DE2560278C2 - Process for joining the surface of a shaped body made of an organic polymer to a carrier - Google Patents

Description

15th

JO

The invention relates to a method of joining the surface of a shaped body made of an organic polymer with a carrier by treating the surface before the shaped body by heating to its softening point and by corona discharge and by gluing by means of a layer of an adhesive.

It is known that various plastics, such as films made of polyethylene, can be treated with a corona discharge - <<> in order to be able to better connect the treated substances to different substrates. Most of the commercial general contractors. use alternating currents with frequencies up to 500 kHz or more to generate corona discharges. Voltages of 15 kV or more are used to treat a film of a polymer which is continuously passed between the two electrodes at a speed of up to 15C m / min or more. V)

When carrying out this process, the surface is usually ^{irradiated with 0.09 to 0.35 watts min./dm 2} to make it receptive to adhesives, printing inks and other polar substances.

U.S. Patent 3,496,092; 32 94 971 and 37 29 672 describe generators for corona discharges and / or methods for treating films. It is accordingly known that when a film made of a polymer is treated with a corona discharge of 0.01 to 0.35 watts Mln./dm ', the adhesiveness of the surface ^h0 of such a film can be increased sufficiently.

It is also known that a film made of a low density polyethylene can be welded to a support made of steel or aluminum if it is treated with heat. Thus, examples ^b5 game, a film made of polyethylene on a Mctnlltrü- be applied • ger, which is heated above the melting point of the polyethylene, and then the laminated body is further heated to a temperature above HO'C v, ird to the film made of polyethylene with to weld or connect to the carrier. Although this method can be used to bond or weld a film of a polymer to a metal, it does require double heating. Here, the second heating is carried out while the film is in contact with the metal. This method cannot be used in cases where the metallic support is not to be heated.

According to US-PS 36 39 134 is a plastic film for Improvement of the adhesion to a hot sealable Surface after extrusion from a conventional extruder to a temperature of about 25 to 50'C heated below its softening point and treated at this temperature with a corona discharge. This method requires a device through which the plastic is at the elevated temperature is held while concurrent with a corona discharge is produced.

From US-PS 37 54 117 it is known for surface treatment a layer of plastic to heat this as high as the film can withstand. the Corona-Bchandlungselnrlichtung is in this device attached directly to the exit of the extruder head, from which the film emerges at a high temperature and immediately, still hot, exposed to the corona. This is according to US-PS 37 54 177 as much more effective compared to a corona treatment of the film cooled to room temperature.

The object of the invention is to create a method for connecting the surface of a molded body made of an organic polymer to a carrier Heating of the shaped body bi = to its softening area and by corona discharge and by gluing by means of a layer of an adhesive.

This task is solved by the Im label of the main claim specified features.

The so treated surface of the molding'-m has an improved adhesive film for adhesives. to bond moldings with mlucls adhesives to metals or other carriers.

The term »molded bodies« used here refers to films, foils or other objects made of materials, such as polypropylene, polyethylene, flexible polyvinyl chloride and the like.

The heating of the molded body made of the polymer to temperatures between about 40 ° C. and the melting temperature Is required to the surface of the molding to change so that she becomes more receptive to them Treatment with a corona discharge, whereby the Adhäslonsfähßkeit the surface treated in this way is significantly improved. The structure of the curses of heated moldings made from a polymer Is not exactly known. Therefore, the invention The procedure is not tied to any particular theory be. However, it is believed that when one is heated Molded body made of polymer a coming together of smaller crystals takes place, whereby tufts or spheres roll arise with gaps between the crystals or spherical rolls. This change in the surface of the Moldings made from the polymer apparently do not cause any tension on the surface, but change it in this way. that the treatment with a corona discharge becomes more effective. It can be assumed that b ^ when heated of the lamellar crystals of the polymer with thicknesses from ctwn 100 Å and widths from I to 100 microns at a temperature slightly below your melting point

Lamellae through self-diffusion along the carbon chain of the molecule become thicker. This increase in thickness is likely to be accompanied by the formation of Holes or cracks, which could be a reason for the change in the surface. Additionally can be accepted that the change in the surface is also caused by the emergence of chemical. Ties during the oxidation of the polymer on heating. Probably the combination of the resulting chemical bonds together with the formation of tufts or spherules on the surface such a change in the surface that they become changed advantageously after treatment with a corona discharge. This very largely increased adhesiveness exceeds that of a professional expect when he is the surface of a polymer in the heat or treated by a corona discharge. So it is a synergistic one Effect that by itself neither by heating nor by treatment with a corona discharge can be generated. This effect is greater than the sum of the individual effects of warming or a treatment with a corona discharge. Probably the higher the energy expended ever Flat unit of the film is partly responsible for this synergistic effect.

In order to achieve the required change in the surface of molded articles made of polymers, the molded article or parts thereof are heated to above about 40 ° C. to below the melting temperature. The respective heating temperature depends on the desired adhesive wedge. In no case the polymer body solo above its melting point Warming ^1, are well integrity would be lost here.

After heating, the shaped body is cooled to below about 20 ° C., with the desired crystal growth is not changed and with no undesirable stresses or other properties arise that affect the surface and its adhesive feel would be harmful after treating with the corona discharge.

The shaped body made of the polymer, which has been pretreated by heating, is then treated with a corona discharge of a known type, with the exception that the energy per unit of the film surface is more than twice as high, preferably more than ten times as high, than in the known processes. Polypropylene films, for example, are produced using the known processes. Polyethylene or flexible polyvinyl chloride treated with a corona discharge of 0.09 to 0.35 watts min./dm '. According to the invention, for example, a film made of polypropylene is treated after the heat treatment with a corona discharge of at least I., preferably more than about 3.5 watt min./dm ² , in order to achieve the desired adhesive strength. It is also possible to use both sides of a film made of, for example, polypropylene. Polyethylene or flexible polyvinyl chloride are treated if both are rarely to be connected to carriers, for example with metals. Preferably, both parts of the film are treated simultaneously with a corona discharge.

The Flg. I to 4 each show In 150x magnification the surface of an untreated or by corona discharge, by heat or according to the invention first by heating, then by means of a corona discharge, conduct film made of polypropylene with a Thickness of 0.25 mm.

The I ⁷ Ig. 5 and 6 / inherently from the front and from the side an I ⁷ IIm, which is glued to a metal carrier, which in turn is connected to a rigid carrier plate.
Fig. 7 shows from the side the components of Flg. 5, wherein the polymer film is connected to one lndc with one clamp and the rigid support is connected to another clamp. This arrangement shows the method of testing the adhesive strength of the film from the polymer.

in The essence of the invention is that the Adhesion strength of a film made of a polymer treated according to the invention is greater than the sum of the Adhesion strengthening of a film from a polymer, alone in the warmth or alone by a corona

r> discharge has been handled. These; synergistic Effect could be due to the increased energy of the corona discharge after treating the film by heating.

According to the invention, by heating and by means of a corona discharge treated shaped body made of a polymer has a surface with an improved Adhesiveness when a 2 5 cm film with a nickel plated steel plate with a middle layer of 0.075 mm on a steel plate of

> 3 0.1 mm is connected by means of a 0.025 mm thick Layer of an adhesive made of fatty polyamide with an amine number of about 70 and a melting point of about 165 "'C. so is an adhesive force of at least 1.25 kg / cm. preferably of at least

H '1.6 Kp'cm. required to hold the film after folding it back peel in a direction parallel to the surface of the plate. This Mlndcsiauhüslonsfesilgkelt von The molded body made of the polypropylene receives 1.25 Kp / cm after the treatment by heating with a

) "· Treatment with a corona discharge of about 4 watt min. which is about ten times higher than that commonly used corona discharge. In order to obtain a preferred adhesion area of 1.6kp.'cm, should the shaped body do so after the treatment

■ »" Heating with a corona discharge of around 7 watts Min./dm 'are treated to the required to achieve a synergistic effect. A similar method for determining the Adhi'.slonsfestigkelt is In ASTM D903-49. The adhesive strength

^{J <} of moldings treated according to the invention is significantly higher than the adhesive strength of moldings which have been treated solely by heating or which have been treated solely with a corona discharge of low Fnergle, the films in each case with the

■ - "the same adhesive are connected to the steel surface.

Another characteristic of those treated properly Surfaces consists in that these surfaces of polar liquids can be bcnet / i. These Wettability by polar liquids is important.

^Vi if an adhesive made of a fatty polyamide with a melting point of 165 ° C. and an amine number of about 70 is used. Such an adhesive is used to bond an untreated film made of polypropylene, polyethylene or flexible polyvinyl chloride

·> 'With a metallic, deceiver, so find a bad one Bonding takes place because the polar adhesive touches the surface of the film is not wetted enough for a complete To achieve connection. If, however, a bottle that has been properly treated is used, its surface is used

^b5 consistently wettable by the adhesive, as a result of which the film is firmly bonded when this adhesive is used

According to the invention, fatty polyamides made from two-base fatty acids are used as adhesives. Fatty polyamides are condensation products of dl- and polyfunctional amines and dl- and polybasic acids, which are obtained by the polymerization of unsaturated acids from vegetable oils or their esters. Fettpolyamlde are particularly well suited as adhesives for joining conductive metals, such. B. of nickel-plated steel, with a film of a polymer treated according to the invention, r. B. made of polypropylene. This creates a composite which is particularly suitable for use in alkaline galvanic cells. Fatty polyamides are not only good adhesives, they are also not wetted and attacked by alkaline electrolytes, and can therefore delay the creep of such electrolytes or out of the cells during prolonged periods. The use of fatty polyamides in galvanic cells is described in US Pat. No. 3,922,178. The invention can be used to make flat alkaline cells.

The synergistic effect with regard to the adhesive properties of molded articles treated according to the invention can be seen in the examples below.

example 1

Various 2 × 5 cm films made of polymers with the thicknesses given in Table I were tested for their adhesiveness. Here they were first connected between two identical sheets of nickel-plated steel of 5.4 χ 2.0 cm using a 0.025 mm thick layer of an adhesive made of a fatty polyamide (condensation product of dl- and polyfunctional amines and dl- and polybasic acids, obtained by polymerizing unsaturated vegetable oleic acids or their esters, with an amine number of about 70). This adhesive was applied to one side of each of the plated steel sheets. The whole was pressed together using a conventional pulse heater made of chromium for 3 to 7 seconds at 120 ° C. under a pressure of 55 kgf / cm ² in order to bond the polymer tightly to the metal sheets by means of the adhesive. Then, thin metal sheets were peeled from the polymer nickel. It was checked visually what amounts of the adhesive had remained from the film and on the carrier, so that the effective adhesion to the film made from the polymer can be determined.

Table I shows the results of adhesion tests for various films made from polymers that were either untreated, heat treated only, corona treated only, or heat and corona treated. The films to be treated by heat were first cut from a sheet of polypropylene, then each sample was heated in an oven to a temperature of 115 to 12O ⁰ C, cooled, removed from the oven and cooled to room temperature.

Some of the untreated and some of the heat treated film samples were then treated with a corona discharge, the surface of the film being irradiated ^{with 12 watts min / dm 2.}

In the table means:

"No Adhesion": The laminate could be easily separated and no adhesive adhered to the film.

"Low adhesion": The laminate could with relatively only little force can be removed and less than 10% of the surface of the film remains with it Adhesive covered.

"Moderate Adhesion": A greater force was required to pull the laminate apart, and 10 up to 25% of the surface of the film remained covered by adhesive.

"Adhesion": It took a relatively large force to separate the metal sheets from the film and at least 80% of the surface of the film remained covered with adhesive.
Table I shows that the synergistic effect of the

sequential treatment du ^rcn heat and by corona irradiation could not be predicted by determining the Adhäsionsfähigkelten of polymer films which had been treated by heat alone, or solely by corona discharge. This synergistic effect may be due to the high energy per surface area of the surface during corona irradiation, which is higher than the usual energy consumption. ;

Table I.

Material treatment

none heated

Corona heated

Discharge and

Corona discharge

Polypropylene none none weak adhesion (0.25 mm)
Polyethylene
(0.25 mm)

flexible
PVC
(0.40 mm)

Adhesion adhesion adhesion

none none weak adhesion adhesion adhesion adhesion

none none weak adhesion adhesion adhesion; ion adhesion

Example 2

A sample was made from a 0.25 mm thick polypropylene film cut. Using a scanning electron microscope, a Photomicrograph of the untreated film made from polypropylene, shown in FIG. 1 is shown. Of the Film was then heated in an oven to 115-120 ° C, then removed from the oven and brought to room temperature cooled down. The surface photographed with the same device and the same magnification of this film is in the wing. 3 shown. The Flg. 3 shows that the crystals have joined together to form clusters or spheres with clear Gaps between adjacent tufts. It is believed that in addition to the formation of the tufts or Spherollte also the dimensions of the crystals at Warming have increased.

A second sample of the same polypropylene film was treated with a corona discharge of 12 watt min./dm '. Treatment lasted about 10 Seconds. A microphotograph of the film treated in this way shows FIG. 2. It shows that the surface of the Crystals has increased, probably due to a corrosive effect.

A third sample of the same film was treated by heating as described above and then by corona irradiation as described above. The surface of the film treated in this way is shown in the figure. 4 shown. As you can see, the surface of the film has changed and the dimensions of the crystals have increased. As Example 1 shows, the surface has

before a film treated in this way an excellent one Adhesiveness.

Example 3

Various patterns of a film of polypropylene having dimensions of 15 χ 2 cm and a thickness of 0.25 were each connected to a 5x2 cm, plated with nickel steel plate _ö mm. For this purpose, a 0.025 mm thick layer of the adhesive mentioned in Example 1 was used. According to FIGS. 5 to 7, a part 3 of each pattern of the film 2 made of polypropylene was nicked to the sheet 6 by means of a layer 4 of adhesive; Clad steel connected, the latter being welded to a steel plate 8 serving as a carrier. One clamp 10 was connected to one end of the carrier plate 8, and the other clamp 10.4 of the sensor was connected to the free, folded-back end 2 of the film 3. The force required to pull off the film 2 from the sheet 6, which acted on the clamps 10 and 10/1 parallel to the surface of the sheet 6, is contained in Table II.

The various samples of the polypropylene film were either untreated by heating alone treated, treated solely by corona discharge or by heating and irradiation with a corona Discharge treated before being connected to the sheet metal became. The treatment by heating and by irradiating with a corona discharge was carried out so that as described in example 1.

The values of the adhesive force for peeling each sample of the polypropylene film from that of the nickel Clad steel plate using the procedure described are included in Table II sees that the pattern (4) treated by heating and irradiating with a corona discharge had an adhesive strength wedge of 1.85 kgf / cm. The pattern treated only by heating (2) had an adhesive strength of less than 0.18 kgf / cm, and the sample (3) that passed alone Irradiation treated with a corona discharge had an adhesion strength of 1.25 kp / cm. These Tests show the synergistic effect of the combined process according to the invention on the adhesive properties the surface of a film made of polypropylene.

The relatively high adhesive strength of the pattern (3) could be due to the fact that the treatment with the corona charge was carried out with an energy of 12 watts min./dm ² , which is about thirty times higher than the energy usually used for treating Polymer surfaces.

The pattern (5) shows that it is necessary to make the film made of polypropylene to be treated first by heating, and only then to be treated by a corona discharge. If these steps are reversed, the adhesive strength decreases.

Table II

Pattern film made of polypropylene

Adhesion strength wedge (kp / cm)

1 as received
untreated

2 by heating alone
treated to 120 ^{0 C.}

continuation

Pattern film made of polypropylene

Adhesion

strength

(kp / cm)

just by treating with a 1.25
Corona discharge of 12 watts
Min./dm ²

by heating to 120 ^° C. and 1.85
then with a corona discharge of 12 watt min./dm ²
treated

first with a corona discharge 1.20
of 12 watt min./dm ² and then by heating up
120 ⁰ C treated.

Example 4

Using the tests to determine four adhesion strengths according to Example 3 with the adhesive described in Example 1, 0.25 mm thick films of polypropylene with the dimensions according to Example 3 were treated first by heating and then with corona removal. The bond strengths were then tested. Each of the various samples was heated differently and treated differently with a corona discharge before being bonded to the sheet of steel clad with nickel. The bond strengths are given in Table III. It can be seen that the adhesive strength of films made from propylene can be significantly improved if the films are treated in accordance with the invention. The test results also show that the change in the properties of the surface of the polypropylene film is dependent on the temperature and the applied energy of the corona discharge. Heating the sample to 120 ° C. and treating it with a corona discharge of 6 watt min./dm ² results in an adhesive strength which is approximately the same as the adhesive strength of a film which is heated to 80 ° C. and has a corona discharge of 12 watt min./dm ² treated lsi. The test results also show that the temperature of the heat treatment and the energy of the treatment with the corona discharge are synergistically linked to one another and can be changed in such a way that the surface has the desired adhesion in each case.

Table III

Polypropylene films 0.25 mm thick

Heat treatment corona discharge Adhesion strength ⁰ C watt min./dm ² kp / cm

<0.18 <0.18

20th 1 <0.18 70 1 <ü, 18 90 1 <0.18 110 1 <0.18 120 i 0.25 20th 3 0.42 70 3 0.51 90 3 0.73 120 3 0.91

continuation

Polypropylene films with a thickness of 0.25 mm

Heat treatment corona discharge Adhesion ^{strength 0} C watt min./dm ² kp / cm

6th 12th 12th 12th 12th 12th

Example 5

1.05 1.45 1.23 1.31 1.52 1.65 1.88 Polyvinyl chloride also increases as the ad ^u., Is! Oribfesllgkclt of films of polypropylene, when treated erflndungsgcmüß.

Table V

Material heat- corona- acirusion-

C, 25mm treatment discharge strength

thick film ⁰ C watt min./dnv kp / ern

IO

It was seducing for example ^Λ used, samples were used films of polypropylene by the »■> Example 3. FIG. The results are given in Table IV.

The test results show that when the Energy of the corona irradiation, the adhesion festlgkalt of patterns heated to the same temperatures 2S were also increasing.

Table IV Polypropylene films with a thickness of 0.25 mm

ίο Heat treatment corona discharge Adhesion ^{strength 0} C Watt Min./dm ² kp / cm

Polyethylene 20th 12th 1.27 Polyethylene 100 12th 1.58 Polypropylene 20th 12th KU Polypropylene 120 12th 1.55 flexible PVC 20th 12th 0.84 flexible PVC 80 12th 1.03

<0.18 0.42 1.23 1.31 1.49 1.55 1.89 0.33 1.07

Example 6

Following the procedure of Example 3, samples of flexible polyvinyl chloride films were made. Polypropy-> <> lcn or polyethylene tested. The patterns keep the same Dimensions as in example 3. The results are included in Table V.

The test results show that the adhesion strengthens of films made of polyethylene or flexible 5> Table V shows that the adhesive strength of the The substances tested are comparable to the figures in Tables 11 to IV. They can be regulated in such a way that the bond strength between nickel plated Steel and the film at layer thicknesses of the adhesive according to Examples H to IV can be gcrcacU.

The examples show that a treatment of an unmarked surface of a molded body made of a polymer with a corona discharge of about 12 watts per meter significantly increases the adhesion strength for adhesives. Examples 3 to 6 show that when a polypropylene film is treated with a corona discharge of 12 watts min./dm "'an adhesive strength on a metallic carrier of at least 1.11 kp / cm is achieved according to example 3. According to example 6 A polyethylene film treated with a corona discharge of 12 watts Mln./dm ^{J has} an adhesive strength of 1.2 kg / cm, while a film made of flexible polyvinyl chloride treated in the same way has an adhesive strength of 0.84 kg / cm . According to the invention can therefore treat a polymeric molded article having a corona Eniladung of greater than about 12 watts Mln./dm ¹ to the surface more receptive ll \ r adhesives, or to make like.

The examples show ajch. that when the molded bodies made of polymers are treated according to the invention, their surface changes in such a way that they are wetted by an adhesive which cannot wet an untreated polymer well. This makes it possible to connect molded articles made of polymers treated according to the invention to various carriers using conventional and readily available adhesives, and that such substances, as described above, can be used in alkaline cells.

For this purpose 2 sheets of drawings

Claims (2)

Patent claims: 1. A method for connecting the surface of a shaped body made of an organic polymer with a sluggish · by treating the surface of the Molded body by heating up to its Erwclchungsberelch and by corona discharge and by gluing by means of a layer of an adhesive, characterized in that a) the shaped body first to a temperature between 40 ° C and heated to its melting point, b) cooled to a temperature below about 20 ° C and c) is then irradiated with a corona discharge which has an energy density of at least 1 watt ■ mln / dm ^J on the surface, and d) then with the carrier by an adhesive is glued, which is a condensate product of two or more functional amines with two or polybasic acids, which have a melting point of about 165 ° C and an amine number of about 70, the adhesive being used in a layer thickness of about 25 μm. 2. The method according to claim 1, characterized in that the treated shaped body on a Surface is glued by nickel. ok