U.S. patent application number 12/008041 was filed with the patent office on 2010-11-11 for surfaces containing coupling activator compounds and reinforced composites produced therefrom.
Invention is credited to Jawed Asrar, Thomas Burghardt, Klaus Friedrich Gleich.
Application Number | 20100286343 12/008041 |
Document ID | / |
Family ID | 43062730 |
Filed Date | 2010-11-11 |
United States Patent
Application |
20100286343 |
Kind Code |
A1 |
Burghardt; Thomas ; et
al. |
November 11, 2010 |
Surfaces containing coupling activator compounds and reinforced
composites produced therefrom
Abstract
The invention relates to products and processes employing
coupling activator compounds represented by the following formula
I: S--X-A (I) wherein S represents a silane coupling moiety capable
of bonding with the surface of an inorganic substrate, A represents
a ring-opening polymerization activator moiety, or blocked
precursor thereof, and X represents a linking moiety. Substrates
containing the coupling activator compounds are useful in preparing
reinforced resins.
Inventors: |
Burghardt; Thomas; (Parker,
CO) ; Asrar; Jawed; (Greenwood Village, CO) ;
Gleich; Klaus Friedrich; (Highlands Ranch, CO) |
Correspondence
Address: |
JOHNS MANVILLE
10100 WEST UTE AVENUE, PO BOX 625005
LITTLETON
CO
80162-5005
US
|
Family ID: |
43062730 |
Appl. No.: |
12/008041 |
Filed: |
January 8, 2008 |
Current U.S.
Class: |
525/410 ;
264/134; 264/271.1; 427/340; 428/408; 428/411.1; 428/429; 428/447;
442/59; 526/348; 528/323; 528/326; 528/354; 528/359; 528/44 |
Current CPC
Class: |
B29K 2105/06 20130101;
C08L 75/04 20130101; C08L 77/02 20130101; Y10T 428/31612 20150401;
C08G 18/718 20130101; C08J 5/24 20130101; C08J 2377/02 20130101;
B29K 2301/10 20130101; Y10T 428/31663 20150401; Y10T 442/20
20150401; C08G 18/8074 20130101; C08J 2365/00 20130101; B29C 48/04
20190201; B29C 48/022 20190201; Y10T 428/31504 20150401; C08J 5/08
20130101; C08J 2367/04 20130101; C08J 2375/04 20130101; Y10T 428/30
20150115 |
Class at
Publication: |
525/410 ;
428/447; 428/429; 428/408; 442/59; 264/134; 264/271.1; 428/411.1;
528/354; 528/323; 528/326; 528/359; 526/348; 528/44; 427/340 |
International
Class: |
C08L 77/04 20060101
C08L077/04; B32B 9/04 20060101 B32B009/04; B32B 17/02 20060101
B32B017/02; B32B 5/02 20060101 B32B005/02; B29C 47/02 20060101
B29C047/02; B29C 39/10 20060101 B29C039/10; C08G 63/08 20060101
C08G063/08; C08G 69/14 20060101 C08G069/14; C08F 210/00 20060101
C08F210/00; C08G 18/00 20060101 C08G018/00; B05D 3/10 20060101
B05D003/10 |
Claims
1. An inorganic substrate having bonded thereto a coupling
activator compound of the formula: S--X-A wherein S represents a
silane coupling moiety through which the compound is bonded to the
surface of the inorganic substrate, A represents a ring-opening
polymerization activator moiety, or blocked precursor thereof,
which is capable of participating in an in situ ring-opening
polymerization of a monomer in the presence of a polymerization
catalyst when exposed to ring-opening polymerization conditions,
and X represents a linking moiety capable of linking the S moiety
and the A moiety.
2. An inorganic substrate according to claim 1 wherein the surface
of the inorganic substrate contains a coating of a sizing
composition comprising the coupling activator compound.
3. An inorganic substrate according to claim 1 wherein the
inorganic material is glass, basalt, carbon fibres, carbon
nanotubes, inorganic nanotubes, or metal fibres.
4. An inorganic substrate according to claim 3 wherein the glass is
in the form of one or more continuous strands, chopped strands,
mats or rovings.
5. An inorganic substrate according to claim 1 wherein S represents
an organosilane group of the formula: ##STR00007## wherein X is as
defined in claim 1, and R.sup.1, R.sup.2 and R.sup.3 may be the
same or different and each may represent alkyl, aryl, alkoxy,
halogen, hydroxy, or a cyclic structure wherein X is connected with
one or more of R.sup.1, R.sup.2 and R.sup.3.
6. An inorganic substrate according to claim 1 wherein the coupling
activator compound is
2-oxo-N-(3-(triethoxysilyl)propyl)azepane-1-carboxamide.
7. An inorganic substrate according to claim 1 wherein A represents
an N-substituted imide group.
8. An inorganic substrate according to claim 1 wherein X represents
alkyl, aryl, or alkyl-aryl.
9. An inorganic substrate according to claim 1 wherein A is a
blocked isocyanate group.
10. A process for preparing a reinforced resin material comprising
the steps of: providing an inorganic substrate; applying to the
inorganic substrate a sizing composition comprising a coupling
activator compound of the formula: S--X-A wherein S represents a
silane coupling moiety capable of bonding with the surface of the
inorganic substrate, and A represents a ring-opening polymerization
activator moiety, or blocked precursor thereof; which is capable of
participating in an in situ ring-opening polymerization of a
monomer in the presence of a polymerization catalyst when exposed
to ring-opening polymerization conditions, and X represents a
linking moiety capable of linking the S moiety and the A moiety;
mixing the sized inorganic substrate with a monomer and a
ring-opening polymerization catalyst to form a polymerization
mixture; and exposing the polymerization mixture to conditions
sufficient to cause an in situ ring-opening polymerization of the
monomer to form a reinforced resin in which the inorganic substrate
is grafted onto a polymer.
11. A process according to claim 10 wherein the monomer is a lactam
or lactone having 3-12 carbon atoms in the main ring, and the
polymerization is anionic ring-opening polymerization.
12. A process according to claim 10 wherein the monomer is a cyclic
olefin and the polymerization is ring-opening metathesis
polymerization.
13. A process according to claim 10 wherein A is a blocked
isocyanate group that becomes unblocked to form an active
isocyanate group that reacts with the monomer to form the
polymerization activator moiety when exposed to the polymerization
conditions.
14. A process according to claim 10 wherein the sizing composition
is coated on the surface of glass fibres and the sized glass fibres
are collected in the form of rovings.
15. A process according to claim 10 comprising a reactive extrusion
process wherein sized fibres and a composition comprising monomer
and catalyst are separately fed into an extruder to form the
polymerization mixture, the polymerization mixture is exposed to
polymerization conditions in the extruder to cause the
polymerization, and the resultant fiber reinforced resin is
extruded through a die into the desired shape.
16. A process according to claim 10 comprising a resin transfer
molding process wherein sized fibres and a composition comprising
monomer and catalyst are mixed together in a closed mold to form
the polymerization mixture, the polymerization mixture is exposed
to the polymerization conditions in the mold to cause the
polymerization, the mold is opened, and the resultant shaped fiber
reinforced resin is removed from the mold.
17. A process according to claim 10 comprising a pultrusion process
wherein sized fibres are pulled through a composition comprising
monomer and catalyst to impregnate the fibres with the composition
and form the polymerization mixture, the impregnated fibres are
pulled through a heated die to cause the polymerization, and the
resultant shaped fiber reinforced resin is recovered from the
die.
18. A process according to claim 10 comprising a reinforced
reaction injection molding process wherein sized fibres are
dispersed in a liquid composition comprising monomer and catalyst,
the liquid composition is injected into a mold, heated to cause the
polymerization, and the resultant shaped fiber reinforced resin is
removed from the mold.
19. A fiber reinforced resin material formed by the process of
claim 10.
20. An inorganic substrate having bonded thereto
2-oxo-N-(3-(triethoxysilyl)propyl)azepane-1-carboxamide or a
blocked isocyanate precursor thereof.
21. A polymerization mixture for preparing a fibreglass-reinforced
polyamide comprising: inorganic substrate having coated on the
surface thereof a sizing composition comprising a coupling
activator compound of the formula: S--X-A wherein S represents a
silane coupling moiety capable of bonding to the inorganic
substrate surface; A represents an anionic ring-opening
polymerization activator moiety or a blocked precursor thereof; and
X represents an alkyl, aryl or alkyl-aryl linking moiety; a lactam
or lactone monomer; and a catalyst.
22. A process for preparing fibreglass-reinforced Nylon-6
comprising the steps of: preparing a sizing composition comprising
2-oxo-N-(3-(triethoxysilyl)propyl)azepane-1-carboxamide; coating
the sizing composition on the surface of rovings of glass fibres;
drying the sized rovings; mixing the sized rovings with a
caprolactam monomer and sodium caprolactam catalyst to form a
polymerization mixture; and heating the polymerization composition
to a temperature sufficient to cause an in situ anionic
ring-opening polymerization of the caprolactam monomer to form a
matrix in which the glass fibres are grafted to Nylon-6
polymer.
23. A glass-reinforced Nylon-6 formed by the process of claim 22.
Description
BACKGROUND OF THE INVENTION
[0001] It is well-known to employ inorganic materials in composite
articles to strengthen and reinforce the articles. In addition to
increased dimensional stability, addition of the inorganic material
provides polymer composites with significantly improved physical
and mechanical properties. As one example, glass fibres may be
placed into a polymer matrix where the high tensile strength of
glass causes the composite to become more rigid. The glass fibres
incorporated in the polymer matrix may take various forms:
continuous or chopped strands, rovings, woven or non-woven fabrics,
continuous or chopped strand mats, etc.
[0002] Conventionally, glass fibres are formed by attenuating
streams of a molten glass material from a bushing or orifice. The
glass fibres may be attenuated by pulling by a winder, which
collects filaments into a package or by other equipment or method
capable of pulling the fibres. A sizing composition, or chemical
treatment, is typically applied to the fibres after they are drawn
from the bushing. After the fibres are treated with the sizing,
which is typically in aqueous form, they may be dried in a package,
chopped, or kept in the wet state before downstream processing.
[0003] Fibreglass may be mixed with a polymeric resin in an
extruder and supplied to a compression- or injection-moulding
machine to be formed into glass fibre-reinforced plastic
composites. Typically, polymer pellets and fibreglass are fed
together or separately into an extruder. During the extrusion
process using single or twin-screw machines, the resin is melted
and the fibres are dispersed throughout the molten resin to form a
fibre/resin mixture. Next, the fibre/resin mixture may be degassed,
cooled, and formed into pellets. The dry fibre strand/resin
dispersion pellets are then fed to a moulding machine and formed
into moulded composite articles that have a substantially
homogeneous dispersion of glass fibre strands throughout the
composite article.
[0004] Alternatively, in the process using continuous filaments,
fibreglass filaments are mixed with the molten resin in an extruder
with the screw geometry designed to mix the matrix with fibres
without causing significant damage to the fibres. Obtained extruded
materials are then subjected to compression moulding to form
long-fibre reinforced thermoplastic materials with significantly
improved mechanical properties due principally to the fibres having
a higher aspect ratio.
[0005] Various chemical treatments exist for inorganic surfaces
such as glass fibres to aid in their processability and
applications. After fibre formation and before bundling, the
filaments or fibres may be treated with a coating composition
(hereinafter referred to as a "sizing composition") that is applied
to at least a portion of the surface of the individual filaments to
protect them from abrasion, improve the chemical or physical
bonding, and to assist in processing. As used herein, the term
"sizing composition", refers to any such coating composition
applied to the filaments after forming. Sizing compositions may
provide protection for subsequent processing steps, such as those
where the fibres pass by contact points as in the winding of the
fibres and strands onto a forming package, drying the sized fibres
to remove the water and/or other solvent or melting of the film
former on the fibre surface, twisting from one package to a bobbin,
beaming to place the yarn onto very large packages ordinarily used
as the warp in a fabric, chopping in a wet or dry condition, roving
into larger bundles or groups of strands, unwinding, and other
downstream processes. In addition, sizing compositions can play a
dual role when placed on fibres that reinforce polymeric matrices
in the production of fibre-reinforced plastics. In such
applications, the sizing composition can provide protection as well
as compatibility and/or chemical bonding between the fibre and the
matrix polymer. Conventional sizing compositions typically contain
one or more film forming polymeric or resinous components,
glass-resin coupling agents, and one or more lubricants dissolved
or dispersed in a liquid medium. The film forming component of the
sizing composition is desirably selected to be compatible with the
matrix resin or resins in which the glass fibres are to be
embedded.
[0006] Many types of polymers may be reinforced by inorganic
materials. Of particular note are those polymers formed by
ring-opening polymerization reactions. Polyamides (PA), such as
poly(caprolactam), commonly know as "Nylon-6" or "polyamide-6", are
examples of resins formed by ring-opening polymerization that are
frequently reinforced by glass fibres. There is a need to provide
glass-reinforced polyamide composites with high glass loading;
however, one of the barriers is the high polymer viscosity of the
polyamide in the molten state. This high viscosity hinders the
dispersion of the glass fibres throughout the molten resin when the
fibre/resin mixture is formed.
[0007] Anionic-catalysed ring-opening polymerization of lactams has
become a commercially significant method for preparation of PA
resins since these polymerizations can be conducted at relatively
low temperatures and under atmospheric pressures. Caprolactam is by
far the most studied lactam for such reactions and Nylon-6 prepared
by this route compares favorably in properties with that prepared
by conventional hydrolytic polymerization. Fast reaction kinetics,
absence of by-products, and the crystalline nature of the Nylon so
produced also makes anionic polymerization of lactams a compelling
choice for several industrial applications, including reactive
extrusion, reactive thermoplastic pultrusion, reaction transfer
molding, D-LFT, compression and injection molding, and reaction
injection molding.
[0008] In its various embodiments, the present invention combines
the processes of forming and loading the inorganic component of a
reinforced resin with the ring-opening polymerization of a suitable
monomer. The invention thereby overcomes any high viscosity issue
associated with combining fibres with resins, provides improved
interfacial adhesion between the polymer matrix and the inorganic
reinforcing material, and thereby provides improved composite
materials.
BRIEF SUMMARY OF THE INVENTION
[0009] In one embodiment, the invention provides an inorganic
substrate, for example glass fibres in the form of continuous
strands, chopped strands, rovings, mats, etc., having bonded
thereto a "coupling activator" compound of the following formula
I:
S--X-A (I)
wherein S represents a silane coupling moiety through which the
compound is bonded to the inorganic substrate, A represents a
ring-opening polymerization activator moiety, or a blocked
precursor thereof, and X represents a linking moiety capable of
linking the S moiety and the A moiety. The polymerization activator
moiety or precursor is capable of participating in an in situ
ring-opening polymerization of a monomer in the presence of a
polymerization catalyst when exposed to ring-opening polymerization
conditions. As a result, the inorganic substrate of the invention
may be used as a ring-opening polymerization activator, alone or
with conventional polymerization activators, in the formation of
polymers that are reinforced with the inorganic material. As
examples of inorganic substrates, mention may be made of glass,
basalt, carbon fibres, carbon nanotubes, inorganic nanotubes, and
metal fibres. For the purposes of the present invention, carbon
nanotubes and carbon fibres are inorganic substrates. Glass
substrates of the invention are particularly useful in the
formation of glass-reinforced polyamides.
[0010] The surface of the substrate of the invention may contain a
coating of a sizing composition comprising a coupling activator
compound of formula I above. In one embodiment of the invention,
silane-functionalized isocyanate may be blocked with caprolactam to
produce 2-oxo-N-(3-(triethoxysilyl)propyl)azepane-1-carboxamide,
which can participate in the anionic ring-opening polymerization of
caprolactam monomer.
[0011] Blocked precursors of coupling activator compounds may
include isocyanates blocked with compounds other than the activator
compound. Under the processing conditions, such blocked isocyanate
would become unblocked to furnish free isocyanate. The isocyanate
may, under the reaction conditions, become blocked with the monomer
thus forming the polymerisation activator. The silane functionality
of the isocyanate compound may react with the substrate, such as
glass, thus leading to improved interfacial adhesion.
[0012] In another embodiment, the invention provides a process for
preparing a reinforced resin material, e.g. a glass-reinforced
resin polyamide. A sizing composition comprising a coupling
activator compound of formula I above may be applied to a glass
substrate. In one embodiment, the sized glass substrate may be
mixed with a lactam monomer, e.g. caprolactam, and a polymerization
catalyst to form a polymerization mixture that may then be exposed
to conditions sufficient to cause an in situ anionic ring-opening
polymerization of the lactam monomer. In another embodiment, the
sized glass substrate may be mixed with a cyclic olefin monomer,
e.g. norbornene, and a polymerization catalyst to form a
polymerization mixture that may then be exposed to conditions
sufficient to cause an in situ ring-opening metathesis
polymerization of the cyclic olefin monomer. The resulting
composite products comprise a matrix in which the glass substrate
is grafted onto the polymer, thereby substantially improving the
coupling between the glass and the polymer. This improved coupling
is expected to provide tougher composite materials.
[0013] In other embodiments, the invention provides processes for
forming a reinforced resin material into a solid mass of a
prescribed shape and size by conventional processing procedures,
e.g. reactive extrusion, resin transfer molding, pultrusion,
reaction injection molding, or any other suitable process.
[0014] These and other embodiments of the present invention are
described in greater detail in the detailed description of the
invention which follows.
DETAILED DESCRIPTION OF THE INVENTION
[0015] The invention relates to products and processes employing
certain compounds referred to herein as "coupling activator"
compounds because they serve both a coupling and a ring-opening
polymerization function. In general terms, coupling activator
compounds of the invention may be represented by the following
formula I:
S--X-A (I)
wherein S represents a silane coupling moiety capable of bonding to
the surface of an inorganic substrate, A represents a ring-opening
polymerization activator moiety or a blocked precursor thereof, and
X represents a linking moiety capable of linking the S moiety and
the A moiety. As examples of suitable X moieties, mention may be
made of alkyl, aryl, and alkyl-aryl groups. The linking group X may
be of any length, including null, in which case the activator
moiety A would be directly attached to the silane S.
[0016] The silane coupling moiety S may comprise any of the known
functional groups that react with the surface of an inorganic
substrate, e.g. an organosilane group. Compounds containing
organosilane groups are well known coupling agents in material
systems that consist of an inorganic (e.g. glass) and organic (e.g.
polymer) phase, and serve to covalently bond the organic groups in
the compound to groups on the inorganic surface. As one example, S
may comprise an organosilane group of the following formula II:
##STR00001##
wherein X is as defined in Formula I above; and R.sup.1, R.sup.2
and R.sup.3 may be the same or different and each may represent
alkyl, aryl, alkoxy, halogen, hydroxy, or a cyclic structure
wherein X is connected with one or more of R.sup.1, R.sup.2, and
R.sup.3.
[0017] The ring-opening polymerization activator moiety A may be
any known organic reactive group that participates in a
ring-opening polymerization reaction, which term includes anionic
ring-opening polymerization, cationic ring-opening polymerization
and ring-opening metathesis polymerization (ROMP). For example,
such reactive group may participate in the polymerization by
forming a reactive center where further cyclic monomers can join
after opening to provide a larger polymer chain through ionic
propagation.
[0018] In one embodiment, the A moiety may be a group that serves
the function of an activator in the anionic ring-opening
polymerization of a lactam or a lactone, e.g. A may be an
N-substituted imide group. Such polymerizations are well-known in
the art and will not be discussed herein in great detail. If
further reference is needed, these polymerization reactions are
discussed more completely in the patent literature, e.g. in U.S.
Pat. Nos. 3,621,001; 4,188,478; 5,864,007; 6,579,965; and the
patents cited therein, all of which are incorporated by reference
herein. Generally, these polymerizations are conducted at low
temperatures (80-160.degree. C.), below the melting point of the
resulting polyamides (which is typically above 200.degree. C.), and
typically employ, in addition to the activator compound, two other
components; i.e.: a lactam monomer and a polymerization catalyst.
The monomer component may be a lactam or lactone having from 3 to
12 carbon atoms in the main ring, such as caprolactam and
caprolactone. The polymerization catalyst may be an alkali metal
salt of the lactam or lactone monomer, such as sodium caprolactam
and sodium caprolactone. There may also be other known auxiliary
components in the polymerization mixture (e.g. co-initiators,
catalysts, co-catalysts, electron donors, accelerators,
sensitizers, processing aids, release agents, etc.).
[0019] In the anionic ring-opening polymerization of the lactam or
lactone monomer, the combination of monomer and polymerization
catalyst produces a catalyzed monomer species containing an atom
with a reactive free anion. As used herein, the term "ring-opening
polymerization activator" may be used to denote this catalyzed
monomer species, and the term "ring-opening polymerization
activator moiety" may be defined as a group that reacts with the
catalyzed monomer molecule to cleave the lactam ring and start the
initial growth of the polymeric chain. In one embodiment the
polymerization catalyst may comprise an alkali metal salt of the
lactam or lactone and the activator moiety may comprise an
N-substituted imide group, e.g. an N-acyl lactam group.
[0020] As another example, in the ring-opening metathesis
polymerization (ROMP) of a cyclic olefin monomer such a norbornene,
cyclopentadiene, cyclooctadiene, decyclopentadiene, etc., the A
moiety of the compound of Formula I above may be a cyclic
olefin-substituted imide group that undergoes ROMP under catalytic
conditions using an alkylidene catalyst such as developed by R. R.
Schrock or R. Grubbs. In this case the A moiety becomes part of the
polymer chain.
[0021] As specific examples of coupling activator compounds of
Formula I above that are useful in the anionic ring-opening
polymerization of lactams, mention may be made of certain
N-propylsilyl-N'-acyl-ureas described in U.S. Pat. No. 4,697,009,
incorporated by reference herein. In one embodiment, the coupling
activator compound may comprise
2-oxo-N-(3-(triethoxysilyl)propyl)azepane-1-carboxamide.
[0022] In one embodiment, the coupling activator compounds of the
invention may be prepared in accordance with the process set forth
in the aforementioned incorporated U.S. Pat. No. 4,697,009. For
example, the coupling activator compounds may be prepared by mixing
in an aprotic, polar organic solvent such as N,N-dimethylformamide
equimolar amounts of an alkali isocyanate (e.g. sodium isocyanate
or potassium isocyanate), a 3-halopropyl silane (e.g.
3-chloropropyltriethoxysilane) and caprolactam, and reacting the
ingredients with each other at elevated temperature. At the end of
the reaction and cooling the mixture to room temperature, the
precipitated alkali halide may be filtered off and the solvent may
be removed from the filtrate to obtain the desired blocked
isocyanate compound. Alternatively, coupling activator compounds
may be prepared according to the procedure described in
International Patent No. WO 2006/012957, incorporated herein by
reference
[0023] In another embodiment, the coupling activator,
2-oxo-N-(3-(triethoxysilyl)propyl)azepane-1-carboxamide may be
prepared in accordance with the following reaction scheme A:
##STR00002##
1.1 eq. of caprolactam 1 may be mixed with 1.0 eq. of
3-isocyanatopropyltriethoxysilane 2 and the mixture heated at
80-100.degree. C. until the completion of the reaction and
formation of
2-oxo-N-(3-(triethoxysilyl)propyl)azepane-1-carboxamide 3. The
reaction progress can be measured by FT-IR, where disappearance of
the isocyanate peak at 2300 cm.sup.-1 should be observed. The
reaction may be run neat or in solution, with 1,4-dioxane as the
solvent. Organotin catalyst (e.g. dibutyltin dilaurate) may be used
to significantly improve the reaction rate.
[0024] In one embodiment, a coupling activator compound of the
invention may be used as the sole initiator in a anionic
ring-opening polymerization reaction, or may be used in combination
with other known initiator compounds. For example, compound 3 above
may be used as the initiator in the reactive extrusion of Nylon-6
in accordance with the following reaction scheme B:
##STR00003##
[0025] In the above reaction, 97.5 wt % of caprolactam 1 may be
mixed with 1.5 wt % of the polymerization catalyst sodium
caprolactam 4, and 1.0 wt % of
2-oxo-N-(3-(triethoxysilyl)propyl)azepane-1-carboxamide 3. The
mixture may be fed into a zone 2 of a 15-zone, L/D=60 Leistritz
co-rotating 27-mm twin-screw extruder with temperature profile of
80-205.degree. C. at the screw speed of 78 min.sup.-1 at torque of
4.8-9.6 MPa to accomplish ring-opening polymerization and obtain
Nylon-6. Alternatively, the same results may be achieved by running
the reaction in a beaker instead of using the reactive extrusion
process.
[0026] In another embodiment, a coupling activator compound of the
invention may participate in a ROMP reaction such as shown in the
following reaction scheme C:
##STR00004##
[0027] In this case, norbornene-substituted maleic anhydride 6 may
be reacted with .gamma.-aminopropyltriethoxysilane 7 to provide a
substituted imide coupling activator compound 8. Coupling activator
compound 8 can then undergo ring-opening metathesis polymerization
(typically under catalytic conditions using rhodium, rhenium, or
molybdenum alkylidene catalysts such as were developed by Grubbs or
Schrock). Monomers such as cyclopentadiene, cyclooctadiene,
dicyclopentadiene, norbornene or other monomers suitable for ROMP
may be used to yield polymers such as illustrated by compound
9.
[0028] In another embodiment, the invention provides an inorganic
substrate having bonded thereto a coupling activator compound of
Formula I above. The inorganic substrate may comprise a plurality
of glass fibres wherein at least one glass fibre is at least
partially coated with the residue of a sizing composition
comprising the coupling activator compound. As previously
described, the silane coupling moiety S of the coupling activator
compound that is included in the coated sizing composition may
covalently bond to the glass fibre when the composition is coated
and dried on the glass substrate, thereby securely attaching the
coupling activator compound to the glass substrate.
[0029] Some embodiments of glass fibres according to the present
invention may be particularly suited for reinforcing polyamide
resins. Polyamide resins reinforced with glass fibres in accordance
with the invention may comprise Nylon 6, Nylon 6:6, Nylon 6:12,
Nylon 4:6, Nylon 6:10, Nylon 12, polyamide 6T (polyhexamethylene
terephthalamide), polyamide 6I (polyhexamethylene isophthalamide)
or mixtures thereof. In one embodiment, the A moiety of the
coupling activator compound in formula I above may comprise a
blocked precursor of the active activator moiety, e.g. a blocked
isocyanate. In this embodiment, the precursor compound may be
coated on the glass substrate and the active form of the activator
may be generated in situ on the surface of a glass substrate when
exposed to unblocking conditions. This process may be illustrated
by the reaction scheme D below:
##STR00005##
[0030] The blocked isocyanate group may be obtained by reacting the
isocyanate group of compound 2 in reaction scheme A above with a
compound that renders the isocyanate group unreactive. A suitable
blocking agent for the isocyanate group may be determined by its
ability to prevent the blocked isocyanate from reacting until a
desired temperature is achieved. Examples of compounds that may be
suitable blocking agents include, but are not limited to, oximes
such as methyl ethyl ketoxime, acetone oxime, and cyclohexanone
oxime, lactams such as .epsilon.-caprolactam, and pyrazoles.
Organosilicon compounds with a blocked isocyanate group are known
in the art, e.g. see U.S. Patent Publication 2007/0123644,
incorporated herein by reference. Upon heating or other deblocking
conditions, these blocked isocyanates decompose to free isocyanate
and the blocking species. Deblocking temperatures depend on the
blocking groups and typically are in the range 70-200.degree. C.
The blocked isocyanate may be included as a component of the sizing
composition used to size glass fibres, and may be applied to glass
fibres in the manner previously described to form the entity
identified as "blocked 2 on glass" in reaction scheme D above. When
the glass fibres with blocked isocyanate compound are exposed to
unblocking conditions, e.g. elevated temperatures during
processing, the isocyanate group may become unblocked to form the
active isocyanate compound 2 chemically bonded to the glass
surface. Now unblocked, the isocyanate group is available to react
with the caprolactam monomer 1 in reaction scheme A above, thereby
forming coupling activator compound 3 bonded to the glass surface.
The coupling activator compound may then enter into the in situ
polymerization reaction on the surface of the glass fibres in
accordance with the invention. If the isocyanate is blocked with a
monomer in the polymerization reaction; e.g. when the isocyanate is
blocked by capolactam in the anionic ring-opening polymerization of
caprolactam, the blocked isocyanate may not need to dissociate into
the free isocyanate in order to facilitate the ring-opening
polymerization reaction.
[0031] Sizing compositions suitable for the present invention may
be prepared by adding a coupling activator compound of formula I to
water or other suitable solvent to form a solution. The sizing
composition may also include other sizing composition components
known in the art, e.g. film-forming polymers, lubricants,
defoamers, biocides, other silanes, etc. The sizing composition
should contain an amount of coupling activator compound sufficient
to accomplish the desired participation in the ring-opening
polymerization. The overall concentration of the coupling activator
compound and other components in the sizing composition can be
adjusted over a wide range according to the means of application to
be used, the character of the inorganic reinforcing material to be
sized, and the intended use of the sized inorganic reinforcing
material. In one embodiment, the sizing composition may contain
about 5 wt % of the coupling activator compound. The components may
be added sequentially, or they may be pre-diluted before they are
combined to form the sizing composition.
[0032] The sizing composition may be applied to the inorganic
substrate by suitable methods known to one of skill in the art. For
example, the sizing composition may be applied to glass fibres
pulled from a bushing using a kiss-roll applicator. Other ways of
applying the sizing composition may include contacting glass fibres
with other static or dynamic applicators, such as a belt
applicator, spraying, dipping, or any other means. Alternatively,
the coupling activator compound may be added to the binder used in
the process of forming woven or non-woven mats.
[0033] After the sizing has been applied, fibres may be collected
in rovings or may be chopped to form chopped strands. Rovings of
continuous sized strands may be used in some applications, e.g. in
long-fibre thermoplastics, or the rovings may be comingled and may
be later chopped to a desired length. The length and diameter of
the chopped glass fibres used for reinforcing polyamide resins may
be determined by various factors such as, but not limited to, the
ease of handling when glass fibres are melt-kneaded with a
polyamide resin, the reinforcing effect of the glass fibres, glass
fibre dispersing ability, the type of polyamide resin in which the
chopped glass fibre will be used to reinforce and the intended use
of a glass-reinforced polyamide resin article. In some embodiments,
the length of the chopped glass fibre strand may have a lower limit
of 1 mm and an upper limit of length of 50 mm. In one embodiment
suitable for reinforcement of Nylon-6, the length of the strand may
be about 6 mm. After the fibre strands have been chopped, they may
then be dried until the moisture level of the fibres is
sufficiently low, e.g. below 0.1%.
[0034] Non-limiting examples of glass fibres suitable for use in
the present invention can include those prepared from fibresable
glass compositions such as "E-glass", "A-glass", "C-glass",
"S-glass", "ECR-glass" (corrosion resistant glass), "T-glass", and
fluorine and/or boron-free derivatives thereof. Typical
formulations of glass fibres are disclosed in K. Lowenstein, The
Manufacturing Technology of Continuous Glass Fibres (Third Ed.
1993), incorporated herein by reference.
[0035] The invention further provides reinforced resin materials
and processes for preparing them from an inorganic substrate that
has bonded thereto coupling activator compounds of the present
invention. In one embodiment, a sizing composition comprising the
coupling activator compound of Formula I may be applied to a glass
substrate, the sized glass substrate may be mixed with a lactam
monomer and a polymerization catalyst to form a polymerization
mixture; and the mixture may be exposed to conditions sufficient to
cause an in situ anionic ring-opening polymerization of the lactam
monomer, thereby forming a polymer/glass matrix in which the glass
substrate is grafted to the polyamide polymer. The polymerization
is referred to as "in situ" because the polymer is formed directly
on the surface of the glass substrate, as opposed to being first
formed and then coated on the glass surface. As a result, the
coupling of the glass component and the polymer component of the
composite material is substantially improved over prior art
glass-reinforced resins.
[0036] Reinforced resin materials of the invention may be produced
using well-known processing procedures such as reactive extrusion,
resin transfer molding, pultrusion, reaction transfer molding,
D-LFT, compression and injection molding, and reaction injection
molding. Example 1 below illustrates the production of
glass-reinforced polyamide-6 using the process of the invention in
a reactive extrusion process, and for comparative purposes, Example
2 below illustrates the production of a glass-reinforced
polyamide-6 using a conventional reactive extrusion process:
Example 1
[0037] Chopped fibre strands sized with a sizing composition
comprising 2-oxo-N-(3-(triethoxysilyl)propyl)azepane-1-carboxamide
(compound 3 in reaction scheme A above) may be fed into an extruder
as previously described. A monomer mix comprising caprolactam
monomer 1 and sodium caprolactam catalyst 4, as shown in reaction
scheme B above, may also be fed into the extruder to be mixed and
heated with the sized glass fibres. The processing conditions
within the extruder initiate and complete an anionic ring-opening
polymerization of caprolactam 1 in accordance with reaction scheme
B, and strands of the resulting glass-reinforced Nylon-6 may be
extruded through the extruder die. A sample strand of the
glass-reinforced Nylon-6 may be broken under tension. The breaking
point may be analyzed with a Scanning Electron Microscope (SEM) to
show the outstanding coupling of glass and polymer in the composite
material provided by the present invention.
Example 2
[0038] Chopped glass fibres strands may be sized with a
conventional sizing composition comprising 0-30 wt % of
.gamma.-aminopropyltriethoxysilane or other suitable silane
coupling agent, 20-70 wt % of a polyurethane emulsion or a suitable
mixture of emulsions, and 10-50 wt % of a lubricant or mixture of
lubricants, and 0-50 wt % of any other required or preferred
additives. The chopped sized fibres may be fed into the same
extruder used in Example 1 above. Referring to reaction scheme E
below, monomer mix comprising caprolactam monomer 1, sodium
caprolactam catalyst 4 and a commercially-available activator 5 may
also be fed into the extruder, thereby mixing and heating the mix
with the sized glass fibres. The processing conditions within the
extruder initiate and complete an anionic ring-opening
polymerization of the caprolactam monomer 1 within the extruder in
accordance with reaction scheme E below:
##STR00006##
[0039] Strands of the resulting Nylon-6 may then be obtained from
the extruder die and analysis of the breaking point of a broken
strand may be performed to show only average coupling between the
glass and the polymer matrix. The comparison between the products
of Examples 1 and 2 clearly demonstrate the unexpected and superior
results achieved by the present invention.
[0040] In another embodiment, substrates of the present invention
may be used in a resin transfer molding process. For example, glass
or other fibres or fibrous mats or fabrics, may be placed in a
closed mold and a mixture comprising lactam monomer and
polymerization catalyst may be transferred into the mold to form a
polymerization mixture. The mold walls may be heated to a
temperature sufficient to cause ring-opening polymerization of the
monomer and result in the formation of the glass-reinforced resin
material in the mold shape. The mold may then be opened to provide
a shaped glass-reinforced resin article. In another embodiment, the
present invention may be used to simplify the preparation of woven
or non-woven fabric laminates using vacuum-assisted resin transfer
molding. These materials may be used to make high-end composites
for applications such as wind turbine blades, automotive or
aircraft parts, and reinforced pressure vessels. Current processes
typically utilize a two-component application wherein a first
molten mixture comprising lactam monomer and polymerization
catalyst and a second molten mixture comprising lactam monomer and
activator compound are separately mixed with glass fibres
containing conventional sizing. In a vacuum-assisted resin transfer
molding process utilizing the present invention, only one mixture
comprising lactam monomer and polymerization catalyst may be used
to cover glass fibres containing a coupling activator compound of
Formula I.
[0041] In another embodiment, the process of the invention may
comprise using the sized substrates in a pultrusion process. For
example, glass fibres containing a coupling activator compound of
Formula I may be pulled from a creel through a bath comprising a
composition of lactam monomer and polymerization catalyst to
impregnate the fibres. The impregnated glass fibres may then enter
a heated die that has been machined to the final shape of the
article to be produced. While the impregnated glass fibres are
being pulled through the die, the heat causes polymerization of the
lactam monomer and the formation of the glass-reinforced resin,
which exits the die in the desired shape. The shaped resin may then
be cut to the desired length.
[0042] In still another embodiment, the process of the invention
may comprise using substrates containing a coupling activator
compound of Formula I in a reaction injection molding process. For
example, glass fibres sized with a compound of Formula I may be
dispersed in a liquid composition comprising lactam monomer and
polymerization catalyst. The liquid composition may then be
injected into a mold and heated to cause anionic ring-opening
polymerization of the lactam monomer. After polymerization is
completed, the shaped glass-reinforced resin may be removed from
the mold.
[0043] One skilled in the art can easily ascertain the essential
characteristics of this invention from the foregoing description,
and without departing from the spirit and scope thereof, can make
various changes and modifications of the invention to adapt it to
various usages and conditions.
* * * * *