EP0931128B1 - Use of polyol-based lubricant for cutting elastomers - Google Patents

Abstract

The invention concerns lubricating coolants which are based on polyols and non-ionic emulsifiers and water and are suitable for lubricating/cooling during the cutting of elastomers. Their use prevents overheating of the cut elastomers and of the cutting tool. Furthermore, the resultant cut surface is suitable for further bonding, without requiring any further pre-treatment, in particular when high tensile strength or combined tension and shear resistance are required for the further bonding process, such as in the direct fitting of motor vehicle windows, for example.

Description

The present invention relates to the use of a lubricant based on water Solutions and / or emulsions of polyether polyols when cutting of cured elastomers.

The cutting of elastomers with a variety of tools comes across because of the rubber-elastic behavior of these polymeric compositions again and again technical difficulties. In modern automotive engineering, the fixed disks are glued directly to the body today. This is usually done using an elastomeric adhesive / sealant used, in most cases based on polyurethane elastomers. in the In the event of a repair, these directly bonded car windows must be used with the help of various Tools are cut out of the frame. Various exist for this Methods, e.g. Cutting wire, knives but also electric or pneumatic operated Vibration or vibration meter. Knives of this type are described, for example, in DE-A-3838044 described.

When using such vibrating knives, a lot of frictional heat is generated, so that it Decomposition reactions occur after a very short cutting time, which is immediately important smoke can be observed. This heat is both out occupational hygiene concerns as well as technical reasons. The occupational hygiene or health concerns are based on the development of Flue gases, the chemical composition of which is seldom exactly known, since they both from the composition of the elastomer as well as from the acute prevailing Decomposition temperature is dependent. The processor usually has his head relative close to the place of smoke or gas development, so it almost inevitably occurs Inhale the vapors. There are usually no occupational health and safety measures and are also difficult to put into practice.

The technical concerns are due to the poor controllability of the Guide the knife under these conditions, but also that the knife is light be baked out until "annealing". This strong thermal stress Knives result in very short downtimes for these knives. In addition, the strong thermal stress on the elastomer in the cutting area to strong chemical Degradation reactions of the polymer lead to the consequence that the chemical and physico-mechanical nature of the elastomer is greatly changed. This Change leads to considerable problems with the re-bondability.

• Kühlen des Schnittbereiches mit Lösungsmitteln, speziell mit Benzinen. Diese Methode verbietet sich bereits aus arbeitshygienischen Erwägungen. Neben der gesundheitlichen Problematik der Exposition der Verarbeiter mit Lösungsmitteldämpfen besteht hier auch ein andauerndes Verpuffungsrisiko wegen der entstehenden Lösungsmitteldampf-/Luftgemische. Letztere können sich sowohl an heiß gewordenen Schneidwerkzeugteilen als auch an den elektrischen Funken bei elektrisch betriebenen Schneidwerkzeugen entzünden.
• Die Kühlung/Schmierung des Schneidebereiches lässt sich mit Wasser nicht durchführen.
• Abkühlung des Schneidebereiches über Wartepausen. Hierbei wird ein kurzer Bereich geschnitten, bis es zur Rauchentwicklung kommt, dann wird die Klinge gekühlt. Dieses Verfahren ist sehr zeitaufwendig und wird alleine aus diesem Grunde kaum angewendet.
• Ein Anbieter von Schneidwerkzeugen empfiehlt nicht nur, sondern schreibt sogar die Verwendung eines Babyshampoos vor, um die Reibung im Schnittbereich herabzusetzen. Dazu wird eine Lösung dieses Shampoos in Wasser auf die Kleberaupe gesprüht und dann geschnitten. Zum Einsprühen der Kleberaupe einer Automobilfrontscheibe werden etwa 150 bis 200 ml dieser Detergenzlösung benötigt. Dieses Verfahren verhindert zwar die Wärmeentwicklung im Schneidebereich der Klebstoffraupe, da jedoch unweigerlich Detergentienreste auf der Schnittfläche verbleiben, wird durch dieses Verfahren ein sehr negativer Einfluss auf die Wiederverkiebbarkeit der Restraupe ausgeübt.

In order to avoid the above-mentioned problems, several approaches have so far been unsatisfactory in practice:

• Cooling the cutting area with solvents, especially with petrol. This method is out of the question for occupational hygiene reasons. In addition to the health problems associated with the exposure of processors to solvent vapors, there is also an ongoing risk of deflagration due to the resulting solvent vapor / air mixtures. The latter can ignite both on hot cutting tool parts and on the electrical sparks in electrically operated cutting tools.
• The cutting area cannot be cooled / lubricated with water.
• Cooling of the cutting area via waiting breaks. Here a short area is cut until smoke develops, then the blade is cooled. This process is very time-consuming and is rarely used for this reason alone.
• A supplier of cutting tools not only recommends, but even prescribes the use of a baby shampoo to reduce friction in the cutting area. A solution of this shampoo in water is sprayed onto the adhesive bead and then cut. About 150 to 200 ml of this detergent solution are required to spray the adhesive bead on an automobile windscreen. Although this process prevents the development of heat in the cutting area of the adhesive bead, however, since detergent residues inevitably remain on the cut surface, this procedure exerts a very negative influence on the resuscibility of the residual bead.

In all cases where the cut surface of the elastomer in a renewed The latter method cannot include the bonding process be used, because of the residues remaining on the cut surface Holding force of the adhesive after re-gluing to very low strength values sinks.

US-A-5,476,411 discloses a composition containing glycerin, Polyethylene glycols and alkyl polyglycoside and their use as a liquid auxiliary for wet grinding processes. According to the teaching of this document, those disclosed there are suitable Compositions for wet grinding of plastics and / or dried or cross-linked coatings of varnishes to achieve a smooth surface. additionally these compositions still contain finely divided abrasive particles, which in the Liquid are suspended. It is also proposed that this Compositions in water can be rinsed off the treated surface or should before further finish treatments can be carried out.

US-A-4128452 describes a knife for separating adhesively bonded Materials, especially self-adhesive labels. This knife has the Blade in a scabbard that has an inner lining made of absorbent material contains. A lubricant such as Silicone oil is even on the absorbent material of the vagina distributed. When the blade is inserted into the vagina being pulled out or pulled out of it, a thin layer of lubricant will be on all Spread surfaces of the blade. This enables an almost smooth contact between the blade and the material to be separated. Thereby the Lubricant prevent the stickiness of the cut adhesive.

The object was therefore to provide a lubricant and coolant which makes it possible to cut elastomers without developing a lot of frictional heat, the cut surfaces produced in this way being intended to remain suitable for a renewed bonding process of the elastomer parts. This is of particular importance in the case of repair of directly bonded car windows, since a so-called "residual bead", ie an adhesive layer of different thickness, remains on the car body when replacing car windows that have become defective. The adhesive for a pane to be newly glued is then applied directly to this cut surface, or the cut surface serves as a contact surface for the adhesive applied to the newly inserted pane. Since a bonded car window, in particular the windshield and rear window, is an integral part of the strength and rigidity of a car body, the car manufacturers stipulate minimum tensile shear strengths for such bonds in their specifications, which are generally at least 3 N / mm ² . As a rule, more than 5 N / mm ^{2 is} achieved with standard adhesives. These values must also be achieved with re-gluing.

It has now been found that when using lubricants based on aqueous solutions and / or emulsions of polyether polyols all the disadvantages of the previous applied methods are avoided. This method allows quick and safe re-gluing of car windows and is toxic and hygienic harmless. Lubrication through the polyether polyol and cooling of the blade through the The water content is very good and has been proven by numerous internal practical tests. The The remainder bead can be re-glued, whereby at least 85% of the specified adhesive shear strength can be achieved. With these values achieved the values for the first wrapping specified by all car manufacturers. In principle, countless polyether polyols can be used for the lubricants according to the invention. Polyether polyols based on linear or branched are particularly preferred Polyethylene glycols, polypropylene glycols or their copolymers. The molecular weight or the OH number and the viscosity of the polyetherols can vary widely Limits vary. Preferred ranges for the OH number are 500 to 15 mg KOH / g, whole OH numbers of 50 to 20 mg KOH / g are particularly preferred. The viscosity of such Polyether polyols at 25 ° C are between 500 mPa.s and 3000 mPa.s. The determination the OH number is according to DIN 53240, the viscosity according to DIN 51550. In support of Miscibility with water or to ensure a stable emulsion Mixtures of high and low molecular weight polyether polyols as well as minor additions of Surfactants or emulsifiers can also be used. This is usually nonionic surfactants used individually or in mixtures, preferably contain at least 2 OH groups per molecule. Those are very particularly preferred Alkyl polyglycosides, e.g. are manufactured and distributed by Henkel. To increase the storage stability, the lubricant according to the invention per se known and common preservatives can be added.

For the actual application as a lubricant / coolant, it is sufficient if in the towards cutting adhesive bead or elastomer bead sprayed solution about 2% by weight Polyether polyol are present. For more effective transport from the place of manufacture to Place of use and for better storage, however, it is advisable to first To produce a concentrate that the end user can easily dilute with water.

• 15 bis 40 Gew.% Polyetherpolyol, ggf. bestehend aus einer Mischung mehrerer Polyetherpolyole
• 0,1 bis 3 Gew.% nichtionische Tenside, vorzugsweise Alkylpolyglycoside
• 0,05 bis 0,5 Gew.% Konservierungsmittel
• 56,5 bis 84,85 Gew.% demineralisiertes Wasser.

A typical composition according to the invention of the concentrate for the lubricant / coolant thus contains:

• 15 to 40% by weight polyether polyol, possibly consisting of a mixture of several polyether polyols
• 0.1 to 3% by weight of nonionic surfactants, preferably alkyl polyglycosides
• 0.05 to 0.5% by weight preservative
• 56.5 to 84.85% by weight of demineralized water.

The possibility of diluting such a concentrate for the actual one Application depends on the concentration of polyether polyol in the concentrate, it lies between about 1: 8 to 1:20.

The invention is described below on the basis of a particularly preferred one Embodiment explained in more detail.

example 1

A lubricant concentrate was produced from the following constituents: 29% by weight polyether polyol (Lupranol 2040 from BASF, hydroxyl number approx. 28 mg KOH / g), 0.8% by weight alkyl polyglycoside from Henkel, 0.2% by weight % Acticid SPX, from Thorchemie, 70% by weight demineralized water.
The polyol and the surfactant were introduced and water was slowly added with a dissolver while stirring vigorously. It is particularly important to achieve particularly intensive mixing in the highly viscous phase so that a stable emulsion with finely dispersed polyol droplets is created.

Example 2

In a practical test, the lubricant was used according to Example 1 for the actual Application 1:15 diluted with water and this liquid on the adhesive bead one glazed car windscreen sprayed. The cured bead of adhesive was able to can be cut using a commercially available vibration knife without generating heat.

Example 3, comparative example

To determine the tensile shear strength during re-bonding, Primer pretreatment glass strips with the dimensions 25x100x4mm and painted Steel sheets 25x100x1mm using an adhesive bead consisting of the one-component moisture-curing direct glazing adhesive Terostat 8597 from Teroson glued so that a layer thickness of 5mm was created. The production of these test specimens and the tensile shear strength was determined in accordance with DIN EN 1465. Such an adhesive bond (here called original adhesive bond) is achieved after final curing According to the manufacturer, a tensile shear strength of 5 to 6 MPa.

To simulate glazing, the accessible, perpendicular to the cut surface were Surfaces of the cured adhesive bead on the one hand with the lubricant / coolant according to the invention sprayed and for comparison a according to the Tool manufacturer made solution of a baby shampoo with water on the Glue bead sprayed and the test specimens cut accordingly. For re-gluing new glass strips were taken, which were pre-cleaned with the primer Terostat 8510 from Teroson were pretreated. On the vented according to the manufacturer's instructions An appropriate amount of Terostat 8597 was applied to the primer surface. thereupon were the sheet metal strips from the cutting tests, on which the no further pretreated residual bead was used to simulate re-bonding, see above that again an adhesive joint with 5mm layer thickness was created.

In the case of the test specimens which contained residual beads which were cut using the lubricant / coolant according to the invention, more than 5 N / mm ^{2 were} achieved in each case after the final strength of the adhesive bond had been reached. The tensile shear test gave strength values below 1 N / mm ² for the test specimens containing residual beads which were cut using the baby shampoo.

It is clear from this that when using a recommended lubricant / coolant according to the prior art, there is a clear safety risk with regard to the tensile shear strength of the re-adhesion, while when using the lubricant / coolant according to the invention, re-adhesion values are achieved which are well above those required by the automakers Minimum values of 3 N / mm ² are.

Claims (7)

1. The use of a composition based on aqueous solutions and / or emulsions of polyether polyols as lubricant for lubricating and cooling in the cutting of cured elastomeric adhesive/sealant joints or of cured elastomeric moldings or profiles.
2. The use as claimed in claim 1, characterized in that the lubricant contains water, at least one polyether polyol, one or more nonionic surfactant(s) and optionally preservatives.
3. The use as claimed in any of the preceding claims, characterized in that the polyether polyol is selected from the group consisting of linear or branched polyethylene glycols, polypropylene glycols or copolymers thereof.
4. The use as claimed in claim 3, characterized in that the polyol has an OH value of 500 to 15 mg KOH/g (DIN 53240) and preferably 50 to 20 mg KOH/g and a viscosity at 25°C of 500 mPa.s to 3,000 mPa.s (DIN 51550).
5. The use as claimed in any of claims 2 to 4, characterized in that the surfactant(s) contain(s) at least 2 OH groups.
6. The use as claimed in claim 5, characterized in that the surfactant( s ) is/are an alkyl polyglycoside.
7. A process for cutting cured elastomeric adhesive/sealant joints or elastomeric moldings, characterized by the following steps:

   spraying or coating of the areas of the elastomer to be cut with the lubricant claimed in claims 1 to 6,

   cutting of the elastomer with a vibrating or oscillating knife or a cutting wire,

   optionally flexible rebonding on at least one of the cut surfaces.