Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-11-08
2003-09-23
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C523S406000, C523S407000, C528S093000, C528S097000, C528S103000, C528S119000
Reexamination Certificate
active
06624213
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to high temperature resistant epoxy-based adhesive films.
BACKGROUND OF THE INVENTION
Polyepoxide resins are monomers or prepolymers that react with curing agents to yield high performance resins. These resins have gained wide acceptance in structural adhesives because of their combination of characteristics such as thermal and chemical resistance, adhesion, and abrasion resistance.
Cured epoxy resins are frequently required to have high glass transition temperatures in order to provide adhesives having structural properties at high temperatures. Examples of methods of achieving high glass transition temperatures in such polyepoxide resins include: preparing resins having a high crosslink density and a high concentration of polar groups as disclosed in U.S. Pat. No. 4,331,582; using epoxy resins compositions in which the epoxy-group containing compound contains a polycyclic structure, such as in U.S. Pat. Nos. 2,902,471; 3,298,998; and 3,332,908; using epoxy resin compositions in which the curing agent or hardener contains a polycyclic structure; and combining a 9,9-bis(aminophenyl)fluorene with an aromatic epoxy resin as described in U.S. Pat. No. 4,684,678.
Although many of these compositions can be cured to resins having a high glass transition temperature, the cured resins typically are highly crosslinked, and are brittle or have a low ductility. One method of improving the ductility of such cured resins is by adding a rubber component or toughening agent to the composition. However, many compositions containing cured epoxy resins having a high glass transition temperature are incompatible with such toughening agents.
SUMMARY OF THE INVENTION
In one aspect, the invention provides an adhesive composition comprising a mixture of polyepoxide resins comprising cycloaliphatic-containing polyepoxide resin and aromatic polyepoxide resin and an effective amount of 9,9-bis(3-methyl-4-aminophenyl)fluorene. The mixture of polyepoxide resins has a cycloaliphatic character of greater than 10 weight percent, as defined below. The cycloaliphatic-containing polyepoxide resin is present in the adhesive composition in an amount of at least about 20 to about 80 weight percent, based on the total weight of the polyepoxide resins. The aromatic polyepoxide resin is present in the adhesive composition in an amount of from about 80 to about 20 weight percent, based on the total weight of the polyepoxide resins. In another embodiment, the adhesive composition further comprises a toughening agent.
The adhesive compositions of the invention are useful for providing adhesives that rapidly cure to provide adhesive bonds having both high peel strength and high overlap shear strength at room temperature and at 120° C. to 150° C. or higher.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The adhesive compositions of the invention contain at least one cycloaliphatic-containing polyepoxide resin. The cycloaliphatic-containing polyepoxide resins have epoxide moieties attached to, that is, pendent from, only aromatic groups and have cycloaliphatic groups between the aromatic groups. A general formula for such compounds is R(X
n
)—R
1
—(R(X
p
)—R
1
)r—R(X
n
), where each R is independently at least a divalent aromatic group, each X is an epoxide-containing moiety, each R
1
is independently at least a divalent cycloaliphatic group, and p and r are ≧0 and n is at least 1. Examples of such cycloaliphatic groups include the divalent radicals of dicyclopentadiene, cyclopentadiene, norabornane, decalin, and hydrogenated analogs of naphthalene, anthracene, and biphenyl compounds, and combinations thereof. Examples of aromatic groups include mono- and divalent radicals of benzene, naphthalene, bisphenol-A, bisphenol-F, and biphenyl-type compounds, and combinations thereof. The aromatic groups may be substituted, for example, with alkyl groups on the aromatic rings.
In some embodiments, adhesives and adhesive compositions of the invention contain one or more dicyclopentadiene-containing polyepoxide resins. Such resins are generally prepared from the reaction of dicyclopentadiene phenol resin and epichlorohydrin under basic conditions. The detailed preparation procedure can be found in publicly available literature. Examples of useful dicyclopentadiene-containing polyepoxide resins have the formula:
wherein n is an integer from 0 to 7 and may be any integer or fraction in between 0 and 7. Epoxide equivalent weights range from about 150 to about 500. Commercially available dicyclopentadiene-based epoxy resins include HP-7200 from Dainippon Ink and Chemicals, Inc., TACTIX™ 71756 and TACTIX™ 556 epoxy resins, available from Vantico, Inc, Brewster, N.Y.
Cycloaliphatic-containing polyepoxide resin is present in the compositions of the invention in an amount of from 20 to 80 weight percent of the total weight of the polyepoxide resins present in the adhesive composition, and may be present in any whole or fractional amount between 20 and 80 weight percent. In other embodiments, the cycloaliphatic-containing polyepoxide resin is present in the compositions of the invention in an amount of from 25 to 75 weight percent of the total weight of the polyepoxide resins present, and any whole or fractional amount between 25 and 75 weight percent.
Suitable aromatic polyepoxide resins include those containing at least two 1,2-cyclic ethers. Such compounds can be aromatic or heteroaromatic, or can comprise combinations thereof. Suitable polyepoxide resins may be solid or liquid at room temperature. Aromatic polyepoxide resin is used in the adhesives and compositions of the invention to increase the Tg of the cured adhesive film and to provide heat resistance. Aromatic polyepoxide resins do not include polyepoxide resins having both aromatic and cycloaliphatic groups.
Compounds containing at least two epoxide groups (i.e., polyepoxides) are preferred. A combination of polyepoxide compounds may be employed, and an epoxide resin having a functionality of less than two may be used in a combination so long as the overall epoxide functionality of the mixture is at least two. The polymeric epoxides include linear polymers having terminal epoxide groups (e.g., the diglycidyl ether of bisphenol-A) and polymers having pendent epoxy groups (e.g., polyglycidyl ethers of phenolic novolak compounds). It is also within the scope of this invention to use a material with functionality in addition to epoxide functionality but which is essentially unreactive with the epoxide functionality, for example, a material containing both epoxide and acrylic functionality.
A wide variety of commercial epoxide resins are available and listed in “Handbook of Epoxy Resins” by Lee and Neville, McGraw Hill Book Company, New York (1967); and in “Epoxy Resin Technology” by P. F. Bruins, John Wiley & Sons, New York (1968); and in “Epoxy Resins: Chemistry and Technology”, 2
nd
Edition” by C. A. May, Ed., Marcel Dekker, Inc. New York (1988). Aromatic polyepoxides (i.e., compounds containing at least one aromatic ring structure, e.g., a benzene ring, and at least two epoxide groups) that can be used in the present invention include the polyglycidyl ethers of polyhydric phenols, such as Bisphenol-A or Bisphenol-F type resins and their derivatives, aromatic polyglycidyl amines (e.g., polyglycidyl amines of benzenamines, benzene diamines, naphthylenamines, or naphthylene diamines), polyglycidyl ethers of phenol formaldehyde resole or novolak resins; resorcinol diglycidyl ether; polyglycidyl derivatives of fluorene-type resins; and glycidyl esters of aromatic carboxylic acids, e.g., phthalic acid diglycidyl ester, isophthalic acid diglycidyl ester, trimellitic acid triglycidyl ester, and pyromellitic acid tetraglycidyl ester, and mixtures thereof.
Preferred aromatic polyepoxides are the polyglycidyl ethers of polyhydric phenols, such as the series of diglycidyl ethers of Bisphenol-A, commercially available from Resolution Performance Products, Houston, Tex., for example, under the trade designations “EPON 828” and “EPON 1001F
George Clayton A.
Schultz William J.
Thompson Wendy L.
3M Innovative Properties Company
Aylward D.
Bardell Scott A
Dawson Robert
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