. or less, while stirring the mixture to provide an O/W type emulsion;

(2) increasing the temperature of the resultant O/W type emulsion, which stirring the emulsion, until the O/W type emulsion is uniformly gelled;

(3) further increasing the temperature of the O/W type emulsion gel until the O/W type emulsion gel is phase-inverted to a W/O type emulsion gel;

(4) cooling the W/O type emulsion gel to a temperature below the gelling temperature in the step (2), to convert the W/O type emulsion gel to an O/W type emulsion; and

(5) stirring the resultant product at a temperature of 40^oC. or less, to prepare a O/W type emulsion containing no solvent and stable to dilution with water.

The process of the present invention optionally further comprises, after the cooling step (4), the step of (4a) mixing a water-scant soluble particulate solid substance comprising at least one member selected from the group consisting of solid effective materials and solid auxiliary additives, into the O/W type emulsion prepared in the step (4), in which the resultant mixture of the step (4a) is subjected to the stirring procedure of the step (5).

The process of the present invention optionally further comprises, after the cooling step (4), the steps of:

(4b) mixing a water-scant soluble particulate solid effective material and an additional high molecular weight surfactant into the cooled O/W type emulsion, while stirring the mixture at a temperature of 40^oC. or less; and

(4c) further mixing an additional low molecular weight surfactant having a molecular weight of 1100 or less and of at least 400 below

the molecular weight of each of the high molecular weight surfactant and the additional high molecular weight surfactant, into the mixture of the step (4h), to provide a mixture of a suspension of the solid effective material with the O/W type emulsion,

in which the resultant mixture of the step (4c) is subjected to the stirring procedure of the step (5),

The above-mentioned process of the present invention optionally further comprises, between the cooling step (4) and the mixing step (4b), the step of:

(4d) adding an additional particulate solid effective material which is scant soluble in water and soluble in the oily substance, into the O/W type emulsion produced in the step (4), which stirring the mixture at a temperature of 40^oC. or less, to allow the additional particulate solid effective material to be dissolved in the oily substance in the O/W type emulsion,

in which the resultant O/W type emulsion obtained in the step (4d) is subjected to the mixing procedure of the step (4b).

The process of the present invention optionally further comprises the steps of:

(6) preparing, separately from the steps (1) to (4), an aqueous suspension of a water-scant soluble particulate solid effective material which is substantially insoluble in the oily substance, in an aqueous medium containing an additional high molecular weight surfactant and an additional low molecular weight surfactant having a molecular weight of 1100 or less of at least 400 below that of the high molecular weight surfactant and the additional high molecular weight surfactant; and

(7) mixing the resultant solid effective material suspension into the O/W type emulsion prepared in the step (4), in which the resultant mixture of the step (7) is subjected to the stirring procedure of the step (5).

The process of the present invention optionally further comprising the steps of:

(6) preparing, separately from the steps (1) to (4), an aqueous suspension of a water-scant soluble particulate solid effective material which is substantially insoluble in the oily substance, in an aqueous medium containing an additional high molecular weight surfactant and an additional low molecular weight surfactant having a molecular weight of 1100 or less and of at least 400 below that of the high molecular weight surfactant and the additional high molecular weight surfactant; (4b) after the cooling step (4), adding an additional particulate solid effective material which is scant soluble in water and soluble in the oily substance, into the O/W type emulsion produced in the step (4), which stirring the mixture at a temperature of 40^oC. or less, to allow the additional particulate solid effective material to be dissolved in the oily substance in the O/W type emulsion; and (7a) mixing the solid effective material suspension of the step (6) into the O/W type emulsion of the step (4b),

in which the resultant mixture of the step (7a) is subjected to the stirring procedure of the step (5).

Claim 1 of 26 Claims

We claim:

1. A process for preparing an O/W type emulsion which comprises the steps of:

(1) mixing

(a) water with

(b) an oily substance comprising at least one member selected from the group consisting of (i) oily effective materials which are selected from the group consisting of oily cosmetic materials, oily food materials, oily medicaments, oily agricultural chemicals, oily sanitary chemicals, oily home-use chemicals, oily office-use chemicals and oily industrial chemicals, and (ii) oily liquid materials which are different from the oily effective materials and are selected from the group consisting of vegetable oils, animal oils, mineral oils, synthetic oils, silicone oils and fluorinated oils, the oily substance (b) and water (a) being capable of forming an interface therebetween,

(c) a high molecular weight surfactant having a molecular weight of 1100 to 700,000, and

(d) a low molecular weight surfactant having a molecular weight of 1100 or less and of at least 400 below the molecular weight of the high molecular weight surfactant (c), at a temperature of 40^oC. or less, while stirring the mixture to provide an O/W type emulsion,

____________________________________________
If you want to learn more about this patent, please go directly to the U.S. Patent and Trademark Office Web site to access the full patent.