DE2828673A1 - Stretchable vulcanisable adhesive film - with polyolefin carrier and rubber adhesive, used for splicing internal belts of tyres - Google Patents

Abstract

The film, in sheet or tape form comprises (1) a thin film of a polyolefin contg. crystalline fractions, which has been slightly stretched biaxially on mfr, as carrier, and (2) a thin layer applied onto one side of (1) of a natural and/or synthetic rubber adhesive, opt. contg. small amts. of adhesive resins and/or anti-ageing agents. Used for splicing the internal belts of tyres (protecting the overlapping joints in the interior of tyres) during the tyre mfr. The carrier (1) is 5-50, esp. 10-30 mu m thick and pref. comprises an isotactic polypropylene; (2) comprises 95-100% of the rubber and 0-5% of a suitable anti-ageing agent.

Description

Beiersdorf Aktiengesellschaft Hamburg

Stretchable, vulcanizable adhesive

The invention relates to a stretchable, vulcanizable one Adhesive film in sheet or web form, which is used in particular for splicing the inner core of radial tires (protection of the overlap joint inside radial tires) in tire manufacture.

In a certain operation in the course of the manufacture of radial tires, their use instead of the usual tires * types for vehicle tires in road traffic brings many advantages (shorter braking distances, longer service life, lower spec. Ground load, less warming and better cornering resistance), the problem arises, one approach to have to glue over the inner surface (splicing of the inner core) in order to protect the overlap joint to achieve inside the radial tire.

To solve this problem, adhesive tapes are particularly suitable, which are essentially for this special application must meet two requirements:

1. The adhesive tape should come out together with the base when the blank is curved out the rubber mixture can be deformed without loosening.

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2. The adhesive tape should not interfere with the vulcanization process of the tire and should not reduce the strength of this or other attached layers.

The known adhesive tapes used hitherto for this purpose meet at most one of these two requirements, what Requires additional work (re-pressing loosened ends or removing the adhesive tape before vulcanization) .

The object of the invention was therefore to develop an adhesive tape that would meet not only one, but both of the requirements mentioned fulfilled in full and therefore particularly suitable for use for the specified special purpose is.

The solution to this problem consists in a stretchable, egg nvulkani si erbaren adhesive film in sheet or web format from one certain plastic film material that was biaxially stretched only to such an extent during its production that it still had a sufficient Degree of elongation and elongation for that required in its application for the stated purpose further stretching remains.

The subject of the invention is thus a stretchable, indentable, canisable adhesive film in sheet or web form, in particular for splicing the inner core of radial tires in the production of redfen, characterized in that it is made of a thin film of an olyolefin with crystalline components which was only weakly biaxially stretched during production, dig carrier and a thin adhesive layer attached to one side of natural and / or synthetic rubber,

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which optionally additionally contains small amounts of tackifier resins and / or anti-aging agents.

The term: "weakly biaxially stretched" is a Understood biaxial stretching of the film, which is well below the yield point.

The carrier preferably consists (thin film made of a polyolefin with crystalline or crystallizable parts) made of low-pressure polyethylene or isotactic polypropylene.

Such films are usually blown extrusion processes manufactured. But flat extrusion with a downstream one or two-stage stretching process also delivers for films suitable for this purpose. It is important that the Reokunip; the slide is carried out in the way leave it in no direction to a complete alignment of the chain molecules leads. The tension-elongation diagram (according to DIN 534-55) of such a film has that shown in Figure 1 of the drawing Course on.

Typical values both in the longitudinal and in the transverse direction for a 20 / am thick film (stretching speed: 100 mm / min) are as follows:

F ₀ = force at yield tension: 3-6 N / cm F _R = tear force: 5-10 N / cm

AL _c = change in length with stretching force: 4 - 8% C Lg "= change in length with tensile force: 400 - 800 %

These values are based on the special requirements of the relief check process and can therefore be used in varies over a larger area; will.

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The adhesive layer of the adhesive film according to the invention is due to the required compatibility with the Tire mixture made from adhesives (adhesive masses) based on natural and / or synthetic rubber. If necessary, they can additionally small proportions (up to about 20% by weight, based on the total composition of the solvent-free adhesive) compatible adhesive resins, e.g. hydrocarbon resins, and / or (up to a maximum of 5% »based on the total composition the solvent-free adhesive) of anti-aging agents, (in particular the usual blocked phenol or Types of cresol) included. The adhesive layer preferably consists of pure natural rubber of high molecular weight (K value: £ i50). However, it can also be made from a synthetic rubber (e.g. Polyisobutylene, butadiene-styrene rubber, butyl rubber or Like.) or consist of a mixture of natural and synthetic rubber.

The adhesive layer is usually obtained by that the adhesive is in the form of a solution in a volatile organic solvent or solvent mixture by means of a suitable application device (doctor blade, roller application) Carried in a thin layer on the carrier material and then on this in a heated drying tunnel is dried.

Because of the inherent tack of the raw rubber mixture of the In the tire, the layer thickness of the adhesive layer in the adhesive film according to the invention can be very low. It amounts to

preferably about 1 g / m. This value represents, but by no means represents a limit value, rather the layer thickness of the adhesive layer can also be selected to be greater without disadvantage.

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To improve the adhesion of the adhesive layer to the carrier film, this can be done by corona discharge or a corresponding one Process be pretreated and / or additionally a primer made of, for example, rubber crosslinked with isocyanates or an ethylene-vinyl acetate copolymer.

In Figure 2 of the drawing, which shows the adhesive film according to the invention in section at right angles to the longitudinal direction, is the Structure of the adhesive film shown schematically, which is excellently suited for the specified special purpose. Included 1 denotes the carrier film made of a crystalline polyolefin or crystallizable parts that were only weakly biaxially stretched during production and therefore still has a reserve of stretchability and 2 the adhesive layer Made of natural and / or synthetic rubber, which may also contain small amounts of adhesive resins and / or May contain anti-aging agents.

The production and use of the adhesive film according to the invention is explained in the following example:

example

A 20 / am thick low-pressure polyethylene film with high crystalline portion (so-called HM film) was measured by means of a Coater with 50 g / m 2 of a 2% ·. Solution of Natural rubber (K value: 150) in a gasoline-toluene mixture (90:10) coated. After evaporation of the solvent mixture in a gradually heated dry kana] one remained

weakly adhesive layer with a layer thickness of about 1 g / m 2. The film coated in this way was made into strips 30 cm wide cut and wound into rolls.

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Because of the relatively low tack of the adhesive layer In the case of the adhesive film according to the invention, the otherwise required adhesive strips wound into a roll are generally unnecessary adhesive-repellent back coating.

Matching sections of the adhesive film thus obtained were stretched over the attachment point of the inner layer of a Tire green glued and this processed in the usual way.

The adhesive film stuck during the subsequent crowning process firm and did not interfere with the vulcanization process, so that it did not need to be pressed down again, had to be removed before vulcanization.

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Claims (5)

2tf28673 Claims Llstretchable, vulcanizable adhesive film in sheet or Web shape, in particular for splicing the inner core of radial tires in tire manufacture, characterized that it consists of a thin film made of a polyolefin with crystalline components that are only used in the manufacture was weakly biaxially stretched, as a carrier and a thin layer of adhesive applied on one side There is natural and / or synthetic rubber, which may also contain small amounts of adhesive resins and / or Contains anti-aging agents. 2. Adhesive film according to claim 1, characterized in that the carrier consists of low-pressure polyethylene or this in contains substantial shares. 3. Adhesive film according to claim 1, characterized in that the Carrier made of isotactic polypropylene or this contains in substantial proportions. 4. Adhesive film according to claims 1 to. 3, characterized in that that the carrier film has a thickness of 5 to 50 μm, preferably between 10 and 30 μm. 5. Adhesive film according to claims 1 to 4, characterized in that the adhesive layer consists of 95 to 100 wt .-% Natural and / or synthetic rubber and 0 to 5 Contains% by weight of a conventional anti-aging agent. - 2 909881/0452 ORIGINAL INSPECTED