US20210054550A1

US20210054550A1 - Method of making a spun-bonded nonwoven for packaging

Info

Publication number: US20210054550A1
Application number: US17/092,494
Authority: US
Inventors: Claudio Cinquemani; Alexander Klein
Original assignee: Individual
Current assignee: Individual
Priority date: 2016-03-10
Filing date: 2020-11-09
Publication date: 2021-02-25
Also published as: EP3480352B1; EP3216905A1; CN107177935B; CN107177935A; JOP20200179A1; EP3480352A1; MX2020009501A; EP3216905B1; DK3216905T3; MX2017003093A; US20180002851A1; DK3480352T3; JO3652B1

Abstract

A package has walls formed of a weldable spun-bonded nonwoven and having welded wall regions. The spun-bonded nonwoven has continuous filaments of a thermoplastic plastic each with a thermoplastic core surrounded by a thermoplastic sheath. The sheaths of the continuous multicomponent filaments of both components contain at least 3 wt % of at least one filler so that weldability of the spun-bonded nonwoven is improved by reducing a welding temperature in thermal welding of the spun-bonded nonwoven. A first plastic component forming the sheaths of the multicomponent filaments has the same or a lower melting point than a second plastic component forming the cores of the filaments.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This is a divisional application of copending application Ser. No. 15/450,986 filed 06 Mar. 2017 with a claim to the priority of EP 16 159 620.2 filed 10 Mar. 2016.

FIELD OF THE INVENTION

The invention relates to a weldable spun-bonded nonwoven, in particular a weldable packaging spun-bonded nonwoven as a component of packaging or packaging bags, where the spun-bonded nonwoven has endless filaments that are preferably of a thermoplastic plastic. The invention also relates to a method of making a weldable spun-bonded nonwoven or packaging spun-bonded nonwoven. The invention also relates to a packaging, in particular a packaging bag, having at least one weldable spun-bonded nonwoven or packaging spun-bonded nonwoven.

BACKGROUND OF THE INVENTION

In the context of the invention, spun-bonded nonwovens of endless filaments are used. As is known, endless filaments differ from staple fibers due to their quasi-endless length, staple fibers having much shorter lengths of for example 10 mm to 60 mm. It lies within the scope of the invention for a spun-bonded nonwoven or packaging spun-bonded nonwoven according to the invention to be made in the form of a spun-bonded nonwoven by a spun-bonding method.
Weldable spun-bonded nonwovens or packaging spun-bonded nonwovens for package walls, particularly of bag-shaped packages, are known from everyday use in a variety of embodiments. In this connection, the spun-bonded nonwovens can be used separately as package walls or as a component of a laminate for the package walls. To this end, laminates of spun-bonded nonwovens and plastic films are known. Packaging walls of spun-bonded nonwovens or containing spun-bonded nonwovens are particularly also known for bag-shaped packages for bulk materials with filling weights of 25 to 500 kg. In this connection, spun-bonded nonwovens are also used for cement bags.
The production of a bag-shaped package based on a spun-bonded nonwoven is carried out as follows. First, a so-called “tube” is made from the spun-bonded nonwoven and then the opposing side edges of the nonwoven web are bonded to each other, in particular welded to each other. Then the tube is cut to the desired bag length, the resulting product is folded and crimped and then a bottom sheet functioning as a bottom wall and a cover sheet functioning as a top wall are set in place and then welded to the bag body.
The bag-shaped packages that have been known up to this point and have been made in the above-explained way, often leave much to be desired from a strength standpoint. In free fall filling of packaging bags, in particular cement bags, from heights of 2 m, for example, the packaging bags tear at least after several drop tests. As a rule, the tearing occurs in the region of the welds or seals of packaging bags. For this reason alone, the known packaging bags, such as cement bags, are in need of improvement.
The spun-bonded nonwovens used for producing the known packaging bags, however, also leave much to be desired with regard to their processability. This particularly relates to the weldability or sealability of spun-bonded nonwovens when producing a package or packaging bag. Normally, relatively high processing temperatures and welding temperatures are required in this connection, which is initially associated with an undesirably high energy expenditure. Furthermore, high processing or welding temperatures cause damage to regions of the nonwoven material and for this reason alone, result in quality losses. Aside from this, the strength and durability of the welding seams leave much to be desired. Furthermore, normally, the known packaging bags made of spun-bonded nonwovens absolutely require a coating with an additional material so that the cost and consumption of raw material is undesirably high. As a result, there is room for improvement.

OBJECT OF THE INVENTION

Correspondingly, the object of invention is to provide a weldable spun-bonded nonwoven or packaging spun-bonded nonwoven that on the one hand, can be processed or welded in a relatively easy, uncomplicated way and on the other hand also meets all requirements from a strength and stability standpoint in the finished state.
Another object of the invention is to provide a method of making such a weldable spun-bonded nonwoven or packaging spun-bonded nonwoven.
A further object of the invention is to provide a corresponding package, in particular a packaging bag, having at least one weldable spun-bonded nonwoven.

SUMMARY OF THE INVENTION

To attain these objects, the invention teaches a weldable spun-bonded nonwoven, in particular a weldable packaging spun-bonded nonwoven, as a component of packages or packaging bags, the spun-bonded nonwoven having endless filaments preferably of a thermoplastic plastic; the endless filaments have 3 wt %, preferably at least 4 wt % of at least one filler, in particular to improve the weldability of the spun-bonded nonwoven and preferably to reduce the welding temperature in the thermal welding of the spun-bonded nonwoven.
Another subject of the invention is a weldable spun-bonded nonwoven, in particular a weldable packaging spun-bonded nonwoven, as a component of packages or packaging bags; the spun-bonded nonwoven has endless filaments that are preferably of a thermoplastic plastic, the endless filaments being of multicomponent filaments, particularly in the form of bicomponent filaments, and at least one component of the multicomponent filaments or bicomponent filaments containing at least 3 wt %, preferably at least 4 wt %, of at least one filler, in particular to improve the weldability of the spun-bonded nonwoven and preferably to reduce the welding temperature in the thermal welding of the spun-bonded nonwoven.
According to a particularly preferred embodiment of the invention, the endless filaments or at least one component of the endless filaments of the weldable spun-bonded nonwoven, in particular the weldable packaging spun-bonded nonwoven, contain 4 to 25 wt % of the filler, preferably 5 to 20 wt %, and very preferably 6 to 15 wt % of the filler. The individual portions of the components of the endless filaments, in particular of the plastic component or plastic components of the endless filaments, add up to a total of 100 wt % when added to the portion of the filler.
It lies within the scope of the invention that the filler is at least one organic filler, preferably at least one metal salt and preferably at least one alkaline earth metal salt. In a particularly recommended embodiment of the invention the filler is a calcium salt and quite particularly preferably, the filler is calcium carbonate. In this case, calcium carbonate has proven itself to be particularly valuable as a filler for the weldable spun-bonded nonwoven according to the invention for attaining the object. Basically, it is also possible to use calcium sulfate as a filler.
According to one variant of the invention, the monocomponent filaments are endless filaments for a weldable spun-bonded nonwoven according to the invention. In this case, the monocomponent filaments of the weldable spun-bonded nonwoven, as recommended, contain at least 5 wt % filler or calcium carbonate, preferably at least 7 wt %, suitably 7 to 25 wt %, preferably 8 to 22 wt %, and very preferably 10 to 20 wt % of filler or calcium carbonate as a filler. It lies within the scope of the invention for the filler to be homogeneously or at least essentially homogeneously distributed in the endless filaments or according to a recommended embodiment, for it to be present at least on the surface of the endless filaments or essentially on the surface of the endless filaments.
A particularly well proven embodiment of the invention is characterized in that in that the endless filaments of the weldable spun-bonded nonwoven are multicomponent filaments, in particular as bicomponent filaments. Preferably, the filler is contained in a plastic component present on the outer surface of the multicomponent filaments or bicomponent filaments. It is advisable for a first plastic component present on the surface of the multicomponent filaments or bicomponent filaments to have the same melting point or preferably a lower melting point than at least one second plastic component of the multicomponent filaments or bicomponent filaments and for the filler to be contained at least in the first plastic component that has the same or a lower melting point, or is contained essentially or exclusively in the first plastic component that has the same or a lower melting point.
According to a preferred embodiment of the invention, the multicomponent filaments or the bicomponent filaments of the weldable spun-bonded nonwoven have a core-sheath configuration. Advantageously, the filler in the sheath of these multicomponent filaments or bicomponent filaments. According to a very preferred embodiment of the invention, the same- or lower-melting-point plastic component of the multicomponent filaments or bicomponent filaments of the weldable spun-bonded nonwoven is the sheath and the filler is then at least contained in this sheath or is essentially or exclusively contained in the sheath.
Preferably polyolefins or other thermoplastic plastics are used as the plastic component or plastic components for the endless filaments of the spun-bonded nonwovens according to the invention. In this connection, it is also within the scope of the invention that blends of the above-mentioned plastics are used as the plastic component or plastic components.
According to one embodiment of the invention, the weldable spun-bonded nonwoven is a spun-bonded nonwoven of bicomponent filaments and in fact, of bicomponent filaments with a core/sheath configuration. The same- or lower-melting-point component is present in the sheath and is composed, for example, of a polypropylene copolymer or essentially of a polypropylene copolymer. In this case, it is necessary to take into account that it is within the scope of the invention for the filler, preferably in the above-specified proportions, to be contained in the sheath. The same- or higher-melting-point component is present in the core of the bicomponent filaments and is composed, for example of polypropylene or essentially of polypropylene. According to another variant, a polyethylene can be used as the lower-melting-point component or as the sheath of the bicomponent filaments or multicomponent filaments and for a polypropylene to be used as the higher-melting-point component or core.
According to a recommended embodiment, at least one plastic component of the bicomponent filaments or multicomponent filaments of the spun-bonded nonwoven according to the invention are of a polyolefin or essentially of a polyolefin. A well-proven embodiment is characterized in that in that both or all of the plastic components of the bicomponent filaments or multicomponent filaments of the weldable spun-bonded nonwoven according to the invention are of polyolefins or essentially of polyolefins. Basically, however, it is also possible to sue other thermoplastic plastics or blends thereof for the components.
It has already been stated that according to a particularly preferred embodiment of the invention, the filler is present in a plastic component of the bicomponent filaments or multicomponent filaments that is on the surface of the filaments. Preferably, this is the lower-melting-point plastic component in the filament and very preferably, the lower-melting-point component is the sheath of a core/sheath configuration of the bicomponent filaments or multicomponent filaments. In a recommended embodiment, 5 to 25 wt %, preferably 7.5 to 22.5 wt %, and very preferably 10 to 20 wt % of the filler, in particular of calcium carbonate, is contained in the, preferably lower-melting-point, plastic component on the surface of the filaments, preferably in lower-melting-point plastic component in the sheath of the bicomponent filaments or multicomponent filaments. Advantageously, the filler or the calcium carbonate in this case is distributed homogeneously or essentially homogeneously in the plastic component or on the outer surface or essentially on the outer surface of the plastic component.
It is within the scope of the invention that in the bicomponent filaments or multicomponent filaments of a spun-bonded nonwoven according to the invention, the mass ratio of the first, preferably lower-melting-point, plastic component, in particular the sheath, to the second, preferably higher-melting-point, plastic component, in particular the core, to be 10:90 to 35:65, preferably 15:85 to 35:65, preferably 20:80 to 50:50, and preferably 25:75 to 45:55. In spun-bonded nonwovens and in package wall regions containing a spun-bonded nonwoven according to the invention in which or at which a welding or sealing does not take place, according to a well-proven embodiment, the mass ratio of the first, preferably lower-melting-point, plastic component, in particular the sheath, to the second, preferably higher-melting-point, component, in particular the core, is 20:80 to 30:70, preferably 20:80 to 25:75. By contrast, in spun-bonded nonwovens and in package wall regions in which or at which a welding or sealing does take place, the mass ratio of the first preferably lower-melting-point plastic component, in particular the sheath, to the second, preferably higher-melting-point component, in particular the core, is 35:65 to 50:50, preferably 40:60 to 45:55. It is within the scope of the invention that in multicomponent filaments or bicomponent filaments of spun-bonded nonwovens and spun-bonded nonwoven regions that are provided for a welding, the ratio of the sheath to the core is higher than in multicomponent filaments or bicomponent filaments of spun-bonded nonwovens and spun-bonded nonwoven regions that are not provided for a welding.
A particularly preferable embodiment of the invention is characterized in that the weldable spun-bonded nonwoven is a calendered spun-bonded nonwoven. In a recommended embodiment, one surface of this spun-bonded nonwoven is pressed smooth and one surface is calendered with a profile. It is also possible, however, for both surfaces of the spun-bonded nonwoven to be calendered smooth. It is within the scope of the invention for the ratio of the strength or tensile strength of the weldable spun-bonded nonwoven in the machine direction (MD) to the strength or tensile strength of the spun-bonded nonwoven crosswise to the machine direction (CD) to be either equal to 1 or greater than 1, preferably greater than 1.1 and particularly preferably greater than 1.2. In this context, “machine direction” particularly means the advancing direction of the deposited spun-bonded nonwoven on a lay or deposition apparatus.
It is also within the scope of the invention that a weldable spun-bonded nonwoven according to the invention is made according to the following method: first, endless filaments are spun by a spinneret and them these filaments are cooled in a cooler and then stretched by a stretcher and then deposited on a deposition apparatus to produce the spun-bonded nonwoven. In this regard, it is within the scope of the invention that the weldable spun-bonded nonwoven or weldable packaging spun-bonded nonwoven according to the invention is made as a spun-bonded nonwoven according to a spun-bonding method. According to a particularly preferable embodiment of the invention, the cooler is divided into at least two compartments one above another or one after another in the filament flow direction; from these compartments, cooling air with different convective heat dissipation capacities, in particular cooling air with different temperatures, is introduced into the filament flow chamber. In a recommended embodiment, the cooler has only two such compartments one above another or one after another in the filament flow direction. Preferably, the cooler is connected via an intermediate conduit, in particular via an intermediate conduit that converges in the filament flow direction, to a lower pull-down conduit of the stretcher. The endless filaments are thus conveyed through the cooler, then through the intermediate conduit, and then through pull-down conduit. Finally, the filaments are deposited on a deposition apparatus to produce the spun-bonded nonwoven web or spun-bonded nonwoven that is preferably a mesh deposition belt or as an endlessly revolving mesh deposition belt.
A quite particularly recommended embodiment of the method and apparatus for producing a weldable spun-bonded nonwoven according to the invention is characterized in that the unit of the cooler, intermediate conduit, and subsequent pull-down conduit is a closed unit and aside from the supply of cooling air in the cooler, no other air supply takes place in this closed unit. Also in the context of the production of weldable spun-bonded nonwoven according to the invention, it is preferable that between the pull-down conduit and the deposition apparatus, at least one diffusor is provided, through which the filaments are guided in the filament flow direction toward the deposition apparatus. Advantageously, at least two diffusors, preferably two diffusors are one after another in the filament flow direction between the pull-down conduit and the deposition apparatus. Furthermore, a recommended embodiment of the invention features the fact that in the region of the spinneret or between the spinneret and the cooler, the filaments are conveyed through a monomer aspirator. In this monomer aspirator, the gases that emerge in addition to the filaments in the form of monomers, oligomers, decomposition products, and the like, are removed from the filament forming chamber below the spinneret and from the device.
It is within the scope of the invention that the spun-bonded nonwoven that is deposited using the endless filaments is prehardened or hardened using at least one calender. The calendering in this case can take place in inline or offline fashion. In a recommended embodiment, a calender for such a calendering has an embossing surface of 10 to 90%, preferably 15 to 35%, and very preferably 18 to 30%. According to a preferred embodiment, only one of the two calender rolls has an engraving and preferably the above-specified embossing surface and the opposing associated calender roller is smooth or essentially smooth and without engraving. Preferably, the embossing depth of the calender engraving is 0.1 to 0.8 mm, preferably 0.1 to 0.6 mm, and very preferably 0.2 to 0.4 mm. It is advisable for the number of engraved points of a calender roller or of the calender roller with engraving to be greater than 30/cm²and preferably greater than 40/cm². Particularly preferably, the number of engraved points of a calender roller or of the calender roller with engraving is greater than 45/cm². According to a well-proven embodiment, the engraved points of a calender roller or of the calender roller with engraving are rhomboid when viewed from above. According to another embodiment, the spun-bonded nonwoven according to the invention is pressed by a calender of two calender rollers that each have a smooth surface.
According to another embodiment of the invention, the calendering of a spun-bonded nonwoven according to the invention can also be carried out with a belt calender. One variant is characterized in that the calendering is carried out in two steps or in at least two steps. In this case, the deposited spun-bonded nonwoven is first pressed by a calender or by a standard calender that has an engraving, preferably the above-explained engraving. In a second step, the spun-bonded nonwoven is then pressed with a calender of two calender rollers that each have a smooth surface or is pressed with a belt calender. In the calender of two calender rollers that each have a smooth surface, one surface can be plastic-coated and one surface can be of steel or essentially of steel.
The above-explained calendering of the spun-bonded nonwoven has particularly proven its worth with regard to attaining the inventive object. Spun-bonded nonwovens that have been calendared in the above-explained way and prehardened/hardened can be welded or welded into packages in a particularly advantageous way. The spun-bonded nonwovens made according to the invention can then be easily and simply used to produce packages with additional layers, in particular, can be combined or coated with plastic films and/or melt-blown nonwovens or other spun-bonded nonwovens.
The production of a weldable spun-bonded nonwoven or packaging spun-bonded nonwoven according to the invention according to the above-explained spun-bonding method has particularly proven its worth in the context of the invention. In this way, spun-bonded nonwovens with an optimized lay quality can be obtained and it is thus possible to produce very homogeneous spun-bonded nonwovens. Above all with this preferred method, the deposited spun-bonded nonwoven can be optimized to the extent that the occurrence of thin areas and thick areas in the spun-bonded nonwoven can be significantly reduced in comparison to other known methods. Upon analysis, a plurality of defined spun-bonded nonwoven area sections, for example when inspecting a plurality of spun-bonded nonwoven 2×2 cm²squares, it is possible, in spun-bonded nonwovens made with the spun-bonding method according to the invention to significantly reduce the range between the lightest thin point or the lightest analyzed square and the heaviest thick point or the heaviest analyzed square in comparison to other known production methods. It is thus possible to reduce the range for example of greater than 30 g/m²achieved with other known methods to about 15 g/m²with the method used according to the invention.
In this regard, the invention is based on the discovery that the spun-bonded nonwovens made in the above-described way can be processed into packages, for example packaging bags, in an excellent way and in particular, can be simply and easily welded. In this connection, the invention is also based on the recognition that the welding temperature for welding these spun-bonded nonwovens or packaging spun-bonded nonwovens according to the invention can be significantly lowered in comparison to the spun-bonded nonwovens made according to other known methods. This advantageous reduction of the welding temperature is achieved primarily from use of the filler according to the invention, in particular in the form of calcium carbonate. The weldable spun-bonded nonwovens made according to the preferably used methods advantageously have fewer thin points than other spun-bonded nonwovens and consequently, it is hardly possible for thin points to be damaged during welding. As a result, the spun-bonded nonwovens made according to the invention feature an optimal processability, in particular weldability, and in this regard, they meet the optimal basic requirements for producing packages.
Particularly advantageous properties for the production of packages are possessed by spun-bonded nonwovens in which the ratio of the strength or tensile strength of the spun-bonded nonwoven in the machine direction (MD) to the strength or tensile strength of the spun-bonded nonwoven crosswise to the machine direction (CD) is equal to or greater than 1, preferably greater than 1.1, preferably greater than 1.2, and very preferably greater than 1.25. The above-explained preferred features of the spun-bonded nonwoven according to the invention and of the method of making the spun-bonded nonwoven and the advantages achieved by them are optimally combined with the filler according to the invention and with the filler content according to the invention and the advantages achieved by them.
To solve the technical problem, the invention also teaches a package, in particular a packaging bag, for example a cement bag, preferably for containing pourable and/or free-flowing products such as cement and the like. The package according to the invention has at least one above-explained spun-bonded nonwoven or packaging spun-bonded nonwoven, the spun-bonded nonwoven forms the package wall and/or is a component of the package wall, and sections of the spun-bonded nonwoven or spun-bonded nonwovens in the side wall region and/or at the bottom and/or at the top of the package wall are welded to one another. It is within the scope of the invention that the package has at least one flat bottom wall and/or at least one flat top wall that is welded to the rest of the package wall or to the side wall of the package. It is also within the scope of the invention that the flat top wall and/or the flat bottom wall of the package is/are of at least one spun-bonded nonwoven according to the invention or of one spun-bonded nonwoven according to the invention and preferably the same spun-bonded nonwoven material as the rest of the package wall or as the side wall. If the side wall and the flat top wall and/or the flat bottom wall of the package wall are of spun-bonded nonwovens of multicomponent filaments or bicomponent filaments with a first, lower-melting-point plastic component on the outer surface, then a particularly preferred embodiment of the invention is characterized in that the spun-bonded nonwovens for the flat top wall and/or for the flat bottom wall have a higher percentage of the first, lower-melting-point plastic component than the spun-bonded nonwoven or spun-bonded nonwovens for the side wall of the package wall. Advantageously, the percentage of the first, lower-melting-point plastic component present on the outer surface of the multicomponent- or bicomponent filaments in the spun-bonded nonwovens for the flat top wall and/or for the flat bottom wall is 1.2 times to 3.5 times, preferably 1.5 times to 2.5 times as great as the percentage of the first, lower-melting-point plastic component in the multicomponent- or bicomponent filaments of the spun-bonded nonwoven or spun-bonded nonwovens for the side wall of the package. The melting points of the two plastic components can also be equal or essentially equal.
A particularly preferred embodiment of the invention is characterized in that a spun-bonded nonwoven according to the invention or spun-bonded nonwovens according to the invention is/are component(s) of a package wall laminate and in addition to the spun-bonded nonwoven, the laminate preferably includes at least one film, preferably a plastic film. In this case, both the side wall and the flat top wall and/or the flat bottom wall of the package wall can be formed of such a package wall laminate. A very preferred embodiment of the invention is characterized in that the film or plastic film of the laminate is provided on an inner face of the package wall.
It is within the scope of the invention that the package according to the invention, in particular a packaging bag according to the invention, has one flat top wall that is a component of the package wall and has at least one weldable spun-bonded nonwoven, preferably the one that is specified in greater detail above, and that the spun-bonded nonwoven of the top wall is firmly bonded, in particular welded, to the side wall or to the spun-bonded nonwoven material of the side wall of the package. It is also within the scope of the invention that the spun-bonded nonwoven of the top wall has multicomponent filaments or bicomponent filaments or is composed or essentially of multicomponent filaments or bicomponent filaments and that the mass ratio of the first, lower-melting-point plastic component present on the outer surface der filaments to the at least one second, higher-melting-point plastic component is 35:65 to 50:50 and preferably 40:60 to 45:55. As has already been demonstrated further above, the melting points of the two plastic components can also be equal or essentially equal.
In a recommended embodiment, the package according to the invention, in particular the packaging bag according to the invention, has at least one flat bottom wall that is a component of the package wall and that has at least one spun-bonded nonwoven or packaging spun-bonded nonwoven, in particular one that is specified in greater detail above. This spun-bonded nonwoven or packaging spun-bonded nonwoven forms the bottom wall and/or is a component of the bottom wall. The at least one spun-bonded nonwoven of the bottom wall is preferably firmly bonded, in particular welded, to the side wall or to the spun-bonded nonwoven material of the side wall of the package. It is advisable for the spun-bonded nonwoven of the bottom wall to have multicomponent filaments or bicomponent filaments or to be composed or essentially of multicomponent filaments or bicomponent filaments and for the mass ratio of the first, lower-melting-point plastic component present on the outer surface der filaments to the at least one second, higher-melting-point plastic component is 35:65 to 50:50 and preferably 40:60 to 45:55.
The invention is based on the recognition that a weldable spun-bonded nonwoven or weldable packaging spun-bonded nonwoven according to the invention can be made in an easy, non-complex, trouble-free way and can be processed into packages, and in particular is weldable. Of particular importance in the context of the invention is the fact that the required welding temperatures when welding the spun-bonded nonwovens can be significantly reduced in comparison to the processing measures that are known from everyday use. Above all, it is possible to work with a homogeneous welding temperature. The invention is also based on the recognition that in the spun-bonded nonwoven according to the invention, thin points and thick points that are problematic for the welding can largely be avoided. Primarily, the invention is based on the recognition that the above-described advantages particularly come into being through the combination of the filler according to the invention, in particular calcium carbonate, on the one hand with the implementation of the spun-bonding method according to the invention on the other.
The invention is based, among other things, on the recognition that the filler according to the invention, particularly in the form of calcium carbonate, gives a better weldability of the spun-bonded nonwoven. It is assumed that the filler or the calcium carbonate on the one hand absorbs less heat than the associated plastic component and on the other simultaneously has a higher thermal conductivity than the plastic. This results in the fact that the filler or the calcium carbonate can convey or impart the introduced heat in a metered fashion to the plastic that is to be melted or softened so that the associated plastic component can be melted selectively. The invention is also based on the recognition that a filler in the form of calcium carbonate improves the UV stability of the filaments and the spun-bonded nonwovens. For this reason, an additional UV stabilizer for the plastic of the spun-bonded nonwoven is not necessary and it is thus possible to reduce raw material consumption. The optimal processability or weldability of a weldable spun-bonded nonwoven according to the invention also results from the advantageous lay quality of the filaments and of the spun-bonded nonwoven in the implementation of the spun-bonding method according to the invention. It achieves a significantly better homogeneity of the spun-bonded nonwoven in comparison to other known methods and as a result, the processing temperature or welding temperature for the spun-bonded nonwovens according to the invention can be considerably reduced in comparison to known nonwovens.
The spun-bonded nonwovens according to the invention and the packages according to the invention that are made out of them exhibit outstanding strength. This is true both for the package wall in and of itself and also for the bonding seams, in particular welding seams, between the package wall regions. The package wall and the bonding seams between the package wall regions feature a high mechanical resistance. In fall tests with filled packages according to the invention, in particular packaging bags according to the invention filled with cement, damage to the package wall or the welding seams between the package wall regions rarely if ever occurs. By contrast with the packaging bags known from the prior art, a tearing of the package wall is hardly ever observed. A weldable spun-bonded nonwoven according to the invention and a package according to the invention made from it, however, also have additional advantages.
On the one hand, the package wall can be cleaned without significant trouble, particularly from the outside. On the other, the package according to the invention also features an attractive outer visual appearance. Furthermore, a weldable spun-bonded nonwoven made according to the invention and a package made from it can exhibit outstanding barrier effects so that in particular, it is not necessary to provide an additional outer coating of the package.

BRIEF DESCRIPTION OF THE DRAWING

The invention will be explained in greater detail below in conjunction with drawings that depict only one exemplary embodiment. In the drawings:

FIG. 1 is a schematic, perspective view of a package according to the invention in the form of a bag,

FIG. 2 is a schematic vertical section through am apparatus for carrying out a method of making a weldable spun-bonded nonwoven or packaging spun-bonded nonwoven according to the invention, and

FIGS. 3A and 3B are a schematic cross-sections through a bicomponent filament of a spun-bonded nonwoven or packaging spun-bonded nonwoven respectively used in the side wall region of the packaging bag and in the bottom wall and/or top wall of the packaging bag.

SPECIFIC DESCRIPTION OF THE INVENTION

FIG. 1 shows a package according to the invention in the form of a packaging bag 1 for bulk materials, in particular for cement.
The package wall of this packaging bag 1 contains weldable spun-bonded nonwovens 2 according to the invention. These spun-bonded nonwovens 2 or packaging spun-bonded nonwovens are of endless filaments 3 of a thermoplastic plastic. The endless filaments 3 contain at least 3 wt % of a filler 4 in the form of calcium carbonate to improve the weldability of the filaments and of the spun-bonded nonwoven 2 and in particular to reduce the welding temperature during thermal welding of the filaments or of the spun-bonded nonwoven 2.
The packaging bag 1 shown in FIG. 1 has a side wall 5 of a spun-bonded nonwoven according to the invention that has been welded at its side edges 6 into a tube, so to speak. A flat bottom wall 7 in the form of a spun-bonded nonwoven 2 according to the invention is positioned at the bottom of the packaging bag 1 and is welded to the side wall 5 of the packaging bag 1. A flat top wall 8 in the form of a spun-bonded nonwoven 2 according to the invention is likewise positioned at the top of the packaging bag 1 and welded to the side wall 5. On an inner face of the package wall of the packaging bag 1, an additional plastic film can be provided, but this is not shown in the embodiment according to FIG. 1. The spun-bonded nonwovens used for the side wall 5, the bottom wall 7, and the top wall 8 of the packaging bag 1 are preferably, and in this embodiment, of bicomponent filaments with a core/sheath configuration (also see FIG. 3). Of the two plastic components of these bicomponent filaments, the lower-melting-point plastic component is the sheath 9 and the higher-melting-point plastic component is the core 10. the filler 4 in the form of calcium carbonate is preferably, and in this embodiment, only contained in the sheath 9 of the bicomponent filaments.
FIG. 2 shows a particularly preferred apparatus for manufacturing the spun nonwovens 2 (spun-bonded nonwovens) according to the invention. The endless filaments 3 in this case are first spun by a spinneret 11 and are then conveyed through a monomer aspirator 12. Then the endless filaments 3 are chilled in the cooler 13. The cooler 13 preferably, and in this embodiment, has two compartments 14, 15 one above another or one after another in the filament flow direction from which cooling air with different temperatures is introduced into the filament flow chamber. After the cooler 13, the endless filaments 3 travel into an intermediate conduit 16 that converges in the filament flow direction. This intermediate conduit 16 is followed by a pull-down conduit 17 of the stretcher 18. This design serves to stretch the endless filaments 3. The endless filaments 3 emerging from the pull-down conduit 17 then preferably, and in this embodiment, pass through two diffusors 19, 20 one above the other or one after another in the filament flow direction. In a recommended embodiment, and here, an ambient air entry gap 25 is provided between the diffusors 19, 20 for drawing in ambient air. Advantageously, and in this embodiment, the endless filaments 3 are then deposited on a mesh belt 21 to form the spun-bonded nonwoven 2. The spun-bonded nonwoven 2 is advanced in the machine direction M by the mesh deposition belt 21.
Preferably, and in this embodiment, the spun-bonded nonwoven 2 is calendered and prehardened/hardened by a calender 22. According to one variant, a calender roller 23 is provided with an engraving, not shown in detail, and a calender roller 24 of the calender 22 that cooperates with and is works with it is preferably, and in this embodiment, equipped with a smooth surface. A spun-bonded nonwoven 2 made in the above-explained manner can be simply and easily used for a package wall (side wall 5 and/or bottom wall 7 and/or top wall 8) of the packaging bag 1.
FIG. 3A and 3B show bicomponent filaments for a weldable spun-bonded nonwoven 2 according to the invention. In the FIG. 3A, the percentage of the core 10 is higher in comparison to the sheath 9. In the bicomponent filaments according to FIG. 3B, the filler in the form of calcium carbonate is contained only in the sheath 9 that corresponds to the lower-melting-point plastic component. The bicomponent filaments according to FIG. Aa are primarily suitable for spun-bonded nonwovens 2 that form the side wall 5 of a packaging bag 1.
By contrast, the bicomponent filaments according to FIG. 3B have a significantly higher percentage of sheath 9 of the lower-melting-point plastic component. Here, too, the filler preferably, and in this embodiment, is completely contained in the sheath 9. The bicomponent filaments according to FIG. 3B are primarily suitable for spun-bonded nonwovens 2 or spun-bonded nonwoven regions that must be welded. The sheath 9 with the lower-melting-point plastic component provides enough welding material for this purpose. Welding is preferably carried out in that only or mainly the sheath 9 melts and is welded. Consequently, the bicomponent filaments according to FIG. 3B are primarily suitable for the bottom wall 7 and/or the top wall 8 that is to be welded of a packaging bag according to the invention 1.
The mass ratio of the lower-melting-point plastic component (sheath 9) to the higher-melting-point plastic component (core 10) may be 20:80 in the embodiment according to FIG. 3A. By contrast, in this embodiment according to FIG. 3B, the mass ratio of the lower-melting-point plastic component 5 (sheath 9) to the higher-melting-point plastic component (core 10) is 40:60.

Claims

1. A method of making a weldable spun-bonded nonwoven or packaging spun-bonded nonwoven comprising the steps of:

spinning endless filaments having sheaths of a first thermoplastic surrounding respective cores of a second thermoplastic wherein

the sheaths contain at least 3 wt % of at least one filler,

the first thermoplastic forming the sheaths of the multicomponent filaments has the same or a lower melting point than the second thermoplastic forming the cores of the filaments such that filaments are weldable to each other by fusing together the sheaths,

a mass ratio of the first plastic component forming the sheaths to the second plastic component forming the cores is 25:75 to 50:50 and in welded regions 35:65 to 50:50;

depositing the filaments to form a spun-bonded nonwoven web;

calendering an outer face of the spun-bonded nonwoven web smooth and without engraving; and

engraving an inner face of the spun-bonded nonwoven web 15 to 35% and to an embossing depth of 0.1 to 0.6 mm.

2. The method according to claim 1, wherein the first plastic of the continuous filaments has 4 to 25 wt % of the filler.

3. The method according to claim 1, wherein the filler is a metal salt.

4. The method according to claim 1, further comprising after the step of spinning and before the step of depositing the steps of sequentially:

cooling the filaments in a cooler; and

stretching the cooled filaments in a stretcher.

5. The method according to claim 1, wherein during calendering the spun-bonded nonwoven is pressed with a calender having an embossing surface of 10 to 90% to 30%.

6. The method according to claim 1, wherein a number of engraved points of the calender is greater than 30/cm².

7. The method according to claim 1, wherein the first component of the continuous filaments has 4 to 25 wt % of the filler.

8. The method according to claim 1, wherein the melting point of the second plastic of the cores is above that of first thermoplastic of the sheaths, the method further comprising the steps after engraving of:

cutting pieces of the web, and

welding the pieces together at edges thereof by applying sufficient heat to melt only the sheaths of the filaments, whereby the melted sheets fuse together.

9. A package having walls formed of a weldable spun-bonded nonwoven and having welded wall regions, wherein

the spun-bonded nonwoven has continuous multicomponent filaments of a thermoplastic plastic of both components each have a thermoplastic core surrounded by a thermoplastic sheath,

the sheaths of the continuous multicomponent filaments of both components contain at least 3 wt % of at least one filler, whereby weldability of the spun-bonded nonwoven is improved by reducing a welding temperature in thermal welding of the spun-bonded nonwoven,

a first plastic component forming the sheaths of the multicomponent filaments has the same or a lower melting point than a second plastic component forming the cores of the filaments,

a mass ratio of the first plastic component forming the sheaths to the second plastic component forming the cores is 25:75 to 50:50 and in the welded wall regions 35:65 to 50:50,

an outer face of the spun-bonded nonwoven is calendered smooth and without engraving, and

an inner face of the spun-bonded nonwoven is engraved 15 to 35% and to an embossing depth of 0.1 to 0.6 mm.

10. The package according to claim 9, wherein the first component of the continuous filaments has 4 to 25 wt % of the filler.

13. The package according to claim 9, wherein the filler is a metal salt.

14. The package according to claim 9, wherein the package is formed of a plurality of pieces of the calendered and engraved nonwoven joined together at seams where the first thermoplastic of the sheaths are fused together but the second thermoplastic of the cores is not fused.