WO2004078448A1

WO2004078448A1 - Method for producing a portion package made of a thermoplastic material in a casting mold made of a silicone elastomer obtained by a platinum cross-linking process

Info

Publication number: WO2004078448A1
Application number: PCT/EP2004/001888
Authority: WO
Inventors: Gerald Petry; Steve Hatfield
Original assignee: Henkel Kommanditgesellschaft Auf Aktien
Priority date: 2003-03-05
Filing date: 2004-02-26
Publication date: 2004-09-16
Also published as: EP1599325A1; DE10361988A1; CN1756635A

Abstract

The invention relates to a method for producing a portion package made of a thermoplastic material during which in a first method step: a) the thermoplastic material, while in the free-flowing state, is poured into a casting mold; b) the thermoplastic material poured into the casting mold is permitted to solidify and in a second method step; c) the solidified thermoplastic material is packed, whereby; d) a shaped body, which is made of at least one silicone elastomer obtained by a platinum cross-linking process, is selected for use as the casting mold. The method is characterized in that a free-flowing thermoplastic material, particularly a hot-melt-type adhesive is poured into the casting mold at temperatures ranging from 40 °C to 280 °C and in a second method step, can be removed after solidification from the casting mold without leaving any residues and can be packed. The emptied casting mold can be reused for filling once again.

Description

METHOD FOR PRODUCING A PORTION PACK OF A THERMOPLASTIC MATERIAL IN A CAST MOLD FROM A PLATIN CROSSLINKING PROCESS

WINNED SILICONE ELASTOMERS

The invention relates to a method for producing a portion package of a thermoplastic material, the portion package of the thermoplastic material itself and the use of a suitable casting mold for producing the portion package of the thermoplastic material.

In the context of the present invention, a thermoplastic material is understood to mean a material which is solid at room temperature, can be liquefied or made to flow by heating and solidifies again on cooling, the process being able to be repeated several times. Solid means that the material has a crystalline to waxy or gummy consistency at room temperature (e.g. 20-22 ° C). The invention relates in particular to thermoplastic materials from the group of thermoplastic adhesives, coating or sealing agents.

The group of thermoplastic adhesives includes, for example, hot melt adhesives.

Hotmelt adhesives are adhesives that are applied as a melt to the substrates to be bonded and that, after being joined, harden when they cool down.

There are both pressure-sensitive and block-resistant, granulable hot melt adhesive systems on the market.

Hotmelt PSAs in solvent-free form are permanently sticky at 20 ° C, remain adhesive and adhere immediately to almost all substrates with low substrate specificity and light pressure. Adhesive composites made with hotmelt PSAs can usually be removed without destroying the bonded substrates. Reactive hot melt adhesives are hot melt adhesives with reactive groups, for example one or two component hot melt adhesives based on polyurethanes with free isocyanate groups.

Methods for packaging thermoplastic materials, in particular from the group of adhesives, are known.

Some processes use direct filling in film tubes made of meltable plastic film, which can be melted and applied together with the adhesive. The plastic film thus becomes part of the adhesive, the additional work step of removing the adhesive before use is omitted and the packaging film does not have to be disposed of separately. Processes of this type are disclosed, for example, for strand-packed hotmelt PSAs in DE 3138222 and DE 3234 065, for granulated hotmelt PSAs in WO 00/34129 and for block-type hotmelt adhesives in DE 3625358.

Portions of adhesive in the form of so-called co-extruded adhesive pillows, packed in a film which can be melted together with the adhesive, are known, for example, from WO 97/00813. Adhesive pillows packaged in this way are suitable for hotmelt PSAs with softening points below 120 ° C.

Another form of film packaging is disclosed in EP 0 521 661 A1. A method is described in which essentially a thermoplastic material in molten form is filled into a casting mold lined with foil. The film forms an adhesive-free coating on the surface of the solidified thermoplastic material. A disadvantage of film-wrapped thermoplastic materials that are melted together with the film is often the floating of solid film residues on the surface of the thermoplastic material melt. This is caused, for example, by the difference in density between plastic film and thermoplastic material, a wide melting range of the plastic film and / or by air which is enclosed in the film. Film residues that are not completely melted can cause clogging of the nozzles of application devices and thus production problems.

The above-mentioned processes are preferably used for the continuous packaging of thermoplastic materials in large-scale production and are carried out without a large amount of personnel. However, high investment costs are associated with the processes of this type.

Smaller production quantities (small series) from discontinuous processes and very highly viscous thermoplastic materials are still mostly filled in containers made of metal, paper or rigid plastic, for example metal drums, boxes, cardboard boxes or plastic trays.

If the thermoplastic materials are sticky materials, the areas of the packaging material that can come into direct contact with the sticky thermoplastic material are generally additionally provided with an anti-adhesive layer.

EP 0496626 A1 discloses a container containing a solid hot-melt material, the solid hot-melt material being separated from the inner surfaces of the container by an anti-adhesive coating. The anti-adhesive coating can consist, for example, of an emulsion, dispersion, wax or powder. The anti-adhesive coating makes it easier to remove the solid hot-melt material from the container. A disadvantage of this coating is that a complete homogeneous coating of the inner surfaces is frequently not achieved, and residues of the hot-melt material remain on the inner surface. If the container is to be used again for filling, the coating of the inner surface must be renewed after the hot-melt material has been removed, since part of the coating usually remains on the hot-melt material.

US 5,992,130 discloses a rigid container for packaging and transporting a reactive hot-melt adhesive composition that crosslinks in the presence of moisture. The outer wall of the container is made of a moisture-resistant material and the inner wall is coated with a material that does not stick to the adhesive. The coating consists, for example, of polymers based on silicone or fluorine components and is applied starting from a resin or varnish. Before the adhesive composition is removed, the container must be heated in a heating device. The container is not suitable for reuse. Since it is made up of different materials, these have to be separated before recycling.

A general disadvantage of the prior art described above is that after the sticky thermoplastic material has been removed from the container, packaging waste arises which has to be disposed of.

Frequently, an at least direct reuse of these containers is also not possible, since the anti-adhesive layer is usually damaged during the filling and unpacking of the thermoplastic material. As a result, more and more manufacturers are beginning to use reusable containers in which the melt of the thermoplastic material is filled to cool. So that the solid thermoplastic material can be brought back out of the container, suitable moldings are either with a separating layer, for. B. wax, siliconized paper or coated with a film or lined. After cooling, the thermoplastic material can, for example, be wrapped in foil or coated with an anti-adhesive layer.

DE 4205919 A1 describes a method in which a shaped body with possibly movable end and side walls rests on a conveyor belt made of thermally conductive material and a packaging material in the form of a film is applied to this shaped body. Liquefied adhesive is introduced onto the packaging material and into the molded body, and the area not yet enclosed by the packaging material is covered with packaging material.

The adhesive packaged in this way is removed from the molded body and can then be stacked and transported. In a preferred embodiment of the invention, the shaped body is designed in the manner of an armored chain and can be used repeatedly in the context of continuous production.

However, a particular problem with this process is a high filling temperature of mostly highly viscous adhesives, which can be up to approx. 200 ° C. In this case, the film introduced into the molded body must be cooled intensively. Even the rapid dissipation of heat from metal moldings alone is not enough to protect the film from damage caused by the hot filled thermoplastic material.

The object of the present invention was to provide an environmentally friendly method for packaging thermoplastic materials which overcomes the disadvantages of the prior art. There is a need, in particular, for a method which enables thermoplastic materials to be filled directly into a packaging material at temperatures up to 280 ° C. without causing damage to the packaging material. Another object of the invention was to provide a method for packaging sticky thermoplastic materials.

Another object of the invention was to provide a method which enables the filling and packaging of thermoplastic materials which are used in direct or indirect contact with food.

The solution to the problem according to the invention can be found in the patent claims.

It essentially consists in a process for producing a portion pack of a thermoplastic material by a) filling the thermoplastic material in a flowable state into a casting mold in a first process step, b) allowing the filled thermoplastic material to solidify in the casting mold and in a second process step c) the solidified thermoplastic material is packaged, wherein d) a mold is selected as the casting mold, which is composed of at least one silicone elastomer, which is obtained by a platinum crosslinking process.

Compared to known processes, the process according to the invention has the particular advantage that the flowable thermoplastic material at temperatures from 40 ° C to 280 ° C, preferably from 60 ° C to 260 ° C and particularly preferably from 80 ° C to 240 ° C. The mold can be filled and cooled in it for solidification without the surface of the silicone elastomer, which is in direct contact with the hot thermoplastic material, being damaged during filling. The filling takes place directly, for example after the production of the thermoplastic material, if it is still flowable, or indirectly, that is, for example, from a storage container. The storage container is permanently heated so that the thermoplastic material contained therein is flowable or the storage container is heated if necessary in order to make the thermoplastic material contained therein flowable. The cooling of a filled amount of painter of 2 kg takes approx. 2-3 hours in air and approx. 1.5 hours in a water bath, depending on the filling temperature.

In a second process stage, the solidified thermoplastic material is packaged.

This can be done continuously or discontinuously by the solidified thermoplastic material remaining in the casting mold and being packed together with the latter in a container made of paper, cardboard, metal or plastic. For example, the container is a box or a cardboard box. In a further embodiment, the casting mold is closed with a lid, the lid preferably consisting predominantly of the same material as the casting mold. The lid is either already attached to the casting mold or is placed in a separate step after the thermoplastic material has been filled to close the casting mold. The lid is preferably designed in such a way that it protects the contents, such as preferably a reactive hot melt adhesive, from atmospheric moisture.

In a preferred embodiment, the thermoplastic material is separated from the casting mold in the second process step before packaging. The solidified thermoplastic material can be removed very easily from the casting mold without the casting mold being damaged and without the casting mold having to be equipped with a separating layer. For this purpose, the casting mold has, on the one hand, sufficient shape stability when filling in the liquid thermoplastic material and, on the other hand, a sufficiently high elasticity which, for example, enables the casting mold to be pulled off a cooled block of the thermoplastic material. The elasticity of the casting mold results from the material used - the casting mold is made up of at least one silicone elastomer. Elastomers are wide-mesh, cross-linked, high-molecular polymers with rubber-elastic behavior, which can be repeatedly stretched at least twice their length at room temperature and, once the constraint required for the stretching has been removed, immediately return to their original length. The elasticity is described by the elastic modulus of elasticity "E", which is the ratio of the tensile stress (force per cross-sectional area) to the longitudinal expansion.

Crosslinking is generally achieved by vulcanizing natural or synthetic rubbers.

Sufficient dimensional stability is brought about by the construction by inserting stiffening elements, for example in the form of webs, in the manufacturing and shaping process.

The casting mold is preferably produced from silicone rubbers using the casting method. These are masses which can be converted into the rubber-elastic state and which, as base polymers, contain polydiorganosiloxanes which have groups accessible to crosslinking reactions. As such, for example, H atoms, OH or vinyl groups are suitable, which are located at the chain ends or can also be incorporated in the chain.

Hot or cold vulcanizing silicone rubbers (high / room temperature vulcanizing = HTV / RTV) are used to manufacture the casting mold.

The HTV silicone rubbers are vulcanized in the presence of crosslinking catalysts, usually organic peroxide, at temperatures> 100 ° C., preferably 150 to 160 ° C. Precious metal compounds are also used as crosslinking catalysts. Platinum is generally used as the precious metal compound. For the injection molding process, liquid silicone rubber components, usually two liquid silicone rubbers (LSR = liquid silicone rubbers) are vulcanized via addition crosslinking.

The cold-curing or RTV silicone rubber compounds can be differentiated into one and two-component systems. Polymerize or crosslink the former by condensation of SiOH groups with the formation of Si-O bonds, for example under the influence of atmospheric humidity.

In the case of two-component rubbers (RTV-2), z. B. mixtures of silicic acid esters and tin-organic compounds are used, the crosslinking reaction being the formation of an Si-O-Si bridge from “Si-OR” and “Si-OH” groups by elimination of alcohol. Platinum is preferably used and is known from the prior art as a crosslinking catalyst, in particular when the crosslinking is carried out by polyaddition and not by polycondensation.

The molded body is preferably produced from high molecular weight polymethylsiloxanes.

Silicone rubbers and casting processes for the production of moldings from silicone elastomers are known from FR 9609004 A1. Usable silicone elastomers are also described in US 2001/0043977.

The casting mold is particularly preferably constructed from a silicone elastomer which is obtained by a platinum crosslinking process. Such crosslinked silicone elastomers have little, if any, contamination from by-products and are therefore suitable for the food sector. It has surprisingly been found that these silicones are rubber-elastic over a wide temperature range and have no color changes at temperatures up to 280 ° C.

The silicones obtained by a platinum crosslinking process are particularly preferably hot-crosslinked (HTV) silicones. In particular, they are methyl vinyl polysiloxanes. Such siloxanes are described in EP 0 992 195 B1 and in EP 0 519 372 B1. The at least one silicone elastomer is antiadhesive to the thermoplastic material: A sticky thermoplastic material, in particular a hot melt pressure sensitive adhesive, which is filled into the casting mold, which is made up of at least one silicone elastomer, which is obtained by a platinum crosslinking process, can after Cool the mold can be removed without the remnants of the sticky thermoplastic material sticking to the wall. The casting mold remains rubber-elastic in a temperature range from -40 ° C to 280 ° C.

The casting mold can be designed in different geometries, for example in the form of a plate with mold cavities, as in DE 19922439 A1 or in the form of a bowl-shaped container, as described in US 2002/0171027 A1.

A rectangular shape is preferred, the geometry is known from DE 4205919.

In a preferred embodiment, the filling space of the casting mold has a base area of 8 to 12 cm × 20 to 26 cm and a height of 6 to 8 cm.

The present invention also relates to the use of a casting mold, produced on the basis of at least one silicone elastomer, which is obtained by a platinum crosslinking process, for packaging thermoplastic materials.

In a particular embodiment, a thermoplastic material from the group of thermoplastic adhesives, coating or sealing agents is used as the thermoplastic material in the method according to the invention. The thermoplastic material is preferably a thermoplastic hot melt adhesive, in particular a thermoplastic hot melt pressure sensitive adhesive.

The invention therefore also relates to a portion pack consisting essentially of a) a thermoplastic adhesive, coating or sealing agent and b) a casting mold made of at least one silicone elastomer, which is obtained by a platinum crosslinking process.

Suitable hot melt adhesives which can be packaged by the process according to the invention are described in EP 0469564 B1 on ropes 4, line 44 to page 8, line 48.

After filling and cooling, reactive hot melt adhesives are preferably packed together with the casting mold in a further container which protects the reactive adhesive from moisture or electromagnetic radiation (daylight, UV light) protects. This can be, for example, a tightly closable metal box or metal box.

The cooled reactive hot melt adhesive can also be removed from the mold and packed in a foil bag made of aluminum / polyethylene (PE). The foil pouch is sealed with the inner PE foil. The aluminum foil on the outside protects the contents of the package from moisture and electromagnetic radiation.

A hotmelt pressure-sensitive adhesive filled by the process according to the invention can be removed from the casting mold again without residue after cooling. It is not necessary to equip the casting mold with aids, for example separating layers made of siliconized paper, plastic film or anti-adhesive coatings.

The hotmelt pressure-sensitive adhesive removed from the casting mold is optionally coated with an anti-adhesive coating for further assembly and packaging, for example with a wax or with a polymer. Coatings of this type are disclosed, for example, in DE 3327289. From WO 84/03457 and WO 84/03468 it is known to provide blocks of hot melt adhesives with a powdery release agent.

The adhesive removed from the casting mold, in particular a hotmelt PSA, can also be packaged in a known manner in plastic film, which if necessary is melted together with the adhesive and applied to the substrate to be bonded. Films suitable for the packaging of hotmelt PSAs can be found in DE 4205191 A1 on page 2, line 46 to page 3, line 9.

In a special embodiment of the invention, the hotmelt PSA is filled into the casting mold, cooled, packaged, for example into a cardboard box or a cardboard box, the casting molds filled with adhesive also being stackable on top of one another, removed from the end user for the application and emptied Casting mold returned to the manufacturer or the process for refilling. The method according to the invention is particularly suitable for filling very highly viscous thermoplastic materials. Highly viscous thermoplastic materials are understood to mean materials that have a viscosity of 5000 mPas to 100,000 mPas at a temperature of 180 ° C., measured according to Brookfield, spindle 27.

The process is also particularly suitable for small series and in production facilities where an investment in a continuous system does not appear to be profitable and which therefore give priority to the process of discontinuous packaging of thermoplastic materials.

The process saves expensive, specially anti-adhesive packaging, such as siliconized cardboard boxes.

The invention will now be explained in detail on the basis of examples:

EXAMPLES

example 1

The hot melt adhesive Technomelt Q 8718 (manufacturer: Henkel KGaA; composition about 45% SIS / SBS, 50% terpene resin, 5% mineral oil) with a viscosity of 45,000 mPas at 180 ° C (measured according to Brookfield, spindle 27.5) was used for a melt temperature of 180 ° C filled directly into the mold. After cooling, the adhesive could be removed from the molded article without leaving any residue.

Example 2

The hot melt adhesive Technomelt 5418 (manufacturer Henkel KGaA; composition about 50% polyolefin, 30% KW resin, 20% mineral oil) with a viscosity of 1600 mPas at 150 ° C (measured according to Brookfield, spindle 27.5) was at a temperature of The melt at 120 ° C is filled directly into the mold. After cooling, the adhesive could be removed from the mold without residue.

In the examples, the mold used in each case could be filled and emptied 20 times without any negative influence on the quality (appearance, surface quality, etc.) being observed.

In both examples, a rectangular container made of a silicone elastomer with the dimensions 24.0 × 10.5 × 7 cm was used as the casting mold. It is a molded body from the "Milleforme" series, manufacturer: Pavoni Italia S.p.A, 24040 Suisio (BG), Italia.

Claims

claims

1. A process for producing a portion pack of a thermoplastic material by, in a first process step: a) filling the thermoplastic material in a flowable state into a casting mold, b) allowing the filled thermoplastic material to solidify in the casting mold and in a second process step c) that packaged solidified thermoplastic material, wherein d) a mold is selected as the casting mold, which is composed of at least one silicone elastomer, which is obtained by a platinum crosslinking process.

2. The method according to claim 1, characterized in that the flowable thermoplastic material is filled at temperatures from 40 ° C to 280 ° C, preferably from 60 ° C to 260 ° C and particularly preferably from 80 ° C to 240 ° C.

3. The method according to claim 1 or 2, characterized in that separating the solidified thermoplastic material in the second process step before packaging from the mold.

4. The method according to any one of claims 1 to 3, characterized in that the casting mold is made of hot or cold vulcanizing silicone rubbers, in particular of methyl vinyl polysiloxanes.

5. The method according to any one of claims 1 to 4, characterized in that the casting mold is rubber-elastic in a temperature range from -40 ° C to 280 ° C.

6. The method according to any one of claims 1 to 5, characterized in that the at least one silicone elastomer is anti-adhesive to the thermoplastic material.

7. The method according to any one of claims 1 to 6, characterized in that the thermoplastic material used is a thermoplastic material from the group of thermoplastic adhesives, coating or sealing agents.

8. The method according to claim 7, characterized in that a hot melt pressure sensitive adhesive or reactive adhesive is used as the thermoplastic material.

9. portion package consisting essentially of a) a thermoplastic adhesive, coating or sealing agent and b) a casting mold made of at least one silicone elastomer, which is obtained by a platinum crosslinking process.