U.S. patent application number 16/561344 was filed with the patent office on 2021-12-23 for manufacturing thermoplastic composites and articles.
The applicant listed for this patent is JOHNS MANVILLE. Invention is credited to Jawed Asrar, Michael Block, Daniel P De Kock, Klaus Friedrich Gleich, Asheber Yohannes, Mingfu Zhang.
Application Number | 20210397410 16/561344 |
Document ID | / |
Family ID | 1000006010521 |
Filed Date | 2021-12-23 |
United States Patent
Application |
20210397410 |
Kind Code |
A9 |
Zhang; Mingfu ; et
al. |
December 23, 2021 |
MANUFACTURING THERMOPLASTIC COMPOSITES AND ARTICLES
Abstract
Embodiments of the present technology may include a method of
making a thermoplastic composite concentrates. The method may
include melting a low-viscosity reactive resin to form a molten
reactive resin. The method may also include fully impregnating a
plurality of continuous fibers with the molten reactive resin in an
impregnation device. The method may further include polymerizing
the molten reactive resin to form a thermoplastic composite strand.
In addition, the method may include chopping the thermoplastic
composite strand into a plurality of pellets to form a plurality of
thermoplastic composite concentrates.
Inventors: |
Zhang; Mingfu; (Englewood,
CO) ; Yohannes; Asheber; (Littleton, CO) ;
Block; Michael; (Centennial, CO) ; Gleich; Klaus
Friedrich; (Nuremberg, DE) ; De Kock; Daniel P;
(Assenede, BE) ; Asrar; Jawed; (Englewood,
CO) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
JOHNS MANVILLE |
Denver |
CO |
US |
|
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20200004499 A1 |
January 2, 2020 |
|
|
Family ID: |
1000006010521 |
Appl. No.: |
16/561344 |
Filed: |
September 5, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
15164434 |
May 25, 2016 |
10442115 |
|
|
16561344 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04M 1/72412 20210101;
G10L 15/22 20130101; H04M 1/6075 20130101; G06F 3/165 20130101;
H04M 1/72463 20210101; G06F 3/048 20130101; G10L 15/26 20130101;
H03G 3/3005 20130101; G06F 3/167 20130101; H04M 1/72454 20210101;
G06F 3/04847 20130101 |
International
Class: |
G06F 3/16 20060101
G06F003/16; G10L 15/22 20060101 G10L015/22; H04M 1/60 20060101
H04M001/60; H04M 1/725 20060101 H04M001/725; G06F 3/048 20060101
G06F003/048; G06F 3/0484 20060101 G06F003/0484; G10L 15/26 20060101
G10L015/26; H03G 3/30 20060101 H03G003/30 |
Claims
1. A method of making thermoplastic composite concentrates, the
method comprising: melting a low-viscosity reactive resin to form a
molten reactive resin in an extruder; fully impregnating a
plurality of continuous fibers with the molten reactive resin in an
impregnation device; polymerizing the molten reactive resin to form
a thermoplastic composite strand; and chopping the thermoplastic
composite strand into a plurality of pellets to form a plurality of
thermoplastic composite concentrates.
2. The method of claim 1, wherein polymerizing the molten reactive
resin to form the thermoplastic composite strand comprises
polymerizing the molten reactive resin in a polymerization
device.
3. The method of claim 1, wherein the thermoplastic composite
concentrates comprises a thermoplastic composite concentrate
comprising greater than or equal to 40 wt. % glass fiber.
4. The method of claim 1, wherein polymerizing the molten reactive
resin to form the thermoplastic composite strand comprises:
polymerizing the molten reactive resin to form a thermoplastic
resin matrix; and cooling the thermoplastic resin matrix to form
the thermoplastic composite strand.
5. The method of claim 1, wherein fully impregnating the plurality
of continuous fibers with the molten reactive resin comprises
injecting the molten reactive resin into the impregnation
device.
6. The method of claim 1, wherein the plurality of pellets
comprises a pellet having a length, and the pellet comprises a
fiber having the length, wherein the length is 1 mm or more.
7. The method of claim 1, wherein the plurality of continuous
fibers is a roving.
8. The method of claim 1, wherein: the low-viscosity reactive resin
comprises monomers; melting the low-viscosity reactive resin
comprises forming oligomers from the monomers in the low-viscosity
reactive resin; and polymerizing the molten reactive resin
comprises polymerizing the oligomers into polymers.
9. The method of claim 1, wherein: the low-viscosity reactive resin
comprises monomers or oligomers, and polymerizing the molten
reactive resin comprises polymerizing the monomers or oligomers
into polymers.
10. A method of making a composite article, the method comprising:
melting a low-viscosity reactive resin to form a molten reactive
resin in an extruder; fully impregnating a plurality of continuous
fibers with the molten reactive resin in an impregnation device;
polymerizing the molten reactive resin to form a thermoplastic
composite strand; and chopping the thermoplastic composite strand
into a plurality of pellets to form a plurality of thermoplastic
composite concentrates, wherein the plurality of thermoplastic
composite concentrates comprises fibers fully impregnated with a
first thermoplastic resin. mixing the plurality of thermoplastic
composite concentrates with a second thermoplastic resin to form a
mixture; and forming the composite article from the mixture.
11. The method of claim 10, wherein the composite article comprises
greater than 10 wt. % glass fiber.
12. The method of claim 10, further comprising processing the
mixture through an injection molding, a compression molding
process, or a local reinforcement process.
13. The method of claim 10, wherein the first thermoplastic resin
comprises a polyamide-6 produced by in situ anionic polymerization
of caprolactam, and the second thermoplastic resin comprises a
hydrolytically polymerized polyamide-6.
14. A system for making a thermoplastic composite strand, the
system comprising: a melting device positioned to receive a
low-viscosity reactive resin, wherein the melting device is
operable to maintain a temperature equal to or greater than a
polymerization temperature of the low-viscosity reactive resin; an
impregnation device, wherein the impregnation device is: positioned
to receive a molten reactive resin from the melting device; and
operable to combine a plurality of continuous fibers with the
molten reactive resin; and a polymerization device, wherein the
polymerization device is: positioned to receive the plurality of
continuous fibers impregnated with the molten reactive resin from
the impregnation device; and operable to polymerize the molten
reactive resin to form the thermoplastic composite strand.
15. The system of claim 14, wherein the melting device comprises an
extruder.
16. The system of claim 14, wherein the polymerization device
comprises a curing oven.
17. The system of claim 16, wherein the curing oven is operable to
flow dry nitrogen or an inert gas through the curing oven.
18. The system of claim 14, wherein the impregnation device
comprises a cross-head die and wherein the impregnation device is
operable to contain the molten reactive resin before the molten
reactive resin impregnates the plurality of continuous fibers.
19. The system of claim 14, wherein the impregnation device is
operable to bring the molten reactive resin into contact with the
plurality of continuous fibers.
20. The system of claim 14, wherein the system further comprises a
molding device operable to receive the thermoplastic composite
strand and to mold the thermoplastic composite strand into a
composite article.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of U.S. Ser. No.
15/164,434, filed May 25, 2016, all of which is incorporated herein
by reference.
BACKGROUND
[0002] Thermoset plastics are favored for making many kinds of
fiber-reinforced articles because of their ease of manufacture.
Uncured thermosets are often low viscosity liquids at room
temperature and easily wet a fabric of fibers. Once they have
migrated through the fabric and surrounded its fibers, a curing
stage (sometimes called a hardening stage) commences to polymerize
the thermoset into a polymer matrix. Often, this wetting and curing
takes place in a mold that defines the shape of the
fiber-reinforced article.
[0003] The uncured thermoset resins used to make the composite are
generally inexpensive, but often off-gas irritating and sometimes
dangerous volatile organic compounds (VOCs). The outgassing of VOCs
are of particular concern during curing, when the exothermic nature
of many thermoset curing reactions raise the temperature of the
composite and drive more VOCs into the gas phase. In many
instances, it is necessary to cure large thermoset articles in
facilities equipped with robust ventilation and air scrubbing
equipment, increasing the overall production costs.
[0004] Thermoset articles are also difficult to repair or recycle.
Hardened thermoset resins often have a high degree of crosslinking,
making them prone to fractures and breaks. Because thermosets
normally will not melt under heat, they have to be replaced instead
of repaired by welding. Compounding difficulties, the unrepairable
thermoset part normally cannot be recycled into new articles, but
must instead be landfilled at significant cost and adverse impact
on the environment. The problems are particularly acute when large
thermoset parts, such as automotive panels and wind turbine blades,
need to be replaced.
[0005] Because of these and other difficulties, thermoplastic resin
systems are being developed for fiber-reinforced articles that were
once exclusively made using thermosets. Thermoplastics typically
have higher fracture toughness and chemical resistance than
thermosets. They also melt at raised temperatures, allowing
operators to heal cracks and weld together pieces instead of having
to replace a damaged part. Perhaps most significantly, discarded
thermoplastic parts can be broken down and recycled into new
articles, reducing landfill costs and stress on the
environment.
[0006] Unfortunately, thermoplastic composites have their own
challenges. High melt viscosities of thermoplastic polymer resins
may cause difficulties in impregnating reinforcing fibers.
Conventional techniques for producing thermoplastic composites,
such as extrusion compounding, break fibers down to very short
lengths, which limits mechanical properties of composite articles.
Existing processes to produce thermoplastic composites containing
long or continuous fibers often result in incomplete resin
impregnation and poor bonding between thermoplastic matrix and
reinforcing fibers. Thus, there is a need to develop new ways to
improve mechanical properties of the thermoplastic composite
materials. These and other issues are addressed in the present
application.
BRIEF SUMMARY
[0007] Methods of making and using fiber-resin compositions in the
construction of fiber-reinforced thermoplastic composite articles
are described. The present compositions include the combination of
reactive thermoplastic resin compositions and continuous fibers,
including rovings. The reactive resin composition may be melted in
a melting device, such as an extruder, and subsequently combined
with the fibers. The low-viscosity reactive thermoplastic resin
compositions are significantly easier to wet and mix with the
fibers compared to a high-viscosity melt of the polymerized
thermoplastic resin. Fiber-resin compositions may also have long
fibers, where the length of the fiber is equal or about equal to
the length of a fiber-resin pellet. Composite articles produced by
methods described herein have improved mechanical properties,
including increased tensile strength, impact strength, and
stiffness.
[0008] Embodiments of the present technology may include a method
of making a thermoplastic composite. The method may include melting
a reactive thermoplastic resin to form a molten reactive resin. The
method may also include fully impregnating a plurality of
continuous fibers, such as rovings, with the molten reactive resin
in an impregnation device. The method may further include
polymerizing the molten reactive resin to form a thermoplastic
matrix. The resulting thermoplastic composite may include the
plurality of fibers and a polymerized resin.
[0009] Embodiments may also include a method of making a composite
article. The method may include melting a reactive thermoplastic
resin. The method may also include fully impregnating a roving with
the molten reactive resin in an impregnation device. The method may
further include polymerizing the molten reactive resin to form a
thermoplastic composite strand comprising the roving and a
polymerized resin. The method may further include chopping the
thermoplastic composite strand into pellets. Furthermore, the
method may include mixing the thermoplastic composite pellets with
a second thermoplastic resin to form a mixture. The method may also
include forming the mixture of the thermoplastic composite pellets
and the second thermoplastic resin into composite article.
[0010] Some embodiments may include a method of making a
thermoplastic composite. The method may include melting in an
extruder a reactive thermoplastic resin to form a molten reactive
resin. The method may also include fully impregnating a roving with
the molten reactive resin in an impregnation device. The method may
further include polymerizing the molten reactive resin to form a
thermoplastic composite strand comprising the roving and a
thermoplastic resin. The thermoplastic composite strand may
comprise rovings fully impregnated with a thermoplastic resin.
[0011] Embodiments may also include a thermoplastic composite
formed by any of the methods described herein. The thermoplastic
composite may include continuous strands, or the thermoplastic
composite may include pellets.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] A further understanding of the nature and advantages of the
present invention may be realized by reference to the remaining
portions of the specification and the drawings wherein like
reference numerals are used throughout the several drawings to
refer to similar components. In some instances, a sublabel is
associated with a reference numeral and follows a hyphen to denote
one of multiple similar components. When reference is made to a
reference numeral without specification to an existing sublabel, it
is intended to refer to all such multiple similar components.
[0013] FIG. 1 shows a method of making a thermoplastic composite
strand according to embodiments of the present technology.
[0014] FIG. 2 shows a method of making a composite article
according to embodiments of the present technology.
[0015] FIG. 3 shows an example system for making fiber-resin
composites and fiber-reinforced articles according to embodiments
of the present technology.
[0016] FIG. 4 shows an example fiber-reinforced article made
according to the embodiments of the present technology.
DETAILED DESCRIPTION
[0017] Conventional methods of forming fiber-thermoplastic resin
compositions include compounding and long fiber thermoplastic (LFT)
processes. These conventional processes involve melts of
thermoplastic polymers, which lead to less than ideal compositions.
In conventional compounding process, fibers may be fed into an
extruder, and as a result of this process, fibers may be reduced to
a length of less than 1 mm. The small length of the fibers in a
fiber-resin composition decreases the strength and other mechanical
properties of the final composite article. Conventional LFT
processes involve longer fibers but include high viscosity
thermoplastic polymer melts. The high viscosity thermoplastic
polymer melts may not wet fibers as effectively as low viscosity
reactive resins, which may result in incomplete resin impregnation
of fibers and/or voids in a fiber-resin composition. The high
processing temperature needed to melt thermoplastic polymers may
also lead to undesired degradation reactions. Roving coating
processes, such as wire coating, may coat a continuous roving.
However conventional roving coating processes again involve high
viscosity thermoplastic resins, which often leads to surface
coating of the roving and does not result in a fully impregnated
roving. The fiber-resin composition and composite articles
resulting from conventional processes may lack the superior
mechanical properties of compositions and methods of the present
application.
[0018] The present application includes methods of making exemplary
fiber-resin compositions from reactive thermoplastic resin
compositions that include low-viscosity melts of monomers and/or
oligomers that can polymerize into a thermoplastic resin holding
the fibers. The low-viscosity reactive thermoplastic resin
compositions are significantly easier to wet fibers compared to a
highly viscous melt of the thermoplastic polymer resin. Reactive
thermoplastic resins may polymerize at a temperature lower than the
melting point of the corresponding thermoplastic polymers, allowing
for more process flexibility and reduced manufacturing cost. The
fiber-resin compositions may be combined with a second
thermoplastic resin and formed into a fiber-reinforced composite
article using a variety of thermoplastic molding techniques,
including injection molding, compression molding, and local
reinforcement. In some instances, a second thermoplastic resin may
be added to the fiber-resin composition and the resulting
composition may be injection molded. Tensile strength, impact
strength, or modulus (stiffness) may increase over conventional
processes. Details about the methods and systems used to make the
exemplary fiber-reinforced compositions and composite articles are
described below.
Exemplary Fibers
[0019] The fibers may be one or more types of fibers chosen from
glass fibers, ceramic fibers, carbon fibers, metal fibers, and
organic polymer fibers, among other kinds of fibers. Exemplary
glass fibers may include "E-glass", "A-glass", "C-glass",
"S-glass", "ECR-glass" (corrosion resistant glass), "T-glass", and
fluorine and/or boron-free derivatives thereof. Exemplary ceramic
fibers may include aluminum oxide, silicon carbide, silicon
nitride, silicon carbide, and basalt fibers, among others.
Exemplary carbon fibers may include graphite, semi-crystalline
carbon, and carbon nano tubes, among other types of carbon fibers.
Exemplary metal fibers may include aluminum, steel, and tungsten,
among other types of metal fibers. Exemplary organic polymer fibers
may include aramid fibers, polyester fibers, and polyamide fibers,
among other types of organic polymer fibers. Fibers may include
natural fibers, which may include wood fibers, cellulose fibers,
manmade fibers based on natural resources (e.g., lignin), or
combinations thereof.
Exemplary Reactive Thermoplastic Resin Compositions
[0020] Reactive thermoplastic resin compositions may include
monomers and/or oligomers capable of polymerizing into a
thermoplastic resin matrix that binds the plurality of fibers.
Exemplary reactive resin compositions may include caprolactam.
Caprolactam is a cyclic amide of caproic acid with an empirical
formula (CH.sub.2).sub.5C(O)NH, which may be represented by the
structural formula:
##STR00001##
[0021] Caprolactam has a low melting point of approximately
68.degree. C. and a melted viscosity (0.004-0.008 Pas) that is
close to water, making it well suited for wetting and mixing with
reinforcing fibers. Typically, the caprolactam-containing reactive
resin composition may be introduced to the plurality of fibers as a
liquid melt.
[0022] Caprolactam-containing reactive resin compositions may also
include polymerization agents such as a polymerization catalyst or
a polymerization activator. Exemplary polymerization catalysts may
include a salt of a lactam, and the salt may be an alkali metal
salt, an alkali-earth metal salt, and/or a Grignard salt of the
caprolactam. For example the polymerization catalyst may be an
alkali metal salt of caprolactam, such as sodium caprolactam. In
another example, the polymerization catalyst may be a Grignard salt
of the caprolactam, such as a magnesium bromide salt of the
caprolactam. As used herein, a polymerization activator may be any
material that activates the polymerization of monomers or
oligomers. Exemplary activators for the anionic polymerization of
caprolactam include caprolactam blocked isocyanates and
N-acylcaprolactams. Polymerization agents may also be present on
the fibers, and in some instances a polymerization agent may be
present both in the reactive resin composition and on the fibers.
Incorporating a polymerization agent on the reinforcing fibers can
render the fibers reactive, and reduce or eliminate its presence in
the reactive resin composition, which may increase the pot-life of
the reactive resin composition prior to being applied to the
fibers.
[0023] Exemplary reactive resin compositions may also include
additional type of lactam compounds, such as laurolactam, a cyclic
amide where the heterocyclic ring includes 12 carbon atoms
(C.sub.12H.sub.23NO).
[0024] Exemplary reactive resin compositions may also include
oligomers of a cyclic alkylene terephthalate, such as cyclic
butylene terephthalate (CBT). An exemplary CBT, whose ring includes
two butylene groups and two terephthalate groups, is illustrated
below:
##STR00002##
[0025] It should be appreciated that the present CBT may include
additional butylene and/or terephthalate groups incorporated into
the ring. It should also be appreciated that some exemplary CBT may
have other moieties coupled to the CBT ring. CBT may include a
plurality of dimers, trimers, tetramers, etc., of butylene
terephthalate.
[0026] CBT resins are typically solids at room temperature (e.g.,
about 20.degree. C.), and begin to melt at around 120.degree. C. At
around 160.degree. C., CBTs are generally fully melted with a
liquid viscosity of about 0.15 Pas. As the molten CBTs are heated
further, the viscosity may continue to drop, and in some instances
may reach about 0.03 Pas at about 190.degree. C. The CBT oligomers
may be selected to have a melting temperature range of, for
example, 120-190.degree. C.
[0027] CBT-containing reactive resin compositions may be introduced
to the plurality of fibers as a melt. The reactive resin
composition may include additional compounds such as polymerization
catalysts, polymerization promoters, colorants, flame retardants,
ultraviolet stabilizers, and fillers including inorganic particles
and carbon nanotubes, among other additional compounds. When the
resin is a CBT, the polymerization catalyst is selected to drive
the polymerization of these types of macrocyclic oligoesters.
Exemplary polymerization catalysts may include organometallic
compounds such as organo-tin compounds and/or organo-titanate
compounds. One specific polymerization catalyst for the CBT
oligomers may be butyltin chloride dihydroxide.
[0028] The CBT-containing reactive resin composition may also
include a polymerization promoter that accelerates the
polymerization rate of the oligomers. When the resin is CBT, the
polymerization promoter may by an alcohol and/or epoxide compound.
Exemplary alcohols may include one or more hydroxyl groups, such as
mono-alcohols (e.g., butanol), diols (e.g., ethylene glycol,
2-ethyl-1,3-hexanediol, bis(4-hydroxybutyl)terephthalate), triols,
and other polyols. Exemplary epoxides may include one or more
epoxide groups such as monoepoxide, diepoxide, and higher epoxides,
such as bisphenol A diglycidylether. They may also include polyol
and polyepoxides, such as poly(ethylene glycol).
[0029] Additional reactive resin compositions may include
compositions of monomers and/or oligomers that polymerize into
polymers such as polyamides, polyesters, thermoplastic polyurethane
(TPU), polyacrylates including polymethyl methacrylate (PMMA) and
poly(hydroxyl-ethyl methacrylate), or mixtures thereof. These
reactive resin compositions may include a polymerization agent,
such as a polymerization initiator or catalyst.
[0030] Thermoplastic resins may be formed from in situ
polymerization of monomers and/or oligomers in reactive
thermoplastic resin. Exemplary thermoplastic resins may include
polyamides, polybutylene terephthalate (PBT), thermoplastic
polyurethane (TPU), polymethyl methacrylate (PMMA),
poly(hydroxyl-ethyl methacrylate), or mixtures thereof. Specific
examples of polyamides may include polyamide-6, polyamide-12, among
other polyamide polymers. The thermoplastic polymer may also
include copolymers, such as the polyamide copolymer from the
anionic co-polymerization of caprolactam and laurolactam.
Exemplary Reactive Thermoplastic Resin Combinations
[0031] The reactive thermoplastic resin compositions may include a
single type of monomer and/or oligomer such as caprolactam or CBT,
or alternatively may include two or more types of monomers and/or
oligomers. For example, the reactive resin composition may include
both caprolactam and laurolactam. The addition of laurolactam as
co-monomer to caprolactam can improve the impact strength and
increase water resistance of the resulting thermoplastic resin
matrix. Additional reactive resin compositions may include
combinations of first and second resin systems having different
polymerization temperatures. This may allow the formation of a
semi-reactive fiber-resin composition that contains a polymerized
resin of the first resin system having a lower polymerization
temperature, while also containing unpolymerized monomers/oligomers
of the second resin system having a higher polymerization
temperature. For example, a reactive resin combination of
caprolactam and CBT may be selected such that the CBT has a higher
polymerization temperature than the caprolactam. Alternatively, a
reactive resin combination can be formulated of two different types
of cyclic alkylene terephthalates and/or a bimodal molecular weight
distribution of CBT oligomers having different polymerization
temperatures.
Exemplary Methods and Products
Composite Strands
[0032] As shown in FIG. 1, embodiments of the present technology
may include a method 100 of making a thermoplastic composite
strand. Method 100 may include melting a reactive thermoplastic
resin to form a molten reactive resin (block 102). An extruder may
be used to melt the reactive thermoplastic resin. The reactive
thermoplastic resin may initially include only monomers and no
oligomers. The reactive thermoplastic resin may have a low
viscosity. Exemplary reactive thermoplastic resins may have a
viscosity lower than 0.1 Pas. Partially as a result of the low
viscosity of the reactive thermoplastic resin, the reactive resin
can more easily wet and coat the plurality of fibers than in
conventional processes such as LFT, where highly viscous
thermoplastic polymer melts are used. The low viscosity reactive
resin also may reduce the formation of bubbles or voids in the
resin.
[0033] The reactive thermoplastic resin may include a
polymerization agent. The polymerization agent may be a
polymerization initiator, a polymerization catalyst, a
polymerization activator, or combinations thereof. The
polymerization initiator may initiate polymerization of the
monomers or oligomers. The polymerization catalyst may catalyze a
polymerization reaction. A reactive thermoplastic resin may be a
resin that contains components that can polymerize in situ under
certain conditions.
[0034] The molten reactive resin may be fed into an impregnation
device to impregnate a plurality of fibers. Because the viscosity
of the reactive resin is very low (<0.1 Pas), the reactive resin
may be injected into the impregnation device by typical liquid
handling techniques.
[0035] Method 100 may also include fully impregnating a plurality
of continuous fibers with the molten reactive resin in an
impregnation device (block 104). The fibers may be any fiber
described herein or combinations thereof. The plurality of
continuous fibers may include a roving. With a roving, the molten
reactive resin may fully impregnate the fibers in the roving. Fully
impregnated may mean that the fibers are completely wetted or
impregnated with the reactive resin composition. Substantially no
voids in coverage of the surface of the fibers may be present.
Higher fiber content may be achieved through the method of the
present invention. For example, greater than 40%, greater than 60%,
or greater than 80% by weight of fiber content, including up to
about 90% by weight of fiber content, may be achieved.
[0036] The fibers may have been sized with a sizing composition.
The sizing composition may be applied to fibers prior to the
impregnation with the reactive resin. The sizing composition may
include a silane coupling agent. Exemplary silane coupling agents
may include gamma-aminopropyltriethoxysilane. The silane coupling
agent may include a coupling activator compound of the formula,
S-X-A. S may represent a silane coupling moiety capable of bonding
to the fiber. A may represent an anionic ring-opening
polymerization activator moiety or a blocked precursor thereof. X
may represent an alkyl, aryl, or alkyl-aryl linking moiety. The
silane coupling agent may include
2-oxo-N-(3-(triethoxysilyl)propyl)azepane-1-carboxamide. Silane
coupling agents may be any coupling activator compound described in
U.S. Patent Publication No. 2011/0045275 and U.S. Patent
Publication No. 2015/0148498, which are incorporated herein by
reference for all purposes.
[0037] The impregnation device may be an impregnation die,
including a cross-head die. The impregnation die may be configured
to contain the reactive resin. While high viscosity resins,
including polymerized thermoplastic resins, may not easily flow
through spaces in an impregnation die, a low viscosity reactive
thermoplastic resin may. As a result, an impregnation die for
reactive thermoplastic resin should be configured to minimize
spaces within the die, so that the molten reactive resin injected
to the die may be completely absorbed by the moving fibers. In this
manner, solid polymers forming in the die may be avoided.
[0038] Method 100 may further include polymerizing the molten
reactive resin to form a thermoplastic resin matrix (block 106).
The resulting thermoplastic composite strand may include the
plurality of fibers and a polymerized resin. Monomers and oligomers
in the reactive thermoplastic resin may include precursors of
polyamides, polybutylene terephthalate (PBT), thermoplastic
polyurethane (TPU), polymethyl methacrylate (PMMA),
poly(hydroxyl-ethyl methacrylate), or mixtures thereof. For
example, the reactive resin may include lactams, macrocyclic
polyesters, acrylates, or mixtures thereof. Polymerizing may
include polymerizing monomers or oligomer precursors into
polyamide, and polymerizing may include anionically polymerizing
caprolactam into polyamide-6. Polymerizing the monomers or
oligomers may include pulling the plurality of impregnated fibers
or the roving coated with the molten reactive resin through a
curing oven. The molten reactive resin may include or exclude
either monomers or oligomers. In some embodiments, the exposure of
the reactive resin to moisture may be minimized. Polymerizing may
be done in the absence of moisture, which may be detrimental to
polymerizations such as the anionic polymerization of caprolactam.
Flowing nitrogen or an inert gas in the curing oven may help
prevent the exposure to moisture during the polymerization
process.
[0039] In addition, method 100 may include cooling the
thermoplastic resin matrix to form the thermoplastic composite
strand (block 108). The thermoplastic composite strand may contain
greater than 40% by weight, 60% by weight, or 80% by weight,
including up to about 90% by weight of fibers. The composite strand
may be a plurality of continuous fibers coated with a solid
thermoplastic resin. In some embodiments, the method may include
winding the composite strand. For example, the composite thread may
be wound around a spool or similar device.
[0040] Some embodiments may include a method of making a
thermoplastic composite. The method may include melting in an
extruder a reactive thermoplastic resin to form a molten reactive
thermoplastic resin. The method may also include fully impregnating
a roving with the molten reactive thermoplastic resin in an
impregnation device. The roving may not pass through the extruder.
The method may further include polymerizing the molten reactive
resin to form a thermoplastic matrix. In addition, the method may
include cooling the thermoplastic matrix to form a thermoplastic
composite strand. The thermoplastic composite strand may comprise
continuous fibers fully impregnated with a thermoplastic resin.
[0041] Embodiments may also include a thermoplastic composite
formed by any of the methods described herein. The thermoplastic
composite may include a continuous strand.
Thermoplastic Composite Concentrates
[0042] In some embodiments, the thermoplastic composite strand may
be chopped into a plurality of pellets. In some embodiments, the
plurality of pellets may include a pellet with a length of 1 mm or
more, 3 mm or more, 6 mm or more, 12 mm or more, or 25 mm or more.
The plurality of pellets may include fibers having the same length
as the length of the pellet. The average length of the pellets may
be the average length of the fibers. The average length may be any
length described herein. The average may be the mean, median, or
mode.
[0043] In some embodiments, 40% or more, 60% or more, or 80% or
more by weight of the thermoplastic composite pellet may be glass
fiber. In other embodiments, 70 wt. % or more may be glass fiber.
The rest of the thermoplastic composite pellet may be resin.
Conventional extrusion compounding processes may result in glass
fiber weight percentages of around 30 wt. %. By contrast, these
high fiber content thermoplastic composite pellets, which may be
termed thermoplastic composite concentrates, may allow for blending
with additional thermoplastic resins to achieve desired fiber
content. In addition, these thermoplastic composite concentrates
may be combined with additional thermoplastic resins for the
manufacturing of composite articles, and the fiber content in a
composite article may be tailored for a specific application. In
some embodiments, thermoplastic composite concentrates may be in
pellet form.
Composite Articles
[0044] As seen in FIG. 2, embodiments may also include a method 200
of making a composite article. Method 200 may include melting a
reactive thermoplastic resin to form a molten reactive resin (block
202). The reactive resin may be any resin described herein.
[0045] Method 200 may also include fully impregnating a roving with
the molten reactive resin in an impregnation device (block 204).
The roving may include any plurality of fibers described herein.
The impregnation device may be any impregnation device described
herein.
[0046] Method 200 may further include polymerizing the molten
reactive resin to form a thermoplastic resin matrix (block
206).
[0047] Additionally, method 200 may include cooling the
thermoplastic resin matrix to form a thermoplastic composite strand
including fibers fully impregnated with a first thermoplastic resin
(block 208). The thermoplastic composite strand may include
composites with high weight percentages of glass fiber.
[0048] Method 200 may further include forming a plurality of
pellets from the thermoplastic composite strand. Pellets may be any
pellets described herein. In some embodiments, composites may
include a continuous fiber and not be chopped into pellets.
[0049] Furthermore, method 200 may include mixing the thermoplastic
composite with a second thermoplastic resin to form a mixture
(block 210). The mixture of the thermoplastic composite pellets and
the second thermoplastic resin may be used to produce thermoplastic
composite article.
[0050] The second thermoplastic resin may be a polymerized
thermoplastic resin. Exemplary polymerized thermoplastic resins may
include polyamide-6 that is produced from the hydrolytic
polymerization of caprolactam. Exemplary polymerized thermoplastic
resins may also include polybutylene terephthalate (PBT) that is
produced by the condensation polymerization of butanediol and
terephthalic acid. The second thermoplastic resin may be in a solid
form, including powder, pellets, or spheres.
[0051] Method 200 may also include forming the mixture of the
thermoplastic composite pellets and the second thermoplastic resin
into the composite article (block 212). The composite article may
include greater than 10 wt. %, 20 wt. %, or 30 wt. % glass fiber.
Forming the composite article may include transferring the mixture
to a mold or molding the mixture. Method 200 may include processing
the mixture through an injection molding process or a compression
molding process. Embodiments may include a composite article formed
by any method described herein.
[0052] Methods described herein may include pellets or other
composites with full resin impregnation. What is more, methods may
include incorporating high molecular weight thermoplastics in the
composite article. Higher molecular weight thermoplastic polymers
may be formed via the in-situ polymerization described herein, as
compared to the thermoplastic polymers used in conventional polymer
melt processing. Higher molecular weight thermoplastic polymer
resins may not be possible or practical with conventional processes
because such thermoplastic resins would have prohibitively high
viscosities. As a result of these and other reasons, the composite
article may have mechanical properties superior to a composite
article produced by a conventional process, including extrusion
compounding and LFT.
Oligomerizing the Reactive Thermoplastic Resin
[0053] In some embodiments, the reactive thermoplastic resin may be
melted at a temperature equal to or greater than the polymerization
temperature. For example, the extruder may be run at the
polymerization temperature for a limited time. As a result, some,
substantially all, or all of the monomers in the reactive resin may
form oligomers. Methods, such as method 100 and method 200, may
further include polymerizing the oligomers into polymers. Forming
oligomers in the extruder and polymerizing the resulting oligomers
instead of monomers may reduce polymerization time after the resin
is contacted with fibers, may increase throughput, and may decrease
capital costs for equipment.
Exemplary Composition and Article Fabrication Systems
[0054] FIG. 3 shows an exemplary system 300 for making the present
fiber-resin composites and fiber-reinforced articles. The system
300 includes a supply of a reactive thermoplastic resin composition
302 fed to an extruder 304. The melted reactive resin composition
and a supply of continuous fibers 306 can be fed to an impregnation
device 308. The reactive resin coated on the fibers is then
polymerized in a polymerization device 310 to form a thermoplastic
resin matrix.
[0055] The fully impregnated thermoplastic composite strands may be
directly supplied to a molding machine 312 that forms the
composition into the fiber-reinforced composite article. In some
embodiments, the fully impregnated composite strands may be chopped
to pellets. The composite pellets may be mixed with a second
thermoplastic resin to produce composite articles in a molding
process. Exemplary molding machines 312 may include injection
molding machines, among other types of molding machines.
Exemplary Fiber-Reinforced Composite Articles
[0056] FIG. 4 shows an exemplary fiber-reinforced composite vehicle
part 402 formed by the fiber-resin compositions. Vehicle part 402
may be an exterior automobile panel. The vehicle part 402 is one of
many types of articles that can be formed by the present methods
and compositions. Other articles may include appliance parts,
containers, etc. Smaller or intricate parts may use pellets in
order to adequately form the part.
Exemplary Thermoplastic Composite Strand
[0057] A reactive thermoplastic resin containing caprolactam,
sodium caprolactam, and caprolactam blocked isocyanates is melted
in an extruder. The molten resin is then added to a roving of glass
fibers in an impregnation device. The molten resin, being low
viscosity, fully impregnates the roving. The resin, being a
reactive resin, in situ and anionically polymerizes to form
polyamide-6. The polyamide-6 solidifies after the completion of
polymerization. The polyamide-6 and the roving together form a
thermoplastic composite strand. The continuous glass fiber
reinforced polyamide-6 composite strand is chopped into pellets.
The polyamide-6 composite pellets are mixed with a hydrolytically
polymerized polyamide-6 resin to form a mixture. The mixture is
formed into a composite article through a molding process. Some of
the mixture is formed into a composite article using an injection
molding process.
[0058] Having described several embodiments, it will be recognized
by those of skill in the art that various modifications,
alternative constructions, and equivalents may be used without
departing from the spirit of the invention. Additionally, a number
of well-known processes and elements have not been described in
order to avoid unnecessarily obscuring the present invention.
Accordingly, the above description should not be taken as limiting
the scope of the invention.
[0059] In the preceding description, for the purposes of
explanation, numerous details have been set forth in order to
provide an understanding of various embodiments of the present
technology. It will be apparent to one skilled in the art, however,
that certain embodiments may be practiced without some of these
details, or with additional details.
[0060] Having described several embodiments, it will be recognized
by those of skill in the art that various modifications,
alternative constructions, and equivalents may be used without
departing from the spirit of the invention. Additionally, a number
of well-known processes and elements have not been described in
order to avoid unnecessarily obscuring the present invention.
Additionally, details of any specific embodiment may not always be
present in variations of that embodiment or may be added to other
embodiments.
[0061] Where a range of values is provided, it is understood that
each intervening value, to the tenth of the unit of the lower limit
unless the context clearly dictates otherwise, between the upper
and lower limits of that range is also specifically disclosed. Each
smaller range between any stated value or intervening value in a
stated range and any other stated or intervening value in that
stated range is encompassed. The upper and lower limits of these
smaller ranges may independently be included or excluded in the
range, and each range where either, neither, or both limits are
included in the smaller ranges is also encompassed within the
invention, subject to any specifically excluded limit in the stated
range. Where the stated range includes one or both of the limits,
ranges excluding either or both of those included limits are also
included.
[0062] As used herein and in the appended claims, the singular
forms "a", "an", and "the" include plural referents unless the
context clearly dictates otherwise. Thus, for example, reference to
"a method" includes a plurality of such methods and reference to
"the fiber" includes reference to one or more fibers and
equivalents thereof known to those skilled in the art, and so
forth. The invention has now been described in detail for the
purposes of clarity and understanding. However, it will be
appreciated that certain changes and modifications may be practice
within the scope of the appended claim
* * * * *