Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Compositions to be polymerized by wave energy wherein said...
Reexamination Certificate
2000-08-15
2003-04-15
Berman, Susan W. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Compositions to be polymerized by wave energy wherein said...
C522S090000, C522S129000, C522S143000, C522S170000, C428S414000, C156S275500, C156S275700, C528S406000, C528S418000
Reexamination Certificate
active
06548566
ABSTRACT:
This invention relates to an adhesive containing three components A, B and C for the production of film laminates. Component A of the adhesive contains at least one compound containing at least one epoxy group, component B contains at least one compound with at least three OH groups and a molecular weight below 400 and component C contains at least one photoinitiator which initiates a polymerization of components A and B after exposure to light with a wavelength of 100 to 600 nm.
In the field of adhesives, particularly in the lamination of web-form materials, there is an increasing demand for short cure times and a shorter response time of the adhesives used for lamination. Conventional systems widely available on the market are generally based on polyurethane, acrylate or epoxy binders which cure by relatively slow crosslinking through reaction with added hardener or with moisture. The usual cure time for commercially available systems such as these is about 4 to about 21 days. However, a cure time as long as this to achieve maximal strength of the film laminates is generally not desirable.
Film laminates are exposed in their production, processing and use to a number of stresses which, typically, do not occur with other bonded materials or do not occur to the same extent as they do in film laminates. In the production of film laminates, materials partly differing in their flexibility and surface structure are bonded to one another. They are generally web-form materials of, for example, paper, plastics, plastics coated by vapor deposition with metals or metal oxides, more particularly transition metals oxides, or metal foils, more particularly aluminium foils.
During their production, processing and use, the film laminates are exposed to a number of mechanical stresses which impose stringent demands on the mechanical properties of the adhesive establishing the bond between the materials. Since the web-form materials to be bonded are normally materials with high flexibility which are constantly exposed to tensile and flexural stresses during production, processing and use, the adhesive itself has to possess sufficiently high flexibility to be able to withstand the stresses occurring without damage or failure of the adhesive bond.
In addition, however, the adhesive is also expected to show high peel strength to be able to withstand tensile stresses applied perpendicularly to the laminate surface without separation of the film laminate.
In addition, the adhesive is also generally expected to satisfy various criteria in regard to crystallization behavior and discoloration which exceed the performance features of adhesives for conventional applications. For example, in the bonding of transparent plastic films, the film laminate is also expected to remain transparent without clouding through crystallization of the adhesive. In addition, the adhesive must not have any tendency to form colored secondary products, even in the event of prolonged storage of the film laminate, for example under UV light.
In addition, film laminates are expected to show high heat resistance after only a short time. This property is particularly important when film laminates are to be used for packaging products while they are still hot, for example with a view to shortening production and filling cycles. However, the feature of heat resistance is also of importance when, for example, materials already at least partly wrapped in the film laminate are to be subjected to heating.
Problems are generally involved in the bonding of films which do not have the transparency required for initiating the polymerization reaction of the adhesive. If, therefore, the films to be bonded together are non-transparent materials, the adhesive-coated film generally has to be irradiated on the adhesive side before that side is bonded to a second film. This procedure presupposes that bonding to the second film takes place at a time at which polymerization of the adhesive, i.e. curing, is not yet complete. However, the adhesive must be capable of developing sufficient adhesion even at that time to ensure that the second web adheres.
Whereas radical-polymerizing adhesive systems often cure too quickly and show inadequate initial adhesion, cationically polymerizing adhesive systems lend themselves to a laminating process in which the adhesive layer applied to the first film is irradiated and the second film is subsequently applied. This is generally attributable to the fact that cationic systems have a slower cure rate than radical-polymerizing adhesive systems. However, another frequent disadvantage of commercially available systems is that the time which the adhesive bond takes to cure completely is thus too long for economic application of this bonding technique.
A quality criterion increasing in significance for film laminates is the substantial absence of “migrates”. Migrates are understood to be low molecular weight constituents of the film laminate which, on the one hand, are not immobile within the laminate, i.e. are capable of migrating within the laminate, and which on the other hand are capable of diffusing from the laminate into the material wrapped in the laminate. Since low molecular weight constituents such as these can affect the physical health of living beings, more particularly human beings, there is a need to provide substantially migrate-free film laminates.
DE-U 94 20 640 relates to radiation-curing compositions containing OH-terminated polyurethanes, an epoxy compound and a photoinitiator. The document in question describes a single-stage, radiation-curing adhesive composition which is characterized both by high initial adhesion and by high ultimate adhesion when it is used as a laminating adhesive.
EP-A 0 688 804 describes multicomponent, cationically curing epoxy compositions and a process for curing these compositions, it describes cationically curing epoxy compositions in various embodiments which generally contain as basic constituents a mixture of compounds that form Lewis acids and/or Brönsted acids under irradiation, cationically polymerizable monomers containing epoxy groups and at least one other constituent selected from the group of flexibilizing agents, retarders, radical-polymerizable monomers, accelerators and modifiers. Alcohols and glycols with a molecular weight of at least 200 to 20,000 g/mole are mentioned as flexibilizing agents.
DE-A 43 40 949 describes cationically curing epoxy compositions and their use. This document mentions a photoinitiated, cationically curing epoxy composition which contains at least one retarder, at least one accelerator, at least one ferrocenium complex salt and at least one cycloaliphatic compound containing epoxy groups together with typical auxiliaries and additives.
The adhesives representing the prior art are generally attended by the disadvantage that they do not satisfy all the requirements which an adhesive used for the production of film laminates is expected to meet. Thus, although quick-curing adhesives can be produced from epoxy compounds and polyurethane polyols, their heat resistance is not as good as it should be, for example, for the preparation of foods or the sterilization of medical instruments.
Accordingly, the problem addressed by the present invention was to provide an adhesive system for the production of film laminates which would withstand the severe stressing involved in the production, processing and use of such laminates and which would have a fast cure time and high shear and peel strengths. Another problem addressed by the invention was to provide an adhesive for the production of film laminates with which it would be possible to obtain film laminates characterized by high heat resistance and a minimal content of migrates (low molecular weight polyols).
The problems stated above have been solved by an adhesive containing at least three components A, B and C which is described in the following.
The present invention relates to the use of an adhesive containing at least three components A, B and C for the production of film laminate
Drobnik Michael
Henke Guenter
Huebener Achim
Berman Susan W.
Harper Stephen D.
Henkel Kommanditgesellschaft auf Aktien
LandOfFree
Laminating adhesives hardenable by radiation does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Laminating adhesives hardenable by radiation, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Laminating adhesives hardenable by radiation will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3014332