U.S. patent application number 16/473133 was filed with the patent office on 2019-11-28 for thermoplastic resin fiber with dispersant attached.
This patent application is currently assigned to KURARAY CO., LTD.. The applicant listed for this patent is KURARAY CO., LTD.. Invention is credited to Tomohiro HAYAKAWA, Hiroyuki KAWAI, Toshimichi KUSUNOKI, Tomoki SAKAI.
Application Number | 20190360149 16/473133 |
Document ID | / |
Family ID | 62709579 |
Filed Date | 2019-11-28 |
![](/patent/app/20190360149/US20190360149A1-20191128-C00001.png)
United States Patent
Application |
20190360149 |
Kind Code |
A1 |
SAKAI; Tomoki ; et
al. |
November 28, 2019 |
THERMOPLASTIC RESIN FIBER WITH DISPERSANT ATTACHED
Abstract
To provide a thermoplastic resin fiber to which a dispersant is
attached, which can effectively disperse carbon fibers. A
thermoplastic resin fiber to which a dispersant containing a random
copolymer (A) of glycidyl ether and an alkylene oxide is attached
in an amount of 0.1 to 20% by mass based on a total mass of
thermoplastic resin fibers to which a dispersant is not
attached.
Inventors: |
SAKAI; Tomoki; (Okayama-shi,
JP) ; KAWAI; Hiroyuki; (Okayama-shi, JP) ;
HAYAKAWA; Tomohiro; (Okayama-shi, JP) ; KUSUNOKI;
Toshimichi; (Okayama-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KURARAY CO., LTD. |
Kurashiki-shi |
|
JP |
|
|
Assignee: |
KURARAY CO., LTD.
Kurashiki-shi
JP
|
Family ID: |
62709579 |
Appl. No.: |
16/473133 |
Filed: |
December 26, 2017 |
PCT Filed: |
December 26, 2017 |
PCT NO: |
PCT/JP2017/046774 |
371 Date: |
June 24, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
D21H 17/06 20130101;
C08J 5/04 20130101; D21H 13/10 20130101; D21H 21/08 20130101; D06M
15/568 20130101; D21H 13/50 20130101; D06M 15/53 20130101 |
International
Class: |
D06M 15/53 20060101
D06M015/53; D06M 15/568 20060101 D06M015/568 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 28, 2016 |
JP |
2016-256170 |
Claims
1. A thermoplastic resin fiber to which a dispersant comprising a
random copolymer (A) of glycidyl ether and an alkylene oxide is
attached in an amount of 0.1 to 20% by mass based on a total mass
of thermoplastic resin fibers to which a dispersant is not
attached.
2. The thermoplastic resin fiber according to claim 1, wherein the
random copolymer (A) of glycidyl ether and an alkylene oxide is a
random copolymer of phenyl glycidyl ether and an alkylene
oxide.
3. The thermoplastic resin fiber according to claim 2, wherein the
random copolymer (A) of phenyl glycidyl ether and an alkylene oxide
is a random copolymer of phenyl glycidyl ether and ethylene oxide,
or a random copolymer of phenyl glycidyl ether, ethylene oxide and
propylene oxide.
4. The thermoplastic resin fiber according to claim 1, wherein the
dispersant further comprises a polyether-based polyurethane resin
(B).
5. The thermoplastic resin fiber according to claim 1, wherein the
thermoplastic resin fiber is one or more fibers selected from the
group consisting of polyetherimide fibers, polyamide fibers,
polyester fibers, polyolefin fibers, polyetheretherketone fibers
and polycarbonate fibers.
6. The thermoplastic resin fiber according to claim 1, wherein the
thermoplastic resin fiber has one or more structures selected from
the group consisting of a circular structure, an elliptical
structure, a triangular structure, a cross structure, a core-sheath
structure, a sea-island structure, a multi-pleat structure, a
hollow structure and a side-by-side structure.
7. The thermoplastic resin fiber according to claim 1, wherein the
dispersant is attached in an amount of 0.5 to 10% by mass based on
the total mass of the thermoplastic resin fibers to which a
dispersant is not attached.
8. (canceled)
9. A slurry comprising thermoplastic resin fibers according to
claim 1, carbon fibers and water.
10. The slurry according to claim 9, comprising 40 to 900 parts by
mass of the thermoplastic resin fibers based on 100 parts by mass
of the carbon fibers.
11. A nonwoven fabric obtained by papermaking and drying the slurry
according to claim 9.
12. A nonwoven fabric based on thermoplastic resin fibers according
to claim 1 and carbon fibers, wherein an amount of the dispersant
in the nonwoven fabric is 0.01 to 1.0% by mass based on a total
mass of thermoplastic resin fibers in the nonwoven fabric.
13. The nonwoven fabric according to claim 11, wherein a number of
carbon fiber bundles having a fiber bundle width of 0.1 mm or more
on a surface is 2000 pieces/m.sup.2 or less.
14. A carbon fiber-reinforced composite molded body based on the
nonwoven fabric according to claim 11.
15. The carbon fiber-reinforced composite molded body according to
claim 14, wherein a number of carbon fiber bundles having a fiber
bundle width of 0.1 mm or more on a surface is 2000 pieces/m.sup.2
or less.
16. The carbon fiber-reinforced composite molded body according to
claim 14, wherein the thermoplastic resin fiber acts as a matrix
resin.
17. A method for manufacturing a carbon fiber-reinforced composite
molded body, the method comprising: papermaking and drying the
slurry according to claim 9, and heat press molding the obtained
nonwoven fabric.
Description
TECHNICAL FIELD
[0001] The present invention relates to a thermoplastic resin fiber
to which a dispersant is attached. More particularly, the present
invention relates to a thermoplastic resin fiber to which a
dispersant is attached, that is capable of effectively dispersing
carbon fibers. The present invention also relates to a slurry
containing the thermoplastic resin fibers, carbon fibers and water,
a nonwoven fabric based on the thermoplastic resin fibers and
carbon fibers, a carbon fiber-reinforced composite molded body
based on the nonwoven fabric, and a method for manufacturing the
carbon fiber-reinforced composite molded body.
BACKGROUND ART
[0002] Composite molding materials obtained by impregnating a
nonwoven fabric composed of reinforcing fibers such as carbon
fibers with a matrix resin are known and used for automobile or
aircraft parts and the like.
[0003] Such composite molding materials can be manufactured, for
example, by laminating a wet nonwoven fabric of carbon fibers and a
thermoplastic resin film, and hot press-molding the obtained
laminate to melt the thermoplastic resin film and impregnate the
carbon fiber nonwoven fabric with the melt.
[0004] As another manufacturing method, for example, a method is
also known in which carbon fibers and thermoplastic resin fibers
are mixed by a papermaking method to form a wet nonwoven fabric,
and the thermoplastic resin fibers in the nonwoven fabric are
melted by hot-pressing the nonwoven fabric to obtain a molded body.
This manufacturing method is preferable from the viewpoint of
easily obtaining high mechanical properties of the molded body due
to the fact that carbon fibers in the molded body are well
dispersed in a matrix resin (molten thermoplastic resin fibers),
and from the viewpoint of simplicity of the manufacturing
method.
[0005] For example, Patent Document 1 discloses a substrate for a
fiber-reinforced plastic molded body comprising reinforcing fibers,
a matrix resin containing a thermoplastic resin, and a binder
component, and a method for manufacturing the substrate for a
fiber-reinforced plastic molded body including a step of
papermaking by a wet nonwoven fabric method, and discloses that, in
the wet nonwoven fabric method, a dispersant in the form of an
aqueous solution may be added to water to which carbon fibers are
added, in order to improve dispersibility of the carbon fibers as
reinforcing fibers.
[0006] Further, Patent Document 2 discloses a dispersant for
hydrophobic fiber papermaking which comprises (A) a monofatty acid
esterified product of ethylene oxide adduct of trimethylolpropane
and (B) an anionic surfactant in a specific ratio, a synthetic
fiber for papermaking obtained by attaching the dispersant for
papermaking to a hydrophobic fiber, and a nonwoven fabric obtained
by wet papermaking of the synthetic fibers.
PRIOR ART DOCUMENTS
Patent Documents
[0007] Patent Document 1: JP-A-2016-20421 [0008] Patent Document 2:
JP-A-2006-77379
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0009] When preparing a wet nonwoven fabric from carbon fibers
using a papermaking method, it is important to well disperse the
carbon fibers in an aqueous dispersion medium. When this dispersion
is poor, for example, carbon fibers may be scattered in the form of
a block of "bundles" in the molded body, which may be a defect and
cause problems such as deterioration in mechanical properties of
the molded body.
[0010] In Patent Document 1, it has been found by studies of the
present inventors that problems may occur, such as dispersing
carbon fibers requires time due to the fact that entering a
dispersant between bundle-like carbon fibers (CF) requires time,
and bending strength, impact resistance or the like may decrease
due to the fact that a matrix resin cannot enter between
bundle-like CFs generating because of poor dispersion when it is
compounded as CFRP (carbon fiber-reinforced plastic).
[0011] In addition, Patent Document 2 discloses that, in a method
for manufacturing a nonwoven fabric used for filtration bags such
as black tea bags, wet tissues or disposable diapers by a wet
papermaking method, a dispersant for hydrophobic fiber papermaking
is attached to hydrophobic fibers composed of resins such as
polyolefin resins or polyester resins in advance to obtain a
synthetic fiber for papermaking, and a paper of the obtained
synthetic fibers is produced. However, Patent Document 2 does not
show a solution for improving the dispersibility of reinforcing
fibers such as carbon fibers.
[0012] Therefore, an object of the present invention is to provide
a thermoplastic resin fiber to which a dispersant is attached,
which can effectively disperse carbon fibers.
Solutions to the Problems
[0013] The present inventors have repeated detailed studies on
thermoplastic resin fiber to which a dispersant is attached, in
order to solve the above object, thus completing the present
invention.
[0014] That is, the present invention includes the following
preferred aspects.
[1] A thermoplastic resin fiber to which a dispersant containing a
random copolymer (A) of glycidyl ether and an alkylene oxide is
attached in an amount of 0.1 to 20% by mass based on a total mass
of thermoplastic resin fibers to which a dispersant is not
attached. [2] The thermoplastic resin fiber according to the above
[1], wherein the random copolymer (A) of glycidyl ether and an
alkylene oxide is a random copolymer of phenyl glycidyl ether and
an alkylene oxide. [3] The thermoplastic resin fiber according to
the above [2], wherein the random copolymer (A) of phenyl glycidyl
ether and an alkylene oxide is a random copolymer of phenyl
glycidyl ether and ethylene oxide, or a random copolymer of phenyl
glycidyl ether, ethylene oxide and propylene oxide. [4] The
thermoplastic resin fiber according to any one of the above [1] to
[3], wherein the dispersant further contains a polyether-based
polyurethane resin (B). [5] The thermoplastic resin fiber according
to any one of the above [1] to [4], wherein the thermoplastic resin
fiber is one or more fibers selected from the group consisting of
polyetherimide fibers, polyamide fibers, polyester fibers,
polyolefin fibers, polyetheretherketone fibers and polycarbonate
fibers. [6] The thermoplastic resin fiber according to any one of
the above [1] to [5], wherein the thermoplastic resin fiber has one
or more structures selected from the group consisting of a circular
structure, an elliptical structure, a triangular structure, a cross
structure, a core-sheath structure, a sea-island structure, a
multi-pleat structure, a hollow structure and a side-by-side
structure. [7] The thermoplastic resin fiber according to any one
of the above [1] to [6], wherein the dispersant is attached in an
amount of 0.5 to 10% by mass based on the total mass of the
thermoplastic resin fibers to which a dispersant is not attached.
[8] Use of the thermoplastic resin fiber according to any one of
the above [1] to [7] as a dispersant for carbon fibers in a slurry
containing the thermoplastic resin fibers, the carbon fibers and
water. [9] A slurry comprising the thermoplastic resin fibers
according to any one of the above [1] to [7], carbon fibers and
water. [10] The slurry according to the above [9], comprising 40 to
900 parts by mass of the thermoplastic resin fibers based on 100
parts by mass of the carbon fibers. [11] A nonwoven fabric obtained
by papermaking and drying the slurry according to the above [9] or
[10]. [12] A nonwoven fabric based on the thermoplastic resin
fibers according to any one of the above [1] to [7] and carbon
fibers, wherein an amount of the dispersant in the nonwoven fabric
is 0.01 to 1.0% by mass based on a total mass of thermoplastic
resin fibers in the nonwoven fabric. [13] The nonwoven fabric
according to the above [11] or [12], wherein a number of carbon
fiber bundles having a fiber bundle width of 0.1 mm or more on a
surface is 2000 pieces/m.sup.2 or less. [14] A carbon
fiber-reinforced composite molded body based on the nonwoven fabric
according to any one of the above [11] to [13]. [15] The carbon
fiber-reinforced composite molded body according to the above [14],
wherein a number of carbon fiber bundles having a fiber bundle
width of 0.1 mm or more on a surface is 2000 pieces/m.sup.2 or
less. [16] The carbon fiber-reinforced composite molded body
according to the above [14] or [15], wherein the thermoplastic
resin fiber acts as a matrix resin. [17] A method for manufacturing
a carbon fiber-reinforced composite molded body, the method
comprising: [0015] papermaking and drying the slurry according to
the above [9] or [10], and [0016] heat press molding the obtained
nonwoven fabric.
Effects of the Invention
[0017] Carbon fibers can be effectively dispersed by using the
thermoplastic resin fiber of the present invention to which a
dispersant is attached.
EMBODIMENTS OF THE INVENTION
[0018] The thermoplastic resin fiber of the present invention is a
fiber to which a dispersant containing a random copolymer (A) of
glycidyl ether and an alkylene oxide is attached.
<Dispersant>
[0019] The dispersant attached to the fiber of the present
invention contains a random copolymer (A) of glycidyl ether and an
alkylene oxide. The random copolymer (A) is preferably a random
copolymer of phenyl glycidyl ether and an alkylene oxide, and is
more preferably a random copolymer of phenyl glycidyl ether and
ethylene oxide or a random copolymer of phenyl glycidyl ether,
ethylene oxide and propylene oxide.
[0020] Carbon fibers can be effectively dispersed by attaching the
above dispersant to the thermoplastic resin fiber. Therefore, in a
slurry containing the thermoplastic resin fibers of the present
invention, carbon fibers and water, the carbon fibers are well
dispersed in a short time and with weak agitation. That is, the
thermoplastic resin fiber of the present invention acts as a
dispersant for carbon fibers in the slurry. In addition, a carbon
fiber-reinforced composite molded body manufactured from a nonwoven
fabric based on the thermoplastic resin fibers of the present
invention and carbon fibers has improved mechanical properties due
to the well dispersed carbon fibers. In the carbon fiber-reinforced
composite molded body, the thermoplastic resin fiber of the present
invention acts as a matrix resin. That is, the thermoplastic resin
fiber of the present invention is contained as a matrix resin
precursor in the slurry and the nonwoven fabric. Here, since the
matrix resin (or matrix) means a base material which bonds
reinforcing fibers in a composite molded body, a fact that a
thermoplastic resin fiber acts as a matrix resin in a carbon
fiber-reinforced composite molded body means that the thermoplastic
resin fiber forms at least a part of the matrix in the carbon
fiber-reinforced composite molded body.
<Random Copolymer (A)>
[0021] The random copolymer (A) is based on glycidyl ether (GE) and
an alkylene oxide (AO), and has a structural unit represented by
the following chemical formula (1):
[Chemical Formula 1]
-(AO).sub.m-(GE).sub.1- (1)
wherein 1 and m are integers of 1 or more; and GE and AO are
arranged with a random order.
[0022] The glycidyl ether (GE) is preferably selected from the
group consisting of alkyl glycidyl ethers having 1 to 18 alkyl
carbon atoms, allyl glycidyl ether, phenyl glycidyl ether and
naphthyl glycidyl ether and is more preferably phenyl glycidyl
ether, from the viewpoint of easily dispersing carbon fibers.
[0023] The alkylene oxide (AO) may be one or more alkylene oxides,
and for example, when the alkylene oxide (AO) is two alkylene
oxides (AO1) and (AO2), the random copolymer (A) has a structural
unit represented by the following chemical formula (2):
[Chemical Formula 2]
-(AO1).sub.m1-(AO2).sub.m2-(GE).sub.1- (2)
wherein 1, m1 and m2 are integers of 1 or more; and GE, AO1 and AO2
are arranged with a random order.
[0024] The alkylene oxide (AO) may be linear or branched, and is
preferably a linear or branched alkylene oxide having 1 to 4 carbon
atoms, more preferably a linear or branched alkylene oxide having 2
to 3 carbon atoms, and particularly preferably ethylene oxide, or
ethylene oxide and propylene oxide, from the viewpoints of
reactivity of the alkylene oxide (ease of synthesis of the random
copolymer represented by the chemical formula (1)) and ease of
availability of the alkylene oxide.
[0025] In one aspect, m1 or m2 is preferably an integer of 60 or
more, and more preferably an integer of 150 or more.
[0026] Copolymerization ratio AO:GE is preferably 70:30 to
99.5:0.5, more preferably 80:20 to 99.5:0.5, and particularly
preferably 80:20 to 99:1.
[0027] Here, the copolymerization ratio AO:GE is a mass ratio of
alkylene oxide to glycidyl ether in the random copolymer (A), which
can be measured by use of, for example, nuclear magnetic resonance
spectrum (.sup.1H-NMR) under the following measurement
conditions.
<Measurement Conditions>
[0028] Equipment: Product Name "JNM-AL400" (manufactured by JEOL
Ltd.) [0029] Observed Nucleus: 1 H [0030] Observation Range:
7992.01 Hz [0031] Data Point Number: 32768 [0032] Pulse Width: 5.80
.mu.sec [0033] Wait Time: 50.00 .mu.sec [0034] Integration
Frequencies: 512 [0035] Measurement Temperature: 25.degree. C.
[0036] Solvent for Measurement: Deuterated chloroform [0037] Sample
Concentration: 0.01 g/mL
[0038] When the copolymerization ratio in the random copolymer (A)
is within the above ranges, carbon fibers are easily dispersed.
[0039] A random copolymer of phenyl glycidyl ether (PGE) and
ethylene oxide (EO) or a random copolymer of phenyl glycidyl ether,
ethylene oxide and propylene oxide (PO), which is a more preferable
random copolymer (A), has a structural unit represented by the
following chemical formula (3):
##STR00001##
wherein 1 and n are integers of 1 or more; m is an integer of 0 or
more; and PGE, EO and PO are arranged with a random order.
[0040] 1 is an integer of 1 or more; and m is an integer of 0 or
more. n is an integer of 1 or more, preferably 60 or more, and
particularly preferably 150 or more.
[0041] Copolymerization ratio EO:PGE is preferably 70:30 to
99.5:0.5, more preferably 80:20 to 99.5:0.5, and particularly
preferably 80:20 to 99:1. In addition, copolymerization ratio of PO
is preferably 30 or less, more preferably 20 or less, and
particularly preferably 10 or less.
[0042] Here, the copolymerization ratio EO:PGE is a mass ratio of
ethylene oxide to phenyl glycidyl ether in the random copolymer
(A), and the copolymerization ratio of PO is a mass ratio of
propylene oxide in the random copolymer (A), which can be measured
by use of, for example, nuclear magnetic resonance spectrum
(.sup.1H-NMR) under the measurement conditions as described
previously.
[0043] When the copolymerization ratio in the random copolymer (A)
is within the above ranges, carbon fibers are easily dispersed.
[0044] The random copolymer (A) preferably has a larger
weight-average molecular weight M.sub.w from the viewpoint of
dispersibility of the carbon fibers, for example, preferably 4,000
to 10,000,000, more preferably 4,000 to 1,000,000, and particularly
preferably 10,000 to 200,000.
[0045] The weight-average molecular weight M.sub.w can be measured
by use of, for example, gel permeation chromatography (GPC) under
the following measurement conditions.
<Measurement Conditions>
[0046] Apparatus: Product Name "LC-10AD" (manufactured by Shimadzu
Corporation) [0047] Detector: Differential Refractive Index
Detector (RID) [0048] Column: Product Name "SHODEX KF-804"
(manufactured by SHOWA DENKO K.K.) [0049] Measurement Temperature:
30.degree. C. [0050] Eluent: THF [0051] Flow Rate: 1.0 mL/min
[0052] Sample Concentration: 0.2% by mass (THF) [0053] Sample
Injection Volume: 100 .mu.L [0054] Conversion Standard:
Polyethylene oxide
[0055] When the weight-average molecular weight of the random
copolymer (A) is within the above ranges, carbon fibers are easily
dispersed.
[0056] The molecular weight distribution (weight-average molecular
weight M.sub.w/number-average molecular weight M.sub.n) of the
random copolymer (A) is not particularly limited, but is preferably
5 or less, more preferably 3 or less, and particularly preferably 2
or less. In the same manner as the measurement of the
weight-average molecular weight M.sub.w described above, the
number-average molecular weight M.sub.n can be measured by use of,
for example, gel permeation chromatography (GPC). When the
molecular weight distribution of the random copolymer (A) is within
the above ranges, for example in a case where the random copolymer
(A) is used as an aqueous solution, the aqueous solution easily has
a viscosity that is easy to handle and carbon fibers are easily
dispersed.
[0057] The degree of randomness of the random copolymer (A) is not
particularly limited.
<Production of Random Copolymer (A)>
[0058] The random copolymer (A) can be produced by copolymerizing
glycidyl ether and an alkylene oxide, preferably in the
above-described copolymerization ratio.
[0059] Copolymerization of glycidyl ether and an alkylene oxide can
be carried out by use of a publicly known method such as a solution
polymerization method or a solvent slurry polymerization method.
For example, it can be carried out by adding predetermined amounts
of glycidyl ether and an alkylene oxide to a solution obtained by
adding an appropriate catalyst to an appropriate solvent at room
temperature under an inert gas atmosphere. A general catalyst used
for producing a random copolymer from glycidyl ether and an
alkylene oxide can be used as an appropriate catalyst, and examples
thereof include organoaluminum catalysts, organozinc catalysts,
organotin phosphate condensate catalysts, alkali metal hydroxide
catalysts such as potassium hydroxide and sodium methoxide,
alkoxides of alkali metals, and catalyst compositions obtained by
combining them. Among them, it is preferred to use a catalyst
composition containing an organoaluminum catalyst, and an alkoxide
of an alkali metal or an alkali metal hydroxide, from the
viewpoints of catalytic activity level, ease of adjusting
polymerization degree, and ease of handling. A general solvent used
for producing a random copolymer from glycidyl ether and an
alkylene oxide can be used as an appropriate solvent, and examples
thereof include ethers, aliphatic hydrocarbons, aromatic
hydrocarbons, halogen solvents, ketones and the like, and mixtures
of two or more of these solvents. Among them, it is preferred to
use n-butane, isobutane, n-pentane, cyclopentane, industrial
hexane, n-hexane, isohexane, cyclohexane, n-heptane, n-octane or
isooctane from the viewpoint that the random copolymer produced is
easily dried and can be handled as powders without any aggregation
because it is not dissolved in a solvent. In addition, it is
preferred to use toluene or xylene from the viewpoint that the
random copolymer produced can be handled as a solution because it
is dissolved in the solvent. The reaction temperature
(copolymerization temperature) at which the copolymerization is
carried out is not particularly limited as long as it is a general
temperature, and may be, for example, 150.degree. C. or less, and
preferably 50.degree. C. or less. After the copolymerization
reaction, the reaction solution is filtered or concentrated, and
the residue is dried by a general method (for example, by use of a
vacuum dryer), so that a random copolymer (A) of glycidyl ether and
an alkylene oxide can be obtained as a viscous liquid or a
solid.
[0060] A commercially available phenylglycidyl ether-ethylene
oxide-propylene oxide random copolymer can also be used as the
random copolymer (A), and examples thereof can include ALKOX
(registered trade name) CP-B1, CP-B2 and the like manufactured by
Meisei Chemical Works, Ltd.
[0061] The dispersant attached to the thermoplastic resin fiber of
the present invention preferably further contains a polyether-based
polyurethane resin (B) in addition to the random copolymer (A).
<Polyether-Based Polyurethane Resin (B)>
[0062] A polyether-based polyurethane resin (B) is preferably based
on a bifunctional polyol which is polyethylene glycol and/or an
ethylene oxide-propylene oxide random copolymer, and hexamethylene
diisocyanate.
[0063] The polymerization ratio (bifunctional polyol:hexamethylene
diisocyanate) is preferably 99.5:0.5 to 60:40, more preferably
99.5:0.5 to 80:20, and particularly preferably 99:1 to 95:5. Here,
the polymerization ratio (bifunctional polyol:hexamethylene
diisocyanate) is a mass ratio of the bifunctional polyol to the
hexamethylene diisocyanate in the polyether-based polyurethane
resin (B), which can be measured by use of, for example, nuclear
magnetic resonance spectrum (.sup.1H-NMR) as described previously.
When the polymerization ratio in the polyether-based polyurethane
resin (B) is within the above ranges, water solubility of the
polyether-based polyurethane resin (B) is improved, and wettability
to the carbon fibers is improved, so that carbon fibers can be
easily dispersed.
[0064] The polyether-based polyurethane resin (B) has a
weight-average molecular weight M.sub.w of preferably 5,000 to
1,000,000, more preferably 10,000 to 1,000,000, and particularly
preferably 20,000 to 100,000. The weight-average molecular weight
M.sub.w can be measured by use of, for example, gel permeation
chromatography (GPC) as described previously. When the
weight-average molecular weight of the polyether-based polyurethane
resin (B) is within the above ranges, carbon fibers can be easily
dispersed.
[0065] The molecular weight distribution (M.sub.w/M.sub.n) of the
polyether-based polyurethane resin (B) is not particularly
limited.
<Production of Polyether-Based Polyurethane Resin (B)>
[0066] The polyether-based polyurethane resin (B) can be produced
by polymerizing a bifunctional polyol which is polyethylene glycol
and/or an ethylene oxide-propylene oxide random copolymer with
hexamethylene diisocyanate preferably in the above-described
polymerization ratio.
<Polyethylene Glycol>
[0067] Polyethylene glycol which is one of the bifunctional polyols
for producing the polyether-based polyurethane resin (B) preferably
has a weight-average molecular weight M.sub.w of 200 to 300,000,
more preferably 400 to 200,000, and particularly preferably 400 to
20,000. The weight-average molecular weight M.sub.w can be measured
by use of, for example, gel permeation chromatography (GPC) as
described previously. When the weight-average molecular weight of
polyethylene glycol is within the above ranges, water solubility of
the polyether-based polyurethane resin (B) is improved, and
wettability to the carbon fibers is improved, so that carbon fibers
can be easily dispersed.
[0068] The molecular weight distribution (M.sub.w/M.sub.n) of the
polyethylene glycol is not particularly limited.
[0069] Such polyethylene glycols are commercially available, for
example, under the trade name of "PEG series" from Sanyo Chemical
Industries, Ltd. or under the trade name of "ALKOX Series" from
Meisei Chemical Works, Ltd.
<Ethylene Oxide-Propylene Oxide Random Copolymer>
[0070] An ethylene oxide-propylene oxide random copolymer which is
one of the bifunctional polyols for producing the polyether-based
polyurethane resin (B) is based on ethylene oxide (EO) and
propylene oxide (PO).
[0071] Copolymerization ratio EO:PO is preferably 90:10 to 10:90.
Here, the copolymerization ratio EO:PO is a mass ratio of ethylene
oxide to propylene oxide in the ethylene oxide-propylene oxide
random copolymer, which can be measured by use of, for example,
nuclear magnetic resonance spectrum (.sup.1H-NMR) as described
previously. When the copolymerization ratio in the ethylene
oxide-propylene oxide random copolymer is within the above range,
carbon fibers are easily dispersed.
[0072] The ethylene oxide-propylene oxide random copolymer
preferably has a weight-average molecular weight M.sub.w of 200 to
150,000, more preferably 400 to 110,000, and particularly
preferably 400 to 20,000. The weight-average molecular weight
M.sub.w can be measured by use of, for example, gel permeation
chromatography (GPC) as described previously. When the
weight-average molecular weight of the ethylene oxide-propylene
oxide random copolymer is within the above ranges, carbon fibers
are easily dispersed.
[0073] The molecular weight distribution (Man) of the ethylene
oxide-propylene oxide random copolymer is not particularly
limited.
[0074] The degree of randomness of the ethylene oxide-propylene
oxide random copolymer is not particularly limited.
[0075] The ethylene oxide-propylene oxide random copolymer can be
produced by copolymerizing ethylene oxide and propylene oxide
preferably in the above-described copolymerization ratio. The
copolymerization of ethylene oxide and propylene oxide can be
carried out by use of a publicly known method disclosed in
JP-A-117-243178, JP-A-2011-32398 or the like. For example, it can
be carried out by addition-polymerizing ethylene oxide and
propylene oxide to a diol compound. Ethylene glycol, propylene
glycol, butane diol, hexamethylene glycol, hexylene glycol and the
like can be used as the diol compound. A general catalyst used for
producing a random copolymer from ethylene oxide and propylene
oxide can be used as an appropriate catalyst, and examples thereof
include hydroxides of alkali metals, alcoholates of alkali metals,
and the like. Among them, it is preferred to use sodium hydroxide
and potassium hydroxide from the viewpoint of ease of handling. The
amount of the catalyst used is usually 0.01 to 1% by mass,
preferably 0.05 to 0.5% by mass, and more preferably 0.1 to 0.3% by
mass, based on the ethylene oxide-propylene oxide random copolymer.
A general solvent used for producing a random copolymer from
ethylene oxide and propylene oxide can be used as an appropriate
solvent, and examples thereof include BTX such as toluene and
xylene. However, solvent-free synthesis is preferred from the
viewpoint of production cost. The reaction temperature
(copolymerization temperature) at which the copolymerization is
carried out is not particularly limited as long as it is a general
temperature, and may be, for example, 80 to 200.degree. C. After
the copolymerization reaction, unreacted monomers and a solvent are
removed, and, if necessary, the catalyst is removed by a method
such as adsorptive filtration, so that an ethylene oxide-propylene
oxide random copolymer can be obtained as a liquid or a solid.
[0076] A commercially available ethylene oxide-propylene oxide
random copolymer can also be used as the ethylene oxide-propylene
oxide random copolymer. Examples thereof can include "New Pole
(registered trade name) 75H-90000" manufactured by Sanyo Chemical
Industries, Ltd., "Brownon P-13075R" manufactured by AOKI OIL
INDUSTRIAL Co., Ltd., and the like.
[0077] The polymerization of a bifunctional polyol and
hexamethylene diisocyanate for producing a polyether-based
polyurethane resin (B) can be carried out by use of a publicly
known method disclosed in JP-A-H10-147706, JP-A-2001-354742,
JP-A-H7-243178 or the like. For example, the polymerization can be
carried by heating and dehydrating a bifunctional polyol under an
inert gas atmosphere, and dissolving it in an appropriate solvent
after cooling, followed by adding hexamethylene diisocyanate and an
appropriate catalyst thereto to polymerize the mixture. A general
catalyst used for producing a polyether-based polyurethane resin
can be used as an appropriate catalyst. Examples thereof include
amine-based catalysts (triethylamine, dimethylcyclohexylamine,
tetramethylethylenediamine, pentamethyldiethylenetriamine,
triethylenediamine, N-methylmorpholine and the like), tin-based
catalysts (dibutyltin dilaurate, trimethyltin laurate, trimethyltin
hydroxide, dimethyltin dilaurate and the like), lead-based
catalysts (lead oleate, lead 2-ethylhexanoate, lead naphthenate,
lead octylate and the like), and the like. Among them, it is
preferred to use dibutyltin dilaurate from the viewpoint of high
catalytic activity. The amount of the catalyst used is usually 0.01
to 5 parts by mass, preferably 0.05 to 3 parts by mass, and more
preferably 0.1 to 1 part by mass, based on 100 parts by mass of the
polyether-based polyurethane resin. A general solvent used for
producing a polyether-based polyurethane resin can be used as an
appropriate solvent, and examples thereof include acetone, toluene,
xylene, ethyl acetate, methyl ethyl ketone, methyl isobutyl ketone,
and the like. Among them, it is preferred to use acetone from the
viewpoint of ease of removing the solvent. The reaction temperature
(polymerization temperature) at which the polymerization is carried
out is not particularly limited as long as it is a general
temperature, and may be, for example, 20 to 150.degree. C., and
preferably 20 to 80.degree. C. After the polymerization reaction,
the solvent is removed by a general method (e.g., distilled off),
and replaced by water, so that an aqueous solution of the
polyether-based polyurethane resin (B) can be obtained.
[0078] A commercially available polyether-based polyurethane resin
can also be used as the polyether-based polyurethane resin (B), and
examples thereof can include Pulset HA manufactured by Meisei
Chemical Works, Ltd., and the like.
<Thermoplastic Resin Fibers>
[0079] The thermoplastic resin fiber in the present invention is
not particularly limited as long as it is a thermoplastic resin
fiber generally used as a thermoplastic resin fiber which is a
matrix resin precursor of a carbon fiber-reinforced composite
molded body. Such thermoplastic resin fibers are preferably one or
more fibers selected from the group consisting of polyetherimide
fibers, polyamide fibers, polyester fibers, polyolefin fibers,
polyetheretherketone fibers and polycarbonate fibers, more
preferably one or more fibers selected from the group consisting of
polyetherimide fibers, polyamide fibers, polypropylene fibers and
polyetheretherketone fibers from the viewpoints of adhesion to
carbon fibers and a melting point suitable for molding, and
particularly preferably one or more fibers selected from the group
consisting of polyetherimide fibers, polyamide fibers and
polypropylene fibers from the viewpoint of physical properties such
as tensile strength.
[0080] The structure of the thermoplastic resin fiber in the
present invention is not particularly limited as long as it is a
normal structure of the thermoplastic resin fiber which is a matrix
resin precursor of the carbon fiber-reinforced composite molded
body. Such structure is preferably one or more structures selected
from the group consisting of a circular structure, an elliptical
structure, a triangular structure, a cross structure, a core-sheath
structure, a sea-island structure, a multi-pleat structure, a
hollow structure and a side-by-side structure.
[0081] The thermoplastic resin fiber in the present invention may
contain an antioxidant, an antistatic agent, a radical inhibitor, a
matting agent, an ultraviolet absorber, a flame retardant, various
inorganic substances and the like as long as the effect of the
present invention is not impaired. Specific examples of such
inorganic substances include carbon materials such as carbon
nanotubes, fullerenes, carbon black, graphite and silicon carbide;
silicate materials such as talc, warastenite, zeolite, sericite,
mica, kaolin, clay, pyrophyllite, silica, bentonite and alumina
silicate; metal oxides such as ceramic beads, silicon oxide,
magnesium oxide, alumina, zirconium oxide, titanium oxide and iron
oxide; carbonates such as calcium carbonate, magnesium carbonate
and dolomite; sulfates such as calcium sulfate and barium sulfate;
hydroxides such as calcium hydroxide, magnesium hydroxide and
aluminum hydroxide; glasses such as glass beads, glass flakes and
glass powder; ceramic beads; boron nitride, and the like.
[0082] A single yarn fineness of the thermoplastic resin fiber in
the present invention is not particularly limited, and is selected,
for example, from the range of 0.1 to 50 dtex. In order to obtain a
carbon fiber-reinforced composite molded body having excellent
mechanical properties, it is desirable to uniformly disperse carbon
fibers in a nonwoven fabric to be a precursor by thermoplastic
resin fibers, so that the single yarn fineness is preferably 0.1 to
40 dtex, more preferably 0.1 to 15 dtex, more preferably 0.1 to 10
dtex, more preferably 0.2 to 9 dtex, and particularly preferably
0.3 to 8 dtex (for example, 0.3 to 5 dtex). When the single yarn
fineness is within the above ranges, carbon fibers are easily
dispersed uniformly by thermoplastic resin fibers, and good
freeness is easily obtained in a process in a case where a nonwoven
fabric is produced by a wet papermaking method.
[0083] The average fiber length of monofilaments of the
thermoplastic resin fiber in the present invention is usually 0.5
to 60 mm, preferably 1 to 55 mm, and more preferably 3 to 50 mm.
When the average fiber length is within the above ranges, the
fibers are less easily to fall off during the process of
manufacturing the nonwoven fabric, good freeness is easily obtained
in a process in a case where a nonwoven fabric is produced by wet
papermaking, and carbon fibers are easily dispersed uniformly by
thermoplastic resin fibers.
<Method for Manufacturing Thermoplastic Resin Fiber>
[0084] The method for manufacturing a thermoplastic resin fiber in
the present invention is not particularly limited as long as fiber
shape can be obtained, and can be carried out using a publicly
known melt spinning apparatus. That is, a thermoplastic resin fiber
can be manufactured by melt-kneading at least a pellet and a powder
of a thermoplastic polymer by a melt extruder, introducing the
molten polymer into a spinning cylinder, weighing it by a gear
pump, and winding yarn discharged from a spinning nozzle. The
take-up speed at that time is not particularly limited, but it is
preferable to take it out in the range of 500 m/min to 4000 m/min
from the viewpoint of reducing occurrence of molecular orientation
on the spinning wire.
<Method for Attaching Dispersant to Thermoplastic Resin
Fiber>
[0085] A method for attaching a dispersant to a thermoplastic resin
fiber is not particularly limited.
[0086] For example, a dispersant can be attached to a thermoplastic
resin fiber by (i) a method of attaching an aqueous solution of a
random copolymer (A) or an aqueous solution of a random copolymer
(A) and a polyether-based polyurethane resin (B) to chopped fibers
of thermoplastic resin fibers cut to an appropriate length, by a
publicly known method such as an immersion method and a spraying
method, and drying it, (ii) a method of attaching an aqueous
solution of a random copolymer (A) and an aqueous solution of a
polyether-based polyurethane resin (B) to chopped fibers of
thermoplastic resin fibers cut to an appropriate length,
sequentially in any order, by a publicly known method such as an
immersion method and a spraying method, and drying it, (iii) a
method of attaching an aqueous solution of a random copolymer (A)
or an aqueous solution of a random copolymer (A) and a
polyether-based polyurethane resin (B) to thermoplastic resin
fibers in any step such as spinning and drawing, by a publicly
known method such as an oil feed roller method, an immersion method
and a spraying method, and drying it, (iv) a method of attaching an
aqueous solution of a random copolymer (A) and an aqueous solution
of a polyether-based polyurethane resin (B) to thermoplastic resin
fibers in any step such as spinning and drawing, sequentially in
any order, by a publicly known method such as an oil feed roller
method, an immersion method and a spraying method, and drying it,
or the like. The thermoplastic resin fiber to which a dispersant is
attached by the above method (iii) or (iv) may be cut to an
appropriate length.
[0087] The concentration of the aqueous solution is usually 0.1 to
5% by mass, and preferably 0.5 to 3% by mass from the viewpoint of
easily securing a predetermined adhesion amount.
[0088] In the thermoplastic resin fibers of the present invention,
a dispersant is attached in an amount of preferably 0.1 to 20% by
mass, more preferably 0.2 to 15% by mass, still further preferably
0.5 to 10% by mass, and particularly preferably 1 to 7% by mass,
based on the total mass of the thermoplastic resin fibers to which
a dispersant is not attached. The adhesion amount of a dispersant
can be measured, for example, using a Soxhlet extraction method, as
described in the following examples. It is easy to disperse carbon
fibers when the adhesion amount of a dispersant is within the above
ranges.
<Slurry>
[0089] The present invention also relates to a slurry containing
the thermoplastic resin fibers of the present invention, carbon
fibers and water.
<Carbon Fibers>
[0090] The carbon fibers are not particularly limited, and any of
the known carbon fibers can be used. Examples thereof include
polyacrylonitrile-based (PAN-based) carbon fibers, rayon-based
carbon fibers, pitch-based carbon fibers, and the like. The carbon
fibers may be each used alone or in mixture of two or more kinds
thereof. It is preferred to use PAN-based carbon fibers from the
viewpoints of inexpensive cost and good mechanical properties. Such
carbon fibers are available as commercial products.
[0091] The carbon fibers preferably have a diameter of 3 to 15
.mu.m, and more preferably 5 to 10 .mu.m.
[0092] Carbon fibers which are recycled from carbon
fiber-reinforced plastics (CFRP) or used carbon fiber nonwoven
fabrics may be used as the carbon fibers. These carbon fibers may
be also each used alone or in mixture of two or more kinds thereof.
Since recycled carbon fibers are relatively inexpensive, they are
preferred from a cost perspective. The method for recycling carbon
fibers is not particularly limited, and examples thereof include a
method of removing a resin part from the CFRP by combustion, a
method of removing a resin part by dissolving or decomposing it
with a solvent, and the like. In the recycling of carbon fibers, it
is difficult to obtain staples having a uniform fiber length, and
very short fibers are mixed therein. In the present invention, very
short fibers may be mixed in recycled carbon fibers in this manner
to such an extent that the effect of the present invention is not
impaired.
[0093] The carbon fibers usually have a length of 5 to 100 mm. In
the present invention, the carbon fibers may be cut so that they
have a length of for example 12.5 mm or more, particular 10.0 mm to
100.0 mm, and furthermore 12.5 mm to 50.0 mm, and then can be
used.
[0094] General treatment for modifying a surface state of carbon
fibers may be either performed or not performed on the carbon
fibers. Examples of such a treatment include application of an oil
agent composition, introduction of a hydrophilic functional group
by oxidation treatment, removal of an irregular surface fragile
layer by application of high voltage, and the like. From the
viewpoint that the thermoplastic resin fiber of the present
invention easily acts as a dispersant for carbon fibers,
non-surface treated carbon fibers are preferred.
[0095] The slurry of the present invention can be manufactured, for
example, by putting the thermoplastic resin fibers of the present
invention, carbon fibers and water into a general mixer or the
like, and stirring (disintegrating) them. The order of putting the
thermoplastic resin fibers of the present invention, carbon fibers
and water is not particularly limited. Examples of the mixer and
the like can include various disintegrators (pulpers), various
beaters such as Niagara beaters, various refiners such as single
disc refiners and double disc refiners, various mixers, and the
like.
[0096] Not only usual tap water but also water such as distilled
water and purified water can be used as the water of an aqueous
dispersion medium. In addition, the aqueous dispersion medium may
contain an aromatic hydrocarbon-based solvent, a hydrocarbon-based
solvent, a halogenated hydrocarbon-based solvent, an ether-based
solvent, a ketone-based solvent, an ester-based solvent, a glycol
ether-based solvent, an acetate-based solvent, a dialkyl
ether-based solvent, an alcohol-based solvent, a glycol-based
solvent, a nitrile-based solvent, a carbonate-based solvent, or the
like. The above solvents may be contained alone or in combination
of two or more thereof.
[0097] The slurry of the present invention contains preferably 40
to 900 parts by mass, more preferably 60 to 500 parts by mass, and
particularly preferably 80 to 300 parts by mass of the
thermoplastic resin fibers of the present invention, based on 100
parts by mass of carbon fibers. When the ratio of the thermoplastic
resin fibers to the carbon fibers is within the above ranges, the
carbon fibers are easily well dispersed in the aqueous dispersion
medium in a short time and with weak agitation and high mechanical
properties are easily obtained as to the carbon fiber-reinforced
composite molded body manufactured from the slurry.
[0098] The slurry of the present invention contains preferably
0.001 to 1% by mass of the thermoplastic resin fibers of the
present invention, 0.001 to 1% by mass of carbon fibers and 98 to
99.998% by mass of water, more preferably 0.005 to 0.5% by mass of
the thermoplastic resin fibers of the invention, 0.005 to 0.5% by
mass of carbon fibers and 99 to 99.99% by mass of water, and
particularly preferably 0.01 to 0.3% by mass of the thermoplastic
resin fibers of the invention, 0.01 to 0.3% by mass carbon fibers
and 99.4 to 99.98% by mass of water, such that their total is 100%
by mass, based on the total mass of the slurry. When the amount of
each component is within the above ranges, carbon fibers are easily
well dispersed in the aqueous dispersion medium in a short time and
with weak agitation, and high mechanical properties are easily
obtained as to the carbon fiber-reinforced composite molded body
manufactured from the slurry.
<Inferred Action Mechanism>
[0099] Although the action mechanism of the thermoplastic resin
fiber of the present invention to which a dispersant is attached is
unknown, the following action mechanism is inferred.
[0100] While carbon fibers have poor dispersibility in an aqueous
dispersion medium due to intermolecular force, adhesion effect of
sizing agent or the like, the dispersibility can be improved by
using a dispersant compatible with the carbon fibers. When mixing
carbon fibers and thermoplastic resin fibers to which a dispersant
are not attached with an aqueous solution of a dispersant in an
aqueous dispersion medium, it takes time to disperse the
thermoplastic resin fibers and to disperse the carbon fibers. Thus,
in the present invention, it is inferred that the thermoplastic
resin fibers can be rapidly dispersed in the aqueous dispersion
medium by attaching a specific dispersant to the thermoplastic
resin fibers and can enter between the carbon fibers, thereby
generating an effect of quickly dispersing the carbon fibers. Then,
a highly aggregated carbon fiber bundle does not exist in a wet
nonwoven fabric whose dispersibility is improved by using the
thermoplastic resin fibers of the present invention. Therefore, it
is inferred that the thermoplastic resin fibers completely
penetrate the carbon fibers when heat press molding the wet
nonwoven fabric, and mechanical properties of the resulting carbon
fiber-reinforced composite molded body are greatly improved.
However, with regard to the reason (action mechanism) in which the
thermoplastic resin fiber of the present invention is excellent in
the above effect, it is clearly stated here that it is within the
scope of the present invention even if it is different from the
above reason.
<Nonwoven Fabric>
[0101] The present invention also relates to a nonwoven fabric
based on the thermoplastic resin fibers of the present invention
and carbon fibers, in which the amount of the dispersant in the
nonwoven fabric is preferably 0.01 to 1.0% by mass, more preferably
0.03 to 0.5% by mass, and particularly preferably 0.05 to 0.3% by
mass, based on the total mass of thermoplastic resin fibers in the
nonwoven fabric. The amount of dispersant in the nonwoven fabric
can be measured, for example, using the Soxhlet extraction method,
as described in the following examples.
[0102] The number of carbon fiber bundles having a fiber bundle
width of 0.1 mm or more on a surface of the nonwoven fabric of the
present invention is preferably 2000 pieces/m.sup.2 or less, more
preferably 1100 pieces/m.sup.2 or less, more preferably 500
pieces/m.sup.2 or less, and particularly preferably 250
pieces/m.sup.2 or less. The number of carbon fiber bundles can be
determined, for example, by counting the number of carbon fiber
bundles on the surface of the nonwoven fabric cut into an
appropriate dimension (for example, 25 cm.times.25 cm) using a
colony counter pen and calculating the number of carbon fiber
bundles per 1 m.sup.2 of the nonwoven fabric from the obtained
numerical value. The fact that the number of carbon fiber bundles
is equal to or less than the above numerical values indicates that
the carbon fibers are very uniformly dispersed in an aqueous medium
by the thermoplastic resin fibers of the present invention.
[0103] Here, the "fiber bundle width" will be described. As
described previously, since carbon fibers have poor dispersibility
in the aqueous dispersion medium due to intermolecular force or the
like, the carbon fibers tend to align and aggregate in a fiber
axial direction, and as a result, carbon fiber bundles of a
plurality of carbon fibers are formed in the aqueous dispersion
medium. Such carbon fiber bundles are formed, for example, in a
slurry containing thermoplastic resin fibers, carbon fibers and
water, and remain in the nonwoven fabric manufactured from the
slurry. In the present invention, the "fiber bundle width" means a
length of the carbon fiber bundle remaining in the nonwoven fabric
in a direction perpendicular to the fiber axial direction.
<Method for Manufacturing Nonwoven Fabric>
[0104] The nonwoven fabric of the present invention can be
manufactured by papermaking and drying the slurry.
[0105] Specifically, first, a so-called wet papermaking method is
performed in which the aqueous dispersion medium is removed from
the slurry to form a sheet. As a paper machine used for a wet
papermaking method, for example, a known paper machine such as an
inclined wire type paper machine, a cylinder paper machine, a
fourdrinier paper machine or a tanmo paper machine can be used.
[0106] In the subsequent drying, drying is performed using a
cylinder dryer, an air dryer or the like.
[0107] Subsequently, the thickness can be adjusted to an
appropriate thickness by subjecting to thermal pressing processing
such as calendar roll treatment under heating.
[0108] The basis weight of the nonwoven fabric is preferably 20 to
150 g/m.sup.2, and more preferably 40 to 100 g/m.sup.2. When the
basis weight is within the above ranges, deterioration in
operability of the paper machine, such as cutting of the nonwoven
fabric, is easily avoided, and, since the nonwoven fabric can be
dried within an appropriate time, deterioration in productivity is
easily avoided.
[0109] In the present invention, the papermaking speed of the
nonwoven fabric is preferably 10 m/min or more. The upper limit of
the take-up speed is usually 100 m/min or less. The drying
temperature of the nonwoven fabric by a cylinder dryer or the like
is usually 100 to 200.degree. C., and preferably 100 to 150.degree.
C.
<Carbon Fiber-Reinforced Composite Molded Body>
[0110] The present invention also relates to a carbon
fiber-reinforced composite molded body based on the nonwoven fabric
of the present invention.
[0111] The number of carbon fiber bundles having a fiber bundle
width of 0.1 mm or more on a surface of the carbon fiber-reinforced
composite molded body of the present invention is preferably 2000
pieces/m.sup.2 or less, more preferably 1100 pieces/m.sup.2 or
less, more preferably 500 pieces/m.sup.2 or less, and particularly
preferably 250 pieces/m.sup.2 or less. The method for determining
the number of carbon fiber bundles is as described previously. The
fact that the number of carbon fiber bundles is equal to or less
than the above numerical values indicates that the carbon fibers
are very uniformly dispersed in an aqueous medium by the
thermoplastic resin fibers of the present invention.
<Method for Manufacturing Carbon Fiber-Reinforced Composite
Molded Body>
[0112] The carbon fiber-reinforced composite molded body of the
present invention can be manufactured by heat press molding the
nonwoven fabric.
[0113] Accordingly, the present invention also relates to a method
for manufacturing a carbon fiber-reinforced composite molded body,
which comprises papermaking and drying the slurry of the present
invention, and heat press molding the obtained nonwoven fabric.
[0114] By heat press molding the nonwoven fabric, the thermoplastic
resin fibers contained in the nonwoven fabric are at least
partially melted to lose at least a part of the fiber shape, and
act as a matrix resin that bonds a reinforced material (carbon
fiber) in the obtained carbon fiber-reinforced composite molded
body. That is, the thermoplastic resin fibers form at least a part
of the matrix that bonds the carbon fibers in the carbon
fiber-reinforced composite molded body.
[0115] In the method for manufacturing a carbon fiber-reinforced
composite molded body of the present invention, the nonwoven fabric
may be used alone or by stacking a number of sheets. In the case of
stacking a number of sheets, a number of a single type of nonwoven
fabric may be used, or different types of nonwoven fabrics may be
used in combination.
[0116] There is no particular limitation on the method of heat
press molding, and general compression molding such as stampable
molding, press molding, vacuum compression molding or GMT molding
is preferably used. A molding temperature at that time may be
appropriately set according to a flow start temperature and a
decomposition temperature of the thermoplastic resin fiber to be
used. For example, when the thermoplastic resin fiber is
crystalline, the molding temperature is preferably in the range of
the melting point of the thermoplastic resin fiber or more and (the
melting point+100.degree.) C. or less. When the thermoplastic resin
fiber is non-crystalline, the molding temperature is preferably in
the range of the glass transition temperature of the thermoplastic
resin fiber or more and (the glass transition
temperature+200.degree.) C. or less. If necessary, the nonwoven
fabric can also be preheated using an IR heater or the like before
heat molding.
[0117] The pressure at the time of heat press molding is also not
particularly limited, but it is usually performed at a pressure of
0.05 MPa or more, for example, 0.05 to 15 MPa. The time for heat
press molding is also not particularly limited, but a polymer may
be deteriorated if exposed to a high temperature for a long time,
so it is usually preferably within 30 minutes. In addition, the
thickness and density of the obtained carbon fiber-reinforced
composite molded body can be appropriately set depending on the
ratio of carbon fibers in the nonwoven fabric and the pressure
applied. Furthermore, the shape of the resulting carbon
fiber-reinforced composite molded body is not also particularly
limited, and can be appropriately set. Depending on the purpose, it
is also possible to carry out heat molding by laminating a
plurality of nonwoven fabrics having different specifications or
separately arranging nonwoven fabrics having different
specifications in a mold of a certain size. In some cases, it can
be molded in combination with other reinforcing fiber fabrics or
resin composites. Moreover, depending on the purpose, it is also
possible to again heat press mold the carbon fiber-reinforced
composite molded body obtained by heat press molding once.
[0118] The obtained carbon fiber-reinforced composite molded body
is obtained by papermaking and drying a slurry containing the
thermoplastic resin fibers of the present invention and carbon
fibers, and heat press molding the obtained nonwoven fabric.
Therefore, carbon fibers having a long fiber length can be
contained at a high content and carbon fibers arranged in a very
uniform and random manner can be contained, so that mechanical
properties and the isotropy thereof are excellent. In addition,
excellent shaping property is also achieved by heat press molding
the nonwoven fabric.
EXAMPLES
[0119] The present invention will further be specifically described
by giving examples and comparative examples, but the present
invention is not limited to these examples.
<Measurement Method and Evaluation Method>
[0120] Various measurement methods and evaluation methods in
examples and comparative examples are as follows.
<Amount of Dispersant Attached to Thermoplastic Resin Fiber or
Nonwoven Fabric>
[0121] A Soxhlet extractor (manufactured by As One Corporation) was
filled with 1.5 g of thermoplastic resin fibers or 3.0 g of a
nonwoven fabric, and extraction treatment was performed using 150
mL of acetone for 10 hours. The amount of a dispersant in this
extract was quantitatively analyzed by high performance liquid
chromatography to determine the amount of dispersant. In the
determination, a calibration curve prepared using a standard of
each dispersant was used.
<Number of Carbon Fiber Bundles Having Fiber Bundle Width of 1
mm or More per 1 m.sup.2 of Nonwoven Fabric or Carbon
Fiber-Reinforced Composite Molded Body>
[0122] The number of carbon fiber bundles having a fiber bundle
width of 1 mm or more was counted, using a colony counter pen Lite
(manufactured by Iuchi Seieido Co., Ltd.), on a surface of a sample
prepared by cutting a nonwoven fabric or a carbon fiber-reinforced
composite molded body into 25 cm.times.25 cm. From the obtained
numerical values, the number of carbon fiber bundles per 1 m.sup.2
of nonwoven fabric or carbon fiber-reinforced composite molded body
was calculated.
<Dispersibility of Carbon Fibers in Slurry>
[0123] Dispersibility of the carbon fibers in the slurry after
stirring for a predetermined time was visually evaluated.
[0124] It was evaluated by 3 grades: [0125] A (uniform) in which a
carbon fiber bundle was not observed; [0126] B (slightly
non-uniform) in which the carbon fibers are not sufficiently
dispersed and a carbon fiber bundle was observed; and [0127] C
(non-uniform) in which the carbon fibers are not dispersed and
carbon fiber bundles are significantly observed.
<Bending Strength Test>
[0127] [0128] Testing machine: INSTRON 5566 (manufactured by
Instron Japan Co., Ltd.) [0129] Test method: Three-point bending
test [0130] Testing speed: 2 mm/min [0131] Distance between support
points: 40 times the thickness of test piece [0132] Test piece
size: 10 mm.times.100 mm
[0133] Under the above conditions, the maximum bending stress (MPa)
of the carbon fiber-reinforced composite molded body was
measured.
<Charpy Impact Test>
[0134] Testing machine: Charpy impact tester DG-CB (manufactured by
Toyo Seiki Seisaku-sho, Ltd.) [0135] Test piece size: 10
mm.times.100 mm [0136] Impact test method: Flatwise
[0137] Under the above conditions, the Charpy impact value
(KJ/m.sup.2) of the carbon fiber-reinforced composite molded body
was measured.
Example 1
<Manufacture of Thermoplastic Resin Fibers of Present
Invention>
[0138] Into a slash pulper (model: SVP-250-B, manufactured by Kyowa
Iron Works Inc.) was introduced 2.5 kg of chopped fibers of
polyetherimide (circular structure) with a single yarn fineness of
2.2 dtex cut into 5 mm of fiber length, 5 L of an aqueous solution
of a random copolymer (A) prepared to 2.5% by mass was added
thereto, the mixture was stirred at 200 rpm for 10 minutes, 0.1 kg
of a polyether-based polyurethane resin (B) was added to the
obtained mixture, and the mixture was further stirred at 200 rpm
for 10 minutes. Thereafter, a dispersant was attached to a surface
of the polyetherimide fibers by drying at 105.degree. C. for 10
hours using a hot air dryer. The amount of dispersants (A) and (B)
attached to the polyetherimide fibers was 6.7% by mass based on the
total weight of the polyetherimide fibers to which a dispersant was
not attached.
[0139] As the random copolymer (A), a random copolymer of phenyl
glycidyl ether (PGE), ethylene oxide (EO) and propylene oxide (PO)
("ALKOX CP-B1" manufactured by Meisei Chemical Works, Ltd.,
copolymerization ratio EO:PO:PGE=98:1:1, weight-average molecular
weight about 100,000 g/mol, molecular weight distribution about
2.0) was used, and as the polyether-based polyurethane resin (B), a
polymer of bifunctional polyol and hexamethylene diisocyanate
("Pulset HA" manufactured by Meisei Chemical Works, Ltd.,
polymerization ratio [bifunctional polyol:hexamethylene
diisocyanate]=97.1:2.9) was used.
<Manufacture of Slurry>
[0140] Into a stirrer of a tanmo paper machine was introduced 1500
L of distilled water, and 2.5 kg of carbon fibers (manufactured by
Toho Tenax Co., Ltd.: trade name "HT C110", 9 .mu.m fiber diameter,
chopped fibers cut into 13 mm) and 2.5 kg of the polyetherimide
fibers were added thereto in this order, and the mixture was
stirred at 100 rpm to obtain a slurry. The amount of polyetherimide
fibers was 100 parts by mass based on 100 parts by mass of the
carbon fibers.
[0141] The time from the addition of the polyetherimide fibers was
completed until the carbon fibers were uniformly dispersed was
measured, and it was 20 minutes. Moreover, the uniformity of the
carbon fibers in the slurry was visually evaluated, and the carbon
fiber bundle was not observed as long as the slurry was visually
confirmed.
<Manufacture of Nonwoven Fabric>
[0142] The slurry was diluted with distilled water, and papermaking
was carried out using a tanmo paper machine so that the basis
weight was 60 g/m.sup.2. The nonwoven fabric after papermaking was
dried at 105.degree. C. for 4 hours using a hot air dryer to obtain
a nonwoven fabric. The amount of dispersant in the nonwoven fabric
was 0.09% by mass based on the total weight of polyetherimide
fibers in the nonwoven fabric.
[0143] The number of carbon fiber bundles having a fiber bundle
width of 0.1 mm or more on a surface of the nonwoven fabric was 160
pieces/m.sup.2.
<Manufacture of Carbon Fiber-Reinforced Composite Molded
Body>
[0144] The nonwoven fabric was cut into a size of 30 cm.times.15
cm, 27 sheets were laminated and pressed using a hot press
(manufactured by GO-factory Co., Ltd.) at 340.degree. C. and 10 MPa
for 5 minutes to obtain a carbon fiber-reinforced composite molded
body.
[0145] The number of carbon fiber bundles having a fiber bundle
width of 0.1 mm or more on a surface of the carbon fiber-reinforced
composite molded body was 160 pieces/m.sup.2. Further, the bending
strength of the carbon fiber-reinforced composite molded body was
396 MPa, and the Charpy impact value was 38.0 KJ/m.sup.2.
Example 2
[0146] A thermoplastic resin fiber to which a dispersant was
attached, a slurry, a nonwoven fabric and a carbon fiber-reinforced
composite molded body were manufactured and evaluated by the same
method as in Example 1, except that chopped fibers of polyamide
PAST (circular structure) with a single yarn fineness of 2.2 dtex
cut into 5 mm of fiber length were used in place of the chopped
fibers of polyetherimide as a thermoplastic resin fiber, and the
press temperature was changed to 320.degree. C. in place of
340.degree. C. The evaluation results are shown in Table 2
described later.
Example 3
[0147] A thermoplastic resin fiber to which a dispersant was
attached, a slurry, a nonwoven fabric and a carbon fiber-reinforced
composite molded body were manufactured and evaluated by the same
method as in Example 1, except that chopped fibers of polyamide
Ny-6 (circular structure) with a single yarn fineness of 2.2 dtex
cut into 5 mm of fiber length were used in place of the chopped
fibers of polyetherimide as a thermoplastic resin fiber, and the
press temperature was changed to 300.degree. C. in place of
340.degree. C. The evaluation results are shown in Table 2
described later.
Example 4
[0148] A thermoplastic resin fiber to which a dispersant was
attached, a slurry, a nonwoven fabric and a carbon fiber-reinforced
composite molded body were manufactured and evaluated by the same
method as in Example 1, except that chopped fibers of polypropylene
(circular structure) with a single yarn fineness of 2.2 dtex cut
into 5 mm of fiber length were used in place of the chopped fibers
of polyetherimide as a thermoplastic resin fiber, and the press
temperature was changed to 270.degree. C. in place of 340.degree.
C. The evaluation results are shown in Table 2 described later.
Example 5
[0149] A thermoplastic resin fiber to which a dispersant was
attached, a slurry, a nonwoven fabric and a carbon fiber-reinforced
composite molded body were manufactured and evaluated by the same
method as in Example 1, except that only the random copolymer (A)
was used as the dispersant in place of the random copolymer (A) and
the polyether-based polyurethane resin (B). The evaluation results
are shown in Table 2 described later.
Example 6
[0150] A thermoplastic resin fiber to which a dispersant was
attached, a slurry and a nonwoven fabric were manufactured and
evaluated by the same method as in Example 1, except for changing
the adhesion amount of the dispersant from 6.7% to 1.0%, and
performing manufacturing of up to a nonwoven fabric without
manufacturing a carbon fiber-reinforced composite molded body. The
evaluation results are shown in Table 3 described later.
Example 7
[0151] A thermoplastic resin fiber to which a dispersant was
attached, a slurry and a nonwoven fabric were manufactured and
evaluated by the same method as in Example 1, except for changing
the adhesion amount of the dispersant from 6.7% to 0.5%, and
performing manufacturing of up to a nonwoven fabric without
manufacturing a carbon fiber-reinforced composite molded body. The
evaluation results are shown in Table 3 described later.
Example 8
[0152] A thermoplastic resin fiber to which a dispersant was
attached, a slurry and a nonwoven fabric were manufactured and
evaluated by the same method as in Example 1, except for changing
the adhesion amount of the dispersant from 6.7% to 0.25%, and
performing manufacturing of up to a nonwoven fabric without
manufacturing a carbon fiber-reinforced composite molded body. The
evaluation results are shown in Table 3 described later.
Example 9
[0153] A thermoplastic resin fiber to which a dispersant was
attached, a slurry and a nonwoven fabric were manufactured and
evaluated by the same method as in Example 1, except for changing
the adhesion amount of the dispersant from 6.7% to 0.2%, and
performing manufacturing of up to a nonwoven fabric without
manufacturing a carbon fiber-reinforced composite molded body. The
evaluation results are shown in Table 3 described later.
Example 10
[0154] A thermoplastic resin fiber to which a dispersant was
attached, a slurry and a nonwoven fabric were manufactured and
evaluated by the same method as in Example 1, except for changing
the adhesion amount of the dispersant from 6.7% to 0.15%, and
performing manufacturing of up to a nonwoven fabric without
manufacturing a carbon fiber-reinforced composite molded body. The
evaluation results are shown in Table 3 described later.
Comparative Example 1
[0155] Into a stirrer of a tanmo paper machine was introduced 1500
L of distilled water, and 2.5 kg of the carbon fibers used in
Example 1 and 2.5 kg of the polyetherimide fibers before attaching
the dispersant which were used in Example 1 were added thereto in
this order, and the mixture was stirred at 100 rpm.
[0156] Dispersibility of the carbon fibers was poor, and carbon
fiber bundles were remarkably observed.
[0157] A nonwoven fabric and a carbon fiber-reinforced composite
molded body were manufactured and evaluated by the same method as
in Example 1 using the resulting mixture.
[0158] The evaluation results are shown in Tables 1 and 2 described
later.
Comparative Example 2
[0159] Into a stirrer of a tanmo paper machine was introduced 1500
L of distilled water, and 2.5 kg of the carbon fibers used in
Example 1 and 2.5 kg of the polyetherimide fibers before attaching
the dispersant which were used in Example 1 were added thereto in
this order, then 0.025 kg of the random copolymer (A) was added,
and the mixture was stirred at 100 rpm. The type and amount of the
random copolymer (A) added were the same as the type and amount as
in Example 1.
[0160] In the resulting mixture, the carbon fibers were not
sufficiently dispersed in 20 minutes (time in which the carbon
fibers were uniformly dispersed in Examples 1 to 5 of the present
invention) from the completion of addition of the random copolymer
(A), and a carbon fiber bundle was observed.
[0161] A nonwoven fabric and a carbon fiber-reinforced composite
molded body were manufactured and evaluated by the same method as
in Example 1 using the resulting mixture.
[0162] The evaluation results are shown in Tables 1 and 2 described
later.
Comparative Example 3
[0163] Into a slash pulper (model: SVP-250-B, manufactured by Kyowa
Iron Works Inc.) was introduced 2.5 kg of chopped fibers of
polyetherimide (circular structure) with a single yarn fineness of
2.2 dtex cut into 5 mm of fiber length, 5 L of an aqueous solution
of a polyether-based polyurethane resin (B) prepared to 2.5% by
mass was added thereto, and the mixture was stirred at 200 rpm for
10 minutes. Thereafter, a dispersant was attached to a surface of
the polyetherimide fibers by drying at 105.degree. C. for 10 hours
using a hot air dryer. The amount of dispersant (B) attached to the
polyetherimide fibers was 6.7% by mass based on the total weight of
the polyetherimide fibers to which a dispersant was not
attached.
[0164] As the polyether-based polyurethane resin (B), a polymer of
bifunctional polyol and hexamethylene diisocyanate ("Pulset HA"
manufactured by Meisei Chemical Works, Ltd., polymerization ratio
[bifunctional polyol:hexamethylene diisocyanate]=97.1:2.9) was
used.
[0165] Subsequently, a slurry, a nonwoven fabric and a carbon
fiber-reinforced composite molded body were manufactured and
evaluated by the same method as in Example 1, except that a
polyetherimide fiber to which only the polyether-based polyurethane
resin (B) was attached was used. The evaluation results are shown
in Table 2 described later.
Comparative Example 4
[0166] A slurry, a nonwoven fabric and a carbon fiber-reinforced
composite molded body were manufactured and evaluated by the same
method as in Comparative Example 1, except that the PAST fibers
before attaching the dispersant which were used in Example 2 were
used in place of the polyetherimide fibers used in Comparative
Example 1 as a thermoplastic resin fiber, and the press temperature
was changed to 320.degree. C. in place of 340.degree. C. The
evaluation results are shown in Table 2 described later.
Comparative Example 5
[0167] A slurry, a nonwoven fabric and a carbon fiber-reinforced
composite molded body were manufactured and evaluated by the same
method as in Comparative Example 1, except that the Ny-6 fibers
before attaching the dispersant which were used in Example 3 were
used in place of the polyetherimide fibers used in Comparative
Example 1 as a thermoplastic resin fiber, and the press temperature
was changed to 300.degree. C. in place of 340.degree. C. The
evaluation results are shown in Table 2 described later.
Comparative Example 6
[0168] A slurry, a nonwoven fabric and a carbon fiber-reinforced
composite molded body were manufactured and evaluated by the same
method as in Comparative Example 1, except that the polypropylene
fibers before attaching the dispersant which were used in Example 4
were used in place of the polyetherimide fibers used in Comparative
Example 1 as a thermoplastic resin fiber, and the press temperature
was changed to 270.degree. C. in place of 340.degree. C. The
evaluation results are shown in Table 2 described later.
TABLE-US-00001 TABLE 1 Dispersibility of carbon fibers Thermo-
Dispersi- Disper- plastic Rein- bility of sion resin forcing carbon
time fibers fibers Dispersant fibers (min) Example 1 PEI Carbon A +
B A 20 fibers (Attached to PEI fibers) Comparative PEI Carbon None
C Not Example 1 fibers dis- persed Comparative PEI Carbon A B 20
Example 2 fibers (Added after- ward separately from PEI fibers)
TABLE-US-00002 TABLE 2 Evaluation results of carbon
fiber-reinforced composite molded bodies Number Attached Dis-
Amount of Number of carbon of carbon Charpy Thermo- Dis- amount of
persion dispersant in fiber bundles in Press fiber bundles in
Bending impact plastic per- dispersant time nonwoven fabric
nonwoven fabric temperature molded body strength value resin fibers
sant (% by mass) (min) (% by mass) (pieces/m.sup.2) (.degree. C.)
(pieces/m.sup.2) (MPa) (kJ/m.sup.2) Example 1 PEI A + B.sup.1) 6.7
20 0.09 160 340 160 396 38.0 Example 2 PA9T A + B.sup.1) 6.9 20
0.08 144 320 144 216 27.2 Example 3 Ny-6 A + B.sup.1) 6.5 20 0.08
144 300 144 198 24.4 Example 4 PP A + B.sup.1) 6.3 20 0.07 176 270
176 157 21.2 Example 5 PEI A.sup.1) 6.4 20 0.08 1600 340 1600 378
30.4 Comparative PEI None -- 20 -- 6200 340 6200 351 24.8 Example 1
Comparative PEI A.sup.2) -- 20 0.07 3700 340 3700 356 26.8 Example
2 Comparative PEI B.sup.1) 6.7 20 0.06 3400 340 3400 362 27.7
Example 3 Comparative PA9T None -- 20 -- 6500 320 6500 186 19.3
Example 4 Comparative Ny-6 None -- 20 -- 5900 300 5900 174 16.6
Example 5 Comparative PP None -- 20 -- 6000 270 6000 137 16.9
Example 6 .sup.1)Thermoplastic resin fibers to which a dispersant
was attached was used. .sup.2)A dispersant was added afterward
separately from thermoplastic resin fibers.
TABLE-US-00003 TABLE 3 Effects of dispersant amount on carbon fiber
dispersibility Number of carbon fiber Thermo- Attached Dis- bundles
in plastic amount of persion nonwoven resin Dis- dispersant time
fabric fibers persant (% by mass) (min) (pieces/m.sup.2) Example 1
PEI A + B.sup.1) 6.7 20 160 Example 6 PEI A + B.sup.1) 1.0 20 144
Example 7 PEI A + B.sup.1) 0.5 20 160 Example 8 PEI A + B.sup.1)
0.25 20 496 Example 9 PEI A + B.sup.1) 0.2 20 576 Example 10 PEI A
+ B.sup.1) 0.15 20 1136 Comparative PEI None 0 20 6200 Example 1
.sup.1)Thermoplastic resin fibers to which a dispersant was
attached was used.
[0169] As shown in Table 1, when the thermoplastic resin fiber of
the present invention to which a dispersant was attached was used
(Example 1), the carbon fibers were effectively uniformly
dispersed, and no carbon fiber bundle was observed. This good
dispersion was achieved in a short time and with weak agitation.
This means that the thermoplastic resin fiber of the present
invention effectively acted as a dispersant for carbon fibers, and
the carbon fibers were very uniformly dispersed in the aqueous
dispersion medium.
[0170] On the other hand, when the thermoplastic resin fiber to
which a dispersant was not attached was used (Comparative Example
1), the carbon fibers were not dispersed.
[0171] In addition, when the dispersant (A) was added separately
from the thermoplastic resin fiber (Comparative Example 2), the
carbon fibers were not effectively uniformly dispersed in a short
time and with weak agitation.
[0172] As shown in Table 2, when the thermoplastic resin fiber of
the present invention to which a dispersant was attached was used
(Examples 1 to 5), the number of carbon fiber bundles in the
nonwoven fabric and in the molded body was extremely small, and
higher bending strength and Charpy impact value of the molded body
were obtained, without depending on the type of the thermoplastic
resin fiber. This means that the thermoplastic resin fiber of the
present invention effectively acted as a dispersant for carbon
fibers, and the carbon fibers were uniformly dispersed, resulting
in improved mechanical properties of the molded body.
[0173] On the other hand, when the thermoplastic resin fiber to
which a dispersant was not attached was used and a dispersant was
not used (Comparative Example 1 and Comparative Examples 4 to 6),
the carbon fibers were not dispersed, and as a result, the numbers
of carbon fiber bundles in the nonwoven fabric and in the molded
body were extremely large, and only extremely low bending strength
and Charpy impact value of the molded body were obtained.
[0174] Moreover, when the thermoplastic resin fiber to which a
dispersant was not attached was used and the dispersant (A) was
later added separately from the thermoplastic resin fiber
(Comparative Example 2), and when the thermoplastic resin fiber to
which only the dispersant (B) was attached was used (Comparative
Example 3), the carbon fibers were not sufficiently dispersed, and
as a result, the numbers of carbon fiber bundles in the nonwoven
fabric and in the molded body were large, and only lower bending
strength and Charpy impact value of the molded body were
obtained.
[0175] As shown in Table 3, even when the adhesion amount of the
dispersant of the thermoplastic resin fiber was changed, dispersion
of the carbon fibers was good, and the number of carbon fiber
bundles in the obtained nonwoven fabric was small.
INDUSTRIAL APPLICABILITY
[0176] Since the thermoplastic resin fibers of the present
invention can effectively disperse carbon fibers, it is used as an
excellent dispersant of carbon fibers.
[0177] The thermoplastic resin fibers of the present invention is
used as an excellent dispersant of carbon fibers in a slurry
containing the thermoplastic resin fibers of the present invention,
carbon fibers and water, and the carbon fibers are well dispersed
in the slurry in a short time and with weak agitation. Therefore,
it has economic advantages for the manufacture of the slurry.
[0178] A carbon fiber-reinforced composite molded body manufactured
from a nonwoven fabric based on the thermoplastic resin fibers of
the present invention and carbon fibers has improved mechanical
properties due to the well dispersed carbon fibers. In the carbon
fiber-reinforced composite molded body, the thermoplastic resin
fiber of the present invention acts as a matrix resin, so that the
thermoplastic resin fiber of the present invention is used as a
matrix resin precursor in the slurry and the nonwoven fabric. Since
the carbon fiber-reinforced composite molded body of the present
invention has improved mechanical properties, it can be extremely
suitably used, but is not particularly limited, in many
applications, such as in general industrial material fields,
electric and electronic fields, civil engineering and construction
fields, aircraft, automotive, rail and marine fields, agricultural
material fields, optical material fields, and medical material
fields.
* * * * *