THERMOPLASTIC POLYMER COMPOSITION WITH REDUCED MIGRATION OF STABILIZERS

Description

[0001] The present invention relates to thermoplastic polymer compositions with reduced migration of stabilizers and / or other ingredients. These thermoplastic polymer compositions contain at least one thermoplastic polymer that exhibits migration barrier properties for stabilizers or other ingredients, and, in one embodiment, at least one stabilizer component.

[0002] The functional barrier properties of various polymers and multilayer composite structures have not yet been sufficiently investigated in practice (see, for example, InnoLETTER of July 6, 2010, Rainer Brandsch, "Recycled cardboard and paper for food packaging? Migration of mineral oil from cardboard packaging into food can be minimized by incorporating a functional barrier," InnoLETTER, pp. 1-8, see www.innoform.de).

[0003] The functional barrier (FB) effect of polymers, polymer blends, and composite structures has been investigated primarily in relation to the permeability of gases such as oxygen, carbon dioxide, nitrogen, and / or water vapor. Functional barrier properties of polymers and multilayer composite structures against substances such as organic molecules are described in the scientific literature in the form of specific material constants and thermodynamic material constants. This enables material selection to protect, for example, the contents of packaging (such as food) against contamination by substances of potentially toxicological or olfactory relevance.

[0004] For long-term use of packaging systems, for example, a risk assessment and a resulting action plan can be developed based on the functional barrier properties of the materials. This can ensure the safe use of packaging materials, including printing inks, varnishes, coatings, adhesives, etc., for food or pharmaceuticals, for example. This generally eliminates the need for time-consuming and costly laboratory tests or reduces them to a minimum.

[0005] DE 103 59 450 A1 discloses thermoplastic molding compositions comprising, the sum total adding up to 100% by weight, a) at least one block copolymer A comprising in polymerized form, based on A, a1) 10 to 90% by weight of at least one styrene monomer, and a2) 10 to 90% by weight of at least one diene monomer, and as stabilizers, based on the molding composition, b) 0.001 to 0.5% by weight of at least one phenolic acrylate B, c) 0.05 to 1% by weight of at least one organic phosphite C, and d) 0.001 to 1% by weight of at least one stabilizer compound D selected from sterically hindered phenols which differ from the phenolic acrylate B, and aromatic amines.

[0006] Therefore, one object of the invention is to provide a cost-effective, thermoplastic polymer composition with reduced migration of the stabilizer(s) or ingredients contained therein. The thermoplastic polymer composition can be used to produce composite systems with two or more layers.

[0007] The following describes a thermoplastic polymer composition (A) with reduced migration, which contains at least 50 wt.%, often at least 80 wt.%, based on the polymer composition (A), of at least one thermoplastic polymer (P) which has migration barrier properties, in particular for stabilizer(s).

[0008] This polymer composition (A) contains at least 0.1 wt.%, in particular 0.1-2.0 wt.%, based on the polymer composition (A), of at least one stabilizer component (S). It frequently also contains other ingredients or additives.

[0009] The invention relates in particular to a thermoplastic polymer composition (A) with reduced migration of stabilizers (S) and / or further ingredients (I), containing 50 to 99.9 wt.%, in particular at least 50 wt.%, often at least 80 wt.%, based on the polymer composition (A), of at least one thermoplastic polymer (P) which has migration barrier properties for stabilizers, and at least 0.1 wt.%, often 0.1 to 2.0 wt.%, based on the polymer composition (A), of at least one stabilizer component (S) and / or at least 0.1 wt.%, often 0.1 to 2.0 wt.%, based on the polymer composition (A), of at least one further ingredient (I), wherein the following applies to the thermoplastic polymer composition (A): a) the glass transition temperature T g of the thermoplastic polymer (P) is above the maximum service temperature of 50 °C, and b) the polymer-specific constant for polymers (AP ) of the thermoplastic polymer (P) is less than 1, wherein the polymer-specific constant for polymers (AP ) is determined as disclosed in the description, and c) the diffusion coefficient (DP ) of the thermoplastic polymer (P) for mineral oil derived therefrom is less than 10 -12< cm 2< / s at 20 °C, wherein the diffusion coefficient (DP ) is determined as disclosed in the description, and d) the morphology of the thermoplastic polymer (P) is two-phase heterogeneous, wherein, in the case of a two-phase heterogeneous morphology of the thermoplastic polymer (P), a polymer component (Pp) with the higher AP value and the higher diffusion coefficient (DP ) is present as a discontinuous phase in particle form with a weight-average particle size (D) of 20 nm to 10 µm, is embedded in a polymer component (P m ) with a lower AP value and lower diffusion coefficient (DP ), and wherein the morphology of the thermoplastic polymer (P) does not have a co-continuous structure.

[0010] Migration barrier properties mean that the migration of the stabilizer or other ingredient in the polymer composition is prevented or at least slowed. Heterogeneous morphology means that there is no homogeneous structure in the polymer or polymer mixture. This can be assessed, for example, by microscopic examination.

[0011] One embodiment of the invention relates to a thermoplastic polymer composition (A) with reduced migration, which contains as thermoplastic polymer (P) a styrene-containing polymer with a glass transition temperature T g of at least 60 °C, in particular at least 70 °C.

[0012] The thermoplastic polymer composition (A) with reduced migration, in particular for stabilizers, preferably contains as thermoplastic polymer (P) a styrene-containing polymer component, in particular from the group consisting of polystyrene (PS), in particular HIPS and GPPS, and SBS copolymer / PS blends.

[0013] Preferably, SBC copolymer / PS blends are used in the composition.

[0014] A further embodiment of the invention relates to a thermoplastic polymer composition (A) with reduced migration, which contains at least one stabilizer component (S) from the group consisting of antioxidants and light stabilizers, and / or at least one further ingredient (I) from the group consisting of residual monomers and oligomers. The various stabilizer components (S) and further ingredients (I) will be described in detail below.

[0015] A further embodiment of the invention relates to a thermoplastic polymer composition (A) with reduced migration, which contains 0.1 to 2.0 wt. %, often 0.1-1.0 wt. %, based on the polymer composition (A), of at least one stabilizer component (S), in particular at least one antioxidant. These are described below.

[0016] The invention further relates to a composite structure, particularly suitable for packaging purposes, comprising at least two different layers (S). At least one layer (S1) consists of, or largely consists of, a thermoplastic polymer composition (A) with reduced migration as described above.

[0017] This composite structure for packaging purposes often contains at least two different layers, with at least one layer (S1) consisting largely of a thermoplastic polymer composition (A) made of, in particular, polystyrene (PS), SBS copolymer / PS blends, and / or SBC copolymer / PS blends, and at least one further layer (S2) consisting largely of a non-styrene-containing thermoplastic polymer composition (A2). This further thermoplastic polymer composition (A2) can consist, for example, of polyester, polyurethane, and / or polyamide.

[0018] The invention further provides a process for producing a thermoplastic polymer composition (A) with reduced migration of stabilizers (S) and / or other ingredients (I), as described above, in which at least one thermoplastic polymer (P) having migration barrier properties is mixed with at least one stabilizer component (S) and, if appropriate, other polymer additives. The other polymer additives are described below.

[0019] The invention further relates to the use of a thermoplastic polymer composition (A) with reduced migration of stabilizers (S) and / or further ingredients (I), as described above, for the production of films, fibers or moldings.

[0020] The invention also relates to the use of a composite structure as described, comprising at least two different layers, in which at least one layer (S1) consists of a thermoplastic polymer composition (A) with reduced migration, for providing packaging with increased resistance to delamination. Delamination refers to the separation of layers in the composite structure. This is a technical challenge, particularly in the case of multiple layers, e.g., layer (S1) as described above, from (S2) and / or (S3).

[0021] The barrier properties of polymers against organic molecules are described in particular by the so-called polymer-specific constant (AP value).

[0022] This is described by T. Begley, L. Castle et al. in "Evaluation of migration models that might be used in support of regulations for food contact plastics" (Food Additives and Contaminants, January 2005; 22(1): 73-90). The following equation (1) applies to the polymer-specific constant AP. A P = A P ′ - τ / T

[0023] The polymer-specific constant (Ap value) described in the 2005 publication consists of a temperature-independent component, Ap', and the temperature-dependent contribution to the activation energy (τ, Tau). In Equation 1, T represents the temperature.

[0024] Table 1 describes the polymer-specific constant AP of some common polymers that can be used, among other things, for the production of packaging. Polymer-specific constants (A p ) for polymers

[0025] polymer AP ' S AP'(max) AP ' (min) N t AP '* T LDPE 10.0 1.0 11 7.0 27 1.7 11.7 0 HDPE 10.0 1.9 12.6 5.0 49 1.68 13.2 1577 PP 9.4 1.8 12.9 6.2 53 1.68 12.4 1577 PET 2.2 2.5 7.2 -4.3 58 1.67 6.35 1577 PEN -0.34 2.4 3.8 -5.5 38 1.7 3.7 1577 PS -2.8 1.25 0.0 -6.5 32 1.7 -0.7 0 HIPS -2.7 1.67 0 -6.2 33 1.7 0.1 0 PA (6.6) -1.54 2.0 2.3 -7.7 31 1.7 1.9 0

[0026] The polymer-specific constant AP is a measure of the mobility of the polymers at the molecular level and thus allows to estimate their barrier properties (or diffusion properties).

[0027] Flexible polymers, e.g. polyethylene (LDPE) or plasticized polyvinyl chloride (soft PVC), generally have a high mobility, ie they have correspondingly higher AP values and diffusion coefficients Dp, which leads to low barrier properties.

[0028] Stiffer polymers, such as polyethylene terephthalate (PET) or polyamide (PA), are generally characterized by lower mobility, ie they have correspondingly lower Ap values and diffusion coefficients DP and therefore lead to better barrier properties.

[0029] The diffusion equation describes the diffusion coefficient (DP ) as follows: D P ∼ exp A P − 0 , 1351 Mr 2 / 3 + 0 , 003 Mr − 10454 / T

[0030] The polymer-specific constant AP describes the polymer matrix (e.g., free volume, chain mobility) and is temperature dependent, as shown above in Equation 1. Mr is the molecular weight of the migrant (e.g., stabilizer, additive); T is the temperature.

[0031] The solubility of the migrating additive in the polymer or polymer composition further contributes to the barrier effect of polymers. Solubility is substance-specific and, with the exception of a few media, such as water, has only been described to a limited extent in the literature. If the solubility of the substance in the polymer is low, the barrier effect of the polymer against this substance is generally high.

[0032] A classic example of this is the good barrier properties of polyethylene (PE) against water and water vapor, because water is insoluble in PE. The migrating substance also influences the barrier effect of the polymer through its molecular size. Small molecules, such as solvents such as acetone, migrate through a polymer faster than large molecules, such as common polymer additives. A practical example from application is low-migration printing inks, in which large molecules, such as polymer photoinitiators, are deliberately used to ensure low migration values.

[0033] The thickness of the polymer product itself also influences its barrier effect. Thick polymer layers, such as those used in cups or bowls, have a higher barrier effect than, for example, thin films made of the same polymer. Temperature has a significant influence on the migration rate, meaning the same substance migration is achieved within a few hours under sterilization conditions (high temperature) and within a few years at room temperature (20°C).

[0034] Whether the barrier effect (functional barrier) of a polymer is sufficient with regard to a specific application (filling material, storage time, storage temperature) can be assessed by taking a holistic view of all influencing factors (polymer type and polymer thickness, migrating substance and its molecular weight and solubility in the polymer, storage time and storage temperature, type of filling material).

[0035] Mineral oil can be used to investigate barrier properties. For example, if the barrier effect of polymers against mineral oil (average molecular weight 300-520 g / mol) is examined at room temperature (approx. 20 °C), a sensible material selection for packaging solutions can be made based on the polymer-specific constants (AP value). A high AP value means low barrier effect, and a low AP value means high barrier effect. Accordingly, LDPE has little barrier effect against mineral oil. PET and polystyrene exhibit very good barrier effect even at low thicknesses (approx. 10 µm). Table 2 shows polymer-specific constants (AP ) for polymers and derived diffusion coefficients (DP ) for mineral oil at RT (20°C): DP [cm 2 / s] AP Gases ∼ 10 -1< Liquids ∼ 10 -5< 20 viscous liquids ∼ 10 -6< 18 soft PVC ∼ 10 -7< 16 Polymers T > T g LDPE ∼ 10 -9< 11 HDPE ∼ 10 -10< 9 PP ∼ 10 -11< 7 Polymers T < T g PA ∼ 10 -13< 2 PS ∼ 10 -14< approx. 0 PET ∼ 10 -15< -2 hard PVC ∼ 10 -16< -4

[0036] T g is the glass transition temperature; T< T g means that the application temperature is below the glass transition temperature of the polymer.

[0037] From the AP value, the molecular weight of the migrant and the temperature, the diffusion coefficient of mineral oil in the respective polymer can be estimated and used for the concrete application-related simulation of the migration, the so-called migration modeling based on the diffusion law.

[0038] However, real packaging systems often consist of several materials and / or items such as a bottle and lid or a thermoformed tray and lidding film. In addition, there are labels, banderoles, sliders, folding boxes, outer packaging, transport packaging, etc., which partially or completely surround the contents (solid, liquid, pasty). Some materials or items in the packaging system are in direct contact with, for example, food or pharmaceuticals, while others are not. The transfer of mineral oil from recycled cardboard or paper mostly occurs via the gas phase. The transfer via the gas phase is possible because mineral oil is sufficiently volatile to be desorbed from, for example, a cardboard fiber and adsorbed onto the inner packaging material or directly onto the food.

[0039] The volatility of a substance can be expressed by its vapor pressure at a given temperature. It should be noted that the vapor pressure of the substance can differ significantly from the vapor pressure of the adsorbed or dissolved substance. Low molecular weight mineral oils are more volatile than high molecular weight ones. The transfer of mineral oil to food is determined by two essential parameters: firstly, the specific surface area of the food, on which the mineral oil is adsorbed relatively non-specifically, and secondly, the freely available or accessible fat content of the food, in which medium to non-polar substances dissolve well, i.e. are preferentially absorbed. A high specific surface area of food, such as flour, rice, cereals, as well as a fat content, e.g. of several percent in food, such asChocolate products or sandwiches can be expected to have high mineral oil migration values if recycled cardboard or paper is used for packaging.

[0040] By analogy with the functional barrier within a material or article, the concept of a functional barrier can be extended to a composite structure. To do so, it is useful to consider the composite structure as concentric layers (S) that at least partially surround each other.

[0041] Which layer (S) should enclose the contents (e.g. inner bag) compared to other layers further out (e.g. transport packaging made of (recycled) cardboard) can be varied with regard to the functional barrier properties of the composite structure. The time (t) required by a substance (e.g. stabilizer component) to migrate from the outside (e.g. outer packaging) through a functional barrier (FB) layer (e.g. made of polymer composition) is also called breakthrough time (Theta, Θ) (see Figure 3 ).

[0042] According to the following equation 3, this breakthrough time (Theta) is directly proportional to the thickness (d) of the layer (S), e.g. of an inner bag, d P squared, and inversely proportional to the diffusion coefficient (D FB ) of the material of the functional barrier (FB), e.g. of the thermoplastic composition (A). θ = 1 6 ⋅ d P 2 D FB θ − Durchbruchzeit d − Dicke D − Diffusionskoeffizient

[0043] The mode of action of a functional barrier (FB) is also shown in the figures of the Figures 1 and 2 If no functional barrier property of the polymer layer (S) is present, the time course of the migration is as in Figure 1 shown. If the migration of the substance (e.g. stabilizer) is determined at two arbitrary points in time and the two points are connected by a straight line, this straight line will always intersect the y-axis, which describes the migration: migration (m F, t / A ) at a positive value (I > 0).

[0044] However, if a functional barrier property of the polymer layer (S) is present, a temporal course of migration as in Figure 2shown. If the migration of the substance (e.g. stabilizer) is determined at two arbitrary points in time and the two points are connected by a straight line, the straight line will intersect the y-axis (migration, m F, t / A ) at a negative value (I < 0) if one point in time is within the breakthrough time (theta).

[0045] A functional barrier made of a polymer composition (A) is effective against a stabilizer component (or other ingredient) if the breakthrough time (theta) is as long as possible. During the breakthrough time, no transfer or migration of the stabilizer component from outside the functional barrier (FB) into, for example, the contents (to be protected) occurs.

[0046] This can also be achieved by using thicker layers of material, but this does not seem to be very effective from an ecological and economic point of view.

[0047] In the case of, for example, bottles, cups and bowls made of polymers, material thicknesses of several hundred micrometers are often common, so the breakthrough times of substances are particularly important.

[0048] Materials with good functional barrier properties such as the polymer compositions (A) and multi-layer composite structures (S) containing at least one such polymer layer (S1) therefore represent a technologically cost-effective option. The use of compositions through which substances (such as stabilizers) migrate very slowly is more effective.

[0049] In compositions (A), substances such as stabilizers exhibit a low diffusion coefficient (D FB ) and a low migration rate. If the diffusion coefficient of a material is known at a given temperature, the breakthrough time can be calculated.

[0050] In Figure 3The qualitative contribution of material selection with regard to the functional barrier effect is presented. A polymer with a low polymer-specific constant (AP value) leads to a low diffusion coefficient (D FB ) and a correspondingly long breakthrough time (Θ). Low solubility of the organic molecule (e.g., the stabilizer) in the polymer (c FB ) leads to low concentrations of the substance in the plastic and thus to a high distribution coefficient (KP,FB ). The linear portion of the curve is correspondingly flat, resulting in only low migration values (mt) even after a long period of time.

[0051] The diffusion coefficient (D FB ) in Figure 3On the one hand, it describes the rate at which a substance migrates into a plastic. On the other hand, the partition coefficient (KP,FB ) describes the relative solubility of a substance between adjacent layers / layers of a composite structure (e.g., in packaging). Based on these two coefficients, the functional barrier properties of the polymer compositions (A) in composite structures with multiple layers (S1, S2, etc.) or in packaging systems can be estimated in relation to another ingredient (e.g., mineral oil).

[0052] In Figure 4The quantitative migration of mineral oil (ODP) in the polymers general purpose polystyrene (GPPS), HIPS, LDPE, polypropylene, and PET is presented (each at 0.2 wt.% ODP, 10 days at 40°C and a layer thickness of 0.25 mm). It is evident that polyethylene and polypropylene have poor migration barrier properties, whereas polystyrene and HIPS can be good migration barriers, even at small layer thicknesses.

[0053] Figure 5 shows the limiting thickness ("infinitife thickness", CF,t ) of films made of various polymer materials, namely polystyrene (GPPS, HIPS), PET, polypropylene, and low-density polyethylene (each 0.2 wt.% ODP, 10 days at 40°C and a layer thickness of 0.25 mm). It is evident that with polyethylene and polypropylene, large polymer layer thicknesses are required to create a migration barrier, whereas with polystyrene, good migration barriers can be achieved even at micrometer-thick layers.

[0054] The invention generally provides a thermoplastic polymer composition (A) with reduced migration. It contains a polymer composition (A) with at least one thermoplastic polymer (P) that has migration barrier properties, in particular for stabilizers, as well as at least one stabilizer component (S) and / or at least one further ingredient (I), such as monomers (such as styrene) or oligomers (e.g., trimers, etc.). The above-mentioned conditions apply to the thermoplastic polymer composition (A).

[0055] In the case of a two-phase morphology of the thermoplastic polymer (P), one polymer component (Pp) with the higher Ap value and the higher diffusion coefficient (DP ) is embedded as a discontinuous phase in particle form with a weight-average particle size (D) of 20 nm to 10 µm in a polymer component (PM ) with a lower Ap value and lower diffusion coefficient (DP ).

[0056] The morphology of the thermoplastic polymer (P) should not have a co-continuous structure, it is two-phase heterogeneous.

[0057] The morphology of the thermoplastic polymer (P), preferably polystyrene or polystyrene / SBC blend, is particularly not co-continuous. Co-continuous structures include, for example, "bis-continuous double diamond" structures, cylindrical structures (e.g., polybutadiene cylinders in a polystyrene matrix), lamellar structures (e.g., polybutadiene lamellae in a polystyrene matrix), and interpenetrating networks (IPNs).

[0058] The glass transition temperature T g of the thermoplastic polymer (P) is preferably above 50°C, often above 60°C, in particular above 70°C.

[0059] The service temperature of the polymer is often in the range of room temperature (20°C) or in the cooling range (-20°C) to normal transport temperature range (up to 40°C, maximum 50°C).

[0060] The polymer specific constant for polymers (AP ) of the thermoplastic polymer (P) is less than 1.0, for example -2.0 to 0.95, in particular -1.8 to 0.93.

[0061] The diffusion coefficient (DP ) of the thermoplastic polymer (P) for mineral oil is preferably less than or equal to 10 -12< cm 2< / s at 20 °C.

[0062] Both standard polystyrene (GPPS, General Purpose Polystyrene, manufacturer e.g., INEOS Styrolution) and impact-resistant polystyrene, such as HIPS (High Impact Polystyrene, manufacturer e.g., INEOS Styrolution), are suitable as thermoplastic polymers (P). Blends of PS and SBS copolymers or blends of PS and SBC copolymers that meet the above criteria are also frequently used.

[0063] The at least one stabilizer component (S) is selected, for example, from the group containing antioxidants and light stabilizers.

[0064] In one embodiment, the thermoplastic polymer composition (A) with reduced migration contains from 50 to 99.9% by weight, based on the polymer composition (A), of at least one thermoplastic polymer (P), and from 0.1 to 2.0% by weight, based on the polymer composition (A), of at least one stabilizer component (S) and / or at least one further ingredient (I).

[0065] The polymer composition (A) often contains 70 to 99 wt.%, based on the polymer composition (A), of at least one thermoplastic polymer (P), or often a mixture of two or more polymers, such as polystyrene and styrene copolymer (such as SB copolymer).

[0066] In a further embodiment, the thermoplastic polymer composition (A) with reduced migration of stabilizer (S) and / or further ingredients (I) contains as thermoplastic polymer (P) a styrene-containing polymer with a glass transition temperature T g of at least 60 °C, in particular at least 70 °C, and (optionally) as stabilizer component (S) up to 5 wt.%, in particular 0.1 to 2.0 wt.%, often 0.1 to 1.0 wt.%, based on the polymer composition (A), of at least one antioxidant as an additive.

[0067] Often the thermoplastic polymer (P) is a styrene-containing polymer component, preferably from the group of polystyrenes (PS), in particular HIPS and GPPS, or a blend of styrene-containing polymer component and S / B block copolymer, e.g. an SBS copolymer / PS blend or SBC copolymer / PS, e.g. PS-SBC blend.

[0068] The stabilizer component (S) preferably contains at least one stabilizer from the group of antioxidants.

[0069] Such antioxidants have, for example, one or more sterically protected phenolic OH groups, and / or phosphite units and / or sulfur compounds. Examples of suitable antioxidants are: 2,6-Di-tert-butyl-p-cresol 2,2'-Methylen-bis-(4-methyl-6-tert.-butyl-phenol) 2,2'-Methylen-bis-(4-methyl-6-cyclohexyl-phenol) 2,2'-Methylen-bis-(6-tert-butyl-4-ethylphenol) Octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionat Pentaerythritol-tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionat) Octyl-3,5-di-tert-butyl-4-hydroxy-hydrocinnamat Triethylenglycol-bis-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionat Thiodiethylen-bis-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionat] N,N'-Hexan-1,6-diylbis[3-(3,5-di-tert-butyl-4-hydroxyphenylpropionamid] 6,6'-di-tert-butyl-4,4'-butylidendi-m-cresol 1,3,5-Trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzol 2,4-Bis(octylthio)-6-(4-hydroxy-3,5-di-tert-butylanilino)-1,3,5-triazin 2-Methyl-4,6-bis(octylsulfanylmethyl)phenol Phenol, 4-methyl-, reaction products dicyclopentadiene and isobutylene 1,2-Di[-(3,5-di-tert-butyl-4-hydroxyp-henyl)propionyl]hydrazin 3,3'-Bis(3,5-di-tert-butyl-4-hydroxyphenyl)-n,n'-bipropionamid 2-(1,1-Dimethylethyl)-6-[[3-(1,1-dimethylethyl)-2-hydroxy-5-methylphenyl]methyl]-4-methylphenylacrylat 2-(1-(2-Hydroxy-3,5-di-tert-pentyl-phenyl)ethyl)-4,6-di-tert-pentylphenyl acrylat 2-tert-Butyl-6-methyl-4-[3-(2,4,8,10-tetratert-butylbenzo[d][1,3,2]benzodioxa-phosphepin-6-yl)oxypropyl]phenol 2-(1,1-Dimethylethyl)-6-[[3-(1,1-dimethylethyl)-2-hydroxy-5-methylphenyl]methyl]-4-methylphenylacrylat 1,3,5-Tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1 H,3H,5H)-trion 4,4',4"-(1-Methylpropanyl-3-ylidene)tris(6-tert-butyl-m-cresol) 3,9-Bis{2-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1-dimethylethyl}-2,4,8,10-tetraoxaspiro[5.5]undecan 4,4'-Thiobis(2-tert-butyl-5-methylphenol) Ethylen bis[3,3-bis[3-(1,1-dimethylethyl)-4-hydroxyphenyl]butanoat] 2,4-Dimethyl-6-(1-methyl pentadecyl) phenol Hexamethylen bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionat] TNPP (Tris-nonylphenyl)phosphit Diethyl 3,5-Di-tert-butyl-4-hydroxybenzylphosphonat Calcium-diethyl-bis[[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]-methyl]phosphonate] Tocopherol Tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanurate 3-tert-butyl-2-hydroxy-5-methylphenyl sulfide 4-[[4,6-Bis(n-octylthio)-1,3,5-triazin-2-yl]amino]-2,6-di-tert-butylphenol Benzenepropanoic acid 3,5-bis(1,1-dimethylethyl)-4-hydroxy-,C13-15-alkyl ester Tris(2,4-di-tert-butylphenyl)phosphite others organophosphorus stabilizers. ,

[0070] Examples of stabilizers that were preferred were: (2-tert-butyl-6-[(3-tert-butyl-2-hydroxy-5-methylphenyl)-methyl]-4-methylphenyl-prop-2-enoate); TNPP (tris-nonylphenyl)phosphite. Examples of other ingredients that were preferred were: white oil, lubricants, styrene oligomers.

[0071] Combinations of different stabilizers are often used, with a total of up to 2.0% by weight of stabilizers, based on the polymer composition (A), preferably being used.

[0072] The invention further relates to a composite structure, particularly suitable for packaging purposes, comprising at least two different layers, wherein at least one layer (S1) consists of a thermoplastic polymer composition (A) with reduced migration of stabilizers as described above.

[0073] This layer (S1) is preferably facing the inside of packaging, e.g. for contact with food.

[0074] In one embodiment, the composite structure contains at least two different layers, in which at least one layer (S1) consists of a thermoplastic polymer composition (A) with reduced migration, and a second layer (S2), and optionally further layers S3, S4, S5, wherein the composite structure is suitable for providing packaging with increased resistance to delamination.

[0075] The invention further relates to a process for producing a thermoplastic polymer composition (A) with reduced migration, in which at least one thermoplastic polymer (P) exhibiting migration barrier properties for stabilizers is mixed with a stabilizer component (S) and, if appropriate, further polymer additives that differ from component (S). Various processes for mixing or compounding thermoplastic compositions with additives are known to the person skilled in the art. The stabilizer component(s) can also be incorporated into the composition in the form of masterbatches.

[0076] By analogy with the functional barrier within a material or article, the inventive concept of a functional barrier can be extended to an entire packaging system. To achieve this, it is expedient to construct a packaging system as concentric layers that at least partially surround one another. Materials or articles are sometimes not in direct contact with one another, but rather, there may be air or another gas between them.

[0077] According to Article 1, EU Framework Regulation (EC) No. 1935 / 2004 of October 2004 applies to materials and articles, including active and intelligent food contact materials and articles, which are intended to come into contact with food as a finished product or are already in contact with food and are intended, or can reasonably be foreseen, to come into contact with food or to transfer their components to food during normal or foreseeable use.

[0078] According to the invention, it was also investigated which polymeric materials or products that can enclose a possibly sensitive filling material (e.g. food) (e.g. inner bag) have good functional barrier properties compared to other materials located further out (e.g. transport packaging made of recycled cardboard or polymer).

[0079] Similarly, it was investigated whether, for example, a film or a molded body (tray) made of the above-mentioned polymer composition possesses functional barrier properties against substances from an applied label, or whether a substrate made of a polymer composition represents a good functional barrier against substances from the applied printing ink (e.g., photoinitiators, stabilizers). The time required for a substance to migrate from the outside (e.g., outer packaging or printing ink) through a functional barrier (e.g., primary packaging or substrate) is also called the breakthrough time θ (theta). According to equation 4, this breakthrough time is directly proportional to the thickness of the inner bag, d P squared, and inversely proportional to the diffusion coefficient D FB of the substance in the functional barrier (FB): θ = 1 6 ∗ d p 2 D FB

[0080] The mode of action of a functional barrier is also shown in the figures of the FIG. 1 and FIG.2where the migration (m F,t / A ) is plotted against time (t).

[0081] If there is no functional barrier or if the migrating substance is in the food contact layer, a time course of migration can be observed, which corresponds to the graph of FIG. 1 If the migration of the substance is determined at two arbitrary points in time and the two points are connected by a straight line, the straight line will always intersect the y-axis (migration, m F,t / A ) at a positive value (I > 0).

[0082] If a functional barrier is present, a temporal course of migration can be observed, which corresponds to the graph of FIG. 2If the migration of the substance is determined at two arbitrary points in time and the two points are connected by a straight line, the straight line will intersect the y-axis (migration, m F,t / A ) at a negative value (I < 0) if one point in time is within the breakthrough time θ ( lag time ). A functional barrier (FB) made of a polymer is effective against a substance if the breakthrough time θ is as long as possible. During the breakthrough time, no transfer / migration of the substance from outside the FB into the contents occurs.

[0083] This can be achieved by applying a thick layer, which is not very effective from the point of view of resource conservation and economic efficiency.

[0084] However, in the case of polymer bottles, cups, and bowls, for example, material thicknesses of several hundred micrometers are not uncommon. Accordingly, the penetration times of these materials are longer than for films of the same material.

[0085] The use of materials such as glass or metal as an absolute barrier against the migration of substances in the field of flexible packaging appears only as a hypothetical option due to several disadvantages.

[0086] Materials with functional barrier properties, such as polymers and multilayer composites, represent a technologically feasible, cost-effective option. The most effective approach is to use materials through which substances can migrate very slowly. In barrier materials, substances exhibit low diffusion coefficients D FB , i.e., a low migration rate. Diffusion coefficients can sometimes be found in the literature or can be estimated using scientifically recognized methods. If the diffusion coefficient of a substance in a material is known at a given temperature, the breakthrough time can be calculated using the above equation.

[0087] In the investigations according to the invention, the qualitative contribution of the material selection with regard to the functional barrier effect was presented.

[0088] Polymers with a low polymer-specific constant (AP value) lead to low diffusion coefficients (D FB ) and correspondingly long breakthrough times θ. Low solubility of the migrant (e.g., organic additive) in the polymer (c FB ) leads to low concentrations of the additive in the polymer and thus to a high distribution coefficient (KP,FB ). The linear portion of the curve is correspondingly flat, resulting in low migration values (mt) even after long periods.

[0089] FIG. 3describes the constant "diffusion coefficient" (D FB ). It describes the rate at which a substance migrates into a polymer. On the other hand, the "partition coefficient" (KP,FB ) describes the relative solubility of a substance (e.g., an additive) between adjacent layers of a composite system (e.g., packaging). Based on these two coefficients, the functional barrier properties of polymers in multilayer composite structures or packaging systems can be calculated or estimated in relation to an additive, such as mineral oils or stabilizers. This allows the effectiveness of a functional barrier against migratory substances to be determined.

[0090] FIG. 4Describes the different solubility (c FB ) of an additive (0.2% ODP) in various polymers and the associated different migration (10 days at 40°C). This is particularly low for the styrene-containing polymers GPPS and HIPS. The K value is the distribution coefficient of the migrating additive in a system consisting of polymer and food simulant (solvent). A K value (more precisely KP / L ) of 1 indicates that a migrating additive (e.g. ODP) is present in the polymer at equilibrium 1 x more than in the solvent. In the presence of 50% ethanol, the K value for PE and PS approaches 1.

[0091] FIG. 5 describes the "indefinite thickness" for various polymers (polystyrene, PET, polypropylene and LD-polyethylene) (additive 0.2% ODP; 10 days at 40°C), which is particularly low for styrene-containing polymers such as PS.

[0092] The glass transition temperature of a polymer is also important for the barrier effect against the migration of polymer additives. The polymer EPP, a particularly tough foam made from expanded polypropylene, is usually foamed by the user. Due to the low T g of PP (5 °C), the chain mobility of PP at room temperature is so high that PP granules loaded with a foaming agent (e.g. pentane) lose their foaming agent within a very short time (during storage or transport). In contrast, EPS (expandable polystyrene) can be loaded with the foaming agent pentane at the manufacturer's plant as granules without any significant loss of pentane during storage and transport. This is due to the high T g of polystyrene, which only drops to around 80 °C even when mixed with up to 5% pentane and is high enough to prevent chain mobility at room temperature.

[0093] Other suitable additives include: Other light stabilizers that can be used include all common light stabilizers, for example compounds based on benzophenone, benzotriazole, cinnamic acid, and sterically hindered amines (HALS).

[0094] Examples of suitable lubricants include hydrocarbons such as oils, paraffins, PE waxes, PP waxes, fatty alcohols with 6 to 20 carbon atoms, ketones, carboxylic acids such as fatty acids, montanic acid or oxidized PE wax, carboxylic acid amides and carboxylic acid esters, e.g. with alcohols, ethanol, fatty alcohols, glycerol, ethanediol, pentaerythritol and long-chain carboxylic acids as acid components.

[0095] Conventional antioxidants, for example phenolic antioxidants, e.g., alkylated monophenols, esters and / or amides of 3-(3,5-di-tertiary-butyl-4-hydroxyphenyl)propionic acid and / or benzotriazoles, can be used as stabilizers. (Tris-nonylphenyl) phosphite can also often be used. Examples of antioxidants are also mentioned in EP-A 698637 and EP-A 669367 or in the Plastics Additives Handbook (H. Zweifel, Munich 2009). Examples of phenolic antioxidants that can be used include 2,6-di-tertiary-butyl-4-methylphenol, pentaerythrityl tetrakis-[3-(3,5-di-tertiary-butyl-4-hydroxyphenyl)propionate, and N,N'-di-(3,5-di-tertiary-butyl-4-hydroxyphenylpropionyl)hexamethylenediamine. The stabilizers mentioned can be used individually or in mixtures.

[0096] The polymer compositions (A) according to the invention can, for example, be pelletized or granulated, or processed by generally known processes, for example by extrusion, injection molding or calendering, into films, tubes, fibers, profiles, shoe shells, technical molded parts, consumer articles, molded articles of all kinds, coatings and / or blow molded articles.

[0097] The invention is explained in more detail by the examples, figures and claims. Examples

[0098] To illustrate the technical advantages of the invention, the migration of three different additives was investigated: (Antioxidant 1): Sumilizer GM (phenolic stabilizer from Sumitomo Chemical, JP) (2-tert-butyl-6-[(3-tert-butyl-2-hydroxy-5-methylphenyl)-methyl]-4-methylphenyl prop-2-enoate); (Antioxidant 2): TNPP (phosphite stabilizer) (tris-nonylphenyl)phosphite; (Mineral Oil): commercially available white oil (plasticizer, e.g. from Eni Oilproducts).

[0099] The following polymers were used: SBS1: Styrolux 3G55 (INEOS Styrolution, Frankfurt), a coupled (star-shaped) SBS polymer with a gross composition: 74% styrene / 26% butadiene.

[0100] Polystyrene 158 (INEOS Styrolution, Frankfurt, standard PS with Vicat B / 50 of 101 °C, containing no white oil).

[0101] 2.5 wt% mineral oil (white oil DAB 10), 0.25 wt% antioxidant 1 ("Sumilizer GM"), and 0.4 wt% antioxidant 2 (tris-nonylphenyl phosphate (TNPP)) were added during melt processing as stabilizers and ingredients, respectively. SBS+PS

[0102] Furthermore, mixtures of the polymer component SBS1 with polystyrene 158 (INEOS Styrolution, Frankfurt, standard PS with Vicat B / 50 of 101 °C, containing no white oil) were prepared.

[0103] These blends were produced by mixing on a ZSK30 twin-screw extruder (Coperion) at a melt temperature of approximately 240 °C: SBS1 + 25% PS means: blend of 75 wt.% Styrolux 3G55 with 25 wt.% Polystyrene 158 (stable morphology: 2-phase blend with lamellar / cylindrical structure); SBS1 + 50% PS means: blend of 50 wt.% Styrolux 3G55 with 50 wt.% Polystyrene 158 (morphology consisting mainly of PS as a homogeneous, continuous phase and polybutadiene-co-styrene as a discontinuous phase, distributed in particles, some lamellae are visible); SBS1 + 75% PS means: blend of 25 wt.% Styrolux 3G55 with 75 wt.% Polystyrene 158 (stable morphology with PS as a homogeneous, continuous phase and polybutadiene-co-styrene as a discontinuous phase, distributed in particles).

[0104] The respective morphology was determined using RuO 4 contrasted ultramicrotome thin-layer sections using a standard scanning electron microscope and a magnification of 100,000 to 1.

[0105] Conducting migration measurements: The use of oil as a grease simulant is less suitable due to analytical and technical difficulties. Ethanol 95% and isooctane are also less reliable as grease simulants due to strong interactions with the polymer matrix. Aqueous simulants are difficult to use due to the very low solubility of the additives.

[0106] For this reason, migration cells were used in which polymer films made of the polymer compositions: "SBS1", "SBS + 25%PS", "SBS + 50%PS" and "SBS+75%PS" each 1 mm thick (Table 3) were clamped between two polyethylene (LDPE) films of 0.5 mm thickness. Zero migration values with polyethylene (LDPE) were determined. After extraction with diethyl ether, the amounts of migrated substances were determined. (according to the times and temperatures given in Table 3a) using FID gas chromatography: Table 3 Device parameters: Column: DB1ht, 30m, ID 0.25mm, film 0.1 µm Carrier gas / flow: Helium; 1.6 ml / min; 35 cm / sec Injector: Split / splitless; 320°C Injection: 1 µm splitless Detector: FID; 320°C Temperature program: 60°C (2 min) 20°C / min 320°C

[0107] The results of the kinetic measurements of migration (at 40-70°C, in µg / dm 2< ) of the ingredients in SBS and SBS+25%PS and the other blends according to the invention (SBS + 50 or + 75% PS) are shown in Table 3a.

[0108] From the migration values, the diffusion coefficients, D p , were determined for the respective polymer matrix and the corresponding migrant, and from these the migration properties were determined using equation (1). <h2 style=";text-align:left;direction:ltr">Table 3a<h2 style=";text-align:left;direction:ltr"> Antioxidant 1 Antioxidant 2 Mineral oil M = 394 M = 689 M = 515 Temp. 40°C 60 °C 70 °C 40 °C 60 °C 70 °C 40 °C 60 °C 70 °C SBS 1* 0,26 0,56 0,76 0,26 1,86 2,47 25,2 74,1 64,0 +25% HP* 0,51 0,29 47,6 +50% HP 0,15 <0,1 9,5 +75% HP <0,01 <0,1 <2 * not according to the invention

[0109] From the migration values, the diffusion coefficients DP were determined for the respective polymer matrix and the corresponding migrants and from these the AP values were calculated using equation 2, see Table 3b. Antioxidant 1 Antioxidant 2 Mineral oil M = 394 M = 689 M = 515 Temp. 40°C 60 ° 70 ° 40°C 60 ° 70 °C 40°C 60 °C 70°C SBS 1* 5,0 5,0 5,1 4,5 5,5 6,0 9,0 10,3 8,9 +25% HP* 3,2 6.2 7.0 +50% HP 0,5 nb 4.5 +75% HP <-2 <0 <2 *not according to the invention nb is not determined

[0110] The mineral oil swells the discontinuous polymeric soft phase and, at the boundary between the inventive discontinuous (particulate) morphology, leads to a partially lamellar morphology, which has negative technical effects. This is evident, for example, in the compositions with 50 wt.% polystyrene and 50 wt.% Styrolux 3G55 as polymer components.

[0111] It was found that during the transition from a (co-continuous) polymer structure to the discontinuous, particulate structure used in the composition (A) according to the invention, both the migration values and the AP polymer-specific parameters decrease significantly. This demonstrates that the barrier effect of the polymer composition is increased, so that the polymer composition (A) with reduced migration of stabilizers (or ingredients) according to the invention provides a significant technical advantage.

[0112] This is used, among other things, for the production of packaging with a composite structure with two different layers, (S1) made of a thermoplastic mixture of 25 wt.% styrene-butadiene-styrene copolymer and 75% PS, and a further layer (S2) made of non-styrene-containing thermoplastic, in particular polyurethane or PET.

Claims

1. Thermoplastic polymer composition (A) with reduced migration of stabilizers (S) and / or further ingredients (I), comprising 50 to 99.9 wt.-%, based on the polymer composition (A), of at least one thermoplastic polymer (P) which has migration barrier properties for stabilizers, and at least 0.1 wt.-%, often 0.1 to 2.0 wt.-%, based on the polymer composition (A), of at least one stabilizer component (S) and / or at least 0.1 wt.-%, often 0.1 to 2.0 wt.-%, based on the polymer composition (A), of at least one further ingredient (I), wherein for the thermoplastic polymer composition (A) applies: a) the glass transition temperature Tg of the thermoplastic polymer (P) is above the service temperature of 50°C, and b) the polymer-specific constant for polymers (AP) of the thermoplastic polymer (P) is less than 1, wherein the polymer-specific constant for polymers (AP) is determined as disclosed in the description, and c) the diffusion coefficient (DP), derived therefrom, of the thermoplastic polymer (P) for mineral oil is less than 10-12 cm2 / s, at 20°C, wherein the diffusion coefficient (DP) is determined as disclosed in the description, and d) the morphology of the thermoplastic polymer (P) is two-phase heterogeneous, where, in the case of two-phase heterogeneous morphology of the thermoplastic polymer (P), the polymer component (Pp) having the higher AP value and the higher diffusion coefficient (DP) present as a discontinuous phase in particle form with a weight-average particle size (D) of 20 nm to 10 µm, is embedded in a polymer component (Pm) of a lower AP value and lower diffusion coefficient (DP), where the morphology of the thermoplastic polymer (P) does not have a co-continuous structure.

2. Thermoplastic polymer composition (A) with reduced migration according to claim 1, characterized in that it comprises as thermoplastic polymer (P) a styrene-containing polymer having a glass transition temperature Tg of at least 60°C, in particular at least 70°C.

3. Thermoplastic polymer composition (A) with reduced migration according to claim 1 or 2, characterized in that it comprises as thermoplastic polymer (P) a styrene-containing polymer component from the group consisting of polystyrene (PS), in particularly HIPS and GPPS, and SBS copolymer / PS blends and SBC copolymer / PS blends.

4. Thermoplastic polymer composition (A) with reduced migration according to at least one of claims 1 to 3, characterized in that it comprises as thermoplastic polymer (P) a polystyrene (PS) and an SBS copolymer.

5. Thermoplastic polymer composition (A) with reduced migration according to at least one of claims 1 to 4, characterized in that the thermoplastic polymer (P) comprises at least 50 wt.-% of polystyrene (PS) and at least 10 wt.-% of SBS copolymer.

6. Thermoplastic polymer composition (A) with reduced migration according to at least one of claims 1 to 5, characterized in that it comprises at least one stabilizer component (S) from the group consisting of antioxidants and light stabilizers, and / or comprises at least one further ingredient (I) from the group consisting of residual monomers and oligomers.

7. Thermoplastic polymer composition (A) with reduced migration according to at least one of claims 1 to 6, characterized in that it contains 0.1 to 2.0 wt.-%, based on the polymer composition (A), of at least one stabilizer component (S), in particular at least one antioxidant.

8. Thermoplastic polymer composition (A) with reduced migration according to at least one of claims 1 to 7, characterized in that it contains 0.1 to 2.0 wt.-%, based on the polymer composition (A), of two different stabilizer components (S), and optionally additionally at least one further ingredient.

9. Composite structure for packaging use, comprising at least two different layers, where at least one layer (S1) consists of a thermoplastic polymer composition (A) with reduced migration according to at least one of claims 1 to 8.

10. Composite structure for packaging use according to claim 9, comprising at least two different layers, wherein at least one layer (S1) consists largely of a thermoplastic polymer composition (A) of polystyrene (PS), SBS copolymer / PS blends and / or SBC copolymer / PS blends, and at least one further layer (S2) consists largely of a non-styrene-containing thermoplastic polymer composition (A2).

11. Process for producing a thermoplastic polymer composition (A) with reduced migration of stabilizers (S) and / or further ingredients (I), according to any of claims 1 to 8, wherein at least one thermoplastic polymer (P) which has migration barrier properties is mixed with at least one stabilizer component (S) and optionally further polymer additives.

12. Use of a thermoplastic polymer composition (A) with reduced migration of stabilizers (S) and / or further ingredients (I) according to any of claims 1 to 8 for the production of films, fibers or moldings.

13. Use of a composite structure according to at least one of claims 9 or 10, comprising at least two different layers, wherein at least one layer (S1) consists of a thermoplastic polymer composition (A) with reduced migration, for providing packaging with enhanced resistance to delamination.

14. Process for producing a composite structure, comprising at least two different layers, where at least one layer (S1) consists of a thermoplastic polymer composition (A) with reduced migration according to at least one of claims 1 to 8, by providing the layer (S1) and at least one further layer (S2) and joining the at least two layers.