U.S. patent application number 09/865868 was filed with the patent office on 2002-03-28 for laminates prepared with reactive hot melt adhesive.
This patent application is currently assigned to ASHLAND INC.. Invention is credited to Chang, Chung-Ying, Walsworth, Gary J..
Application Number | 20020037415 09/865868 |
Document ID | / |
Family ID | 22977924 |
Filed Date | 2002-03-28 |
United States Patent
Application |
20020037415 |
Kind Code |
A1 |
Chang, Chung-Ying ; et
al. |
March 28, 2002 |
Laminates prepared with reactive hot melt adhesive
Abstract
The present invention relates to laminates prepared using
reactive hot melt adhesives. The reactive hot melt adhesives are
the reaction product of a polyurethane prepolymer and a vinyl
chloride based thermoplastic copolymer.
Inventors: |
Chang, Chung-Ying; (Dublin,
OH) ; Walsworth, Gary J.; (Dublin, OH) |
Correspondence
Address: |
ASHLAND INC.
P.O. BOX 2219
COLUMBUS
OH
43216
US
|
Assignee: |
ASHLAND INC.
|
Family ID: |
22977924 |
Appl. No.: |
09/865868 |
Filed: |
May 25, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09865868 |
May 25, 2001 |
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09257827 |
Feb 25, 1999 |
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6274674 |
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Current U.S.
Class: |
428/423.1 |
Current CPC
Class: |
C08G 18/4045 20130101;
Y10T 428/24996 20150401; C09J 127/06 20130101; C09J 127/06
20130101; B32B 2375/00 20130101; C08L 2666/14 20130101; C09J 175/04
20130101; Y10T 428/249992 20150401; Y10T 428/3154 20150401; C08G
18/307 20130101; C08L 2666/04 20130101; C09J 175/04 20130101; C08L
2666/14 20130101; Y10T 428/249993 20150401; Y10T 428/31551
20150401; C08G 18/12 20130101; B32B 7/12 20130101; C08L 75/04
20130101; C08G 18/12 20130101; Y10T 428/31699 20150401; C08L
2666/04 20130101; C08G 2170/20 20130101; B32B 27/40 20130101 |
Class at
Publication: |
428/423.1 |
International
Class: |
B32B 027/40 |
Claims
We claim:
1. A laminate, comprising; A) at least two substrate layers, and B)
between said substrate layers an adhesive consisting essentially of
the reaction product of; i) an isocyanate terminated prepolymer
with an isocyanate index greater than about 2, comprising the
reaction product of an aliphatic polyester polyol or mixture of
aliphatic polyester polyols and a polyisocyanate or mixture of
polyisocyanates, and ii) a thermoplastic copolymer having a weight
average molecular weight greater than 30,000 which is compatible
with the isocyanate prepolymer, comprising the reaction product of
vinyl chloride and at least one monomer capable of copolymerizing
with vinyl chloride; where the thermoplastic copolymer contains at
least 50% by weight vinyl chloride, at least 10% by weight of the
monomer capable of copolymerizing with the vinyl chloride and is
free of isocyanate reactive groups.
2. The laminate as claimed in claim 1 wherein the adhesive further
consists essentially of; a thermoplastic copolymer stabilizer.
3. The laminate as claimed in claim 1, wherein the thermoplastic
copolymer is the reaction product of vinyl chloride and at least
one monomer selected from the group consisting of; vinyl acetate,
vinylidene chloride, esters of methacrylic acid, acrylonitrile.
4. The laminate as claimed in claim 1, wherein at least one
aliphatic polyester polyol is a crystallizing aliphatic polyester
diol having a melting point of at least 40.degree. C.
5. The laminate as claimed in claim 1, wherein the thermoplastic
copolymer is the reaction product of vinyl chloride and vinyl
acetate.
6. The laminate as claimed in claim 1, wherein up to about 30% by
weight of the polyester polyol is replaced with a polyether polyol
or mixture of polyether polyols.
7. The laminate as claimed in claim 1, wherein the polyisocyanate
is an aromatic polyisocyanate.
8. The laminate as claimed in claim 1 wherein the adhesive is
reacted in the presence of a catalyst.
9. The composition as claimed in claim 2, where the stabilizer is
an epoxidized soybean oil, epoxidized tall oil, epoxy resin,
epoxidized polybutadiene or mixtures thereof.
10. A laminate, comprising; A) at least two substrate layers, and
B) between said substrate layers an adhesive consisting essentially
of the reaction product of; i) from 60% to 95% by weight of an
isocyanate terminated prepolymer with an isocyanate index greater
than about 2.0, comprising the reaction product of; a) a
polyisocyanate or mixture of polyisocyanates having an average
functionality of from 2.0 to about 2.3, and b) an aliphatic
polyester polyol or mixture of aliphatic polyester polyols; ii)
from 5% to 40% by weight of a thermoplastic copolymer that is
compatible with the isocyanate prepolymer, having a weight average
molecular weight greater than 30,000, comprising the reaction
product of vinyl chloride and vinyl acetate where at least 50% by
weight of the thermoplastic is vinyl chloride and at least 10% by
weight of the thermoplastic copolymer is vinyl acetate; iii) up to
20% by weight of a stabilizer selected from the group consisting of
epoxidized soybean oil, epoxidized tall oil, epoxy resin,
epoxidized polybutadiene and mixtures thereof; iv) optionally a
catalyst, v) optionally a filler, vi) optionally an antioxidant,
vii) optionally an adhesion promoter, viii) optionally a tackifier,
and ix) optionally a wax.
11. The laminate as claimed in claim 1, wherein the substrate
layers are selected from the group consisting of; coated and
uncoated metals, treated and untreated plastics, fiber reinforced
plastics, vinyl, plywood, particle board, oriented strand-board and
foam.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a division of U.S. Ser. No. 09/257,827.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not applicable.
BACKGROUND OF THE INVENTION
[0003] The present invention relates to solvent free,
moisture-curable, reactive hot melt adhesive compositions that are
solid at room temperature, a method of making the adhesive
compositions, a laminate prepared from the adhesive compositions
and a method of preparing the laminates. More particularly the
invention relates to solvent free, moisture-curable, hot melt
adhesive compositions comprising a polyurethane prepolymer and a
vinyl chloride based thermoplastic copolymer.
[0004] Moisture curable reactive hot melt adhesives are known.
Typically, these reactive hot melt adhesives are 100% solids
materials which do not contain or require solvents. They are solids
at room temperature and liquids when heated to application
temperatures. The adhesives are used to prepare laminated
structures such as garage doors, architectural panels, truck doors,
patio enclosure panels, transit panels, cold storage panels,
agricultural panels and the like. The materials used for the panel
portion of the laminates include coated and uncoated metals,
treated and untreated plastics, fiber reinforced plastics (FRP),
vinyl, plywood, particleboard, oriented strandboard (OSB) and foam.
The adhesive is required to provide structural performance with
high moisture resistance and high bond strength. In general, the
adhesive is applied in a molten state as a single component with a
roller, spraying, etc. Both batch and continuous processes can be
used to prepare a laminate. In a batch process a stack of adhesive
coated panels is assembled. The stack is placed in a press and
pressure is applied. The pressure of the press on the stack is not
released until adhesive strength has developed which is sufficient
to bond all the layers of the laminate tightly together. In a
continuous process the adhesive coated panel laminate is
continuously passed through a nip roller or other device for
applying pressure. In the continuous process the adhesive needs to
provide immediate adhesive strength (green strength) after rolling
or pressing in order to insure that the various layers of the
laminate remain bonded until the adhesive is allowed to continue to
cure. Reactive hot melt adhesives having quick green strength are
particularly suitable for a continuous process.
[0005] A number of reactive hot melt polyurethane adhesive
compositions are known. U.S. Pat. No. 3,931,077 discloses a
composition comprising, a polyurethane prepolymer having a
viscosity greater than 300,000 cps at 25.degree. C.; a
thermoplastic resin of an ethylene-vinylacetate copolymer; and a
tackifier. U.S. Pat. No. 4,585,819 teaches the combination of a
polyurethane prepolymer, a thermoplastic polyurethane or polyester,
and a synthetic resin selected from the group consisting of ketone
resins, hydrogenated products of acetophenone condensation resins
and mixtures thereof. U.S. Pat. No. 4,775,719 discloses
compositions comprising; a prepolymer having a viscosity of less
than 300,000 cps at 25.degree. C., a thermoplastic
ethylene-vinylacetate copolymer or ethylene acrylate copolymer, a
tackifier and an antioxidant. These compositions are prepared by
blending a polyurethane prepolymer with a melted mixture of a
thermoplastic polymer and a tackifier at 150.degree. C. U.S. Pat.
No. 4,808,255 teaches that compatible blends may be prepared by
combining a polyurethane prepolymer made by reacting an isocyanate
compound with a polyester polyol, a thermoplastic ethylene-vinyl
monomer copolymer and tackifying agent at elevated temperatures
sufficient to melt the composition but not harm the components.
U.S. Pat. No. 5,021,507 discloses thermoplastic acrylic modified
reactive urethane hot melt adhesive compositions in which the
acrylic component is prepared by polymerizing acrylic monomers in
the presence of polyols. An isocyanate is then added to react with
the polyol in situ. U.S. Pat. No. 5,527,616 relates to specific
uses of hot melt adhesives. It discloses a laminate for flexible
packaging using a polyurethane reactive hot melt adhesive. The
polyurethane prepolymer contains a polyester polyol component
having 3 to 50 mole % of an aromatic component selected from the
group consisting of an aromatic diol and an aromatic dicarboxylic
acid. Use of the aromatic component is said to markedly improve
adhesion to different polyester films. The patent discloses that
from 0 to 10 parts by weight of a thermoplastic copolymer may be
blended into the composition. U.S. Pat. No. 5,550,191 discloses a
catalyzed polyurethane reactive hot melt comprising; a reactive
polyurethane adhesive and from 0.05 to 0.15 wt %
2,2'dimorpholinoethyl ether catalyst. This reference discloses a
method of improving the cure speed of the composition by including
a thermoplastic ABA block, A-(BA)n-B block or radial A-B-A block;
where A=polystyrene, B=a rubbery block and n=2-50. U.S. Pat. No.
5,827,926 moisture-curable hot melt compositions comprising a
polyurethane prepolymer and a crystalline polymer. The crystalline
polymer must contain at least one crystalline monomer. The claimed
crystalline monomers are (meth)acrylate esters of non-tertiary
alcohols where the alkyl portion is comprised of 16 or more carbons
containing no isocyanate reactive hydrogen.
[0006] Other references disclose adhesive compositions containing a
mixture of a polyurethane prepolymer and a chlorinated resin.
Typically, these compositions are dissolved in solvents. They are
not reactive hot melts. U.S. Pat. No. 4,217,254 and U.S. Pat. No.
4,340,682 disclose adhesive compositions in solvents consisting
essentially of a recinoleate polyurethane prepolymer and a
chlorinated rubber or a chlorinated polyvinyl chloride resin. U.S.
Pat. No. 4,740,424 discloses compositions containing a polyurethane
prepolymer and a halogenated resin compatible with the prepolymer.
Polyols used to prepare the prepolymer are selected from the group
consisting of polytetramethylene oxide polyols, polycarbonate
polyols, and polysulfide polythiols. The halogenated resins contain
from 50 to 70 weight percent halogen.
BRIEF SUMMARY OF THE INVENTION
[0007] The present invention relates to solvent free,
moisture-curable, reactive hot melt adhesive compositions that are
solids at room temperature, methods of preparing the compositions,
methods of preparing laminates using the compositions of the
invention and laminates prepared using the adhesive compositions.
The compositions are comprised of an isocyanate terminated
prepolymer and a thermoplastic copolymer which is compatible with
the isocyanate prepolymer. The isocyanate prepolymer is the
reaction product of an aliphatic polyester polyol or mixture of
aliphatic polyester polyols and a polyisocyanate or mixture of
polyisocyanates. The thermoplastic copolymer is prepared from vinyl
chloride monomers and at least one other monomer capable of
copolymerizing with the vinyl chloride. The vinyl chloride monomers
make up at least 50% by weight of the thermoplastic copolymer. The
thermoplastic copolymer is free of isocyanate reactive groups and
has a weight average molecular weight (M.sub.w) greater than about
30,000.
[0008] The vinyl chloride based thermoplastic used in the present
invention can decompose releasing hydrogen chloride, during
processing and weathering. In order to ensure the effectiveness of
the present hot melt compositions a stabilizer can be added. The
stabilizer acts as an acid scavenger. Epoxy containing compositions
are generally suitable as stabilizers in the compositions of the
present invention. Examples of such compositions include epoxidized
oils and resins. Many of these compositions also act as
plasticizers. In addition, the composition may also contain
components typically found in solvent free, moisture-curable, hot
melt adhesives such as; catalysts, fillers, antioxidants, adhesion
promoters, tackifiers, plasticizers, waxes and the like. The
solvent free, moisture-curable, hot melt adhesive compositions of
the present invention may be prepared by conventional means,
however the compositions of the present invention can also be
prepared by a one-step, in-situ process which can be run at
moderate temperatures. The use of moderate processing temperatures
aids in maintaining the integrity of the adhesive components. One
object of the invention is to provide solvent free,
moisture-curable, hot melt adhesive compositions which exhibit
shear thinning Theological behavior, improved green strength, water
resistance, and adhesion to various substrates such as metals,
wood, plastics, and foams. Another object of the invention is to
provide a simple one step method of preparing the adhesive
compositions of the invention. Other objects of the invention
include laminates prepared using the claimed adhesive compositions
and method of preparing the laminates using the claimed adhesive
compositions.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0009] Not applicable.
DETAILED DESCRIPTION OF THE INVENTION
[0010] The present invention relates to solvent free,
moisture-curable, reactive hot melt adhesive compositions, methods
of making the compositions and the use of the compositions in the
preparation of laminates. It has been found that solvent free,
homogeneous, moisture-curable, reactive hot melt compositions can
be prepared from mixtures of an isocyanate terminated prepolymer
and a vinyl chloride copolymer. The compositions are easily made by
a one step in-situ process and exhibit excellent physical
characteristics, such as shear thinning rheological behavior,
improved green strength, water resistance, and adhesion to a
variety of substrates. Other additives commonly added to the
moisture-curable reactive hot melt adhesive compositions include
catalysts, fillers, antioxidants, adhesion promoters, tackifiers,
plasticizers, stabilizers and waxes. These additives may be added
to the extent they do not adversely effect the basic
characteristics of the compositions of the present invention. The
preparation of isocyanate terminated prepolymers is well known in
the art. Typically, the isocyanate terminated prepolymer is
prepared by the reaction of a polyisocyanate with a polyol. The
isocyanate terminated prepolymer of the present invention is
prepared by reacting an excess of a polyisocyanate with an
aliphatic polyester polyol. The polyisocyanate excess should be
such that the isocyanate index of the prepolymer is greater than
about 2.0. Preferably the isocyanate index is about 3.0. The
isocyanate index is the ratio of isocyanate groups to isocyanate
reactive groups.
[0011] For purposes of the present invention the term
polyisocyanate includes isocyanate compositions with two or more
isocyanate groups per molecule. Examples of polyisocyanates useful
in the present invention include diphenylmethane-2,4'-diisocyanate,
diphenylmethane-4,4'-diisocyan- ate, tolylene-2,6-diisocyanate,
naphthalene-1,5-diisocyanate,
triphenylmethane-4,4',4"-trisocyanate, 1,4-phenylene diisocyanate,
4,4'-cyclohexylmethane diisocyanate, hexamethylene diisocyanate,
isophorone diisocyanate, tetramethylxylene diisocyanate, xylene
diisocyanate and the like. A single polyisocyanate or mixture of
polyisocyanates may be used. The average functionality of the
polyisocyanate or mixture of polyisocyanates used in the
preparation of the prepolymer should be between 2.0 and 2.3.
Preferably, the average functionality is between 2.0 and 2.1.
[0012] Examples of aliphatic polyester polyols include
polyesterpolyols obtained by ring opening polymerization of a
lactone such as e-caprolactone and polyester polyols derived from
polyhydric alcohols and polybasic acids. A mixture of aliphatic
polyester polyols containing at least one crystallizing aliphatic
polyester diol having a melting point of at least 40.degree. C. is
preferred. Examples of polyhydric alcohols which may be used in the
reaction with polybasic acids includes, ethylene glycol,
1,2-propylene glycol, 1,3-propylene glycol, 1,3-butylene glycol,
1,4-butylene glycol, neopentyl glycol, 1,6-hexanediol,
1,8-octanediol, 1,10-decanediol, 1,12-dodecanediol, diethylene
glycol, dipropylene glycol, cyclohexane-1,4-diol, glycerol,
trimethylol propane, etc. Examples of polybasic acids includes,
succinic acid, glutaric acid, adipic acid, pimelic acid, suberic
acid, azelaic acid, sebacic acid, undecanedionic acid, dodecandioic
acid, etc.
[0013] Up to about 30% by weight of a polyether polyol or mixture
of polyether polyols based on the total weight of all polyols may
be used in the preparation of the prepolymer. However, if amounts
greater than about 30% by weight are used the thermoplastic vinyl
chloride copolymer will not be miscible in the polyol.
Consequently, the mixture of the prepolymer and the thermoplastic
vinyl chloride copolymer would not be homogeneous. The isocyanate
prepolymer is present in the reactive hot melt adhesive composition
in an amount of from 60% to 95% by weight based on the total weight
of the adhesive composition.
[0014] The polyether polyols useful in the present invention are
well known to those skilled in the art. These polyols are obtained
by copolymerizing at least one compound of ethylene oxide,
propylene oxide, butylene oxide, tetrahydrofuran, etc. with at
least one compound having at least two active hydrogen atoms on
average in one molecule such as the polyhydric alcohols list above
which include ethylene glycol, propylene glycol, dipropylene
glycol, glycerol and the like. Other suitable polyhydric compounds
include sucrose, ethylenediamine, propylenediamine,
triethanolamine, 1,2-propanedithiol, etc. The thermoplastic
copolymer of the present invention is prepared from vinyl chloride
monomers and at least one other monomer capable of copolymerizing
with vinyl chloride. Preferably, the copolymer contains at least
about 10% by weight of a monomer capable of copolymerizing with the
vinyl chloride. Vinyl chloride makes up at least 50% by weight of
the thermoplastic copolymer. The copolymer is free of isocyanate
reactive groups and has a weight average molecular weight (M.sub.w)
of greater than 30,000. Typically, the M.sub.w is from greater than
about 30,000 to about 100,000. A most preferred M.sub.w is about
60,000. Examples of monomers copolymerizable with a vinyl chloride
monomer include ethylene, propylene, butenes, pentene-1,
butadienes, styrene, acrylonitrile, vinylidene chloride, vinylidene
cyanide, alkyl vinyl ethers, vinyl carboxylate esters, allyl
ethers, N-vinylpyrrolidone, vinyl silanes, esters of acrylic and
methacrylic acid, or mixtures thereof. Especially preferred
monomers include vinyl acetate, alkyl esters of methacrylic acid,
vinylidene chloride, acrylonitrile, or mixtures thereof. Preferred
esters of acrylic and methacrylic acid are those alkyl esters where
the alkyl group has from 1 to 12 carbon atoms. An example of a
preferred thermoplastic copolymer is a vinyl chloride-vinyl acetate
copolymer having a weight average molecular weight of between
60,000 and 65,000. The thermoplastic copolymer preferably is
present in the reactive hot melt adhesive composition in an amount
of from 5% to 40% by weight based on the total weight of the
adhesive composition. Vinyl chloride copolymers in general are
somewhat susceptible to degradation during processing and
weathering. For instance, when a polyvinyl chloride copolymer is
exposed to heat and light a non-chain scission reaction such as
dehydrochlorination can occur. In order to alleviate the effects of
this type of reaction a stabilizer is added to the reactive hot
melt composition. The stabilizer acts as an acid scavenger and to
some extent a plasticizer, in the reactive hot melt. Suitable
stabilizers include epoxide group containing compositions. Examples
of useful epoxide group containing compositions include epoxy
resins, epoxidized soybean oil, epoxidized tall oil and epoxidized
polybutadiene. These epoxide group containing compositions are
present in the reactive hot melt adhesive compositions in amounts
up to about 20% by weight based on the total weight of the adhesive
composition. Preferably, the epoxide containing compositions are
present in amounts of from 5% to 15% by weight based on the total
weight of the composition. Other stabilizers although not preferred
may be used. Examples of other stabilizers include metallic soaps
such as lead, calcium, barium, zinc, or cadmium stearate.
[0015] Other commonly used additives may be added to the reactive
hot melt adhesive compositions. Such common additives include
catalysts, fillers, antioxidants, adhesion promoters, tackifiers
and waxes.
[0016] Catalysts that may be employed are those conventionally used
to promote the reaction of the isocyanate group with an active
hydrogen. Examples include amine catalysts such as triethyl amine,
triethylene diamine, N-methyl morpholine, 2,2'-dimorpholinoethyl
ether, and di(2,6-dimethylmorpholinomethyl)ether; and tin catalysts
such as tetramethyltin, tetraoctyltin, dimethyl dioctyltin,
triethyltin dichloride, dibutyltin diacetate and dibutyltin
dilaurate.
[0017] Fillers include for example carbon black, calcium carbonate,
titanium dioxide, talc and precipitated and fumed silica.
[0018] Antioxidants include phenolic types such as, BHT (butylated
hydroxytoluene),
octadecyl-3,5-bis(1,1-dimethyl)-4-hydroxybenzene-propano- ate, and
pyrogallol; phosphites such as, triphenyl phosphite,
tris(nonylphenyl) phosphite; or thioesters such as, dilauryl
thiodipropionate.
[0019] Adhesion promoters include, organosilanes such as,
isocyanatopropyltriethoxysilane,
gamma-mercaptopropyltrimethoxysilane,
gamma-glycidoxypropyltrimethoxysilane, and
tris(3-trimethoxysilyl)isocyan- urate. Tackifiers can include rosin
esters and terpene phenolic resins.
[0020] Waxes which can be included in the compositions of the
present invention are generally defined as hydrocarbons or
hydrocarbon derivatives which are solids at room temperature
(77.degree. F.), but are low viscosity liquids at moderately higher
temperatures (below 250.degree. F.). An example of a typical wax is
paraffin. The reactive hot melt adhesive compositions of the
present composition may be prepared in any manner known in the art
for preparing similar compositions. However, the compositions of
the present invention are preferably prepared in a simple process
where the polyester polyol, the thermoplastic vinyl chloride
copolymer, the polyisocyanate and other additives are added to a
single reaction vessel; the polyisocyanate and polyester prepolymer
are allowed to react forming the prepolymer in-situ; and the
resulting homogeneous mixture is discharged to a clean dry
container. Those skilled in the art will understand that exact
conditions for the preparation of the reactive hot melt adhesive
compositions of the present invention will vary with the individual
components. The following procedure provides a preferred method.
Typically, a polyester polyol or mixture of polyester polyols is
premelted at 100.degree. C. to 130.degree. C. The melted polyester
polyol(s) and optional stabilizer are charged into a reaction
vessel equipped with an anhydrous inert gas inlet, a means for
agitating the contents of the vessel, an addition port, a vacuum
source, a heat source and a discharge port. Solid, powdered vinyl
chloride based copolymer is added to the melted polyester polyol
mixture with sufficient agitation to wet the powder. The wetted
powder is allowed to dissolve in the polyol and the molten mixture
is dehydrated at 115.degree. C. to 130.degree. C. for from about 45
minutes to 60 minutes under a vacuum of about 25 mmHg. When the
dehydration is complete, the mixture is allowed to cool under
vacuum to 115.degree. C. The vacuum is relieved with anhydrous,
inert gas and polyisocyanate is added to the mixture under the
inert gas with agitation. The temperature is raised to 120.degree.
C. to 130.degree. C. under a vacuum about 25 mmHg and the
polyisocyanate and polyester polyol are allowed to react. On
completion of the reaction of the polyisocyanate and the polyol,
the homogeneous melt can be discharged to a container under an
anhydrous inert gas atmosphere. The storage containers should be
air tight. Additives can be added at any appropriate time during
the process. Preferably, the stabilizer is added prior to heating
the thermoplastic vinyl chloride copolymer. The optional catalyst
can be added to the molten homogeneous mixture before or after the
reaction between the polyisocyanate and the polyester polyol is
complete but before the mixture is completely cooled and
discharged.
[0021] The reactive hot melt adhesive compositions have melt
viscosities of up to 50,000 cps at 250.degree. F. The reactive hot
melt adhesive compositions of the invention exhibit shear thinning
rheology which allows viscous molten adhesive compositions to be
delivered and applied at reduced viscosities without raising
process temperatures beyond common current temperatures of about
250.degree. F.
[0022] Having thus described the invention the following examples
are illustrative in nature and should not be construed as
limiting.
[0023] In the examples all parts are by weight unless otherwise
indicated. Melt viscosity is in centipoise and determined using a
Brookfield Thermosel viscometer with a #27 spindle at 5 rpm.
Following are descriptions of compositions used in the
examples.
[0024] Tone 0240 is a poly (.epsilon.-caprolactone) polyol
available from Union Carbide.
[0025] Dynacoll 7380 is a crystalline polyester available from
Creanova.
[0026] Lexorez 1931-50 is a polyglycol adipate available from
Inolex.
[0027] EPON 825 is a bisphenol A/epichlorohydrin based epoxy resin
available from Shell.
[0028] CP 4915 is a vinyl chloride vinyl acetate copolymer
available from Colorite Polymers.
[0029] ISONATE 2125M is a 4-4'-diphenylmentane diisocyanate (MDI)
available from Dow.
[0030] FLEXOL PLASTICIZER EPO is a epoxidized soybean oil available
from Union Carbide.
[0031] MONDUR ML is an isomer mixture of diphenylmentane
diisocyanate (MDI) available from Bayer.
[0032] ELVACITE 2013 is an acrylic resin available from ICI.
EXAMPLE 1
[0033] 37.11 g of Tone 0240, 6.00 g of Dynacoll 7380 available from
Creanova, 5.00 g of Lexorez 1931-50 and 15.00 g of Epon 825 were
premelted at 100.degree. C. to 130.degree. C. in an oven. The
melted mixture was charged to a glass kettle fitted with an
anhydrous nitrogen gas inlet adapter, a cover with rubber gasket,
gas inlet, and stirrer. 20.00 g of CP 4915 powder was added to the
melt with stirring and allowed to mix until the CP 4915 was
thoroughly wetted. The contents of the vessel were stripped at
115.degree. C. to 130.degree. C. for about 45 minutes under a
vacuum of about 25 mmHg. After 45 minutes the temperature was
allowed to cool to about 115.degree. C. while maintaining the
vacuum. When the temperature of the molten mixture reached at
115.degree. C., the vacuum was relieved with anhydrous nitrogen and
16.89 g of ISONATE 2125M were added with mixing. The temperature of
the mixture was raised to 120.degree. C. to 130.degree. C. under a
vacuum of about 25 mmHg and the mixture was allowed to react for
about 45 to 60 minutes. The finished product was discharged to a
clean, dry container under an anhydrous nitrogen blanket and
sealed. The finished product was homogeneous and had an NCO Index
of 3.0; an NCO content, %(calc.) 3.78; and a viscosity at
250.degree. F. of 13,550.
EXAMPLE 2
[0034] The same procedure for preparing a reactive hot melt
adhesive composition as that used in example 1 was followed except
that the following components were used:
1 Tone 0240 51.65 g Dynacoll 7380 6.00 g Lexorez 1931-50 5.00 g
Epon 825 15.00 g ISONATE 2125M 22.35 g
[0035] The composition had an NCO Index of 3.0; an NCO content,
%(calc.) of 5.00; and a viscosity at 250.degree. F. of 2,670.
EXAMPLE 3
[0036] The same procedure for preparing a reactive hot melt
adhesive composition as that used in Example 1 was followed except
that the following components were used:
2 Tone 0240 37.11 g Dynacoll 7380 6.00 g Lexorez 1931-50 5.00 g
Epon 825 15.00 g Elvacite 2013 20.00 g ISONATE 2125M 16.89 g
[0037] The composition appeared grainy indicating that it was not
homogeneous. It had an NCO Index of 3.0; an NCO content, %(calc.)
3.78; and a viscosity at 250.degree. C. of 1,490.
EXAMPLE 4
[0038] The composition was prepared according to the procedure used
in Example 1 of U.S. Pat. No. 5,550,191. 16.89 g of Lexorez
1400-56, 39.37 g Poly-G 20-56 and 25.00 g of Elvacite 2013 were
added to vessel and heated to 100.degree. C. until the Elvacite
dissolved. At that point 18.74 g of ISONATE 2125M was added and the
reaction was held at 100.degree. C. for 3 hours. The reaction
mixture was decanted hot to a clean, dry container. The composition
had an NCO Index of 1.57; an NCO content, %(calc.) 2.27; and a
viscosity at 250.degree. F. of 13,350.
EXAMPLE 5
Rheology
[0039] The shear thinning behavior of adhesive examples 1, 2, 3 and
4 was examined. Each of the adhesive samples was subject to a shear
sweep from 0 to 1,000 l/sec. at 250.degree. F., using a Carrier Med
CSL Rheometer (TA Instruments, Inc.). The viscosity curves for the
4 examples are given in the graph below.
[0040] Example 1, which was a vinyl chloride copolymer-polyurethane
adhesive according to the invention shows a much greater shear
thinning behavior than examples 2-4, which exhibit little if any
shear thinning rheology.
EXAMPLE 6
Green Strength
[0041] The green strength of examples 1-4 was compared by measuring
the hold time of a laminate prepared from a vinyl sheet and
expanded polystyrene. A thin film of molten adhesive (1.1 g.+-.0.3)
at about 250.degree. F. was coated onto a 2.0 inch by 3.0 inch
piece of expanded polystyrene foam. Light pressure (.about.0.5 psi)
was applied to the laminate for 5 minutes. After 5 minutes firm
hand pressure was used to mate the surfaces. Immediately, a 1,000 g
weight was hung from the vinyl sheet and the timer started. Holding
time was recorded as the point when the vinyl sheet completely
separated from the foam. The results are given in the chart
below.
3 Example No. Holding time (minutes) 1 16.10 2 6.29 3 0.78 4
9.33
EXAMPLE 7
Peel Strength
[0042] Three samples were prepared according to the procedure of
Example 1. The compositions used to prepare each of the three
samples are listed in Table 1. The adhesive samples were then
applied to substrates. In each case metal was bonded to the grade A
side of plywood. Each laminate specimen was allowed to cure at room
temperature and ambient humidity for seven days. Both water soak
and hot peel tests were performed on each type of sample. For the
water soak test samples were completely immersed in water at
ambient temperatures. Each sample was the subject first to a vacuum
of 25 mmHg or less for thirty minutes and then to pressure
(.about.75 psi) for an additional thirty minutes. The pressure was
relieved and each sample was tested wet.
[0043] For the hot peel test each sample was held in a hot air
circulating oven at 160.degree. F. for 16 to 24 hours. Samples were
tested immediately after being removed from the oven. Results of
the water soak peel test and the hot peel test are given in Tables
2 and 3.
4TABLE 1 ADHESIVE # CONTROL 1 2 COMPOSITION WEIGHT (%) WEIGHT (%)
WEIGHT (%) TONE 0240 78.41 56.06 56.06 FLEXOL EPO -- 10.00 -- EPON
825 -- -- 10.00 CP 4915 -- 15.00 15.00 MONDUR ML 21.59 18.93 18.93
NCO INDEX 2.20 2.70 2.70 NCO Cont, % 3.95 4.00 4.00 (calc) Melt
Visc. 1,000 4,450 7,350 (cps) @ 250.degree. F.
[0044]
5TABLE 2 90.degree. Wet Peel in Water Soak Test - ASTM D3167 Metal
to Plywood (Douglas fir, A/C) CONTROL 1 2 ADHESIVE Wood Wood Wood #
Strength Failure Strength Failure Strength Failure Metals (pli) (%)
(pli) (%) (pli) (%) Epoxy 16 72 NA Wood 11 88 Backed Broke Aluminum
Bare 16 60 9.9 52 12 80 Aluminum Mirror 11 75 9.4 88 12 58
Stainless Steel Notes: Numbers shown are the average of 2 specimens
(1 inch .times. 12 inches), crosshead speed 2.0"/min.
[0045]
6TABLE 3 90.degree. Hot Peel at 160.degree. F. Test - ASTM D 3167
Metal to Plywood (Douglas fir, A/C) CONTROL 1 2 ADHESIVE Wood Wood
Wood # Strength Failure Strength Failure Strength Failure Metals
(pli) (%) (pli) (%) (pli) (%) Epoxy 24 58 NA Wood 13 90 Backed
Broke Aluminum Bare 13 0 10 100 11 96 Aluminum Mirror 19 80 16 96
12 85 Stainless Steel Notes: Numbers shown are the average of 2
specimens (1 inch .times. 12 inches), crosshead speed 2.0"/min.
* * * * *