WO2009027536A1

WO2009027536A1 - Plastic profile with a photocatalytically active surface

Info

Publication number: WO2009027536A1
Application number: PCT/EP2008/061472
Authority: WO
Inventors: Frank Suthoff; Rudolf Heitzmann; Bernd Rung
Original assignee: Profine Gmbh
Priority date: 2007-08-31
Filing date: 2008-09-01
Publication date: 2009-03-05
Also published as: DE102008041740A1

Abstract

In order to improve the properties of so-called self-cleaning plastic profiles, in particular window profiles, it is proposed to connect an extruded basic body based on PVC-U to a top layer which is based on an organic thermoplastic polymer and is directly or indirectly connected to the basic body, wherein a photocatalytically active metal oxide, in particular TiO2, is homogeneously distributed in the organic polymer. The top layer consists, in particular, of PMMA having a layer thickness of 0.1 to 3 mm.

Description

description

Plastic profile with photocatalytically active surface

The present invention relates to a plastic profile with a photocatalytically active surface, comprising an extruded base body based on PVC-U and a covering layer directly or indirectly bonded to the base body based on an organic polymer. In particular, the invention relates to PVC-U hollow wall profiles used in the manufacture of windows and doors.

Technical area

Windows and doors are made to a large extent of extruded plastic profiles, in particular of rigid PVC (PVC-U). For this purpose, profile sections cut in the miter area are welded together for the frame and wing mitred sections.

Surface coatings with a self-cleaning or "easy-to-clean" effect are known in particular for glazing (eg EP 0 850 203 B1). As a rule, they are based on the use of nanoscale TiO 2 particles with photocatalytic and hydrophilic properties. In recent years, however, efforts are being made to equip the frame material self-cleaning.

The photocatalytic properties of TiC ^ particles have long been known and studied extensively in the literature. The photocatalytic effect is based on a semiconductor property of the TiC> 2, wherein a hole-electron pair is formed by a quantum of light, which has a relatively long recombination time. By diffusion of holes and electrons to the surface processes are set in motion, which develop directly or indirectly via water with subsequent hydrogen peroxide formation a strong oxidative effect. The oxidation potential of more than 3 eV is so high that practically all organic substances that come into contact with such TiO 2 particles are oxidized. For photocatalytic applications, TiO 2 is predominantly used in the Anatase configuration and primary particle sizes in the nanoscale range, ie with primary particle sizes below 100 nm used.

However, it has been found that it is difficult to on substrates or surface layers that are themselves oxidizable, such. As in substrates or layers of organic polymers, oxidation by a photocatalytic layer applied thereto and thus to prevent damage to the substrate or the layer.

TiO 2 is widely used for the pigmentation of PVC-U. The TiO 2 pigments have almost exclusively the rutile crystallite form of the TiO 2. Although rutile has a lower photocatalytic activity compared to the anatase configuration, TiCi pigments for PVC must firstly be optimized with regard to their particle diameter-usually the average diameter is about 0.3 to 0.4 μm-and secondly For example, TiCi pigments are usually rendered inert by a thin coating of Al 2 O 3 and SiO 2 compounds or other metal oxides in order to avoid undesirable degradation of the PVC polymer by photocatalytic effects.

State of the art

DE 102 248 95 A1 discloses a self-cleaning plastic body with a plastic substrate which initially has a siloxane coating and an inorganic bonded photocatalytically active layer with TiO 2 particles. The plastic substrate can also consist of PMMA (polymethyl methacrylate).

Although the inorganic coatings applied in this way have a relatively high scratch resistance, on the one hand the application of the two inorganic layers is complicated, on the other hand their durability is limited.

The 103 04 953 Al concerns scratch-resistant and self-cleaning plastic body, which are obtainable by one on one Plastic substrate applied and cured a siloxane coating, the polar portion of the surface energy of the cured siloxane coating to a value of at least 10 mN / m increases and then applying a photocatalytic active TiC ^ particle-containing coating and cured.

WO 2005/007286 A1 and EP 1 498 176 A1 disclose a generic PVC substrate which can also be used, for example, for window profiles with a photocatalytically active coating consisting of at least two wet-chemically produced inorganic layers with at least one first substrate applied to the substrate an underlayer comprising inorganic polymer and at least one second second top layer consisting of TiO 2 particles, wherein the underlayer contains less than 0.5% by weight of TiO 2 particles, is free of pores and has at least 5% by weight of ZrO 2. A layer of PMMA may also be arranged between the PVC layer and the inorganic polymer layers.

The photocatalytically active coating of these PVC substrates with a self-cleaning or "easy-to-clean" effect, however, has a lower efficiency and only a limited shelf life compared with correspondingly coated glazings. In addition, the application of the coating is very expensive. An additional, as yet unsolved problem exists in the welding of the window profiles in the miter area, since the inorganic coating is destroyed during welding in the corner. As a result, dirt can accumulate especially in the corner of the window frame.

It is an object of the present invention to provide a plastic profile based on PVC-U with a photocatalytically active surface with a self-cleaning or "easy-to-clean" effect, which has high efficacy with good long-term stability. Presentation of the invention

The invention solves this problem by a plastic profile with an extruded base body based on PVC-U, wherein the extruded base body has a directly or indirectly connected to the base layer cover layer based on an organic polymer in which a photocatalytically active metal oxide is present homogeneously distributed , The organic polymer of the cover layer is preferably a thermoplastic.

The present invention thus turns away from the hitherto fundamentally adopted method of using photocatalytically active TiO 2 in inorganic, very thin coatings and separating them with an additional inorganic intermediate layer from the organic polymer of the substrate. The invention takes into account the fact that the organic polymer of the top layer is slowly degraded at the surface.

The thickness of the cover layer based on the organic polymer is preferably 0.1 to 3 mm, in particular 0.15 to 0.6 mm. It is thus relatively thick in comparison to heretofore used inorganic coatings, so that the durability of the coatings according to the invention is sufficient for practical use even under high UV irradiation and usual atmospheric influences.

The photocatalytically active metal oxide can not be incorporated directly into PVC, since this is immediately degraded and darkened. It is preferred for the organic polymer of the cover layer, a halogen-free polymer used.

It has surprisingly been found that, in particular, PMMA is outstandingly suitable for the homogeneous incorporation of photocatalytically active TiC.sub.2 nanoparticles. It is therefore preferred that the organic polymer of the cover layer consists at least predominantly of PMMA. PMMA (polymethyl methacrylate) is an amorphous (noncrystalline) polymer prepared by polymerization of methyl methacrylate. ester. To achieve special properties such as higher hardness, impact resistance, etc., the methyl methacrylate before the polymerization other acrylates, eg. For example, butyl acrylate, are added, in which case the corresponding copolymers of methyl methacrylate arise. Insofar as the term PMMA is used in this application, this includes in addition to polymethyl methacrylate also the corresponding copolymers of methyl methacrylate or mixtures of polymethyl methacrylate with these copolymers.

Suitable photocatalytically active metal oxides are the metal oxides known from the prior art, in particular TiO 2 in the anatase configuration. The primary particles of these TiO 2 TiO 2 nanoparticles in particular have average dimensions <50 nm, but can also be used as agglomerates of such small primary particles. In principle, all photocatalytically active metal oxides or mixtures thereof can be used. The preferred TiC 2 nanoparticles are available commercially as Kronos uvlp 7500 and vlp 7000 from Kronos International, Inc., for example. The vlp 7000 type is photocatalytically active even when exposed to visible light.

It has been found in tests that the respective surface of the PMMA cover layer of the plastic profiles according to the invention is slowly degraded, while in deeper layers of the PMMA cover layer degradation is not measurable. The degradation at the surface takes place the faster, the higher the concentration of photocatalytically active metal oxide in the PMMA cover layer. Therefore, as small as possible but still sufficiently effective amounts of photocatalytically active metal oxide are used in the PMMA cover layer.

The photocatalytically active metal oxides are preferably used in amounts of from 0.05 to 10% by weight, in particular from 0.1 to 5% by weight, particularly preferably up to 1.5% by weight, based in each case on the polymer content of the top layer. The coextruded PMMA cover layer preferably has an average thickness of 0.1 to 3 mm, in particular 0.15 to 0.6 mm, in which the photocatalytically active metal oxide is homogeneously distributed.

Since the surface degradation of the PMMA layer is accelerated with increasing concentration of photocatalytically active metal oxide in the PMMA cover layer, the thickness of this cover layer should be rather higher at higher concentrations of photocatalytically active metal oxide in the cover layer, while at lower concentrations of photocatalytically active Metal oxide in the cover layer, the thickness of this cover layer can be selected thinner. The ratio of the concentration of photocatalytically active metal oxide in the cover layer to the thickness of this cover layer is preferably less than 4% / mm, preferably ≦ 2% / mm, particularly preferably ≦ 1% / mm.

The cover layer according to the invention can in principle - if no pigments are used - be transparent or translucent, since the nanoparticles used due to their small dimensions, the incident visible light little or no break or reflect. However, the cover layer according to the invention is preferably provided with additional color pigments and / or UV absorbers. Preferably, the topcoat contains 1 to 6 wt .-% of color pigments, with inorganic color pigments are preferred because organic color pigments are degraded, if necessary, of the photocatalytically active metal oxides.

The organic top layer particularly preferably contains TiO 2 as non-photocatalytically active UV absorber or white pigment as rutile in an inertized form having an average primary particle size> 0.1 μm, in particular with an average primary particle size of 0.2 to 0.4 μm. Examples of suitable TiO 2 pigments are the commercial products Kroonos 2220 and Kronos 2222 from Kronos International, Inc.

The preferred use of pigments or UV absorbers in the polymeric topcoat prevents larger amounts of UV Radiation penetrate into deeper layers of the cover layer, where they stimulate the photocatalytically active metal oxides and thereby accelerate degradation of the polymer.

The production of the profiles according to the invention is preferably carried out by a coextrusion method which is fundamentally known to the person skilled in the art, in which the PVC batch, usually in the form of a dry blend, is melted with a main extruder and fed to an extrusion tool. Parallel to this, a PMMA granulate is melted in a second extruder and passed through separate distribution channels in certain areas of the same tool. Immediately following the extrusion of the profile takes place in hollow chamber profiles familiar to the expert calibration. With regard to the coextrusion of PMMA and PVC, reference is made to DE 22 46 497 B2, to which reference is hereby incorporated by reference.

The PMMA granules used for extrusion preferably already contains the fraction according to the invention of photocatalytically active metal oxide and pigments. The preparation of these PMMA granules can be carried out, for example, in commercially available co-running twin-screw extruders (compounding extruders). Before the granulating unit, various additives are added to the PMMA. The additives can be added to the PMMA in the compounder extruder as powder, as agglomerate or granules or in liquid form, whereby gravimetric metering systems are often used because of the required accuracy.

However, it is also possible to homogeneously mix PMMA powder or meal with the desired additives and then to granulate the mixture. This is particularly advantageous if the additive has a lack of flowability, which is the case with many powdery materials, especially mineral aggregates such as titanium dioxide, chalk, etc.

The surface of the plastic profiles according to the invention is in common use of both a UV irradiation - in particular by sunlight - and the influence of moisture - especially by rain - suspended. Both factors are important for the "self-cleaning" and hydrophilizing character of the surface.

However, the coextruded profiles initially still have a low self-cleaning effect of the surface. It has surprisingly been found that by machining the surface, in particular by grinding, the self-cleaning and hydrophilizing action of the photocatalytically active metal oxides can be considerably increased. It is assumed that the photocatalytically active metal oxides are initially enveloped on the surface of PMMA polymer and thus virtually inerted. By grinding the photocatalytically active metal oxides are apparently exposed in sufficient quantities.

The catalytic activity can be demonstrated by bringing an aqueous solution of methylene blue into contact with the surface to be measured, exposing the solution in contact with the surface to be measured to UV light, and measuring the decrease in color of the solution over time becomes.

According to a preferred embodiment of the invention, the cover layer is activated after the profile extrusion or after the surface layer has been sanded by UV exposure. Here, if necessary, a slight discoloration of the top layer can be observed, which occurs only in the first intensive UV exposure.

Preferred field of application of the present invention is the extrusion of self-cleaning profiles for the production of windows and doors, in particular in the form of hollow chamber profiles. The cover layer according to the invention based on an organic polymer, in particular of PMMA, preferably covers only partial areas of the profile surface, in particular the outside of the profiles exposed to the weather. It has turned out to be a particular advantage that such coextruded window or door profiles are readily mitred and welded together in the miter area can also be in the miter area, the PMMA cover layer is almost seamless and thus the self-cleaning effect is present in the miter area.

BRIEF DESCRIPTION OF THE DRAWING The invention is explained in more detail below on the basis of an exemplary embodiment and the drawing. 1 shows a cross section through an inventive window profile (frame and casement).

Best way to carry out the invention

In Fig. 1, an inventive frame profile 1 and a corresponding sash profile 2 are shown in cross section. Seen from the contours, these are commercially available plastic profiles for the production of windows, as sold under the trade name Trocal, System Innonova M5, by the applicant. The profiles are produced in a manner known per se in the art by coextrusion with a white-colored PMMA layer.

The approach for the basic profile based on PVC-U contains in addition to the thermoplastic polymer PVC still conventional amounts of chalk, inertized TiO 2 as white pigment, type Kronos 2220, and a lead-free stabilization based on calcium-zinc.

The PMMA coatings 5, 6 coextruded with the PVC base profiles 3, 4 each have a thickness of 0.5 mm and were produced from the following formulation:

Table 1:

This approach for the PMMA coatings 5, 6 was first mixed in a concurrent twin-screw compounding extruder at a temperature of 240 ⁰ C, homogenized and processed into granules. The granules have a white color.

Following the extrusion with subsequent calibration and cooling of the surface known per se to about 30 ^° C., the PMMA surface is sanded by means of abrasive brushes.

After a single activation of the photocatalytically active TiO 2 particles in the surface of the PMMA layer with UV irradiation (100 h with a VITALUX lamp), the surfaces of the PMMA layers 5, 6 have a markedly hydrophilic surface photocatalytic activity can be estimated over the lightening of an aqueous solution of methylene blue over time under UV irradiation.This results in an even higher photocatalytic effect of the PMMA-coated invention compared to commercially available photocatalytically coated glazings (type active glass, Pilkington) profiles.

Legend

1 frame profile

2 sash profile

3 basic profile 4 basic profile

5 PMMA coating

6 PMMA coating

Claims

claims

1. plastic profile with a photocatalytically active surface comprising an extruded base body based on PVC-U and a directly or indirectly connected to the base layer cover layer based on an organic polymer, characterized in that homogeneously distributed in the organic polymer, a photocatalytically active metal oxide is present.

2. Plastic profile according to claim 1, characterized in that the organic polymer of the cover layer is a halogen-free thermoplastic material.

3. Plastic profile according to claim 2, characterized in that the organic polymer of the cover layer consists at least predominantly of PMMA.

4. Plastic profile according to one of claims 1 to 3, characterized in that the photocatalytically active metal oxide consists at least largely nanoscale Tiθ2, in particular in the anatase configuration.

5. Plastic profile according to one of claims 1 to 4, characterized in that the photocatalytically active metal oxide in an amount of 0.05 to 10 wt .-%, in particular 0.1 to 5 wt .-%, in the organic polymer of the cover layer is present.

6. Plastic profile according to claim 5, characterized in that the photocatalytically active metal oxide is present in an amount of 0.1 to 1.5 wt .-% in the organic polymer of the cover layer.

7. Plastic profile according to one of claims 1 to 6, characterized in that the cover layer is transparent or translucent.

8. Plastic profile according to one of claims 1 to 6, characterized in that the cover layer contains a non-photocatalytic lytic UV absorber.

9. Plastic profile according to one of claims 1 to 8, characterized in that the cover layer contains 1 to 6 wt .-% of inorganic pigments, in particular TiO 2.

10. Plastic profile according to claim 8 or 9, characterized in that the non-photocatalytically active UV absorber contains inerted TiO 2 having a mean particle size> 0.1 microns.

11. Plastic profile according to one of claims 1 to 10, characterized in that the cover layer has been connected to the base profile by coextrusion.

12. Plastic profile according to one of claims 1 to 11, characterized in that the cover layer has an average thickness of 0.1 to 3 mm, in particular 0.15 to 0.6 mm.

13. Plastic profile according to claim 12, characterized in that the ratio of the weight concentration of the photocatalytically active metal oxide in the cover layer to the thickness of the cover layer is less than 4% / iπm, preferably ≤ 2% / mm and in particular ≤ 1% / mm.

14. Plastic profile according to one of claims 1 to 12, characterized in that the cover layer has been treated by machining, in particular by grinding.

15. Plastic profile according to one of claims 1 to 14, characterized in that the cover layer has been activated by UV exposure.

16. Plastic profile according to one of claims 1 to 15, characterized in that the plastic profile has hollow chambers up.

17. Use of a plastic profile according to claim 16 for the production of windows and doors.

18. A process for producing a plastic profile with a photocatalytically active surface according to any one of claims 1 to 16, characterized by the following features:

• Melting and homogenizing of a first approach based on PVC-U;

Mixing and homogenizing a second formulation based on a halogen-free organic thermoplastic polymer, this formulation containing between 0.05 and 5% by weight of a photocatalytically active metal oxide,

• Coextrusion of the PVC-U-based approach with the second approach based on a halogen-free organic thermoplastic polymer to form a plastic profile with a photocatalytically active surface.

19. The method according to claim 18, characterized in that the surface is calibrated on the basis of the halogen-free organic thermoplastic polymer after coextrusion and subsequently treated by machining.