CZ232599A3 - Process of making elastomer coating and apparatus for making the same - Google Patents

Abstract

In the present invention, there is described a process for forming an elastomeric coating using a device (10) for stamping a substrate, which device comprises a die (12) having at least one stamping surface (14) for stamping the substrate covered with an elastomeric coating (16), whereby this stamping surface (14) for stamping the substrate has an edge (30) with stiffness greater than that one of the elastomeric coating (16). The edge (30) forms a flange being flush with or projects slightly beyond the front edge of the die (12) elastomer coating, and the process comprises the steps of: (i) pretreating the device by chemical and/or mechanical means to form a bonding surface for said elastomeric coating; and (ii) applying said elastomeric coating to said device. Described is also a method for stamping a detergent bar, a device for stamping a substrate as well as the use thereof.

Description

The present invention relates to an apparatus and method for molding a plastic material using a press to form a shaped article. In particular, the present invention relates to a method for molding a detergent bar.

BACKGROUND OF THE INVENTION

By detergent bar is meant a tablet, bun, or bar in which the amount of surfactant, including soap, synthetic detergent, or mixtures thereof, is at least 20% by weight of the bar.

Typically, in the manufacture of detergent bars, a pre-blend comprising all of the bar components is extruded from the die to form a continuous bar that is cut into smaller pieces of a predetermined length, which are commonly referred to as blocks. These blocks are then fed to a press machine or, alternatively, are printed on one or more surfaces using, for example, a press of the same dimensions as the rod surface. The surface of the rod is driven by force by means of, for example, a mallet or press into the shape of a roller.

Pressing machines typically have a two-half press, each having a surface that contacts the block during the pressing operation. These surfaces are adapted to close to a predetermined separation distance, thereby compressing the block between the halves of the press to give the bar its final shape and appearance, and then separating it. The excess mixture is extruded from the halves of the press as they close. This is commonly referred to as an overflow. The overflow is then separated from the soap bar by passing the bar through the holes in the overflow removal plate.

Conventional dies include contoured presses in which a pair of opposed fasteners or press halves interfere during a press step, and a box press device in which a pair of opposed fasteners press a bar held within a through hole in the box frame but do not interfere during the pressing operation, the peripheral surface of the rod being bounded by a box-shaped frame.

The pressing halves are often each provided with a punch or an extrusion insert. These are usually held closed within the press half by means of springs, but can be forced out by compressed air or mechanical means to assist in releasing the rod from the press. During the closing of the press halves, a vacuum may be applied to remove air trapped in the press cavity between the detergent bar and the press surface, and in the case of rotary presses, this vacuum assists in holding the bars in place during rotation.

Pressing of the detergent bars using a press is performed to give the bars a reproducible shape, a smooth surface and / or to imprint a pattern such as a logo.

or at least a portion of the surface of the rod.

However, due to the clogging of the press, i.e., the amount of residual detergents remaining on the press halves that accumulate during continued use of the presses, the bars are often made with visible imperfections on their surfaces or the bars may no longer release from the press surface.

A number of solutions have been proposed to solve these problems. One solution involves cooling the pressing halves during the pressing operation. Cooling uses valuable resources, especially energy sources.

Another solution is described in GB-A-746 769 which discloses a press assembly comprising a press box and a pair of associated press members made of plastic materials comprising polymers with a specific modulus of elasticity. A disadvantage of this system is that a press release agent is needed to prevent detergents from adhering to and accumulating on the presses and from bonding to the surfaces of the subsequently pressed rods.

Luckow in US Patent No. 1,817,157 discloses a soap mold.

Pinto in U.S. Patent No. 3,127,457 discloses a fluorocarbon film used as a release agent for molding polyurethane products.

Krugg in U.S. Patent No. 3,539,144 discloses a mold usable for making polyurethane foams which includes a structural molding shape and a hot vulcanized silicone rubber coating disposed thereon, as well as a mold for forming polyurethane foams. Cold vulcanized silicone rubber, deposited on hot vulcanized silicone rubber.

Ladney in US Patent No. 3,889,919 discloses a plastic ventilation insert for a compression chamber for molding plastic 5 parts. The press cavity (26) of the device comprises a peripheral lip (28).

Cavanugh in US Patent No. 4,035,122 discloses a soap-saving device for pressing soap stick residues.

Austin in US Patent No. 4,076,207 discloses a food mold comprising an insert and a fixed holder, the insert having an edge for securing the holder.

Roussel in US Patent No. 4,809,945 discloses a mold cavity for use in molding articles such as soap bars.

Watanabe in US Patent No. 5,332,190 discloses an elastic molding press composed of an elastomeric laminate film whose inner layer does not contain fillers.

It is proposed in US Patent No. 5,269,997 to provide each of the two soap mold halves with an elastomeric insert extending over their surfaces. Such a system would be complex to use at the speeds required for commercial production, and the thin coating would tend to tear, with inadequate reproduction of the logo expected.

5

WO 96/00278 discloses a detergent bar pressing apparatus comprising a press having at least one rod pressing surface, the rod pressing surface having an elastomeric coating, the total thickness of the elastomeric coating being less than 200 µm. In preferred embodiments, the elastomeric coating is the only elastomeric material of the rod pressing surface.

Another solution is proposed in EP 276 971 and US Patents 5 No. 4,793,956 and No. 4,822,273, which disclose the use of two fasteners each comprising a non-elastomeric and an elastomeric portion. The elastomeric portion that contacts the soap bar during the molding process comprises an elastomeric coating having a thickness of at least 200 µm and having a modulus of elasticity within the specified range.

Manufacturing presses with thick coatings is a complex and costly process. Therefore, it is highly desirable to maximize the working life of such coatings.

GB-A-2276345 discloses a method of manufacturing articles such as soap bars using molds having at least a portion of their surface a modulus of elasticity to some extent. The disclosed mold may have sharp edges in which the edge of a portion having a given modulus of elasticity meets the bottom of the mold.

The difficulty associated with elastomeric coatings is that they tend to have a short working life of the order of several days or more. The problems it causes are obvious.

SUMMARY OF THE INVENTION

It has been found that the short working life of the elastomeric press coatings results from the high stress exerted by the press edge during the soap pressing operation. This is due to the high shearing forces of the soap pressing, which tend to be friable. tear the cover from the metal bottom of the press. This problem leads to the negation of the advantages of using presses coated with elastomeric coatings, for example the possibility of avoiding the use of expensive chilled metal presses.

It has been found that the stresses to which the elastomeric coatings are subjected can be reduced by using an edge or flange having a stiffness greater than that of the elastomeric coating of the press, in particular being similarly coated with the elastomer itself. Preferably, the edge or flange is made of metal or other hard or rigid material. The use of the metal edge results in reduced tearing of the elastomer by reducing the stresses to which the elastomer is subjected. Preferably the edge extends over the leading edge of the elastomer and thereby protects the elastomer from the applied pressures during compression. This noticeably improves the useful life of the elastomer coated press and allows the benefits of the coated presses to be realized without the disadvantage of an extremely short useful life.

Although it may be easier to form an edge of the same material as the press, this is not necessary.

The edge or flange may be made of a variety of materials, including urethane-based plastics and composite materials. In an advantageous embodiment, the edge is formed by a T-shaped or umbrella-shaped construction, the elastomer being protected under the top of the umbrella.

The present invention is particularly applicable to presses used to produce detergent bars having side walls extending generally perpendicular to the longitudinal axis of the bar, i.e., the belt bars. It is assumed that in the 4 presses with elastomeric coatings used for the production of strip rods, even greater stresses are achieved than in the presses with elastomeric coatings used for the production of rods without vertical side walls or whose vertical side walls extend only a short percentage of the height of the rod.

It is contemplated that the edge or flange of the present invention may also be used on a press which is itself made of an elastomeric material rather than being coated. The edge will generally be made of a harder material than the press.

For a more complete understanding of the above and other features and advantages of the present invention, a more detailed description of preferred exemplary embodiments 15 is presented below with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 shows a perspective view of the presses according to the present invention;

Giant. 2 shows a cross-sectional side view of a press according to the present invention;

Fig. 3 shows a front cross-sectional view of a press according to the present invention; and 5

Giant. 4 is a cross-sectional view of the press shown in FIG. 3 in which the press has been coated with an elastomeric coating.

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9 10 «» 9 · 4

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DETAILED DESCRIPTION OF THE INVENTION

The use of thick elastomeric coatings in soap bar pressing is described in EP 276971 and US Pat.

Nos. 4,793,959 and 4,822,273, the disclosures of which are hereby incorporated by reference.

In the following description, the term surface decoration refers to a uniform shape, a smooth surface and a designation such as a logo, trademark or the like.

The term elastomer according to the present invention means a material defined according to ISO 1382 (International Organization for Standardization) as elastomer or rubber. Thermoplastic elastomers and copolymers and mixtures of elastomers, thermoplastic elastomers and rubbers are also included in the definition of elastomeric materials according to the present invention.

Elastomers are defined as polymers with long elastic chains, independent of the raw material and transformed by vulcanization or cross-linking agents, which introduce cross-links and form a network structure. This mesh structure captures the movement of molecules in the macromolecular chains and, as a result, the polymer quickly returns to approximately its initial size and shape after deformation by force and release of this force.

As the temperature rises, the elastomer passes through the rubber phase after softening and retains its elasticity and modulus until the decomposition temperature is reached.

Thermoplastic elastomers include amorphous and crystalline phases. The amorphous phase has a softening range below

3Q ambient temperature, and thus acts as an elastic spring, while crystalline segments whose softening range is above three tiers three tiers three tiers. temperature, acts as crosslinking sites for crosslinking.

Preferably, the elastomeric material of the present invention is selected from the classes described by the American Society for Testing Materials under number D1418, including:

Unsaturated carbon chain elastomers (R class), comprising natural rubbers such as standard Malaysian rubber; butadiene such as BUNA supplied by Bunaweke Huls; and a butadiene-acrylonitrile copolymer such as Perbunan supplied by Bayer.

2. Saturated carbon chain elastomers (M class), including ethylene proplyene types such as Nordel supplied by DuPont; and fluorine containing types such as Viton supplied by DuPont.

3. Silicone-substituted elastomers (Q class), including liquid silicone rubbers such as Silastic 9050/50 P (A + B) supplied by Dow Corning.

4. Carbon, nitrogen and oxygen-containing elastomers in the polymer chain (U class), including polyurethanes, for example polyurethanes supplied by Belzona.

The elastomeric material as defined above may be pretreated, such as by forming a solution of a commercially available elastomer, before being applied as a coating to the press surface. Elastomers, rubbers and copolymers and mixtures thereof are generally cured.

• ♦ * * * * * * *

(vulcanized) or crosslinked in place on the press surface. For example, components including the base elastomeric material, crosslinking agents and other materials, such as accelerators, may be mixed prior to application as a coating. Once applied to the press surface, the coatings are cured in place. This may be supported by the application of heat or other acceleration processes, for example by pressure, radiation or UV light.

The elastomeric material may be applied as either liquid or semi-solid. For example, when applied as a liquid, the two press halves are held apart with a predetermined distance to allow the elastomers to occupy the space between the two parts. Preferably, the press is filled with an elastoraer under pressure.

In some cases, the materials may be dissolved with a suitable solvent, applied to the press surface, and the solvent subsequently removed.

In the case of thermoplastic materials, these materials can be heated to a molten state, applied to the press surface, cooled and rehardened.

The materials suitable as elastomeric coatings in the present invention will preferably have a modulus of elasticity in the range of 0.1 to 50 MPa, particularly preferably in the range of 1 to 35 MPa.

The elastic modulus of the elastomeric coating can be measured by recording the force required for indentation into the coating as a function of the indentation depth. Usually a spherical indentation can be used and the slope with force is determined as a function of the indentation depth with a power of 3/2. Depth of indentation

AND

is the displacement of the indentation into the coating after the indentation first contacts the surface of the coating. Generally, it is necessary to correct the measured indentation depth due to the meter's compliance. This means that the actual indentation depth d is related to the measured apparent indentation depth d by the following relation:

d = ï - (F.C) where F is the indentation force. The compliance C is determined by compressing the indentation against the rigid surface and recording the apparent displacement as a function of the applied force that has a slope equal to C. The modulus of elasticity E is calculated from the following expression:

E = 3/4: s 1 / (R) ^1/2 (1 - b ² ) where s = F / d ^3/2 , R is the radius of the ball tip and b is the Poisson coating constant, which for elastomers is approximately 0 , 5.

Under certain conditions, which will be described in the description below, the above-mentioned indentation method can provide false large values of the modulus of elasticity due to the effect of the rigid material to which the coating is applied. In order to avoid this problem with certainty, it is necessary to ensure that the contact radius of the indentation with the coating does not exceed approximately 1/10 of the coating thickness. The contact radius a is related to the indentation depth by the following expression:

a = (dR) ^1/2

For coatings less than 200 µm, it is recommended that a nanometric induction die capable of being used is used

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4 measurements of indentation forces at low indentation depths using indenters with a tip having a small radius. An example of such a device is Nanolntender II (Nano-instruments). An alternative is to perform a test on a thick coating (greater than 200 µm) so that more conventional measuring equipment such as an Instron tester (e.g., Model 5566) can be used.

Preferably, the press comprises a solid material selected from metals and their alloys, for example brass and other alloys of copper, aluminum, and steels including carbon and stainless steels; and other non-elastomeric materials such as thermosets and thermoplastics, for example polyester, epoxy resins, furan resins; hard cast polyurethanes; ceramics; composite materials and composite materials.

Additive materials, such as fillers, can be added to the elastomeric material to modify its mechanical and processing properties. The effects of adding filler depend on the mechanical and chemical interaction between the elastomeric material and the filler.

Fillers may be used to modify the elastomeric material so that the desired properties, such as tear resistance, are achieved. Suitable fillers include carbon black; silicon oxides; silicates; and organic fillers such as styrene or phenol resins.

Other optional ingredients include friction modifiers and antioxidants.

The edge or flange should extend from the wall of the press to cover the thickness of the coating cavity and preferably 30

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♦ coating outside the cavity. The edge dimensions for optimum performance are therefore determined by the desired coating thickness.

The thickness and hardness of the elastomeric coating may be varied according to the composition of the detergent bar, the processing temperature and / or process parameters such as the cavity shape in the press halves, the speed of the press device and the separation distance of the press halves to achieve the desired result. press. For presses bearing a more complex logo or for more complex press shapes, acceptable release from the press is enhanced by the use of thicker coatings and lower modulus of elasticity. Similarly, for the composition of the bar, which itself is harder to compress, an acceptable release from the press with a stronger elastomeric coating and / or a coating having a lower modulus of elasticity can be achieved.

The apparatus of the present invention can be used to mold a detergent bar comprising a surfactant which comprises essentially a soap or synthetic detergent or a mixture of soap and synthetic detergent. This device finds particular application in the pressing of soft and / or sticky detergent and / or soft bars containing synthetic surfactants, translucent and transparent soap bars having a reduced fatty content, for example in the range of 63 to% by weight relative to the total weight bars, and those bars containing agents suitable for treating the skin, such as wetting agents, polyols, oils, fatty acids, and fatty alcohols.

According to a further aspect of the present invention, there is provided a method for molding a detergent bar comprising:

i) forming an elastomeric coating on a press having an edge to delay the rupture of the elastomeric coating;

ii) feeding the detergent bar composition to the press formed in step i;

iii) compressing the mixture in a press to form a pressed rod; and iv) releasing the rod from the press, preferably in such a manner that the surface decoration is applied to the rod in an easily reproducible manner.

Preferably, the elastomeric coating is bonded to the press surface of the press by mechanical and / or chemical means to increase adhesion between the press and the coating.

It is particularly preferred that the edge used to relieve stress on the elastomeric coating is also partially coated with the elastomeric coating itself. Preferably, the edge coating is thinner than the coating present on the surface of the bar pressing press. For example, it may have a thickness ranging from 1 to

200 µm, preferably from 1 to 50 µm.

A detailed description will now be made in conjunction with the drawings. Giant. 1 shows the press halves 10 assembled from individual presses 12. Each press half 10 is provided with an elastomeric coating 16 on the press pressing surface 14 (see FIG. 4). The elastomeric coating 16 is also formed on the non-pressing surface 18 of the pressing halves 10. One pressing half 10 is provided with a logo 20 on the pressing surface 14 for pressing the rod. (In some cases, both press halves will be provided with a logo.) This logo 20 may also be coated with an elastomeric coating 16.

«» T t # # # t t t t t t t t t t t t t t t t t t t t t t t

The press 12 comprises a metal edge 30 that extends inwardly from the upper periphery of the detergent bar cavity 32. As seen in FIG. 4, the edge 30 covers the upper edge of a generally vertically rising, elastomeric coating

Preferably, the surface 34 of the metal edge 30 that faces the cavity 32 is at least in alignment with the surface 36 of the elastomeric coating 16, which likewise faces the cavity 32. More preferably, the surface 34 of the metal edge 30 extends slightly beyond the surface 36 of the elastomeric coating 16.

Using the edge or flange of the present invention, the press is designed such that the soft elastomer near the cutting edge is not damaged when the press is cut into soap.

This is achieved by covering this soft elastomer near the pressing edge with a rigid and thicker material. This cover 15 o s.

it acts similar to an umbrella around the pressing edge and slightly overlaps the soft elastomer, preferably by about 0.001 to 0.015 (about 0.0254 mm to 0.381 mm). This protects the soft material from excessive shear and tensile forces that could speed up the damage of the soft material and make the press unusable.

Although the edge of the stress relief press has been described to be metallic, this generally depends on the material from which the press is made. Typically, the edge will be of the same material as the press. However, the edge will usually be relatively stiff to protect the elastomer.

The present invention can be used with a conventional press apparatus, such as the Binacchi USN 100.

· * ♦ · ftft ftft ft ftft ftftftft · · ** ** ftftftft ftft • I! 1 * 1 · · ft ft ft ft ft ft ft ftft ftft

Preferably, the edge is undercut, which provides greater mechanical strength.

EXAMPLE

A number of carbon steel press halves were produced, which were electrospark machined for a number of surface roughness values (Ra), degreased with acetone, treated with a primer and then coated with a plurality of elastomeric materials.

A number of brass press halves were also used in the examples. The press halves were similarly degreased with acetone, treated with a primer and then coated.

Elastomeric coatings are made of polyurethane. Polyurethane is ready starting with:

(a) Andur 80-5AP polyether based on an isocyanate-terminated liquid prepolymer. This material is supplied by: Anderson Development Co., 1415 E Michigan St, Adrian, MI 49221-3499;

and is cured using

b) Voronal 234 630 - Triol hardeners available from: Dow Chemical Co., 2040 Dow Center, Midland, MI 48674

The bar compositions used in the examples are as follows:

17 • ft ♦♦ 9 9 9 • · · · · • »· · Ftft ·· ftft ft ftft and ·· ftft a • t ·· • ft ftft ·· • ftftft · • · · · · ft ·· ft ··· ··· • ftft • ft ·· · ♦ Composition 0, 0 weight anhydrous tallow soap 52.3 waterless coconut soap 29.9 5 coconut fatty acid 5.2 water and minor admixtures to 100 Composition B O O weight 10 sodium alkyl isethionate 27,00 cocoamidopropylbetain 5.00 polyethylene glycol, molar mass 33, 12 fatty acid 11.00 15 Dec sodium stearate 5.00 water and minor admixtures to 100 Composition C O p weight 20 May sodium alkyl isethionate 49, 78 soap 82/18 8.31 sodium stearate 2, 98 alkylbenzenesulfonate 2.02 25 stearic acid 20, 15 coconut fatty acid 3, 08 isethionate sodium 4, 68 water and minor admixtures to 100

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

0 »* 9 · 0 · 00 ·

000 «00

0 «0 0 ·

The presses comprise metal edges as illustrated in FIG. 4. Metal edges have been found to relieve stress on the upper periphery of the cavity during compression and result in a longer usable coating life.

It should be understood, of course, that the specific forms of the present invention which have been illustrated and described herein are intended to be representative only and may be subject to certain changes without departing from the spirit or scope of the invention. The content of the following appended claims is decisive for determining the full scope of the present invention.

Claims (9)

A substrate pressing apparatus comprising a press having at least one pressing surface for pressing a substrate covered with an elastomeric coating, said pressing surface for pressing a substrate having a stiffness greater than the stiffness of the elastomeric coating, wherein the edge forms a flange, which lies in alignment or extends beyond the leading edge of the elastomeric coating of the press. Device according to claim 1, characterized in that the edge is metal. Device according to claim 1 or 2, characterized in that the edge is formed of a press material. The device of claim 1, 2 or 3, characterized in that the edge comprises an elastomeric coating thinner than the press coating. A device according to any one of claims 1 to 5 4, characterized in that the elastomeric coating is selected from elastomers, rubbers, thermoplastic elastomers and copolymers and mixtures thereof. Apparatus according to any one of the preceding claims, characterized in that the press comprises a rigid material selected from metals and their alloys, thermoplastics thermosets, hard cast polyurethanes, ceramic materials, composite materials and laminates. 0 * 0 «00 0 0 0 0 0 0 0 0 0 • 0 0 0 · · 4 0 0 00 00 0 0 0 0 · 0 0 «0 0« 00 0 0 0 * 00 A method for forming an elastomeric coating on a device as defined in any preceding claim, comprising the steps of: i. pretreating the device with chemical and / or mechanical means to form a bonding surface for the elastomeric coating; and ii. applying an elastomeric coating to the device. 8. A method for molding a detergent bar comprising the steps of: i. forming a device as defined in any one of claims 1 to 6; ii. supplying the detergent bar composition to the press; iii. compressing the mixture in a press to form a molded bar; and iv. releasing the rod from the press. Use of a device as defined in any one of claims 1 to 6 for molding a detergent bar.