DE102019201025A1 - Adhesive tape with temporary fixing adhesive - Google Patents

Abstract

A temporary fixation adhesive for a first temporary fixation of two substrates to one another as a preliminary stage of a second final fixation of the two substrates, the second final fixation being carried out by means of a final fixation adhesive and this final fixation adhesive the temporary fixation adhesive in the course of the second final fixation, the temporary fixation adhesive being a pressure-sensitive adhesive which contains the following:
a) at least one polymer
b) optionally at least one adhesive resin
c) at least one solid reactive resin
d) optionally further reactive resins, the temporary fixing adhesive containing at least 185 parts of the at least one solid reactive resin per 100 parts of polymer and adhesive resin,
is a very good temporary fixing adhesive that is soluble in the final fixing adhesive, which has good pressure-sensitive tack and can also be produced solvent-free.

Description

The present invention relates to a temporary fixing adhesive for a first temporary fixing of two substrates to one another as a preliminary stage of a second final fixing of the two substrates, the second final fixing being carried out by means of a final fixing adhesive and this final fixing adhesive the temporary -Fixier adhesive in the course of the second final fixation, an adhesive tape containing this adhesive, a process for producing this adhesive and the use of this adhesive and this adhesive tape.

Fiber-reinforced epoxy resins have numerous areas of application. They are used in the automotive industry, boat building, aircraft construction or in the manufacture of rotor blades for wind turbines. When producing rotor blades for wind turbines, many layers of glass fiber mats are laid out in the desired shape over a large area. In a so-called vacuum infusion process, epoxy resins are then sucked in (process names: vacuum-assisted resin transfer molding (VARTM), vacuum infusion). This is in the shown. In order to prevent the glass fiber mats from shifting or wrinkling in this process, which is a problem, the larger the glass fiber mats are, it is desirable to temporarily hold the glass fiber mats in the desired position. To do this, they are either glued to the edges or spray adhesives are used. The edge bonding is complex and prone to errors when fixing the mats. Since the mats are only fixed at their edges, the mats can warp in more internal areas of the mold, which have a negative impact on the product. The application of spray adhesives is also time-consuming and prone to errors because the metering of the adhesive is the responsibility of the applicator. A uniform layer thickness of the adhesive layer can therefore not be guaranteed. In addition, spray adhesives contain large amounts of solvents, some of which are harmful or irritating to health, such as styrene or butanone, which have to evaporate before bonding. Since a foreign material is introduced into the composite via the spray adhesive, the performance of the cured fiberglass-epoxy composite is also somewhat worse than that of the pure epoxy composite without the addition of a spray adhesive. Pressure sensitive adhesive tapes would be easier to apply, but foreign materials would remain in the composite, as with spray adhesive, so that the performance of the component would also be poorer.

From the EP 2 229 421 B1 are known fiber mats coated with adhesive, so-called "prepregs"("preimpregnatedfibers"), which are used for the production of fiber-reinforced epoxies. The essence of the invention is that the adhesive is partially crosslinked, partial esters of an epoxy resin being reacted with an unsaturated carboxylic acid and partially crosslinked. The adhesive is swellable and / or soluble in the epoxy resins of the infusion process.

Prepregs, their manufacture and use are in the WO 2013/107829 A1 described in detail. These are textile fabrics that are impregnated with a reactive resin. The reactive resins are generally gelled to ensure storage and transportability, i.e. the hardening reaction is initiated and stopped at an early stage (so-called B state). A clear increase in the viscosity of the resin occurs, which makes the impregnated structure manageable. Prepregs of this type are tacky and can therefore be laminated together at room temperature. Like adhesive tapes, they are usually covered with release liners to make them stackable or windable. A disadvantage of this prior art is that the gelled prepregs have to be stored in a refrigerated state in order to prevent the curing reaction from continuing.

The EP 2 229 421 B1 solves the problem of the short shelf life of prepregs in the B state by providing a semi-finished textile that is equipped with a pressure sensitive adhesive. This is partially networked via a radical process. The pressure sensitive adhesive is used on a textile backing for bonding. In the finished component, both the textile fabric and the partially crosslinked polymer remain at the bonded point, which generates inhomogeneities in the crosslinking density.

The WO 2012/026980 A2 describes the use of pressure sensitive adhesive spray adhesives to influence the flow behavior of the epoxy resin drawn into the VARTM. Examples include the commercially available adhesives NuTack ^® E, NuTack ^® Blu, NidaTack ^® NT and 3M ™ Super 77 ™. These spray adhesives reduce the interlaminar shear strength of fiber composites by more than 8%.

The WO 1997/003828 A1 describes fiber-reinforced foams. As described therein, the foam can, for example, be provided with a pressure sensitive adhesive in order to fix the fiber mats. Problematic is that the pressure sensitive adhesive remains in the cured component as a disruptive factor because it negatively influences its strength.

That's why the WO 2013/060588 A1 intend to use thermoplastic adhesives for the temporary fixation of the fiber mats which have the same or a chemically similar resin as the resin used for the VARTM process. Unsaturated polyester are advantageous. and vinyl ester resins are described, which are then dissolved by styrene-containing resins in the VARTM.

Crosslinkable adhesives based on epoxides are used in the WO 2013/060588 A1 described as disadvantageous, since these tend to form a substructure, which have a negative effect on the properties of the laminate. For high-quality components, however, epoxy resins are preferred in the VARTM.

A central disadvantage in the current state of the art is the complex fixing of the fiber mats with adhesives on the edge or spray adhesives. Pressure-sensitive adhesives for fixing foams, for example, on fiber mats are generally described in such infusion processes. However, these foreign substances remaining in the material cause performance losses that cannot be tolerated in demanding industries such as aerospace or the manufacture of rotor blades. A liquid adhesive becomes tacky if it has a certain cohesion. In the prior art, the increase in cohesion is achieved, for example, with textile fabrics and / or by UV-induced pre-crosslinking ( EP 2 229 421 B1 ) or through the use of thermoplastic adhesives ( WO 2013/060588 A1 ) that are sticky only at elevated temperatures.

In order to temporarily fix fiber structures in epoxy composite production without having a relevant negative impact on the performance of the cured components, the DE 10 2015 208 320 A1 described that adhesive strips made of a pressure-sensitive adhesive that dissolve in the resin are used for the temporary fixation of fiber structures in composite production. In this way, the problem is avoided that the remaining foreign substances (adhesive) in the resin have to accept a loss in stability. In the DE 10 2015 208 320 A1 liquid epoxy resins are used. The production must be solvent-based. This brings with it the usual problems of solvent-based manufacturing processes.

The object of the present invention was therefore to produce temporary fixing adhesives which have good pressure-sensitive adhesiveness, dissolve well in the final fixing adhesive and can be produced without solvents.

This object is achieved according to the invention by a temporary fixing adhesive as described in the independent claim. The subclaims relate to advantageous developments of the subject matter of the invention. Furthermore, the invention comprises a method for producing the adhesive, an adhesive tape containing the adhesive and the use of adhesive and adhesive tape.

1. a) mindestens ein Polymer
2. b) optional mindestens ein Klebharz
3. c) mindestens ein festes Reaktivharz
4. d) optional weitere Reaktivharze,

wobei der Temporär-Fixier-Klebstoff auf 100 Teile Polymer und Klebharz mindestens 185 Teile des mindestens einen festen Reaktivharzes enthält.Accordingly, the invention relates to a temporary fixing adhesive of the type mentioned at the outset, the temporary fixing adhesive being a pressure-sensitive adhesive which contains the following:

1. a) at least one polymer
2. b) optionally at least one adhesive resin
3. c) at least one solid reactive resin
4. d) optionally further reactive resins,

wherein the temporary fixing adhesive contains at least 185 parts of the at least one solid reactive resin per 100 parts of polymer and adhesive resin.

The term “contains” is to be understood in the present application in such a way that the list of possible components is not exhaustive. In addition to the components a) to d) mentioned, other compounds can also be contained in the temporary fixing adhesive.

Information on properties such as “tacky”, “solid” or “liquid” in the present invention is always based on the property at room temperature, unless explicitly stated otherwise.

Surprisingly, it was found in the context of the present invention that when using at least 185 parts of solid reactive resin per 100 parts of polymer and adhesive resin, that is to say with a maximum of 35% polymer and adhesive resin in the temporary fixing adhesive, in view of the use of solid reactive resins Both good pressure-sensitive adhesives and adhesives that are soluble in the final fixing adhesive are obtained.

This is particularly surprising, since it would be expected that on the one hand solid reactive resins make the adhesives firmer and therefore less soluble, and on the other hand low polymer contents are good for solubility, but in combination with liquid reactive resins they give very soft adhesives without sufficient shear strength for the process become. A person skilled in the art would therefore not naturally choose such a combination.

For the purposes of this application, dissolving means that, according to the method for determining the solubility described in the method part, the temporary fixing adhesive at least partially dissolves in the final fixing adhesive. An adhesive that only detaches from the carrier and visually floats around in the final fixing adhesive did not meet this definition.

The maximum of 35% polymer / adhesive resin relates to the sum of the two components. If there is no adhesive resin, up to 35% polymer can be included. Based on the parts specified, the phrase “at least 185 parts of solid reactive resin per 100 parts of polymer and adhesive resin” means that at least 185 g of solid reactive resin are used per 100 g of polymer and / or adhesive resin. If adhesive resin is also included, the parts of polymer and adhesive resin are combined. If more than one reactive resin is used, the information relates to the sum of the parts by weight of the reactive resins, if more than one polymer is used, to the sum of the parts by weight of the polymers used, plus the amount of the adhesive resin or the sum of the Parts by weight of the adhesive resins used.

Pressure-sensitive adhesives are adhesives that allow a permanent connection to the adhesive base even under relatively weak pressure and can be removed from the adhesive base after use, essentially without residue. Pressure-sensitive adhesives are permanently pressure-sensitive at room temperature, that is to say they have a sufficiently low viscosity and a high degree of tack, so that they wet the surface of the respective adhesive base even with slight pressure. The adhesiveness of corresponding adhesives is based on their adhesive properties and the releasability on their cohesive properties.

By using the temporary fixing adhesive according to the invention, it can be ensured that the deviation in the interlaminar apparent shear strength (ILSS) of a component using the resulting final fixing adhesive / temporary fixing adhesive mixture from that of a component using of the final fixation adhesive deviates only slightly if at all, since the mixture largely has the same properties as the final fixation adhesive in its pure form. The ILSS is a measure of the material's resistance to shear forces that affect the cohesion between the individual material layers. For the purposes of the present invention, the deviation in the interlaminar apparent shear strength of the resulting final fixing adhesive / temporary fixing adhesive mixture from that of the pure final fixing adhesive is less than 5%. The deviation is particularly preferably less than 3%.

The temporary fixing adhesive is advantageously produced from components a) to d) in a solvent-free manner. If, in addition to components a) to d), further components are added, this preferably also applies to these further components. Solvent-free production is preferable from an environmental and health perspective. In addition, the step of removing the solvent is eliminated, which leads to a reduction in production time and costs.

The further reactive resin is advantageously a liquid reactive resin with a viscosity <1,000 Pa · s. With such additional liquid reactive resins, the viscosity of the product can advantageously be adjusted, so that application from the melt, which can take place, for example, by means of a spray nozzle, is particularly simple.

An epoxy resin is preferably used as the solid reactive resin. If liquid reactive resins are also used, these are also preferably epoxy resins. Epoxy resins are used in VARTM. On the one hand, the same (reactive resin) dissolves more easily in the same, on the other hand the influence becomes the interlaminar shear strength is kept particularly low, since the dissolved epoxides from the temporary fixing adhesive also cross-link and are therefore not a disruptive factor. At least one epoxy resin based on bisphenol-A, bisphenol-S, bisphenol-F, an epoxy novolak, an epoxy cresol novolak or an epoxidized nitrile rubber is particularly preferred as the reactive resin.

The final fixing adhesive is particularly preferably based on at least one epoxy resin, and the temporary fixing adhesive contains the same reactive resin class as the reactive resin of the final fixing adhesive.

At least one epoxy resin based on bisphenol-A, bisphenol-S, bisphenol-F, an epoxy novolak, an epoxy cresol novolak or an epoxidized nitrile rubber is also particularly preferred as reactive resin for the final fixing adhesive.

“On the basis of” or “on the basis of” in the present case means that the properties of the adhesive are at least strongly determined by the basic properties of this component (the so-called “base resin”), although it is of course not excluded that this can be caused by use by modifying auxiliaries or additives or by other polymers in the composition are additionally influenced. In particular, this can mean that the proportion of the base resin in the total mass of the adhesive is more than 50% by weight.

The polymer can be a polymer, but can also be a mixture of two or more different polymers. The at least one polymer can in particular be an elastomer or a thermoplastic.

Examples of polymers are elastomers as are usually used in the field of pressure sensitive adhesives, as are described, for example, in the “Handbook of Pressure Sensitive Adhesive Technology” by Donatas Satas (Satas & Associates, Warwick 1999).

These are, for example, elastomers based on acrylates and / or methacrylates, polyurethanes, natural rubbers, synthetic rubbers such as butyl, (iso) butyl, nitrile or butadiene rubbers, styrene block copolymers with an elastomer block made from unsaturated or partially or fully hydrogenated polydiene blocks (polybutadiene, Polyisoprene, poly (iso) butylene, copolymers of these and other elastomer blocks known to those skilled in the art), polyolefins, fluoropolymers and / or silicones.

Particularly advantageous polymers are poly (amides), polyurethanes, nitrile butadiene rubbers, poly (ureas), poly (ether ether ketone) (PEEK), poly (sulfone) (PSU) and poly (ether sulfone) (PES). These enable pressure-sensitive adhesives with very high proportions of reactive resin, which is particularly advantageous for the finished components, since the proportion of non-crosslinking polymers is particularly low. Nitrile rubbers are particularly suitable for the present invention. Those nitrile rubbers which contain more than 15%, in particular more than 25%, acrylonitrile are particularly preferred.

Any type of thermoplastics known to the person skilled in the art can also be used as the at least one polymer, as described, for example, in the textbooks “Chemistry and Physics of Synthetic Polymers” by J.M.G. Cowie (Vieweg, Braunschweig) and "Macromolecular Chemistry" by B. Tieke (VCH Weinheim, 1997) are mentioned. These are, for example, poly (ethylene), poly (propylene), poly (vinyl chloride), poly (styrene), poly (oxymethylene), poly (ethylene oxide), poly (ethylene terephthalate), poly (carbonate), poly (phenylene oxide), poly (urethane), poly (urea), acrylonitrile-butadiene-styrene (ABS), poly (amide) (PA), poly (lactate) (PLA), poly (etheretherketone) (PEEK), poly (sulfone) (PSU), Poly (ether sulfone) (PES). Poly (acrylates), poly (methacrylates) and poly (methyl methacrylates) (PMMA) are also possible as a polymer, but are not preferred for the purposes of the present invention.

The selection of the polymer component depends on the chosen epoxy system. If polar epoxides (often produced by the reaction of alcohols with epichlorohydrin, such as the reaction product of bisphenol-A and epichlorohydrin) are used, more polar polymers are particularly preferred. These include both elastomers such as acrylonitrile butadiene rubbers and thermoplastics such as poly (ethylene oxide), poly (ethylene terephthalate), poly (carbonates), poly (phenylene oxides), poly (urethanes), poly (ureas), poly (amides) (PA) ), Poly (lactate) (PLA), poly (ether ether ketone) (PEEK), poly (sulfone) (PSU), poly (ether sulfone) (PES).

For non-polar epoxides such as dicyclopentadiene diepoxide, non-polar polymers are preferred. These are, for example, poly (styrene), styrene block copolymers with an elastomer block made from unsaturated or partially or fully hydrogenated polydiene blocks (polybutadiene, polyisoprene, poly (iso) butylene, copolymers of these and other elastomer blocks known to the person skilled in the art) or thermoplastic polyolefins, fluoropolymers and / or Silicones.

In order to obtain temporary fixing adhesives with particularly high epoxy contents, all polymers that are not intrinsically pressure-sensitive are particularly suitable, ie they do not meet the Dahlquist criterion at room temperature (cf. J. Adhesion, 1991, vol. 34, pp. 189-200 or CA Dahlquist: Tack, adhesion, fundamentals and pra.ctice, McLaren and Sons Ltd., London, 1966 ). This applies both to the polymer component and to the mixture of polymer and adhesive resin, if such is used. Thus, although polymer and possibly adhesive resin are not pressure sensitive per se, the resulting temporary fixing adhesive is pressure sensitive.

The polymers of the polymer mixture can be of linear, branched, star-shaped or grafted structure, to give only a few examples, and can be constructed as a homopolymer, as a random copolymer, as an alternating or as a block copolymer. For the purposes of this invention, the term “statistical copolymer” includes not only those copolymers in which the comonomers used in the polymerization are incorporated purely statistically, but also those in which gradients in the comonomer composition and / or local enrichments of individual comonomer types occur in the polymer chains . Individual polymer blocks can be constructed as a copolymer block (random or alternating).

Adhesive resins can be used for the present invention, but an adhesive resin is unnecessary for the temporary fixing adhesives of the present invention. The desired pressure-sensitive tack of the adhesive is achieved even without the addition of adhesive resin. Since it is desired that the temporary fixing adhesive is chemically as similar as possible to the final fixing adhesive and the latter usually does not contain any adhesive resins, it is preferred that the temporary fixing adhesive contains no adhesive resins.

In principle, all reactive constituents known to the person skilled in the field of pressure-sensitive adhesives or reactive adhesives and forming macromolecules which crosslink in a build-up reaction can be used as reactive resins, as described, for example, in Gerd habenicht: gluing - basics, technologies , Applications, 6th edition, Springer, 2009.

The structure and the chemical nature of the crosslinkable component are not critical, as long as the structure reaction can be carried out under conditions, in particular with regard to the temperatures used, the type of catalysts used and the like, which do not lead to any significant impairment and / or decomposition of the polymer phase, whereby they are preferably at least partially miscible with the elastomer phase.

Epoxy-containing materials or epoxy resins that are useful in the compositions of the invention are any organic compounds having at least one oxirane ring that are polymerizable by a ring opening reaction. Such materials, commonly referred to as epoxies, include both monomeric and polymeric epoxies and can be aliphatic, cycloaliphatic, or aromatic. These materials generally have on average at least two epoxy groups per molecule, preferably more than two epoxy groups per molecule. The “average” number of epoxy groups per molecule is defined as the number of epoxy groups in the epoxy-containing material divided by the total number of epoxy molecules present. The polymeric epoxides include linear polymers with terminal epoxy groups (e.g. a diglycidyl ether of a polyoxyalkylene glycol), polymers with skeletal oxirane units (e.g. polybutadiene polyepoxide) and polymers with epoxy side groups (e.g. a glycidyl methacrylate polymer or copolymer). The molecular weight of the epoxy-containing material can vary from 58 to about 100,000 g / mol or more. Mixtures of various epoxy-containing materials can also be used in the hot melt compositions of the invention. Useful epoxy-containing materials include those that contain cyclohexene oxide groups, such as the epoxycyclo-hexane carboxylates, that are generated by 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate, 3,4-epoxy-2-methylcyclohexylmethyl-3,4-epoxy-2-methylcyclohexane carboxylate, and bis (3,4-epoxy-6-methylcyclohexylmethyl) adipate are included. For a more detailed list of useful epoxides of this type see U.S. Patent No. 3,117,099 to get expelled.

Other epoxy-containing materials that are particularly useful in the practice of this invention include glycidyl ether monomers. Examples are the glycidyl ethers of polyhydric phenols, which are obtained by reacting a polyhydric phenol with an excess of chlorohydrin, such as epichlorohydrin (e.g. the Diglycidyl ether of 2,2-bis (2,3-epoxypropoxyphenol) propane) can be obtained. Further examples of epoxides of this type that can be used in the practice of this invention are shown in U.S. Patent No. 3,018,262 described.

There are a variety of commercially available epoxy containing materials that can be used in this invention. In particular, epoxies that are readily available include octadecylene oxide, epichlorohydrin, styrene oxide, vinyl cyclohexene oxide, glycidol, glycidyl methacrylate, diglycidyl ether of bisphenol A (for example, those available under the trade names EPON 828, EPON 1004 and EPON 1001F from Shell Chemical Co. and DER- 332 and DER-334 are available from Dow Chemical Co.), diglycidyl ether from bisphenol F (e.g. ARALDITE GY281 from Ciba-Geigy), vinyl cyclohexene dioxide (e.g. ERL 4206 from Union Carbide Corp.), 3,4-ep-oxycyclohexylmethyl- 3,4-epoxycyclohexene carboxylate (e.g. ERL-4221 from Union Carbide Corp.), 2- (3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy) cyclohexane metadioxane (e.g. ERL-4234 from Union Carbide Corp.), bis (3,4-epoxycyclohexyl) adipate (e.g. ERL-4299 from Union Carbide Corp.), dipentene dioxide (e.g. ERL-4269 from Union Carbide Corp.), epoxidized polybutadiene (e.g. OXIRON 2001 by FMC Corp.), epoxy functionality containing silicone resin, epoxysilanes ( for example beta (3,4-epoxycyclohexyl) ethyltrimethoxysilane and gamma-glycido-xypropyltrimethoxysilane, commercially available from Union Carbide), fire retardant epoxy resins (e.g. DER-542, a brominated bisphenol type epoxy resin available from Dow Chemical Co.), 1 , 4-butanediol diglycidyl ether (e.g. ARALDITE RD-2 from Ciba-Geigy), hydrogenated epoxy resins based on bisphenol A epichlorohydrin (e.g. EPONEX 1510 from Shell Chemical Co.) and polyglycidyl ether from phenol formaldehyde novolak (e.g. DEN-431 and DEN-438 from Dow Chemical Co.).

The reactive resin of the temporary fixing adhesive preferably has the same epoxy base as the final fixing adhesive. The more similar the Temporary Fixing Adhesive and the Final Fixing Adhesive are to one another, the smaller the deviations in the ILSS will be. “Similar” means that, for example, when using bisphenol-A based epoxides in the final fixation adhesive, reactive resins based on bisphenol-A are also used in the temporary fixation adhesive composition. These can be exactly the same or differ slightly in molecular weight.

The reactive resin of the temporary fixing adhesive is therefore particularly preferably the same as that of the final fixing adhesive.

The temporary fixing adhesive according to the invention can contain a hardener or initiator. However, this is not necessary because the final fix adhesive contains a hardener or initiator. However, as mentioned above, the temporary fixing adhesive is preferably hardener-free. The temporary fixing adhesive of the adhesive tape according to the invention can also contain an accelerator. As in the case of the hardener, however, this is also of only minor importance, since the setting of the crosslinking reaction of the reactive resin takes place via the final fixing adhesive.

The temporary fixation adhesive can optionally contain further additives, rheology modifiers, foaming agents, fillers or adhesion promoters.

A temporary fixing adhesive according to the invention is particularly suitable if the adhesive strength of the uncured adhesive on steel is at least 1 N / cm. This gives good pressure sensitive properties.

The invention further relates to an adhesive tape which contains the temporary fixing adhesive according to the invention. Packaging as adhesive tape is particularly suitable for the application. A very simple and precise metering of the adhesive is possible with an adhesive tape. Dosing is simplified compared to an adhesive, since a fixed amount is always applied and it does not depend on the skill and accuracy of the user which amount of adhesive is applied in which area.

The general term “adhesive tape” encompasses a backing material which is provided on one or both sides with an (adhesive) adhesive. The carrier is preferably made of the same or at least a very similar material as the fiber fabric of the composite material so that it does not change its properties. In order to minimize bumps as much as possible, the carrier should have the smallest possible thickness.

In particular, the term “adhesive tape” in the sense of the present invention includes so-called “transfer adhesive tapes”, that is to say an adhesive tape without a carrier. Such transfer adhesive tapes are particularly preferred according to the invention. In the case of a transfer adhesive tape, the adhesive is rather in front of the Application applied between flexible liners, which are provided with a separating layer and / or have anti-adhesive properties. For application, a liner is regularly removed first, the adhesive is applied and then the second liner is removed. The adhesive can be used directly to connect two surfaces. Such strapless transfer adhesive tapes are particularly preferred according to the invention. Such a pressure-sensitive, adhesive, strapless transfer adhesive tape according to the invention enables very precise bonding in terms of positioning and dosage.

Adhesive tapes are also possible in which the liner is not equipped with two liners but with a single liner that separates on both sides. The adhesive tape web is then covered on its upper side with one side of a liner equipped with double-sided separation, its underside with the back of the liner equipped with double-sided separation, in particular an adjacent turn on a bale or a roll.

As mentioned above, in the case of use in the production of composite materials in which the carrier remains in the composite, the carrier should be as similar as possible to or match the fiber material used. The lowest possible carrier thickness is preferred.

The thickness of the pressure sensitive adhesive, which is present either as transfer adhesive tape or coated on a flat structure, is preferably between 1 μm and 100 μm, more preferably between 5 μm and 50 μm and particularly preferably between approximately 10 μm and 30 μm.

For use in the manufacture of rotor blades, the preferred layer thickness is from 10 µm to 30 µm. The layer thickness is to be chosen the smaller the fewer epoxies are contained in the temporary fixing adhesive, since a lower epoxy content in the adhesive has a greater negative effect on the ILSS. If, on the other hand, the temporary fixation adhesive has a higher epoxy content, there is little or almost no negative influence on the ILSS and it is possible to use a thicker layer of the temporary fixation adhesive.

The invention also relates to the use of the temporary fixing adhesive according to the invention or the adhesive tape according to the invention for the temporary fixing of fiber structures in the production of composites. Typical areas of application are the automotive industry, aircraft and boat construction as well as rotors for wind turbines. Especially in the case of rotors for wind power plants, fiber mats of very large dimensions have to be temporarily fixed in a mold, which is very difficult since warping and unevenness can easily occur. The adhesive tape according to the invention enables a temporary fixation in a simple and inexpensive manner without this temporary fixation having any significant loss in the quality of the finished product.

The temporary fixing adhesive according to the invention or the adhesive tape according to the invention are particularly preferably used for the temporary fixing of fiber structures in vacuum resin infusion processes, the resin for the vacuum resin infusion process being selected from the group of epoxy resins. Epoxy resins are particularly advantageous for vacuum resin infusion processes because the prefabricated components using epoxy resins have particularly good properties with regard to the ILSS.

• - temporäres Fixieren der Fasergebilde in einer Form sowie untereinander mit dem erfindungsgemäßen Klebeband enthaltend einen Temporär-Fixier-Klebstoff;
• - Einfüllen des Final-Fixier-Klebstoffes unter Auflösen des Temporär-Fixier-Klebstoffes des Klebebandes im Final-Fixier-Klebstoff; und
• - Aushärten des Final-Fixier-Klebstoffes.

A method for producing a composite from fiber structures and a final fixing adhesive comprises the following steps:

• - Temporary fixing of the fiber structures in a mold and with each other with the adhesive tape according to the invention containing a temporary fixing adhesive;
• - Filling the final fixing adhesive while dissolving the temporary fixing adhesive of the adhesive tape in the final fixing adhesive; and
• - curing of the final fixing adhesive.

The final fixing adhesive is preferably filled in by a resin infusion process, which is also called a vacuum infusion process. Here, glass fiber mats are laid out in the desired shape over a large area and then epoxy resins are sucked in under vacuum.

Finally, the present invention relates to a method for producing the temporary fixing adhesive according to the invention, the at least one polymer a) being digested with the at least one solid reactive resin c) and the optional further components in an extruder, at least part of the amount, preferably the total amount of solid reactive resin to the polymer at the beginning of the Disclosure is added. A very homogeneous adhesive is obtained by adding the solid reactive resin at the beginning.

Alternatively, the temporary fixing adhesive according to the invention can also be produced by kneading. It is also advantageous here to add the solid reactive resin at the beginning of the process.

It is already advantageous if part of the solid reactive resin is added. The entire reactive resin is particularly advantageously added at the beginning.

Examples

Measurement methods

Solubility of PSAs in Final Fixing Adhesives

Epon Resin 828 from Momentive (bisphenol-A epichlorohydrin reaction product) was selected as the final fixing adhesive.

• ++: löst sich schnell, innerhalb der ersten 4 Stunden ist bereits optisch ein Auflösen zu beobachten, nach 24h sind auf dem PET keine Klebebandreste mehr vorhanden
• +: löst sich, nach 24h sind auf dem PET keine Klebebandreste mehr vorhanden
• -: quillt an, die Schichtdicke des Klebebandes hat zugenommen aber der PET-Träger ist noch vollständig mit Klebemasse bedeckt
• -- löst sich nicht, der PET-Träger ist noch vollständig mit Klebemasse bedeckt

In a 250 mL glass vessel, Epon Resin 828 was heated to 40 ° C ± 1 ° C with a magnetic stirrer. For the test, the PSA to be tested was laminated to etched PET and dissolved in the stirred Epon Resin 828 for 24 hours. The evaluation was made optically according to the following criteria:

• ++: dissolves quickly, within the first 4 hours a dissolving effect can already be observed, after 24 hours there are no adhesive residues left on the PET
• +: dissolves, after 24 hours there are no adhesive residues left on the PET
• -: swells, the layer thickness of the adhesive tape has increased but the PET carrier is still completely covered with adhesive
• - does not come off, the PET carrier is still completely covered with adhesive

Molecular weight:

The molecular weight determinations of the number average molecular weights M _n and the weight average molecular weights M _{w were} carried out by means of gel permeation chromatography (GPC). THF (tetrahydrofuran) with 0.1% by volume of trifluoroacetic acid was used as the eluent. The measurement was carried out at 25 ° C. PSS-SDV, 5 µ, 10 ³ Å, ID 8.0 mm x 50 mm was used as the guard column. The columns PSS-SDV, 5 µ, 10 ³ as well as 10 ⁵ and 10 ⁶ , each with an ID of 8.0 mm x 300 mm, were used for the separation. The sample concentration was 4 g / l, the flow rate 1.0 ml per minute. It was measured against polystyrene standards.

Interlaminar Apparent Shear Strength (ILSS):

The 100 kN servohydraulic test system from Inova was used to test the samples and an MGC Plus from HBM (Hottinger Baldwin Messtechnik) was used for data acquisition. The measurement rate was 20 Hz.

The test apparatus according to EN ISO 14130 was used for the tests. With this experimental set-up, the interlaminar apparent shear strength is determined. The structure is basically similar to that of the three-point bending test. However, very small samples are used to cause interlaminar failure. The pressure-sensitive fixing agents were compared with a reference (without fixing agent) and 2 competitor products (spray adhesive Aerofix 2 and 3M 11095). The samples have four layers of glass fiber and fixative was applied between each layer. The amount of spray adhesive was 10 to 15 g / m ² . The pressure-sensitive adhesives were between about 30 µm thick.

The sample plates were produced using VARTM (vacuum-assisted resin transfer molding). An 812 g / m ² biax scrim (batch number 1012299) from Saertex was used. The plates were laminated with the RIM 135 epoxy system from Momentive (batch number SG1CO197) and the hardener RIM137 (batch number SG1BO364) at 40 ° C and under an absolute pressure of 2 mbar. The samples were then cut and annealed in a tempering furnace for 10 hours at a temperature of 70 ° C.

Adhesive strength

The bond strengths were determined analogously to ISO 29862 (method 3) at 23 ° C. and 50% relative atmospheric humidity at a take-off speed of 300 mm / min and a take-off angle of 180 °. The thickness of the adhesive layer was approx. 30 µm in each case. An etched PET film with a thickness of 50 μm was used as the reinforcing film, as is available from Coveme (Italy).

Steel plates according to the standard were used as the substrate. The measuring strip was glued using a roller at a temperature of 23 ° C. The adhesive tapes were removed immediately after application.

Gel value determination

For this purpose, adhesive tape samples were punched out in pieces of 20 cm ² and welded into a bag made of spunbonded polyethylene (Tyvek from Du Pont with a basis weight of approx. 55 g / cm ² ). The samples were extracted with butanone for 3 days with shaking at room temperature. The butanone was changed daily. After extraction, the samples were dried at 110 ° C. The gel fraction was determined by differential weighing, taking into account the extraction losses of the spunbonded nonwoven and the carrier. From the difference between the sample weights before extraction and after extraction, the gel value is determined as a percentage of the weight fraction of the polymer that cannot be extracted with butanone.

The gel value is determined by Soxhlet extraction, which is used to extract soluble ingredients from polymers in continuous extraction. In the case of gel value determination of PSAs, the soluble fractions of a polymer - the so-called sol - are extracted from the insoluble fractions - the so-called gel - using a suitable solvent such as tetrahydrofuran. Preparation: The mass to be extracted is applied to siliconized release paper in a thin film - usually 120 µm layer thickness - and dried for approx. 12 h at 80 ° C (convection oven). The films are stored in the desiccator over drying agents. The 603 Whatman extraction tubes are dried for 12 hours at 80 ° C., the empty weight of the tubes is determined and stored in the desiccator until use.

Approx. 1 g of PSA is weighed into the extraction thimble. A 100 ml round-bottom flask of the Soxhlet apparatus is filled with 60 ml of tetrahydrofuran and heated to boiling. THF vapors rise through the steam pipe of the Soxhlet apparatus and condense in the cooler and THF drips into the extraction sleeve and extracts the sol portion. In the course of the extraction, the THF I with the extracted sol runs back into the flask. Dissolved sol increasingly accumulates in the flask. After 72 h of continuous extraction, the sol is completely dissolved in the THF. The extraction sleeve is then removed after the apparatus has cooled to room temperature and dried at 80 ° C. for 12 h. The tubes are kept in the desiccator until they are constant in weight and then weighed out.

mit

• m₁: Masse Extraktionshülse, leer
• m₂: Masse Extraktionshülse + Polymer
• m₃: Masse Extraktionshülse + Gel

The gel value of the polymer is calculated using the following formula: $$Gelwert=\frac{m_{\mathrm{3rd}}-m_1}{m_{\mathrm{2nd}}-m_1}\cdot 100\%$$

With

• m ₁ : mass of extraction sleeve, empty
• m ₂ : mass of extraction sleeve + polymer
• m ₃ : mass of extraction sleeve + gel

Static shear test

The test is based on PSTC-7 at 40 ° C using a weight of 1 kg. An aluminum foil with an etched surface is laminated onto a 250 µm thick adhesive tape pattern as a reinforcement foil. A 1.3 cm wide strip of this pattern is glued onto a polished steel plate with a length of 2 cm with a 2 kg roll by rolling it over twice. The platelets are equilibrated for 30 min under test conditions (40 ° C) but without load. Then the test weight (1 kg) is attached so that a shear stress is created parallel to the bond area, and the time is measured until the bond fails. The results are given in minutes.

Raw materials used:

Breon N41 H80

Nitrile butadiene rubber with an acrylonitrile content of 41% from Zeon Chemicals (London, UK)

Desmomelt 530

Largely linear hydroxyl polyurethane. Desmomelt 530 is a highly crystallizing, elastic polyurethane of very low thermoplasticity from Bayer MaterialScience

Epon Resin 828

Bifunctional bisphenol-A / epichlorohydrin liquid epoxy with a weight per epoxy of 185 - 192 g / eq from Momentive.

Tactix 556

Dicyclopentadiene-epoxy novolak resin with a weight per epoxy of 215 to 235 g / eq and a softening point of 53 ° C. from Huntsman.

Epiclon 673

Epoxy-cresol novolak resin with a weight per epoxy of 208 - 212 g / eq. and a softening range of 75 - 79 ° C.

Example: K1 parts by weight K2 parts by weight K3 parts by weight K4 parts by weight K5 parts by weight K6 parts by weight V1 parts by weight V2 parts by weight Breon N41H80 10th 20 35 20 20 55 20 Desmomelt 530 20 Epon Resin 828 45 40 32.5 20 60 22.5 80 Tactix556 80 Epiclon 673 45 40 32.5 60 20 22.5 Results Reference Adhesion strength steel at 23 ° C / 50% RH > 1N / cm > 1N / cm > 1N / cm > 1N / cm > 1N / cm > 1N / cm > 1N / cm > 1N / cm Shear strength 40 ° C / min. 620 950 1600 1270 810 740 3290 50 solubility ++ ++ + + ++ + - ++ Gel value /% 0 0 0 0 0 0 0 0 ILSS / MPa 29.7 29.1 28.3 29.3 29.6 29.8 26.2 29.6 29.75 delta ILSS /% - 0.2 -2.2 -4.9 -1.5 -0.5 +0.2 -11.9 -0.5

Production of adhesives

K1-6 and V1-V2 were kneaded in a Brabender kneader at 60 ° C until a homogeneous adhesive was obtained. The nitrile rubber was particularly well digested if parts or all of the reactive resins were added from the start.

An alternative production of the adhesives was shown as an example on K3. For this purpose, both the nitrile rubber and the solid reactive resin were metered into a planetary roller extruder in the first zone. Epon Resin 828 was added at a later dose point.

Manufacture of test specimens

The adhesive from the kneader was either pressed between two siliconized separating foils in a press to form approx. 30 µm thick pressure-sensitive transfer adhesive tapes or applied directly to the substrate using a hot-melt gun.

Sample geometry and testing

According to EN ISO 14130, the samples and their geometry are dependent on the laminate thickness for the ILSS test. A test specimen is ten times the length and five times the width. The distance between the supports (printing fins) also corresponds to five times the thickness. According to the test standard EN ISO 14130, it must be pointed out that the test result obtained is not an absolute value. Therefore, the term "apparent interlaminar shear strength" is used to define the measured quantities.

delta (ILSS): percentage change in ILSS compared to the reference in which the fiber mats were fixed without adhesive.

Reference: reference component without the use of fixing adhesives.

Adhesive foils produced on the kneader and pressed to approx. 30 µm were used for the evaluation. Examples K1-K3 show that the shear strength of the adhesives is improved with the polymer content, but the solubility in reactive resins decreases. If the polymer content becomes too high, for example in V1, the shear strength will increase further, but the adhesive will then no longer dissolve in the reactive resin. With a constant polymer content, K4 and K5 show how important it is to use a solid reactive resin, because in contrast to V2 both masses have sufficient shear values. Other polymers and compositions with only solid reactive resin (K6) also produce sufficiently shear-resistant adhesives that are soluble in reactive resin.

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• EP 2229421 B1 [0003, 0005, 0010]
• WO 2013/107829 A1 [0004]
• WO 2012/026980 A2 [0006]
• WO 1997/003828 A1 [0007]
• WO 2013/060588 A1 [0008, 0009, 0010]
• DE 102015208320 A1 [0011]
• US 3117099 [0041]
• US 3018262 [0042]

Non-patent literature cited

• J. Adhesion, 1991, vol. 34, pp. 189-200 or C.A. Dahlquist: Tack, adhesion, fundamentals and pra.ctice, McLaren and Sons Ltd., London, 1966 [0036]

Claims (15)

Temporary fixation adhesive for a first temporary fixation of two substrates to each other as a preliminary stage of a second final fixation of the two substrates, the second final fixation being carried out using a final fixation adhesive and this final fixation adhesive being the temporary fixation adhesive in the In the course of the second final fixation, characterized in that the temporary fixing adhesive is a pressure-sensitive adhesive which contains the following: a) at least one polymer b) optionally at least one adhesive resin c) at least one solid reactive resin d) optionally further reactive resins, the Temporary fixing adhesive per 100 parts of polymer and adhesive resin contains at least 185 parts of the at least one solid reactive resin. Temporary fixing adhesive after Claim 1 , characterized in that the temporary fixing adhesive is produced from components a) to d) in a solvent-free manner. Temporary fixing adhesive after Claim 1 or 2nd , characterized in that the solid reactive resin is an epoxy resin. Temporary fixing adhesive according to one of the Claims 1 to 3rd , characterized in that the further reactive resin is an epoxy resin. Temporary fixing adhesive according to one of the Claims 1 to 4th , characterized in that the further reactive resin is a liquid reactive resin with a viscosity <1,000 Pa · s. Temporary fixing adhesive according to one of the Claims 1 to 5 , characterized in that the at least one polymer is a nitrile rubber. Temporary fixing adhesive after Claim 6 , characterized in that the nitrile rubber contains more than 15%, in particular more than 25%, acrylonitrile. Adhesive tape containing the temporary fixing adhesive according to one of the Claims 1 to 7 . Tape after Claim 8 , the tape being available as a transfer tape without a strap. Use the temporary fixing adhesive according to one of the Claims 1 to 7 or the tape Claim 8 or 9 for the temporary fixation of fiber structures in composite production. Use the temporary fixing adhesive according to one of the Claims 1 to 7 or the tape Claim 8 or 9 for the temporary fixation of fiber structures in the manufacture of rotor blades. Use the temporary fixing adhesive according to one of the Claims 1 to 7 or the tape Claim 8 or 9 for the temporary fixation of fiber structures in vacuum resin infusion processes. Use according to one of the Claims 10 to 12th , characterized in that the tacky temporary fixing adhesive is applied from the melt. Process for producing the temporary fixing adhesive according to one of the Claims 1 to 7 , wherein the at least one polymer a) with the at least one solid reactive resin c) and the optional further components is digested in an extruder, characterized in that at least a part of the amount, preferably the total amount of solid reactive resin, of the polymer at the beginning of the digesting is added. Procedure according to Claim 14 , characterized in that the method is carried out in a planetary roller extruder.

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