FI86875C - GASTAETT MATERIAL, SOM INNEHAOLLER INVAENDIGT MJUKGJORD POLYVINYLALCOOL - Google Patents

Description

86875

Gas-tight material containing internally plasticized polyvinyl alcohol

The material is mixed with a mixture of 5 polyvinyl alcohols

The invention relates to a gas-tight material and products containing a gas-tight material. In particular, the invention relates to a gas-tight material comprising polyolefin, polyvinyl alcohol and polyamide and products containing it.

Polyolefins are widely used, for example, in the packaging industry in the manufacture of 15 different film products. The advantages of polyolefins are particularly good strength and water resistance properties. Disadvantages include permeability to certain gases and liquids, especially oxygen and hydrocarbon solvents. For this reason, the usefulness of polyolefin films is limited in the packaging of certain substances, such as foodstuffs, where low oxygen permeability is required.

It is common in the packaging industry to use multilayer film structures in which the materials of the different layers are selected for a specific purpose. Thus, such multilayer structures may include layers that provide a good barrier to gases, e.g., oxygen, as well as layers that impart other properties to the product, e.g., strength properties. In addition, multilayer structures may include other layers that provide, for example, adhesion between different layers. However, such products are expensive to manufacture.

Polyvinyl alcohol is a polymer with low oxygen permeability. This property has been most commonly used in olefin-vinyl alcohol random copolymers and olefin-vinyl alcohol block copolymers. It is also known to prepare a mixture of polyolefin and polyvinyl alcohol products which have a low oxygen permeability and which are therefore excellently suitable, for example, for the production of packaging films. Finnish patent application 87-5772 discloses a mixture of polyolefin and polyvinyl alcohol, which optionally additionally contains plasticizers. Mixing the polyolefin and polyvinyl alcohol in the molten state gives a mixture consisting of two phases, a continuous phase and a dispersed phase. When the diameter of the particles in the dispersed phase is small enough, completely transparent films are obtained. Mixing is usually performed in a separate compounding step before extruding the final product.

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When PVA forms a continuous phase in a mixture of polyolefin and PVA, a good density is obtained for the product, for example oxygen tightness, and the product is clear and stable in both molten and solid state despite the two phases and is easy to soften by adding plasticizers.

EP 280455-A discloses oxygen-tight materials comprising a mixture of polyethylene, a polyolefin containing carboxyl groups and a third poly-20 polymer incompatible with polyethylene. According to the publication, said third polymer may be polyamide (PA), ethylene-vinyl alcohol copolymer, polyvinyl alcohol (PVA), polyester or a mixture thereof, although no examples of mixtures, for example mixtures of polyamide and polyvinyl alcohol, are given. The blend of polyethylene and PVA is not usable due to its brittleness and the blend of polyethylene and polyamide is not usable due to insufficient barrier properties. If, instead, polyethylene is mixed with PVA and polyamide, the product is both dense and tough.

30 Although polyolefin / PVA / PA blends generally have good oxygen tightness properties under dry conditions, under wet conditions they have a significant decrease in oxygen tightness and are therefore sensitive to moisture. In addition, when melt blends of polyolefins, PVA and polyamide, partial decomposition of PVA and strong discoloration of the product occur. When plasticizers are used, their stability in the mixture is not the best, which is why migration of plasticizers occurs in the product. Another disadvantage of conventional PE / PVA / PA blends is 3,86875 that the melt index of the product is not low enough.

The present invention relates to a material comprising polyolefin, polyvinyl alcohol and polyamide in which the sensitivity of the product to the moisture tightness of moisture is reduced, the brightness of the product is increased and the need for plasticizers is eliminated and the strength properties of films made of the product are improved toughness, tensile strength and impact strength.

According to the invention, it has surprisingly been found that the blending in the molten state of certain internally plasticized vinyl alcohol polymers and amorphous polyamide with polyolefins copolymerized or grafted with a carboxylic acid provides products which are lighter in color and have an oxygen density of much less than 15 m. and in addition, the films made from the product have better strength properties than when using unmodified polyolefin, ordinary polyvinyl alcohol and polyamide.

Thus, the invention relates to a gas-tight material comprising a polyolefin, a vinyl alcohol polymer and a polyamide prepared by mixing in a molten state 3 to 60% by weight of a polyolefin, 10 to 96% by weight of an internally plasticized vinyl alcohol polymer and 1 to 50% by weight of an amorphous polyamide. . The gas-tight material 25 according to the invention is characterized in that the vinyl alcohol polymer chains have polyglycol groups (polyether groups) as side groups.

By internally plasticized vinyl alcohol polymer is meant a vinyl alcohol polymer that contains polyglycol groups (polyether groups) or other polyvinyl alcohol plasticizing groups in its side chains. These plasticizer groups are attached to the chain by copolymerization, grafting, or reactive compounding. One such internally plasticized polyvinyl alcohol is a Vinex polymer (trade name, Air Products and Chemicals Inc.) in which the comonomer is an ester of methacrylic acid and polyethylene glycol.

Such internally plasticized vinyl alcohol polymers can be prepared, for example, as disclosed in U.S. Patent 4,708,999.

This patent discloses that the product has good oxygen tightness and is suitable for casting, injection molding and extrusion products and is characterized by good water solubility and is therefore particularly suitable for the production of films requiring water solubility.

The vinyl alcohol polymer used in the polyolefin-polyvinyl alcohol-polyamide mixture according to the invention is preferably one in which, in the poly (alkyleneoxy) ester derivative used as a comonomer, the alkylene of the alcohol moiety is ethylene or propylene and the acid moiety is acrylic acid or methacrylic acid. Such modified vinyl alcohol polymers can be prepared, for example, by polymerizing a vinyl acetate monomer and a poly (alkyleneoxy) acrylate comonomer and hydrolyzing the copolymer thus obtained to produce an internally plasticized vinyl alcohol polymer.

The amount of internally plasticized vinyl alcohol polymer in the polyethylene-polyvinyl alcohol / polyamide blend according to the invention may be between 10 and 96% by weight, preferably between 30 and 60% by weight. In some cases, it may be advantageous to replace some of the internally plasticized vinyl alcohol polymer used in the gas-tight material with unmodified polyvinyl alcohol, if the intended use of the product allows it.

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The polyolefin in the gas-tight material according to the invention can be based on homo- or copolymers of olefins. Thus, it may be low density polyethylene (LDPE), medium density polyethylene (MDPE) or high density polyethylene (HDPE), polypropylene or polybutylene. The polyolefin may also be a copolymer of ethylene with other olefins such as propylene, butene, hexene and octene. The polyolefin may also be an olefin ester copolymer, such as an ethylene-vinyl acetate copolymer, an ethylene-acrylate ester copolymer, or an ethylene-methacrylate ester copolymer, or it may be a thermoplastic olefin-based elastomer, such as EP or EPD rubber.

5,86875

The amount of polyolefin in the gas-tight material according to the invention may be between 3 and 60% by weight, but preferably between 30 and 60% by weight of the total mixture.

The third component in the gas-tight material according to the invention is amorphous polyamide. The polyamide used is preferably a polyamide having a degree of crystallinity ranging from 1 to 10%, preferably from 1 to 5%.

The amount of amorphous polyamide in the material according to the invention can be selected from 1 to 50% by weight.

Amorphous polyamide improves the toughness and deep tensile properties of the polyolefin and polyvinyl alcohol copolymer blend.

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The gas-tight polyolefin / PVA / PA blend of the invention can be prepared by mixing the polyolefin component, the vinyl alcohol copolymer component and the polyamide component in a melt blender simultaneously as a dry blend, premixed in a solid or molten state, or the various components can be added separately.

Various products can be made from the polyolefin / PVA / PA blend of the invention by combining the blend with polyolefins, other plastics, or other materials, such as fiber-based materials. Multilayer products can be made by coextrusion, (co) extrusion coating, (co) extrusion lamination, glue lamination, or other techniques, and these manufacturing methods can also be combined.

Suitable products containing the gas-tight material according to the invention are, for example, films, blow-molded bottles and containers, sheets, tubes, injection-molded containers, deep-drawn films and sheets, liquid packaging boards, etc. Dense multilayer products are generally used for food packaging but the tightness of carbon dioxide or some other gas may also come into question. In addition, fat, chemical and odor tightness is desired in both food packaging and technical products.

The following non-limiting examples illustrate the preparation, properties and application of the polyolefin / vinyl alcohol polymer / polyamide blend of the invention in dense monolayer products. The oxygen permeability of the membranes was measured with an OX-TRAN 1000 instrument (ASTM D 3985). The polyolefins, vinyl alcohol polymers and polyamides used in the experiments of the examples are shown in the table below: 10

Polyolefins: P01 - LDPE (low density polyethylene), melt index 1.8 g / 10 min (190 ° C) 15

Polyvinyl alcohol: PVAl - vinyl alcohol copolymer with comonomer of methacrylic acid and polyethylene glycol ester (Vinex 4004, 20 trade name, Air Products and Chemicals Inc.) PVA2 - polyvinyl alcohol, viscosity 4, degree of hydrolysis 88%

Polyamides: 25 PAl - amorphous polyamide, crystallinity 1-5%? PA2 - polyamide 6 PA3 - polyamide 11 PA4 - polyamide 12 30 Plasticizer: glycerol, purity 99% 35 Example 1

The polyolefin / PVA / polyamide * blends of the invention were prepared by mixing polyolefin, polyvinyl alcohol and polyamide in the molten state using a Berstorff mixer equipped with a flat film-nozzle. The temperature profile was 130-190-200-210-210-210-220-220-215-210. The production rate was 10 kg / h.

The thickness of the obtained films was 150-200 μπι. Their compositions are shown in Table 1A below. The properties of the films are shown in Table 1B below. 45 The oxygen permeabilities of the films have been calculated for a thickness of 25 μπι: η 7,86875. The brightness of the films was measured by the so-called as a yellowness index according to ASTM D 1925-70 on Hunter Lab’s Ultra Scan.

Table 1 A

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Experiment Polyvinyl alcohol Polvolefin Polyamide type p-% type p-% type p-% 10 _ 1 PVAl 60 P01 30 PAl 10 2 PVAl 60 P01 10 PAl 9 PA2 21 15 3 PVAl 60 P01 10 PAl 9 PA3 21 4 PVAl 60 POl 10 PAl 9 PA4 21 5 PVAl 60 POl 10 PAl 30 20 6 PVA2 60 POl 40

Note. In Experiment 6, the amount of polyvinyl alcohol includes 4.5% of the amount of glycerol in the PVA.

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Table 1 B

30 Test Oxygen permeability Yellowness_ Tensile strength_ fm 1 / m2x 2 4hxb ar) index thickness machine cross- 0% RH 90% RH μπι direction direction MPa MPa 35 1 0.01 2.5 0.75 151 15.0 14.5 2 0, 09 1.5 0.75 163 44.8 25.0 3 0.12 1.5 0.75 148 44.0 24.5 4 1.11 1.5 0.75 191 42.5 22.7 40 5 0.01 3.0 0.85 190 47.8 29.0 6 0.20 10.0 10.9 172 10.0 7.0

Claims (7)

1. Gas-sealed material containing polyolefin, polyvinyl alcohol and polyamide, which material is prepared by melting in the molten state to mix 3-60 wt.% Polyolefin, 10-96 wt.% Internally softened vinyl alcohol polymer and 1-50 wt.% Amorphous polyamide. , characterized in that the vinyl alcohol polymer chains have polyglycol groups (polyether groups) as side groups. Gas-sealed material according to claim 1, characterized in that the polyvinyl alcohol is a copolymer in which the comonomer is an unsaturated poly (alkyleneoxy) ester derivative. Gas-sealed material according to claim 2, characterized in that said alkylene is ethylene or propylene and the acid part of said ester is acrylic acid or methacrylic acid. k. Gas-tight mixture according to any of the preceding claims, characterized in that the polyvinyl alcohol comprises in the mixture unmodified polyvinyl alcohol and vinyl alcohol polymer according to claims 2 - 3. Gas-sealed material according to any of the preceding claims, characterized in that the polyolefin is low density polyethylene (LDPE), medium density polyethylene (MDPE) or high density polyethylene (HDPE), polypropylene or polybutene, or a copolymer of ethylene with propylene, butene, hexene and octene or an olefin ester copolymer, such as, for example, ethylene-vinyl acetate copolymer, ethylene-acrylate ester copolymer or ethylene-methacrylate ester copolymer, EP-rubber, EPD-rubber or any other thermoplastic elastomer. Gas-tight material according to any of the preceding claims, characterized in that the degree of crystallisation of the polyamide is between 1 and 5%. 35 2 Products containing a gas-tight material according to any of the preceding claims.