DE3840130C1 - Method of adhesively bonding parts to be joined of rubber or plastic - Google Patents

Abstract

A description is given of a method of adhesively bonding parts to be joined of rubber or plastic, in particular for shoe soles, in which a laser beam (100) is passed over the parts to be joined (1) and in which the removal of the adhesion-inhibiting outer boundary layer, adhering to the parts to be joined (1), is effected by the thermal energy applied by the laser beam (100), and in which the adhesion between the part to be joined (1) and an adhesive applied to the part to be joined (1) is increased by chemical reactions induced by the laser beam (100) in the reaction layer and the inner boundary layer of the part to be joined (1). <IMAGE>

Description

The invention relates to a method for gluing Joining parts made of rubber or plastic, especially for Shoe soles.

To increase the holding force of the adhesive connection between the Insole and the lasting fold attached to it on the one hand and the outsole on the other known mechanical-abrasive processes with which the Sole surfaces are roughened. This creates one Surface enlargement, which to increase the number of Binding points leads (specific adhesion) and the adhesive in the adhesive surface offers anchoring options (mechanical Adhesion), which increases the strength of the adhesive joint is achieved. The shoe soles are roughened by hand or carried out with napping machines. Such roughing machines for Treatment of the lasting fold, the sole surfaces and the Inner shaft use rotating tools like rough heads, Roughing, brushing and the like. The known mechanical  Processes have the disadvantage that they are automated Processing of the adhesive surfaces only with very simple ones Workpiece geometries is possible. The massive mechanical The action of the roughing tools also requires a rapid Wear and tear of the same, resulting in a constant, reproducible quality standard of the machining results can only be achieved with great effort. Furthermore, the by the mechanical removal process of some layers of the Particle surface caused emission of dust particles the need for post-treatment of the workpieces.

The invention has for its object to a method develop which is automated with little effort Adhesive pretreatment of a wide variety of shoe soles Geometry enables and a constant Quality standard of the processing results guaranteed.

The object is achieved in that before the application of the Adhesive guided a laser beam over the parts to be joined is that the removal of the adhering to the parts to be joined anti-adhesive layers by the laser beam applied thermal energy is effected, and that the Adhesion between the parts to be joined and that on the parts to be joined adhesive to be applied by induced by the laser beam chemical reactions in the reaction layer and the inner layer Boundary layer of the parts to be joined is increased.  

Advantageous developments of the invention are in the Subclaims defined.

The invention has the advantage that in the same step surface cleaning and surface activation is carried out. The action of the laser causes the adhesion-inhibiting layers of the sole surface are evaporated and that at the same time a chemical change in Reaction layer and the inner boundary layer takes place. Thereby there is an increased adhesive force between the surface of the joint and reached the adhesive. The contactless influence of the Laser beam on the surface of the part to be bonded guarantees one consistent, reproducible quality standard of Machining results. The beam guidance of the laser can be simple any geometries of the parts to be matched, whereby a automated execution of processing also at complicated part geometries is possible.  

Further details of the invention are the following description and the drawings in which an embodiment is described. It shows

Fig. 1 is a cross-sectional view of a shoe sole;

Fig. 2 is a schematic representation of the method;

Fig. 3 shows an embodiment of the device.

In Fig. 1, a cross section through a shoe sole 1 is shown schematically. The outer boundary layer 2 of the shoe sole 1 consists of the contamination layer 4 , the adsorption layer 5 and the reaction layer 6 . The impurity layer 4 , which varies in thickness, contains solid (dust, dirt, separating wax) or liquid (oils, greases, moisture) substances which have an adhesion-inhibiting effect and must be removed before bonding. The adsorption layer 5 is formed by the absorption of foreign molecules (e.g. water, gases, etc.) and also counteracts the adhesion between the adhesive and the surface of the part to be joined. The reaction layer 6 lying under the adsorption layer 5 arises from a natural or artificial chemical change in the inner boundary layer 3 . The reaction layer 6 is firmly connected to the base material 8 due to the main chemical valence bonds and represents the actual zone for the formation of the adhesive forces. The inner boundary layer 3 forms the transition to the base material 8 . Compared to this, it has changed physical and / or mechanical properties, which, for. B. caused by a subsequent cold deformation.

Adhesive pretreatment must now do two things: The surface treatment preceding the actual adhesive process has the task of cleaning the surface and activating the surface. The surface cleaning by removing the adhesion-inhibiting impurity layer 4 and the adsorption layer 5 enables a flat contact between the adhesive to be applied and the reaction layer 6 . The surface activation creates favorable conditions for the occurrence of chemisorption.

The process for the adhesive pretreatment of shoe soles 1 made of rubber or plastic provides that the surface treatment of the shoe soles 1 preceding the bonding process is carried out by means of a contactless laser beam 100 (see FIG. 2). The energy transmitted to the sole of the shoe 1 by the laser beam 100 on the one hand causes the adhesion-inhibiting layers adhering to the sole to be evaporated, and on the other hand the effect of the laser has a depth effect which extends into the inner boundary layer 3 :

Evaporation of the anti-adhesive layers enables one Surface cleaning free from the emission of dust particles. The contactless effect of the laser beam on the  Shoe sole surface achieves a constant, reproducible quality standard of the cleaning process.

The change in the reaction layer 6 and the inner boundary layer 3 induced by the laser action is achieved in two ways: on the one hand, the bombardment of the surface with the laser beams 100 leads to a partial destruction of the polymer chains and a formation of carbon radicals due to this chain degradation. On the other hand, the air in the vicinity of the laser beam 100 is ionized and the oxygen is partially converted into the very reactive, unstable ozone. The atomic oxygen formed during the subsequent decomposition of the ozone can then react with the boundary layer molecules and / or the carbon radicals of the plastic surface and the formation of oxygen-containing polar groups. In principle, it is an oxidation reaction of the rubber or plastic surface, ie the incorporation of the strongly electronegative oxygen atom in the molecules of the reaction or inner boundary layer with the formation of functional groups, in particular hydroxyl, carboxyl and keto or Carbonyl groups. The laser treatment has the effect that the polar groups required for the formation of the secondary valency forces are generated in nonpolar plastics or the number of polar groups is significantly increased in polar plastics. The functional groups of the shoe sole 1 designed in this way can now crosslink with the corresponding functional groups of a polar adhesive, whereby an improved adhesion is achieved. The increased holding force of the adhesive connection compared to the original state is not achieved by the increase in roughness of the surface of the adhesive part, but the action of the laser beam 100 causes a chemical activation of the surface. If gluing is carried out immediately after the laser treatment, chemical sorption occurs. The connection quality is considerably better than with an exclusive cleaning treatment.

A second possibility for carrying out the method is that the treatment process is carried out in an oxygen environment. In addition to the above described, caused by the ionization effect of the laser beam 100 oxidation of the surface then also still induced by the thermal effect of the laser beam 100 oxidation reaction contributes which enhances the former.

Another way of carrying out the method is to carry out the process in an inert gas atmosphere. The improvement in the adhesion properties is then achieved via the formation of carbon radicals caused by the laser beam 100 or through the formation of an internal polarization of the polymer molecules.

Which process variant is suitable for gluing preparation of a shoe sole 1 best result for the expert from the chemical constitution of the shoe sole 1 to be processed.

The guidance of the laser beam 100 is explained on the basis of the diagram in FIG. 2. The shoe sole 1 is moved at a transport speed 61 under a laser beam 100 . In order to be able to expose each area of the shoe sole 1 to the laser action, the forward movement of the shoe sole 1 must be superimposed on a movement of the laser beam 100 which is transverse to it. The transverse speed 62 of the laser beam 100 is selected such that it covers the entire width 63 of the shoe sole 1 during the period in which the shoe sole 1 is moved further by the beam diameter 64 of the laser beam 100 . During this period, the processing surface 66 is subjected to the laser action. The individual processing surfaces 66 thus cover the entire surface of a shoe sole 1 . The processing speed 65 resulting from the transport speed 61 and the transverse speed 62 and the power of the laser must be coordinated with one another in such a way that the beam intensity per unit area required for processing the shoe soles can be applied to the shoe sole 1 .

To increase the intensity while maintaining the laser power, it can also be provided that the transport speed 61 is selected such that the individual surfaces 66 overlap.

The laser beam 100 supplied by a laser (not shown) has a typical distribution of the beam intensity over the beam diameter 64 . The laser can e.g. B. have a Gaussian (TEM ₀₀ mode) or an annular (TEM ₀₁ mode) energy distribution. In order to achieve a uniform intensity distribution over the entire beam diameter 64 , the typical energy distribution of the laser beam 100 must be converted into a uniform, flat energy distribution. For this, known temporal or spatial integration methods can be used. The temporal integration methods use mobile imaging systems such as a rotating polygon or a galvanometer scanner. In the case of spatial integration, the intensity peaks are deflected into the lower-energy edge zones of the laser beam 100 via an integrator mirror consisting of defined individual facets.

The required laser intensity per cm ² depends on the sole material to be processed. Is z. B. uses a CO ₂ laser with a wavelength of about 10 microns, so shoe soles 1 made of rubber, a laser intensity of 150 to 250 watts / cm ^{2 is} necessary to achieve a holding force of 60 to 80 Newtons. If the shoe soles 1 are made of polyurethane, a holding force of approximately 130 Newtons is achieved with a laser intensity between 200 and 350 watts / cm ² . Since polyurethane is mainly used as the sole material in the shoe industry, the method described is particularly advantageous for pretreating the soles of shoes 1 made of this material due to the high holding force achieved.

The device used to implement the method is shown in FIG. 3. The shoe soles 1 are placed on a conveyor belt 11 which is driven by a controllable motor 12 . The conveyor belt 11 consists of a laser-resistant material, such as copper or aluminum. The low absorption of these materials means that the laser beam 100 cannot couple into the strip material. The controllable motor 12 allows the transport speed 61 of the conveyor belt 11 to be changed continuously.

A polygon arrangement 200 , which serves as an imaging system of the laser beam 100, is attached to a carrier frame 10 above the conveyor belt 11 . A laser beam 100 is guided via two deflecting mirrors 30, 31 to a rotating polygon 16 which is driven by a motor 17 via a gear 18 . Each surface 19 of the polygon 16 is designed as a deflecting mirror.

Instead of the deflecting mirrors 30, 31 , any beam guiding and beam shaping system known to the person skilled in the art can be provided, which guides the laser beam 100 from the laser resonator to the rotating polygon 16 .

The polygon arrangement 200 is aligned with the direction of movement of the conveyor belt 11 determined by the transport speed 61 such that a laser beam 100 impinging on a surface 19 of the polygon 16 is deflected transversely to the direction of movement. The rotation of the polygon has the effect that the angle of incidence of a laser beam 100 impinging on a surface 19 of the polygon 16 is constantly changed.

As a result, the laser beam 100 is guided once across the width 63 of the shoe sole 1 during the passage time of a surface 19 of the polygon 16 . The resulting processing surfaces 66 thereby cover the entire surface of a shoe sole 1 . The number of revolutions of the polygon 16 and thus the deflection frequency and the transverse speed 62 can be regulated by the motor 17 .

The motors 12 and 17 make it particularly easy to match the transport speed 61 of the conveyor belt 11 and the transverse speed 62 of the laser beam 100 to the predetermined power of the laser in such a way that the laser intensity required to carry out the method is applied to each surface unit.

In order to adapt the beam guidance to the geometry of the shoe sole 1 to be machined, it is provided that the polygon arrangement 200 can be rotated and adjusted in height relative to the conveyor belt 11 . For this purpose, the polygon arrangement 200 is connected to a plate 14 which is moved vertically up and down via a pull spindle 13 driven by the motor 25 and which can be rotated in the direction 26 about the axis 24 of the pull spindle 13 . The change in the distance of the polygon 16 from the conveyor belt 11 makes it possible to vary the deflection 73 of the laser beam 100 . As a result, this size can be matched particularly easily to the width 63 of a shoe sole 1 . Due to the rotatability of the plate 14 , the position of the processing surfaces 66 can be changed relative to the direction of movement of the conveyor belt 11 . The height adjustment and the rotatability of the polygon arrangement 200 allow flexible beam guidance, which can be adapted particularly easily to the geometry of the shoe soles 1 to be processed by control devices known to the person skilled in the art. A largely automated adhesive pretreatment of the shoe soles 1 is thereby achieved, since the laser beam 100 can be guided to any desired location on the shoe sole 1 by the control devices. The flexible control of the laser beam 100 also makes it possible to process only one or more selected partial areas instead of the entire width 63 of the shoe sole 1 .

In order to be able to change the position of the impingement points 70 of the laser beams 100 on the conveyor belt 11 independently of the orientation of the polygon arrangement 200 , the polygon 16 is slidably mounted in the guide grooves 22 of a guide block 21 located on the plate 14 via two bolts 20 . This allows e.g. B. to treat the edge areas of the shoe sole 1 separately. A counterweight 23 counteracts tilting of the plate 14 and ensures that the tension spindle 13 is always perpendicular.

It is also possible to operate the laser in a pulsed mode. The devices for beam guidance described above then, in conjunction with an incremental encoder acting on the control devices, allow the individual processing surfaces 66 to be applied in a mosaic shape to the shoe sole 1 . The laser beam 100 draws an interrupted, arbitrarily selectable track over the surface of the shoe sole 1 . This allows the laser beam 100 to be guided particularly easily over partial areas of the shoe sole 1 which are not intended for treatment.

To supply the oxygen or inert gas are the Devices known to those skilled in the art are provided, which are not here to be shown.

After the adhesive pretreatment, a suitable adhesive is applied to the shoe soles 1 in a manner known per se. The person skilled in the art knows which adhesive to choose based on the material properties of the shoe soles 1 and the desired purpose of the adhesive.

The method outlined above and the one described Embodiments of the device are not only for gluing of shoe soles applicable. Because of the above It is readily apparent to those skilled in the art that the Rather the object of the invention for the preparation of adhesives Joining parts of different geometries and different Materials can be used in a particularly advantageous manner.

Claims (9)

1. A method for gluing rubber or plastic parts, in particular for shoe soles, characterized in that a laser beam ( 100 ) is guided over the parts ( 1 ) before the adhesive is applied in such a way that the removal of the parts ( 1 ) adhering adhesion-inhibiting layers ( 4, 5 ) is brought about by the thermal energy applied by the laser beam ( 100 ), and that the adhesion between the joining parts ( 1 ) and the adhesive to be applied to the joining parts ( 1 ) by chemical induced by the laser beam ( 100 ) Reactions in the reaction layer ( 6 ) and the inner boundary layer ( 3 ) of the parts to be joined ( 1 ) is increased. 2. The method according to claim 1, characterized in that the action of the laser beam ( 100 ) on the surface of the joining parts ( 1 ) is carried out in a normal ambient atmosphere. 3. The method according to claim 1, characterized in that the action of the laser beam ( 100 ) on the surface of the joining parts ( 1 ) is carried out in an oxygen atmosphere. 4. The method according to claim 1, characterized in that the action of the laser beam ( 100 ) on the surface of the joining parts ( 1 ) is carried out in an inert gas atmosphere. 5. The method according to any one of claims 1 to 4, characterized in that the joining parts ( 19 ) are moved by a transport device relative to the laser beam ( 100 ), and that the laser beam ( 100 ) through an imaging system ( 200 ) transverse to the direction of movement of the joining parts ( 1 ) is distracted. 6. The method according to claim 5, characterized in that the transport speed ( 61 ) of the joining parts and the transverse speed ( 62 ) of the laser beam are so matched to the power of the laser that on each surface element of a processing surface ( 66 ) that to achieve the desired adhesive force necessary laser intensity is applied. 7. The method according to any one of claims 1 to 6, characterized in that a non-uniform distribution of the intensity of the laser beam ( 100 ) over the beam diameter ( 64 ) by a spatial or temporal integration method is converted into a uniform, flat distribution of the intensity. 8. The method according to claim 7, characterized in that stationary or movable imaging systems ( 200 ) for integrating the laser beam ( 100 ) are used. 9. The method according to any one of claims 1 to 8, characterized in that the joining parts ( 1 ) consist of polyurethane material.