JPH0159099B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to the bonding of plastic materials, and more particularly to the preparation of plastic materials for adhesive bonding to or to similar or dissimilar plastic materials.

Polypropylene can generally be adhered to itself or to other plastic or non-plastic materials with adhesive forces suitable for many purposes using adhesives. This adhesion is generally improved if the plastic material surfaces to be bonded are first subjected to oxidation by being exposed to a hot blue gas flame for a few seconds until a dull finish is achieved on these materials. however,
Although such oxidative pre-treatment attempts to sufficiently bond the plastic surfaces, it is unlikely that the bond will be truly sufficient to withstand substantial stress and therefore the bonded plastic product will not be fully bonded. It has hitherto been impossible to be able to use it for structural purposes. In accordance with the present invention, a method is provided for pretreating a plastic surface prior to bonding it to another surface through the use of an adhesive. The method involves exposing the plastic surface to a hot blue gas flame. The gas flame contains an oxygen content that is as little as possible above the oxygen content that will maximally ionize the gas in the blue region, thereby achieving an adhesive and desirable matte finish on the surface of the plastic material. .

Furthermore, according to the invention, an apparatus is provided which is used for the preparation of surfaces of plastic materials to be bonded with adhesives. The device has a burner which generates a flame for matting the surface of the plastic items to be bonded. The burner comprises a gas inlet means, a gas outlet means, a current collection means disposed within the flame produced by the burner, an amplifier for amplifying the current or voltage resulting from ionization within the flame and the resulting current. or means for reading or recording the voltage.

The method of the invention is particularly well suited for the pretreatment of polypropylene surfaces to be bonded to similar or different plastic materials. Nevertheless, this method can generally be applied to the bonding of plastic materials that have undergone surface oxidation and are therefore matted before bonding takes place. The method of the invention has been found to give excellent results when applied to the pretreatment of fluorin-containing polymers such as polytetrafluoroethylene, polycarbonate, silicone resins, and melamine-formaldehyde resins.
In the case of these last-mentioned plastics,
It has been found that the method of the present invention renders such plastics bondable using cyanoacrylate resins which were previously not possible to use with such plastics. In addition to preparing plastic materials for plastic bonding, plastic materials pretreated by the method of the invention may be used, for example, Silcoset 152 and 153 and Dow Corning
Using a silicone adhesive like RTV adhesive,
Can be adhered to other materials such as moderately degreased metal. Bonding during bricklaying can be accomplished using silicone-based sealing compounds currently available in the building trade.

When carrying out the method of the invention, the extent to which the plastic surface is exposed to the blue region of the flame depends on the plastic material being treated and must be determined by testing for each particular material. The best test for a successful pretreatment may in fact lie in a complex method of structural testing, but in practice, the appearance of the treated area is examined to determine if it has a high degree of matteness. Good preparation can generally be assessed by performing a simple wetting test. In general, it has been found that the method of the invention provides particularly good results when an organosilicon adhesive is made from the adhesive that cures to an elastic mass.

The ionization occurring in the blue oxidation region of the treatment flame is successfully determined as follows. That is, even a pair of electrically connected wires with a suitable thermal resistance network or gap is inserted into the flame and can draw several microamps, depending on the current collector used, but typically only a few nanometers. It can be determined by electrically amplifying the small amount of current produced in the flame when currents on the order of amperes occur. Insofar as gauze can be used, the term "gauze" is used here to refer to an electrically conductive, usually metallic structure that has a wide open surface through which the flame can pass. It acts on the plastic material being treated. It is therefore also possible to use perforated or expansive metal sheet structures, although a mesh in the conventional sense may also be used.

In order to understand the invention more deeply and to show how it can be carried out in practice,
Reference is now made to the accompanying drawings by way of example only.

According to the figure, the burner illustrating an example of the invention is
It has an angular metal tube, for example a copper tube 1. This tube 1
has an inlet pipe 2 for gas and air and is closed off on the opposite side. The gas and air are sealed off at its inner end, around which a plurality of outlets 4 are arranged to ensure a homogeneous distribution of the combustion mixture within the tube 1 and to ensure the flame This will give it a uniform height. Beyond the corner 5 provided on the tube 1, the tube 1 is surrounded by a copper tube 6. Over some length and width covered by the copper tube 6, the inner tube 1 has an opening 7 which is aligned with an opening 10 in the copper tube 6, above which double thickness opening there is a A fine mesh mesh of stainless steel is arranged. This screen is held in place by an outer tube 9 around the copper tube 6 and is preferably made of aluminum, whose high thermal conductivity prevents the edges of the flame from reaching extreme temperatures. Second
As can be seen, the opening 7 of the inner tube 1 is narrower than the corresponding opening 10 of the copper tube 6.

A suitably supported metal mesh 11 is spaced from the mesh 8 and is generally more coarsely woven than the mesh 8, from which conductive wires 12 extend to a current amplifier 13. The amplifier 13 is a microampere meter 1
It is attached to 4. This amplifier 13 is further connected to the copper tube 1 via a conducting wire 15.

When the gas burner is used, a mixture of gas and air is fed into the angular copper tube 1 via the inlet tube 2 and the outlet 4. That is openings 7 and 1
When it exits the angular copper tube through 0 and ignites, a flame 16 is created. Its construction is more clearly shown in FIG. This elongated flame impinges on the surface of the sheet plastic material to be subjected to adhesive bonding and achieves a matting of that surface. The metal mesh 10 is placed at a suitable position in the resulting flame, preferably in the blue portion thereof, and the ionization that occurs in the flame and is greatest in the blue portion is transmitted to the amplifier 13 and the resulting amplitude current is microampere. A total of 14 readings are made. According to the invention, the control of the flame is such that gases such as propane or butane, and oxidizing gases, generally air or oxygen, are completely combusted so that ionization is maximized and therefore an optimal pretreatment of the plastic material is achieved. done until done.

The machine can be configured in accordance with the invention so that areas along the edges of sheet plastic material, such as sheet polypropylene, are flame treated. For this purpose, the burner 2 shown in the accompanying drawings
A platform is placed on a pedestal with an overturning drive capable mechanism for conveying the burners at a substantially uniform speed along the edge to be treated. When the pedestal is in its normal position, the burner flames each extend into an ion collection network and the resulting small current is electrically amplified as described above to achieve optimal flame conditions before moving the pedestal and Pretreatment of sheet plastic materials can be accomplished.

Although the detection of current has been described here with diagrams, since voltage is also produced, voltage amplifiers and voltmeters can be used to determine when maximum ionization of the gas will occur in the flame and therefore when in the combustible gas. It is equally possible to establish how to set the oxygen content of

(Effects of the Invention) The present invention provides that when a pair of current conductors (electrodes) with a gap are arranged in a gas flame, the current conductor They found that the current or voltage measured through the combustible gas changes, and that this electrical property is related to the oxygen content in the combustible gas and is well indicative of changes in the oxygen content. According to the present invention, the oxygen content in the gas flame can be successively measured and the oxygen content of the combustible gas can be adjusted to be optimal for matte finishing, so if the concentration of flammable gas changes during use, , even if the type of combustible gas changes, it is possible to always supply combustible gas with the appropriate oxygen content.
Provides the best matte finish during use.

[Brief explanation of drawings]

FIG. 1 is a partially sectional front view of a burner showing one embodiment of the present invention, and FIG. 2 is a front view of a burner shown in FIG.
FIG. 1...metal pipe, 2...inflow pipe, 4...outlet,
7,10...opening, 8,11...metal mesh, 13...
...Amplifier, 14...Ampere meter, 16...Flame.

Claims (1)

[Scope of Claims] 1. A method of pretreating a plastic surface to achieve an adhesive and desired matte finish on the surface of the plastic material before bonding the surface to another surface using an adhesive, comprising: , the method includes exposing the plastic surface to a hot blue gas flame, the gas flame containing an oxygen content as little as possible above the oxygen content that will maximally ionize the gas in the blue region of the gas flame. , a means for determining the oxygen content that maximally ionizes gas in the blue region of the gas flame, the method comprising the steps of: (a) A process in which a pair of current conductors electrically connected with a certain gap are inserted into a flame, and the minute current generated in the flame is electronically amplified via the current conductors and then monitored; (b) Setting the oxygen content in the gas flame to maximize the current or voltage conducted by the current conductor. 2. The method according to claim 1, applied at any time to the pretreatment of polypropylene surfaces. 3. A method according to claim 1 or claim 2, wherein the current conductor forms part of a refractory metal mesh inserted into the flame as specified above. 4. In order to determine the oxygen content of the gas at which maximum ionization of the gas occurs in the blue region, the gas is combusted in an elongated burner, which comprises inlet means for combustible gas and oxidizing gas and gas outlet means. a pair of electrically connected current conductors arranged in association with said gas evacuation means to be located within a flame produced in said burner, and a current produced within said flame; 4. A method according to any one of claims 1 to 3, further comprising means for reading or recording the voltage. 5. According to claim 4, the inflow means is arranged at one end of the elongated burner, the opposite end thereof is closed, and the gas discharge means is constituted by an elongated hole in the side wall of the burner. the method of. 6. The method of claim 5, wherein the elongated burner is reinforced near the ejection means by a metallic sleeve having another elongated hole mounted thereon and aligned with the elongated hole. . 7. The method according to any one of claims 3 to 5, wherein the gas exhaust means is covered with a fine mesh metal mesh. 8. A method in which claim 7 falls under claim 4, wherein the heat-resistant metal mesh has coarser mesh than the finer mesh metal mesh. 9. A method according to any of claims 1 to 8, wherein the current conductor is placed in the blue portion of the gas flame. 10. A method according to any one of claims 1 to 9, in which, in a next working step, the already pretreated plastic surface is bonded to another surface with an organosilicon adhesive. 11. A device for pretreating a plastic surface before it is bonded to another surface using an adhesive, consisting of a tube producing a flame for matting the surface of the plastic article to be bonded; A gas-fed burner having gas inlet means and gas outlet means, current collection means disposed in the flame produced by the burner, and an amplifier for amplifying the current or voltage resulting from ionization in the flame. and means for reading or recording the current or voltage produced thereby. 12. The apparatus of claim 11, wherein said current collection means is a refractory metal mesh as previously identified.