Note: Descriptions are shown in the official language in which they were submitted.
~093/20123 2 1 3 3 8 3 9 PCT/US93/02677
,~ .; , .
A HIGH PERFORMANCE EPOXY BASED LAMINATING ADHESIVE
t
. ~! .; .,
CROSS-R~FERENCES
This application is a continuation-in-part of
Application Serial No. 07/483,266, by Thomas F. Gardeski
and Diane G. No~ak, filed February 15, 1990, which is, in
turn, a con~inuation of Application Serial No.
5 07/153,141, by Thomas F. Gardeski and Diane G. Novak,
filed February 8, 1988, and now abandoned, both of which
are also entitled "A High Performance Epoxy Based
aminating Adhesive." These two applications are hereby
incorporated in their entirety by this reference.
1 0
BACKGRO~N~ OF THE INVENTION
This invention is direted to three-dimensional
:
~ polymeric adhesive materials and m~thods for producing
.
~ 15~ uch materials.
,
During the past quarter century, the rapid
growth of~the electronic circui~s industry has resulted
in the de~elopment of higher performance construction
:
materials. However, ~he development of high performance
:'
adhesive materials and systems to bond the construction
materials together has not kept pace. This lack of
higher performance adhesive materials is particularly
:
2133`83~
WOg3/20123 PCT/US93/02677
felt in the assembly of electronic components for use in
se~ere environmental conditions, such as under-the-hood
automotive and military applications. Adhesive materials
and~systems that are currently available mee~ some of the
requirements for such properties as peel strength,
chemical resistance, moisture resistance, high
temperature stability, dimensional stability, especially
in the Z-axis direction, and ease of processing.
~; ~ However, these~materials and systems typically fail to
10- meet one or more of these requirements. Therefore, a
need exists for an adhesive material that meets all of
; ~ the rèquirements~for use under severe environmental
conditions while;~retaining ease of application.
; We have~developed a three-dimensional adhesi~e
terial~;and a process~for preparlng it that meets these
needs and provides~an improved adhesi~e for use under
20~ se~ere~en~ironment;al~conditions, particularly in the
assembly~of electronic components.
~ ~ :
One aspect of the present invention is a
process~for produclng a three-dimensional polymeric
adhesive material.~ The process comprises:
reacting a starting polymer containing an
active hydrogen or hydroxy function with a polyfunctional
~ ~ucleophile to form an adduct product; and
:;` ~:: :
~ ~0~3/201~3 ~13 ~B.~ Q . . PCT/US93/02677
(2) reacting the adduct product with a
polyelectrophile ~o generate a three-dimensional
polymeric adhesive material.
The starting polymer can contain an active
hydrogen and ha~e a maximum acid ~alue of 2. Such a
starting polymer can be selected from the group
consisting of polycarboxylic acids, polyesters,
polyamides, polyacrylics, polyfunctional phenolic resins,
: 10 and mixtures thereof. Preferably, in this alternative,
the starting polymer is a high molecular weight
polyester.
~ Alternatively, the starting polymer can be a
: 15 po~y~unctional hydroxy-containing polymer having a
hydroxy number o~:at least 10. Preferably, the
polyfunctional hydro~y-containing polymer is selected
from the group consisting of polyols, polyesters,
:
. : polyurethanes, and mixtures thereof.
: 20 ~ ~
; ~ Preferably, the polyfunctional nucleophile is a
;~ polyfunctional~nitrogen-containing compound. More
~, preferably, the polyfunc~ional nitrogen-containing
compound is æelected from the group consisting of
25 ~ polyamines, polyazir1dines, polyisocyanates, and mixtures
thereof. Most preferably, the polyfunctional nitxogen-
: containing co~pound is a polyisocyanate.
~ .
~; ,
W O 93/20123 ~ ~ ~ PC~r/US93/~2677 `
Preferably, the polyelectrophile comprises at
: least one polyepoxide~ More preferably, the polyepoxide
is selected from the group consisting of bisphenol A-
~ ~ epichlorohydrin epoxies, novolac epoxies, and mixtures
; 5 thereof. Most preferably, the polyexpoxide comprises a
mixture of bisphenol A-epichlorohydrin epoxies and
novolac epoxies.
Preferably, when the polyelectrophile comprises
at least:one~polyepoxide, the step of reacting the adduct
: product with ~:he at least one polyepoxide comprises
heating a mixture of the adduct product and the at least
o~e polyepoxide~to;a~temperature between about 250F and
about 400~F.
;` Preferably~ when a high molecular weight
polyéster:and~at~least~one:polyepoxide are uæed to form
the~three-dimen~ional~polymeric material, the high
; molecular~weight~polyester~comprlses fr~m about 50- to
2a ;~ about~90~ by~weight:~of:the~three-dimensional polymeric
::adhesive:material~and~the polyepoxide comprises from
about~10% to~.~about~50% by weisht of the three-dimensional
: . polymeric adhesive material.
25 ~: Another aspect~of:the~:present invention is a
process for bonding at least two substrates. The process
comprises the steps of:
(1) reacting a starting polymer containing an
~$o 93/~123 ~ g~ PCT/US93/02~77
active hydrogen or hydroxy function with a polyfunctional
nucleophile to form an adduct product;
(2) mixing the adduct product with a
polyelectrophile to generate a bonding precursor;
(3) applying the bonding precursor between ~he
substrates prior to the reaction between the adduct
product and the polyel ctrophile; and
(4) reacting the adduct product with the
polyelectrophile to generate a three-dimensional polymer
adhesive material between the substrates, thereby bonding
the substrates.
Typically, ~he substrates are selected from the
group consisting of film substrates, foil substrates, and
: 15 ~ hardboard ~ubstrates.
Another aspect of the present in~ention is a
three-dimensional;adhesive produced by the process
described above~. In general, the adhesive comprises:
2~ at least two linear:polymer moieties, each
,
moiety cornprising a~polymer containing nucleophilic
nitrogen at~ms capable of react1on with an electrophile
and
(2) cross-l~inks between the nitrogens of the
polymer moieties; each cross-link comprising a polymer
linked to the nitrogen atoms of the polymer moieties
:~ through reaction o~ an electrophile with the nitrogen
: atoms.
WO 93/20123 ~3~39 PCT/US93/02677
Preferably, the linear polymer moieties are
selected from the group consisting of polycarboxylic
acids, polyesters, polyamides, polyacrylics,
: polyfunctional phenolic resins, and mixtures thereof.
Preferably, the linear polymer moieties are
~; formed by reac~ion of a hydroxy-containing polymer with a
polyfunctional nitrogen-containing nucleophile.
: ~ '
Preferably, the polyfunctional nitrogen-
containing nucleophile:is selected from the group
consisting of polyamines, polyaziridines,
: : :
polyisocyanates, and mixtures thereof.
:15 One preferred versio~ of the three-dimensional
polymeric adhesive of:~he present in~ention comprises:
at least two linear urethane linked
polymer moieti~es, each moiety comprlsing a hydroxy-
termina~ed polyester linked in urethane linkage by an
::: :~ : :
~ 20 aromatic isocyanate; and
- : :
(2) ~ross-links between ~he ~itrogens of the
; urethane linked polymer moieties, each cross-link
comprising a phenyl-containing polymer linked to the
: : nltrogen at~ms of the urethane linkages by -CH2-CHOH-
,
:25 linkages, with ~he methylene groups of the linkages being
: bonded directly to the nitrogen atoms such that the
ross-links form a three-dimensional polymeric structure.
:
-- ,
0 g3/20123 ~ P~/~JS93/iD2677
In this version, the cross--links preferably
comprise at teast one polyepoxide selected f rom the group
consisting of bisphenol A--epichlorohydrin epoxies,
novolac epoxies, ~nd mixtures thereof.
s
More preferab.y, the polyepoxide comprises a
mixture of bisphenol A-epichlorohydrin epoxies having the
formula
CH2--CH--CH2~0~¢~0CH2--CH--CH230~¢~-ocH2--CH--CH2
CH3 3CH
~ ~ ~ and novolac epoxies having the formula
:~ /o\
15 ~ :CH2--CH--CH2 o~CH2 ~ CH2~o--CH2--CH--CH2
wherein n is an inte~er from 1 to about 20, n being
~:: :
independently chosen for the bispheno~ A-epichlorohydrin
:
epoxies and: ~or the novolac epoxies.
The adhesive material of the present invention
can be used to bond at lecst two substrates, thereby
' forming a ~omposite structure. A composite structure
formed cccording to the invention comprises:
:~ :
: : 25 (l ) :at least two bondable substrates; and
(2) a three-dimensional polymeric adhesive
material in adhesive contact with each o~ the substrates
such that each of the substrates is bonded to at least
SUBSTITUTE SHEET
W093/20123 b~3~ PCT/US93/02677
one other substrate by the adhesi~e material, the
adhesive material comprising:
(a) at least two linear polymer moieties,
each moiety comprising a polymer con~aining nucleophilic
nitrogen atoms capable of reaction with an electrophile;
and
(b) cross-links between the nitrogens of
~ the polymer moieties, each cross-link comprising a
: polymer linked to the nitrogen atoms of the polymer
: 10 moieties through reaction of an electrophile with the
nitrogen atoms.
, .
DESCRIPTION
`15 I. The Adhesive Production Process
i ::
One aspect of the present inv~ntion is a
process for producing~a three-dimensional polymexic
adhesive material. The polymeric adhesive material
produced by this~process has impro~ed peel strength,
chemical reslstance, moisture resistance, high
; : temperature.stability, and dimensional stabili~y. It is
easy to process and is particularly suitable for use with
electronic construct1on materials, such as printed
circuit boards. ~In general, this process comprises:
~,
1) reacting a starting polymer containing an
active hydrogen function or hydroxy func~ion with a
polyfunctional nucleophiIe to form an adduct product; and
,10g3~20123 ~ t ~ ~ PCT/US~3/02677
f.J ~ ~ ~ V d ~
~ 2) reacting the adduct product with a
polyelectrophile to generate a three-dim~nsional
polymeric adhesive material.
S The starting polymer can contain an active
hydrogen, with a maximum acid value of 2. Such polymers
can be polycarboxylic acids, polyesters, polyamides,
polyacrylics, polyfunctional phenolic resins, or mixtures
: thereof.
Alternatively, the starting polymer can be a
polyfunctional hydroxy-containing polymer having a
hydroxy number of at least 10. The poly~unctional
hydroxy-containing pol~mer can be a polyol, a polyester,
:
a polyurethane, or a mixture thexeof.
Preferably, the:starting polymer is a high
: molecular weight polyester with hydroxyl end-yroup
fun~tionality of the alcohol type.
20;
: The~ polyfunctional nucleophile can be a
~: polyfunctional nitrogen-containing:compound. Such
:' compounds include polyamines, polyaziridines,
polyisocyanates, and mixtures thereof. Preferably, the
polyfunc~io~al nitrogen-containing:compound is a
:
polyisoGyaLnate~
A particularly suitable starting polymer is a
::
:
WO93/2~123 } ~ 3g P~T/VS93~2677
polyester resin such as DuPont 49002 base. A
particularly suitable polyelectrophile is a
polyfunctional isocyanate sold by Mobay Chemical Corp.,
Pittsburgh, Pennsylvania, under the name of Mondur MRS,
which is a polymethylene polyphenylene ester of isocyanic
acid.
Carbon atoms of alkyl and/or aryl moieties
within the starting polymer or polyfunctional nucleophile
can be optionally substituted with methyl and/or C2-C5
: : :
alkyl. The terms "starting polymer" and "polyfunctional
nuc~eophile", as used herein, include compounds
optionally substituted with methyl and/or C2-C5 alkyl.
The rea~tion of the starting polymer with the
~: , :
po~yfunctional nucleophile takes place slowly at room
temperature and takes place more rapldly at about 250F.
Typically, this: reaction is performed in a solvent, such
as a 90~:10~ mixture of methylene chloride:cyclohexanone.
: :
~ ~ .
The;second~stage of the process comprised is
reacting the adduct product with a polyelectrophile to
generate the three-dimensional polymeric adhesi~e
material. The polyelectrophile is preferably a
25 ~ polyepoxide. More preferably, it is a polyepoxide
selected from the group consisting of bisphenol A-
epichlorohydrln epoxies, novolac epoxies, or a mixture
thereof. Most preferably, the polyelectrophile is a
'
::
~093/20123 ~ 3~9 P~/USg3/0~677
mixture of a bisphenol A-epichlorohydrin epoxy, such as
Celanese Epi-Rez-5132, and a novolac epoxy, such as Dow
DEN 438. The bisphenol A-epichlorohydrin epoxy has the
following structure:
CH/2--\CH--CH2~0~C~OCH2--CIH-CH230~C~ocH2--CH--CH2
:: CH3 c~3
:
~: 10
wherein n is an integer fron~ 1 to about 20. The novolac
epoxy has :the f ollowtng structure:
;, : : .
: OCH2--GH--CH2 /\
CH2--CH--CH2--0~cH2~cH2~0--CH2--CH--CH2
wherein n is an integer from 1 to about 20. The vaîues
o~ n are~: independently chosen for the bis-epi and novolac
epoxies.
: 2:0~
Preferably, when a high molecwlar weight
polyester and at least one polyepoxide are used to form
the three-dlmensional polymeric material, the high
~ .
molecular weight ~polyester comprises f rom about 5070 to
25 about 90% by weight of the three-dimensional polymeric
`: adhesive rnaterial and the polyepoxide comprises ~rom
~ ::
about 10% to about 50% by weight of the three--dimensional
polymeric adhesive material.
SUBSTITUTE StlE~ET
WO 93/20123 ~3g j PCI/US93/02677
The reactivn of the adduct product and the
polyelectrophile preferably takes place at a temperature
from about 250-F to about 400-F. The first ond second
stage reactions are depicted below:
1 st Stage:
H(R)xH + OCN-[c6H4(cH2)]n-Nco
. O
~O(R)x-o-cN-[c6H4(cH2)~n-Nco
H
where R represents the ester repeat unit and x,
represents the number of ester repeat units and
:
n represents the number of organic aromatic
repeat units in th~e isocyanate component.
5 ~ 2nd Stage: :
O(R)XO--CN~C6 H4(CH2 ) ~n ~ CI~/CH--R-CH\--CH2
epoxy
t
--O(R)xocN~c6H4(cH2)~n
H-C--H
: H--C~H
H--C--OH
H--¢--H
O~R)xOC--N~C6H4(CH2)~n
$lJlBS~lT~T~
~093/20123 ~1 3 3 ~ 3 9; I. PCT/US93~02677
13
The pxessure at which the reaction occurs is
generally not critical. The reaCtion typically takes
pla e at atmospheric pressure.
: 5
The reaction typically occurs in an aprotic,
moderately polar solvent or a mixture of such solvents.
Exemplary solvents are~a mixture of:methylene chloride
and cyclohexanone or methyl ethyl ketone, or a mixture of
methylene chloride~and cyclohexanone together with methyl
ethyl keto~e. However, suitable solvents are not to be
limited to these combinations; the choice of solvent i5
generally:~not;~crltlcal.~ ~
~1};. U~e~of the Adhèsiy~for Bondinq
The process~ of;~producing:the adhesive of the
presént invention:~can:~be incorporat;ed into a process for
bond:ing at least~two~substrates. In general, this
~ ;20~ b~ondin~process~compris~e~s of the steps of:
s~ reacting a~starting polymer with a
polyfunGtional nucleophile 'co ~ forrn~ an adduct product, as
:~ :
described above;
2)~ mixlng the adduct product with a
Z5 ;~polyelectrophile to~generate a bonding precursor;
(3) applying the bonding precursor between the
:substrates prior to~a reaction between the adduct product
and the polyelectrophile; and
::: :
:: :
, ~
.
W O 93/20123 i l ' ' 9 14 P(~rIUS9~102677
(4) reacting the adduct product with the
polyelectrophile to generate a three-dimensional
polymeric adhesive material between the substrates,
thereby bonding the substrates.
The substrates used for this procedure can be
film æubstrates, foil substrates, or hardboard
:
substrates. A typical example of a film substrate is
polyimide film. The substrates can be of the same
materials or different materiaIs. The substrates can be
electronic circuit boards or other electronic structural
components.
III. The Adhesive Compound
Another aspect of the invention is an improved
three-dimenslonal polymeric adhesive material comprising:
(l) at~least~two linear polymer moieties, each
moiety~ comprising a polymer containing nucleophilic
nit~rogen atoms cap~ble of reaction with an electrophile;
and
) cross-links between the nitrogens of the
~; polymer moieties, each cross-link comprising a polymer
linked to the nitrogen atoms of the polymer moieties
through reaction of an electrophile with the nitrogen
atoms.
~ ~ 1 3 3 ~ ~ ~
WO93/20123 - . PCTIUS93/02677
Preferably, the adhesive comprises:
(1) at least ~wo linear urethane linked
polymer moieties, each moiety comprising a hydroxy-
terminated polyester linked in urethane linkage by an
aromatic îsocyanate; and
(2) cross-links between the nitrogen of the
urethane linked polymer moieties, each cross-link
comprising a phenyl-containing polymer linked to the
nitrogen atoms of the polyurethanes by -CH2-C~OH- linkages
~: : 10 with the CH2 moieties being located adjacent to the
nitrogen atoms.
:
: ~:
As dis1Osed above, this adhesive material can
be formed in_situ for bonding at least two substrates.
: 15: The substrates can bé film substrates, foil substrates,
: or hardboard substrates.
When~;at least~two: or more substrates are bonded
by the adhesi~e;of the present invention, a compo~ite
material can ~e formed. The composite material
: comprises: :
~ ~ .
(1) at least two bondable substrates, and
~2) the three-dimensional polymeric adhesive
material o the:present in~ention ln adhesive contact
~ with each of the:substrates such that each of the
: substra~es lS bonded to at least one other substrate by
:~ the adhesive material.
~ ~:
.
W O 93/20123 ?,~ ` . P(~rJUS93/02677
~ ~839
~ 16
The invention is illustrated by the following
example. The example is for illustrative purposes and is
not to be construed as limiting the scope of the
vention in any~manner.
; An example of the adhesive material of the
present invention includes the following components:
10~ :(1) a~polyester resin having a solids content
~;~ of 1~7-20~ comprised of:Dupont 49002 bàse in a solvent
mixture of 90~::10% ~(w/w) methylene chloride:
;cyclohexanone;~
2~ àn~epoxy~;novolac at~85~ sollds content
l5;~ composed~of~Dow DEN 438-EK85 in~methyl ethyl ketone;
: (3)~ a~bis~-epi;epoxy~composed of Celanese Epi-
Rez~ 5132 ~at :100~solids content; and
4)~ a~polyfunctional isocyanate used as a
cu ~ tivé~co ~c ent~,~Mondur: ~ S~from Mobay Chem~ical Co
The Gomponents can~be~:combined according to
either~of the~following two procedures:
The~adhesive coating composition is made
by adding:8~0~ by solids~:of the~polyester c~omponent, 10~
25~ by~solids~of~the~epoxy~novolac,;10~by solids of the bis-
::;epi epoxy, and~1.2~ parts by weight~:of the~:isocyanate in
an open container~wlthout agltation~. The composition is
: : : then agi~tated well for 1 to 5 minutes. The container is
~-~"~
WO93/20123 2 1 3 3 8 3 ~ PCT/US~3/02677
then capped with an airtight lid for 30 minutes to allow
for the onset of the isocyanate/polyester reaction.
(2) The polyester and isocyanate are combined,
thoroughly mixed, and then allowed to stand at room
temperature for a minimum of 30 minutes prior to the
epoxy addition to allow onset of the isocyanate/polyester
reaction.
; The adhes1ve coating composition is then
applied by means of the reverse roll coating technique to
a l mil polyimide film to yield a 1 mil dry coat weight.
Drying (i.e., remova1 of the sol~ents) is accomplished
through a 75-foot, 3-zone oven at 212F and 25 feet per
minute. The coated substrate is then positioned nex~ to
the treated~side of~a l ounce copper foil, where the
copper~foi1 surface i8 treated with Oak CMC-lIl compound
to enhance bondability. The polyimide film and copper
foil~are~heated~to~a temperature of 225F to 400F with
an applied pres~ure of 80 psi (pounds/square inch) to 120
ZO ~psl through~a~coater/1aminator combining station as part
of a continuous~operat1on. The resulting roll is brought
onto a six inch~core, left at room temperature for l to 7
days, then post cured as follows: 2 hours at 150F, 2
hours at 275F, and 2 hours at 350F.
~ ,
: : :
A composite structure was prepared according to
the first of the abov~ procedures. The resulting
composite structure e~hibited the properties shown in
:
WO93/20123 ~ 21~ 3 8 ~ 9 PCT/US93/02677
18
Table 1 when tested per A~SI/IPC-FC-232B and 241B
procedures:
TABLE 1
PROPERTIES OF ADHESIVE COMPOSITE STRUCTURE
Initial Peel 20 plia
Peel After Solder 21 pli
Chemical Reslstance:
: Methyl Ethyl Ketone 21 pli
Toluene 20 pli
~Isopropyl Alcohol 21 pli
Trichloroethylene/Methylene Chloride 21 pli
Solder~ Float : Pass
Aging (96 hours at ~ ~o Bond
2~75F~in~:air circulating oven) Strength Change
pli -~:pounds per~linear inch
ADVANTAGES OF THE _~y~N~
,
::
The`present invention provides an adhesive
system with extremely balanced properties and the added
5 :~ benefit of superior Z-axis stability through a unique
:: :~ : : : :
curing mechanism. More specifically, the present
in~ention provldes an epoxy-based laminating adhesive
~: that can be cqntinuously processed and cured without the
:: :
~:
: :
3 1! ~ 1 ~ 3 ~ ~9
WO93/20123 rCT/US93/0~677
19
evolution of byproducts to pro~ide a flexible bond-ply
with superior overall properties, including excellent Z-
axis stability. The adhesi~e material is applicable to
film substrates such as polyimide, foi~ substrates such
as copper, and hardboard substrates, such as FR4
(fiberglass impregnated hardboard). The adhesive of the
present invention also possesses superior peel strength,
chemical resistance, moisture resistance, and temperature
~: stability. It is particularly suitable for use in the
:.
~10 bonding of electronic construction materials, such as
: those intended for use in severe en~ironmental
conditions. In particular, the adhesive of the present
inv-ntion is~suitabl~e~for use in under-the-hood
automotive and military~appl1cations.
Although~the present invention has been
described in~cons~iderable detail with reference to
certa~in~preferred~versions thereof~, other versions are
pQssib1e~ Therefore~the spirit~and scope of the pending
2~0~ :claims:~::shou1d not be limited to the description of the
preferred versions contained~herein.
:~ :~ : :,
