WO2013056704A1

WO2013056704A1 - Process for producing nanocomposites from inorganic nanoparticles and polymers

Info

Publication number: WO2013056704A1
Application number: PCT/DE2012/100324
Authority: WO
Inventors: Michel Gschwendtner; Franziska WEICHELT
Original assignee: Minervius Gmbh; Hülsmann, Ralf
Priority date: 2011-10-20
Filing date: 2012-10-19
Publication date: 2013-04-25
Also published as: DE102011054628A1

Abstract

The invention relates to a process for producing nanocomposites from inorganic nanoparticles and polymers, comprising the following method steps: a) irradiation cross-linking of a starting polymer in solid form; b) admixing inorganic nanoparticles to the starting polymer.

Description

Process for the preparation of nanocomposites from inorganic nanoparticles and polymers

DESCRIPTION

The invention relates to a process for the production of nanocomposites from inorganic nanoparticles and polymers.

A nanocomposite here means hybrid materials (combination of at least two heterogeneous components) in which at least one dimension of one of the components lies in the nanoscale range (i.e., less than 100 nm).

The production of such nanocomposites is for example in

WO 2007/024043 A1 and WO 2007/142663 A2.

WO 2007/024043 A1 discloses nanocomposites of surface-modified colloidal metals or metal oxide nanoparticles and a

thermoplastic polymer, which improved mechanical

Properties, compared to the unmodified polymer own. The compatibility between inorganic component and polymer matrix is achieved by the additional surface modification of the nanoparticles. WO 2007/142663 A2 describes a polymer composite material which contains halloysite (silicate mineral) as nanoparticulate filler. By using the nanoparticles novel properties are obtained in the polymer matrix, without the mechanical

Properties of the composite material.

The invention is based on the object, a particularly advantageous method for the production of nanocomposites from inorganic

Nanoparticles and polymers. In particular, the after the nanocomposites produced have improved mechanical, thermal, optical and / or chemical properties compared to conventional nanocomposites.

This object is solved by the features of patent claim 1. Advantageous embodiments are described in the subclaims.

According to the invention, the method for producing nanocomposites from inorganic nanoparticles and polymers has the following

Process steps on: a) Radiation crosslinking of a starting polymer in the solid state and b) admixing of inorganic nanoparticles to the starting polymer.

Radiation crosslinking (hereinafter also referred to as irradiation) is understood here as meaning a generally known process for modifying polymers with the aid of ionizing radiation. Such a radiation crosslinking process is described, for example, in US Pat. No. 7,094,472 B2.

The inventive combination of radiation crosslinking and admixture of inorganic nanoparticles produces a nanocomposite which has particularly good mechanical, thermal, optical and / or chemical properties, since both the beam crosslinking and the addition of inorganic nanoparticles improve the material properties of the starting polymer accordingly.

In general form, the time sequence of method steps a) and b) is not fixed. Thus, first of all, method step a) and then method step b) can be carried out. However, it is also possible first to carry out method step b) and then method step a). In a particularly preferred Embodiment, however, the process step a) before the time

Process step b) executed.

The starting polymer is a polymer matrix of a thermoplastic, an elastomer and / or thermoplastic elastomer

Polymer matrix may be both a homopolymer and a copolymer. Homopolymers are polymers consisting of only one kind of monomer, e.g. Polyethylene, polypropylene, etc. Copolymers are polymers produced by the polymerization of two or more varieties of

Monomers have been prepared, e.g. Ethylene-propylene copolymers, ethylene-butylene copolymers, propylene-butylene copolymers, ethylene-vinyl acetate copolymers, etc. Also, the polymer matrix may be a blend of various thermoplastics, elastomers and / or thermoplastic elastomers, e.g. Polyethylene / polypropylene blends, polyethylene-polystyrene blends, etc. Finally, the polymer matrix may also be a recyclate, i. by recycling processes recovered thermoplastic, elastomer or thermoplastic elastomer, be. The polymer matrix may contain up to 30% by weight of non-polymeric components, e.g. Impurities, additives or metal residues. Particularly preferred are in the

The present invention uses ethylene polymers as the polymer matrix, the term ethylene polymer referring to both ethylene homopolymers and ethylene copolymers. Ethylene homopolymers are here

Ethylene polymers that are substantially, i. consist of at least 97 wt .-% of ethylene. Ethylene copolymers are ethylene polymers derived from the polymerization of ethylene and at least one other

copolymerizable monomer, i. the term also includes terpolymers (polymers made from three different monomers).

The inorganic nanoparticles may be in the form of metal oxides (e.g.

Zinc Oxide (ZnO), Titanium Dioxide (TiO2), Iron (III) Oxide (Fe2O3), Silica (SiO 2), aluminum (III) oxide (Al 2 O 3), tin dioxide (SnO 2), indium (III) oxide (In 2 O 3), magnesium oxide (MgO), zirconia (ZrO 2), ceria (CeO 2), copper (I) oxide (CuO), silver oxide (AgO)), metal hydroxides (eg

Aluminum hydroxide (Al (OH) 3), magnesium hydroxide (Mg (OH) 2)),

Metal carbonates (e.g., magnesium carbonate (MgCO3)), metals (e.g., silver (Ag), gold (Au), nickel (Ni), aluminum (Al)), melamine phosphates, or melamine pyrophosphates, natural or synthetic clays

(Phyllosilicates) or polyhedral oligomeric silsequioxanes (POSS) or carbon-based (e.g., carbon nanotubes, carbon black, fullerenes (spherical carbon-based nanoparticles)). Furthermore, it is possible to mix different types of nanoparticles in the polymer matrix. The nanoparticle form can be nanoscale in three dimensions (spherical), nanoscale in two dimensions (rod-shaped, tubular, fibrous, needle-shaped) or even nanoscale in a dimesion (platelet-shaped). The

Nanoparticles can be present as individual particles, agglomerates or aggregates. As agglomerates loose, reversible particle accumulations are referred to, which can be separated by sufficient shear forces. In contrast, aggregates are irreversible

Deposits of particle particles, where the individual particles can not be separated. The nanoparticles can be introduced into the polymer matrix at from 0.01 to 50% by weight. In order to improve the compatibility between nanoparticles and polymer matrix and to facilitate the dispersibility of the nanoparticles in the polymer matrix, the nanoparticulate components may additionally contain additives

be surface-functionalized. The additives can react with the nanoparticle surface both via physical and chemical bonding.

By using ZnO, for example, both the UV stability and the mechanical properties of the polymer (eg Abrasion resistance and stability). In addition, an antimicrobial effect can be achieved by nanoscale ZnO. The

Use of layered silicates can lead to an improvement in stiffness, a reduction in abrasion and a reduction in the combustibility of the polymer. ΤΊΟ2 has both a UV-protecting and a water and dirt repellent effect. By using Al 2 O 3, the mechanical properties (e.g.

Breaking strength and hardness) and the flammability of the polymer can be reduced. The addition of CNT or carbon black on the one hand improves the conductivity of the polymer and on the other hand achieves a UV-protective effect. In addition, by using CNT, the combustibility of the polymer can be reduced.

Radiation crosslinking takes place at a temperature at which the

Starting polymer in the solid phase (i.e., in the solid state) is present.

In particular, the starting polymer may be in the form of granules, pellets, flakes, spheres or powders. Preferably, the radiation crosslinking under ambient pressure and / or

Ambient atmosphere instead.

The irradiation can be carried out both in the presence and in the absence of oxygen. However, the irradiation preferably takes place

Oxygen atmosphere instead, because by the irradiation in the presence of oxygen, the polymer reacts via a peroxide radical mechanism with the oxygen molecules and so new polar functional groups (eg carboxyl or carbonyl groups) can be generated in the polymer, this process is called oxidation. Radiation-induced oxidation can significantly improve the compatibility of the polymer with other materials (eg, additives) and the adhesion of the polymer to polar species (such as metal surfaces). In a particularly advantageous embodiment, the starting polymer is a semi-crystalline polymer material and the irradiation takes place at a temperature below the crystalline melting temperature of the

Polymer material. In this procedure, the amorphous regions are preferably branched / partially crosslinked, while the crystalline regions remain largely unchanged. In this way, the processability of the

Polymer largely preserved.

Irradiation is by means of ionizing radiation, i. possible

Irradiation types are, in particular, electron radiation, gamma radiation or X-radiation, but preferably electron radiation. The irradiation dose should be between 0.1 and 500 kGy, preferably in the range of 4 to 30 kGy; the choice of the irradiation dose depends on the polymer, the additive content and / or the desired degree of crosslinking.

In another preferred embodiment, the starting polymer is crosslinked to a gel content of 0.01-10%. This preferred

Degree of crosslinking is well below the usual levels

Degree of crosslinking (gel content 60-70%) and allows easy and simple further processing / transformation of the irradiated polymer. At the same time, due to the low degree of crosslinking, the shrinkage behavior of the polymer remains largely unchanged. A reduction in shrinkage can be further enhanced by the addition of nanoscale fillers (e.g.

Calcium carbonate) can be achieved.

If the radiation treatment of the polymers with the above relatively low radiation doses (0.1 to 500 kGy), only the above-mentioned low degree of crosslinking (gel content of 0.01 -10%) is obtained in the polymer, so that the material also after the radiation modification remains processable and recyclable and from this final products can be formed. In contrast, products that are chemically crosslinked or after Forming radiation crosslinked were no longer deformable or recyclable. A reshaping of the irradiated polymer can by a

Extrusion process done. In a particularly advantageous manner, this extrusion process can be carried out simultaneously with the admixing of the inorganic

Nanoparticles take place, i. The inorganic nanoparticles are fed to the extruder and during the extrusion process in the

radiation-crosslinked polymer matrix distributed.

Preferably, the irradiation takes place without the addition of crosslinking additives. However, depending on the type of polymer, crosslinking additives can be added if, for example, it is known that during treatment with ionizing radiation without crosslinking additive, degradation of the polymer over crosslinking dominates, e.g. in polypropylene. The

Crosslinking additive may be solid, liquid or gaseous and contains at least one multiple bond. For solid or liquid

Crosslinking additives are these before irradiation by

Melting / compounding introduced into the polymer. If the crosslinking additive is gaseous, some or all of it may be gaseous

Ambient atmosphere in which the material is irradiated, be replaced by the gaseous crosslinking additive. The gaseous

Crosslinking additive can diffuse directly during the irradiation in the polymer and there lead to crosslinking, an additional

Compounding step is not necessary. It is also possible to apply the solid or liquid crosslinking additives to the nanoparticle surface, ie to modify the nanoparticles with the crosslinking additives. The additives can react with the surface of the nanoparticulate component both by chemical and physical bonding. Embodiments Example 1

25 kg LLDPE granules are irradiated with high-energy electrons from an electron irradiation facility (10 MeV) with a surface dose of 8 kGy in ambient atmosphere and at room temperature.

Subsequently, with the aid of an extruder, 2% by weight of nanoscale ZnO and 0.5% by weight of heat stabilizer are compounded into the modified LLDPE granules and a film is extruded (nanocomposite modified). It is chosen a temperature profile that ensures a melting temperature in the range of 200 to 260 ° C. A comparative film is prepared in the same way using the unmodified LLDPE (nanocomposite un modified). Subsequently, the properties of the slides

(Nanocomposite unmodified and nanocomposite modified) compared. The modified LLDPE film has a lower UV transmission with a higher transparency in the visible range compared to the modified nanocomposite film because the ZnO nanoparticles are better distributed and deagglomerated in the LLDPE matrix by the radiation modification of the polymer. In addition, the modified LLDPE film is more tear-resistant.

Example 2:

25 kg HDPE granules are irradiated with high-energy electrons from an electron irradiation system (10 MeV) with a surface dose of 16 kGy in ambient atmosphere and at room temperature.

Subsequently, by means of an extruder, 3% by weight of phyllosilicate (natural montmorillonite modified with quarternary ammonium salt) and 0.5% by weight of heat stabilizer and 0.5% by weight of light stabilizer are compounded into the modified HDPE granules, into a water bath extruded and then cut into pellets (granulated, nanocomposite modified). It is chosen a temperature profile, which ensures a melting temperature in the range of 210 to 260 ° C. One

Comparative material is prepared in the same way using the unmodified HDPE (nanocomposite unmodified). Subsequently, the properties of the nanocomposites (unmodified and modified) are compared. The modified HDPE nanocomposite has improved mechanical (e.g., higher modulus of elasticity or tensile strength) and thermal properties (higher heat distortion temperature) than the unmodified HDPE nanocomposite.

Example 3:

25 kg of HDPE granules are irradiated in a gamma irradiation system at a dose of 16 kGy. Subsequently, by means of an extruder, 2.5% by weight of nanosize Al 2 O 3 are compounded into the modified HDPE granules, extruded into a water bath and then cut into pellets (granulated, nanocomposite modified). It will be a

Temperature profile selected, which ensures a melting temperature in the range of 210 to 260 ° C. A comparison material is prepared in the same way using the unmodified HDPE (nanocomposite unmodified). Subsequently, the properties of the nanocomposites (unmodified and modified) are compared. The modified HDPE nanocomposite has improved mechanical properties (e.g., improved abrasion resistance) than the unmodified HDPE nanocomposite.

Example 4:

A compound of 0.25% by weight AgO and 0.25% by weight CuO in LDPE is prepared, extruded into a water bath and then cut into pellets (granulated, nanocomposite unmodified). It will be a Temperature profile selected, which ensures a melting temperature in the range of 210 to 260 ° C. 25 kg of the granules are with

high-energy electrons from an electron irradiation system (10 MeV) with a surface dose of 8 kGy in ambient atmosphere and irradiated at room temperature (nanocomposite modified). Of the

Modified LDPE nanocomposite has better antimicrobial activity than unmodified LDPE nanocomposite.

The invention is further illustrated by the drawing figures. It show, each schematically:

1 shows a microstructure of a polymer before irradiation;

Fig. 2 shows the microstructure of the polymer after irradiation; and

3 shows the microstructure of the polymer after irradiation and with homogeneously distributed spherical nanoparticles.

Fig. 1 shows schematically a structure of a polymer. The structure consists of macromolecular molecular chains 1, of which only one has been provided with a reference numeral. Fig. 2 shows the microstructure of Fig. 1 after irradiation. Compared to the structure of Fig. 1, the molecular chains 1 were partially broken. At the same time have themselves

Connecting points 2, of which only one has been provided with a reference numeral, formed between the individual molecular chains 1. There was a networking. 3 shows the networked structure of FIG. 2 with homogeneously distributed spherical nanoparticles 3, of which only one has been provided with a reference numeral. The nanoparticles 3 are arranged between the molecular chains and distributed substantially homogeneously within the structure.

Claims

1 . Process for the preparation of nanocomposites from inorganic nanoparticles and polymers with the following process steps:

a) Radiation crosslinking of a starting polymer in the solid state; b) admixing inorganic nanoparticles for

Starting polymer.

2. The method of claim 1, wherein the method step a) is carried out prior to the process step b).

3. The method according to any one of the preceding claims, wherein in a time after the process step a) carried out further

Process step, reshaping the radiation crosslinked

Starting polymer takes place.

4. The method according to any one of the preceding claims, wherein the

Process step b) during an extrusion of the

Starting polymer takes place.

5. The method according to any one of the preceding claims, wherein the

Starting polymer is a partially crystalline polymer material and the radiation crosslinking is carried out at a temperature which is below the crystalline melting temperature of the polymer material.

6. The method according to any one of the preceding claims, wherein the

Radiation crosslinking takes place until the starting polymer has a gel content of 0.01 -10%.

7. The method according to any one of the preceding claims, wherein the radiation crosslinking takes place with an irradiation dose of 0.1-500 kGy.

8. The method according to any one of the preceding claims, wherein the starting polymer before the process step a) is present as granules, flakes or powder.

A process according to any one of the preceding claims, wherein the starting polymer is an ethylene polymer.

10. The method according to any one of the preceding claims, wherein the method step a) at room temperature and under

Ambient atmosphere is performed.