Note: Descriptions are shown in the official language in which they were submitted.
~1~73S~!:
This invention relates to a rnethod for coating sur~aces and particularly
to a method for adhesively bonding surfaces such as tread members to shoe
uppers .
An important requirement in the attachment of tread members such as
outsoles to shoe uppers is that the adhesive mus-t be applied in a fluid condition
to enable it to wet and effect limited penetration of the surfaces to be joined.
It is also important that the adhesive become tough and strong thereafter.
The initial fluidity has been secured by the use of volatile organic solvent
10 solutions of adhesives where the development of strength and toughness after
application was achieved by evaporation of the solvent. However, solvent
type adhesives require a time delay for drying of the adhesive and present
fire and health hazards from the solvent vapors.
~ ot melt adhesives have been used with some success; but the need
for relatively high temperature to bring the adhesive viscosity to a low enough
value for wetting adhesive engagement with the surfaces has created problems
both with degradation of the adhesive and in some instances harm to the surfaces
to be bonded. Additionally, the relatively short open time has imposed undesirably
rigid time requirements in the assembly of surfaces with the adhesive still
in fluid condition.
It is an object of the present invention to provide a method for coating
or bonding surfaces using a coating material which is initially fluid at relatively
low temperatures to enable it more readily to enter into wetting adhesive engagement
with a surface and which is convertible by relatively mild treatment to a tough,
solid but heat softenable condition capable of establishing substantially immediate
strong adhesive union with a compatible adhesive or resin surface.
To this end and in accordance with a feature of the present invention,
a polymeric urethane containing reactive -NCO groups and crystalline segments
in the polymer molecule and having a relatively low crystalline melting point
.
1 01773S2
is coated on ~ surface at a relatively low temperature at which
it is freely fluid for entering wetting adheqive engagement with
that surface. The coating of the urethane material is converted
to tough solid condition by reaction with a chain extender
containing a compound having active hydrogens reactive with
the-NC0 groups of the urethane. The chain extended coating
may be assembled in heat softened condition against a compatible
surface to be joined to the first mentioned surface to establish
adhesive engagement and thereafter cooled to tough strong
condition.
The invention relates to the method comprising the
steps of bringing a normally solid polymeric urethane to fluid
form, applying said urethane as a coating to a surface of an
article, said urethane containing reactive ~NC0 groups and
comprising segments having a crystalline melting point of from
about 40C to about 90C, the reactive -NC0 groups in said
urethane being in proportions to form after chain extension
polymeric polyurethane which is viscoelastic when heated above
said crystalline melting point, solidifying and crystallizing
the urethane of said coating, thereafter bringing a compound
providing active hydrogens into contact with said urethane
coating at temperatures at which the solidified urethane coating
is not distorted and reacting said compound with said -NC0
groups to chain extend said polymeric urethane, heating said
chain extended polyurethane to a temperature above its crystalli-
ne melting point to bring it to heat softened viscoelastic
condition, pressing said heat softened viscoelastic chain-
extended polyurethane against a coating of heat activatable
adhesive compatible with said chain-extended polyurethane on
the attaching surface of a second article said heat activatable
adhesive comprising a polyurethane having reactive -NC0 groups
~)773S;~
and thereafter cooling said chaln-extended polyur~thane to tough
strong condition bon~ing said second article to said ~irs-t
mentioned article.
Reference is made to the attached drawings forming
part of the disclosure of the present case in which:
FIG. 1 is a diagrammatic angular view with parts
broken away of an outsole cementer disposing a band of adhesive
on the attaching margin of an outsole.
FIG. 2 is a diagrammatic elevational view showing acti-
vation of the adhesive on an outsole and show upper by radiantheating, and
FIG. 3 is ~ diagrammatic elevational view showing the
bonding of an outsole to a show upper in a sole attaching press.
The method of the present invention is primarily useful
in adhesive bonding, particularly in bonding tread members to
shoe uppers, and will be described with particular relation to
this use. However, in some of its aspects the method is also
useful in coating and bonding other surfaces such as wood,
resinous or rubber materials, metal and fabrics and in reinforc-
ing and stiffening sheet materials, for example, in stiffeningthe toes or counters of shoes.
As shown in FIG. 1, use of the adhesive in the
process of cement outsole attaching may include the application
of a band 10 of the urethane adhesive in fluid condition on
the attaching margin of an outsole 12, preferably by an outsole
cementer 14. The outsole cementer 14 comprises a nozzle 16 for
applying
,~
..
.
73~
and spreading the adhesive, a drive wheel 18 for moving the outsole 12 at a
desired rate passed the nozzle 16 and a guide 20 for maintaining the margin
of the outsole 12 in desired relation to the no~le 16. As shown in FIG. 1, the
cementer applies a band 10 extending around at least the forward portion of
the outsole 12, but the band 10 may extend around the entire margin of the
outsole depending on the shoe construction involved.
The same or other compatible adhesive may also be applied to the attaching
surface of the bottom of a shoe upper.
The deposited urethane adhesive is then subjected to moisture, suitably
in a steam cabinet or other device for providing moisture, and preferably,
limited heating to the deposited adhesive to effect chain extension of the adhesive.
After chain extension of the adhesive, completion of the sole attaching
process involves (see FIG. 2) disposing the outsole 12 and a shoe upper 22
having adhesive on the attaching surface 24 on the bottom of the shoe upper
on a rack 26 spaced from a radiant heating unit 28 to warm the adhesive to
a temperature above its crystalline melting point and bring it to viscoelastic
condition. After heating of the adhesive on the bottom of the shoe upper 22
20 and on the outsole 12, the outsole 12 is positioned on the bottom of the shoe
upper 22 and the assembled outsole 12 and shoe upper 22 are placed in a sole
attaching press 30, (see FIG. 3) and subjected to sole attaching pressure.
The present method gives novel advantage~s through the ordered sequence
of the development of physical properties resulting from temperature and chemical
actions on the adhesive coordinated with the crystalline properties of segments
of the resin and the relatively low molecular weight of the adhesive. The adhesive
may be brought to liquid form for application either by heating it to molten '
condition or by addition of a solvent.
Where the adhesive is applied in molten form, it requires only a temperature
above the crystalline melting point of the resin segments to give it the Eluidity
:~07735'~
needed for wetting aclhesive engagement with a surEace to be bonded. The
term "crystalline melting point" is the temperature at which crystalline segments
of the polymer melt and is determined as the temperature of the major endotherm
peak in a differential thermal analysis. When the polymer is brought above
this temperature in activation, the crystalline segments melt and cause softening
of the polymer coating or film. After application, the adhesive is brought
below that crystalline melting point and is al:Lowed to crystallize to develop
a resistance to flow and distortion at temperatures used in the succeeding step.
The adhesive may also be brought to liquid form by dissolving it in an
inert volatile solvent for application at room temperature or at slightly elevated
temperatures. Solvents which may be used are volatile organic liquids which
do not contain active hydrogen. Among those which have been employed are
xylol, toluene~ dimethyl formamide, acetone, methyl ethyl ketone, ethyl acetate,
cellulose acetate, methylene chloride and mixtures of these. Particularly useful
solvents have been mixtures of toluene with up to about 85% by weight based
on the weight of the solvent mixture of methylene chloride or methyl ethyl
ketone. Because OI the nature of the urethanes employed in the present method,
relatively high solids content solutions, for example, 60% by weight and higher
have viscosities low enough for application in wetting engagement with surfaces.
Also, smaller percentages of solvents may be useful where it is desired to
apply the urethane material at moderately elevated temperatures below temperatures
needed to melt the urethane in the absence of solvents. If the adhesive applied
is a solution, the solvent is evaporated off before subsequent treatment.
That step following the formation of a coating of the adhesive is the reaction
o~active isocyanate-groups of the adhesive at warm or moderately elevated
temperatures with a chain extending agent providing at least two active hydrogens
such as water vapor or steam or similar chain extending agents to bring the
adhesive to a tough flow resistant, but heat softenable condition. In chain
--4--
, ,
~07~35'~
extended state, the crystalline melting point i8 substantially unchanged from
that of the original urethane adhesive so that when heated above the crystalline
melting point the chain extended adhesive becomes viscoelastic, namely, somewhat
rubbery, but deformable and tlowable under pressure and is tacky and capable
of adhesive union with a compatible surface such as a wood, metal, or Eabric
surface coated with the same or a compatible adhesive or with a resin e . g .
vinyl resin, surface. By reason of the viscoelastic condition and the somewhat
rubbery physical state of the chain extended adhesive at temperatures above
10 its crystalline melting point, bonds established by contact of the adhesive
surface with another surface have very high initial bond strength so that,
for example, in assembly of a shoe sole and a shoe upper, tendency of the
sole to separate from the upper because of the springiness of the sole is prevented.
The adhesive which develops the successive advantageous physical
states under the successive physical and chemical treatments is based on a
polyurethane having reactive -NCO groups, suitably an -NCO terminated prepolymer
from reaction of a relatively low molecular weight polyol having a crystalline
melting point in the range of from about 40C . to about 90C., preferably from
about 40C. to 65C. with an excess of diisocyanate.
Suitable polyol materials include the hydroxyl terminated polycaprolactones
and polyesters of 6 to 12 carbon atom aliphatic dicarboxylic acids such as sebacic,
adipic, azelaic, suberic and dodecanedioic acids with, preferably even numbered,
glycols having from 2 to 6 carbon atom chains such as 1,4-butanediol . The
~ acid component of the polyester polyol may include from about 5% to about
- 25% on a molar basis of cycloaliphatic acid such as 1,4-cyclohexane dicarboxylic
acid or 1, 2-cyclohexane dicarboxylic acid to promote adhesion particularly
to resin-rubber surfaces and from about 5% to about ~5% on a molar basis of
aromatic dicarboxylic acid such as terephthalic acid or isophthalic acid to
improve resistance to plastici~ers. The glycol component may include from
--5--
. . .
.:, ' ,
~0773~
about 5O to about 15% on a molar basis o~ diethylene glycol or cycloaliphatic
glycols such as 1,4-cyclohexane dimethanol to improve tack and wetting proper-ties
and give better reactivity with water vapor. These polyols should have a
molecular ~,veight in the range from about 1, 000 to about 10, 000 and preferably
from about 2,000 to about 4,000.
The polyurethane material for application to the surface to be bonded
is made by reaction of one or more of -the above polyols with a diisocyanate
in proportions to give an -NCO to -OH ratio in a range from about~5 to about
10 3Ø Any of the available diisocyanates may be used including tolylene diisocyanate,
diphenylmethane diisocyanate, dicyclohexyl methane diisocyanate. The polyurethane
material is preferably made without the use of a catalyst and it is desirable
to include a stabilizer such as an acid chloride, for example, benzoyl chloride,
acetyl chloride or sebacoyl chloride in amount of from about 0 . 05% to about
0. 2% by weight of the polyurethane material .
It has been ~ound that polyurethanes formed using diphenylmethane
diisocyanate, react with water much more rapidly than do polyurethane materials
from reaction using tolylene diisocyanate; but that the latter polyurethane
materials are more stable on storage. Improved storage stability coupled with
rapid reaction rate may be obtained by a combination of both diisocyanates.
Because of the differences in rate of reaction, it is preferred to add the tolylene
diisocyanate first and allow it to react for a limited time which enables the
-NCO group in the para position to react with the polyol, after which diphenylmethane
diisocyanate may be added. Useful ratios of these diisocyanates may be from
equal parts on a molar basis to 80 moles of diphenylmethane diisocyanate with
20 moles of tolylene diisocyanate.
The speed of the chain extension reaction of the urethane layers may
be increased by the use of catalysts. Where chain extension is effected by
moisture, tertiary amines such as N-methyl morpholine, triethylene diamine
,: :
S;~
and other known catalysts such as dibutyl tin dilaurate and stannous swlfate
may be incorporated in the urethane material. In general, amounts of catalyst
from about 0 . 05% to about P6 by weight, basecl on the weight Oe the urethane
may be used.
While the urethane forms an excellent adhesive or coating by itself,
it may be desirable to include other materials æuch as plastici~ers, fillers and
tackifiers. Plasticizers, particularly normally solid plasticizers, are of value
both to reduce the viscosity of the urethane when in hot molten condition and
10 to modify the properties of the final film. Among plasticizers useful with the
urethane are dicyclohexyl phthalate, triphenyl phosphate, diphenyl phthalate
and cycloaliphatic epoxies such as monomers of the Bisphenol-A type.
Tackifiers effective to improve the establishment of adhesive relation
include tackifiers of the hydrocarbon type such as the terpenes e . g. alpha-
and beta-pinene polymers, low molecular weight styrenes such as polyalphamethyl
styrene, and rosin esters.
Also inert fillers in general such as clays, carbonates, titanium dioxide
and others may be included in the urethane compositions.
Reaction of the diisocyanate with the polyol has been found to raise the
crystalline melting point only a few degrees above the crystalline melting point
of the polyol itself. For example, a butanediol sebacate polyol may have a
crystalline melting point of 49C., and the polyurethane from reaction of this
polyol with diphenylmethane diisocyanate in a ratio of 1. 5 -NCO to 1 -OH will
have a crystalline melting point OI only 54C.
The polyurethane material may be applied in fluid condition to a surface
such as the sole attaching surface on the bottom of a shoe upper or the attaching
surface of an outsole by conventional applicator means or even by hand. Relatively
low application temperatures, for example, temperatures of 80C. to 100C.,
have been found usefi,ll with solvent-free polyurethane materials having crystalline
. . .
' ~
3~773~
melting points as high as about 70C. Solvent containing polyurethane compositions
may be applied at room temperature or at slightly elevated temperatures.
It is desirable that the thickness of coatings of the urethane material
be uniform in order that the action of the chaln extending agent over the whole
extent of it and throughout, thickness of the urethane coating or filler be uniform.
It is preferred that the coating be from about l to about 5 mils in thickness
for most satisfactory and uniform chain extensions throughout the thickness
of the coating. Relatively thin coatings which may be as thin as 0. 001" are
10 effective on relatively regular surfaces such as the attaching surface of an
outsole, and coatings as thin as 0 . 003" may be applied to more irregular surfaces
such as the sole attaching surface on the bottom of a shoe upper.
After deposition of the polyurethane, the material of the coating is preferably
allowed to crystallize before being subjected to chain extension. That is,
the development of crystallinity serves to resis-t distortion through flow of
the deposited material under the higher temperatures to which the coating
is subjected in the chain extension step.
To bring the deposited polyurethane to the desired state for bond formation,
it is subjected to a chain extension treatment involving exposing the surface
of the coating to a compound having two active hydrogens for reaction with
the -NCO groups of the polyurethane. A preferred chain extension agent is
water, preferably in the form of vapor or steam, for example, in a high humidity
room or in proximity to a steam or vapor source. Other chain extending agents
such as diamines or glycols may also be used. It is preferred to use temperatures
somewhat above room temperature for the chain extension step and temperatures
from about 90F. up to about 190F. at a relative humidity of from about 50%
to about 95% have been found effective to insure chain extension at reasonable
speed, e . g. from about 10 to about 30 minutes, without distortion of the urethane
coating. The chain extension reaction should be carried to on extent at which
--8--
. . .
` '
3~;~
the film becomes elastoplastic on heat activation, but not markedly cross-linked,
i . e . the film is still soluble or attacked by active polyurethane solventa such
as dimethyl formamide or tetrahydrofurane.
After chain extension, and elimination of free water or other chain extending
agents from the surface of the urethane coating, the coating may be heated
to bring it to actively adhesive condition. Radiant heating is preIerred but
other forms of heating such as convective heating may be used. The heating
should be such as to bring at least the surface of the urethane coating rapidly,
10 preferably within about 15 to 30 seconds, to a temperature above the crystalline
melting point, preferably to a temperature in the range of from about 120F.
to about 180F. so that at least the surface is in a viscoelastic condition capable
of adhesive union with a compatible surface such as a vinyl resin or adhesive
layer on the article to be bonded to the coated surface. Using urethanes with
crystalline melting points up to about 158F., excellent bonds have been obtained
with attaching temperatures as little as 9F. above the crystalline melting point.
Completion of the adhesive bond involves bringing together the surfaces
with heat activated urethane between them and subjecting the assembly to pressure
to insure good overall engagement. It has been found that limited relative
movement of the surfaces to be joined may be secured after the initial assembly
and before pressure because of the viscoelastic condition of the adhesive;
but that after the assembly is subjected to pressure, an initial high strength
bond is secured. The ultimate bond on cooling of the urethane adhesive has
excellent toughness and flexibility in order that the adhesive may successfully
withstand the stresses encountered in the use of a shoe having the sole attached
by means of this urethane adhesive.
While the coating or bonding method of the invention has been described
in terms of applying the adhesive in fluid molten or solution form, the method
may also be practiced by providing the chain extended adhesive as a supported
_g_
~7~;~5~
or unsupported ~lm and bonding it in heat activated form to a compatible surface
as a coating or between compatible surfaces as an adhesive bonding the surfaces
together .
The following examples are given to ald in understanding the invention.
It is to be understood that the invention is not restricted to the particular materials,
proportions or procedural details set forth in the examples.
Example 1
An -NCO terminated prepolymer is prepared by reacting a hydroxyl
10 terminated butanediol adipate polyester having a molecular weight of 2600
and a crystalline melting point of about 49C . with diphenylmethane diisocyanate
in proportions providing an -NCO to -OH ratio of 1. 5 . The resulting prepolymer
has a melting point of about 54C. and is fluid with a viscosity of about ô,000
cps. at 100C.
The above and other melting points given in this and subsequent examples
are crystalline melt points determined as endotherm peaks by differential thermal
analysis .
The prepolymer is melted and brought to a temperature of 100C. and
applied as a coating 0 . 003!' thick to the previously roughened sole attaching
surface of a leather shoe upper and to the attaching surface of an outsole compounded -~
of a vulcanized butadiene styrene copolymer synthetic rubber.
The applied coatings are exposed to a high humidity atmosphere on a
steam table at 70C . for 15 minutes for reaction of the moisture with -NCO groups
of the prepolymer to effect chain extension. After this treatment, the material
of the coatings is tough, strongly adherent to the attaching surface and capable
of being softened to tacky condition adhesive to like adhesive surfaces at temperatures
about 65C. The coatings on the attaching surfaces are subjected to infrared
heat activation in a radiant heat activator for 30 seconds with the heat unit
set at 60% input. The sole is assembled against the attaching surfaces of the
--10--
-
~07~35'~:
bottom of the shoe upper and the spotting tack is excellent. The assembly
is pressed in a sole attaching press to complete the bond. A strong initial
bond is formed with no separation or "grinning" and the bond strength is considered
satisfactory for use of -the shoe.
Example 2
Test strips 1" by 7" of the materials listed in the following Table I are
coated with molten prepolymer of Example l at 80C . to 90C . to provide a ,
coating thickness of 0 . 003" . After 15 minutes from the time of application of
10 the coatings, the strips are placed in a high humidity atmosphere on a steam
table at 70C. or in a room at about 36C. and 68% relative humidity for times
as noted in the table to react the -NCO groups in the material of the coating
with water to effect chain extension. The strips are then activated by infrared
heat in a conventional radiant heat activator (RHA) for 30 seconds with the
heat unit of the activator set at 60% input. Activation raises the temperature
of the coatings on the strips to about 68C. to 75C. The activated strips are
then assembled in pairs as noted in the table, and pressed to complete bonds
after which the assembled strips are cooled to room temperature and the bonds
subject to testing. The results of the tests are reported in the table.
--11--
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u~ co ~ o ~ ~ ~ co c~ ~
~ C~ CO C~ N C~ N
~ ml~ = ~ o
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E- 1~, h = - = h
o~
V C~
¢ ' ~j E 'q ~ = E .~1
~Q V
1:1 o O O o ~
.~ ~ ~ 3 h
~o ~ = = ~ o¢~ =
U~ ~o o ~ ~
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zol ~ CD ~ C~ a~ o ~ ,~
h ~ ~i l pC~
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773S'~
EXAMPLE 3
An -NCO terminated prepolymer is prepared by reacting
a hydroxyl terminated butanediol adipate polyester having a
molecular weight of 3,000 and a melting point of about 50C with
mixed diisocyanate in the molar ratio of two parts of diphenyl-
methane diisocyanate and one part of tolylene diisocyanate in
proportions providing an -MCO to -OH ratio of 2Ø The resulting
prepolymer had a melting point of about 54C and is fluid with a
viscosity of about 11,000 cps at 100C.
Test s-trips 1" by 7" were cut from an outsole sheet
material purchased as surface-chlorinated Krato ~ , which is a
styrene butadiene block copolymer of which the surface has been
chlorinated, a polyvinyl chloride outsole sheet material, and
a styrene butadiene copolymer outsole stock. Similar strips
were also cut of shoe upper material including the backed
polyvinyl chloride material known as Pattina~ and leather.
The strips of outsole material were coated with the
molten prepolymer at 80C to 90C to provide a coating thickness
of 0.003", and after application and cooling of the coatings,
the strips were placed in a high RH 90% humidity atmosphere on
a steam table at 70C for about one-quarter hour.
The strips of upper material were coated respectively
with a solvent-type polyurethane (Estane)6~ adhesive on the backed
polyvinyl chloride upper material and with a solvent-type phenolic
resin-polychloroprene sole àttaching cement on the leather upper
material. In each case the deposited adhesive coating was
allowed to dry for elimination of the solvent.
The adhesive coated surfaces of the outsole material
and upper material test strips were put in a radiant heat
activator for 10 seconds with the radiant heat unit set at 55%
input. The surface temperature of the adhesive on the surfaces
of the strips was about 80~C
'~
735;~
Strips of the adhesive coatecl backed polyvinyl chloride upper material
were assembled with strips of the adhesive coated block copolymer outsole
material and with the styrene butadiene copolymer outsole stock, and strips
of the adhesive coated leather were assembled with the polyvinyl chloride
outsole material and the assemblies were pressed together to comple-te the bonds.
When tested after seven days, the peel bond strengths were 31 lbs. per linear
inch between the polyvinyl chloride material and the block copolymer, 27 lbs.
per linear inch between the leather and the polyvinyl chloride outsole material
10 and 39 lbs. per linear inch between the polyvinyl chloride material and styrene
butadiene copolymer outsole stock.
Example 4
An -NCO terminated prepolymer was prepared by reaction of diphenyl
methane diisocyanate and a polycaprolactone having a molecular weight of
about 2B60 and a melting point of about 5~C., the prepolymer having a free -
NCO content of 2.18%.
The prepolymer was melted and brought to a temperature of 100C. and
20 applied as a coating 0 . 003" thick to a previously roughened surface of outsole
material formed of styrene-isoprene-styrene block copolymer. The applied
coating was exposed to a 95% REl humidity atmosphere on a steam table at 70C.
for 30 minutes for reaction of the mixture with -NCO groups of the prepolymer
to effect chain extension.
A viscous adhesive was prepared by dissolving a thermoplastic linear
poly~ster urethane elastomer in a solvent mixture of approximately equal parts
of tetrahydrofurane and methyl ethyl ketone, the solids content of this solution
being about 20%. The urethane elastomer was a commercial product ("Estane"),
30 substantially free from cross links, obtained by reaction of one mol of an
-OH terminated polyesterJ an aliphatic glycol and a diphenyl diisocyanate in
-14-
:
~07735~
proportions leaving essentially no unreacted isocyanate or hydroxyl groups.
The resulting solution had a viscosity at room temperature of from about 2,000
to 3, 000 Cp9 . as determined by the Brookfield viscometer .
The above solution type adhesive was brushed on the previously roughened
surface of a fabric backed polyvinyl chloride shoe upper material.
Twenty-four hours after application of the adhesive to the backed polyvinyl
chloride material, the coating was subjected to infrared heat activation in a
radiant heat activator for 30 seconds with the heat unit set at 60% input. The
10 heat activated backed polyvinyl chloride material was assembled with its adhesive
coated surface against the similarly heat activated adhesive coating on the block
copolymer sole material. Spotting tack was good. The assembly was pressed
together to complete the bond. The initial bond as determined by a peel
pull test was from 15 to 20 lbs. per linear inch. When the bond was tested
after 7 days, the peel bond strength was 45 lbs. per linear inch, and failure
occurred in the block copolymer.
Example 5
The procedure oP Example 4 was repeated except that a styrene butadiene
copolymer rubber outsole material was used in place of the block copolymer
material. The assembly showed good initial tack, very good initial bond
strength and a peel bond strength after 7 days of 39 lbs. per linear inch.
In this case failure occurred in the backed polyvinyl chloride shoe upper
material .
~xample 6
The following -NCO terminated prepolymers are prepared by reacting
polyols with diphenylmethane diisocyanate in the -NCO to -OH ratio shown
in the following Table II. The polyol for prepolymer 2 is a polycaprolactone
-15-
1~7735'~
having a molecular weight of 2890 and a melting point of about 56C. and
the prepolymer is prepared by reaction of the polyol with diphenylmethane
diisocyanate in proportions providing an -NCO/-OH ratio of 1. 75 . The polyol
for prepolymer 3 is an -OH terminated butanediol sebacate polyester having
a molecular weight of about 2000 and a m~elting point of about BD~C., and
the prepolymer is prepared by reaction of the polyol with diphenylmethane
diisocyanate in proportions providing an -NCO/-OH ratio of 1.75.
Test strips 1" by 7" of the materials listed in the following Table II
10 are coated with molten prepolymer at 80C. to 90C. to provide a coating
thickness of 0.003". After 15 minutes from the time of application of the
coatings, the strips are placed in a high humidity atmosphere on a steam
table at 70C. for 15 minutes to react the -NCO groups in the material of
the coating with water to effect chain extension. The strips are then activated
by infrared heat in a conventional radiant heat activator (~HA) for 30 seconds
with the heat unit of the activator set at 60% input.
Activation raises the temperature of the coatings on the strips to about
68C. to 75C. The activated strips are then assembled in pairs as noted
in the table, and pressed to complete bonds after which the assembled strips
are cooled to room temperature and the bonds subject to testing. The results
of the tests are reported in the table.
-16-
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O
O ~ ~ U~
o tQ ~ æ v æ ~ x x
Q)
co Is~ O ~ c~
o~ 3 Q R
R mC~ N ~ C`J -
R ~41 ~c~ = _ _ =
o
~ E~
G2 ~
R .
,~ ¢ .~ C~ o~O ~ oP
V c~
o ~ ~9 cQR
c~ ~ vl ~ fi = ~ o fi =
¢ E~ ~ ~ V
~n V o
o
~ ~ ~ E h t~
V V ~ U2
o ~ m ~
= ~Q ~ ~ 2 ~ V V~ ~ CQ
'q ol v ~q
~ z ~ N C`~
s~ o
P~ Z
,
.
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D D
c ~ ; o~ v~ (~' o~ o ,~ o~
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C D ~? ,.,. O W ~ C ~, tD
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o
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D
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c~ ~ co w ~
op ~.
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o p ~ ~
o
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107735'~
Example 7
An -NCO terminated prepolymer is prepared by reacting a hydroxyl
terminated butanediol adipate polyester having a molecular weight of 2600
and a crystalline melting point of about 4~lC. with diphenylmethane
diisocyanate in proportions providing an -NCO to -OF~ ratio of 1. 5 . The
resulting prepolymer has a melting point ~ ut 54C. and is fluid with
a viscosity of about 8000 cps. at 100C~
The prepolymer was dissolv~ m a 60% by weight solids solution
10 in a solvent mixture of 4 parts ~ne chloride and 1 part of toluene.
The solution had a viscosity of about 1500 cps.
The solution is applied as coatings 0.005" thick to the previously
roughened surface of leather shoe upper material and to the surface of an
outsole material compounded of a vulcanized butadiene styrene copolymer
- synthetic rubber and the coatings were dried.
The coatings are exposed to a high humidity atmosphere on a steam
ta~le at 70C. for 15 minutes for reaction of the moisture with -NCO groups
of the prepolymer to effect chain extension. After this treatment, the material
of the coatings is tough, strongly adherent to the surfaces and capable of
being softened to tacky condition adhesive to like adhesive surfaces at temperatures
of about 65C. The coatings are subjected to infrared heat activation in a
radiant heat activator for 20 seconds with the heat unit set at 55% output.
The surfaces are assembled together and pressed to complete the bond.
When tested after 7 days, the peel bond strength is 40 lbs. per linear inch.
Example 8
A prepolymer solution was prepared as in Example 7 but containing
0,25% of dimethyl pipera~ine based on the weight of the prepolymer.
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7735~
The solution was coated onto leather and to vulcani~ed butadiene
styrene copolymer synthetic rubber and the coatings dried as in Example 7.
Chain extension was effected by exposing the coatings for 15 minutes
at 85C. to an atmosphere having only 18% to 20% relative humidity to bring
the coatings to tough, strongly adherent condition.
Thereafter the coatings wexe heat activated and the leather and
synthetic rubber assembled and pressed as in Example 7. Peel bond strength
after seven days was 40 lbs. per linear inch.
Example 9
An -NCO terminated prepolymer is prepared by reacting a polycaprolactone
having a molecular weight of 2860 and a crystalline melting point of about
54C. with diphenylmethane diusocyanate in proportions providing a free
-NCO content of 2.18%.
The prepolymer is dissolved to form a 60% by weight solids solution
in toluene. The solution has a viscosity of about 1600 cps.
The solution is applied as coatings 0.005" thick to the previously
20 roughened surface of backed polyvinyl chloride shoe upper material and
to the surface of an outsole material compounded of a sytrene butandiene
styrene block copolymer.
The applied coatings are exposed to a 90Q6 relative humidity atmosphere
on a steam table at 70C. for 30 minutes for reaction of the moisture with
-NCO groups of the prepolymer to effect chain extension. After this
treatment, the mater;al of the coatings is tough, strongly adherent to the
surfaces and capable of being softened to tacky condition adhesive to like
adhesive surfaces at temperatures of about 65C. The coatings are subjected
30 to infrared heat activation in a radiant heat activator for 20 seconds with
the heat unit set at 55% output. The surfaces are assembled together and
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.
.' , .' :
1~773~;~
pressed to complete the bond. When tested after 7 days, the peel bond
strength is 42 lbs. per linear inch.
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