HIGH-BARRIER POLYMER BLEND COMPOSITIONS

Abstract

A polymer blend composition comprising 78-92% by weight of a homopolymer or copolymer of ethylene, 3-10% by weight of a polyamide homopolymer, 5-10% by weight of maleic anhydride grafted polyethylene (MAgPE) and 0-2% by weight of antistatic compound on the total weight of the polymer blend composition, in combination with suitable additives.

Claims

1. A polymer blend composition comprising 78-92% by weight of a homopolymer or copolymer of ethylene, 3-10% by weight of a polyamide homopolymer, 5-10% by weight of maleic anhydride grafted polyethylene (MAgPE) and 0-2% by weight of antistatic compound on the total weight of the polymer blend composition, in combination with suitable additives.

2. The polymer blend composition according to claim 1, wherein the homopolymer or copolymer of ethylene is a high density polyethylene having a density ranging between 0.945-0.955 g/cm.sup.3.

3. The polymer blend composition according to claim 2, wherein the high density polyethylene is selected from the group consisting of high density polyethylene homopolymers, high density polyethylene/hexene copolymers and mixtures thereof.

4. The polymer blend composition according to claim 1, wherein the polyamide homopolymer is polyamide 6.

5. The polymer blend composition according to claim 1, wherein the antistatic compound has a resistance R.sub.0 comprised between 10.sup.5<R.sub.0<10.sup.12.

6. The polymer blend composition according to claim 5, wherein the antistatic compound is selected from the group consisting of polyamide/polyether block amide mixtures.

7. A multi-layer container comprising a barrier layer made of the polymer blend composition according to claim 1, and at least one further layer comprising HDPE.

8. The multi-layer container according to claim 7, wherein said at least one further layer contains 70-100% by weight of HDPE, 0-20% by weight of an antistatic compound and 0-10% by weight of additives.

9. The multi-layer container according to claim 7, wherein said at least one further layer comprises a first layer and a second layer, said multi-layer container consisting of three layers: an inner layer corresponding to said first layer and made of high density polyethylene, an intermediate layer corresponding to said barrier layer, an outer layer corresponding to said second layer and made of high density polyethylene.

10. The multi-layer container according to claim 7, wherein said at least one further layer comprises a first layer and a second layer, said multi-layer container consisting of three layers: an inner layer corresponding to said first layer made of high density polyethylene, an intermediate layer corresponding to said barrier layer, an outer layer corresponding to said second layer comprising 70-90% by weight of HDPE, 5-20% by weight of an antistatic compound and 1-10% by weight of additives.

11. The multi-layer container according to claim 7, wherein said barrier layer comprises 0-40% of regrinded material from said barrier layer and from said at least one further layer.

Description

DESCRIPTION OF THE FIGURES

DETAILED DESCRIPTION OF THE INVENTION

Multi-Layer Container

[0019] The object of the present invention is a polymer blend composition comprising 78-92% by weight of a homopolymer or copolymer of ethylene, 3-10% by weight of a polyamide homopolymer, 5-10% by weight of maleic anhydride grafted polyethylene (MAgPE) and 0-2% by weight of antistatic compound on the total weight of the polymer blend composition, in combination with suitable additives. The homopolymer or copolymer of ethylene is preferably a high density polyethylene.

[0020] Said high density polyethylene employed for the aim of the present invention has a density ranging preferably between 0.945-0.955 g/cm.sup.3.

[0021] Even more preferably said high density polyethylene is selected from the group consisting of high density polyethylene homopolymers, high density ethylene/hexene copolymers or mixtures thereof.

[0022] Suitable high density polyethylene polymers are even more preferably characterised by: [0023] a melt flow index ranging between 2-12 g/10 min at 190 C./21.6 kg, [0024] a yield strength ranging between 23-28 MPa when stretched at 50 mm/min, at 23 C. (ISO 527-1-2) [0025] an elongation ranging between 500-700% (ISO 527-2) at break, [0026] a flexural modulus ranging between 850-1300 MPa [0027] an environmental stress cracking greater than 500 hours, preferably between 1000 and 2000 hours (ASTM D1693)

[0028] Suitable high density polyethylene that can be used within the aim of the present invention are those available on the market with the commercial name of Lupolen 4261 AGUV 60005 (Basell Polyolefines), Rigidex HM4560UA (Ineos Polyolefins), Polyethylene HDPE 49080 UV (Total petrochemicals).

[0029] The polyamide homopolymer used in the polymer blend composition of the present invention is preferably polyamide 6.

[0030] Within the scope of the present invention, suitable polyamide 6 are more preferably characterised by: [0031] a density ranging between 1.12 and 1.16 g/cm.sup.3, [0032] a notched impact strength ranging between 5 and 7 KJ/m.sup.2 Charpy at 23 C., [0033] a melt volume flow rate ranging between 43 and 47 cm.sup.3/l0 min at 275 C./21.6 kg, [0034] a melting point ranging between 220 and 224 C., [0035] a moisture content ranging between 0.03% and 0.1%.

[0036] Within the purposes of the present invention, a suitable polyamide 6 polymer is for example the one available on the market with the commercial name of Grilon F 50 nat 6368 (EMS-GRIVORY|a unit of EMS-CHEMIE AG).

[0037] The polymer blend composition of the present invention further comprises Maleic Anhydride grafted Polyethylene (MAgPE), a modified polyethylene, functionalised with the anhydride of the unsaturated carboxylic maleic acid.

[0038] In a preferred embodiment, the MAgPE suitable for the polymer blend composition of the present invention has a density ranging between 0.958-0.962 g/cm.sup.3, a melt flow rate ranging between 1-3 g/10 min at 190 C./2.16 kg, a melting point ranging between 130-137 C., and a maleic anhydride graft level ranging between 0.9-1.2% by weight on the total weight of the MAgPE.

[0039] Within the aim of the present invention, a suitable MAgPE is the one available in the market with the commercial name of DuPont Fusabond E MB100D (Dupont Packaging & Industrial Polymer).

[0040] An antistatic compound is furthermore contained in the polymer blend composition according to the present invention.

[0041] As used within the context of the present invention, an antistatic compound is defined as a material having a resistance R.sub.0 comprised between 10.sup.5<R.sub.0<10.sup.12.

[0042] Suitable antistatics employed within purposes of the present invention are most preferably selected from the group consisting of polyamide-polyether block amide mixtures.

[0043] In general sense a polyether block amide (polyetheresteramide) or PEBA is a block copolymer obtained by polycondensation of a carboxylic acid polyamide (PA6, PA11, PA12) with polyoxyalkylene glycol (Polytetramethylene glycol PTMG; PEG).

[0044] PEBA is a high performance thermoplastic elastomer, displaying lower density among TPE, superior mechanical and dynamic properties (flexibility, impact resistance, energy return, fatigue resistance) as well as being able to keep these properties at low temperature (lower than 40 C.).

[0045] Polyamide/polyether block amide mixtures are polymeric systems comprising polyamide and said thermoplastic PEBA elastomers.

[0046] Among the preferred polyamide/polyether block amide mixtures, most preferably the one employed in the purpose of the present invention is the polymeric system known with the trade name of IRGASTAT P18, produced from Ciba Specialty Chemicals, and providing for a permanent antistatic effect.

[0047] In another preferred embodiment, the polymer blend composition disclosed in the present application can eventually comprise other additives, such as colour, UV protection-agents (antiUV), compatibilisers, nucleation agents.

[0048] The aforementioned polymer blend composition, in view of the specific selection of components and concentrations, allows the production of plastic containers for the transport of hazardous substances displaying superior barrier properties, chemical and impact resistance when compared to the plastic containers of the state of the art.

[0049] Within the scope of the present invention, by hazardous substance is meant any of the substances belonging to classes 3-6, 8-9 provided by The Recommendations on the Transport of Dangerous Goods, said classes corresponding respectively to Flammable Liquids; Flammable solids, substances liable to spontaneous combustion, substances which, on contact with water, emit flammable gases;

[0050] Oxidizing substances and organic peroxides; Toxic and Infectious substances; Corrosive substances; Miscellaneous dangerous substances and articles, including environmentally hazardous substances. (http://www.unece.org/fileadmin/DAM/trans/danger/publi/unrec/rev19/Rev19e_Vol_I.pdf).

[0051] The polymer blend composition of the present invention is employed to manufacture inner containers for Intermediate Bulk Containers (IBC) for storage and collection of liquid or gel hazardous substances.

[0052] The polymer blend composition of the present invention is particularly advantageous for the production of plastic containers suitable for example for the storage and collection of petroleum-based products, aromatic solvents, aliphatic solvents, ketones, kerosenes, alcohols and commercially based products such as paints, pesticides and herbicides that are dissolved in such solvents.

[0053] The present invention also relates to a multi-layer container comprising a barrier layer made of the polymer blend composition according to the present invention and at least one further layer comprising HDPE.

[0054] Advantageously, the barrier layer according to the present invention provides good barrier properties for hydrocarbon materials even more preferably against the following test materials: Trichloroethylene (Flash Point (FP) 89.6 degC), Cyclohexanone (FP 44 degC), Hexane (FP 26 degC), Propanol (FP 22 degC)) & Xylene (FP 30 degC).

[0055] Even more preferably, said at least one further layer contains 70-100% by weight of HDPE, 0-20% by weight of an antistatic compound, 0-10% by weight of additives, said additives being preferably selected among compatibilisers, colours and antiUV.

[0056] In a first preferred embodiment, the multi-layer container according to the present invention is constituted by three layers: the barrier layer made of the polymer blend composition according to the present invention; a first layer made of HDPE; a second layer made of HDPE.

[0057] The three layers comprise an inner layer, an outer layer and an intermediate layer arranged between the inner layer and the outer layer. The inner layer is designed to contact the hazardous substance stored in the multi-layer container.

[0058] In said first preferred embodiment, said first layer is the inner layer, said second layer is the outer layer, and said barrier layer is the intermediate layer, arranged between said first layer and second layer.

[0059] In a second preferred embodiment, the multi-layer container according to the present invention is constituted by three layers: the barrier layer made of the polymer blend composition according to the present invention; a first layer made of HDPE; a second layer comprising 70-90% by weight of HDPE, 5-20% by weight of an antistatic compound, preferably Irgastat P18, and 1-10% by weight of additives, preferably 4% of compatibilizer, 1% antiUV and, optionally, a colour masterbatch.

[0060] Even more preferably said compatibilizer is Lotader AX 8900.

[0061] In said second preferred embodiment, said first layer is the inner layer, said second layer is the outer layer and said barrier layer is the intermediate layer, arranged between the first and the second layers.

[0062] Advantageously, the presence of MAgPE in the polymer blend composition according to the present invention provides for a good adhesion between the three layers, without the need to introducing an additional adhesive layer.

[0063] Even more preferably, said barrier layer of said multi-layer container comprises 0-40% by weight of regrinded material from said barrier layer and from said at least one further layer.

[0064] More precisely, according to a preferred embodiment, said barrier layer comprises 0-40% by weight of regrinded material from said barrier layer, said first layer and said second layer.

[0065] Whether present, said antistatic compound comprised within said at least one further layer is preferably the same antistatic compound comprised in the polymer blend composition according to the present invention.

[0066] The multi-layer container according to the present invention preferably has a volume ranging between 800 L and 1200 L, in view of the aforementioned volumes, a total weight ranging between 14 kg and 21 kg, wherein the outer layer has a weight preferably ranging between 2 kg and 3 kg, the inner and intermediate layers have, singularly, a weight preferably ranging between 6 kg and 9 kg.

[0067] Another object of the present invention is a method for producing the multi-layer container, according to the present invention, said method comprising the steps of: [0068] i. Dry blending an homopolymer or copolymer of ethylene, a polyamide and maleic anhydride grafted polyethylene; [0069] ii. Melting the dry blended polymer mass according step i. in an extruder; [0070] iii. Coextruding said dry blended polymer mass together with at least one further layer comprising HDPE, to form a multi-layer parison; [0071] iv. Blowing the multi-layer parison in a mold to obtain a multi-layer container; [0072] v. Trimming the leftover material of the multi-layer parison extending beyond the mold; [0073] vi. Recycling said leftover material into the following production cycle.

[0074] Preferably, the leftover material obtained from each production cycle of the aforementioned method is added to phase i. and dry blended together with the other polymers.

Examples of Multilayer Container

[0075] With an explicative but not limitative purpose, we provide herewith two examples of the polymer blend composition employed for the production of the multi-layer container according to the present invention.

Example 1

[0076] Multi-layer container according to the present invention, characterised by a total weight of 17.5 kg, a volume of 1000 L and a thickness of 1.5 mm-2.5 mm.

TABLE-US-00001 Inner Outer Layer Intermediate Layer (w/w) Layer (w/w) (w/w) Total % (w/w) 42.5% 42.5% 15% Grilon F 50 0.0% 6.02% 0.0% nat 6368 DuPontTM Fusabond 0.0% 8.43% 0.0% E MB100D Irgastat P18 0.0% 0.00% 0.0% Rigidex HM4560UA 100.0% 85.54% 100.0%

Example 2

[0077] Multi-layer container according to the present invention, characterised by a total weight of 17.5 kg, a volume of 1000 L and a thickness of 1.5 mm-2.5 mm.

TABLE-US-00002 Inner Outer Layer Intermediate Layer (w/w) Layer (w/w) (w/w) Total % (w/w) 42.5% 42.5% 15% Grilon F 50 nat 6368 0.0% 6.02% 0.0% DuPontTM Fusabond 0.0% 8.43% 0.0% E MB100D Lotader AX 8900 0.0% 0.36% 5.0% Irgastat P18 0.0% 1.08% 15.0% BF UV 1610 0.0% 0.07% 1% Rigidex HM4560UA 100.0% 84.00% 79.0%

Single-Layer Container

[0078] A further polymer blend composition, a single-layer container obtained from said polymer blend composition and a method for the production of the same, which do not form part of the present invention, are hereinafter described according to the following clauses: [0079] 1. A polymer blend composition comprising 68-87% by weight of a homopolymer or copolymer of ethylene, 5-15% by weight of a polyamide homopolymer, 8-17% by weight of maleic anhydride grafted polyethylene (MAgPE), in combination with suitable additives. [0080] 2. The polymer blend composition according to clause 1, wherein the homopolymer or copolymer of ethylene is a high density polyethylene having a density ranging between 0.945-0.955 g/cm.sup.3. [0081] 3. The polymer blend composition according to clause 2, wherein the high density polyethylene is selected from the group consisting of high density polyethylene homopolymers, high density polyethylene/hexene copolymers and mixtures thereof. [0082] 4. The polymer blend composition according to anyone of clauses 1-3, wherein the polyamide homopolymer is polyamide 6. [0083] 5. The polymer blend composition according to anyone of clauses 1-4, wherein said suitable additives are selected from the group consisting of antistatics, UV protection-agents, compatibilisers, nucleation agenta, colours. [0084] 6. A single-layer container consisting of one layer made of the polymer blend composition according to anyone of clauses 1 to 4. [0085] 7. The single-layer container according to clause 6, wherein said single-layer container comprises 0-40% of regrinded material from said one layer.

[0086] It is described herewith a polymer blend composition not belonging to the present invention and comprising 68-87% by weight of a homopolymer or copolymer of ethylene, 5-15% by weight of a polyamide homopolymer, 8-17% by weight of maleic anhydride grafted polyethylene (MAgPE), in combination with suitable additives.

[0087] The homopolymer or copolymer of ethylene is preferably a high density polyethylene. Said high density polyethylene has a density preferably ranging between 0.945-0.955 g/cm.sup.3.

[0088] Even more preferably said high density polyethylene is selected from the group consisting of high density polyethylene homopolymers, high density ethylene/hexene copolymers or mixtures thereof.

[0089] Suitable high density polyethylene hydrocarbon polymers are even more preferably characterised by: [0090] a melt flow index ranging between 2-12 g/10 min at 190 C./21.6 kg, [0091] a yield strength ranging between 23-28 MPa when stretched at 50 mm/min, at 23 C. (ISO 527-1-2) [0092] an elongation ranging between 500-700% (ISO 527-2) at break, [0093] a flexural modulus ranging between 850-1300 MPa [0094] an environmental stress cracking greater than 500 hours, preferably between 1000 and 2000 hours.

[0095] Suitable homopolymer or copolymer of ethylene that can be used for the polymer blend are those available on the market with the commercial name Lupolen 5261 Z (Basell Polyolefines), Marlex HXM 50100 (Chevron Philips Chemical Company), HDPE 56020 S (Total refining & Chemicals), RIGIDEX HM5420XPH (INEOS Olefines and Polymers Europe), Polyethylene HDPE 49080 UV (Total petrochemicals).

[0096] The polyamide homopolymer used in the aforementioned polymer blend is preferably polyamide 6.

[0097] Suitable polyamide 6 suitable for the polymer blend composition are more preferably characterised by: [0098] a density ranging between 1.12 and 1.16 g/cm.sup.3, [0099] a notched impact strength ranging between 5 and 7 KJ/m.sup.2 Charpy at 23 C., [0100] a melt volume flow rate ranging between 43 and 47 cm.sup.3/10 min at 275 C./21.6 kg, [0101] a melting point ranging between 220 and 224 C., [0102] a moisture content ranging between 0.03% and 0.1%.

[0103] More preferably, suitable polyamide 6 is for example the one available on the market under the trade name of Grilon F 50 nat 6368 (EMS-GRIVORY|a unit of EMS-CHEMIE AG).

[0104] The polymer blend composition further comprises Maleic Anhydride grafted Polyethylene (MAgPE), a modified polyethylene, functionalised with the anhydride of the unsaturated carboxylic maleic acid.

[0105] In a preferred embodiment, the MAgPE suitable for the polymer blend composition of the present invention has a density ranging between 0.958-0.962 g/cm.sup.3, a melt flow rate ranging between 1-3 g/10 min at 190 C./2.16 kg, a melting point ranging between 130-137 C., and a maleic anhydride graft level ranging between 0.9-1.2% by weight on the total weight of the MAgPE.

[0106] A suitable MAgPE is for example the one available in the market under the commercial name of DuPont Fusabond E MB100D (Dupont Packaging & Industrial Polymer).

[0107] In another preferred embodiment, the polymer blend composition can eventually comprise other additives, such as antistatics, colours, UV protection-agents (antiUV), compatibilisers, nucleation agents.

[0108] The aforementioned polymer blend composition, in view of the specific selection of components and concentrations, allows the production of plastic containers for the transport of hazardous substances displaying superior barrier properties, chemical and impact resistance when compared to the plastic containers of the state of the art.

[0109] The polymer blend composition is employed to manufacture monolayer containers, for storage and collection of liquid or gel hazardous substances.

[0110] The polymer blend composition is particularly advantageous for the production of plastic containers suitable for example for the storage and collection of petroleum-based products, aromatic solvents, aliphatic solvents, ketones, kerosenes, alcohols and commercially based products such as paints, pesticides and herbicides that are dissolved in such solvents.

[0111] Advantageously the barrier layer according to the present invention provides good barrier properties for hydrocarbon materials even more prefebably against the following test materials: Trichloroethylene (Flash Point (FP) 89.6 degC), Cyclohexanone (FP 44 degC), Hexane (FP 26 degC), Propanol (FP 22 degC)) & Xylene (FP 30 degC).

[0112] A single-layer container consisting of one layer made of the above mentioned polymer blend composition, not according to the present invention, is also hereinafter disclosed.

[0113] The single-layer container preferably has a volume ranging between 1 L and 30 L and, in relation to the aforementioned volumes, a thickness ranging between 0.7 mm and 4.0 mm.

[0114] Said single-layer container is preferably produced by a method comprising the following steps: [0115] a. Dry blending an homopolymer or copolymer of ethylene, a polyamide and maleic anhydride grafted polyethylene; [0116] b. Melting the dry blended polymer mass according step i. in an extruder; [0117] c. Extruding said dry blended polymer mass to form a single-layer parison; [0118] d. Blowing the single-layer parison in a mold to obtain a single-layer container; [0119] e. Trimming the leftover material of the single-layer parison container extending beyond the mold; [0120] f. Recycling said leftover material into the following production cycle.

[0121] Preferably, the leftover material obtained from each production cycle of the aforementioned method is added to phase a. and dry blended together with the other polymers.

[0122] More precisely, according to a preferred embodiment, said single-layer container comprises 0-40% by weight of regrinded material from said one layer.

Examples of Monolayer Container

[0123] With an explicative but not limitative purpose, we provide herewith two examples of the polymer blend composition employed for the production of the single-layer container not according to the present invention.

Example 1

[0124] Single-layer container not according to the present invention, characterised by a total weight of 15.5 kg, a volume of 1000 L and a thickness of 1.4-2.2 mm.

TABLE-US-00003 Single-Layer container Total % 100% Grilon F 50 5.00% nat 6368 DuPontTM 8.33% Fusabond E MB100D HDPE 49080 UV 86.67%

Example 2

[0125] Single-layer container not according to the present invention, characterised by a total weight of 270 g, a volume of 5 L and a thickness of 0.7-2.0 mm.

TABLE-US-00004 Single-Layer container Total % 100% Grilon F 50 14.00% nat 6368 DuPontTM Fusabond 16.00% E MB100D Marlex HXM 50100 70.00%