FI86870C - GASTAETT MATERIAL, SOM INNEHAOLLER INVAENDIGT MJUKGJORD POLYVINYLALCOOL - Google Patents

Description

86870

Gas-tight material containing internally plasticized polyvinyl alcohol

The material of the present invention is 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 and polyvinyl alcohol 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. contains other layers that cause, for example, adhesion between the 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, as a mixture, products containing polyolefin and polyvinyl alcohol which have low oxygen permeability and which are therefore excellently suitable for the production of packaging films, for example. Finnish patent application 87-5772 discloses a mixture of polyolefin and polyvinyl alcohol, which optionally additionally contains plasticizers. Mixing the polyolefin and polyvinyl alcohol 5 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 tightness is obtained for the product, for example an 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.

Although polyolefin-PVA blends generally have good oxygen tightness properties under dry conditions, under humid conditions their oxygen density decreases significantly, making them sensitive to moisture. In addition, when the blends of polyolefins and PVA are melt blended, partial decomposition of PVA and 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 blends is that the viscosity of the product is not high enough and the mechanical properties of the films made therefrom are not good enough.

The present invention relates to a polyolefin containing polyvinyl alcohol, in which the oxygen sensitivity of the product to moisture is reduced, the brightness of the product is increased and the migration of plasticizers is reduced.

According to the invention, it has surprisingly been found that the mixing of certain internally plasticized polyvinyl alcohol copolymers in the molten state with the polyolefins provides products which are lighter in color and in which the oxygen density achieved is considerably less sensitive to moisture than conventional polyvinyl alcohol. In addition to its 86870 3, there is no or very little migration of plasticizers in the material according to the invention.

Thus, the invention relates to a gas-tight material containing 5 polyolefins and polyvinyl alcohol, which material is prepared by mixing in a molten state 1-99% by weight of a polyolefin and 99-1% by weight of an internally plasticized vinyl alcohol polymer and optionally 1-15% by weight of a plasticizer. The gas-tight material according to the invention is characterized in that the vinyl alcohol polymer chains have 10 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 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 states that the product has good oxygen tightness and is suitable for casting, injection molding and extrusion products and that "it is characterized by good solubility in water and is therefore particularly suitable for the production of films required" *. water solubility.

The vinyl alcohol polymer used in the polyolefin-polyvinyl alcohol mixture according to the invention is preferably one in which the alkylene of the alcohol moiety in the poly (alkyleneoxy) ester derivative used as a comonomer 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 polyomer.

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The amount of internally plasticized vinyl alcohol polymer in the polyethylene-polyvinyl alcohol mixture according to the invention may be between 1 and 99% by weight, preferably between 10 and 90% by weight. At lower amounts, the effect on oxygen permeability is reduced, but the color of the product is kept good despite the slime. In some cases, it may be advantageous to replace part 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.

The polyolefin in the gas-tight material according to the invention may 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-20 rubber.

The amount of polyolefin in the gas-tight material according to the invention may be between 1 and 99% by weight, but preferably between 10 and 90% by weight of the total mixture.

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The gas-tight material according to the invention may further contain 1-15% by weight of plasticizers. The plasticizer can be selected from any substance known as a polyvinyl alcohol plasticizer or a mixture thereof. Examples which may be mentioned are ethylene glycol, trimethylene glycol, propylene glycol, triethylene glycol, neopentyl glycol and 2,2,4-trimethyl-1,3-pentanediol and sorbitol. The preferred plasticizer is glycerol.

The gas-tight polyolefin / PVA blend of the invention can be prepared by mixing the polyolefin component, the vinyl alcohol polymer component and the optional plasticizer component in the melt blender simultaneously as a dry blend, premixed in a solid or molten state, or the various components can be added separately. The addition of plasticizers can also be performed after compounding. It is also possible to add the plasticizer to the PVA component, which has the advantage that the whole mixture does not have to be softened.

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Various products can be prepared from the polyolefin / PVA 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, 10 (co) extrusion coating, (co) extrusion lamination, adhesive lamination or other techniques, and these manufacturing methods can also be combined.

Suitable products 15 containing a 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. the tightness of carbon dioxide or some other gas may also be considered. In addition, grease, chemical and odor tightness are 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 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 and vinyl alcohol polymers used in the experiments of the examples are shown in the table below:

Polyolefins (PO): PO1 = LDPE (low density polyethylene), density 922 kg / m3, melt index (MI) 1.8 g / 10 min (190 ° C) 35 PO 2 - PP (propylene block copolymer), MI 3.3 g / 10 min (230 ° C) PO 3 -PB (polybuteone), MI 1.4 g / 10 min (190UC) PO 4 = EVA (ethylene-vinyl acetate copolymer). vinyl acetate content 5% 40 PO5 = EBA (ethylene-butyl acrylate copolymer), MI 1.0 g / 10 min (190 ° C), butyl acrylate content 7% 6 86870

Polyvinyl alcohol: PVAl - a vinyl alcohol copolymer with a comonomer of methacrylic acid and polyethylene glycol ester (Vinex 4004, trade name of Air 5 Products and Chemicals Inc.) PVA2 = polyvinyl alcohol, viscosity 4, degree of hydrolysis 88%

Plasticizer: 10 glycerol, 99% pure

Example 1 15

The polyolefin-PVA blends of the invention were prepared by mixing polyolefin and polyvinyl alcohol in a molten state using a Berstorff mixer equipped with a flat film nozzle. The thermal state profile was 25-130-200-200-200-210-230-230-230-220-220 and the temperature of the melt 20 was 220 ° C. The production rate was 10 kg / h.

The thicknesses of the obtained films were 100-170 μια. Their compositions are shown in Table 1 A below. The properties of the films are shown in Table 1 B below. The oxygen permeabilities of the films have been calculated for a thickness of 25 μπι: η 25. 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.

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Table 1 A

Test Polyvinyl alcohol Polvolefin Plasticizer 5 type wt% type wt% 1 PVA1 60 P01 40 2 PVA1 60 POl 36 4 10 3 PVA1 10 POl 36 4 PVA2 50 4 PVAl 90 POl 10 5 PVAl 30 POl 70 6 PVAl 10 POl 90 15 7 PVA2 60 POl 36 4 8 PVA2 90 POl 6 4 9 PVA2 30 POl 66 4 10 PVA2 10 POl 86 4 20

Table 1 B

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Test Melt- Oxygen blot Yellowness_ Tensile strength_index (ml / m2x24hxbar) _ index thickness cross-machine 30 (g / 10 min) 0% RH 65% RH 90% RH μια direction direction (210 ° C) MPa MPa 1 13 1.0 8 .7 12.0 0 151 20.8 6.5 35 2 54 2.5 35 49 0 105 7.0 3.8 3 1.5 0.25 27 2.3 155 14.4 5.0 4 54 0 , 25 30 67 0 98 15.1 7.1 59 82 88 92 0 118 12.8 3.1 6 3 1326 1350 1390 0 135 9.6 8.1 40 7 26 2.1 37 54 3.3 141 14 , 1 3.1 8 39 0.2 26 98 4.7 137 6.3 3.5 9 8 80 89 93 2.1 120 6.1 6.1 10 4 1296 1299 1421 1.0 167 8.1 7 .0 45

Example 2

Polyolefin-PVA blends were prepared using various polyolefins and polyvinyl alcohol (Vinex) in the molten state using a 50 Berstorff mixer equipped with a flat film nozzle 86870 8 la. The temperature profile was 25-130-200-200-200-210-230-230-230-220-220 and the melt temperature was 220 ° C. The production rate was 10 kg / h.

The thicknesses of the obtained films were 120-160 μm. Their compositions are shown in Table 2A below. The properties of the films are shown in Table 2B below.

Table 2 A

10 _

Experiment Polyvinyl alcohol Polvolefin Plasticizer type wt% type wt% 15 11 PVAl 60 PO3 40 12 PVAl 60 P04 40 13 PVAl 60 PO5 40 14 PVAl 60 PO 6 40 20 _

Table 2 B

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Test Oxygen permeability Yellowness_ Tensile strength_ (ml / mzx24hxbar) _ index thickness cross-machine 30 0% RH 65% RH 90% RH / im direction direction MPa MPa 11 2.1 13.0 56.1 3.1 154 10.9 7, 1 35 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 40 I,

Claims (8)

86870 A gas-tight material comprising a polyolefin and a polyvinyl alcohol, which material is prepared by mixing in the molten state in a state of 1 to 99% by weight of a polyolefin and 99 to 1% by weight of an internally plasticized vinyl alcohol polymer and optionally 1 to 15% by weight of a plasticizer , that vinyl alcohol polymer chains have polyglycol groups (polyether groups) as side groups. Gas-tight 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. A gas-tight material according to claim 2, characterized in that said alkylene is ethylene or propylene and that the acid moiety of said ester is acrylic acid or methacrylic acid. Gas-tight mixture according to one of the preceding claims, characterized in that the polyvinyl alcohol comprises, as a mixture, unmodified polyvinyl alcohol and a vinyl alcohol polymer according to Claims 1 to 3. Gas-tight material according to one 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 polybutylene, or a copolymer of ethylene with propylene, butene , with hexene and octene, or an olefin ester copolymer such as an ethylene-vinyl acetate copolymer, an ethylene-acrylate ester copolymer or an ethylene-methacrylate ester copolymer, an EP rubber, an EPD rubber, or another thermoplastic olefin-based elastomer or elastomer-based elastomer Gas-tight material according to one of the preceding claims, characterized in that the polyolefin is a mixture of unmodified polyolefin and carboxylic acid-modified polyolefin. Gas-tight material according to one of the preceding claims, characterized in that it further contains 1 to 15% by weight of one or more plasticizers selected from the group consisting of ethylene glycol, trimethylene glycol, propylene glycol, triethylene glycol, neopentyl glycol and 2,2,4-trimethyl -1,3-pentanediol and sorbitol. Products comprising a gas-tight material according to any one of the preceding claims 10. n 86870