DE102004061268A1 - Surface activation of plastic component involves treatment of component surface with gas containing ozone - Google Patents

Abstract

An ozone-containing gas is produced and at least some areas of the component are subjected to the gas mixture to activate the surface for further processing stages. Ozone concentration in the process gas is not less than10ppm, preferably not less than25ppm. The ozone is produced from oxygen or oxygen-containing gas in an ozonizer by static electrical discharge or by UV(ultra-violet) radiation. The process gas may be fed into a gap (26) of constant depth between the surface (24) of the plastic component (22) and a boundary face. A hood may be placed over the component and the gap is formed between the component and the hood, whose contour follows that of the component and at a constant distance from it. Treatment may alternatively occur during the component molding stage in which one tool half (14) is partly opened and the process gas fed (18) into the gap (26). Process gas may also be directed onto the component surface via a nozzle (38) which is manually or automatically guided over the component surface. Components may also be treated by introducing them, via a sluice, into a chamber permanently filled with ozone-containing gas. An independent claim is included for a plastic component, in particular a vehicle component, manufactured by the claimed process.

Description

The The invention relates to a method for activating a plastic surface of a Plastic molding and a molded part thus produced.

Engineering plastics often consist of nonpolar polymers, which due to their low surface energy leads to poor wettability and thus low adhesion of paints, adhesives or other plastic layers, which are to be applied to the plastic surface. In order to improve the adhesion properties of such plastic surfaces, various activation methods are known. In addition to purely physical roughening methods, such as grinding or sandblasting, these include chemical modifications of the plastic surface with polar functional groups (in particular fluorination, eg. DE 35 32 086 A ) also techniques such as flame treatment, UV irradiation, corona treatment and low-pressure plasma.

The flame treatment (eg DE 35 22 315 A ) is the most common pretreatment method. In this case, at a distance of a few centimeters, a gas flame, in particular a propane, butane or natural gas flame with oxygen excess, passed over the plastic surface.

Increasing the adhesion of non-polar plastics with UV irradiation is usually carried out in a vacuum. Out EP 0 833 859 B It is known to perform the UV irradiation in the presence of oxygen to produce a variety of activated oxygen species which is responsible for the observed activation.

at The corona treatment are generated by a high frequency generator High voltage discharges (10-60 kHz, 10-20 kV) Transfer electrodes to the plastic surface. The few millimeters to the surface spaced electrodes are thereby moved slowly over the surface. In this process carried out in air under atmospheric pressure are high-energy Generates ions and radicals that bombard the plastic surface. Due to the electrode system, the corona treatment is only for flat substrates, suitable for films.

When activated in low-pressure plasma (eg DE 102 56 483 A ) are the plastic moldings in batch operation in batches at low pressure in the range of 0.1 to 10 mbar with a suitable process gas (oxygen, nitrogen, fluorine, noble gases) acted upon by a high frequency voltage in the Hz to GHz range. In the process, atoms are knocked out of the plastic surface and the surface is activated by the formation of highly charged accelerated anions, electrons and atoms of the plasma gas. Above all, the process is characterized by a long service life of 100 hours and short process cycles in the minute range. On the other hand, the high investment costs and the compulsory discontinuous operation of the process of disadvantage and a certain associated with the treatment heating of the plastic parts.

Lots the aforementioned activation methods (flame treatment, UV irradiation, Corona treatment) have the disadvantage of complex three-dimensional structures not accessible due to shadow effects. The flame and Corona treatment require activation due to the relatively low durability a quick subsequent Further processing of the surface-treated Plastic part and have a low intensity of activation on. The problem with the treatment in low pressure plasma are high investment and operating costs. Most of the chemical surface modifications are more harmful to the environment with the disadvantage By-products and waste products loaded.

DE 100 24 172 A1 describes the generation of a non-polar substance diffusion barrier by treating the surface of the plastic parts with ozone. The method is particularly applied to fuel tanks to inhibit the diffusion of fuel through the plastic wall.

Of the Invention is based on the object, a method for activation of plastic surfaces to disposal to provide an intense and long-lasting activation preferably low investment and process costs and ideally also the treatment of complex surfaces allowed. That by the Process treated plastic part should be particularly suitable, to be permanently connected with other materials.

This object is achieved by a method having the features of claim 1. According to the invention, it is provided to produce an ozone-containing process gas and at least partially pressurize the plastic surface to be activated with the ozone-containing process gas. The invention takes advantage of the fact that ozone is easy and inexpensive to produce and is able, even in low concentrations a strong polarization and thus increase the free specifi surface energy of the plastic surface. It is believed that exposure to the highly reactive ozone results in the generation of hydroxyl group on the plastic surface. The activation by ozone is also very durable, so that a subsequent further processing of the plastic part, in particular a painting, gluing, flocking, lamination, metallization, labeling, foaming, spraying or the like of the activated plastic surface does not have to take place immediately after the treatment. Rather, a surface-activated plastic part according to the invention can be stored over many days or even weeks. Since the ozone-containing gas is spontaneously distributed in every direction in space, even complex-shaped surface structures can be activated without undesirable shading effects being observed. The distribution can be accelerated by suitable air control measures.

Especially Preferably, an ozone-containing process gas is generated which has an ozone concentration of at least 10 ppm, in particular at least 25 ppm or more. For practical implementations ozone concentrations above 85 ppm were also used. These concentrations guarantee extremely intense activation and allow a reduction in process times to a few minutes or seconds.

The Loading the plastic surface with an externally generated Gas flow also has the advantage that this arbitrary and targeted to lead leaves. It is provided in particular that the ozone-containing process gas in a gap between the plastic surface to be activated and a boundary (tool wall or the like) runs, is guided. As particularly advantageous in terms of a uniform activation effect in particular has a largely constant layer thickness (Equidistant) extending to the plastic surface Gap proved. This gap is preferably relatively narrow in the mm or cm range, so that only small amounts of ozone are needed for filling or a suitable process pressure can be built up quickly can.

The Generation of the ozone may consist of an oxygen-containing gas, in particular Air, or pure oxygen in a conventional ozone generator, consisting of an ozonizer, in which between two electrodes a silent electric discharge is maintained. Also is basically known, ozone by UV radiation from oxygen or oxygen-containing To produce gas (air). The disposal of the environmentally harmful Ozone can easily be trapped in a downstream ozone trap, especially an activated carbon filter, in which the ozone absorbs becomes and decays.

The Ozone can be realized in different ways. According to one first execution becomes a hood, preferably (but not necessary) one the outer contour the plastic part substantially equidistantly replicating hood over the Plastic part set and the ozone-containing process gas in the gap between the plastic surface and the hood headed.

To an alternative embodiment the ozone is applied following the production of the Plastic part in a mold, for example, an injection molding, thermoforming, press or dip edge tool or the like. After shaping the plastic part becomes a mold half of the mold partially return and in the thus generated sealed cavity, the ozone-containing process gas directed.

In Another preferred embodiment of the invention is the Ozone application by manual or automatic guidance of a Nozzle, off which flows the ozone-containing process gas, over the plastic surface to be activated, wherein also Here preferably a substantially uniform distance between the nozzle and the plastic surface is maintained becomes.

Also can ozone in a permanent with the ozone-containing Process gas filled Chamber done with the plastic part through locks in the Chamber spent and removed after treatment from this.

The Invention further relates to a plastic part produced by the method, in particular a for a vehicle interior or exterior.

Further preferred embodiments of the invention will become apparent from the others, in the subclaims mentioned features.

The Invention will be described below in embodiments with reference to FIG associated Drawings explained. Show it:

1a to 1c Process stages of ozone loading of a plastic part in a mold;

2 Ozonbeaufschlagung a plastic part under a contour hood and

3 Ozone loading of a plastic part with an air nozzle.

The 1a to 1c show as a sectional representation of manufacturing stages in the surface activity tion of a plastic part with ozone according to a first embodiment of the invention. According to 1a First, the production of the plastic part in a total with 10 designated mold, which is an injection mold in the example shown. The tool 10 consists essentially of two mold halves 12 . 14 which, in the assembled state, form a cavity 16 form, which images an outer contour of the plastic part to be produced. The tool half 14 has an injection port 18 on, through which a plastic melt 20 a thermoplastic polymer, for example with an extruder, in the mold space 16 is injected. After complete filling of the mold cavity 16 you leave the plastic part 22 solidify ( 1b ) and drives the tool half 14 so far back that on the side of a plastic surface to be activated 24 the plastic part 22 a cavity 26 arises, which is largely equidistant to the plastic surface 24 runs. Then it is over the injection opening 18 an ozone-containing process gas into the cavity 26 directed, where there is the plastic surface for a given duration and at a given temperature 24 applied.

In a modification to the example shown, the tool can also have several injection openings 18 over which first the melt 20 and later the ozone-containing gas is supplied. According to another modification, the ozone does not pass through the injection port 18 , but supplied via not shown pressure equalization openings or pressure openings. The latter serve as a rule, the demolding of the plastic part produced 22 after his petrification.

Unlike in the example according to 1a to 1c Depending on the manufacturing method, it may be with the tool 10 also to other types of tools, such as thermoforming, pressing or dipping edge tools or the like act. In any case, the illustrated principle (retraction of a mold half and introduction of ozone into the cavity) remains relevant. Advantage of this principle is that the relevant devices are already present due to the normal process flow and the method is thus particularly cost-effectively feasible. Advantageously added to the usually existing Temperierbarkeit the tools.

2 shows a further embodiment of the method according to the invention. Here is the plastic part 22 on a surface 28 which is for example a conveyor belt. To carry out the process is on the plastic part 22 first a contour hood 30 placed, the outer contour of the plastic surface to be activated 24 corresponds, but is designed so that a substantially equidistant running gap 32 between the plastic surface 24 and the contour hood 30 consists. A around the entire circumference of the hood 30 extending sealing ring 34 , which consists for example of an elastomer, serves on the one hand the correct positioning of the hood 30 on the plastic part 22 and on the other hand the sealing of the hood 30 on the ground 28 , Through an inlet opening 36 the contour hood 30 then an ozone-containing process gas is supplied and the application of the plastic surface 24 for a predetermined duration and at a predetermined temperature.

A third advantageous embodiment of the invention is in 3 shown. Here is the plastic part 22 also on a base 28 , In particular, a substantially continuously conveyed conveyor belt. A nozzle 38 from which flows an ozone-containing process gas, in particular a Langschlitzdüse, is above the conveyor belt 28 arranged and can be moved vertically, for example via a robot. This is done in a way that the distance 40 between the plastic surface 24 and the nozzle 38 always remains substantially constant to achieve uniform surface activation. Alternatively, the nozzle 38 also be guided manually.

In modification to the in 3 illustrated embodiment, the plastic part 22 also on a stationary surface 28 located and the nozzle 38 - Ideally equidistant - over the plastic surface 24 to be moved.

In all embodiments according to the 1 to 3 the production of the ozone-containing process gas is preferably carried out from normal air. This can be done in particular either by means of an ozonizer, which maintains a silent electrical discharge between two electrodes, or by means of UV radiation.

The subsequent Destruction of the ozone can be done in an ozone trap, for example, the Ozone binds to activated carbon, where it decomposes within a short time.

10

mold

12

tool half

14

tool half

16

cavity

18

Injection port

20

Plastic melt

22

Plastic part

24

Plastic surface

26

cavity

28

Substrate / conveyor belt

30

contour hood

32

gap

34

seal

36

inlet port

38

jet

40

distance

Claims (11)

Method for activating a plastic surface ( 24 ) of a plastic part ( 22 ), wherein an ozone-containing process gas is generated and the plastic surface ( 24 ) is at least partially applied to the ozone-containing gas mixture. Method according to claim 1, characterized in that that the ozone-containing process gas has an ozone concentration of at least 10 ppm, in particular of at least 25 ppm. Method according to claim 1 or 2, characterized that the ozone is made of oxygen or an oxygen-containing gas in an ozonizer by silent electric discharge or by UV radiation is produced. Method according to one of the preceding claims, characterized in that the ozone-containing process gas in a gap ( 26 . 32 . 40 ) between the plastic surface ( 24 ) and a boundary, the gap ( 26 . 32 . 40 ) in particular with a substantially constant layer thickness to the plastic surface ( 24 ) runs. Method according to one of claims 1 to 4, characterized in that the ozone is applied by a hood ( 30 ), in particular a the outer contour of the plastic part ( 22 ) substantially equidistantly simulating hood, over the plastic part ( 22 ) and the ozone-containing process gas into the gap ( 32 ) between the plastic surface ( 24 ) and the hood ( 30 ). Method according to one of claims 1 to 5, characterized in that the ozone impingement following the production of the plastic part in a mold ( 10 ), wherein a tool half ( 14 ) of the molding tool ( 10 ) is partially returned and into the cavity ( 26 ) the ozone-containing process gas is passed. Method according to one of claims 1 to 5, characterized in that the ozone loading by manual or automatic guidance of a nozzle ( 38 ), from which the ozone-containing process gas flows, over the plastic surface ( 24 ) he follows. Method according to one of claims 1 to 5, characterized in that the ozone is applied in a permanently filled with the ozone-containing process gas chamber, wherein the plastic part ( 22 ) is brought through locks in the chamber and removed from it. Method according to one of the preceding claims, characterized in that during the ozone loading of the plastic surface ( 24 ) Temperierung takes place. Method according to one of the preceding claims, characterized in that following the ozone loading a painting, gluing, flocking, lamination, metallization, labeling, foaming or spraying of the activated plastic surface ( 24 ) he follows. Plastic part, especially for a motor vehicle manufactured with a method according to one of claims 1 to 10.