WO2010023606A1 - A novel mono-axially oriented multilayer slit film tape yarn, and an apparatus and a process to make the same - Google Patents

A novel mono-axially oriented multilayer slit film tape yarn, and an apparatus and a process to make the same Download PDF

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Publication number
WO2010023606A1
WO2010023606A1 PCT/IB2009/053687 IB2009053687W WO2010023606A1 WO 2010023606 A1 WO2010023606 A1 WO 2010023606A1 IB 2009053687 W IB2009053687 W IB 2009053687W WO 2010023606 A1 WO2010023606 A1 WO 2010023606A1
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WO
WIPO (PCT)
Prior art keywords
slit film
multilayer
film tape
tapes
slit
Prior art date
Application number
PCT/IB2009/053687
Other languages
French (fr)
Inventor
Amit Kumar Lohia
Original Assignee
Lohia Starlinger Limited
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Filing date
Publication date
Application filed by Lohia Starlinger Limited filed Critical Lohia Starlinger Limited
Publication of WO2010023606A1 publication Critical patent/WO2010023606A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/32—Layered products comprising a layer of synthetic resin comprising polyolefins
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
    • B29C48/07—Flat, e.g. panels
    • B29C48/08—Flat, e.g. panels flexible, e.g. films
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/16—Articles comprising two or more components, e.g. co-extruded layers
    • B29C48/18—Articles comprising two or more components, e.g. co-extruded layers the components being layers
    • B29C48/21—Articles comprising two or more components, e.g. co-extruded layers the components being layers the layers being joined at their surfaces
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/30—Extrusion nozzles or dies
    • B29C48/305—Extrusion nozzles or dies having a wide opening, e.g. for forming sheets
    • B29C48/307—Extrusion nozzles or dies having a wide opening, e.g. for forming sheets specially adapted for bringing together components, e.g. melts within the die
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/36—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die
    • B29C48/395—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die using screws surrounded by a cooperating barrel, e.g. single screw extruders
    • B29C48/397—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die using screws surrounded by a cooperating barrel, e.g. single screw extruders using a single screw
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
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    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/36—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die
    • B29C48/49—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die using two or more extruders to feed one die or nozzle
    • B29C48/495—Feed-blocks
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    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
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    • B29C48/91—Heating, e.g. for cross linking
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    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
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    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
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    • B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
    • B29C55/02—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets
    • B29C55/023—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets using multilayered plates or sheets
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
    • B29C55/02—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets
    • B29C55/04—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets uniaxial, e.g. oblique
    • B29C55/06—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets uniaxial, e.g. oblique parallel with the direction of feed
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
    • B29C55/02—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets
    • B29C55/04—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets uniaxial, e.g. oblique
    • B29C55/06—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets uniaxial, e.g. oblique parallel with the direction of feed
    • B29C55/065—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets uniaxial, e.g. oblique parallel with the direction of feed in several stretching steps
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B32B27/08—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/18—Layered products comprising a layer of synthetic resin characterised by the use of special additives
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/18—Layered products comprising a layer of synthetic resin characterised by the use of special additives
    • B32B27/20—Layered products comprising a layer of synthetic resin characterised by the use of special additives using fillers, pigments, thixotroping agents
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/88—Thermal treatment of the stream of extruded material, e.g. cooling
    • B29C48/911—Cooling
    • B29C48/9135—Cooling of flat articles, e.g. using specially adapted supporting means
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2023/00—Use of polyalkenes or derivatives thereof as moulding material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2105/00—Condition, form or state of moulded material or of the material to be shaped
    • B29K2105/06—Condition, form or state of moulded material or of the material to be shaped containing reinforcements, fillers or inserts
    • B29K2105/16—Fillers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
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    • B32B2250/24—All layers being polymeric
    • B32B2250/242—All polymers belonging to those covered by group B32B27/32
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    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
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    • B32B2264/10—Inorganic particles
    • B32B2264/104—Oxysalt, e.g. carbonate, sulfate, phosphate or nitrate particles
    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B32B2307/00—Properties of the layers or laminate
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    • B32B2307/514—Oriented
    • B32B2307/516—Oriented mono-axially
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Definitions

  • the present invention relates to polymer slit film tapes used in the woven fabric industry.
  • it relates to the multilayer slit film tapes containing inorganic filler and a method of manufacturing such tapes.
  • Slit film tapes - also known as film bands, strips, slit film tapes, raffia tapes, tape yarn and mono-axially oriented tapes - are defined as unidirectional oriented tapes with a high width-to-thickness ratio and produced by slitting sheet or films made from thermoplastics, followed by monoaxial stretching.
  • Slit film tapes made of polyolefin's such as polypropylene (PP), high density polyethylene (HDPE) and linear low density polyethylene (LLDPE) and other similar polymeric materials have been in use for several industrial applications.
  • the major areas of application of slit film tapes include woven sacks, large industrial sacks and packaging fabrics, geo-textiles, ropes and twines, and miscellaneous industrial woven fabrics.
  • the polyolefin-based slit film tapes are made from films that are extrusion cast in a flat or tubular (blown) form. The blown film is best for certain types of thin slit film tape yarns. The majority of slit film tapes are made from cast films.
  • the slit film tapes are typically formed by slitting sheets of extruded film.
  • the slit-film tapes are then stretched by using one of the two known processes - stretching all slit tapes formed from a film together as a single group or stretching single slit- film tapes or stretching groups containing a number of tapes.
  • molten polyolefin is extruded in monolayer by single extruder through a suitable extrusion die to form a sheet (or film) of required thickness which is suitably cooled by a devices such as a water- quencher or a set of chilled roll(s). Then the substantially amorphous sheet is transported under tension to a suitable slitting device for slitting into tapes.
  • the slit tapes are mono-axially oriented by drawing in a longitudinal direction, under heat treatment.
  • the drawn tapes are defined in terms of an orientation ratio, which is also known as the draw or stretch ratio.
  • the stretched tapes are then annealed and wound to form bobbins on suitable winding device.
  • the tapes may also be fibrillated and twined, resulting in a yarn.
  • the tapes are woven on suitable weaving device to form flat fabric and/or tubular fabric suitable for various applications such as woven sacks, large industrial sacks and packaging fabrics, geo-textiles, tarpaulin and the like.
  • Inorganic or organic additives with suitable particulate geometry typically known as fillers, are added to the thermoplastics for modifying or enhancing physical and thermal properties, improving and controlling of processing conditions and achieving an overall cost reduction.
  • the most commonly used particulate fillers are industrial minerals such as talc, calcium carbonate, mica, kaolin, woilastonite, feldspar, and barite.
  • the most commonly used filler in the manufacture of polyolefin-based monolayer slit film tapes is calcium carbonate, which is introduced in the extrusion system using a commercially available calcium carbonate masterbatch (hereinafter referred to as CCMB) that contains the mineral and the resin optionally processing additives or their combination.
  • CCMB calcium carbonate masterbatch
  • the CCMB enhances the thermal conductivity and the specific heat of polyolefin, reduces fibrillation tendency of the tape and also improves the productivity of the tape making process due to higher specific gravity of the raw material mixture.
  • Calcium carbonate in the powder form is an abrasive material. When deposited on the machinery, it has the potential to damage the metal parts and reduce the working life of the machinery and increase the machinery downtime and maintenance costs.
  • US 4533510 discloses methods and apparatus for continuously producing a thermoplastic sheet composed of a plurality of thermoplastic materials co- extruded in segments, wherein at least one of the segments comprises a multi- layered thermoplastic sheet, and at least one other segment comprises a layer of a single material. It has been claimed that the method and apparatus are effective to produce a thermoplastic sheet having two or more layers in a central portion of the sheet and only a single layer at the edge portions of the sheet. However, there's no mention of inorganic fillers such as calcium carbonate in the patent document. US patent 7318961 talks of a multilayered material of high stretch ratio. All layers are created using the same basic materials but which have different DSC melting points.
  • the product has excellent mechanical properties such as mechanical strength, stiffness and the like. It also claims that because it is a mono-component material, it has a higher recycle numbers as there are no 'impurities'. However, there is no suggestion in the patent that inorganic fillers in high proportion could be used while maintaining strength properties and reducing costs.
  • a further object of the present invention is to develop a slit film tape (and the process of making it), which reduces the mechanical wear and tear of the machinery that uses it, particularly those parts that are in contact with the slit film tape.
  • a still further object of the present invention is to develop an economical slit film tape containing high proportion of inorganic fillers but which does not emit or ooze dust, either from the tape surface or its edges, and lends itself well for printing operation.
  • a yet further object of the present invention is to develop a stable process of manufacturing the multilayer slit film tape with normal tensile properties and reasonable production/machine speed.
  • Another object of the present invention is to ensure that the individual layers of the multilayer slit film of the invention do not separate out in downstream processing.
  • the present invention discloses a multi-layered tape slit-film tape made from polymer resin and inorganic fillers, comprising at least one central layer with a high proportion of inorganic filler, preferably CCMB, and external layers with high proportion of polymer resin, preferably polyolefin.
  • the invention also discloses a process of and apparatus for making such slit film tapes.
  • the slit film tapes of the present invention have adequate mechanical and thermal properties for use in slit film tape woven fabric industry and are more economical than the existing slit film tapes that are used for the same purpose.
  • the multilayer slit film tapes are found to be devoid of drawbacks such as excessive inorganic dust, the consequent wear and tear of the machinery, and hazard to human health, resulting from the use of the currently available monolayer slit- film tapes that use inorganic fillers.
  • Figure 1 Residual deposits on weaving machinery using monolayer tapes using inorganic fillers
  • Figure 2 Typical manufacturing line for a monolayer monoaxially stretched slit film tape
  • FIG. 3 Multilayer die, extruder, and feedblock schematic set up for present invention
  • FIG. 3A Feedblock and multilayer die arrangement
  • Figure 3B An alternative schematic set up for the multilayer die, extruder, and feedblock system
  • Figure 4 Multilayer slit-film tape of the present invention
  • Figure 4A Variations of the multilayer film of the present invention
  • Monolayer tape die 9. Web of slit film tapes
  • the invention accordingly concerns development of multilayer slit film tape containing inorganic fillers, preferably in a high proportion, and an extrusion line/machine for manufacturing such tapes.
  • a monolayer film is extruded through a monolayer tape die (1) mounted on a single extruder (2).
  • the film passes through a series of devices such as a water bath (3), a film slitting unit (4), after which the web of slit film tapes (9) passes through a holding unit (5), a hot air oven (6), a stretching and annealing unit (7), and a winding device (8).
  • the multilayer film (15) is extruded through a specially designed multilayer die (10) (also referred to as a flat die) that is independently mounted on a standalone mounting device (11) (not shown in figure), preferably a stand, and which is fed by a number of extruders (preferably 2A and 2B as shown in Figure 3, and optionally 2C as shown in Figure 3B, or more extruders) via suitably designed multichanneled feedblock (10A).
  • a specially designed multilayer die 10
  • a standalone mounting device (11) not shown in figure
  • extruders preferably 2A and 2B as shown in Figure 3, and optionally 2C as shown in Figure 3B, or more extruders
  • the feedblock (10A) arranges the incoming melt streams from two different extruders (2A and 2B) in the required order, balances the velocities of streams and combines the melt streams to form a multilayer molten composite which is compressed-fed to the flat die (10).
  • the finished configuration of the multilayer film (15) is ABA, the letters A denoting the external layers (14) between which the central layer B (13) is positioned.
  • a layer of type C denoted as layer C (14A), and which is also categorized as an external layer, is incorporated.
  • the flat die (10) designed specifically for casting a multilayer film (15) has internal geometry that addresses the layer order and ensures the uniformity of the cast multilayer film (15).
  • the multilayer polymer composite fed to flat die (10) is then spread and thinned out to its desired final form which is the multilayer film (15).
  • Figure 3 shows schematically, individual extruders (2A and 2B) feeding into the feedblock (10A) of the invention.
  • an extruder EB (2B) extrudes the molten material that forms the central layer B (13) of the multilayer film (15) of the present invention and the two external layers A (14) are formed by a single second extruder EA (2A).
  • the electronic controls for the extruders are designed such that both extruders (2A and 2B) operate synchronously to achieve the required feed rate.
  • the extruder delivery or output is adjusted independently as per the requirement.
  • the extruded multilayer film (15) cast through the die (10) of the present invention is then suitably cooled using a set of chill rollers or, more preferably by the water bath (3) method.
  • the formed and cooled multilayer film (15) passes through a slitting device (4) and then through a drawing zone that consists of single stage stretching units or multi-stage stretching units.
  • the slit film tapes (16) thus formed and drawn are annealed. After drawing and annealing process, the slit film tapes (16) are wound on the suitable package on the winding device (8).
  • a multilayer slit film tape (16) is disclosed.
  • the multilayer film (15) which is slit to create the multilayered slit film tapes (16) is made from a polymer matrix to which a filler material, preferably inorganic, and optionally other additives are added.
  • the multilayer slit film tape (16) has preferably three layers of ABA configuration as shown in figure 4, comprising a central layer B (13) which is sandwiched between two external layers A (14).
  • the polymer matrix of the central layer B (13) and external layers A (14) are selected from same or different poly olefin grade which are compatible with each other.
  • the polymer matrix is made from a material selected from the group comprising, polypropylene (PP), high density polyethylene (HDPE), linear low density polyethylene (LLDPE) and other similar polymeric material, or any combination thereof.
  • PP polypropylene
  • HDPE high density polyethylene
  • LLDPE linear low density polyethylene
  • the resin used is either virgin polymer, optionally blended with commercially available additives such as anti- fibrillating agent, ultra-violet stabilizer, color masterbatch, or recycled polymer and like.
  • the central layer B (13) constitutes 20% to 80%, preferably more than 50%, by total weight of the tape (16) and balance is contributed by external layers A (14), preferably in equal proportions.
  • the central layer B (13) consists of polymer resin, preferably polyolefin and filler, preferably inorganic, which is preferably in a higher proportion with the polymer.
  • the proportion of the filler material in the layer B (13) is higher, preferably significantly higher than that of the external layers A (14).
  • the inorganic filler in the central layer B (13) is added in the form of the commercially available CCMBs such that the CCMB forms up to 10% to 90% (w/w) (w/w denoting proportion or percentage by weight), preferably 30% to 70% (w/w), more preferably up to 50% (w/w) of the total weight of the central layer B (13). It is evident that the central layer B (13) contains a high proportion of the inorganic filler.
  • Each external layer A (14) contains a filler, most preferably in the form of CCMB, such that the CCMB forms up to 0% to 20% (w/w), preferably 3% to 20% (w/w), more preferably 3% to 8% by weight of the total weight of external layers A (14).
  • both the central and external layers (13 and 14) may generally contain conventional additives, including but not limited to UV stabilizers, conductive compounds, processing aids, colour pigments and like.
  • the CCMB used in the present invention is sourced from any commercially available sources known to a person skilled in the art.
  • the proportion of calcium carbonate in CCMB is of crucial importance.
  • the slit film tapes (16) of the present invention have a width between 0.8 mm to 160 mm, preferably between 2mm and 5mm; a thickness between 0.015 mm and 0.3 mm, preferably between 0.025mm and 0.1mm; and denier between 200 and 45,000, preferably between 400 and 2500.
  • the total number of external layers (A and C) is three or more, in the formats ABCA ACABA, ACABAC, ABABC and so on (see Figure 4A).
  • the number of external layers on either side of the central layer B (13) is preferably same; alternatively the number of external layers on either side of the central layer B (13) is different; preferably there is at least one external layer on either side.
  • the composition of layers A and B is the same as that disclosed in the second preferred embodiment.
  • the layer C (14A) which is also categorized as an external layer, constitutes 10% to 80%, preferably less than 50% of the total weight of the multilayer film (15).
  • the external layers A and C have different composition; however, both contain low proportion of CCMB that is within the relevant ranges used in the second preferred embodiment.
  • the feedblock (10A) has sufficient number of channels (12) arranged in appropriate order such that the film (15) cast from the multilayer die (10) is in the format selected from a group comprising ABCA, ACABA, ACABAC, ABABC, and so on (see Figure 4A).
  • a third extruder EC (2C) is added to extrude the molten material that forms the external layers C (14A).
  • the feedblock (10A) has sufficient number of channels (12) arranged in appropriate order such that the film (15) cast from the multilayer die (10) is in the format selected from a group comprising ABCA (see Figure 4A), ACABA, ACABAC, ABABC and so on.
  • the slit film tapes (16) are drawn after slitting, their thickness reduces, whereby the inorganic filler gets further embedded and securely oriented within the resinous matrix of the tapes, thereby reducing the amount of loose inorganic filler that can potentially ooze out from the exposed edges of the tapes during their lifetime, particularly during downstream operations on the winders and looms.
  • a process of manufacturing a multilayer slit film tape containing high proportion of inorganic filler comprises the steps of:
  • Cooling said film preferably using chill rollers or water bath (3) method.
  • the slit film tape (16) is stretched by total draw ratio between 3 and 20, preferably between 5 and 15, more preferably 10, even more preferably 4 to 7, so the tensile properties suitable for application of slit film tapes (16) are achieved.
  • the inventive multilayer slit film tapes (16) of the present invention are monoaxially stretched by passing them sequentially over a set of heated rollers and/or through a combination of heating device such as hot plates or convection heating device (6).
  • the heating/stretching temperature is between 6O 0 C to 175 0 C depending on the material composition of the tapes.
  • the speed of each successive roller is higher than that of predecessor roller, which results in the desired orientation/stretching of slit film tapes (16).
  • the stretched slit film tapes (16) are annealed, usually by using set of annealing rollers kept at ambient temperature. Alternatively, and preferably, heated annealing rollers operating at almost same speed as the final stretching roller are used following which the tapes (16) are cooled on a set of cooled annealing rollers operating at reduced surface speed than the stretching rollers.
  • the final line speed is maintained between 100 to 650 m/min, preferably between 300 to 600 m/min.
  • the formed multilayer slit film tapes are then formed into suitable packages using winding devices (8).
  • the multilayer slit film tapes (16) of the present invention are used to make fabric suitable for various applications such as woven sacks, large industrial sacks and packaging fabrics, geo-textiles, ropes and twines and miscellaneous industrial woven fabrics.
  • the multilayer slit film tapes (16) are fibrillated during or after the processing and then twisted and/or twined to produce desired yarn.
  • the multilayer slit film has two layers.
  • the final form of the tape (16) is either of AB, AC, or BC.
  • Each of the two layers may use same or different polyolefin grade and have same or different proportion of filler, however, the overall composition of each of the two layers is different from each other.
  • the multilayer slit film tape was prepared such that the central layer consisted of 80% w/w of Polypropylene (Reliance, 3 MFI) and 20% w/w of CCMB and each of the two external layers consisted of 96% w/w of Polypropylene (Reliance, 3 MFI) and 4% w/w CCMB, resulting in three layer slit film tape in which the layers of the ABA configuration are in the proportion 15%:70%:15% w/w.
  • the extrusion temperature for all layers was 260 0 C.
  • the water bath temperature was 30 0 C, total stretch ratio was 5.5, stretching oven temperature 150 0 C & the annealing ratio 0.95 for the final line speed of 380 m/min.
  • the multilayer slit film tape thus formed was of 900 denier and 3 mm width. It had a tenacity of 5.4 gpd and elongation of 25% at break. When a tubular woven fabric was made from this multilayer slit film tapes, very low dust was visible on the circular loom which was running at 820 picks per minute (ppm) speed.
  • the multilayer slit film tape was prepared such that the central layer consisted of 76% w/w of Polypropylene (Reliance, 3 MFI), 22% w/w of CCMB and 2% w/w of a colour additive in the form of a red colour masterbatch; each of the two external layers consisted of 94% w/w of Polypropylene (Reliance, 3 MFI) and 4% w/w of CCMB and 2% w/w of a colour additive in the form of a red colour masterbatch, resulting in three layer slit film tape in which the layers of the ABA configuration were in the proportion 16%:68%:16% w/w.
  • the extrusion temperature for all layers was 260 0 C.
  • the water bath temperature was 28 0 C, total stretch ratio 5.4, stretching oven temperature 150 0 C & the annealing ratio 0.94 for the final line speed of 360 m/min.
  • the multilayer slit film tape thus formed was of 900 denier and 3 mm width. It had a tenacity of 5.3 gpd and elongation of 24% at break. When a tubular woven fabric was made from this multilayer slit film tapes, very low dust was visible on the circular loom which was running at 810 picks per minute (ppm) speed.
  • Example 3
  • the multilayer slit film tape was prepared such that the central layer consisted of
  • the multilayer slit film tape thus formed of 900 denier and 3 mm width had a tenacity of 5.5 gpd and elongation of 24% at break.
  • a tubular woven fabric was made from this multilayer slit film tapes, low dust was visible on the circular loom which was running at 820 picks per minute (ppm) speed.
  • the multilayer slit film tape was prepared such that the central layer consisted of
  • the multilayer slit film tape thus formed was of 820 denier and 2.5 mm width. It had a tenacity of 5.4 gpd and elongation of 23% at break. When a tubular woven fabric was made from this multilayer slit film tapes, very low dust was visible on the circular loom which was running at 840 picks per minute (ppm) speed.
  • the multilayer slit film tape was prepared such that the central layer consisted of 50% w/w of Polypropylene (Reliance, 3.4 MFI), 50% w/w of CCMB and each of the two external layers consisted of 96% w/w of Polypropylene (Reliance, 20 MFI) and 4% w/w of calcium MB, resulting in three layer slit film tape in which the layers of the ABA configuration were in the proportion 15%: 70%: 15% w/w.
  • the extrusion temperature for the core/central layer was 265 0 C and for the external layers 245 0 C.
  • the water bath temperature was 26 0 C, total stretch ratio 5.7, stretching oven temperature 152 0 C & the annealing ratio 0.96 for the final line speed of 390 m/min.
  • the multilayer slit film tape thus resulted was of 800 denier and 2.5 mm width. It had a tenacity of 4.8 gpd and elongation of 22% at break.
  • ppm picks per minute
  • Figure 1 shows residual dust on a part of the circular loom that has in operation a monolayer tape of 820 denier, 2.5 mm width containing high proportion of inorganic filler which were CCMB 12% w/w.
  • Figure 5 shows a part of the circular loom that has in operation the multilayer slit film tape of the present invention as per example 4 (820 denier, 2.5mm width & total CCMB more than 22% (w/w)).
  • a monoaxially drawn multilayer slit film tape comprising a polymer matrix and inorganic filler, said slit film tape made by slitting a multilayer film made of two or more layers, each of said layers preferably containing said inorganic filler.
  • a monoaxially drawn multilayer slit film tape as described in item 1 wherein the total number of layers is at least three, wherein a central layer is cohesively bonded between at least two external layers, preferably at least one external layer positioned on each side of said central layer, wherein said external layers is of the type A or C.
  • a monoaxially drawn multilayer slit film tape as described any of the preceding items wherein the proportion of said masterbatch in the central layer is in the range between 10% (w/w) to 90% (w/w), preferably 30% (w/w) to 70% (w/w), more preferably 50% (w/w) of the total weight of the central layer, and wherein the proportion of said filler in each of said external layers is in the range between 0% (w/w) to 20% (w/w), preferably 3% (w/w) to 20% (w/w) more preferably 3% (w/w) to 8% (w/w) by weight of the total material of external layer.
  • a monoaxially drawn multilayer slit film tape as described any of the preceding items wherein the width of said slit film tapes is between 0.8 mm to 160 mm, preferably between 2 mm and 5 mm; and wherein the thickness of said slit film tapes is between 0.015 mm and 0.3 mm, preferably between 0.025 mm and 0.08 mm; and denier of said slit film tapes is between 200 and 45,000, preferably between 400 and 2500.
  • polymeric material is from a material selected from the group comprising, polypropylene (PP), high density polyethylene (HDPE), linear low density polyethylene (LLDPE) and other similar polymeric material, or any combination thereof.
  • PP polypropylene
  • HDPE high density polyethylene
  • LLDPE linear low density polyethylene
  • a process of making a monoaxially drawn multilayer slit film tape comprising the steps of:
  • extruding a multilayer film through an independently mounted flat die said die being fed by at least two different extruders via suitably designed feedblock such that one of the said extruder forms the central layer of said film and the remaining extruder form respective external layers, further wherein all extruders operate in synchronous manner as per the required feed rate,
  • a monoaxially drawn multilayer slit film tape as described in item 6, and preferably manufactured using a process of item 8, wherein said slit film tape is stretched by total draw ratio between 3 and 20, preferably between 5 and 15 even more preferably 4 to 7.
  • An apparatus of making a monoaxially drawn multilayer slit film tape comprising a system of at least two extruders, a feedblock, and a flat die, wherein a multilayer film is extruded through said flat die that is independently mounted on a standalone mounting device, preferably a stand, and which said die is fed by said multiple number of extruders via said feedblock which combines the melt streams to form a multilayer molten composite which is fed to said flat die, and wherein said flat die has the internal geometry to ensure that the cast film produced has the desired format selected from the group comprising ABCA, ACABA, ACABAC, ABABC, and so on.

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Abstract

The present invention discloses a multi-layered tape slit-film tape made from polymer resin and inorganic fillers, comprising at least one central layer with a high proportion of inorganic filler, preferably a commercially available calcium carbonate masterbatch and external layers with high proportion of polymer resin, preferably polyolefin. The invention also discloses a process of and apparatus for making such slit film tapes. The slit film tapes of the present invention have adequate mechanical and thermal properties for use in slit film tape woven fabric industry and are more economical than the existing slit film tapes that are used for the same purpose. The multilayer slit film tapes are found to be devoid of drawbacks such as excessive inorganic dust, the consequent wear and tear of the machinery, and hazard to human health, resulting from the use of the currently available monolayer slit-film tapes that use inorganic fillers.

Description

A Novel Mono-axially Oriented Multilayer Slit Film Tape Yarn, And An Apparatus And A Process To Make The Same
Field of Invention
The present invention relates to polymer slit film tapes used in the woven fabric industry. In particular it relates to the multilayer slit film tapes containing inorganic filler and a method of manufacturing such tapes.
Background of Invention Slit film tapes - also known as film bands, strips, slit film tapes, raffia tapes, tape yarn and mono-axially oriented tapes - are defined as unidirectional oriented tapes with a high width-to-thickness ratio and produced by slitting sheet or films made from thermoplastics, followed by monoaxial stretching.
Slit film tapes made of polyolefin's such as polypropylene (PP), high density polyethylene (HDPE) and linear low density polyethylene (LLDPE) and other similar polymeric materials have been in use for several industrial applications. The major areas of application of slit film tapes include woven sacks, large industrial sacks and packaging fabrics, geo-textiles, ropes and twines, and miscellaneous industrial woven fabrics. The polyolefin-based slit film tapes are made from films that are extrusion cast in a flat or tubular (blown) form. The blown film is best for certain types of thin slit film tape yarns. The majority of slit film tapes are made from cast films. The slit film tapes are typically formed by slitting sheets of extruded film. The slit-film tapes are then stretched by using one of the two known processes - stretching all slit tapes formed from a film together as a single group or stretching single slit- film tapes or stretching groups containing a number of tapes.
In a typical process of manufacturing film tapes, molten polyolefin is extruded in monolayer by single extruder through a suitable extrusion die to form a sheet (or film) of required thickness which is suitably cooled by a devices such as a water- quencher or a set of chilled roll(s). Then the substantially amorphous sheet is transported under tension to a suitable slitting device for slitting into tapes. Next, the slit tapes are mono-axially oriented by drawing in a longitudinal direction, under heat treatment. The drawn tapes are defined in terms of an orientation ratio, which is also known as the draw or stretch ratio. The stretched tapes are then annealed and wound to form bobbins on suitable winding device. The tapes may also be fibrillated and twined, resulting in a yarn. The tapes are woven on suitable weaving device to form flat fabric and/or tubular fabric suitable for various applications such as woven sacks, large industrial sacks and packaging fabrics, geo-textiles, tarpaulin and the like. Inorganic or organic additives with suitable particulate geometry (granules, spheres, flakes etc), typically known as fillers, are added to the thermoplastics for modifying or enhancing physical and thermal properties, improving and controlling of processing conditions and achieving an overall cost reduction. The most commonly used particulate fillers are industrial minerals such as talc, calcium carbonate, mica, kaolin, woilastonite, feldspar, and barite.
The most commonly used filler in the manufacture of polyolefin-based monolayer slit film tapes is calcium carbonate, which is introduced in the extrusion system using a commercially available calcium carbonate masterbatch (hereinafter referred to as CCMB) that contains the mineral and the resin optionally processing additives or their combination. The CCMB enhances the thermal conductivity and the specific heat of polyolefin, reduces fibrillation tendency of the tape and also improves the productivity of the tape making process due to higher specific gravity of the raw material mixture.
With increasing price of polyolefin resin there has been trend towards increasing the amount of filler in the slit film tape raw materials. In particular there has been an increase in the use of the CCMB in the production of slit film tapes. The increased in dosage of CCMB in monolayer slit film tapes causes problems in the downstream processes such as winding and weaving. When used in high dosages, calcium carbonate particles migrate to the surface of the monolayer slit film tape. As the particle size of calcium carbonate is typically bigger than that of molten polymer, some of the calcium carbonate particles on the outer surface of the monolayer slit film tape become loosened and ooze out due to frictional contact with mechanical parts such as guides, roller, and support, or due to jerky motion during the manufacturing process. This phenomenon is evident from the white powder (as shown in Figure 1) which is normally found on the surfaces exposed to the monolayer slit film tape during the manufacture process.
Calcium carbonate in the powder form is an abrasive material. When deposited on the machinery, it has the potential to damage the metal parts and reduce the working life of the machinery and increase the machinery downtime and maintenance costs.
Monolayer slit film tapes containing higher proportion of inorganic fillers such as CCMB are available with inorganic fillers such as CCMB in a proportion as high as 20% of total weight of the tape. However, all such products have some of the following drawbacks:
a) They emit or ooze out a lot of dust containing inorganic material, which is harmful for the heath of machine operators and persons working in environs surrounding the production line or looms.
b) Excessive dust containing inorganic material, when deposited on machine parts (such as the tape production line, winders, and looms), causes wear & tears to the moving parts. The amount of dust generated by the use of currently available monolayer slit film tapes is evident from Figure 1.
c) The surfaces of woven fabric made from such slit film tapes offer poor adhesion to the coating layers in subsequent coating/lamination operations.
d) The printing on surfaces of the woven fabric made from such slit film tapes is not of good quality and long lasting.
While there are available multilayer films or sheets made of polymer, slit film tapes made from multilayer films containing high proportions of inorganic material are not available.
US 4533510 discloses methods and apparatus for continuously producing a thermoplastic sheet composed of a plurality of thermoplastic materials co- extruded in segments, wherein at least one of the segments comprises a multi- layered thermoplastic sheet, and at least one other segment comprises a layer of a single material. It has been claimed that the method and apparatus are effective to produce a thermoplastic sheet having two or more layers in a central portion of the sheet and only a single layer at the edge portions of the sheet. However, there's no mention of inorganic fillers such as calcium carbonate in the patent document. US patent 7318961 talks of a multilayered material of high stretch ratio. All layers are created using the same basic materials but which have different DSC melting points. One of the advantages claimed in the patent is that the product has excellent mechanical properties such as mechanical strength, stiffness and the like. It also claims that because it is a mono-component material, it has a higher recycle numbers as there are no 'impurities'. However, there is no suggestion in the patent that inorganic fillers in high proportion could be used while maintaining strength properties and reducing costs.
None of the existing products therefore address the issue of cost reduction while maintaining mechanical and other properties of the slit film tape product at a required level.
In the light of the increasing costs of tape manufacture and the other drawbacks of currently available tapes, there is a need to develop a slit-film tape at a reduced costs and which has adequate properties for the applications such as woven sacks, large industrial sacks and packaging fabrics, geo-textiles, tarpaulin and the like. In particular there is a need for products which have mechanical and thermal properties similar to or better than the existing products, while ensuring the good weavability. Furthermore, there is also a need to provide an apparatus and process for manufacturing such slit film tapes. Furthermore there's a need for a product and the process of making it, which would reduce the amount of polymer in the waste generated during the tape manufacture and also reduce the mechanical wear and tear of the machinery that uses it, particularly those parts that are in contact with the slit film tape. Finally, there's a need to provide an economical slit film tape containing high proportion of inorganic fillers but which does not emit or ooze dust and lends itself well for printing operation.
Objects of the invention:
It is therefore an object of the present invention to develop a slit-film tape which reduces production costs and has adequate properties for the applications such as woven sacks, large industrial sacks and packaging fabrics, geo-textiles, tarpaulin and the like. It is a particular object of the present invention to develop such tapes using polymer resins and inorganic fillers and which has mechanical and thermal properties similar to or better than the existing products while ensuring good weavability.
It is another object of the present invention to develop (or modify an existing one) an apparatus and process for manufacturing multilayered slit-film tapes containing polymer resin and inorganic fillers. A further object of the present invention is to develop a slit film tape (and the process of making it), which reduces the mechanical wear and tear of the machinery that uses it, particularly those parts that are in contact with the slit film tape.
A still further object of the present invention is to develop an economical slit film tape containing high proportion of inorganic fillers but which does not emit or ooze dust, either from the tape surface or its edges, and lends itself well for printing operation.
A yet further object of the present invention is to develop a stable process of manufacturing the multilayer slit film tape with normal tensile properties and reasonable production/machine speed.
Another object of the present invention is to ensure that the individual layers of the multilayer slit film of the invention do not separate out in downstream processing.
Summary of the invention:
The present invention discloses a multi-layered tape slit-film tape made from polymer resin and inorganic fillers, comprising at least one central layer with a high proportion of inorganic filler, preferably CCMB, and external layers with high proportion of polymer resin, preferably polyolefin. The invention also discloses a process of and apparatus for making such slit film tapes. The slit film tapes of the present invention have adequate mechanical and thermal properties for use in slit film tape woven fabric industry and are more economical than the existing slit film tapes that are used for the same purpose. The multilayer slit film tapes are found to be devoid of drawbacks such as excessive inorganic dust, the consequent wear and tear of the machinery, and hazard to human health, resulting from the use of the currently available monolayer slit- film tapes that use inorganic fillers.
List of Figures:
Figure 1 : Residual deposits on weaving machinery using monolayer tapes using inorganic fillers
Figure 2: Typical manufacturing line for a monolayer monoaxially stretched slit film tape
Figure 3: Multilayer die, extruder, and feedblock schematic set up for present invention
Figure 3A: Feedblock and multilayer die arrangement
Figure 3B : An alternative schematic set up for the multilayer die, extruder, and feedblock system Figure 4: Multilayer slit-film tape of the present invention
Figure 4A: Variations of the multilayer film of the present invention
Figure 5: Residual deposits on weaving machinery using multilayer slit film tapes of the present invention
List of parts:
1. Monolayer tape die 9. Web of slit film tapes
2. Extruder 10. Multilayer die
2A. Extruder EA 1OA. Feedblock
2B. Extruder EB 11. Mounting device
2C. Extruder EC 12. Channels
3. Water bath 13. Central layer B
4. Film slitting unit 14. External layer A
5. Holding unit 14A. External layer C
6. Hot air oven 15. Multilayer film
7. Stretching and annealing unit 16. Multilayer slit film tape
8. Winding device 17. Exposed edge Detailed description of the invention:
The invention accordingly concerns development of multilayer slit film tape containing inorganic fillers, preferably in a high proportion, and an extrusion line/machine for manufacturing such tapes.
In the conventional manufacturing line for making monolayer slit film tape as shown in Figure 2, a monolayer film is extruded through a monolayer tape die (1) mounted on a single extruder (2). The film passes through a series of devices such as a water bath (3), a film slitting unit (4), after which the web of slit film tapes (9) passes through a holding unit (5), a hot air oven (6), a stretching and annealing unit (7), and a winding device (8).
An apparatus to form a multilayer film (15) is disclosed in the first preferred embodiment of the present invention. The extruder and die system of the conventional monolayer tapelines has been inventively modified as shown in Figure 3. Rather than mounting the die on the extruder itself as in the case of conventional tapelines, the multilayer film (15) is extruded through a specially designed multilayer die (10) (also referred to as a flat die) that is independently mounted on a standalone mounting device (11) (not shown in figure), preferably a stand, and which is fed by a number of extruders (preferably 2A and 2B as shown in Figure 3, and optionally 2C as shown in Figure 3B, or more extruders) via suitably designed multichanneled feedblock (10A). As shown in Figure 3A, the feedblock (10A) arranges the incoming melt streams from two different extruders (2A and 2B) in the required order, balances the velocities of streams and combines the melt streams to form a multilayer molten composite which is compressed-fed to the flat die (10). For example, the finished configuration of the multilayer film (15) is ABA, the letters A denoting the external layers (14) between which the central layer B (13) is positioned. In some embodiments of the present inventions, a layer of type C, denoted as layer C (14A), and which is also categorized as an external layer, is incorporated. The flat die (10) designed specifically for casting a multilayer film (15) has internal geometry that addresses the layer order and ensures the uniformity of the cast multilayer film (15). The multilayer polymer composite fed to flat die (10) is then spread and thinned out to its desired final form which is the multilayer film (15). Figure 3 shows schematically, individual extruders (2A and 2B) feeding into the feedblock (10A) of the invention. A typical three layer film (15) (not shown in figures) coming out of the die (10), in the ABA format.
In the first preferred embodiment, an extruder EB (2B) extrudes the molten material that forms the central layer B (13) of the multilayer film (15) of the present invention and the two external layers A (14) are formed by a single second extruder EA (2A). The electronic controls for the extruders are designed such that both extruders (2A and 2B) operate synchronously to achieve the required feed rate. The extruder delivery or output is adjusted independently as per the requirement. The extruded multilayer film (15) cast through the die (10) of the present invention is then suitably cooled using a set of chill rollers or, more preferably by the water bath (3) method. The formed and cooled multilayer film (15) passes through a slitting device (4) and then through a drawing zone that consists of single stage stretching units or multi-stage stretching units. The slit film tapes (16) thus formed and drawn are annealed. After drawing and annealing process, the slit film tapes (16) are wound on the suitable package on the winding device (8).
In the second preferred embodiment of the invention, a multilayer slit film tape (16) is disclosed. The multilayer film (15) which is slit to create the multilayered slit film tapes (16) is made from a polymer matrix to which a filler material, preferably inorganic, and optionally other additives are added. The multilayer slit film tape (16) has preferably three layers of ABA configuration as shown in figure 4, comprising a central layer B (13) which is sandwiched between two external layers A (14). The polymer matrix of the central layer B (13) and external layers A (14) are selected from same or different poly olefin grade which are compatible with each other. More particularly, the polymer matrix is made from a material selected from the group comprising, polypropylene (PP), high density polyethylene (HDPE), linear low density polyethylene (LLDPE) and other similar polymeric material, or any combination thereof. The resin used is either virgin polymer, optionally blended with commercially available additives such as anti- fibrillating agent, ultra-violet stabilizer, color masterbatch, or recycled polymer and like.
In the second preferred embodiment, the central layer B (13) constitutes 20% to 80%, preferably more than 50%, by total weight of the tape (16) and balance is contributed by external layers A (14), preferably in equal proportions. The central layer B (13) consists of polymer resin, preferably polyolefin and filler, preferably inorganic, which is preferably in a higher proportion with the polymer. The proportion of the filler material in the layer B (13) is higher, preferably significantly higher than that of the external layers A (14).
The inorganic filler in the central layer B (13) is added in the form of the commercially available CCMBs such that the CCMB forms up to 10% to 90% (w/w) (w/w denoting proportion or percentage by weight), preferably 30% to 70% (w/w), more preferably up to 50% (w/w) of the total weight of the central layer B (13). It is evident that the central layer B (13) contains a high proportion of the inorganic filler. Each external layer A (14) contains a filler, most preferably in the form of CCMB, such that the CCMB forms up to 0% to 20% (w/w), preferably 3% to 20% (w/w), more preferably 3% to 8% by weight of the total weight of external layers A (14). It is evident that the external layers A (14) contain a low proportion of the inorganic filler. Both the central and external layers (13 and 14) may generally contain conventional additives, including but not limited to UV stabilizers, conductive compounds, processing aids, colour pigments and like.
The CCMB used in the present invention is sourced from any commercially available sources known to a person skilled in the art. The proportion of calcium carbonate in CCMB is of crucial importance. CCMBs containing CaCθ3 up to
85% w/w are available. The higher the proportion of CaCθ3 in the masterbatch, the lower the amount of CCMB material used in the present invention, to achieve a certain level of CaCθ3 in the final slit film tape (16). The preferred embodiments of the present invention use a CCMB containing approximately
70% to 80% w/w Of CaCO3.
The slit film tapes (16) of the present invention have a width between 0.8 mm to 160 mm, preferably between 2mm and 5mm; a thickness between 0.015 mm and 0.3 mm, preferably between 0.025mm and 0.1mm; and denier between 200 and 45,000, preferably between 400 and 2500.
In one embodiment of the invention, the total number of external layers (A and C) is three or more, in the formats ABCA ACABA, ACABAC, ABABC and so on (see Figure 4A). In this situation, the number of external layers on either side of the central layer B (13) is preferably same; alternatively the number of external layers on either side of the central layer B (13) is different; preferably there is at least one external layer on either side. The composition of layers A and B is the same as that disclosed in the second preferred embodiment. The layer C (14A), which is also categorized as an external layer, constitutes 10% to 80%, preferably less than 50% of the total weight of the multilayer film (15). In this embodiment, the external layers A and C have different composition; however, both contain low proportion of CCMB that is within the relevant ranges used in the second preferred embodiment.
In another embodiment of the present invention, the feedblock (10A) has sufficient number of channels (12) arranged in appropriate order such that the film (15) cast from the multilayer die (10) is in the format selected from a group comprising ABCA, ACABA, ACABAC, ABABC, and so on (see Figure 4A).
In another embodiment of the present invention, a third extruder EC (2C) is added to extrude the molten material that forms the external layers C (14A). The feedblock (10A) has sufficient number of channels (12) arranged in appropriate order such that the film (15) cast from the multilayer die (10) is in the format selected from a group comprising ABCA (see Figure 4A), ACABA, ACABAC, ABABC and so on.
One of the key features of the invention is the fact that the external layers (14 and
14A) that contain proportionately a very small amount of the little inorganic filler, form a protective cover to the central layer B (13) which contains higher proportion of the inorganic filler. This arrangement ensures that there's very little inorganic dust oozing out from the main surface of the multilayer slit film tapes (16) during downstream processing. Furthermore, it is observed that there is very little oozing of inorganic dust from the exposed edges (17) (see Figure 4) of the slit film tapes (16). As the slit film tapes (16) are drawn after slitting, their thickness reduces, whereby the inorganic filler gets further embedded and securely oriented within the resinous matrix of the tapes, thereby reducing the amount of loose inorganic filler that can potentially ooze out from the exposed edges of the tapes during their lifetime, particularly during downstream operations on the winders and looms.
In the third preferred embodiment of the present invention, a process of manufacturing a multilayer slit film tape containing high proportion of inorganic filler is disclosed. The process comprises the steps of:
Extruding a multilayer film (15) through a specially designed multilayer die (10) independently mounted on stand and fed by at least two different extruders (2 A and 2B, and optionally 2C as an additional extruder) via suitably designed feedblock (10A), such that, in the case of a three layered film, one of the said extruder forms the central layer B
(13) of said film and the remaining extruder forms the respective external layers (A or C), further wherein all extruders operate in synchronous manner as per the required feed rate, such that material feeding, heating and rate of extrusion are individually adjusted and controlled.
Cooling said film preferably using chill rollers or water bath (3) method. - Passing said film (15) through a slitting device (4) to make slit film tapes
(16) of predetermined width.
Drawing said slit film tapes (16) in a monoaxial stretch using single stage stretching units or multi-stage stretching units (7).
Annealing of the said slit film tapes (16).
Depending on the desired denier of the slit film tape and the material composition in the individual layer, the slit film tape (16) is stretched by total draw ratio between 3 and 20, preferably between 5 and 15, more preferably 10, even more preferably 4 to 7, so the tensile properties suitable for application of slit film tapes (16) are achieved.
The inventive multilayer slit film tapes (16) of the present invention are monoaxially stretched by passing them sequentially over a set of heated rollers and/or through a combination of heating device such as hot plates or convection heating device (6). The heating/stretching temperature is between 6O0C to 1750C depending on the material composition of the tapes. The speed of each successive roller is higher than that of predecessor roller, which results in the desired orientation/stretching of slit film tapes (16).
The stretched slit film tapes (16) are annealed, usually by using set of annealing rollers kept at ambient temperature. Alternatively, and preferably, heated annealing rollers operating at almost same speed as the final stretching roller are used following which the tapes (16) are cooled on a set of cooled annealing rollers operating at reduced surface speed than the stretching rollers. The final line speed is maintained between 100 to 650 m/min, preferably between 300 to 600 m/min. The formed multilayer slit film tapes are then formed into suitable packages using winding devices (8).
The multilayer slit film tapes (16) of the present invention are used to make fabric suitable for various applications such as woven sacks, large industrial sacks and packaging fabrics, geo-textiles, ropes and twines and miscellaneous industrial woven fabrics.
In another embodiment of the present invention, the multilayer slit film tapes (16) are fibrillated during or after the processing and then twisted and/or twined to produce desired yarn. In an embodiment of the present invention, the multilayer slit film has two layers. The final form of the tape (16) is either of AB, AC, or BC. Each of the two layers may use same or different polyolefin grade and have same or different proportion of filler, however, the overall composition of each of the two layers is different from each other.
In order that the invention is more readily understood, reference is made to the following examples which are intended to illustrate the invention, but not restrict or limit whatsoever the scope thereof.
Example 1
The multilayer slit film tape was prepared such that the central layer consisted of 80% w/w of Polypropylene (Reliance, 3 MFI) and 20% w/w of CCMB and each of the two external layers consisted of 96% w/w of Polypropylene (Reliance, 3 MFI) and 4% w/w CCMB, resulting in three layer slit film tape in which the layers of the ABA configuration are in the proportion 15%:70%:15% w/w. The extrusion temperature for all layers was 260 0C. The water bath temperature was 30 0C, total stretch ratio was 5.5, stretching oven temperature 150 0C & the annealing ratio 0.95 for the final line speed of 380 m/min. The multilayer slit film tape thus formed was of 900 denier and 3 mm width. It had a tenacity of 5.4 gpd and elongation of 25% at break. When a tubular woven fabric was made from this multilayer slit film tapes, very low dust was visible on the circular loom which was running at 820 picks per minute (ppm) speed.
Example 2
The multilayer slit film tape was prepared such that the central layer consisted of 76% w/w of Polypropylene (Reliance, 3 MFI), 22% w/w of CCMB and 2% w/w of a colour additive in the form of a red colour masterbatch; each of the two external layers consisted of 94% w/w of Polypropylene (Reliance, 3 MFI) and 4% w/w of CCMB and 2% w/w of a colour additive in the form of a red colour masterbatch, resulting in three layer slit film tape in which the layers of the ABA configuration were in the proportion 16%:68%:16% w/w. The extrusion temperature for all layers was 2600C. The water bath temperature was 280C, total stretch ratio 5.4, stretching oven temperature 1500C & the annealing ratio 0.94 for the final line speed of 360 m/min.
The multilayer slit film tape thus formed was of 900 denier and 3 mm width. It had a tenacity of 5.3 gpd and elongation of 24% at break. When a tubular woven fabric was made from this multilayer slit film tapes, very low dust was visible on the circular loom which was running at 810 picks per minute (ppm) speed. Example 3
The multilayer slit film tape was prepared such that the central layer consisted of
78% w/w of Polypropylene (Haldia, 3.4 MFI), 22% w/w of CCMB; each of the two external layers consisted of 98% of Polypropylene (Reliance, 3 MFI) and 2% w/w CCMB, resulting in three layer slit film tape in which the layers of the ABA configuration were in the proportion 18%: 64%: 18% w/w. The extrusion temperature for all layers was 2550C. The water bath temperature was 280C, total stretch ratio was 5.6, stretching oven temperature 150 0C & the annealing ratio 0.94 for the final line speed of 360 m/min.
The multilayer slit film tape thus formed of 900 denier and 3 mm width had a tenacity of 5.5 gpd and elongation of 24% at break. When a tubular woven fabric was made from this multilayer slit film tapes, low dust was visible on the circular loom which was running at 820 picks per minute (ppm) speed.
Example 4
The multilayer slit film tape was prepared such that the central layer consisted of
78% w/w of Polypropylene (Reliance, 3.4 MFI), 22% of CCMB and each of the twp external layers consisted of 96% w/w of Polypropylene (Reliance, 30 MFI) and 4% of CCMB, resulting in three layer slit film tape in which the layers of the ABA configuration were in the proportion 13%:74%:13% w/w. The extrusion temperature for the core/central layer was 265 0C and the external layers 245 0C. The water bath temperature was 26 0C, total stretch ratio 5.8, stretching oven temperature 152 0C & the annealing ratio 0.96 for the final line speed of 410 m/min.
The multilayer slit film tape thus formed was of 820 denier and 2.5 mm width. It had a tenacity of 5.4 gpd and elongation of 23% at break. When a tubular woven fabric was made from this multilayer slit film tapes, very low dust was visible on the circular loom which was running at 840 picks per minute (ppm) speed.
Example 5
The multilayer slit film tape was prepared such that the central layer consisted of 50% w/w of Polypropylene (Reliance, 3.4 MFI), 50% w/w of CCMB and each of the two external layers consisted of 96% w/w of Polypropylene (Reliance, 20 MFI) and 4% w/w of calcium MB, resulting in three layer slit film tape in which the layers of the ABA configuration were in the proportion 15%: 70%: 15% w/w. The extrusion temperature for the core/central layer was 265 0C and for the external layers 245 0C. The water bath temperature was 26 0C, total stretch ratio 5.7, stretching oven temperature 152 0C & the annealing ratio 0.96 for the final line speed of 390 m/min. The multilayer slit film tape thus resulted was of 800 denier and 2.5 mm width. It had a tenacity of 4.8 gpd and elongation of 22% at break. When a tubular woven fabric was made from this multilayer slit film tapes, low dust was visible on the circular loom which was running at 800 picks per minute (ppm) speed.
It is evident from the foregoing specification and accompanying drawings that all of the stated objects of the stated invention have been achieved.
The multilayer slit film tapes of the present invention have the following advantages over the monolayer slit films containing inorganic fillers:
Emits very little (practically nil) dust, this it poses very little or no danger to machine operators using the multilayer slit film tape in comparison to monolayer slit film tape with higher filler proportion.
Results in less wear & tear on moving parts of downstream processing machines (like Tape line, Winder and Loom) than the monolayer slit film tapes produced by conventional methods are used. The amount of the residual deposits created by the use of the multilayer slit film tapes of the present invention is far less than that generated by the tapes of prior art.
This is evident from the comparison of Figures 1 and 5. Figure 1 shows residual dust on a part of the circular loom that has in operation a monolayer tape of 820 denier, 2.5 mm width containing high proportion of inorganic filler which were CCMB 12% w/w. Figure 5 shows a part of the circular loom that has in operation the multilayer slit film tape of the present invention as per example 4 (820 denier, 2.5mm width & total CCMB more than 22% (w/w)).
Uses less amount of expensive additives as compared to the currently available monolayer slit film tapes. As in case of multilayer slit films the expensive additive is used only in the external layers, which amount to 20 to 50 % w/w of the total weight of the slit film tape.
Offers superior adhesion of coating layer (outer layers) on the fabric as the outer layers have very little amounts of the inorganic filler material
- Offers a multilayer slit film tape woven fabric on which the printing quality is of superior quality than that for the conventionally produced monolayer tapes.
While the above description contains much specificity, these should not be construed as limitation in the scope of the invention, but rather as an exemplification of the preferred embodiments thereof. It must be realized that modifications and variations are possible based on the disclosure given above without departing from the spirit and scope of the invention. Accordingly, the scope of the invention should be determined not by the embodiments illustrated, but by the appended claims and their legal equivalents. It is apparent from the foregoing discussion that the present invention comprises the following items:
1. A monoaxially drawn multilayer slit film tape comprising a polymer matrix and inorganic filler, said slit film tape made by slitting a multilayer film made of two or more layers, each of said layers preferably containing said inorganic filler.
2. A monoaxially drawn multilayer slit film tape as described in item 1 , wherein the total number of layers is at least three, wherein a central layer is cohesively bonded between at least two external layers, preferably at least one external layer positioned on each side of said central layer, wherein said external layers is of the type A or C.
3. A monoaxially drawn multilayer slit film tape as described in any of the preceding items, wherein preferably said central layer has greater proportion (w/w) of inorganic filler than in said external layers, and further wherein said filler is preferably in the form of a calcium carbonate masterbatch, wherein said masterbatch contains calcium carbonate in the proportion ranging between 25% (w/w) to 90% (w/w), preferably 50% (w/w) to 85% (w/w), more preferably 70% (w/w) to 80% (w/w).
4. A monoaxially drawn multilayer slit film tape as described any of the preceding items, wherein the proportion of said masterbatch in the central layer is in the range between 10% (w/w) to 90% (w/w), preferably 30% (w/w) to 70% (w/w), more preferably 50% (w/w) of the total weight of the central layer, and wherein the proportion of said filler in each of said external layers is in the range between 0% (w/w) to 20% (w/w), preferably 3% (w/w) to 20% (w/w) more preferably 3% (w/w) to 8% (w/w) by weight of the total material of external layer.
5. A monoaxially drawn multilayer slit film tape as described any of the preceding items, wherein the width of said slit film tapes is between 0.8 mm to 160 mm, preferably between 2 mm and 5 mm; and wherein the thickness of said slit film tapes is between 0.015 mm and 0.3 mm, preferably between 0.025 mm and 0.08 mm; and denier of said slit film tapes is between 200 and 45,000, preferably between 400 and 2500.
6. A monoaxially drawn multilayer slit film tape as described any of the preceding items, wherein the external layers, or central layer, or any of the layers contain additives selected from a group comprising UV stabilizers, conductive compounds, processing aids, colour masterbatch, or any other additives, or any combination thereof.
7. A monoaxially drawn multilayer slit film tape as described in any of the preceding items, wherein the polymeric material of the central layer (13) and external layers (14) are selected from same or different poly olefin grade or their blends.
8. A monoaxially drawn multilayer slit film tape as described any of the preceding items, wherein the polymeric material is from a material selected from the group comprising, polypropylene (PP), high density polyethylene (HDPE), linear low density polyethylene (LLDPE) and other similar polymeric material, or any combination thereof.
9. A monoaxially drawn multilayer slit film tape as described in any one of the preceding items, wherein the polymeric material in any layer is either virgin polymer or recycled polymer, optionally blend of recycled polymer with virgin polymer.
10. A process of making a monoaxially drawn multilayer slit film tape, wherein said process comprises the steps of:
extruding a multilayer film through an independently mounted flat die, said die being fed by at least two different extruders via suitably designed feedblock such that one of the said extruder forms the central layer of said film and the remaining extruder form respective external layers, further wherein all extruders operate in synchronous manner as per the required feed rate,
- cooling said film preferably using chill rollers or water bath method.
passing said film through a slitting device to make slit film tapes of predetermined width
drawing said slit film tapes in a monoaxial stretch using single stage stretching units or multi-stage stretching units
- annealing of the stretched slit film tapes. 11. A monoaxially drawn multilayer slit film tape, as described in item 6, and preferably manufactured using a process of item 8, wherein said slit film tape is stretched by total draw ratio between 3 and 20, preferably between 5 and 15 even more preferably 4 to 7.
12. An apparatus of making a monoaxially drawn multilayer slit film tape, wherein said apparatus comprises a system of at least two extruders, a feedblock, and a flat die, wherein a multilayer film is extruded through said flat die that is independently mounted on a standalone mounting device, preferably a stand, and which said die is fed by said multiple number of extruders via said feedblock which combines the melt streams to form a multilayer molten composite which is fed to said flat die, and wherein said flat die has the internal geometry to ensure that the cast film produced has the desired format selected from the group comprising ABCA, ACABA, ACABAC, ABABC, and so on.
13. An apparatus of making a monoaxially drawn multilayer slit film tape, said tape being as described in item 8, wherein said extruders are three or more in number.
14. A monoaxially drawn multilayer slit film tape as described in item 6, wherein said tape is in the format selected from a group comprising ABCA, ACABA, ACABAC, ABABC and so on
15. A woven flat or tubular fabric prepared from the multilayer slit film produced as per any one of the preceding items. 6. Products made using the fabric prepared from multilayer slit film tape as described in item 15 preferably sacks, packaging fabrics and the like.

Claims

Claims:
1. A monoaxially drawn multilayer slit film tape comprising a polymer matrix and inorganic filler, said slit film tape made by slitting a multilayer film made of two or more layers, each of said layers preferably containing said inorganic filler.
2. A monoaxially drawn multilayer slit film tape as claimed in claim 1, wherein the total number of layers is at least three, wherein a central layer is cohesively bonded between at least two external layers, preferably at least one external layer positioned on each side of said central layer, wherein said external layers is of the type A or C.
3. A monoaxially drawn multilayer slit film tape as claimed in claim 2, wherein preferably said central layer has greater proportion (w/w) of inorganic filler than in said external layers, and further wherein said filler is preferably in the form of a calcium carbonate masterbatch, wherein said masterbatch contains calcium carbonate in the proportion ranging between 25% (w/w) to 90%
(w/w), preferably 50% (w/w) to 85% (w/w), more preferably 70% (w/w) to 80% (w/w).
4. A monoaxially drawn multilayer slit film tape as described in claim 3, wherein the proportion of said masterbatch in the central layer is in the range between 10% (w/w) to 90% (w/w), preferably 30% (w/w) to 70% (w/w), more preferably 50% (w/w) of the total weight of the central layer, and wherein the proportion of said filler in each of said external layers is in the range between 0% (w/w) to 20% (w/w), preferably 3% (w/w) to 20% (w/w) more preferably 3% (w/w) to 8% (w/w) by weight of the total material of external layer.
5. A monoaxially drawn multilayer slit film tape as described in claim 4, wherein the width of said slit film tapes is between 0.8 mm to 160 mm, preferably between 2 mm and 5 mm; and wherein the thickness of said slit film tapes is between 0.015 mm and 0.3 mm, preferably between 0.025 mm and 0.08 mm; and denier of said slit film tapes is between 200 and 45,000, preferably between 400 and 2500.
6. A monoaxially drawn multilayer slit film tape as claimed in claim 5, wherein the external layers or central layers, or any of the layers may contain additives selected from a group comprising UV stabilizers, conductive compounds, processing aids, colour masterbatch, or any other additives, or any combination thereof.
7. A monoaxially drawn multilayer slit film tape as claimed in any one of the preceding claims, wherein the polymer material of the central layer (13) and external layers (14) are selected from same or different poly olefin grade or their blends.
8. A monoaxially drawn multilayer slit film tape as claimed in claim 7 wherein the polymer material is from a material selected from the group comprising, polypropylene (PP), high density polyethylene (HDPE), linear low density polyethylene (LLDPE) and other similar polymeric material, or any combination thereof.
9. A monoaxially drawn multilayer slit film tape as claimed in any one of the preceding claims, wherein the polymeric material in any layer is either virgin polymer or recycled polymer; optionally blend of recycled polymer with virgin polymer.
10. A process of making a monoaxially drawn multilayer slit film tape, wherein said process comprises the steps of:
extruding a multilayer film through an independently mounted flat die, said die being fed by at least two different extruders via suitably designed feedblock such that one of the said extruder forms the central layer of said film and the remaining extruder form respective external layers, further wherein all extruders operate in synchronous manner as per the required feed rate,
cooling said film preferably using chill rollers or water bath method,
passing said film through a slitting device to make slit film tapes of predetermined width,
drawing said slit film tapes in a monoaxial stretch using single stage stretching units or multi-stage stretching units,
annealing of the stretched slit film tapes.
11. A monoaxially drawn multilayer slit film tape, as claimed in claim 6, and preferably manufactured using a process of claim 8, wherein said slit film tape is stretched by total draw ratio between 3 and 20, preferably between 5 and 15 even more preferably 4 to 7.
12. An apparatus of making a monoaxially drawn multilayer slit film tape, wherein said apparatus comprises a system of at least two extruders, a feedblock, and a flat die, wherein a multilayer film is extruded through said flat die that is independently mounted on a standalone mounting device, preferably a stand, and which said die is fed by said multiple number of extruders via said feedblock which combines the melt streams to form a multilayer molten composite which is fed to said flat die, and wherein said flat die has the internal geometry to ensure that the cast film produced has the desired format selected from the group comprising ABCA, ACABA, ACABAC, ABABC and so on.
13. An apparatus as claimed in claim 8, wherein said extruders are three or more in number.
14. A monoaxially drawn multilayer slit film tape as claimed in claim 6, wherein said tape is in the format selected from a group comprising ABCA, ACABA, ACABAC, ABABC and so on.
15. A woven flat or tubular fabric prepared from the multilayer slit film produced as per any one of the preceding claims.
16. Products made using the fabric prepared from multilayer slit film tape as claimed in claim 15 preferably sacks, packaging fabrics and the like.
PCT/IB2009/053687 2008-08-27 2009-08-21 A novel mono-axially oriented multilayer slit film tape yarn, and an apparatus and a process to make the same WO2010023606A1 (en)

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