Multilayered composite material and objects made therefrom

Abstract

The present invention relates to a multilayer composite having barrier properties, objects, in particular fuel containers, comprising the same, a process for producing the multilayer composite or the objects comprising the same and also the use of the multilayer composite or the objects for reducing the emission of volatile organic compounds.

Claims

1. A multilayer composite having barrier properties for volatile organic compounds which have a vapor pressure of at least 0.01 kPa at 20 C. (293.15 K), wherein the multilayer composite has a first surface and a second surface and comprises at least one first layer and at least one further layer, wherein one of the two layers comprises at least one adsorption material for said volatile organic compounds and at least one polymeric support material in admixture with or bonded to the adsorption material, wherein if the at least one adsorption material and the at least one polymeric support material are bonded to one another, the composite comprises at least three layers, wherein the polymeric support material comprises a high density polyethylene (HDPE), and wherein the at least one adsorption material is selected from the group consisting of sheet and framework silicates, porous carbon material, metal organic frameworks (MOP) and mixtures thereof.

2. The composite as claimed in claim 1, wherein the content of adsorption material in the layer comprising adsorption material, if adsorption material and support material are present in admixture in one layer, or in the bonded assembly of the layer comprising adsorption material and the layer comprising support material is from 0.001 to 80% by weight, in each case based on the total weight of adsorption material and polymeric support material.

3. The composite as claimed in claim 1, wherein the specific surface area of the at least one adsorption material is at least 10 m.sup.2/g.

4. The composite as claimed in claim 1, wherein the adsorption material has pores having a diameter in the range from 0.1 to 10 nm.

5. The composite as claimed in claim 1, wherein the adsorption material has a porosity of at least 5%.

6. The composite as claimed in claim 1, wherein the at least one further layer comprises at least one polymeric material.

7. The composite as claimed in claim 1, wherein the at least one further layer comprises at least one polymeric material which has barrier properties in respect of volatile organic compounds.

8. The composite of claim 1, wherein said silicates comprise porous silicates.

9. The composite of claim 1, wherein said porous carbon material comprises activated carbon.

10. The composite of claim 1, wherein said metal organic frameworks comprise porous metal organic frameworks.

11. The composite of claim 1, wherein said framework silicates comprise zeolites.

12. The composite of claim 1, wherein said porous carbon material comprises covalent organic frameworks (COF).

13. An object for the accommodation, passage or envelopment of substances comprising volatile organic compounds, comprising the multilayer composite as claimed in claim 1.

14. The object as claimed in claim 13, wherein it is a film, a pipe, a hollow body or a closure or other component for such a hollow body.

15. The object as claimed in claim 13, wherein the at least one further layer of the composite comprises at least one polymeric material which has barrier properties in respect of volatile organic compounds where the layer which comprises this polymeric material having barrier properties is located closer to the surface of the object which is provided for contact with the substance comprising the volatile organic compound than the layer comprising adsorption material.

16. A process for producing a multilayer composite or an object as claimed in claim 1, which comprises a step for forming the at least one layer comprising adsorption material on the at least one further layer by means of (co)extrusion, injection molding, (co)extrusion blow molding or lamination.

17. The use of a multilayer composite or an object as claimed claim 1 for reducing the emission of volatile organic compounds.

18. A composite as claimed in claim 1, wherein the volatile organic compounds are selected from the group consisting of acyclic and cyclic aliphatic and aromatic, optionally branched and/or halogenated hydrocarbons and heteroaromatic compounds, alcohols, acetals, ketones, ethers, carboxylic acids and mixtures thereof.

Description

EXAMPLES

Example 1: Production of Test Plates with and without Adsorption Material

(1) A molecular sieve having a pore size of 4 [0.4 nm], for example BASF Molekularsieb 4A (BASF, Ludwigshafen, Germany), and a metal organic framework based on aluminum fumarate, known under the trade name Basolite A520 (BASF, Ludwigshafen, Germany), were used as adsorption materials. The synthesis of such metal organic frameworks is described, for example, in WO 2012/042410 A1.

(2) Spherical adsorption material was manually comminuted in a laboratory mortar. The ground material was passed through an analytical sieve having a metal wire mesh in accordance with DIN ISO 3310-1:2001 and a mesh opening of 500 m. The sieve fraction was used for the subsequent compounding with polymer. Pulverulent adsorption materials were used directly as obtained, without prior manual comminution, in the compounding with polymer.

(3) Mixtures containing 10% by weight of the respective adsorption material and 90% by weight of HPDE (Lupolen 4261 AG from LyondellBasell Industries, Rotterdam, the Netherlands) were homogenized on a Brabender Plasti-Corder W 50 EHT with Lab-Station drive and PC-controlled measuring unit (Brabender GmbH & Co. KG, Duisburg, Germany) having contrarotating kneading blades at 190 C. and 60 rpm for 5 minutes. The plastic melt obtained was pressed by means of a Schwabenthan specimen press Polystat 200 T (formerly Berlin, Germany) at 190 C. under a pressure of 90 bar for 5 minutes to give plates having the dimensions 200 mm100 mm1.6 mm. The plates were subsequently cooled to a temperature below 60 C. by means of the water cooling of the specimen press and demolded.

(4) As blank or comparative specimens, plates composed of 100% by weight of HPDE without adsorption material were produced by the above-described process.

Example 2: Lamination of the Test Plates with 5-Layer COEX Material

(5) A film produced by the coextrusion process and having the layer structure HDPE/bonding agent/EVOH/bonding agent/HDPE and a total thickness of 220 m, in which the thickness of the two HDPE layers (Lupolen 4261AG) was in each case 90 m, the thickness of the two bonding agent layers (Admer GT6, Mitsui Chemicals, Tokyo, Japan) was in each case 10 m and the thickness of the EVOH layer (EVAL F101A, Kuraray, Chiyoda, Japan) was 20 m, was used as 5-layer COEX material.

(6) This 5-layer film was laminated with the test plates described in example 1 in a Schwabenthan specimen press by in each case applying one of the test plates described in example 1 to one side of the film and pressing this structure at 190 C. under a pressure of 90 bar for 5 minutes, subsequently cooling the resulting laminate to a temperature below 60 C. by means of the water cooling of the specimen press and demolding the laminate.

(7) This example shows that layers comprising adsorption material as per the present invention can also be joined to multilayer coextruded materials using conventional lamination processes.

Example 3: Adsorption and Desorption Measurements

(8) Test plates having a weight of about 20 g and composed of pure HPDE (i.e. without laminated 5-layer film) without addition of adsorption agent (referred to as HPDE in table 1) as comparative specimen and also with addition of in each case 10% by weight of the molecular sieve specified in example 1 (referred to as MS in table 1) or metal organic framework (referred to as MOF in table 1) as adsorption agent were produced as described in example 1. These were exposed to a gaseous ethanol atmosphere at room temperature (about 20-23 C.) in glass containers. Absolute ethanol (denatured with 1% of methyl ethyl ketone), high purity, commercially available from, for example, VWR International GmbH (Darmstadt, Germany) under the catalog number APPCA5007.2500, was used as alcohol. The weight increase was determined over a period of 147 days by means of a Sartorius 2007 MP6 analytical balance (Sartorius, Gttingen, Germany).

(9) The percentage weight change of the test plates over time, in each case relative to the point in time t=0, and also the percentage ethanol loading resulting therefrom, based on the weight of the adsorption agent in the test plates, are shown in table 1. The indicated ethanol loading takes into account the weight loss of the HDPE component in the test plates by extraction of particular constituents from the polymer over time.

(10) TABLE-US-00001 TABLE 1 Ethanol Weight increase of the loading of the Time test plate [%] adsorbent [%] [Days] HDPE.sup.1 MS.sup.2 MOF.sup.3 MS.sup.2 MOF.sup.3 0 0 0 0 0 0 2 0.03 0.11 0.37 1.38 3.96 15 0.07 0.44 0.62 3.79 5.61 28 0.23 0.85 1.02 6.70 8.25 50 0.21 1.01 1.09 8.40 9.01 64 0.30 1.11 1.25 8.74 9.92 91 0.17 1.34 1.46 12.07 13.05 114 0.38 1.67 1.61 13.70 12.84 147 0.21 1.83 1.69 16.59 15.13 .sup.1Test plate composed of 100% by weight of HDPE .sup.2Test plate composed of 90% by weight of HDPE & 10% by weight of molecular sieve .sup.3Test plate composed of 90% by weight of HDPE & 10% by weight of metal organic framework

(11) The test plate which contained molecular sieve as adsorption agent and also the test plate composed of pure HDPE were subsequently taken from the ethanol atmosphere and stored for 7 days under ambient pressure in a vacuum drying oven VT 5042 EK (Heraeus) heated to 60 C. in order to examine the desorption properties. The weight decrease of the test plate was determined by means of the Sartorius 2007 MP6 analytical balance after storage at 60 C. for 24 hours and 48 hours and also 7 days.

(12) Here too, the percentage weight change of the test plates over time, in each case relative to the point in time t=0, and also the percentage ethanol loading resulting therefrom, based on the weight of the adsorption agent in the test plates, were determined. The ethanol loading indicated once again takes into account the weight loss of the HDPE component in the test plates by extraction of particular constituents from the polymer over time. The results are shown in table 2.

(13) TABLE-US-00002 TABLE 2 Weight change of the Ethanol loading of the Time test plate [%] adsorbent [%] [Days] HDPE.sup.1 MS.sup.2 MS.sup.2 148 (1).sup.3 0.02 1.54 15.55 149 (2).sup.3 0.08 1.48 15.42 154 (7).sup.3 0.10 1.47 15.52 .sup.1Test plate composed of 100% by weight of HDPE .sup.2Test plate composed of 90% by weight of HDPE & 10% by weight of molecular sieve .sup.3Total duration of the experiment from the point in time at which the test plates were first exposed to the ethanol atmosphere. The time for which only the desorption was examined is indicated in parentheses.

(14) These results show that addition of a suitable adsorption agent to a polymeric support material results in volatile organic compounds being able to be adsorbed in this modified support material and thus bound in the long term, sometimes even at comparatively high temperatures of, for example, 60 C.

(15) A commercial 6-layer COEX fuel container having a barrier layer of EVOH having a thickness of 100 m displays an emission loss of about 5 mg per day in a CARB 24 hr diurnal cycle when using LEVIII fuel.

(16) If such a fuel container is modified by adding 400 g of adsorption agent to the HDPE layer(s) located behind the EVOH barrier layer, viewed from the fuel side, corresponding to a modification of 50% by weight of the HDPE used in this fuel tank with 10% of adsorption medium, the emission of volatile organic compounds passing through the barrier layer can be prevented or reduced over many years by adsorption of these volatile organic compounds.

(17) Even if only a value of 8% of adsorbed ethanol, based on the mass of the adsorption material, were to be assumed as maximum value of the possible loading of the adsorption agent and virtually the entire emission loss of the fuel tank were to be attributed to the emission of ethanol, for example when using fuels having high ethanol contents, e.g. E85 or E100, such a fuel tank is able to bind 32 g of ethanol. On the basis of the abovementioned emission loss of the fuel tank of 5 mg per day, the time taken to reach this maximum loading of the adsorption agent with ethanol is 6400 days. The modified fuel tank is therefore able to adsorb the ethanol passing through the EVOH barrier layer and thus prevent the liberation thereof into the surroundings for a period of more than 17.5 years.

(18) Furthermore, the use of mixtures of different adsorption agents enables the adsorption behavior of the fuel tank to be matched to the emission profiles of different fuels.