Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1997-06-03
2002-08-20
Gallagher, John J. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C524S186000, C524S502000
Reexamination Certificate
active
06436225
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a film laminating adhesive (FLA) composition comprising an N-methylol-based polyacrylic dispersion and polyalkyleneimine (PAI) and laminates thereof, a method for bonding substrates together using these compositions and a method for preparing these compositions.
BACKGROUND OF THE INVENTION
In order to sufficiently bond low-dyne substrates together, most applicators employ a two-coat system. The first coat is usually a primer and the second coat is an adhesive. Polyethyleneimine (PEI) is one such primer that is commercially available. Although PEI is a powerful adhesion promoter, it is commonly used only as a primer in very thin film thickness because of its high cost. Thus, it is more economical to employ a conventional synthetic polymeric adhesive to bond the desired substrates together. An example of a PEI application in two-coat systems is described in U.S. Pat. No. 3,507,685 which discloses a two-step treatment of cellulosic base material with polyethyleneimine as an anchor coating and an aldehyde as a crosslinking agent. Another example is U.S. Pat. No. 3,480,506 which discloses a process for preparing laminated wood structures using a thin sheet or film of modified polyolefin and a solution of polyalkyleneimine as an intermediate adhesion promoter coating. These applications use PAI in conjunction with another component in a two-step or two-coat process.
Other prior art references have described the addition of PEI to promote adhesion. U.S. Pat. No. 3,607,544 disclosed the addition of PEI to promote coating between sheets, foils, films and top coating to improve the bond between respective layers. U.S. Pat. No. 3,230,135 disclosed coating paper materials with polyimine to improve adhesion and heat strength. The paper web is coated with a thin film of polyethyleneimine composition prior to extrusion coating with polyethylene film. U.S. Pat. No. 3,457,101 disclosed thermosealable polyolefin film with multilayer coating of a) primer layer which is formed from a partial reaction product of an amine with an oxirane derivative, and b) a layer film or foil of vinyl or vinylidene polymer or copolymer.
The prior art compositions have performed satisfactorily for their intended purpose. However, for simplicity and efficiency, there is a need for a one-coat system that accomplishes the same result as a two-coat primer/adhesive system with improved adhesion and cohesive strength. None of the preceding references teach or suggest the use of an N-methylol-based polyacrylic dispersion/PAI blend as a stable system for adhering low-dyne substrates. The present inventor has found that the addition of PAI to an N-methylol-based polyacrylic dispersion can increase the adhesive strength (peel strength) of hard to bond surfaces, as well as increasing the cohesive strength without compromising adhesive strength.
SUMMARY OF THE INVENTION
The present invention provides a stable adhesive comprising a blend of N-methylol-based polyacrylic dispersions with PAI which produces the same or better adhesion between film type structures as a two-coat PAI primer/adhesive system. The level of the adhesion in laminated structures can be equal to or greater than the bonds obtained with other adhesives such as polyurethane dispersions.
This invention relates specifically to a blend of aqueous N-methylol-based polyacrylic dispersions and polyalkyleneimine (PAI). The polyacrylic dispersion comprises free radically polymerized acrylic and N-methylol-based monomers. The N-methylol-based monomer as used herein has the following general structure:
wherein
R=hydrogen or C
1
-C
4
alkyl
x=0-6 units; and
R
1
=hydrogen or C
1
-C
4
alkyl
These PAI-polyacrylic blends machine well, are extremely stable, and have a good pot life. The addition of PAI to an N-methylol-based polyacrylic dispersion dramatically increases the adhesive and cohesive strength several fold in film laminating adhesives as compared to the base polymer alone.
In one aspect, the invention provides a film laminating adhesive composition for dry bonding films for flexible packaging.
It is another object of the invention to provide a method for bonding substrates using an N-methylol-based polyacrylic dispersion and polyalkyleneimine as an adhesive for use in film laminating.
It is another object of the invention to provide a film laminating adhesive which attains excellent stability and bonding with difficult to bond substrates.
It is yet another object of the invention to provide a film laminating adhesive with increased cohesive strength without compromising adhesive strength.
It is still another object of the invention to provide laminates comprising a substrate laminated to another substrate, of the same or different material using the film laminating adhesive composition.
These, as well as other objects and advantages of the invention, are accomplished by providing blends of N-methylol-based polyacrylic dispersions and polyalkyleneimine as an adhesive for use in film laminating.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a one-component blend of N-methylol-based polyacrylic dispersions and polyalkyleneimine that produces the same effect as a two-step two component system for film laminating adhesive. The invention provides a film laminating adhesive having significant adhesive strength and improved cohesive strength.
The term “film” includes any substrate which can be adhered to another substrate of the same or different material with the present adhesive composition to form a flexible package or laminate. Included as “film” are any type of naturally occurring and synthetic materials. Representative examples of such materials and their forms include the following: paper, glassine paper, paperboard, fabrics, plastic, metal foil, metallized plastic film or most any other solids in the form of a film, sheet or paper. Plastic films include polyolefin films such as polyethylene and polypropylene, as well as polyamide or polyester film. Generally, these plastic films have low energy surfaces and are difficult to adhere to one another. Therefore, the surfaces are normally activated by corona discharge, flame oxidation, chemical etching or primer coating in order to promote adhesion. The films that are employed in the present invention are unlimited, but more specifically, the PAI-film laminating adhesive will be mainly used to bond flexible film to flexible film or paper. The adhesive of the present invention will be used for hard to bond surfaces, e.g., low dyne level substrates and anywhere a higher cohesive strength is needed. Examples of flexible packaging or laminates are dry snack food bags such as pretzel or potato chips, decorative ribbons or shopping bags.
The term “laminate ” includes structures that are manufactured by lamination using the present adhesive composition comprising N-methylol-based polyacrylic dispersions/PAI blend and films. A laminate structure typically comprises a substrate of the same or different films which are laminated to each other by coating the primary film or web with the present adhesive composition. The secondary web is then laminated to the primary web after the adhesive is dried.
The term “effective amount” means an amount sufficient to accomplish the intended purpose.
The term “T
g
” or glass transition temperature as used herein means the temperature at which a polymer changes from a glassy, brittle solid to a very high viscosity liquid. “T
g
” can be calculated by a well known mathematical procedure, as described, for example, by T. Nielsen in “Mechanical Properties of Polymers”, Reinhold Publishing Co., 1962, pp 22-27.
The term “acrylic” can include monoethylenically unsaturated monomers including acrylic, methacrylic, vinyl and allylic monomers, acrylate or methacrylate monomers. Additionally, acrylics can include acids, esters, amides and substituted derivatives thereof. Generally, the preferred acrylates are C
1
-C
20
alkyl acrylates or methacrylates. Examples of such acrylates include ethyl(meth)acryl
Gallagher John J.
H. B. Fuller Licensing & Financing Inc.
Su Bin
LandOfFree
N-methylol-based polyacrylic dispersion and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with N-methylol-based polyacrylic dispersion and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and N-methylol-based polyacrylic dispersion and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2950627