Plastic and nonmetallic article shaping or treating: processes – With step of making mold or mold shaping – per se
Reexamination Certificate
2000-05-10
2004-08-24
Colaianni, Michael (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
With step of making mold or mold shaping, per se
C264S320000, C425S185000, C425S344000
Reexamination Certificate
active
06780362
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a modular die or mold and to a process for stamping or molding a plastic material using such die or mold to form a shaped article. In particular, it relates to a process for stamping a detergent bar and/or for molding an insert for a bar stamping die.
By “detergent bar” is meant a tablet, cake or bar in which the level of surface active agent, which comprises soap, synthetic detergent active or a mixture thereof, is at least 20 wt. % based on the bar.
BACKGROUND OF THE INVENTION
In the manufacture of detergent bars, a preformed composition comprising all components of the bar is typically extruded from a nozzle to form a continuous “rod” which is cut into smaller pieces of predetermined length, commonly referred to as “billets.” These “billets” are then fed to a stamper or, alternatively, are given an imprint on one or more surfaces using, for example, a die of the same dimensions as the bar surface. The bar surface is hit with force by, e.g., a mallet or a die in the shape of a roller.
Stampers typically have a die formed in two halves each with a surface which contacts the billet during the stamping operation. These surfaces are adapted to close to a preset separation distance, thereby compressing the billet between the die halves to give the bar its final shape and appearance, and then separate. Excess composition is squeezed out from the die halves as they close. This is commonly referred to as “flash.” The flash is then separated from the soap bar by transferring the bar through holes in a “deflashing plate.”
Conventional die stamping machines include “pin die” shaped machines in which a pair of opposing die members or die halves meet during a compaction step, and a “box die” machine in which a pair of opposing die members stamp a bar held within a through-opening in a box frame but do not meet during compaction, the peripheral face of the bar being restrained by the box frame.
The die halves are often each provided with a die or ejector insert. These are normally held closed within the die halve by springs but can be pushed open by compressed air or mechanical means to assist in the release of the bar from the die. During closing of the die halves a vacuum can be applied to remove air trapped in the die cavity between the detergent bar and die surface and, in the case of rotary dies, this vacuum assists in retaining the bars in place during rotation.
Stamping of detergent bars using a die is carried out to give the bars a reproducible shape, smooth surface and/or to imprint a design such as a logo, trade mark or the like onto at least part of a surface of the bar.
However, as a result of die-blocking, i.e. amounts of residual detergent left on die halves which builds up during continued use of the dies, bars are often formed with visible imperfections on their surfaces or they may not release from the die surface. Numerous solutions to these problems have been proposed. One solution involves chilling the die halves during the stamping operation. Chiling uses valuable resources, particularly energy sources.
Another solution is described in GB-A-746 769 which discloses a die set which includes a die box and a pair of companion die members made of plastic materials comprising polymers with a specified modulus of elasticity. A disadvantage of this system is that a die release agent is necessary to prevent detergent from adhering to and building up on the dies and marring the surfaces of subsequently pressed bars.
WO 98/11194 is directed to a device for handling plastic materials such as a stamping device for stamping detergent bars, comprising at least two elastomeric coatings of different properties and/or compositions. Surface decorations such as uniform shape, smooth surface, design such as a logo, trademark or the like are said to be achievable in an easily reproducible manner in accordance with the invention. An advantage of thin elastomeric coatings is said to be that they can be easily applied in a factory to a conventional die with a built in logo. In describing the figure, it is said that a logo (not shown) may be formed on one or more of the die stamping surfaces if required.
Roberts, U.S. Pat. No. 3,534,440 discloses bodies of soap, detergent and the like which are pressed to final shape and/or size with indented or raised surface indicia in a die press. A detachable and replaceable section of embossed tape bearing the indicia is mounted on either an upper die pressing face or a bottom of a cavity or both. It is said that the invention may be used for synthetic detergent bars as well. Permanent indicia are said to restrict the dies to one usage run. Dies with replaceable inserts are said to be known. The thin embossable material embossed with the desired indicia may be attached by pressure sensitive adhesive means to one or more pressing faces of a pair of dies. It is said that while the tape seems relatively fragile, it does not rupture or deform under the high soap forming pressures and it is said to be believed that the air trapped in spaces opposite the embossed characters cooperates with inherent resiliency of the strip material effectively to uniformly cushion the strip to prevent destructive localized stress regions.
Cubbitt, U.S. Pat. No. 3,522,633 is directed to a die member comprising a rigid metal body having a forming surface provided with a panel receiving recess wherein a plastic design-bearing panel is molded in place. The panel has a surface that is substantially continuous with the die forming surface except for interruption by the design to be imparted to the article formed by the die. The panel is removable and replaceable by a different mold in place panel bearing a different design. The dies are for pressing of soap or like relatively soft material in bar cakes or any desired compact form.
An object of the Cubbitt invention is said to be to provide a novel soap pressing die structure wherein part of the internal soap contacting and forming surface of the die is a specially formed plastic panel for providing a desired design on the pressed soap bars. A further object of the invention is said to be a novel method of making a soap die member having a soap contacting and forming surface wherein an insert panel or the like is formed as by molding or casting into a recessed inset surface, the panel having an exposed surface which except for a design is essentially a continuation of the die pressing surface wherein the incorporated panel is removable for molding or casting a substitute panel. Should a different design be desired, panel
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is displaced and replaced with another panel that is identical except for surface design. The replaceable panel may be formed in place on the metal die member using a master blank of hard non-deformable plastic. Preferably the panel material is a thermosetting material although it is said that thermoplastic material may also be used.
Pinto, U.S. Pat. No. 3,127,457 discloses a fluorocarbon film used as a release agent for molding polyurethane articles.
Krugg, U.S. Pat. No. 3,539,144 discloses a mold useful for producing polyurethane foams, which includes a structural mold shape and a coating of hot vulcanized silicon rubber disposed on the structural mold as well as a cold vulcanized silicone rubber deposited on the hot vulcanized silicon rubber.
Cavanugh, U.S. Pat. No. 4,035,122 discloses a soap saving device for compressing remnants of soap bars.
Austin, U.S. Pat. No. 4,076,207 discloses a food mold comprising a liner and a rigid holder wherein the liner has a rim for securement to the holder.
Roussel, U.S. Pat. No. 4,809,945 discloses a mold cavity for use in molding articles such as soap bars.
Watanabe, U.S. Pat. No. 5,332,190 discloses an elastic molding die composed of an elastomer laminate film, the innermost layer of which does not contain fillers.
In U.S. Pat. No. 5,269,997 it is proposed to provide each of two dies of a soap mold with an elastomeric septum stretched across their surfaces. Such a system would be complex to use at the speed required f
Buzzeo Pasquale Michael
Heinz Daniel John
Lathrop Gregory Alan
Story Edward Ross
Bornstein Alan A.
Colaianni Michael
Poe Michael I.
Unilever Home & Personal Care USA , division of Conopco, Inc.
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