CA1339566C - Adhesive film - Google Patents
Adhesive filmInfo
- Publication number
- CA1339566C CA1339566C CA000558328A CA558328A CA1339566C CA 1339566 C CA1339566 C CA 1339566C CA 000558328 A CA000558328 A CA 000558328A CA 558328 A CA558328 A CA 558328A CA 1339566 C CA1339566 C CA 1339566C
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- CA
- Canada
- Prior art keywords
- adhesive
- film
- film according
- polyaddition
- constructional
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
- C09J7/00—Adhesives in the form of films or foils
- C09J7/20—Adhesives in the form of films or foils characterised by their carriers
- C09J7/22—Plastics; Metallised plastics
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
- C09J7/00—Adhesives in the form of films or foils
- C09J7/30—Adhesives in the form of films or foils characterised by the adhesive composition
- C09J7/35—Heat-activated
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Laminated Bodies (AREA)
- Adhesives Or Adhesive Processes (AREA)
- Adhesive Tapes (AREA)
Abstract
Multi layer structural adhesive film consisting of an elastomeric base film which is coated on both sides with a thermosetting constructional adhesive film. These films are suitable for bonding load-bearing parts.
Description
Adhesive Film The present invention relates to a multilayer adhesive film and also to its use for the bonding of load-bearing metal parts, in particular in the vehicle industry.
Hitherto load-bearing metal parts have been welded. The advantages of bonding load-bearing metal parts compared with welding are obvious: in addition to a reduction in weight as a consequence of increased energy absorption by the bonded parts and their improved energy transmission, investment in expensive welding robots is unnecessary. The change in the metal resulting from the welding spots, for example in the case of steel, and the increased susceptibility, associated therewith, of the metal to corrosion no longer take place. In addition, the bridging of gaps by bonded joints is better and the susceptibility of such joints to corrosion is therefore again reduced.
Previous attempts to employ adhesives to join load-bearing metal parts, for instance with epoxy resin pastes, did not yield a com-pletely satisfactory solution. Extremely high requirements are imposed today on such parts, in particular in relation to corrosion resistance, high peel strength and particularly high impact strength.
It has hitherto been the strength under impact conditions in partic-ular which has presented a problem only capable of an unsatisfactory solution by means of adhesives, and this explains why adhesives have been used in vehicle construction only to join non-load-bearing parts.
This applies to liquid and paste-like adhesives, and also to adhesive films.
Multi layer adhesive films for use in the vehicle industry, in par-ticular in motor car construction, have also been described. Thus, for example, double-sided adhesive films with two thermosetting formu-lations as adhesives and a woven textile base are known as repair aids from German Offenlegungsschrift 3,125,393. The French Publication No. 2,201,184 describes adhesive films consisting of a highly fluor-inated elastomer and two hot-curing epoxy resin layers for joining materials with unequal coefficients of thermal expansion, for instance -1339~6~
metal and glass.
The present invention relates to a multilayer structural adhesive film consisting of an elastomeric base film of styrene-butadiene (SBR) or acrylonitrile-butadiene rubber (NBR) or a polyurethane elastomer which is coated on both sides with a thermosetting constructional adhesive film, said adhesive being a polyaddition, a polycondensation or a polymerization adhesive.
Suitable elastomeric base films are materials which combine the application characteristics of elastomers with those of thermoplastic materials. Typical examples thereof are styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), but also polyurethane elastomers such as thermoplastic polyurethane elastomers (TPU). These elastomers are well known to those skilled in the art and are commercially available in various modifications and compositions. In these cases the thickness of the film is 0.05 to 1.5 mm, preferably 0.15 to 1.5 mm.
Particularly good results can be achieved if the surface of the elastomeric film is textured.
In a particularly preferred embodiment, the elastomeric base film is perforated. The perforations may take the form of punched holes or the form of incisions or slits. This achieves the result that the thermosetting materials come into direct contact at various selected points. Surprisingly, the impact strength is further increased as a result. In addition, the behaviour under dynamic and static load, and the fatigue limit are improved. This is apparent particularly at elevated temperature, without the excellent low-temperature characteristics being impaired. The proportion of the perforation referred to the total area of the elastomeric base film may constitute up to 70%.
preferably it is 10 to 60%, and in particular 10-30%. The diameter of the perforation is, for example, 0.5 to 5 mm, in particular 1.0 to 3.0 mm.
Suitable thermosetting constructional adhesives are a polyaddition, a polycondensation or a polymerization adhesive.
The thermosetting layer has a thickness of 0.05 to 1 mmr preferably 0.15 to 0.5 mm.
Typical representatives of polyaddition adhesives are epoxy resins. Hot-curing epoxy resin adhesives are suitable for the application envisaged. Typical reactants are carboxylic acid anhydrides, phenols or polyamines. As hardeners or hardenin~ accelerators, mention may be made here, for example, of the following substances: cyanamide, di-cyandiamide, hydrazides, Friedel-Crafts catalysts such as boron tri-fluoride and boron trichloride and their complexes and chelates which are obtained by reacting boron trihalides with, for example, 1,3-di-ketones. Mention may also furthermore be made of imidazoles such as l-methylimidazole. The nature and quantity of hardeners or hardening catalysts are familiar to those skilled in the art and permit them to match adhesive systems to the special requirements in relation to adhesive layer characteristics and curing conditions. The processing conditions, especially the pot life, are also determined to a decisive extent by the particular formulations. The single-component epoxy resin adhesives may be highlighted here as particularly preferred.
Since the reaction mixture consisting of the two components may be regarded in this connection as one component from the process engin-eering point of view, such systems are also described as single-component thermo-setting adhesives. The single-component thermo-setting adhesives have the advantage that dispensing errors during use are eliminated since the two components are already mixed at the premises of the adhesive manufacturer.
Elastomer-modified epoxy resins are also very suitable. These are known under the designation of toughened epoxy resin adhesives. In this case up to 10% by weight of a rubber, for example acrylonitrile-butadiene rubber are added to the epoxy resin. The rubber particles become dispersed in the polymer and impart increased toughness without substantially reducing the cohesive strength.
Another category of adhesives which fall within the definition of poly-addition adhesives are single-component polyurethane adhesives.
Since the simple, low-molecular polyisocyanates form relatively hard and brittle adhesive layers with low strength values on reaction with moisture, the starting point in the single-component systems is pre-ferably pre-crosslinked polymers, so-called prepolymers. These compounds are known and are produced from higher-molecular polyols with a stoichiometric excess of isocyanate. In this manner compounds 1339~66 are produced which already have urethane formations but, on the other hand, still have reactive isocyanate groups which are accessible to the reaction with moisture.
In addition to these single-component polyurethane adhesives, therm-ally activatable polyurethane adhesives, i.e. compounds in which the isocyanate group is masked or blocked and the isocyanate group can only be removed at elevated temperature, are also suitable for the application according to the invention, as are reactive polyurethane hotmelt adhesives which, as is known, can be produced using higher-molecular crystallizing and fusible diol and isocyanate components.
The cross-linking of the fusible prepolymers again takes place by additional exposure to moisture which acts on the reactive isocyanate groups still present and the crosslinking takes place via urea bonds to the adhesive layer polymer.
Within the scope of the present invention, the term "polycondensation adhesive" is understood to mean formaldehyde condensates, polyimides and polysulfones. Of the formaldehyde condensates, phenol-formalde-hyde resin adhesives and cresol-/resorcinol-formaldehyde resin adhe-sives are particularly preferred. It is known to those skilled in the art that, of the phenol-formaldehyde resins, only the so-called resols are suitable for use as an adhesive. These are thermosetting phenolic resins which, although they are soluble and fusible in the initial stage, can be converted in the adhesive joint by heat or catalytic action into the insoluble, nonfusible state, the so-called resites, with a high degree of crosslinking. Because of the often troublesome brittleness, pure phenol-formaldehyde resins are modified with further compounds by copolymerization or cocondensation with suitable monomers which predominantly yield thermoplastic polymers, for example with polyvinylformal, polyvinyl butyral, polyamides, elastomers such as polychloroprene, nitrile rubber, and also epoxy resins and similar materials.
As a rule the cresol- and the resorcinol-formaldehyde adhesives also require suitable modification. These are generally notable for a higher rate of hardening and greater resistance to weathering 1339 ~66 effects.
Polyimide adhesives are notable particularly for their high heat resistance. The production of industrially usable polyimides is carried out by reacting the anydrides of tetra-basic acids, for example pyromellitic anhydride with aromatic diamines, for example diaminodiphenyl oxide. m e use takes place in the form of precon-densate films.
Of the polymerization adhesives, especially the acrylic resins or methacrylic resins are of importance. The fact that the free-radical chaln-growth polymerization of the MMA monomer involves reactions which proceed very rapidly after the components - monomer, hardener and accelerator - have been combined, has resulted in several developments of a processing tailored to manufacturing needs for practical application. These are known to those skilled in the art as A-B processes and no-mix processes.
All the thermosetting constructional adhesives mentioned are basically known adhesives. The choice of the particular system depends on the particular requirements of a particular application. The advantages which are basically inherent in a particular constructional adhesive are known per se to those skilled in the art. It was not possible to foresee, however, that the load-bearing parts fully bonded with the claimed structural adhesive films are capable of absorbing equal, and in some cases higher, energies than welded constructions. This completely surprising behaviour, coupled with the advantages of the bonded joints generally, such as, for example, the optimum corrosion protection, make it possible to bond load-bearing parts in vehicle construction cheaply, cleanly and durably and make the use of the films according to the invention particularly attractive in mass-production motor car construction.
The term "structural adhesive" or "constructional adhesive" are under-stood to mean adhesives which, in the cured state, have mechanical properties which have a particular minimum level, have fatigue strength, can be varied reproducibly and can therefore be used for 13395fi6 reliably designing and dimensioning adhesive bonds. In a wider sense, if account is taken of the stress conditions to be required and if the component construction is suitable, these adhesives make it possible to produce a bond with the most economic utilization of the parts to be joined possible. The terms chosen here and familiar to those skilled in the art are descriptions which essentially serve as a distinction from adhesive systems of lower adhesive layer strengths, for example contact or pressure-sensitive adhesives.
Obviously, mixtures of the abovementioned thermosetting plastics are also suitable as constructional adhesive films, i.e. the structural adhesive films may be coated with constructional adhesive films which are chemically different from each other. Preferred are epoxy resin adhesives or mixtures of two different epoxy resins.
The production of the multilayer structural adhesive films according to the invention is known. The procedure for doing this may, for example, be such that a solution of the thermosetting plastic or preferably a melt is applied to the elastomeric base film with a doctor blade. This multilayer film produced in this manner is stored at a temperature at which the curing does not as yet occur. A
particular advantage of adhesive film technology is prefabrication.
This is understood to mean the bringing together of a section of film cut to size and the part to be joined. The adhesive layer then sets after combination with the second piece to be joined under the influence of energy. Depending on the starting monomers, the curing reaction normally takes place at temperatures between 80~ and 250~C.
In this connection, it should be noted that in choosing the adhesives for this type of combination bonding, similar time and temperature curing parameters are a prerequisite for obtaining optimally cured adhesive layers in all cases under the same conditions.
In order to achieve an optimum adhesion between elastomeric base film and thermosetting adhesive film, in a preferred embodiment of the present invention, the base film is pretreated. The polyurethane elastomers are pretreated, as is known, by applying a so-called primer, for example a silane adhesion promotor. In the case of the ~ 7 ~ 13~66 styrene-butadiene and acrylonitril~-butadiene rubbers, the surface is preferably partially oxidized, for example by treatment with sulfuric acid or with an oxygen plasma or by means of corona radiation. This involves common techniques which have hitherto been carried out on the numerous, commercially available elastomeric films.
The thermosetting constructional adhesive films which are applied to both sides of the base film are preferably chemically identical; they may, however, also be different in order to make allowance for the different materials to be bonded.
If desired, to adjust the viscosity, reactive diluents such as, for example, styrene oxide, butyl glycidyl ether, 2,2,4-trimethylpentyl glycidyl ether, phenyl glycidyl ether, cresyl glycidyl ether or glycidyl esters of synthetic, highly branched, mainly tertiary al-phatic monocarboxylic acids may be added to the mixtures according to the invention. As other common additives, the mixtures according to the invention may furthermore contain plasticizers, extenders, fillers and reinforcing agents such as, for example, coal tar, bitumen, tex-tile fibres, glass fibres, asbestos fibres, boron fibres, carbon fibres, mineral silicates, mica, silica flour, aluminium oxide hy-drate, bentonites, kaolin, silicic acid aerogel or metal powder, for example aluminiu~ powder or iron powder, and also pigments and dyes such as soot, oxide colours and titanium dioxide, flame retardents, thixotropic agents, flow control agents such as silicones, waxes and stearates, which are also used in some cases as mould release agents, adhesion promoters, antioxidants and light protection agents.
Example 1: To bond steel sheets, a film system of the following composition was produced:
A) Elastomeric base film: 0.25 mm thick styrene-butadiene rubber film (available commercially, Shore hardness 63-70, tensile strength 15-20 MPa, surface textured).
B) Thermosetting constructional adhesive:
20% by weight of liquid epoxy resin based on bisphenol A (epoxy value 5.3 e q/ kg) 35% by weight of an epoxy resin based on bisphenol A (epoxy value 5.3 eqlkg) modified with a carboxyl-terminated butadiene rubber (CTBN rubber) in the ratio 70: 30 20% by weight of sol id epoxy resin based on bisphenol A (epoxy value 1.6 eq/kg) 20% by weight of chalk 2.5% by weight of dicyandiamide 1.0% by weight of monuron 1. 5% by weight of aerosil thixotropic agent The epoxy resins of the thermosetting adhesive composition are homo-geneously mixed in a divided trough kneader at 100-130~C in vacuo.
The filler, the accelerator, monuron and thixotropic agent were successively added, also in vacuo, with the temperature of the mixture being allowed to drop at the same time to 80~C.
The thermosetting constructional adhesive (A) thus produced is applied to both sides of the elastomeric base film to a thickness of 0.1 mm in each case on a doctor-blade coater at 80-90~C.
Example 2: The multilayer adhesive film according to Example 1 is laid between two oiled steel sheets (steel 1403) and cured for 30 min at 180~C. The bonded construction has the following properties:
(a) Shear strength according to DIN 53 283: 8-9 N/mm2 (b) Floating roller peel test according to DIN 53 289: 8-10 Nlmm After 28 cycles (16 h at 80%, 99% humidity and 4 h at -30~C):
(c) Shear strength according to DIN 53 283: 6-8 N¦mm2 (d) Corrosion: none, cohesive fracture Example 3: Analogously to Example 1, a film system of the same chemi-cal composition was produced, in which, however, the textured elasto-meric film A) had a thickness of 0.4 mm and the constructional 1339~6~
_ 9 _ adhesive layers had a thickness of 0. 5 mm each. This mul tilayer adhesive film is laid between two oiled steel sheets (steel 1403) and cured for 30 min at 180~C. me bonded construction has the following properties:
(a) Shear strength according to DIN 53 283: 11 N/mm2 (b) ~loating roller peel strength according to DIN 53 289: 16 N/mm (c) Impact strength: 37 Nm Example 4: Analogously to Example 1, a film system of the same chemical composition was produced in which the textured elastomeric film A) had a thickness of 0.4 mm and uniformly distributed perfor-at~ons having a diameter of 2 mm, and the constructional adhesive layers were each 0.3 mm thick. This multilayer adhesive film with the proportion of perforations mentioned below is laid between two oiled steel sheets (steel 1403) and cured for 30 min at 180~C. The bonded construction has the following properties:
Proportion of the area occupied by the perforations in the elastomeric film 1 0% 3 0% 60%
( a) Shear strength according 7-8 N/mm2 6-7N/mm2 6-7N/mm2 to DIN 53 2 83 (b) ~loating roller peel strength according to DIN 53 289 17N/mm 16N/mm 14 N/mm
Hitherto load-bearing metal parts have been welded. The advantages of bonding load-bearing metal parts compared with welding are obvious: in addition to a reduction in weight as a consequence of increased energy absorption by the bonded parts and their improved energy transmission, investment in expensive welding robots is unnecessary. The change in the metal resulting from the welding spots, for example in the case of steel, and the increased susceptibility, associated therewith, of the metal to corrosion no longer take place. In addition, the bridging of gaps by bonded joints is better and the susceptibility of such joints to corrosion is therefore again reduced.
Previous attempts to employ adhesives to join load-bearing metal parts, for instance with epoxy resin pastes, did not yield a com-pletely satisfactory solution. Extremely high requirements are imposed today on such parts, in particular in relation to corrosion resistance, high peel strength and particularly high impact strength.
It has hitherto been the strength under impact conditions in partic-ular which has presented a problem only capable of an unsatisfactory solution by means of adhesives, and this explains why adhesives have been used in vehicle construction only to join non-load-bearing parts.
This applies to liquid and paste-like adhesives, and also to adhesive films.
Multi layer adhesive films for use in the vehicle industry, in par-ticular in motor car construction, have also been described. Thus, for example, double-sided adhesive films with two thermosetting formu-lations as adhesives and a woven textile base are known as repair aids from German Offenlegungsschrift 3,125,393. The French Publication No. 2,201,184 describes adhesive films consisting of a highly fluor-inated elastomer and two hot-curing epoxy resin layers for joining materials with unequal coefficients of thermal expansion, for instance -1339~6~
metal and glass.
The present invention relates to a multilayer structural adhesive film consisting of an elastomeric base film of styrene-butadiene (SBR) or acrylonitrile-butadiene rubber (NBR) or a polyurethane elastomer which is coated on both sides with a thermosetting constructional adhesive film, said adhesive being a polyaddition, a polycondensation or a polymerization adhesive.
Suitable elastomeric base films are materials which combine the application characteristics of elastomers with those of thermoplastic materials. Typical examples thereof are styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), but also polyurethane elastomers such as thermoplastic polyurethane elastomers (TPU). These elastomers are well known to those skilled in the art and are commercially available in various modifications and compositions. In these cases the thickness of the film is 0.05 to 1.5 mm, preferably 0.15 to 1.5 mm.
Particularly good results can be achieved if the surface of the elastomeric film is textured.
In a particularly preferred embodiment, the elastomeric base film is perforated. The perforations may take the form of punched holes or the form of incisions or slits. This achieves the result that the thermosetting materials come into direct contact at various selected points. Surprisingly, the impact strength is further increased as a result. In addition, the behaviour under dynamic and static load, and the fatigue limit are improved. This is apparent particularly at elevated temperature, without the excellent low-temperature characteristics being impaired. The proportion of the perforation referred to the total area of the elastomeric base film may constitute up to 70%.
preferably it is 10 to 60%, and in particular 10-30%. The diameter of the perforation is, for example, 0.5 to 5 mm, in particular 1.0 to 3.0 mm.
Suitable thermosetting constructional adhesives are a polyaddition, a polycondensation or a polymerization adhesive.
The thermosetting layer has a thickness of 0.05 to 1 mmr preferably 0.15 to 0.5 mm.
Typical representatives of polyaddition adhesives are epoxy resins. Hot-curing epoxy resin adhesives are suitable for the application envisaged. Typical reactants are carboxylic acid anhydrides, phenols or polyamines. As hardeners or hardenin~ accelerators, mention may be made here, for example, of the following substances: cyanamide, di-cyandiamide, hydrazides, Friedel-Crafts catalysts such as boron tri-fluoride and boron trichloride and their complexes and chelates which are obtained by reacting boron trihalides with, for example, 1,3-di-ketones. Mention may also furthermore be made of imidazoles such as l-methylimidazole. The nature and quantity of hardeners or hardening catalysts are familiar to those skilled in the art and permit them to match adhesive systems to the special requirements in relation to adhesive layer characteristics and curing conditions. The processing conditions, especially the pot life, are also determined to a decisive extent by the particular formulations. The single-component epoxy resin adhesives may be highlighted here as particularly preferred.
Since the reaction mixture consisting of the two components may be regarded in this connection as one component from the process engin-eering point of view, such systems are also described as single-component thermo-setting adhesives. The single-component thermo-setting adhesives have the advantage that dispensing errors during use are eliminated since the two components are already mixed at the premises of the adhesive manufacturer.
Elastomer-modified epoxy resins are also very suitable. These are known under the designation of toughened epoxy resin adhesives. In this case up to 10% by weight of a rubber, for example acrylonitrile-butadiene rubber are added to the epoxy resin. The rubber particles become dispersed in the polymer and impart increased toughness without substantially reducing the cohesive strength.
Another category of adhesives which fall within the definition of poly-addition adhesives are single-component polyurethane adhesives.
Since the simple, low-molecular polyisocyanates form relatively hard and brittle adhesive layers with low strength values on reaction with moisture, the starting point in the single-component systems is pre-ferably pre-crosslinked polymers, so-called prepolymers. These compounds are known and are produced from higher-molecular polyols with a stoichiometric excess of isocyanate. In this manner compounds 1339~66 are produced which already have urethane formations but, on the other hand, still have reactive isocyanate groups which are accessible to the reaction with moisture.
In addition to these single-component polyurethane adhesives, therm-ally activatable polyurethane adhesives, i.e. compounds in which the isocyanate group is masked or blocked and the isocyanate group can only be removed at elevated temperature, are also suitable for the application according to the invention, as are reactive polyurethane hotmelt adhesives which, as is known, can be produced using higher-molecular crystallizing and fusible diol and isocyanate components.
The cross-linking of the fusible prepolymers again takes place by additional exposure to moisture which acts on the reactive isocyanate groups still present and the crosslinking takes place via urea bonds to the adhesive layer polymer.
Within the scope of the present invention, the term "polycondensation adhesive" is understood to mean formaldehyde condensates, polyimides and polysulfones. Of the formaldehyde condensates, phenol-formalde-hyde resin adhesives and cresol-/resorcinol-formaldehyde resin adhe-sives are particularly preferred. It is known to those skilled in the art that, of the phenol-formaldehyde resins, only the so-called resols are suitable for use as an adhesive. These are thermosetting phenolic resins which, although they are soluble and fusible in the initial stage, can be converted in the adhesive joint by heat or catalytic action into the insoluble, nonfusible state, the so-called resites, with a high degree of crosslinking. Because of the often troublesome brittleness, pure phenol-formaldehyde resins are modified with further compounds by copolymerization or cocondensation with suitable monomers which predominantly yield thermoplastic polymers, for example with polyvinylformal, polyvinyl butyral, polyamides, elastomers such as polychloroprene, nitrile rubber, and also epoxy resins and similar materials.
As a rule the cresol- and the resorcinol-formaldehyde adhesives also require suitable modification. These are generally notable for a higher rate of hardening and greater resistance to weathering 1339 ~66 effects.
Polyimide adhesives are notable particularly for their high heat resistance. The production of industrially usable polyimides is carried out by reacting the anydrides of tetra-basic acids, for example pyromellitic anhydride with aromatic diamines, for example diaminodiphenyl oxide. m e use takes place in the form of precon-densate films.
Of the polymerization adhesives, especially the acrylic resins or methacrylic resins are of importance. The fact that the free-radical chaln-growth polymerization of the MMA monomer involves reactions which proceed very rapidly after the components - monomer, hardener and accelerator - have been combined, has resulted in several developments of a processing tailored to manufacturing needs for practical application. These are known to those skilled in the art as A-B processes and no-mix processes.
All the thermosetting constructional adhesives mentioned are basically known adhesives. The choice of the particular system depends on the particular requirements of a particular application. The advantages which are basically inherent in a particular constructional adhesive are known per se to those skilled in the art. It was not possible to foresee, however, that the load-bearing parts fully bonded with the claimed structural adhesive films are capable of absorbing equal, and in some cases higher, energies than welded constructions. This completely surprising behaviour, coupled with the advantages of the bonded joints generally, such as, for example, the optimum corrosion protection, make it possible to bond load-bearing parts in vehicle construction cheaply, cleanly and durably and make the use of the films according to the invention particularly attractive in mass-production motor car construction.
The term "structural adhesive" or "constructional adhesive" are under-stood to mean adhesives which, in the cured state, have mechanical properties which have a particular minimum level, have fatigue strength, can be varied reproducibly and can therefore be used for 13395fi6 reliably designing and dimensioning adhesive bonds. In a wider sense, if account is taken of the stress conditions to be required and if the component construction is suitable, these adhesives make it possible to produce a bond with the most economic utilization of the parts to be joined possible. The terms chosen here and familiar to those skilled in the art are descriptions which essentially serve as a distinction from adhesive systems of lower adhesive layer strengths, for example contact or pressure-sensitive adhesives.
Obviously, mixtures of the abovementioned thermosetting plastics are also suitable as constructional adhesive films, i.e. the structural adhesive films may be coated with constructional adhesive films which are chemically different from each other. Preferred are epoxy resin adhesives or mixtures of two different epoxy resins.
The production of the multilayer structural adhesive films according to the invention is known. The procedure for doing this may, for example, be such that a solution of the thermosetting plastic or preferably a melt is applied to the elastomeric base film with a doctor blade. This multilayer film produced in this manner is stored at a temperature at which the curing does not as yet occur. A
particular advantage of adhesive film technology is prefabrication.
This is understood to mean the bringing together of a section of film cut to size and the part to be joined. The adhesive layer then sets after combination with the second piece to be joined under the influence of energy. Depending on the starting monomers, the curing reaction normally takes place at temperatures between 80~ and 250~C.
In this connection, it should be noted that in choosing the adhesives for this type of combination bonding, similar time and temperature curing parameters are a prerequisite for obtaining optimally cured adhesive layers in all cases under the same conditions.
In order to achieve an optimum adhesion between elastomeric base film and thermosetting adhesive film, in a preferred embodiment of the present invention, the base film is pretreated. The polyurethane elastomers are pretreated, as is known, by applying a so-called primer, for example a silane adhesion promotor. In the case of the ~ 7 ~ 13~66 styrene-butadiene and acrylonitril~-butadiene rubbers, the surface is preferably partially oxidized, for example by treatment with sulfuric acid or with an oxygen plasma or by means of corona radiation. This involves common techniques which have hitherto been carried out on the numerous, commercially available elastomeric films.
The thermosetting constructional adhesive films which are applied to both sides of the base film are preferably chemically identical; they may, however, also be different in order to make allowance for the different materials to be bonded.
If desired, to adjust the viscosity, reactive diluents such as, for example, styrene oxide, butyl glycidyl ether, 2,2,4-trimethylpentyl glycidyl ether, phenyl glycidyl ether, cresyl glycidyl ether or glycidyl esters of synthetic, highly branched, mainly tertiary al-phatic monocarboxylic acids may be added to the mixtures according to the invention. As other common additives, the mixtures according to the invention may furthermore contain plasticizers, extenders, fillers and reinforcing agents such as, for example, coal tar, bitumen, tex-tile fibres, glass fibres, asbestos fibres, boron fibres, carbon fibres, mineral silicates, mica, silica flour, aluminium oxide hy-drate, bentonites, kaolin, silicic acid aerogel or metal powder, for example aluminiu~ powder or iron powder, and also pigments and dyes such as soot, oxide colours and titanium dioxide, flame retardents, thixotropic agents, flow control agents such as silicones, waxes and stearates, which are also used in some cases as mould release agents, adhesion promoters, antioxidants and light protection agents.
Example 1: To bond steel sheets, a film system of the following composition was produced:
A) Elastomeric base film: 0.25 mm thick styrene-butadiene rubber film (available commercially, Shore hardness 63-70, tensile strength 15-20 MPa, surface textured).
B) Thermosetting constructional adhesive:
20% by weight of liquid epoxy resin based on bisphenol A (epoxy value 5.3 e q/ kg) 35% by weight of an epoxy resin based on bisphenol A (epoxy value 5.3 eqlkg) modified with a carboxyl-terminated butadiene rubber (CTBN rubber) in the ratio 70: 30 20% by weight of sol id epoxy resin based on bisphenol A (epoxy value 1.6 eq/kg) 20% by weight of chalk 2.5% by weight of dicyandiamide 1.0% by weight of monuron 1. 5% by weight of aerosil thixotropic agent The epoxy resins of the thermosetting adhesive composition are homo-geneously mixed in a divided trough kneader at 100-130~C in vacuo.
The filler, the accelerator, monuron and thixotropic agent were successively added, also in vacuo, with the temperature of the mixture being allowed to drop at the same time to 80~C.
The thermosetting constructional adhesive (A) thus produced is applied to both sides of the elastomeric base film to a thickness of 0.1 mm in each case on a doctor-blade coater at 80-90~C.
Example 2: The multilayer adhesive film according to Example 1 is laid between two oiled steel sheets (steel 1403) and cured for 30 min at 180~C. The bonded construction has the following properties:
(a) Shear strength according to DIN 53 283: 8-9 N/mm2 (b) Floating roller peel test according to DIN 53 289: 8-10 Nlmm After 28 cycles (16 h at 80%, 99% humidity and 4 h at -30~C):
(c) Shear strength according to DIN 53 283: 6-8 N¦mm2 (d) Corrosion: none, cohesive fracture Example 3: Analogously to Example 1, a film system of the same chemi-cal composition was produced, in which, however, the textured elasto-meric film A) had a thickness of 0.4 mm and the constructional 1339~6~
_ 9 _ adhesive layers had a thickness of 0. 5 mm each. This mul tilayer adhesive film is laid between two oiled steel sheets (steel 1403) and cured for 30 min at 180~C. me bonded construction has the following properties:
(a) Shear strength according to DIN 53 283: 11 N/mm2 (b) ~loating roller peel strength according to DIN 53 289: 16 N/mm (c) Impact strength: 37 Nm Example 4: Analogously to Example 1, a film system of the same chemical composition was produced in which the textured elastomeric film A) had a thickness of 0.4 mm and uniformly distributed perfor-at~ons having a diameter of 2 mm, and the constructional adhesive layers were each 0.3 mm thick. This multilayer adhesive film with the proportion of perforations mentioned below is laid between two oiled steel sheets (steel 1403) and cured for 30 min at 180~C. The bonded construction has the following properties:
Proportion of the area occupied by the perforations in the elastomeric film 1 0% 3 0% 60%
( a) Shear strength according 7-8 N/mm2 6-7N/mm2 6-7N/mm2 to DIN 53 2 83 (b) ~loating roller peel strength according to DIN 53 289 17N/mm 16N/mm 14 N/mm
Claims (12)
1. A multilayer structural adhesive film consisting of an elastomeric base film of styrene-butadiene (SBR) or acrylonitrile-butadiene rubber (NBR) or a polyurethane elastomer which is coated on both sides with a thermosetting constructional adhesive film, said adhesive being a polyaddition, a polycondensation or a polymerization adhesive.
2. A film according to claim 1, wherein the elastomeric base film is perforated.
3. A film according to claim 1, wherein the polyaddition adhesive is a hot-curing epoxy resin adhesive.
4. A film according to claim 1, wherein the polyaddition adhesive is a single-component epoxy resin adhesive.
5. A film according to claim 1, wherein the polyaddition adhesive is a moisture-curing polyurethane adhesive.
6. A film according to claim 1, wherein the polyaddition adhesive is a single-component polyurethane adhesive.
7. A film according to claim 1, wherein the polycondensation adhesive is a phenol- or cresol-/resorcinol-formaldehyde resin adhesive.
8. A film according to claim 1, wherein the polycondensation adhesive is a polyimide.
9. A film according to claim 1, wherein the polymerization adhesive is an acrylate resin or a methacrylate resin.
10. A film according to claim 1, wherein the elastomeric base film has a thickness of 0.05 to 1.5 mm and the constructional adhesive films have a thickness of 0.05 to 1 mm each and the multilayer system has a minimum thickness of 0.5 mm.
11. A film according to claim 1, wherein the two constructional adhesive films are chemically identical.
12. Use of the films according to claim 1 for bonding load-bearing parts.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CH488/87-0 | 1987-02-10 | ||
| CH48887 | 1987-02-10 | ||
| CH100987 | 1987-03-17 | ||
| CH1009/87-0 | 1987-03-17 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1339566C true CA1339566C (en) | 1997-12-02 |
Family
ID=25684717
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000558328A Expired - Fee Related CA1339566C (en) | 1987-02-10 | 1988-02-08 | Adhesive film |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0279777B2 (en) |
| JP (1) | JP2646102B2 (en) |
| CA (1) | CA1339566C (en) |
| DE (1) | DE3864160D1 (en) |
Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4908273A (en) * | 1987-03-24 | 1990-03-13 | Ciba-Geigy Corporation | Multi-layer, heat-curable adhesive film |
| JPH02122046U (en) * | 1989-03-17 | 1990-10-04 | ||
| JPH0734912Y2 (en) * | 1990-09-11 | 1995-08-09 | イナバゴム株式会社 | Thermal adhesive seal member |
| JP3221978B2 (en) * | 1993-05-11 | 2001-10-22 | ヤマウチ株式会社 | Cushion material for hot press molding, method for producing the same, heat-resistant heat-sensitive adhesive sheet for cushion material for hot press molding, and method for producing the same |
| US6333115B1 (en) | 1998-08-24 | 2001-12-25 | Premark Rwp Holdings, Inc. | Thin film adhesive, method of making, products made therefrom |
| US6333073B1 (en) | 1999-02-25 | 2001-12-25 | Premark Rwp Holdings, Inc. | Adhesive tape and products made therefrom |
| EP1279695A1 (en) * | 2001-07-23 | 2003-01-29 | Silu Verwaltung AG | Adhesive mounting tape for improved sealing of gaps and dispenser |
| KR102235987B1 (en) * | 2018-06-05 | 2021-04-02 | 주식회사 엘지화학 | Stretchable adhesive film and display device comprising the same |
| WO2023083472A1 (en) * | 2021-11-15 | 2023-05-19 | Lohmann Gmbh & Co. Kg | Adhesive tape |
Family Cites Families (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL94814C (en) * | ||||
| US3703434A (en) * | 1968-03-29 | 1972-11-21 | Minnesota Mining & Mfg | Heat-activatable adhesive sheets |
| JPS4929160U (en) * | 1972-06-15 | 1974-03-13 | ||
| FR2201184A1 (en) * | 1972-10-04 | 1974-04-26 | Matra Engins | Elastomer/epoxy composite for component assembly - consisting of elastomer sheet coated with solid film of thermosetting epoxy resin on both faces |
| JPS502952U (en) * | 1973-05-16 | 1975-01-13 | ||
| FR2404039A1 (en) * | 1977-09-23 | 1979-04-20 | Peintures Ind Ass | Elastic heat sealing prod. used with textiles - partic. clothing, comprising elastic support layer with adhesive coating |
| JPS5617395A (en) * | 1979-07-20 | 1981-02-19 | Dx Antenna | Driving unit for display device |
| EP0050096A1 (en) * | 1980-10-14 | 1982-04-21 | Ciba-Geigy Ag | Process for bonding objects by curable adhesives |
| DE3125393A1 (en) * | 1981-06-27 | 1983-01-13 | Dr.Ing.H.C. F. Porsche Ag, 7000 Stuttgart | Connection of at least two walls |
-
1988
- 1988-02-04 EP EP88810065A patent/EP0279777B2/en not_active Expired - Lifetime
- 1988-02-04 DE DE8888810065T patent/DE3864160D1/en not_active Expired - Lifetime
- 1988-02-08 CA CA000558328A patent/CA1339566C/en not_active Expired - Fee Related
- 1988-02-10 JP JP63029986A patent/JP2646102B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JP2646102B2 (en) | 1997-08-25 |
| EP0279777B1 (en) | 1991-08-14 |
| EP0279777A1 (en) | 1988-08-24 |
| JPS63199785A (en) | 1988-08-18 |
| DE3864160D1 (en) | 1991-09-19 |
| EP0279777B2 (en) | 1994-03-09 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |