GAS-SEALED MATERIAL

Abstract: The present invention concerns a gas-sealed material, containing polyolefin and polyvinyl alcohol. The material is manufactured by mixing in molten state 1 to 99 per cent by weight of polyolefin and 99 to 1 per cent by weight of internally plasticized vinyl alcohol polymer, and optionally 1 to 15 per cent by weight of a plasticizing agent.

Description: Gas-sealed material The present invention concerns a gas-sealed material and products 5 containing gas-sealed material. In particular, the present invention concerns a gas-sealed material containing polyolefine and polyvinyl alcohol, and products containing the same. Polyolefins are widely used, for instance, in packaging industry for -JQ manufacturing various film products. Advantages of polyolefins are in particular appropriate strength and water resistance properties. Among the drawbacks may be mentioned permeability to certain gases and liquids, concerning particularly oxygen and hydrocarbon dis¬ solvents. Therefore, the usability of polyolefin films is limited to -|5 packaging certain substances, such as food stuffs, in which minor oxygen permeability is required. It is customary to use in packaging industry multiple layer film structures in which materials of different layers are selected to 20 serve a given purpose. Therefore, such multiple layer structures may contain layers which form a good barrier against gases, such as oxygen, and layers which provide other properties for the product, such as strength properties. In addition, multiple layer structures may contain other layers which generate for instance adhesion between 25 different layers. Products of this kind are, however, expensive to manufacture. Polyvinyl alcohol is one of such polymers which has a low oxygen permeability property. Said property has most often been utilized in 30 olefin-vinyl alcohol random-mixed polymers and in olefin-vinyl alcohol segment-mixed polymers. It is also known in the art to manufacture products containing polyolefin and polyvinyl alcohol in the form of mixtures, which have a low oxygen permeability and which therefore are exceedingly appropriate for manufacturing e.g. packaging films. 35 In the Finnish patent application No. 87-5772 is disclosed a mixture of polyolefin and polyvinyl alcohol, moreover containing optionally plasticizers. When polyolefin and polyvinyl alcohol are mixed in 1 molten state, a mixture is obtained which is co posed of two phases, a continuous phase and a dispersed phase. When the diameter of the particles in the dispersed phase is small enough, totally transpar¬ ent films are obtained. The mixing is usually carried out in a 5 separate compounding phase prior to the extrusion of the end product. When the PVA in the mixture of polyolefin and PVA establishes a continuous phase, a good sealing is provided in the product, for instance oxygen sealing, and the product is bright and stable, in -JO spite of two phases, both in molten and in solid state, and it is easy to soften by adding plasticizers. Although polyolefin-PVA-mixtures are provided with good oxygen sealing properties in dry circumstances, in moist circumstances their oxygen -|5 sealing property reduces significantly, so that they are sensitive to moisture. In addition, when mixtures of polyolefins and PVA are mixed in molten state, partial dissolution of PVA and colouring of the product take place. When plasticizers are used, their stability in the mixture is not as good as possible because of which migration 20 °f plasticizers takes place in the product. One more drawback in conventional PE/PVA mixtures is that the viscosity of the product is not high enough, and that the mechanical properties of the films manufactured therefrom are not adequate. 25 The object of the present invention is a polyvinyl alcohol containing polyolefin, in which the moisture sensitivity of the product to oxygen sealing is reduced, the lightness of the product has increased, and the migration of the plasticizers has lessened. 30 As taught by the invention, it has been surprisingly found that when certain internally plasticized polyvinyl alcohol copolymers are mixed in molten state with polyolefins, such products are obtained which have a lighter colour and the oxygen sealing gained in which is considerably less sensitive to moisture than in using conven- 35 tional polyvinyl alcohol. In addition, in the material of the in¬ vention no plasticizer migration occurs, or it occurs only to a very low degree. 1 Therefore, the invention concerns a gas-sealed material containing polyolefin and polyvinyl alcohol. The gas-sealed material of the invention is characterized in that it is produced by mixing 1 to 99 per cent by weight of polyolefin and 99 to 1 per cent by weight of 5 internally plasticized vinyl alcohol polymer in molten state, and optionally 1 to 15 per cent by weight of a plasticizer. The term 'internally plasticized vinyl alcohol polymer'•refers to a vinyl alcohol polymer which contains polyglycol groups (polyether -|0 groups) or other groups plasticizing polyvinyl alcohol in the side chains thereof. Said plasticizer groups are connected into a chain by copolymerizing, branching or by means of reactive compounding. One of such internally plasticized polyvinyl alcohols is Vinex polymer (trade name, Air Products and Chemicals Inc.), in which for comonomer -|5 is used an ester of methacrylic acid and polyethylene glycol. Said internally plasticized vinyl alcohol polymers may be manu¬ factured, for instance in the manner as disclosed in the US. patent No. 4,708,999. Said patent presents that the product is provided 20 with good oxygen sealing and that it Is appropriate for cast, injection moulding and extrusion products, and that it is characterized by good water solubility and therefore, it is particu¬ larly well appropriate for manufacturing films which are required to possess water solubility. 25 The vinyl alcohol polymer used in the polyolefin/polyvinyl alcohol mixture of the invention is advantageously such in which in the poly(alkyleneoxy)ester derivative for use as a comonomer the alkylene of the alcohol component is ethylene or propylene, and the acid 30 component is acrylic acid or methacrylic acid. Said modified vinyl alcohol polymers may be manufactured, for instance, by polymerizing vinyl acetate monomer and poly(alkyleneoxy)acrylate comonomer, and hydrolyzing the copolymer thus obtained in order to produce an in¬ ternally plasticized vinyl alcohol polymer. 35 The amount of the internally plasticized vinyl alcohol polymer in the polyethylene-polyvinyl alcohol mixture of the invention may be 1 in the range of from 1 to 99 per cent by weight, preferably in the range of from 10 to 90 per cent by weight. In smaller quantities, the effect on oxygen permeability is, however, smaller, while the colour of the product may, nevertheless, be maintained good. In some 5 instance, it may be preferable to substitute part of the internally plasticized vinyl alcohol polymer used in the gas-sealed material for unmodified polyvinyl alcohol if the purpose of the product allows. The polyolefin present in the gas-sealed material of the invention -|0 may be based on homopolymers or copolymers of the olefins. There¬ fore, it may be low density polyethylene (LDPE) , medium density polyethylene or high density polyethylene (HDPE) , polypropylene or polybutene. The polyolefin may also be a copolymer of ethylene to¬ gether with other olefins, such as propylene, butene, hexene and -j5 octene. The polyolefin may also be an olefin-ester copolymer, such as ethylene-vinyl acetate copolymer, ethylene-acrylate-ester copolymer or ethylene-methacrylate ester copolymer, or it may be a thermoplastic olefin-based elastomer, such as EP or EPD rubber. 20 The polyolefin in the process according to the invention may also be a homopolymer or a copolymer of the above-mentioned olefins which has been modified with the aid of carboxylic acid. To such a modified olefin polymer is copolymerized or grafted 0.1 to 10 per cent by weight of carboxylic acid. The carboxylic acid may comprise any 25 unsaturated carboxylic acid or carboxylic acid anhydride which can be grafted or copolymerized in polyolefin. Examples of such acids are, for instance, acrylic acid, methacrylic acid, maleic acid fumaric acid, itaconic acid, crotonic acid, sorbic acid, and anhydrides of the afore-mentioned acids. In grafting or in copolymerizing one or 30 several above acids may be used. The polyolefin grafted or copolymer¬ ized with carboxylic acid may also be a mixture containing a poly¬ olefin modified in the manner described above, and un unmodified polyolefin. 35 The quantity of the polyolefin in the gas-sealed material of the invention may be in the range from 1 to 99 per cent by weight, but preferably in the range from 10 to 90 per cent by weight of the quantity of the entire mixture. The gas-sealed material of the invention may further contain 1 to 15 per cent by weight of plasticizers. A plasticizer may be selected from any material used for polyvinyl alcohol plasticizer or a mixture thereof. As examples of such may be mentioned ethylene glycol, tri- methylene glycol, propylene glycol, triethylene glycol, neopenthyl glycol and 2,2,4-trimethyl-l,3-pentane diol and sorbitol. A preferable plasticizer is glycerol. The gas-sealed polyolefin/PVA mixture of the invention may be manu¬ factured mixing the polyolefin component, the vinyl alcohol/polymer component and a potential plasticizer component in a melt mixer simultaneously as a dry mixture, premixed in solid or molten state, or then various components are added separately. The addition of plasticizers may also be carried out after the compounding. Also such procedure may be adopted in which a plasticizer is added in the PVA component, whereby the advantage is gained that the entire mixture need not be plasticized. From the polyolefin/PVA mixture of the invention various products may be prepared by combining the mixture with polyolefins, other plastics or other materials, such as fibre-based materials. Multiple layer products may be manufactured by coextrusion, (co)extrusion coating, (co)extrusion lamination, adhesion lamination, or using other techniques, and these production procedures may also be com¬ bined. As products containing a gas-sealed material of the invention e.g. films, moulded-blown bottles and containers, plates, tubes, injection moulded vessels, deep-drawn films and plates, liquid packaging card¬ boards, etc. may be mentioned. Sealed multiple-layer products are generally used for packaging food stuffs, when oxygen sealing is desired also in moist circumstances, but the sealing of carbon dioxide or some other gas may be thought of. In addition, fat, chemical and odour sealing may be desired both in food stuff packages and technical products. In the following non-limiting examples the manufacturing, properties and application of the polyolefin/vinyl alcohol polymer mixture of the invention in sealed one-layer products are described. The oxygen permeability of the films was measured with an OX-TRAN 1000 apparatus (ASTM D 3985) . The polyolefins and the vinyl alcohol polymers used in the tests of the examples are presented in the table below. Polyolefins (PO) P01 = LDPE (low density polyethylene), density 922 kg/m 3 , molten index (MI) 1.8 g/min (190°C) P02 = PP (propylene block copolymer), MI 3.3 g/10 min (230°C) P03 = PB (polybutene), MI 1.4 g/10 min (190°C) P04 = EVA (ethylene-vinyl acetate copolymer), vinyl acetate content 5% P05 = EBA (ethylene-butyl acrylate copolymer), MI 1.0 g/10 min (190°C) , butyl acrylate content 7% P06 = LLDPE (linear low density polyethylene) , grafted with 0.25% maleic acid anhydride (MHA) , MI 0.5 g/10 min (190°C) P07 - PP (propylene block copolymer), MI 3.3 g/10 min (230°C) P08 - PP (P03), grafted with 0.20% MHA P09 - PB (polybutene), MI 1.4 g/10 min (190°C) P010 - PB (P05), grafted with 0.25% itaconic acid P011 - EVA (ethylene-vinyl acetate copolymer) vinyl acetate content 5% P012 = EVA (P07), grafted with 0.1% fumaric acid P013 - EBA (ethylene-butyl acrylate copolymer), MI 1.0 g/10 min (190°C) , butyl acrylate content 7% P014 - EBA (P09), grafted with 0.4 % acrylic acid P015 - EEA (ethylene-acrylic acid copolymer) , acrylic acid content 6% Polyvinyl alcohol PVAl - vinyl alcohol copolymer wherein the comonomer is an ester of methacryl acid and polyethylene glycol (Vinex 4004, Air Products and Chemicals) PVA2 - polyvinyl alcohol, viscosity 4, hydrolysis degree 88% Plasticizer glycerol, degree of purity 99% Example 1 Polyolefin-PVA mixtures of the invention were prepared by mixing polyolefin and polyvinyl alcohol in molten state by the aid of a Berstorff mixer which was provided with a flat film nozzle. The temperature profile was 25 to 130 to 200 to 200 to 200 to 210 to 230 to 230 to 230 to 220 to 220, and the temperature of the melt was 220°C. The production rate was 10 kilograms per hour. The thicknesses of the obtained films were 100 to 170 μm. The com¬ pounds thereof are presented in the accompanying Table 1 A. The properties of the films are presented in the accompanying Table 1 B. The oxygen permeability values of the films are calculated for 25 μm thickness. The lightnesses of the films was measured as a so-called yellowness index conforming to the standard ASTM D 1925-70 with the Ultra Scan apparatus of Hunter Lab. Table 1 A Test Polyvinyl alcohol Polvolefine Plasticizer type % by weight type, % by w. PVAl 60 POl 40 2 PVAl 60 POl 36 4 3 PVAl 10 POl 36 4 PVA2 50 4 PVAl 90 POl 10 5 PVAl 30 POl 70 6 PVAl 10 POl 90 7 PVA2 60 POl 36 4 8 PVA2 90 POl 6 4 9 PVA2 30 POl 66 4 10 PVA2 10 POl 86 Table 1 B Test Melt Oxygen permeabil. Yellowness Tensile index (ml/m^x24hxbar) index,thick¬ strenigth g/io min 0%RH 65%RH 90%RH ness μm mach. /trans (210° ■ C) dir. dir. MPa MPa 1 13 1.0 8.7 12.0 0 151 20.8 6.5 2 54 2.5 35 49 0 105 7.0 3.8 3 3 1 1..55 > 0 0..2255 2277 - 2.3 155 14.4 5.0 4 4 5 544 0 0..2255 3300 6 677 0 98 15.1 7.1 5 5 9 9 8 822 8888 9 922 0 118 12.8 3.1 6 6 3 3 i 1:352266 11335500 : 11339900 0 135 9.6 8.1 7 7 2 266 2 2..11 3377 5 544 3.3 141 14.1 3.1 8 8 3 399 0 0..22 2266 9 988 4.7 137 6.3 3.5 9 9 8 8 8 800 8899 8 833 2.1 120 6.1 6.1 10 4 1296 1299 1421 . 1.0 167 8.1 7.0 Example 2 Polyolefin-PVA mixtures were prepared in which various polyolefins and polyvinyl alcohol (Vinex) were used in molten state, by the aid of a Berstorff mixer which was provided with a flat film nozzle. The temperature profile was from 25 to 130 to 200 to 200 to 200 to 210 to 230 to 230 to 230 to 220 to 220 and the temperature of the melt was 220°C. The production rate was 10 kilograms per hour. The thicknesses of the obtained films were 120 to 160 urn. The com¬ pounds thereof are presented in the accompanying Table 2 A. The properties of the films are presented in the accompanying Table 2 B. Table 2 A Test Polyvinyl alcohol Polyolefin Plasticier type, % by weight type, % by 11 PVAl 60 P03 40 12 PVAl 60 P04 40 13 PVAl 60 P05 40 14 PVAl 60 P06 40 Table 2 B Test Oxygen perm. Yellowπιess Tensile strength (ml/m^x24hxbar inde , thick- machine /transversal 0%RH 65%RH 90%RH ness μnl direction MPa MPa 11 2.1 13.0 56.1 3.1 154 10.9 7.1 12 1.8 14.9 49.2 4.2 163 11.0 6.3 13 4.3 12.7 53.1 3.8 153 9.2 8.5 14 3.0 13.2 59.2 2.7 121 10.1 5.0 Example 3 Polyolefin-PVA mixtures of the invention were prepared by mixing polyolefin and polyvinyl alcohol, in molten state, with the aid of a Berstorff mixer which was provided with a flat film nozzle. The temperature profile was 25 to 130 to 200 to 200 to 200 to 210 to 230 to 230 to 220 to 220, and the temperature of the melt was 220°C. The production rate was 10 kilograms per hour. The thicknesses of the obtained films were 100 to 260 μm. The com- pounds thereof are presented in the accompanying Table 3 A. The properties of the films are presented in the accompanying Table 3 B. The oxygen permeability values of the films are calculated for 25 μm thickness. The lightness of the films was measured as a so-called yellowness index conforming to the standard ASTM D 1925-70 with the Ultra Scan apparatus of Hunter Lab. TABLE 3 A Test Polyvinyl alcohol Polyolefin Plasticizer type % by weight type % by w. % by w. 1 PVAl 90 P06 10 2 PVAl 60 POl 20 P06 20 3 PVAl 60 P06 40 4 PVAl 50 P06 50 5 PVAl 40 P06 60 6a PVAl 30 P06 70 6b PVAl 30 P06 40 PVA2 30 7 PVAl 10 P06 90 8 PVAl 50 P015 50 the polyvinyl does not contain a plasticizer TABLE 3 B Test Melt Oxygen permeabil. Yellowness Tensi .le index (ml/m' 2 x24hxbar) index, thick¬ strength g/io min 0%RH 65%RH 90%RH ness μm mach. /trans (210 c > C) dir. dir. MPa MPa 1 8.5 0.9 1.2 1.7 0 130 16.2 13.1 2 1.5 1.1 3.2 4.8 0 100 16.7 8.9 3 0.9 1.1 1.5 3.4 0 142 19.8 20.2 4 0.7 1.3 1.5 4.5 0 168 20.0 15.6 5 0.1 1.7 2.6 5.0 0 183 15.7 13.4 6a 0.05 38 46 55 0.16 257 11.5 8.5 6b 1.5 1.2 2.1 17.2 2.0 179 18.9 18.5 7 0.05 1890 2560 2390 0 169 18.5 17.9 8 2.0 0.4 17 32 0.16 111 15.1 14.3 Example 4 For reference were prepared polyolefin-PVA mixtures in which poly¬ olefin unmodified with an acid or modified with an acid, and ordinary unmodified polyvinyl alcohol were used (except test 12) , in molten state, with the aid of a Berstorff mixer which was provided with a flat film nozzle. The temperature profile was from 25 to 130 to 200 to 200 to 200 to 210 to 230 to 230 to 230 to 220 to 220, and the temperature of the melt was 220°C. The production rate was 10 kilo¬ grams per hour. The thicknesses of the obtained films were 130 to 230 μm. The com¬ pounds thereof are presented in the accompanying Table 4 A. The properties of the films are presented in the accompanying Table 4 B. TABLE 4 A Test Polyvinyl alcohol Polyolefin Plasticizer type, % by weight type, % by w. 9 PVA2 90 P06 10 + 10 PVA2 90 POl 10 + 11 PVA2 60 POl 20 P06 20 + 12 PVAl 60 POl 40 - 13 PVA2 60 POl 40 + 14 PVA2 50 P06 50 + 15 PVA2 50 POl 50 + 16 PVA2 40 P06 60 + 17 PVA2 40 POl 60 + 18 PVA2 30 P06 70 + 19 PVA2 30 POl 70 + 20 PVA2 10 P06 90 + 21 PVA2 10 POl 90 + the polyvinyl alcohol does not contain plasticizer the quantity of polyvinyl alcohol contains 6% by weight of a plasticizer, calculated by PVA quantity TABLE 4 B Test Melt Oxygen ^ permeabil. Yellowness Tensile index (ml/m z x24hxbar) index, thick- strength g/io min 0%RH 65%RH 90%RH ness μm mach./trans (210° C) dir. dir. MPa MPa 9 8.9 0.15 37 43 5.37 227 16.0 16.0 10 27 0.17 46 52 5 191 13.0 7.5 11 1.1 0.25 25 39 3.45 194 17.5 7.9 12 14 1.0 8.7 15 0 134 20.8 6.5 13 25 0.25 27 43 3.5 136 14.0 6.0 14 0.5 0.9 25 18 1.56 191 17.2 11.1 15 20 1.0 29 57 30 189 12.7 4.8 16 0.3 1.5 22 33 3.21 206 15.9 14.2 17 23 1.5 25 35 2.5 201 11.8 4.2 18 0.5 7.2 51 63 5.22 203 16.5 15.9 19 15 7.5 64 70 2 194 10.9 4.2 20 0.5 1970 2390 2560 0.50 173 18.1 17.1 21 12 1990 2460 2380 1.5 200 18.0 13.1 Example 5 Polyolefin/PVA mixtures were prepared in which various polyolefins modified with an acid and internally plasticized polyvinyl alcohol polymer of the invention, or ordinary polyvinyl alcohol were used, in molten state, with the aid of a Berstorff mixer, which was provided with a flat film nozzle. The temperature profile was from 25 to 130 to 200 to 200 to 200 to 210 to 230 to 230 to 230 to 220 to 220, and the temperature of the melt was 220°C. The production rate was 10 kilograms per hour. The thicknesses of the obtained films were 120 to 260 μm. The com¬ pounds thereof are presented in the accompanying Table 5 A. The properties of the films are presented in the accompanying Table 5 B. TABLE 5 A Test Polyvinyl alcohol Polyolefin Plasticizer type, % by weight type, % by w. 22 PVAl 60 P08 40 23 PVA2 60 P07 40 + 24 PVAl 40 P010 60 25 PVA2 40 P09 60 26 PVAl 60 P012 40 27 PVA2 60 P011 40 + 28 PVAl 60 P014 40 29 PVA2 60 P013 40 30 PVAl 50 P015 50 31 PVA2 50 P015 50 = the polyvinyl alcohol does not contain a plasticizer + = the quantity of polyvinyl alcohol contains a plas¬ ticizer of 6% by weight, calculated from the PVA quantity TABLE 5 B Test Melt Oxygen perm. Yellowness Tensile strength index ml/m x24hxbar index/thick- mach./transv. g/10 min 0%RH 65%RH 90%RH ness μm dir. dir. MPa MPa 22 8.0 2.0 3.5 5.1 0 122 18.1 14.0 23 33.9 2.0 36 50 3.5 139 13.7 9.3 24 6.7 10.1 12.3 22 0.05 154 18.1 16.1 25 29 9.0 43 67 2.07 179 12.1 7.2 26 10 1.8 6.1 11 0.09 188 17.9 15.1 27 32 3.2 47 61 2.7 260 14.1 7.2 28 6.2 1.3 3.1 4.7 0 189 15.9 8.2 29 30 1.3 23 37 3.5 176 14.2 5.2 30 4.0 1.0 1.2 3.9 0 123 18.3 17.9 31 4.0 0.4 17 32 2.5 155 18.1 17.1

Claims: Claims 1. A gas-sealed material, containing polyolefin and polyvinyl alcohol, characterized in that the material is prepared by mixing 1 to 99 per cent by weight of polyolefin and 99 to 1 per cent by weight of in¬ ternally plasticized vinyl alcohol polymer in molten state, and optionally 1 to 15 per cent by weight of a plasticizer. 2. Gas-sealed material according to claim 1, characterized in that in the vinyl alcohol polymer chains are present polyglycol groups (polyether groups) as side groups. 3. Gas-sealed material according to claim 1 or 2, characterized in that the polyvinyl alcohol is a copolymer in which the comonomer is an unsaturated poly(alkyleneoxy)ester derivative. 4. Gas-sealed material according to claim 3, characterized in that said alkylene is an ethylene or propylene and that the acid component of said ester is acrylic acid or methacrylic acid. 5. A gas-sealed mixture according to any one of the preceding claims, characterized in that the polyvinyl alcohol contains an unmodified polyvinyl alcohol in the form of mixture and vinyl alcohol polymer according to claims 2 to 4. 6. A gas-sealed material according to any one of the preceding claims. characterized in that the polyolefin is a low density polyethylene (LDPE) , medium density polyethylene (MDPE) or high density poly¬ ethylene (HDPE) , polypropylene or polybutene, or ethylene copolymer with propylene, butene, hexene and octene, or an olefin/ester co¬ polymer, such as ethylene-vinyl-acetate copolymer, ethylene-acrylate ester copolymer or ethylene-methacrylate ester copolymer, EP rubber, EPD rubber or some other thermoplastic olefin-based elastomer, or a mixture of one or several above-mentioned polyolefins. 7. A gas-sealed material according to claim 6, characterized in that the polyolefin is modified by graf ing or copolymerizing thereto 0.1 to 10 per cent by weight of carboxylic acid selected from the group of acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid, sorbic acid, and anhydrides of the afore¬ mentioned acids. 8. Gas-sealed material according to any one of the preceding claims, characterized in that the polyolefin is formed from a mixture of an unmodified polyolefin and a polyolefin modified with carboxyl acid. 9. Gas-sealed material according to any one of the preceding claims, characterized in that it consists further 1 to 15 per cent by weight of one or several plasticizers selected from among the group of ethylene glycol, trimethylene glycol, propylene glycol, triethylene glycol, neopenthyl glycol and 2,2,4-trimethyl-l,3-pentanediol and sorbitol. 10. Products containing a gas-sealed material according to any one of the preceding claims.

Inventors: BERGSTROEM CHRISTER, KETTUNEN LEILA, LINDSTROEM HELGE, SEPPAENEN HANNELI, STJERNBERG MARIA, TUOMINEN OLLI, BERGSTROEM, CHRISTER, KETTUNEN, LEILA, LINDSTROEM, HELGE, SEPPAENEN, HANNELI, STJERNBERG, MARIA, TUOMINEN, OLLI
Applicants: NESTE OY
Application year: 1990
Main classification: C08L23
IPC codes: C08J5, C08L23, C08L29, C08L51, C08L77