Plastic and nonmetallic article shaping or treating: processes – Mechanical shaping or molding to form or reform shaped article – Shaping against forming surface
Reexamination Certificate
1998-05-14
2001-05-29
Heitbrink, Jill L. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Mechanical shaping or molding to form or reform shaped article
Shaping against forming surface
C264S328700, C264S328100, C510S447000
Reexamination Certificate
active
06238612
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a process for forming detergent bars and detergent bars formed thereby. The detergent bars may be intended for personal wash or fabric wash.
BACKGROUND
One of the conventional methods of detergent bar manufacture is casting. In the casting process, a detergent composition in a heated, mobile and readily pourable state is introduced into the top of an enclosed cavity of the desired shape within a mould and the temperature of the composition is reduced until it solidifies either totally or partially, such that the bar is handleable. The mould is generally two-part, and the bar can be removed by opening the mould.
In order to be castable, the detergent formulation must be mobile and readily pourable at the elevated temperatures employed. The detergent melt, once in the mould, tends to cool slowly and unevenly. This can lead to unwanted structural orientations and segregation of ingredients.
Detergent formulations may be desired to be formed into bars in such a condition that they are not sufficiently fluid to be cast by conventional means. In this case, pressure can be used to deliver the detergent composition to the mould in, for example, an injection moulding process. The detergent composition will still require some further cooling and solidification within the mould cavity.
A major problem with such processes is that detergent compositions shrink in the mould as they cool and solidify. This is highly undesirable as the mould cavity is intended to impart a distinctive shape on the bar and often also a logo of some kind. Shrinkage can result in dimples, wrinkles or voids in the bar, or a depression at the fill point. Which of these bar imperfections occurs depends on factors such as the nature of the detergent composition at fill, the cooling mechanism employed, and the form and surface of the mould.
A further problem particularly associated with the delivery of semi-solid detergent compositions to a mould, is the formation of “weld lines” in the bars. Without being limited by theory, it is believed that as a material is delivered to a mould cavity, flow fronts of the material are created in the cavity as material is added and the cavity fills. Weld lines in the final bars are a result of interfaces between flow fronts of detergent material inside the mould cavity which have not blended together. Such weld lines may be visible to the consumer, and can lead to weaknesses in the bar, which may in turn lead to cracking in use.
Therefore, there is a need for a process for forming detergent compositions into good quality bars which have good appearance and physical characteristics. Such a process should prevent the imperfections so far associated with shrinkage, and, should allow the detergent composition to be fed to the mould in any desired physical state, and the bar formed to be any desired shape, with a well-defined logo if required.
The present inventors have found that if a pressure is applied to a detergent composition contained within a mould cavity then the problems associated with shrinkage of the detergent composition as it cools can be reduced.
Furthermore, the problems encountered when forming bars from semi-solid material, e.g. weld lines, can be alleviated and better logo definition can be obtained.
SUMMARY OF THE INVENTION
According to a first aspect, the present invention provides a process for forming detergent bars comprising applying pressure to a detergent composition contained within a mould cavity.
In order to maintain the total volume of detergent material in the mould cavity and improve shape reproduction, further detergent composition may be delivered to the mould cavity as the volume of detergent composition in the mould cavity decreases as it cools and shrinks.
Thus, according to a second aspect, the present invention provides a process for forming detergent bars comprising feeding a detergent composition into a mould cavity until it is substantially full and then creating a pressure on the detergent composition in the mould cavity by applying a pressure to a feed of a detergent composition in fluid contact with the material contained within the cavity.
If the detergent composition being delivered to a mould contains a quantity of a compressible material, e.g. a gas, then when a pressure is applied to the detergent composition contained within the mould, the volume of the compressible material will reduce. If the mould cavity is then closed, subsequent volume reduction of the detergent material (e.g. shrinkage on cooling) enables the compressible material volume to increase, thus maintaining the overall shape and volume of the bar.
Thus, according to a further aspect, the present invention provides a process for forming detergent bars comprising applying a pressure to a detergent composition contained within a mould cavity characterised in that the detergent composition contains a compressible gas component dispersed therein.
Unless specified more generally, references herein to the invention or to any preferred features apply to all aspects of the invention.
DETAILED DESCRIPTION OF THE INVENTION
Detergent compositions to be delivered to the mould can be in any form capable of being delivered to the mould. For example, the composition may be in a substantially fluid (e.g. molten, molten dispersion, liquid), substantially semi-solid or almost solid form, so long as the composition is sufficiently plastic to allow the material to be delivered to the mould as would be understood by the person skilled in the art.
The present invention envisages that detergent compositions which are not readily mobile and pourable (i.e. which are not conducive to casting) can be fed into a mould and formed into bars by techniques such as injection moulding.
Preferably, the detergent composition entering the mould cavity is in a substantially fluid or semi-solid state. A detergent composition may be considered to be in a semi-solid state if sufficient structure is present in the composition so that it no longer behaves like a simple liquid, as would be understood by the person skilled in the art. The term “melt” as used hereinafter, can include detergent compositions in a substantially fluid or semi-solid state.
Where the pressure applied to the mould is applied over a small cross-sectional area, e.g. at the gate of the mould, it will be clear to the skilled person that the benefits of the present invention will not be obtained if the material in the mould cavity is allowed to solidify to too great an extent before a pressure is applied. Preferably, the material in the mould is in a substantially fluid or semi-solid state when the pressure is first applied.
The material should be such that it is capable of transmitting pressure applied for example at the gate of the mould cavity, through the material in the cavity.
Preferably, pressure is applied to the detergent material contained within the mould cavity whilst at least part of the detergent material therein is solidifying.
Preferably, the mould is substantially full before the pressure is applied.
Moulds used in detergent bar manufacture typically comprise a cavity defined by a rigid material. Typically, a mould comprises two (or more) rigid complementary die parts which on engagement define a cavity corresponding to the total shape of the article to be manufactured in a casting or injection moulding process and a gate. The detergent melt is fed to the mould cavity through an orifice or “gate” in the mould. The gate opens on one side to the cavity and may open on the other side to a neck (e.g. a small channel) through which detergent composition can be fed to the mould cavity. The neck may be designed to hold a relatively large quantity of detergent material, e.g. up to 20% of the mould cavity volume, if desired.
Moulds are generally constructed of materials with high thermal conductivity, e.g. aluminium. This is to aid cooling of the melt and hence shorten bar release times. The mould will be designed so that it can withstand the envisaged applied pressures without leakage,
Allan Peter Stewart
Cordell John Martin
Irving Graeme Neil
Nadakatti Suresh Murigeppa
Naik Vijay Mukund
Heitbrink Jill L.
Koatz Ronald A.
Lever Brothers Company Division of Conopco, Inc.
LandOfFree
Process for the production of a detergent composition does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for the production of a detergent composition, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for the production of a detergent composition will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2527422