Casting web for flexible tube containers with longitudinal side seams

Abstract

A one-step multilayer non-laminated tube with longitudinal side seams useful for packaging applications and having a combination of oxygen barrier properties and resilience properties includes a core layer having an oxygen barrier material such as ethylene-vinyl alcohol. A composition of the invention comprising a layer structure is disclosed for obtaining a one-step casting web for manufacturing longitudinal side seam pipes.

Description

Technical Field

[0001] The present invention is in the field of material science and relates to a cast web for a flexible tube container having longitudinal side seams. Summary of the invention

[0002] The invention relates to a cast web material for longitudinal side-seamed tube packaging which is oxygen and water vapor-proof, and a method for manufacturing the packaging material.

[0003] The multilayer cast laminate tube container comprises a core layer having an oxygen barrier material such as ethylene vinyl alcohol. A first adhesive resin (tie) layer is disposed between a first outer layer and the core layer. A second adhesive resin layer is disposed between the core layer and the second outer layer. A first additional layer is disposed between the first outer layer and the first adhesive resin layer. A second additional layer is disposed between the second outer layer and the second adhesive resin layer. The cast web is prepared by an extrusion cast sheet production line.

[0004] Cast web tube packaging with longitudinal side seams provides a good barrier to oxygen and water vapor. Background Art

[0005] The longitudinal side seam tube is used to protect the freshness, hygiene, and shelf life of the product. The tube also provides a convenient and durable packaging. Conventional longitudinal side seam webs are made by multiple processes, first blow molding, then lamination process to obtain laminated webs.

[0006] U.S. Patent Application No. 2003 / 0129434A1 shows a multilayer thermoformable plastic film comprising: an outer layer comprising a blend of very low density polyolefin, ethylene vinyl acetate and a compatibilizer; a middle layer comprising a mixture of nylon copolymer and amorphous nylon; a bottom layer comprising a polyolefin or an ionomeric polymer; and at least one adhesive bonding the top layer, the middle layer and the bottom layer together.

[0007] Cast film / sheet as a multilayer film / sheet is obtained by passing the polymer melt through a die, followed by cooling and winding via a chill roll. Polyolefin films or sheets are widely used for packaging tubular products. Multilayer cast film inventions for several applications have been prepared, such as tray packaging, oxygen barrier films, printed films, food packaging, adhesive films, industrial and consumer packaging. Various processes are described in US 6,713,189 B2, US2005 / 0096448 A1, US8,815,360 B2, US2015 / 0258755 A1, US2,018 / 0154617 A1 and US 9,994,003 B2.

[0008] CN 106079765 A discloses a retort-resistant cast film including 11 layers from top to bottom: a first PA (polyamide) layer, a second adhesive layer, and third to eleventh PP layers. The cast film can withstand retort at a high temperature of 120°C and is suitable for packaging products such as meat products that require high-temperature sterilization.

[0009] CN 107160797 A discloses a multi-layer co-extruded cast film, which includes a viscous layer, a high barrier layer, a waterproof layer, a buffer layer, a color developing layer and an antistatic anti-sticking layer from the inside to the outside. The invention has excellent properties in terms of viscous test, barrier property, water resistance test, tensile strength and elongation.

[0010] CA2752306 discloses plastics that prevent the spread of odors. The multilayer film is composed of a moisture-proof polymer layer composed of high-density polyethylene and an optional odor counteractant, the odor counteractant being an aromatic unsaturated carboxylic acid ester, wherein the unsaturated structure is conjugated to both the aromatic ring and the carbonyl part of the carboxylic acid ester; and an odor barrier polymer layer composed of polyamide; and optionally, an adhesive layer between the moisture-proof polymer layer and the odor barrier polymer layer. The plurality of film layers are composed of a multilayer cast film.

[0011] CN 1294198 C shows a multilayer structure with excellent barrier properties, transparency, stretchability, flexibility, bending resistance and interlayer adhesion.

[0012] It has been found that the above-mentioned packaging does not provide a one-step cast tube with longitudinal side seams. The packaging tube container produced according to the present invention is suitable for filling and packaging of highly viscous or pasty compositions, for example. The lead time for producing cast web laminate tubes has been shortened from 30 days to 15 days. The present invention aims to provide a film / sheet made of a polymer composition, which gives the film / sheet good mechanical properties, stiffness and tensile strength. The melt index of the polymer composition measured by ASTM D1238 can be various values ​​in the range of 0.5-20g / 10 minutes. Various additives may be present, such as stabilizers, lubricants, fillers, colorants, waxes, etc. The amount of additives is generally less than 10% by weight relative to the polymer. DETAILED DESCRIPTION

[0013] The term "polyolefin" refers to a polymer containing repeating units derived from an olefin, for example, a polyalphaolefin such as polypropylene and / or polyethylene.

[0014] "Polypropylene" refers to a polyolefin containing repeating units derived from propylene, such as a polypropylene homopolymer and / or a polypropylene copolymer, wherein at least 50 wt%, preferably 85 wt% by number of repeating units are derived from polypropylene monomers.

[0015] "Polyethylene" refers to a polyolefin containing repeating units derived from ethylene, such as a polyethylene homopolymer and / or a polyethylene copolymer, wherein at least 50% by weight, preferably 85% by weight, of the number of repeating units are ethylene monomers.

[0016] "Copolymer" refers to a polymer containing repeating units from at least two different monomers (preferably, for example, olefins such as ethylene, propylene, butene, etc.). Propylene copolymers or propylene-based polymers contain at least two different monomers, wherein the repeating units are derived from propylene monomers in an amount greater than 50 wt%, preferably greater than 85 wt%.

[0017] The present invention provides a process for producing 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 a feed block to form a cast film; (c) cooling the cast film using one or more cooling rollers; (d) optionally, annealing the cast film and / or treating the cast film using a corona treatment.

[0018] The outer layer comprises high-density polyethylene resin and other polyethylene resins to provide rigidity, sealing ability and impact resistance. High-density polyethylene (HDPE) is sometimes selected to improve stress crack resistance and rigidity. The crystallinity of HDPE can be about 85 weight %. Low-density polyethylene (LDPE) is usually selected for purposes such as enhancing dart impact or easy processing. The crystallinity of LDPE can be about 30 weight %. Linear low-density polyethylene (LLDPE) is usually used to enhance toughness, tear strength and impact strength. The crystallinity of LLDPE can be about 55 weight %. Based on the gross weight of the outer layer, the blend usually comprises about 30 weight % to 90 weight %, preferably about 60 weight % to 90 weight %, and most preferably 73 weight % of high-density polyethylene.

[0019] Based on the total weight of the outer layer, the blend generally comprises about 10 wt % to 70 wt %, preferably about 10 wt % to 40 wt %, and most preferably about 25 wt % of the metallocene linear low density polyethylene. Based on the total weight of the outer layer, the blend generally comprises most preferably about 2 wt % of a processing aid. The processing aid helps to make the polymer flow smoothly during extrusion and to make the thickness of each polymer layer in the multilayer thermoplastic film uniform.

[0020] In embodiments herein, the LDPE present may have a density of 0.915-0.935 g / cc. LDPE may also be used to refer to "high pressure ethylene polymer" or "highly branched polyethylene" and may include branched polymers partially or fully homopolymerized or polymerized in autoclave or tubular reactors.

[0021] Therefore, the present invention for constituting the cast web laminate is an extrusion lamination technology by extruding five layers having an outer layer, an adhesive resin layer, an EVOH layer, an adhesive resin layer and an inner layer.

[0022] The bonding interface or bonding resin layer in the present invention refers to an anhydride-modified low-density polyethylene resin containing anhydride. The term "adhesive layer" or "bonding resin layer". The thickness of the bonding interface is generally about 5 to 25 microns, preferably about 10 microns.

[0023] The ethylene content of the ethylene-vinyl alcohol copolymer (EVOH) of the inner polyethylene layer is 27 mol% to 44 mol%.

[0024] The inner layer can be used as a sealant. The inner layer preferably comprises a heat-sealable polymer material, and more preferably can use very low density polyethylene, or other ethylene alpha-olefin copolymers including what is commonly known as linear low density polyethylene or very low density polyethylene. In the heat-sealable layer, a small amount of suitable additives such as anti-caking agents can be added to improve the handling and usability of the packaging material of the present invention.

[0025] A colorant such as the oxide, titanium dioxide (TiO2) may be used in the outer layer.

[0026] Embodiments of the present invention are provided:

[0027] [1] A cast web for a flexible tube container having longitudinal side seams, comprising at least five material layers selected from at least two polyolefin layers, at least two adhesive layers and one barrier layer, wherein, optionally, the stacking arrangement of the layers is as follows:

[0028] The first layer is a first polyolefin,

[0029] The second layer is the first adhesive,

[0030] The third layer is the barrier layer.

[0031] The fourth layer is the second adhesive,

[0032] The fifth layer is a second polyolefin.

[0033] Another embodiment of the present invention is provided:

[0034] [2] The cast web according to [1], comprising:

[0035] The first layer is a first polyolefin layer having a density of 0.90-0.97 g / cc polyolefin,

[0036] The second layer is a first adhesive having an adhesive resin to provide inter-layer adhesion,

[0037] The third layer is a barrier layer having a barrier resin,

[0038] The fourth layer is a second adhesive having an adhesive resin to provide inter-layer adhesion,

[0039] The fifth layer is a second polyolefin having a density of 0.90-0.97 g / cc polyolefin,

[0040] Wherein, the total thickness of the cast web is in the range of 150-350 microns.

[0041] Another embodiment of the present invention is provided:

[0042] [3] A cast web for a flexible tube container having longitudinal side seams, comprising at least 7 material layers selected from at least 4 polyolefin layers, at least 2 adhesive layers and 1 barrier layer, wherein, optionally, the stacking arrangement of these layers is as follows:

[0043] The first layer is a first polyolefin,

[0044] The second layer is a second polyolefin,

[0045] The third layer is the first adhesive,

[0046] The fourth layer is the barrier layer.

[0047] The fifth layer is the second adhesive,

[0048] The sixth layer is the third polyolefin,

[0049] The seventh layer is a fourth polyolefin.

[0050] Another embodiment of the present invention is provided:

[0051] [4] The cast web according to [3], comprising:

[0052] The first layer is a first polyolefin layer having a density of 0.90-0.97 g / cc polyolefin,

[0053] The second layer is a second polyolefin layer having a density of 0.90-0.97 g / cc polyolefin,

[0054] The third layer is a first adhesive layer having an adhesive resin to provide inter-layer adhesion,

[0055] The fourth layer is a barrier layer having a barrier resin,

[0056] The fifth layer is a second adhesive layer having an adhesive resin to provide inter-layer adhesion,

[0057] The sixth layer is a third polyolefin layer having a density of 0.90-0.97 g / cc polyolefin,

[0058] The seventh layer is a fourth polyolefin layer having a density of 0.90-0.97 g / cc polyolefin,

[0059] Wherein, the total thickness of the cast web is in the range of 150-350 microns.

[0060] Another embodiment of the present invention is provided:

[0061] [5] The cast web as described in any one of [1] to [4], wherein the polyolefin layer is a polyolefin optionally selected from LDPE, LLDPE, HDPE, polyethylene copolymers, polypropylene copolymers and / or mixtures thereof. Another embodiment of the present invention is provided:

[0062] [6] The cast web as described in [5], wherein the total thickness of the polyolefin layer is in the range of 15-100 μm.

[0063] Another embodiment of the present invention is provided:

[0064] [7] The cast web according to any one of [1] to [4], wherein the adhesive resin layer is an anhydride-modified low-density polyethylene resin containing an acid anhydride.

[0065] Another embodiment of the present invention is provided:

[0066] [8] The cast web as described in [7], wherein the thickness of the adhesive resin layer is in the range of 5 to 30 μm.

[0067] Another embodiment of the present invention is provided:

[0068] [9] The cast web according to any one of [1] to [4], wherein the barrier layer is a copolymer of ethylene and vinyl alcohol.

[0069] Another embodiment of the present invention is provided:

[0070]

[10] The cast web as described in [9], wherein the thickness of the barrier layer is in the range of 5-30 μm.

[0071] Cast web extrusion processes can be used to produce barrier webs. Extrusion processes for both five-layer and seven-layer web production focus on systems engineering, die design, web product, and economies of scale. Surface modification techniques for substrates after the extrusion casting operation require a combination of corona, flame, ozone, and atmospheric plasma equipment to optimize adhesion to printing inks.

[0072] A conventional laminate tube forming machine is used to form a hollow tube with longitudinal side seams. A conventional tube head machine is used to form the shoulder and seal with the hollow tube.

[0073] In the following examples we show that one-step cast webs with longitudinal side seams have web properties comparable to laminated webs.

[0074] Examples 1-3: Preparation of five-layer cast webs by cast film line. Three different webs are described in Table 1.

[0075] 80 wt% HDPE and 20 wt% propylene and ethylene copolymer were loaded into the hopper of the outer skin casting layer A. 65 wt% HDPE, 20 wt% propylene and ethylene copolymer and 15 wt% polyolefin plastomer were loaded into the hopper of the inner skin casting layer D. Casting layer B was loaded with 100 wt% adhesive resin. Casting layer C was loaded with 100 wt% EVOH.

[0076] Table 1

[0077]

[0078] Example 4: A seven-layer cast web was prepared using the formulation shown in Table 2.

[0079] Table 2 describes the cast webs obtained by the coextrusion casting line, including the composition of the polymers, the thickness of each layer in the multi-layer cast web.

[0080] Table 2

[0081]

[0082] Example 5 (comparative example): external LLDPE film 135 / LLDPE extruded film 15 / adhesive resin 10 / EVOH 15 / adhesive resin 10 / LLDPE extruded film 15 / internal LLDPE film 50

[0083] The inner polyethylene film having a thickness of 50 microns was laminated to the outer polyethylene film having a thickness of 135 μm by coextrusion of hot-melt LLDPE, adhesive resin and EVOH resin. In the coextrusion lamination process, a five-layer molded film having a structure of LLDPE extruded film 15 μm / adhesive resin 10 μm / EVOH 15 μm / adhesive resin 10 μm / LLDPE extruded film 15 μm was obtained.

[0084] Melt index was measured at 190°C and 2.16 kg load according to ASTM D-1238. The values ​​are reported in g / 10 min. Density measurements were prepared within one hour of sample pressing according to ASTM D792.

[0085] According to ASTM standards, the web samples are placed under conditions of 23°C (+ / -2°C) and 50% RH (+ / -5) for at least 40 hours. According to ASTM standards, standard test conditions are 23°C (+ / -2°C) and 50% RH (+ / -5). For example, the following physical properties of the web are measured:

[0086] Tensile strength, weight % elongation and 1 weight % secant modulus were measured using ASTM D-882. Web MD (longitudinal) and CD (cross-direction) secant modulus and tensile strength at break were measured using an Instron universal tester according to ASTM D882-10. The reported secant modulus value is the average of five measurements in each direction. Seal strength was measured using ASTM F904 to monitor seal properties. The opacity of plastic sheets was measured using a Tobias densitometer. Tube roundness or ovality was measured by using the following measurements / calculations:

[0087] Ellipticity = ((D max -D sho ) / D sho )100

[0088] Ovality ±6 weight%

[0089] D max = Maximum diameter of the tube at the open end

[0090] D sho = Tube diameter at shoulder

[0091] Table 3

[0092]

[0093] The physical properties of Examples 4-5 are comparable and can be used for tube forming processes. As shown in the thickness range, the web thickness using cast web is more controllable compared to multi-step laminated webs. Compared to laminated webs, the rigidity of the yield tensile strength of cast webs is smaller. Casting technology is needed to use a resin grade that is softer and more flexible than multi-step laminated webs. The elongation values ​​show the same trend as the tensile strength of cast webs and laminated webs. There is no significant difference in the sealing strength, opacity and tube roundness of cast webs and laminated webs. Examples 4 and 5 are all effectively formed laminated tubes, and then headers and caps are added. Improved plastic resin technology also plays an important role in the successful development of plastic resin formulations for obtaining the required physical properties of packaging tubes.

[0094] Best Mode for Carrying Out the Invention

[0095] As described above in the detailed description of the present application.

Claims

1. A cast web for a flexible tube container having longitudinal side seams, comprising at least 5 material layers selected from at least 2 polyolefin layers, at least 2 adhesive layers and 1 barrier layer, wherein: Optionally, the layers are stacked in the following arrangement: The first layer is a first polyolefin layer, The second layer is the first adhesive layer, The third layer is the barrier layer. The fourth layer is the second adhesive layer, The fifth layer is a second polyolefin layer.

2. The cast web of claim 1, comprising: The first layer is a first polyolefin layer having a density of 0.90-0.97 g / cc polyolefin, The second layer is a first adhesive layer having an adhesive resin to provide inter-layer adhesion, The third layer is a barrier layer having a barrier resin, The fourth layer is a second adhesive layer having an adhesive resin to provide inter-layer adhesion, The fifth layer is a second polyolefin layer having a density of 0.90-0.97 g / cc polyolefin, Wherein, the total thickness of the cast web is in the range of 150-350 microns.

3. A cast web for a flexible tube container having longitudinal side seams, comprising at least 7 material layers selected from at least 4 polyolefin layers, at least 2 adhesive layers and 1 barrier layer, wherein: Optionally, the layers are stacked in the following arrangement: The first layer is a first polyolefin layer, The second layer is a second polyolefin layer, The third layer is the first adhesive layer, The fourth layer is the barrier layer. The fifth layer is the second adhesive layer, The sixth layer is the third polyolefin layer, The seventh layer is a fourth polyolefin layer.

4. The cast web of claim 3, comprising: The first layer is a first polyolefin layer having a density of 0.90-0.97 g / cc polyolefin, The second layer is a second polyolefin layer having a density of 0.90-0.97 g / cc polyolefin, The third layer is a first adhesive layer having an adhesive resin to provide inter-layer adhesion, The fourth layer is a barrier layer having a barrier resin, The fifth layer is a second adhesive layer having an adhesive resin to provide inter-layer adhesion, The sixth layer is a third polyolefin layer having a density of 0.90-0.97 g / cc polyolefin, The seventh layer is a fourth polyolefin layer having a density of 0.90-0.97 g / cc polyolefin, Wherein, the total thickness of the cast web is in the range of 150-350 microns.

5. The cast web according to any one of claims 1 to 4, wherein The polyolefin layer is a polyolefin optionally selected from LDPE, LLDPE, HDPE, polyethylene copolymers, polypropylene copolymers and / or mixtures thereof.

6. The cast web according to claim 5, wherein: The total thickness of the polyolefin layer is in the range of 15-100 microns.

7. The cast web according to any one of claims 1 to 4, wherein The adhesive resin layer is an anhydride-modified low-density polyethylene resin containing an acid anhydride.

8. The cast web according to claim 7, wherein The thickness of the adhesive resin layer is in the range of 5-30 microns.

9. The cast web according to any one of claims 1 to 4, wherein The barrier layer is a copolymer of ethylene and vinyl alcohol.

10. The cast web according to claim 9, wherein The thickness of the barrier layer is in the range of 5-30 microns.

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