FIELD OF THE INVENTION

This present invention is in the field of materials science and relates to a casted web for flexible tube container with longitudinal side seam.

SUMMARY OF THE INVENTION

This invention relates to casted web for longitudinal side seam tube packaging having barrier to oxygen and water vapor, and the method of manufacturing of packaging material.

A multi-layered casted laminate tube container comprises a core layer having an oxygen barrier material such as ethylene vinyl alcohol. The first tie layer is disposed between the first outer layer and the core layer. The second tie layer is disposed between the core layer and the second outer layer. The first additional layer is disposed between the first outer layer and the first tie layer. The second additional layer is disposed between the second outer layer and the second tie layer. The cast web was prepared by extrusion cast sheet line.

The casted web tube packages with longitudinal side seam provided good barrier to oxygen and water vapor.

BACKGROUND ART

Longitudinal side seam tube is used to protect the product for freshness, hygiene, shelf life. Tubes also provide a convenient and durable package. Conventional longitudinal side seam web production is made from multi-step process starting from blown film and lamination process to obtain laminated web.

US patent application number 2003/0129434 Al showed a multi-layer thermoformable plastic film comprises of outer layer comprising a blend of a very low-density polyolefin, ethylene vinyl acetate, and a compatibilizer; an intermediate layer comprising a mixture of nylon copolymer and an amorphous nylon; a bottom layer comprising a polyolefin or ionomeric polymer; and at least one adhesive that bonds said top, intermediate, and bottom layers together.

Cast film/sheet where is a multilayer film/sheet is obtained by passing a polymer melt through a die, followed by cooling via one chill roll and winding. Polyolefin films or sheets are widely used in packaging tube products. Multi-layer cast film inventions for several application aspects have been prepared such as pallet wrapping, oxygen barrier film, printing film, food packaging, cling film, industrial and consumer packaging. Various processes are described in US patent number 6,713,189 B2, US 2005/0096448 Al, US 8,815,360 B2, US 2015/0258755 Al, US 2018/0154617 Al, and US 9,994,003 B2. CN 106079765 A disclosed a retortable cast film including sequentially eleven layers from top to bottom: a first PA (polyamide) layer, a second adhesive layer, a third to eleventh PP layers. The cast film can tolerate retorting at a high temperature of 120 Celsius, is suitable for use in packaging the products requiring high-temperature sterilization, such as meat foods.

CN 107160797A revealed the multilayer co-extrusion cast film comprising a viscous layer, a high barrier layer, a waterproof layer, a buffer layer, a chromogenic layer, and an antistatic and anti-sticking layer which is sequentially from inside to outside. The invention has excellent properties in a viscous test, barrier property, a water resistance test, tensile strength and elongation rate.

CA 2752306 revealed a malodor transmission-resistant plastic. A multilayer film consists of a moisture-resistant polymeric layer consisting of high-density polyethylene and, optionally, a malodor counteractant that is an aromatic unsaturated carboxylic ester wherein the unsaturation is conjugated to both the aromatic ring and the carbonyl group portion of the carboxylic ester; and an odor-barrier polymeric layer consisting of polyamide; and optionally, a binding layer between said moisture-resistant polymeric layer and said odor-barrier polymeric layer. The plurality of film layers consists of a multilayer cast film.

CN 1294198C showed a multilayer structure with superior barrier properties, transparency, stretchability, flexibility, flexing resistance and interlayer adhesiveness.

It has been found that the above-described packages do not provide one-step casted tube with longitudinal side seam. A package tube container produced in accordance with the present invention is suitable, for example, for the filling and packaging of highly viscous or pasty compositions. Leadtime to produce casted web laminate tubes have been shortened from 30 days to 15 days. The present invention is to provide the film/sheet from a polymer composition that yields a film/sheet having good mechanical properties, stiffness, and tensile strength. The melt index of polymer compositions, determined by ASTM DI 238, may have various values, for instance between 0.5-20 g/10 min. Various additives may be present, such as, stabilizers, lubricants, fillers, colorants, waxes, etc. The quantity of additives to polymer will usually lower than 10% w/w.

DETAILED DESCRIPTION

The term “polyolefin” means a polymer containing recurring units derived from olefin, e.g., poly-a olefin such as polypropylene and/or polyethylene. “Polypropylene” means a polyolefin containing propylene-derived units, e.g., polypropylene homopolymer and/or polypropylene copolymer wherein at least 50% w/w, preferably 85% w/w, by the number of the recurring units are derived from polypropylene monomer.

“Polyethylene” means a polyolefin containing recurring ethylene-derived units, e.g., polyethylene homopolymer and/or polyethylene copolymer wherein at least 50% w/w, preferably 85% w/w, by the number of the recurring units are ethylene monomer.

“Copolymef ’ means a polymer containing recurring units derived from at least two different monomers, preferably, e.g., olefins such as ethylene, propylene, butenes, etc. A propylene copolymer or propylene-based polymer contains at least two different monomers wherein > 50% w/w, preferably > 85% w/w, by the number of the recurring units are derived from propylene monomer.

The invention provides a process to produce a cast film, the process comprising: (a) melt extruding at least one first polyethylene polymer to form a molten polymer; (b) passing the molten polymer through a T-die and feed block to form the cast film; (c) cooling the cast film using one or more chill rolls; (d) optionally, annealing the cast film and/or treating the cast film with a corona treatment.

Outer layer comprises of high-density polyethylene resin and other polyethylene-based resin to provide stiffness, seal ability, and impact resistance. High density polyethylene (HDPE) is occasionally selected for increasing stress crack resistance and stiffness. The crystallinity of HDPE might be approximately 85% w/w. Low density polyethylene (LDPE) is normally selected for purpose such as enhance dart impact or easy processability. The crystallinity of LDPE might be approximately 30% w/w. Linear low-density polyethylene (LLDPE) is generally used for enhancing toughness, tear strength, and impact strength. The crystallinity of LLDPE might be approximately 55% w/w. The blend typically comprises about 30% w/w to 90% w/w, preferably about 60% w/w to 90% w/w, most preferably 73% w/w, of a high-density polyethylene, based on the total weight of outer layer.

The blend typically comprises about 10% w/w to 70% w/w, preferably about 10% w/w to 40% w/w, most preferably about 25% w/w, of a metallocene linear low-density polyethylene, based on the total weight of outer layer. The blend typically comprises most preferably about 2% w/w, of a processing aid, based on the total weight of outer layer. The processing aid assists during extrusion to allow smooth polymer flow and uniform thickness of the various polymer layers in the multi-layered thermoplastic film. In embodiments herein, the LDPE present may have a density of 0.915-0.935 g/cc. The LDPE may also be used to refer “high pressure ethylene polymer” or “highly branched polyethylene”, and may include branched polymers that are partly or entirely homopolymerized or polymerized in autoclave or tubular reactors.

Accordingly, this invention used to constitute casted web laminated sheet is an extrusion lamination technique by extruding five layers with outer, tie, EVOH, tie, and inner layer.

Bonding interfaces or tie layer in this invention means an anhydride-modified, low-density polyethylene resins containing anhydride. The term “adhesive layer”, or “tie layer”. The bonding interfaces typically have a thickness of about 5 to 25 microns, preferably about 10 microns.

The ethylene-vinyl alcohol copolymer (EVOH) of the inner polyethylene layer has ethylene content from 27 mol% to 44 mol%.

The inner layer is useful as a sealant. It preferably comprises a heat sealable polymeric material and more preferably a very low-density polyethylene, or other ethylene alpha-olefin copolymers including those commonly designated as linear low-density polyethylene or very low- density polyethylene may be used. In the heat sealable layer, small amounts of suitable additives can be added such as anti-blocking agents to enhance the handling and usefulness of the packaging material of the present invention.

A coloring agent may be used in the outer layer, such as oxide, titanium dioxide (TiCb).

An embodiment of this invention is provided:

[1] A casted web for flexible tube container with longitudinal side seam comprising at least 5 layers of materials which selected from at least 2 layers of polyolefin, at least 2 layers of adhesion, and a layer of barrier, wherein optionally arrangement of overlaying these layers is as follows: first layer is a first polyolefin, second layer is a first adhesion, third layer is a barrier, fourth layer is a second adhesion, fifth layer is a second polyolefin.

Another embodiment of this invention is provided:

[2] The casted web according to [1], comprising: said first layer is the first polyolefin layer having a polyolefin with density 0.90-0.97 g/cc, said second layer is the first adhesion having a tie to provide high interlayer adhesion, said third layer is the barrier having a barrier resin, said fourth layer is the second adhesion having a tie to provide high interlayer adhesion, said fifth layer is the second polyolefin having a polyolefin with density 0.90-0.97 g/cc, wherein said casted web having total thickness range is 150-350 micron.

Another embodiment of this invention is provided:

[3] A casted web for flexible tube container with longitudinal side seam comprising at least 7 layers of materials which selected from at least 4 layers of polyolefin, at least 2 layers of adhesion, and a layer of barrier, wherein optionally arrangement of overlaying these layers is as follows: first layer is the first polyolefin, second layer is the second polyolefin, third layer is the first adhesion, fourth layer is the barrier, fifth layer is the second adhesion, sixth layer is the third polyolefin, seventh layer is the fourth polyolefin.

Another embodiment of this invention is provided:

[4] The casted web according to [3], comprising: said first layer is the first polyolefin layer having the polyolefin with density 0.90-0.97 g/cc, said second layer is the second polyolefin layer having the polyolefin with density 0.90-0.97 g/cc, said third layer is the first adhesion having the tie to provide high interlayer adhesion, said fourth layer is the barrier having the barrier resin, said fifth layer is the second adhesion having the tie to provide high interlayer adhesion, said sixth layer is the third polyolefin having the polyolefin with density 0.90-0.97 g/cc, said seventh layer is the fourth polyolefin having the polyolefin with density 0.90-0.97 g/cc, wherein said casted web having total thickness range is 150-350 micron.

Another embodiment of this invention is provided:

[5] The casted web according to any one of [l]-[4], wherein said polyolefin layer is a polyolefin which is optionally selected comprising LDPE, LLDPE, HDPE, polyethylene copolymer, polypropylene copolymer and/or mixture thereof. Another embodiment of this invention is provided:

[6] The casted web according to [5], wherein said polyolefin having total thickness range is 15-100 micron.

Another embodiment of this invention is provided:

[7] The casted web according to any one of [l]-[4], wherein said tie layer is an anhydride-modified, low-density polyethylene resins containing anhydride.

Another embodiment of this invention is provided:

[8] The casted web according to [7], wherein said tie layer having thickness range 5-30 micron.

Another embodiment of this invention is provided:

[9] The casted web according to any one of [l]-[4], wherein the barrier layer is copolymer of ethylene and vinyl alcohol.

Another embodiment of this invention is provided:

[10] The casted web according to [9], wherein said barrier layer having thickness range 5-30 micron.

The cast web extrusion process can be used to produce barrier web. Both extrusion process for 5-layer web and 7-layer web production are made with the focus on system engineering, die design, web products and economies of scale. Surface modification technique to a substrate after extrusion casting operation requires combinations of corona, flame, ozone and atmospheric plasma equipment to optimize adhesion to the printing ink.

The conventional laminated tube forming machine is used to form hollow tube with longitudinal side seam. The conventional tube heading machine is used to form shoulder part and sealing with hollow tube.

In the example below, we showed that one-step cast web with longitudinal side seam has comparable web properties to the laminated web.

Example 1-3: Cast web 5 layer was prepared by cast film line. Three different webs are described in Table 1.

80 % w/w HDPE and 20 % w/w copolymer of propylene and ethylene were loaded into the hopper of outer skin cast layer A. 65 % w/w HDPE and 20 % w/w copolymer of propylene and ethylene and 15% w/w polyolefin plastomer were loaded into the hopper of inner skin cast layer D. The cast layer B was loaded with 100 % w/w tie. Cast layer C was loaded with 100 % w/w EVOH. Table 1.

Example 4: Cast web 7 layers was prepared using formula as shown in the Table 2.

Table 2 described cast web by co-extrusion casting line, including polymer compositions, thickness of each layer in the multi-layer cast web. Table 2

Example 5 (Comparative example): Outer LLDPE filml35/LLDPEextrul5/TielO/EVOH15/ TielO/LLDPE extrul5/Inner LLDPE film50

Inner polyethylene film with a thickness of 50 micron was laminated to a 135p-thick outer polyethylene film by using co-extrusion of hot-melted LLDPE, Tie, and EVOH resins. During coextrusion laminating process, five-layered film forming is obtained with a structure of LLDPE extru 15 p/Tie 10 p/E V OH 15 p/Ti e 10 p/LLDPE extru 15 p .

Melt index was measured in accordance to ASTM D-1238 at 190 Celsius and 2.16 kg load. Their values were reported in g/10 min. Density measurement was prepared according to ASTM D792 within one hour of sample pressing.

The web samples were conditioned for at least 40 hours at 23 °C (+/- 2°C) and 50%RH (+/- 5) as per ASTM standards. Standard testing conditions were 23 °C (+/- 2°C) and 50%RH (+/- 5) as per ASTM standards. The following physical properties of web were measured such as: Tensile strength, % w/w elongation and 1% w/w secant modulus were measured using ASTM D-882. The web MD (Machine Direction) and CD (Cross Direction) secant modulus and tensile strength at break were measured with an Instron universal tester according to ASTM D882- 10. The reported secant modulus value was the average of five measurements in each direction. Seal strength was measured to monitor the sealing property using ASTM F904. Opacity of plastic sheet was measured by using Tobias densitometer. Tube roundness or ovality is measured by using the measurement/calculation below:

Ovality ⁼ ((Dmax-Dsho)/Dsho) ^x 100

Ovality ± 6% w/w

Dmax = maximum diameter at open end of tube

D _S ho = tube diameter at the shoulder

Table 3.

The physical properties of example 4-5 are comparable and capable for tube forming process. The web thickness using cast web was better controllable than multi-step laminated web as shown in the thickness range. The tensile strength at yield of cast web were less rigid than laminate web. Cast process is needed to use more soft and flexible resin grade than multi-step laminate web. Elongation values have shown the same trend as tensile strength of cast web and laminate web. Seal strength, opacity and tube roundness of cast and laminate webs were not significantly different. Both example 4 and 5 were effectively formed laminated tube and subsequently heading and capping. The improved plastic resin technology also plays an important role for the success of the development of plastic resin formulation to obtain the desired physical properties of the packaging tube.

BEST MODE FOR CARRYING OUT THE INVENTION

As stated above in the detailed description of this application.