WO2002024806A1

WO2002024806A1 - Plastic composition, method for producing the same and the use thereof, especially as barrier medium

Info

Publication number: WO2002024806A1
Application number: PCT/EP2001/010814
Authority: WO
Inventors: Matthias Gutweiler; Martin Steuer; Sven KÖHNEN; Robert W. Fuss
Original assignee: Kuraray Specialtities Europe Gmbh
Priority date: 2000-09-20
Filing date: 2001-09-19
Publication date: 2002-03-28
Also published as: WO2002024806B1; DE10046619A1

Abstract

The invention relates to a plastic composition that contains 30 to 99 % by weight of a plasticized polyvinyl alcohol and 1 to 70 % by weight of a polyolefin maleic anhydride copolymer. The invention further relates to a method for producing said compositions and to the use thereof, especially as a barrier medium in fuel tanks.

Description

description

Plastic composition, process for its production and its use, in particular as a barrier medium

The present invention relates to plastic compositions which, inter alia in a multilayer structure, have excellent properties in relation to gases and organic liquids, in particular fuels, in comparison with the barrier media available on the market today. The

Compositions contain at least one plasticized polyvinyl alcohol and at least one polyethylene-maleic anhydride copolymer and, if appropriate, further plastics, extrusion aids, drying agents and antioxidants which can be processed into barrier media using conventional extrusion methods.

Known barrier media generally consist of a combination of different plastics, since one plastic alone cannot meet the high technical requirements placed on barrier media. Such requirements are, for example, break resistance, transparency, low weight, easy processing, good printability and sealability. For many applications, both in the food and in the technical field, today's barrier media must have a great barrier effect against oxygen, water, carbon dioxide, aroma and fragrance substances as well as organic liquids. The barrier packaging available on the market today consists of at least three, but usually six or more, layers. The plastics used mainly as so-called support layers are polyethylene (PE), polypropylene (PP), oriented polypropylene (OPP), polyethylene terephthalate (PET), polycarbonate (PC) and polystyrene (PS). The actual barrier materials, consisting of ethylene vinyl alcohol (EVOH), polyamide (PA) or polyvinylidene chloride (PVDC), are embedded in a kind of sandwich structure.

BESTATIGUNGSKOPIE The barrier media can be produced by all methods known to the person skilled in the art, such as, for example, by co-extrusion, laminating, painting and coating, and by laminar technology.

In co-extrusion, production takes place in that at least two plastic melts are bonded to one another by means of adhesion promoters. In this way, sandwich structures are also produced, for example, which have polyamide (PA) or ethylene-vinyl alcohol (EVOH) as a barrier layer, which is enclosed between support layers made of polyethylene (PE) or polypropylene (PP). Such barrier media are used, for example, as menu trays, underfloor heating pipes, crop protection containers and fuel tanks. However, the production of EVOH is complex and expensive. Another disadvantage is that the use of adhesion promoters is necessary to bond the individual layers together.

When laminating, the plastic foils are connected to one another using a suitable adhesive. When painting and coating, the foils are coated or coated in particular with PVDC. However, PVDC has the disadvantage that it is thermally sensitive, contains chlorine and is difficult to recycle.

With the laminar technology, the barrier material PA is incorporated into PE during the extrusion, so that overlapping lamellae are created. The use of an adhesion promoter is also necessary here. The actual barrier effect is based on the lamellar structure in the PE matrix caused by the PA, in which the gases have to cover a greater diffusion path through the barrier layer than in the case of a material without a lamellar structure, but ultimately diffuse through the barrier medium.

Barrier media can also be produced by vapor deposition with aluminum or SiO _x . The aluminum or SiO _{x is} evaporated on a suitable carrier film in a high vacuum. For example, coffee packaging is made by steaming a PET film with aluminum and subsequent coating with PE. A disadvantage of the production by vapor deposition with aluminum is that cracks can easily occur due to mechanical stress, which reduce the barrier effect and on the other hand the transparency is lost. In addition, the process is generally very complex and expensive.

Barrier media can also be produced by fluorination and sulfonation. For example, blow molded articles are inflated with fluorine or H ₂ S0 ₃ . This causes the gas to react with the surface of the plastic, creating the barrier layer. The barrier layer is thus on the side facing the ingredient. With the barrier media produced in this way, the finest cracks, caused by stress, have a disadvantageous effect on the barrier effect. In addition, this manufacturing process requires a great deal of safety.

Regardless of the manufacturing process, the barrier effect also depends heavily on the environmental conditions, e.g. Temperature, pressure and / or humidity.

The above-described processes for formulating and producing barrier media are the subject of a large number of patents and patent applications.

For example, EP-A-0 015 556 describes a process for producing a laminate material from a mixture which is a polyolefin, a second polymer which is incompatible with the polyolefin, selected from the group of polyamides and polyesters, and contains an alkyl carboxyl substituted polyolefin.

A formulation consisting of ethylene-vinyl alcohol copolymers with crystalline nylon and ionomeric and optionally usable amorphous nylon is described in WO 97/09380. The ionomer is Copolymers of ethylene and carboxylic acid, which are then neutralized with metal ions.

US Pat. No. 5,939,158 describes a polymer built up in a laminar structure, which consists of the materials polyolefin, nylon, polyvinyl alcohol and a compatibilizer, which can be a mixture of two different alkyl carboxyl-substituted polyolefins or a small amount of a maleic anhydride-modified polyolefin, consists.

WO 90/12061 describes a formulation consisting of polyolefin and internally plasticized polyvinyl alcohol. The formulation is prepared by mixing the polyolefin with the internally plasticized polyvinyl alcohol in the molten state using a material mixer equipped with a flat film nozzle. The internally plasticized polyvinyl alcohol is a copolymer of vinyl alcohol and an ester of methacrylic acid and polyethylene glycol. The polyvinyl alcohol used is partially saponified, with a degree of hydrolysis of 88%, and has a viscosity of 4 mPas. The plasticizer to be used optionally with 1 to 15% by weight is glycerol.

WO 99/54400 discloses a formulation consisting of polyolefin and polyvinyl alcohol. Based on 100% by weight of polyolefin are 3 to 40% by weight of a high molecular weight compatibilizer (acrylic-containing copolymer) and / or 0.1 to 5% by weight of a low molecular weight compatibilizer (maleic anhydride) and 0.01 to 0.5% by weight .-% contain an initiator (peroxide compound). Based on 100% by weight of polyvinyl alcohol, the formulation contains 3 to 50% by weight of plasticizer (glycerol / water), 1 to 10% by weight of extrusion aid and 0.01 to 5% by weight of antioxidant. The formulation is prepared by first mixing a plasticizer, the extrusion aid and the antioxidant to the polyvinyl alcohol and then homogenizing in a mixer at more than 100 revolutions / minute for at least 5 minutes. This polyvinyl alcohol composition is dried at 80 to 120 ° C for more than 3 hours. In the meantime, the high molecular and low molecular compatibilizers and the initiator to a polyolefin in the mixer and also mixed under the same conditions as in the polyvinyl alcohol blend production. The two polyvinyl alcohol and polyolefin blends thus produced are mixed together again in the mixer mentioned above, extruded using a twin-screw extruder and then granulated. Due to the incompatibility of polyethylene and polyvinyl alcohol, heterogeneous areas are formed, also due to the separate addition of the compatibilizer, which adversely affect the barrier properties. Thus, the excellent barrier effect of polyvinyl alcohol against gases and organic liquids is not fully exploited here. In addition, the manufacturing process is very complex, inter alia due to the large number of mixing processes.

Based on the prior art mentioned, it was an object of the present invention to provide a material, in particular for use as

Barrier medium to provide that fully exploits the barrier effect and is also easy to manufacture.

This object is achieved by a plastic composition which contains 30 to 99% by weight, preferably 50 to 80% by weight, of a plasticizer

Polyvinyl alcohol and 1 to 70 wt .-%, preferably 20 to 50 wt .-%, of a polyolefin-maleic anhydride copolymer.

Polyethylene and polypropylene are preferred as polyolefins, with polyethylene being particularly preferred.

The proportion of maleic anhydride in the polyolefin-maleic anhydride (MA) copolymers is 0.1 to 20% by weight, preferably 0.1 to 10% by weight. The proportion of polyolefin in the copolymer is accordingly in the range from 80 to 99.9% by weight, preferably in the range from 90 to 99.9% by weight. The particularly preferred polyethylene (PE) -maleic anhydride (MSA) copolymers have melt indexes which are preferably in the range from 0.3 to 10 g / 10 minutes.

All fully or partially hydrolyzed polymers of vinyl acetate can be used as polyvinyl alcohol. However, it is preferred to use completely saponified polyvinyl alcohols with a degree of hydrolysis of at least 98 mol%, particularly preferably at least 99 mol%. The 4% by weight aqueous solution of the polyvinyl alcohol preferably has a viscosity of 3 to 50 mPas, particularly preferably 10 to 30 mPas (measured according to Höppler at 20 ° C.).

All plasticizers or plasticizer mixtures which are compatible with polyvinyl alcohol and are suitable and known for plasticizing them can be used as plasticizers. Preferred plasticizers are organic substances containing hydroxyl groups, such as, for example, glycols, polyhydric alcohols having 1 to 10 carbon atoms, trimethylolpropane, neopentyl glycol and fatty acid monoglycerides. The proportion of plasticizer in the plasticized polyvinyl alcohol is preferably in the range from 5 to 50% by weight and particularly preferably in the range from 10 to 20% by weight. Internal plasticization of the polyvinyl alcohol is also possible.

The plasticizer-containing polyvinyl alcohol may also contain other additives. Additives which can preferably be silica, thermoplastic resins, both liquid and powder, e.g. as a dispersion or dispersion powder, particularly preferably homo- or copolymers of vinyl acetate, maleic esters, acrylic esters and long-chain and / or branched carboxylic esters being suitable as comonomer components, wax-like substances, fatty acid esters and their derivatives, and / or commercially available oxidation stabilizers.

A particularly preferred plasticizer-containing polyvinyl alcohol has the following composition: 50 to 99% by weight polyvinyl alcohol, 5 to 25% by weight glycerin, 2 to 8% by weight water, 0 to 10% by weight stearic acid, 0 to 5% by weight Aerosil and 0 to 4% by weight. -% polyvinyl acetate.

In a further embodiment, the composition according to the invention can also contain up to 50% by weight, preferably up to 5% by weight, based on the total composition of polyolefins, preferably polyethylene or polypropylene and particularly preferably polyethylene.

However, a plastic composition is preferred which essentially consists of the plasticized polyvinyl alcohol and the polyolefin-maleic anhydride copolymer.

The invention also relates to a method for producing this composition. For this purpose, the polyvinyl alcohol is first plasticized, then this softener-containing polyvinyl alcohol is optionally mixed with the polyolefin-maleic anhydride copolymer and compounded and granulated using an extruder. The process according to the invention for the polyethylene-maleic anhydride copolymer to be used with particular preference is described in detail below.

The plasticizer-containing polyvinyl alcohol and the polyethylene-maleic anhydride copolymer are preferably used in granular form.

The two components are optionally mixed with one another and compounded in an extruder at melt temperatures of 170 to 240 ° C., preferably 210 to 230 ° C., and then granulated.

The granulate is characterized by good processability with various non-polar plastics, such as polyethylene. Because of this good Properties, the composition according to the invention can be used in a large number of applications.

The granules obtained can therefore be processed together with other plastics to form a shaped body by all processes known to the person skilled in the art, preferably by extrusion and particularly preferably by co-extrusion.

The subject of the present application is therefore also a molded article containing the plastic composition according to the invention. The shaped body preferably contains at least one layer which essentially consists of the composition according to the invention.

Such a shaped body is distinguished, inter alia, by good barrier properties against gases and organic liquids, such as fuels, and also by its good processability.

The molded body according to the invention can be used as a barrier medium in a large number of applications, for example in single-layer or multilayer structures in the packaging sector. The molded body is preferably used for the production of fuel tanks.

When using the shaped body according to the invention as a barrier medium in multilayer structures, up to two layers can be saved compared to conventional barrier media (EVOH, PA), since the composition according to the invention itself has sufficient adhesion to the carrier material and therefore no adhesion promoter is required.

The invention is described in more detail below on the basis of exemplary embodiments, but without being restricted in any way thereby. example 1

a) Preparation of the plasticized polyvinyl alcohol

1000 parts by weight (GT) of polyvinyl alcohol, 25 GT ^® Mowilith powder DS, 2.5 GT stearic acid, 175 GT glycerol, 50 GT water and 6 GT ^® Aerosil R 972 are used. The polyvinyl alcohol used is saponified to 98 mol%. A 4% aqueous solution has a viscosity of 10 mPas at 20 ° C. The plastification takes place in a Papenmeier mixer with heatable and coolable double wall and a special stirrer system. The number of revolutions is continuously adjustable.

b) Production of the plastic composition

75 GT of the plasticised polyvinyl alcohol from Example 1a 24.7 GT PE-maleic anhydride copolymer (melt index at 190 ° C and 2.16 kg of 0.5 g / 10 minutes) and 0.3 pbw of an antioxidant ^(® Hostanox 03 ) mixed and compounded in a twin screw extruder. The processing temperatures in the extruder are 170 to 200 ° C. The strand thus obtained is processed into granules using a commercially available granulator.

c) Production of the film

The granules obtained in Example 1b become one in a Schwabenthan press

Foil processed.

The film has the following barrier properties:

Oxygen permeability at 23 ° C / 50% rel. Humidity: 0.46 [cm ³ x mm] / [m ² xdx bar] fuel permeability according to CEC legislative fuel RF-08-A-85 at

40 ° C in contact with the liquid fuel: <0.0006 [gx mm] / [m ² xd]

Example 2

a) Preparation of the plasticized polyvinyl alcohol

There are 1000 parts by weight (GT) of polyvinyl alcohol, 25 GT ^® Mowilith powder DM 117 P, 2.5 GT stearic acid, 180 GT glycerol, 50 GT water and 6 GT ^® Aerosil R 972 were used. The polyvinyl alcohol used is saponified to 99 mol%. A 4% aqueous solution has a viscosity of 15 mPas at 20 ° C. The plastification takes place in a Papenmeier mixer with heatable and coolable double wall and a special stirrer system. The number of revolutions is continuously adjustable.

b) Production of the plastic composition 75 pbw of the plasticized polyvinyl alcohol from example 2a are made with 24.7 pbw of PE-MSA copolymer (melt index at 190 ° C. and 2.16 kg of 4.1 g / 10 minutes) and 0.3 GT of an oxidation stabilizer ( ^® Hostanox 03) mixed and compounded in a twin screw extruder. The processing temperatures in the extruder are 210 to 220 ° C. The strand thus obtained is processed into granules using a commercially available granulator.

c) Production of the film

The granules obtained in Example 2b are processed into a film using a Göttfert blown film extruder, Buchen / Odenwald. The cylinder diameter of the extrusiometer is 30 mm, its length 25 D. The compression ratio of the core-progressive three-zone screw without mixing part and additional compression elements is 1: 2.5. The die head diameter is 30 mm, the gap width is 0.6 mm. The processing temperatures are between 200 and 220 ° C. The film has the following barrier properties:

Fuel permeability according to CEC legislative fuel RF-08-A-85 at 40 ° C in contact with the liquid fuel: <0.00025 [gx mm] / [m ² xd]

Example 3

a) Preparation of the plasticized polyvinyl alcohol

b) Production of the plastic composition 75 pbw of the plasticized polyvinyl alcohol from example 3a using 24.7 pbw of PE-MSA copolymer (melt index at 190 ° C. and 2.16 kg of 1.3 g / 10 minutes) and 0.3 GT of an oxidation stabilizer ( ^® Hostanox 03) mixed and compounded in a twin screw extruder. The processing temperatures in the extruder are 210 to 220 ° C. The strand thus obtained is processed into granules using a commercially available granulator.

c) Production of the film

The granules obtained in Example 3b are processed into a film in the same way as in Example 2c using a Göttfert blown film extruder. The film has the following barrier properties:

Oxygen permeability at 23 ° C / 50% rel. Humidity: 0.55 [cm ³ x mm] / [m ² xdx bar] Fuel permeability according to CEC legislative fuel RF-08-A-85 at 40 ° C in contact with the liquid fuel: <0.00002 [gx mm] / [m ² xd]

Comparative example

Analogously to Example 1c, a film is produced from ethylene-vinyl alcohol (EVOH) copolymer using a Schwabenthan press. The film has the following barrier properties: Oxygen permeability at 23 ° C / 50% rel. Humidity: 0.003 [cm ³ x mm] / [m ² xdx bar] Fuel permeability according to CEC legislative fuel RF-08-A-85 at 40 ° C in contact with the liquid fuel: <0.0006 [gx mm] / [m ² xd]

Claims

claims

1. Plastic composition containing 30 to 99 wt .-% of a plasticized polyvinyl alcohol and 1 to 70 wt .-% of a polyolefin-maleic anhydride copolymer.

2. Plastic composition according to claim 1, characterized in that the polyolefin in the copolymer is polyethylene or polypropylene.

3. Plastic composition according to claim 1, characterized in that the polyolefin in the copolymer is polyethylene.

4. Plastic composition according to at least one of claims 1 to 3, characterized in that the proportion of maleic anhydride in the polyolefin-maleic anhydride copolymer is 0.1 to 20 wt .-%.

5. Plastic composition according to claim 3 or 4, characterized in that the polyethylene-maleic anhydride copolymer has melt indexes which are in the range from 0.3 to 10 g / 10 minutes.

6. Plastic composition according to at least one of the preceding claims, characterized in that a fully saponified polyvinyl alcohol with a degree of hydrolysis of at least 98 mol% is used as the polyvinyl alcohol.

7. Plastic composition according to at least one of the preceding claims, characterized in that the polyvinyl alcohol has a viscosity in the range from 3 to 50 mPas.

8. Plastic composition according to at least one of the preceding claims, characterized in that the proportion of plasticizer in the plasticized polyvinyl alcohol is in the range from 5 to 50% by weight.

9. Plastic composition according to at least one of the preceding claims, characterized in that it contains up to 50 wt .-%, based on the total composition of polyolefins.

10. A method for producing a plastic composition according to at least one of the preceding claims, characterized in that the polyvinyl alcohol is first plasticized, this plasticizer-containing polyvinyl alcohol is then optionally mixed with the polyolefin-maleic anhydride copolymer and compounded using an extruder and then granulated.

11. The method according to claim 10, characterized in that the plasticized polyvinyl alcohol and the polyolefin-maleic anhydride copolymer are used in granular form.

12. The method according to claim 10 or 11, characterized in that both components are compounded at melt temperatures in the range of 170 to 240 ° C.

13. Shaped body containing a plastic composition according to at least one of claims 1 to 9.

14. Shaped body containing at least one layer of a plastic composition according to at least one of claims 1 to 9.

15. Use of a shaped body according to claim 13 or 14 as a barrier medium.

16. Use of a shaped body according to claim 13 or 14 for the production of fuel tanks.

17. Plastic container containing at least one layer of a plastic composition according to at least one of claims 1 to 9.