Plastic and nonmetallic article shaping or treating: processes – Mechanical shaping or molding to form or reform shaped article – Shaping against forming surface
Patent
1991-12-26
1993-08-17
Heitbrink, Jill L.
Plastic and nonmetallic article shaping or treating: processes
Mechanical shaping or molding to form or reform shaped article
Shaping against forming surface
425384, 425407, C11D 1316, B30B 1534
Patent
active
052366545
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to the stamping of soap and/or detergent bars. By "soap and/or detergent" bars we means both toilet and laundry bars made from conventional soap (ie. alkali metal salts of long chain monocarboxylic acids) or non-soap detergents or a mixture of soap and non-soap detergents. "Bars" includes cakes, tablets and the like. For convenience the bars will generally be referred to below as "soap bars".
Stamping of soap bars is traditionally performed on extruded billets in order to produce bars having a pleasing and uniform appearance. The stamping operation using pairs of co-acting die members can however be a frequent source of problems on a production line. A potential major problem is die blocking which results in imperfections appearing in the stamped bars due to small amounts of soap sticking to the stamping surface of the die members. A number of solutions to this problem have been proposed over the years but none has proved totally satisfactory.
It has for example been the practice of the applicants to operate die chilling techniques in their soap bar production lines. Such a practice has traditionally been accepted as an aid to improving the stamping of soap bars. Die blocking still however occurs to a high enough level to effect the output of acceptable soap bars. The coolant frequently used has been 50% aqueous glycol solution at a temperature of between -30.degree. and -20.degree. C. Such a system did produce some sort of benefit. Little attention has however been paid to the rationale and overall effectiveness for the chilling system that has been employed over the years either by ourselves or we believe by other soap manufacturers.
For example U.S. Pat. No. 2,987,484 (The Procter & Gamble Company) dates from 1959 and relates to a process for closed die molding in which a fluid mixture of synthetic detergent and a binder vehicle is injected into a closed die and forms a strong shape retaining shell in a substantially closed precooled mould. After solidification to at least a shape-sustaining form the bar is ejected from the mould for further cooling as necessary. The mould is said to be suitably precooled to a temperature in the range of about -30.degree. F. to about +40.degree. F. (-34.degree. to +4.degree. C.) and preferably to a temperature in the range of about -10.degree. F. to about +30.degree. F. (-23.degree. to -1.degree. C.) for optimum results, such as minimum tendencies for the bar compositions to stick, crack or require long holding times in the mould. The optimum mould temperature within this range varies with the composition of the melt, the melting point of the mix, and the temperature of the melt as it is injected into the mould. U.S. Pat. No. 2,987,484 is thus concerned with the particular problems associated with the closed die molding of fluid mixtures. It is noteworthy however that no details are given about the operation of the cooling system applied to the mould.
According to the present invention there is provided a process for stamping soap and/or detergent bars using Co-acting die members wherein a liquid coolant is circulated through tubes, having a diameter within the range 2 to 20 mm, formed within the die members, characterised in that the liquid is circulated through the die members under turbulent flow conditions.
Turbulent flow conditions can be achieved in a number of ways. Preferably the turbulent flow conditions are achieved by use of a high throughput pump. Alternatively or additionally turbulent flow conditions can be achieved by use of die members having tubes with a diameter less than a predetermined width. Suitably the throughput of coolant through tubes having a diameter within the range to 2 to 20 mm in the die members, in order to achieve turbulent flow conditions, should be within the range 100 to 10,000 liters/hour. A typical flow rate will lie in the range 150 to 4000 liters/hour while the flow velocity is 2 to 10 meters/sec (contrasting with 0.2 meters/sec for laminar flow). Stated more generally it is desirable that the linear
REFERENCES:
patent: 2987484 (1961-06-01), Lundberg
patent: 3271834 (1966-09-01), Mazzoni
patent: 3449804 (1969-06-01), Moses et al.
patent: 3907486 (1975-09-01), Kennedy
patent: 4067946 (1978-01-01), Rickert
patent: 4278230 (1981-07-01), Allen
Adams Michael J.
Edmondson Brian
Heitbrink Jill L.
Koatz Ronald A.
Lever Brothers Company
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