U.S. patent application number 16/638573 was filed with the patent office on 2021-05-20 for moldings of fiber-reinforced thermoplastic resin.
This patent application is currently assigned to TORAY INDUSTRIES, INC.. The applicant listed for this patent is TORAY INDUSTRIES, INC.. Invention is credited to Yuki MITSUTSUJI, Atsuki TSUCHIYA, Kazuki YOSHIHIRO.
Application Number | 20210147664 16/638573 |
Document ID | / |
Family ID | 1000005373543 |
Filed Date | 2021-05-20 |
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United States Patent
Application |
20210147664 |
Kind Code |
A1 |
YOSHIHIRO; Kazuki ; et
al. |
May 20, 2021 |
MOLDINGS OF FIBER-REINFORCED THERMOPLASTIC RESIN
Abstract
To provide a fiber reinforced thermoplastic resin molded article
having excellent impact strength and flexural strength, provided is
a fiber reinforced thermoplastic resin molded article, including: a
carbon fiber (A), an organic fiber (B) having a strand strength of
1500 MPa or more and, a thermoplastic resin (C), wherein the fiber
reinforced thermoplastic resin molded article contains 5 to 45
parts by weight of the carbon fiber (A), 1 to 45 parts by weight of
the organic fiber (B), and 20 to 94 parts by weight of the
thermoplastic resin (C) with respect to 100 parts by weight of the
total of the carbon fiber (A), the organic fiber (B), and the
thermoplastic resin (C), wherein a ratio (L.sub.co/l.sub.no) of the
critical fiber length L.sub.co of the organic fiber (B) to the
number average fiber length l.sub.no of the organic fiber (B) is
0.9 or more and 2.0 or less, and wherein an interfacial shear
strength between the organic fiber (B) and the thermoplastic resin
(C) is 3.0 MPa or more and 50 MPa or less.
Inventors: |
YOSHIHIRO; Kazuki;
(Nagoya-shi, JP) ; MITSUTSUJI; Yuki; (Nagoya-shi,
JP) ; TSUCHIYA; Atsuki; (Nagoya-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TORAY INDUSTRIES, INC. |
Tokyo |
|
JP |
|
|
Assignee: |
TORAY INDUSTRIES, INC.
Tokyo
JP
|
Family ID: |
1000005373543 |
Appl. No.: |
16/638573 |
Filed: |
September 3, 2018 |
PCT Filed: |
September 3, 2018 |
PCT NO: |
PCT/JP2018/032554 |
371 Date: |
February 12, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C08L 23/12 20130101 |
International
Class: |
C08L 23/12 20060101
C08L023/12 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 5, 2017 |
JP |
2017-169953 |
Claims
1. A fiber reinforced thermoplastic resin molded article,
comprising: a carbon fiber (A), an organic fiber (B) having a
strand strength of 1500 MPa or more and, a thermoplastic resin (C),
wherein said fiber reinforced thermoplastic resin molded article
contains 5 to 45 parts by weight of said carbon fiber (A), 1 to 45
parts by weight of said organic fiber (B), and 20 to 94 parts by
weight of said thermoplastic resin (C) with respect to 100 parts by
weight of the total of said carbon fiber (A), said organic fiber
(B), and said thermoplastic resin (C), wherein a ratio
(L.sub.co/l.sub.no) of the critical fiber length L.sub.co of said
organic fiber (B) to the number average fiber length l.sub.no of
said organic fiber (B) is 0.9 or more and 2.0 or less, and wherein
an interfacial shear strength between said organic fiber (B) and
said thermoplastic resin (C) is 3.0 MPa or more and 50 MPa or
less.
2. The fiber reinforced thermoplastic resin molded article
according to claim 1, wherein said organic fiber (B) has a single
fiber tenacity of 50 cN or more.
3. The fiber reinforced thermoplastic resin molded article
according to claim 1, wherein a ratio (L.sub.cc/L.sub.co) of the
critical fiber length L.sub.cc of said carbon fiber (A) to the
critical fiber length L.sub.co of said organic fiber (B) is 0.1 or
more and 0.4 or less.
4. The fiber reinforced thermoplastic resin molded article
according to claim 1, wherein said organic fiber (B) is at least
one selected from the group consisting of liquid crystalline
polyester fibers, aramid fibers, and
poly(paraphenylenebenzoxazole)fibers.
5. The fiber reinforced thermoplastic resin molded article
according to claim 1, wherein said thermoplastic resin (C) is at
least one selected from the group consisting of polypropylene
resins, polyester resins, and polyarylene sulfide resins.
6. The fiber reinforced thermoplastic resin molded article
according to claim 1, wherein said organic fiber (B) has a number
average fiber length l.sub.no of 2000 m or more and 15000 m or
less.
7. The fiber reinforced thermoplastic resin molded article
according to claim 2, wherein a ratio (L.sub.cc/L.sub.co) of the
critical fiber length L.sub.cc of said carbon fiber (A) to the
critical fiber length L.sub.co of said organic fiber (B) is 0.1 or
more and 0.4 or less.
8. The fiber reinforced thermoplastic resin molded article
according to claim 2, wherein said organic fiber (B) is at least
one selected from the group consisting of liquid crystalline
polyester fibers, aramid fibers, and poly(paraphenylenebenzoxazole)
fibers.
9. The fiber reinforced thermoplastic resin molded article
according to claim 2, wherein said thermoplastic resin (C) is at
least one selected from the group consisting of polypropylene
resins, polyester resins, and polyarylene sulfide resins.
10. The fiber reinforced thermoplastic resin molded article
according to claim 2, wherein said organic fiber (B) has a number
average fiber length l.sub.no of 2000 m or more and 15000 .mu.m or
less.
Description
TECHNICAL FIELD
[0001] The present invention relates to fiber reinforced
thermoplastic resin molded articles.
BACKGROUND ART
[0002] Molded articles containing a reinforcement fiber and a
thermoplastic resin are light in weight, have excellent mechanical
properties, and thus, are widely used in sports goods applications,
aerospace applications, general industry applications, and the
like. Examples of reinforcement fibers to be used for these molded
articles include: metal fibers such as aluminum fibers and
stainless steel fibers; inorganic fibers such as silicon carbide
fibers and carbon fibers; organic fibers such as aramid fibers and
poly(paraphenylenebenzoxazole) (PBO) fibers; and the like. A carbon
fiber is suitable from the viewpoint of a balance among specific
strength, specific stiffness, and lightness.
[0003] A carbon fiber has excellent specific strength and specific
stiffness, and thus, molded articles reinforced with a carbon fiber
have excellent lightness and mechanical properties. Because of
this, such molded articles are widely used in various fields such
as electronic equipment housings and automobile members. However,
molded articles are required to be even lighter and thinner in the
above-mentioned applications, and in particular, molded articles
such as housings are required to have even higher mechanical
properties (in particular, flexural strength and impact
characteristics).
[0004] Examples of proposed means for enhancing the impact
characteristics of a carbon fiber reinforced thermoplastic resin
molded article include a long fiber reinforced composite resin
composition containing an olefinic resin, an organic long fiber,
and a carbon fiber (see, for example, Patent Literature 1). In
addition, composite fiber reinforced thermoplastic resin pellets
are proposed as pellets having excellent stiffness and impact
resistance, wherein the composite fiber reinforced thermoplastic
resin pellets contain a thermoplastic resin and two or more
selected from organic fibers and carbon fibers, and wherein the
fibers are present in a twisted state and coexist with the
thermoplastic resin (see, for example, Patent Literature 2). In
addition, a fiber reinforced thermoplastic resin molded article
containing a carbon fiber, an organic fiber, and a thermoplastic
resin is proposed as a fiber reinforced thermoplastic resin molded
article having excellent impact strength and low temperature impact
strength, wherein the carbon fiber and the organic fiber each have
an average fiber length in a specific range, and further, wherein,
in the carbon fiber and the organic fiber, the average
straight-line distance between two edges of a single fiber and the
average fiber length are in a specific relationship (see, for
example, Patent Literature 3).
CITATION LIST
Patent Literature
[0005] Patent Literature 1: JP2009-114332A
[0006] Patent Literature 2: JP2009-24057
[0007] Patent Literature 3: WO2014/098103
SUMMARY OF INVENTION
Technical Problem
[0008] However, the technologies described in Patent Literature 1
to 3 afford still insufficient mechanical properties, particularly
flexural strength and impact strength. Thus, conventional
technologies for fiber reinforced thermoplastic resin molded
articles whose matrix is a thermoplastic resin do not afford a
fiber reinforced thermoplastic resin molded article that achieves
high mechanical properties, particularly both flexural strength and
impact strength. There is a demand for development of such a fiber
reinforced thermoplastic resin molded article. In view of the
above-mentioned problems posed by conventional technologies, an
object of the present invention is to provide a fiber reinforced
thermoplastic resin molded article having excellent mechanical
properties (in particular, impact strength and flexural
strength).
Solution to Problem
[0009] To solve the problems, the present invention mainly has the
following constituents.
[0010] A fiber reinforced thermoplastic resin molded article,
comprising: a carbon fiber (A), an organic fiber (B) having a
strand strength of 1500 MPa or more and, a thermoplastic resin (C),
wherein the fiber reinforced thermoplastic resin molded article
contains 5 to 45 parts by weight of the carbon fiber (A), 1 to 45
parts by weight of the organic fiber (B), and 20 to 94 parts by
weight of the thermoplastic resin (C) with respect to 100 parts by
weight of the total of the carbon fiber (A), the organic fiber (B),
and the thermoplastic resin (C), wherein a ratio
(L.sub.co/l.sub.no) of the critical fiber length L.sub.co of the
organic fiber (B) to the number average fiber length l.sub.no of
the organic fiber (B) is 0.9 or more and 2.0 or less, and wherein
an interfacial shear strength between the organic fiber (B) and the
thermoplastic resin (C) is 3.0 MPa or more and 50 MPa or less.
Advantageous Effects of Invention
[0011] A fiber reinforced thermoplastic resin molded article
according to the present invention contains a carbon fiber, an
organic fiber, a thermoplastic resin, wherein the ratio
L.sub.co/l.sub.no of the organic fiber and the interfacial shear
strength between the organic fiber and the thermoplastic resin are
each brought within a specific range. This results in making it
possible to obtain a molded article which allows more energy to be
absorbed thanks to the pull-out of organic fiber when the molded
article undergoes an impact, and which thus achieves high flexural
strength and impact strength. Such a molded article can be obtained
by using a fiber reinforce thermoplastic resin molding material
according to the present invention. Then, such a molded article is
very useful for electrical and electronic equipment, OA equipment,
home electrical appliances, housings, automobile parts, and the
like.
BRIEF DESCRIPTION OF DRAWINGS
[0012] FIG. 1 is a schematic view depicting an example of a first
step in which a single fiber is adhered, in straight form, to a
fixing jig in adhesion evaluation in Examples and Comparative
Examples.
[0013] FIG. 2 is a schematic view depicting an example of a single
fiber adhered to a fixing jig in adhesion evaluation in Examples
and Comparative Examples.
[0014] FIG. 3 is a schematic view depicting an example of an
adhesion evaluation sample in a second step in Examples and
Comparative Examples.
[0015] FIG. 4 is a schematic view depicting an example of a single
fiber pull-out test in a third step in adhesion evaluation in
Examples and Comparative Examples.
DESCRIPTION OF EMBODIMENTS
[0016] A fiber reinforced thermoplastic resin molded article
according to the present invention (hereinafter referred to as a
"molded article" for short) contains at least a carbon fiber (A),
an organic fiber (B), and a thermoplastic resin (C).
[0017] Frictional resistance experienced by fiber pull-out is one
of the factors that contribute to absorption of impact energy
resulting from an impact undergone by a fiber reinforced
thermoplastic resin molded article. More specifically, a molded
article that has undergone impact generates cracking, which
fractures fibers and advances linearly to incur brittle breaking.
On the other hand, if the generated cracking changes its direction
at the interface with the fibers and thus causes the fibers to be
more easily pulled out of the thermoplastic resin, frictional
resistance experienced by the fiber pull-out allows the impact
energy to be absorbed more easily.
[0018] The present inventors have found that a specific ratio of
the critical fiber length (L.sub.co) of an organic fiber (B) to the
number average fiber length (l.sub.no) of an organic fiber in a
molded article causes fiber pull-out resulting from interfacial
debonding to occur more preferentially in material breaking caused
by the impact on the molded article than the fiber fracture of the
organic fiber. The present inventors have further discovered that
friction caused by fiber pull-out at the interface between organic
fiber and resin increases the amount of impact energy absorption
and enhances the impact strength of the molded article. In
addition, the present inventors have discovered that a
thermoplastic resin and an organic fiber (B) which have a specific
range of interfacial shear strength therebetween contribute to
enhancing the static mechanical strength such as the flexural
strength of the molded article.
[0019] As above-mentioned, the present inventors have discovered
that high flexural strength and high impact strength are both
achieved for a molded article by allowing the critical fiber length
(L.sub.co) of the organic fiber and the number average fiber length
(l.sub.no) of the organic fiber in the molded article to be each in
a specific range, and allowing the interfacial shear strength
between the thermoplastic resin (C) and the organic fiber (B) to be
in a specific range.
[0020] <Carbon Fiber (A)>
[0021] A carbon fiber (A) according to the present invention has a
fiber reinforcement effect on a thermoplastic resin (C), which can
thus have higher mechanical properties. If a carbon fiber has
unique characteristics such as electrical conductivity and thermal
conductivity, such a carbon fiber can give a molded article these
properties, which cannot be given by only the thermoplastic resin
(C).
[0022] The carbon fiber is not limited to any particular one, and
examples thereof include PAN carbon fibers, pitch carbon fibers,
rayon carbon fibers, cellulosic carbon fibers, vapor-grown carbon
fibers, graphitized fibers thereof, and the like. A PAN carbon
fiber is a carbon fiber the raw material of which is a
polyacrylonitrile fiber. A pitch carbon fiber is a carbon fiber the
raw material of which is petroleum tar or petroleum pitch. A
cellulosic carbon fiber is a carbon fiber the raw material of which
is viscose rayon, cellulose acetate, or the like. A vapor-grown
carbon fiber is a carbon fiber the raw material of which is
hydrocarbon or the like.
[0023] Furthermore, preferable carbon fibers are ones which have a
surface oxygen concentration [O/C] of 0.05 to 0.5 as an atomicity
ratio of oxygen (O) to carbon (C) in the fiber surface, as measured
by X-ray photoelectron spectroscopy. A surface oxygen concentration
of 0.05 or more makes it possible to secure a sufficient amount of
functional group in the surface of the carbon fiber, which can thus
obtain strong adhesion to the thermoplastic resin (C), and
accordingly, further enhances the flexural strength and tensile
strength of the molded article. The surface oxygen concentration is
more preferably 0.08 or more, still more preferably 0.1 or more. In
addition, the upper limit of the surface oxygen concentration is
not limited to any particular value, and is generally preferably
0.5 or less from the viewpoint of a balance between the handling
and productivity of a carbon fiber. The surface oxygen
concentration is more preferably 0.4 or less, still more preferably
0.3 or less.
[0024] The surface oxygen concentration of a carbon fiber can be
determined by X-ray photoelectron spectroscopy in the following
manner. First, if any sizing agent or the like is adhered on the
surface of the carbon fiber, the sizing agent or the like is
removed with a solvent. The carbon fiber filament is cut into
pieces each having a length of 20 mm, and the pieces are spread and
arranged on a copper-made sample support table. Subsequently, the
inside of a sample chamber is kept at 1.times.10.sup.-8 Torr using
AlK.alpha.1 or AlK.alpha.2 as an X-ray source. As a value for the
correction of a peak which should be carried out due to the
occurrence of electrostatic charging during the measurement, the
kinetic energy value (K.E.) of the main peak of C.sub.1s is set to
1202 eV. The C.sub.1s peak area is determined by drawing, as K.E.,
a linear baseline in a range of from 1191 to 1205 eV. The O.sub.1s
peak area is determined by drawing, as K.E., a linear base line in
a range of from 947 to 959 eV.
[0025] Here, the surface oxygen concentration [O/C] is calculated
as an atomicity ratio from the ratio of the O.sub.1s peak area to
the C.sub.1s peak area using a sensitivity correction value
inherent to a device. A model ES-200 device manufactured by Kokusai
Electric Inc. is used as an X-ray photoelectron spectroscopy
device, and a sensitivity correction value of 1.74 is used.
[0026] Examples of means for adjusting the surface oxygen
concentration [O/C] to 0.05 to 0.5 include, but are not limited
particularly to, techniques such as an electrolytic oxidation
treatment, a chemical oxidation treatment, and a gas phase
oxidation treatment. Among these, an electrolytic oxidation
treatment is preferable.
[0027] The average fiber diameter of the carbon fiber (A) is not
limited to any particular value, and is preferably 1 to 20 .mu.m,
more preferably 3 to 15 .mu.m, from the viewpoint of the mechanical
properties and surface appearance of a molded article.
[0028] To form a carbon fiber bundle, the number of single fibers
therein is, without particular limitation, preferably 100 to
350,000, and more preferably 20,000 to 100,000 from the viewpoint
of productivity.
[0029] For the purpose of enhancing adhesion between the carbon
fiber (A) and the thermoplastic resin (C) or other purposes, the
surface of the carbon fiber may be treated. Examples of methods of
treating the surface include an electrolytic treatment, an
ozonation treatment, an UV treatment, and the like.
[0030] For the purpose of preventing the fluffing of the carbon
fiber, enhancing the adhesion between the carbon fiber and the
thermoplastic resin (C), or other purposes, a sizing agent may be
applied to the carbon fiber. Applying a sizing agent makes it
possible to enhance the surface properties of the carbon fiber,
such as the properties of a functional group, and to enhance the
adhesion and the composite comprehensive properties. Examples of
sizing agents include epoxy resins, phenol resins, polyethylene
glycol, polyurethanes, polyesters, emulsifiers, surfactants, and
the like. These may be used in combination of two or more kinds
thereof. The sizing agent is preferably water-soluble or
water-dispersible. An epoxy resin that has excellent wettability
against carbon fibers is preferable, and a multi-functional epoxy
resin is more preferable. More specifically, those enumerated below
as examples of surface treatment agents for an organic fiber may be
used.
[0031] The amount of the sizing agent to be adhered is preferably
0.01 to 10 wt % with respect to 100 wt % of the total of the sizing
agent and the carbon fiber. If the amount of the sizing agent to be
adhered is 0.01 wt % or more, the adhesion to the thermoplastic
resin (C) can be further enhanced. The amount of the sizing agent
to be adhered is more preferably 0.05 wt % or more, still more
preferably 0.1 wt % or more. On the other hand, if the amount of
the sizing agent to be adhered is 10 wt % or less, the physical
properties of the thermoplastic resin (C) can be maintained at
higher levels. The amount of the sizing agent to be adhered is more
preferably 5 wt % or less, still more preferably 2 wt % or
less.
[0032] Examples of means for applying a sizing agent include, but
are not limited particularly to, a method in which a sizing agent
is dissolved (or dispersed) in a solvent (or a dispersion medium if
the sizing agent is dispersed) to prepare a sizing treatment
liquid, which is then applied to a carbon fiber, and the solvent is
then dried/evaporated to be removed. Examples of methods of
applying a sizing treatment liquid to a carbon fiber include: a
method in which a carbon fiber is immersed in a sizing treatment
liquid through a roller; a method in which a carbon fiber is
brought into contact with a roller having a sizing treatment liquid
adhered thereto; and a method in which a sizing treatment liquid in
the form of fine mists is atomized onto a carbon fiber. The means
for applying a sizing agent may be in either one of a batch mode
and a continuous mode, and is preferably in a continuous mode
because this mode affords better productivity and lower unevenness.
In this case, it is preferable to adjust the concentration or
temperature of the sizing treatment liquid and the tension of the
carbon fiber so that the amount of the sizing agent adhered to a
carbon fiber can become uniform within a proper range. It is more
preferable that the carbon fiber is vibrated with ultrasonic waves
during the application of the sizing treatment liquid.
[0033] The drying temperature and the drying time should be
adjusted in accordance with the amount of the compound to be
adhered. The drying temperature is preferably 150.degree. C. or
more and 350.degree. C. or less, more preferably 180.degree. C. or
more and 250.degree. C. or less, from the viewpoint of completely
removing the solvent used in the sizing treatment liquid, reducing
the time required for the drying, preventing the thermal
degradation of the sizing agent, and preventing the sized carbon
fiber from being hardened to have worse spreadability.
[0034] Examples of solvents to be used in a sizing treatment liquid
include water, methanol, ethanol, dimethylformamide,
dimethylacetamide, acetone, and the like. from the viewpoint of
easy handling and disaster prevention, water is preferred. Thus, in
cases where a compound that is water-insoluble or is poorly soluble
in water is used as a sizing agent, it is preferable to add an
emulsifier or a surfactant to disperse the compound in water before
usage. Specific examples of emulsifiers or surfactants that can be
used include: an anionic emulsifier such as a styrene-maleic
anhydride copolymer, an olefin-maleic anhydride copolymer, a
formaldehyde condensate of a naphthalene sulfonic acid salt, and
sodium polyacrylate; a cationic emulsifier such as
polyethyleneimine and polyvinylimidazoline; and a nonionic
emulsifier such as a nonylphenol ethylene oxide adduct, polyvinyl
alcohol, a polyoxyethylene ether ester copolymer, and a sorbitan
ester ethyl oxide adduct. A nonionic emulsifier having a low
interaction hardly interferes with the adhesion effect of a
functional group contained in the sizing agent, and thus, is
preferable.
[0035] The carbon fiber (A) content of a molded article according
to the present invention is 5 to 45 parts by weight (5 parts by
weight or more and 45 parts by weight or less) with respect to 100
parts by weight of the total of the carbon fiber (A), the organic
fiber (B), and the thermoplastic resin (C). A carbon fiber (A)
content of less than 5 parts by weight decreases the impact
strength of the molded article. The carbon fiber (A) content is
preferably 10 parts by weight or more, more preferably 20 parts by
weight or more. On the other hand, a carbon fiber (A) content of
more than 45 parts by weight decreases the dispersibility of fibers
and thus increases entanglement between fibers. This results in
breaking fibers, thus shortening the fiber length and decreasing
the impact strength. The carbon fiber (A) content is preferably 30
parts by weight or less.
[0036] <Thermoplastic Resin (C)>
[0037] In the present invention, the thermoplastic resin (C) is a
matrix resin that constitutes part of a molded article. The
thermoplastic resins (C) preferably has a molding temperature
(melting temperature) of 200 to 450.degree. C., and examples of
such a thermoplastic resin include polyolefin resins, polystyrene
resins, polyamide resins, vinyl halide resins, polyacetal resins,
saturated polyester resins, polycarbonate resins, polyarylsulfone
resins, polyaryl ketone resins, polyarylene ether resins,
polyarylene sulfide resins, polyaryl ether ketone resins, polyether
sulfone resins, polyarylene sulfide sulfone resins, polyalylate
resins, polyamide resins, and the like. These can be used in
combination of two or more kinds thereof. A preferable polyolefin
resin is a polypropylene resin.
[0038] Among these thermoplastic resins (C), at least one selected
from the group consisting of polypropylene resins, polyester
resins, and polyarylene sulfide resins is more preferable because
these resins are light in weight and have an excellent balance
between mechanical properties and moldability, and polypropylene
resins are still more preferable because of their excellent
general-purpose properties. Polypropylene resins may be unmodified
or modified.
[0039] Specific examples of unmodified polypropylene resins
include: homopolymers of propylene; and copolymers of propylene and
at least one monomer selected from the group consisting of
.alpha.-olefins, conjugated dienes, non-conjugated dienes, and
other thermoplastic monomers; and the like. Examples of copolymers
include random copolymers and block copolymers. Examples of
.alpha.-olefins include C.sub.2-C.sub.12 .alpha.-olefins excluding
propylene, such as ethylene, 1-butene, 3-methyl-1-butene,
4-methyl-1-pentene, 3-methyl-1-pentene, 4-methyl-1-hexene,
4,4-dimethyl-1-hexene, 1-nonene, 1-octene, 1-heptene, 1-hexene,
1-decene, 1-undecene, 1-dodecene, and the like. Examples of
conjugated dienes and non-conjugated dienes include butadiene,
ethylidene norbomene, dicyclopentadiene, 1,5-hexadiene, and the
like. These may be used in combination of two or more kinds
thereof. Suitable examples include polypropylene,
ethylene/propylene copolymers, propylene/1-butene copolymers,
ethylene/propylene/1-butene copolymers, and the like. Propylene
homopolymers are preferable from the viewpoint of enhancing the
stiffness of a molded article. Random or block copolymers of
propylene and at least one monomer selected from the group
consisting of .alpha.-olefins, conjugated dienes, and
non-conjugated dienes are preferable from the viewpoint of
enhancing the impact strength of a molded article.
[0040] In addition, the modified polypropylene is preferably an
acid-modified polypropylene resin, more preferably an acid-modified
polypropylene resin having a carboxylic acid and/or a carboxylate
group bound to the polymer chain. The above-mentioned acid-modified
polypropylene resins can be obtained by various methods. For
example, the acid-modified polypropylene resin can be obtained by
allowing an unmodified polypropylene resin to be graft-polymerized
with a monomer having a neutralized or unneutralized carboxylic
group and/or a monomer having a saponified or unsaponified
carboxylic ester group.
[0041] Here, examples of monomers having a neutralized or
unneutralized carboxylic group and monomers having a saponified or
unsaponified carboxylic ester group include ethylenic unsaturated
carboxylic acids, anhydrides thereof, ethylenic unsaturated
carboxylic esters, and the like.
[0042] Examples of ethylenic unsaturated carboxylic acids include
(meth)acrylic acids, maleic acids, fumaric acids,
tetrahydrophthalic acids, itaconic acids, citraconic acids,
crotonic acids, isocrotonic acids and the like. Examples of
anhydrides thereof include nadic acid TM
(endocis-bicyclo[2,2,1]hepto-5-ene-2,3-dicarboxylic acid), maleic
anhydrides, citraconic anhydrides, and the like.
[0043] Examples of ethylenic unsaturated carboxylic esters include:
(meth)acrylic esters such as methyl (meth)acrylate, ethyl
(meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate,
iso-butyl (meth)acrylate, tert-butyl (meth)acrylate, n-amyl
(meth)acrylate, isoamyl (meth)acrylate, n-hexyl (meth)acrylate,
2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, decyl
(meth)acrylate, dodecyl (meth)acrylate, octadecyl (meth)acrylate,
stearyl (meth)acrylate, tridecyl (meth)acrylate, lauroyl
(meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate,
phenyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl
(meth)acrylate, dicyclopentenyl (meth)acrylate, dimethylaminoethyl
(meth)acrylate, and diethylaminoethyl (meth)acrylate; hydroxyl
group-containing (meth)acrylic esters such as hydroxyethyl
acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl
(meth)acrylate, 4-hydroxybutyl acrylate, lactone modified
hydroxyethyl (meth)acrylate, and 2-hydroxy-3-phenoxypropyl
acrylate; epoxy group-containing (meth)acrylic acid esters such as
glycidyl (meth)acrylate and methylglycidyl (meth)acrylate;
aminoalkyl (meth)acrylates such as N,N-dimethylaminoethyl
(meth)acrylate, N,N-diethylaminoethyl (meth)acrylate,
N,N-dimethylaminopropyl (meth)acrylate, N,N-dipropylaminoethyl
(meth)acrylate, N,N-dibutylaminoethyl (meth)acrylate, and
N,N-dihydroxyethylaminoethyl (meth)acrylate; and the like.
[0044] These can be used in combination of two or more kinds
thereof. Among these, ethylenic unsaturated carboxylic anhydrides
are preferable, and maleic anhydrides are more preferable.
[0045] Examples of polyester resins include polyethylene
terephthalate, polybutylene terephthalate, polyethylene
naphthalate, and copolymers thereof.
[0046] Examples of polyarylene sulfide resins include polyphenylene
sulfide (PPS) resins, polyphenylene sulfide sulfone resins,
polyphenylene sulfide ketone resins, random or block copolymers
thereof, and the like. These may be used in combination of two or
more kinds thereof. Among these, polyphenylene sulfide resins are
particularly preferably used.
[0047] A polyarylene sulfide resin can be produced by any method,
for example, a method of obtaining a polymer having a relatively
small molecular weight described in JP45-3368B, a method of
obtaining a polymer having a relatively large molecular weight
described in JP52-12240B and JP61-7332A, and the like.
[0048] The obtained polyarylene sulfide resin may be allowed to
undergo various treatments such as: cross-linking the resin and
imparting a higher molecular weight to the resin by heating in air;
heat-treating the resin under an atmosphere of inert gas such as
nitrogen or under reduced pressure; washing the resin with an
organic solvent, hot-water, or an acid aqueous solution; activating
the resin with a functional group-containing compound such as an
acid anhydride, amine, isocyanate, and a functional
group-containing disulfide compound.
[0049] Examples of methods of heating a polyarylene sulfide resin
to cross-link the resin and impart a higher molecular weight to the
resin include a method in which a polyarylene sulfide resin is
heated until the resin obtains a desired melt viscosity in a heated
container at a predetermined temperature under an oxidizing gas
atmosphere such as air or oxygen or under an atmosphere of a gas
mixture of the oxidizing gas and an inert gas such as nitrogen or
argon. The heat-treatment temperature is preferably in a range of
from 200 to 270.degree. C., and the heat-treatment time is
preferably in a range of from 2 to 50 hours. Adjusting the
treatment temperature and the treatment time makes it possible to
adjust the viscosity of the obtained polymer in a desired range.
Examples of heat-treatment devices include common hot air dryers,
rotary heating devices, heating devices with agitating blades, and
the like. Rotary heating devices or heating devices with agitating
blades are preferably used from the viewpoint of efficient and more
uniform heat-treatment.
[0050] If a polyarylene sulfide resin is treated under reduced
pressure, the pressure is preferably 7,000 Nm.sup.-2 or less.
Examples of heat-treatment devices include common hot air dryers,
rotary heating devices, heating devices with agitating blades, and
the like. Rotary heating devices or heating devices with agitating
blades are preferably used from the viewpoint of efficient and more
uniform heat-treatment.
[0051] In cases where a polyarylene sulfide resin is washed with an
organic solvent, examples of organic solvents include:
nitrogen-containing polar solvents such as N-methylpyrrolidone,
dimethylformamide, and dimethylacetamide; sulfoxide-based and
sulfone-based solvents such as dimethylsulfoxide and
dimethylsulfone; ketone-based solvents such as acetone,
methylethylketone, diethylketone, and acetophenone; ether-based
solvents such as dimethylether, dipropylether, and tetrahydrofuran;
halogen-based solvents such as chloroform, methylene chloride,
trichloroethylene, ethylene dichloride, dichloroethane,
tetrachloroethane, and chlorobenzene; alcohol-based or phenol-based
solvents such as methanol, ethanol, propanol, butanol, pentanol,
ethylene glycol, propylene glycol, phenol, cresol, and polyethylene
glycol; and aromatic hydrocarbon-based solvents such as benzene,
toluene, and xylene. These may be used in combination of two or
more kinds thereof. Among these organic solvents,
N-methylpyrrolidone, acetone, dimethylformamide, chloroform, and
the like are preferably used. Examples of methods of washing with
an organic solvent include a method in which a polyarylene sulfide
resin is immersed in an organic solvent. If necessary, the resin
can be suitably stirred or heated. A washing temperature at which a
polyarylene sulfide resin is washed in an organic solvent is
preferably normal temperature to 150.degree. C. In this regard, the
polyarylene sulfide resin that has been washed with an organic
solvent is preferably washed with water or hot water several times
so that the residual organic solvent can be removed.
[0052] In cases where a polyarylene sulfide resin is washed with
hot-water, water to be used is preferably distilled water or
deionized water to express the effect of the favorable chemical
modification to be achieved by the polyarylene sulfide resin washed
with hot-water. Hot-water washing is usually carried out by adding
a predetermined amount of polyarylene sulfide resin to a
predetermined amount of water and heating the resulting mixture
with stirring at normal pressure or in a pressure container. A
ratio of a polyarylene sulfide resin to water is selected
preferably from bath ratios of 200 g or less of polyarylene sulfide
resin to 1 liter of water.
[0053] Examples of methods of acid-treating a polyarylene sulfide
resin include a method in which a polyarylene sulfide resin is
immersed in an acid or an acid aqueous solution. If necessary, the
resin can be suitably stirred or heated. Examples of acids include:
aliphatic saturated monocarboxylic acids such as formic acid,
acetic acid, propionic acid, and butyric acid; halo-substituted
aliphatic saturated carboxylic acids such as chloroacetic acid and
dichloroacetic acid; aliphatic unsaturated monocarboxylic acids
such as acrylic acid and crotonic acid; aromatic carboxylic acids
such as benzoic acid and salicylic acid; dicarboxylic acids such as
oxalic acid, malonic acid, succinic acid, phthalic acid, and
fumaric acid; and inorganic acidic compounds such as sulfuric acid,
phosphoric acid, hydrochloric acid, carbonic acid, and silic acid.
Among these acids, acetic acid or hydrochloric acid is preferably
used. The polyarylene sulfide resin that has been acid-treated is
preferably washed with water or hot water several times so that the
residual acid or salt can be removed. Water to be used for washing
is preferably distilled water or deionized water.
[0054] The polyarylene sulfide resin preferably has a melt
viscosity of 80 Pas or less, more preferably 20 Pas or less, under
the conditions: 310.degree. C. and a shear speed of 1000/second.
The melt viscosity is not limited to any particular lower limit,
but is preferably 5 Pas or more. Two or more polyarylene sulfide
resins having different melt viscosities may be used in
combination. The melt viscosity can be measured using a Capilograph
device (manufactured by Toyo Seiki Co. Ltd.) under the conditions:
a die length of 10 mm and a die hole diameter of 0.5 to 1.0 mm.
[0055] Examples of polyarylene sulfide resins that can be used
include commercially available products such as ones marketed under
the tradenames of "TORELINA" (registered trademark) manufactured by
Toray Industries, Inc., "DIC. PPS" (registered trademark)
manufactured by DIC Corporation, and "DURAFIDE" (registered
trademark) manufactured by Polyplastics Co., Ltd.
[0056] The thermoplastic resin (C) content of a molded article
according to the present invention is 20 to 94 parts by weight (20
parts by weight or more and 94 parts by weight or less) with
respect to 100 parts by weight of the total of the carbon fiber
(A), the organic fiber (B), and the thermoplastic resin (C). A
thermoplastic resin (C) content of less than 20 parts by weight
decreases the fiber dispersibility of the carbon fiber (A) and the
organic fiber (B) in a molded article and decreases the impact
strength. The thermoplastic resin (C) content is preferably 30
parts by weight or more. On the other hand, a thermoplastic resin
(C) content of more than 94 parts by weight results in making the
carbon fiber (A) content and the organic fiber (B) content relative
smaller, thus decreasing the reinforcement effect of the fibers and
decreasing the impact strength. The thermoplastic resin (C) content
is preferably 85 parts by weight or less, more preferably 75 parts
by weight or less.
[0057] <Organic Fiber (B)>
[0058] A molded article according to the present invention contains
an organic fiber (B) in addition to the above-mentioned carbon
fiber (A). A carbon fiber such as the carbon fiber (A) is rigid and
brittle, and thus, less easily entangled and more easily broken.
Because of this, there is a problem in that a fiber bundle composed
of only carbon fibers is easily broken in production of molded
articles, and easily falls off from a molded article. In view of
this, the organic fiber (B), which is flexible and less easily
broken, is contained in a molded article, and thus can
significantly enhance the impact strength of the molded
article.
[0059] The organic fiber (B) can suitably be selected to the extent
that the organic fiber (B) does not decrease the mechanical
properties of a molded article very much. Examples thereof include
fibers obtained by spinning the following: a polyolefin-based resin
such as polyethylene or polypropylene; a polyamide-based resin such
as nylon 6, nylon 66, aromatic polyamide, or aramid; a
polyester-based resin such as polyethylene terephthalate or
polybutylene terephthalate; a fluorine resin such as
polytetrafluoroethylene, a perfluoroethylene/propene copolymer, or
an ethylene/tetrafluoroethylene copolymer; a liquid crystal polymer
such as a liquid crystal polyester or liquid crystal polyester
amide; and a resin such as polyether ketone, polyether sulfone,
poly(paraphenylenebenzoxazole), a polyarylene sulfide such as
polyphenylene sulfide, and polyacrylonitrile. These may be used in
combination of two or more kinds thereof.
[0060] In the present invention, an organic fiber having a strand
strength of 1500 MPa or more is used. Use of an organic fiber
having a strand strength of less than 1500 MPa is more likely to
cause the organic fiber to be fractured in an impact test and is
less easily pulled out, and thus, the obtained molded article
results in having insufficient impact resistance.
[0061] The strand strength is more preferably 3000 MPa or more,
still more preferably 5000 MPa or more. The strand strength is
preferably less than 7000 MPa. A strand strength of more than 7000
MPa substantially does not cause fiber fracture even if the molded
article undergoes an impact, and thus, the molded article does not
result in achieving enhanced impact strength.
[0062] Among the above-mentioned organic fibers, examples of
organic fibers having a strand strength of 1500 MPa or more include
"fibers obtained by spinning the following: a polyamide-based resin
such as aromatic polyamide or aramid; a fluorine resin such as
polytetrafluoroethylene, a perfluoroethylene/propene copolymer, or
an ethylene/tetrafluoroethylene copolymer; a liquid crystal polymer
such as a liquid crystal polyester or liquid crystal polyester
amide; and a resin such as polyether ketone, polyether sulfone, or
poly(paraphenylenebenzoxazole)".
[0063] The organic fiber (B) preferably has a single fiber fineness
of 0.1 to 10 dtex.
[0064] In the present invention, the organic fiber (B) content of a
molded article is 1 to 45 parts by weight with respect to 100 parts
by weight of the total of the carbon fiber (A), the organic fiber
(B), and the thermoplastic resin (C). An organic fiber (B) content
of less than 1 part by weight decreases the impact strength of the
molded article. The organic fiber (B) content is preferably 3 parts
by weight or more, more preferably 5 parts by weight or more. On
the other hand, an organic fiber (B) content of more than 45 parts
by weight increases entanglement between fibers, decreases the
dispersibility of the organic fiber (B) in a molded article, and
more often decreases the impact strength of the molded article. The
organic fiber (B) content is preferably 20 parts by weight or less,
more preferably 10 parts by weight or less.
[0065] <Other Components>
[0066] A molded article according to the present invention may
contain (an)other component(s) in addition to the components (A) to
(C) to the extent that the objects of the present invention are not
impaired. Examples of the (an)other components include
thermosetting resins, inorganic fillers other than carbon fibers,
flame retardants, nucleating agents, ultraviolet absorbers,
antioxidants, vibration damping agents, antimicrobial agents,
insect repellents, deodorizers, color protection agents, heat
stabilizers, mold release agents, antistatic agents, plasticizers,
lubricant, coloring agents, pigments, dyes, foaming agents,
antifoaming agents, coupling agents, and the like. In addition, the
molded article may contain, for example, the below-mentioned
component (D) used for molding materials.
[0067] <L.sub.co/l.sub.no of Molded Article According to Present
Invention>
[0068] In a molded article according to the present invention, a
ratio (L.sub.co/l.sub.no) of the critical fiber length L.sub.co of
the organic fiber (B) to the number average fiber length l.sub.no
of the organic fiber (B) in the fiber reinforced thermoplastic
resin molded article is 0.9 or more and 2.0 or less. The ratio in
this range causes organic fiber pull-out to occur more
preferentially than organic fiber fracture and thus, makes it
possible to obtain a molded article which allows impact energy
absorption to be increased through the fiber pull-out, even when
the molded article undergoes an impact, and which thus achieves
high flexural strength and impact strength. A ratio
(L.sub.co/l.sub.no) of less than 0.9 causes the organic fiber
fracture to occur more preferentially, causes the pull-out less
easily, and thus, decreases the impact strength. The ratio is more
preferably 1.0 or more, still more preferably 1.1 or more. L.sub.co
is small, and thus, a ratio (L.sub.co/l.sub.no) of more than 2.0
causes the adhesion between the organic fiber (B) and the
thermoplastic resin (C) to be insufficient, decreasing the flexural
strength of the molded article. Alternatively, the fiber length
l.sub.no of the organic fiber becomes smaller, decreasing the
impact strength. The ratio is more preferably 1.4 or less, still
more preferably 1.2 or less.
[0069] Examples of means for adjusting L.sub.co/l.sub.no in the
above-mentioned range include a means by which L.sub.co and
l.sub.no are adjusted as above-mentioned. A detailed description
follows below.
[0070] Critical Fiber Length L.sub.c
[0071] Here, a critical fiber length refers to the smallest fiber
length that allows fracture to occur at the interface between fiber
and matrix resin, and in theory, fiber fracture does not occur with
a fiber length smaller than the critical fiber length. Hereinafter,
L.sub.cc is the critical fiber length of the carbon fiber (A), and
L.sub.co is the critical fiber length of the organic fiber (B).
[0072] The carbon fiber (A) preferably has a critical fiber length
L.sub.cc of 2500 .mu.m or less. The critical fiber length of 2500
.mu.m or less allows the carbon fiber (A) and the thermoplastic
resin (C) to have sufficient adhesion therebetween, enhancing the
flexural strength of a molded article, and thus, is preferable. The
critical fiber length is more preferably 1500 .mu.m or less. The
carbon fiber (A) having a critical fiber length L.sub.cc of 500
.mu.m or more enhances the impact strength of the molded article,
and thus, is preferable.
[0073] The organic fiber (B) preferably has a critical fiber length
Lm of 3000 .mu.m or more. The critical fiber length of 3000 .mu.m
or more is more likely to cause fiber pull-out than fiber fracture
in an impact test, enhancing the impact strength of the molded
article, and thus, is preferable. The organic fiber (B) more
preferably has a critical fiber length L.sub.co of 5000 .mu.m or
more, still more preferably 7000 .mu.m or more. The organic fiber
(B) having a critical fiber length L.sub.co of 15000 .mu.m or less
enhances the flexural strength of the molded article, and thus, is
preferable.
[0074] In the present invention, a ratio (L.sub.cc/L.sub.co) of the
critical fiber length L.sub.cc of the carbon fiber (A) to the
critical fiber length L.sub.co of the organic fiber (B) is
preferably 0.1 or more and 0.4 or less. A ratio (L.sub.cc/L.sub.co)
of 0.1 or more enhances the flexural strength of the molded
article, and thus, is preferable. The ratio is more preferably 0.3
or more. A ratio (L.sub.cc/L.sub.co) of 0.4 or less enhances the
impact strength, and thus, is preferable. As below-mentioned, the
critical fiber length varies with the shear strength (i) at the
interface between fiber and matrix resin, and thus, to determine
the ratio L.sub.cc/L.sub.co, the carbon fiber and the organic fiber
are measured for interfacial shear strength preferably using the
same matrix resin.
[0075] Next, a method of calculating a critical fiber length
L.sub.c will be described. If a shearing stress at the interface is
constant along a fiber length, the critical fiber length L.sub.c is
represented by the following equation.
L.sub.c=(Gf.times.df)/2.tau.
[0076] Here, .tau., .sigma.f, and, df represent an interfacial
shear strength, a single fiber strength, and a fiber diameter
respectively at the interface between fiber and matrix resin. These
will be described below in detail.
[0077] .tau.: shear strength at the interface between fiber and
matrix resin
[0078] An interfacial shear strength .tau. represents an
interfacial shear strength at the interface between fiber surface
and matrix resin, and can be measured by the following method. It
should be noted that an interfacial shear strength obtained using a
fiber coated with a surface treatment agent refers to a shear
strength at the interface between the surface of a fiber containing
the surface treatment agent and a matrix resin.
[0079] First, a thermoplastic resin is heated on a heater, and a
single fiber is brought down into the resin from above and embedded
in the resin in such a manner that the fiber forms a straight line.
Here, the depth at which the fiber is embedded in the direction of
the straight line is defined as H. The resin having the single
fiber embedded therein is cooled to normal temperature, and then,
that end of the fiber which is not embedded in the resin is fixed
on a pull-out tester. The end is pulled at a speed of 0.1 to 100
m/second in the straight line direction of the fiber and in the
direction allowing the fiber to be pulled out. Thus, the maximum
load value F is determined.
[0080] Using the following equation, F is divided by an embedded
depth H and a fiber perimeter (.pi.df), so that an interfacial
shear strength .tau. can be determined.
.tau.=F/(.pi.dfH)
[0081] Here, a represents the circumference ratio, and a fiber
diameter df (hereinafter, may be referred to as a single fiber
diameter) can be calculated using the average of three or more
fiber diameters randomly selected from the fibers observed using an
optical microscope (at 200 to 1000.times.), wherein the fibers are
yet to be subjected to pull-out measurement.
[0082] For a molded article composed of two or more fibers, the
following equation can be used for calculation after the values Lc
and .tau. of each of the fiber components are determined.
L.sub.c=L.sub.c1w.sub.1+L.sub.c2w.sub.2+L.sub.c3w.sub.3
.tau.=.tau..sub.1w.sub.1+.tau..sub.2w.sub.2+.tau..sub.3w.sub.3
[0083] Here, L.sub.c1, L.sub.c2, and L.sub.c3 . . . are the L.sub.c
of a first component, the L.sub.c of a second component, and the
L.sub.c of a third component respectively, and w.sub.1, w.sub.2,
and w.sub.3 are the fiber weight ratio of the first component, the
fiber weight ratio of the second component, and the fiber weight
ratio of the third component respectively, assuming that the weight
of the entire fiber in a molded article is 1.
[0084] .sigma.f: single fiber strength of fiber
[0085] The single fiber strength is a strength per unit
cross-sectional area of the single fiber, and is a value obtained
by dividing the single fiber tenacity by the cross-sectional area
of the fiber. In this regard, a strand strength is a value obtained
by dividing the tenacity of a strand by the cross-sectional area of
the fiber contained in the strand, and thus, in the present
invention, the strand strength can be used as a single fiber
strength Gf in the above-mentioned equation.
[0086] The strand strength can be determined in accordance with the
resin-impregnated strand testing method described in JIS-R-7608
(2004). In formulation of a resin, CELLOXIDE (registered trademark)
2021P (manufactured by Daicel Corporation), boron trifluoride
monoethyl amine (manufactured by Tokyo Chemical Industry Co.,
Ltd.), and acetone are used at a ratio of 100:3:4 (parts by
weight), and the curing conditions: 130.degree. C. and 30 minutes
are used. In this regard, the fiber cross-sectional area can be
calculated using the below-mentioned df (fiber diameter).
[0087] df: fiber diameter
[0088] As above-mentioned, the fiber diameter df can be calculated
using the average of three or more fiber diameters randomly
selected from the fibers observed using an optical microscope (at
200 to 1000.times.).
[0089] Method of adjusting L.sub.c
[0090] As above-mentioned, the critical fiber length (L.sub.c) can
be determined using (.sigma.f.times.df)/2.tau., and thus, adjusting
the interfacial shear strength (.tau.), the single fiber fiber
strength (.sigma.f), and the fiber diameter (df) makes it possible
to adjust the critical fiber length (L.sub.c). These will be
described below.
[0091] Interfacial Shear Strength
[0092] In the present invention, the organic fiber (B) has an
interfacial shear strength of 3.0 MPa or more and 50 MPa or less.
An interfacial shear strength of less than 3.0 MPa decreases
adhesion between the matrix resin and the organic fiber (B), and
thus, decreases the flexural strength of the molded article. The
interfacial shear strength is more preferably 3.3 MPa or more,
still more preferably 4.0 MPa or more. The interfacial shear
strength is still more preferably 5.0 MPa or more. An interfacial
shear strength of more than 50 MPa decreases Le, and thus, lowers
the impact strength of the molded article. The interfacial shear
strength is preferably 30 MPa or less, more preferably 10 MPa or
less, still more preferably 6 MPa or less.
[0093] The interfacial shear strength at the interface between
fiber and matrix resin can be measured by the above-mentioned
method. Examples of methods of adjusting an interfacial shear
strength include adjusting the amount and kind of a surface
treatment agent to be adhered to the surface of a fiber.
[0094] A surface treatment agent (what is called a sizing agent)
that can be used for the carbon fiber is as above-mentioned.
Examples of surface treatment agents for the organic fiber are
below-mentioned. In this regard, those enumerated below as examples
of surface treatment agents for the organic fiber can be used as
surface treatment agents for the carbon fiber, and surface
treatment agents used for the carbon fiber and surface treatment
agents used for the organic fiber may be the same or different.
[0095] For example, a modifier such as an epoxy resin, phenol
resin, polyethylene glycol, or polyurethane is used as a surface
treatment agent for the organic fiber so that the interfacial shear
strength can be enhanced and so that the flexural strength can be
enhanced. Among these, an epoxy resin that has excellent
wettability against the organic fiber (B) is preferable, and a
multi-functional epoxy resin is more preferable.
[0096] Examples of multi-functional epoxy resins include bisphenol
A epoxy resins, bisphenol F epoxy resins, aliphatic epoxy resins,
phenol novolac epoxy resins, and the like. Among these, aliphatic
epoxy resins that are more likely to exhibit adhesion to the
thermoplastic resin (C) are preferable. Aliphatic epoxy resins have
a flexible backbone and thus are more likely to have a structure
having high toughness although having a high cross-linking density.
In addition, an aliphatic epoxy resin that may be allowed to be
present between the fiber and the thermoplastic resin is flexible
and makes it difficult for both to peel apart, and thus, can
further enhance the strength of the molded article.
[0097] Examples of multi-functional aliphatic epoxy resins include
diglycidyl ether compounds, polyglycidyl ether compounds, and the
like. Examples of diglycidyl ether compounds include ethylene
glycol diglycidyl ethers, polyethylene glycol diglycidyl ethers,
propylene glycol diglycidyl ethers, polypropylene glycol diglycidyl
ethers, 1,4-butanediol diglycidyl ethers, neopentyl glycol
diglycidyl ethers, polytetramethylene glycol diglycidyl ethers,
polyalkylene glycol diglycidyl ethers, and the like. In addition,
examples of polyglycidyl ether compounds include glycerol
polyglycidyl ethers, diglycerol polyglycidyl ethers, polyglycerol
polyglycidyl ethers, sorbitol polyglycidyl ethers, arabitol
polyglycidyl ethers, trimethylolpropane polyglycidyl ethers,
trimethylolpropane glycidyl ethers, pentaerythritol polyglycidyl
ethers, polyglycidyl ethers of aliphatic multivalent alcohols, and
the like.
[0098] Among the above-mentioned aliphatic epoxy resins,
ti-functional or more-multi-functional aliphatic epoxy resins are
preferable, and aliphatic polyglycidyl ether compounds having three
or more glycidyl groups having high reactivity are more preferable.
Aliphatic polyglycidyl ether compounds exhibit a good balance among
flexibility, cross-linking density, and compatibility with the
thermoplastic resin (C), and can enhance the adhesion. Among these,
glycerol polyglycidyl ethers, diglycerol polyglycidyl ethers,
polyglycerol polyglycidyl ethers, polyethylene glycol glycidyl
ethers, and polypropylene glycol glycidyl ethers are still more
preferable.
[0099] Use of a modifier such as a silicon oil solution makes it
possible to increase L.sub.c and enhance the impact strength of the
molded article.
[0100] In addition, a polyester, an emulsifier, or a surfactant may
be used, and two or more of these may be used. The surface
treatment agent is preferably water-soluble or
water-dispersible.
[0101] The amount of the above-mentioned surface treatment agent to
be adhered is preferably 0.1 parts by weight or more, 5.0 parts by
weight or less, with respect to 100 parts by weight of the organic
fiber. An amount of 0.1 parts by weight or more enhances the
dispersibility of the organic fiber in a molded article, and thus,
enhances the impact strength and flexural strength. The amount is
preferably 0.3 parts by weight or more, more preferably 0.5 parts
by weight or more. Such a surface treatment agent inhibits the
dispersion of the organic fiber if excessively adhered to the
organic fiber, and thus, an amount of 5.0 parts by weight or less
enhances the dispersibility of the organic fiber in a molded
article, and thus, enhances the flexural strength. The amount is
preferably 3.0 parts by weight or less, more preferably 1.5 parts
by weight or less.
[0102] In this regard, the carbon fiber (A) preferably has an
interfacial shear strength of 5 MPa or more. An interfacial shear
strength of 5 MPa or more allows the carbon fiber (A) and the
thermoplastic resin (C) to have high adhesion therebetween,
enhancing the flexural strength of the molded article. The
interfacial shear strength is more preferably 6 MPa or more, still
more preferably 10 MPa or more. The carbon fiber (A) having an
interfacial shear strength of 50 MPa or less enhances the impact
strength of the molded article, and thus, is preferable. The
interfacial shear strength is more preferably 30 MPa or less.
[0103] The method of measuring the interfacial shear strength of
the organic fiber (B) can be used as a method of measuring the
interfacial shear strength of the carbon fiber (A). Examples of
methods of adjusting the interfacial shear strength of the carbon
fiber (A) include adjusting the amount and kind of a sizing
agent.
[0104] In addition, the interfacial shear strength is an index of
adhesive strength at the interface between fiber and matrix resin,
and thus, can be adjusted according to the degree of modification
of the matrix resin and the selection of an organic fiber in
accordance with the degree of modification.
[0105] For a less adhesive fiber such as an aramid fiber or a
poly(paraphenylenebenzoxazole) fiber, a more adhesive resin such as
a polyolefin resin, a polyamide resin, a polyester resin, or a
polycarbonate resin is preferable from the viewpoint of enhancing
the impact strength and flexural strength and used to enhance the
flexural strength of the molded article. Among these, a
polypropylene resin and/or a polyester resin are preferable. Among
polyolefin resins, particularly a polypropylene resin used as a
matrix resin may be an unmodified polypropylene or a modified
polypropylene, and an unmodified polypropylene and a modified
polypropylene resin are preferably used in combination to enhance
the interfacial shear strength. In particular, with a less adhesive
fiber such as an aramid fiber or a poly(paraphenylenebenzoxazole)
fiber, an unmodified polypropylene resin and a modified
polypropylene resin are preferably used at a weight ratio of 99:1
to 90:10 to enhance the interfacial shear strength. The weight
ratio is more preferably 97:3 to 95:5, still more preferably 97:3
to 96:4.
[0106] For a more adhesive fiber such as a liquid crystal polyester
(LCP) fiber, a less adhesive resin such as a polyolefin resin,
polystyrene resin, polyarylsulfone resin, polyaryl ketone resin,
polyarylene ether resin, polyarylene sulfide resin, polyaryl ether
ketone resin, polyether sulfone resin, or polyarylene sulfide
sulfone resin is preferable from the viewpoint of enhancing the
impact strength and flexural strength. Among these, a polyolefin
resin and/or a polyarylene sulfide resin are preferable. Among
polyolefin resins, particularly a polypropylene resin used as a
matrix resin may be an unmodified polypropylene or a modified
polypropylene, and an unmodified polypropylene and a modified
polypropylene resin are preferably used in combination to enhance
the interfacial shear strength. More specifically, an unmodified
polypropylene resin and a modified polypropylene resin are
preferably used at a weight ratio of 100:0 to 97:3. The weight
ratio is more preferably 100:0 to 99:1 from the viewpoint of a
balance between impact strength and flexural strength.
[0107] Single fiber strength, fiber diameter, and single fiber
tenacity
[0108] The single fiber strength is a strength per unit
cross-sectional area of the single fiber, is a value obtained by
dividing the single fiber tenacity by the cross-sectional area of
the fiber, and depends on the fiber type.
[0109] In the present invention, the organic fiber (B) has a single
fiber tenacity of 50 cN or more. The organic fiber (B) having a
single fiber tenacity of less than 50 cN causes the ratio
(L.sub.co/l.sub.no) to be smaller, is less likely to cause fiber
pull-out than fiber fracture in an impact test, and less likely to
enhance the impact strength. The single fiber tenacity is more
preferably 70 cN or more, still more preferably 120 cN or more.
Although there is no particular upper limit, the single fiber
tenacity is preferably 250 cN or less.
[0110] A fiber that satisfies a single fiber tenacity of 50 cN or
more is preferably at least one selected from the group consisting
of liquid crystalline polyester fibers, aramid fibers, and
poly(paraphenylenebenzoxazole) fibers.
[0111] In the present invention, a liquid crystal polyester fiber
mentioned as an example of an organic fiber having a strand
strength of 1500 MPa or more preferably has a fiber diameter of 6
.mu.m or more and 1000 .mu.m or less. The fiber diameter of 6 .mu.m
or more increases the critical fiber length L.sub.co, enhances the
impact strength, and thus, is preferable. The fiber diameter is
more preferably 10 .mu.m or more. The fiber diameter of 1000 .mu.m
or less enhances the flowability during molding, makes the
moldability better, and thus, is preferable.
[0112] About l.sub.n
[0113] Here, the "number average fiber length (l.sub.n)" in the
present invention refers to an average fiber length calculated
using the following equation, wherein a method of calculating a
number average molecular weight is applied to the calculation of a
fiber length. However, the following equation applies in a case
where the fiber diameters and densities of the carbon fiber (A) and
the organic fiber (B) are constant.
Number average fiber length=.SIGMA.X(Mi)/(N)
Mi: fiber length (mm) N: number of fibers
[0114] The number average fiber length can be measured by the
following method. An ISO type of dumbbell specimen is sandwiched
between glass plates, heated on a hot stage set to 200 to
300.degree. C., and uniformly dispersed in film form. The film
having the fiber uniformly dispersed therein is observed using an
optical microscope (at 50 to 200.times.). Randomly selected 1000
carbon fibers (A) and organic fibers (B) are measured for fiber
length to calculate the number average fiber length of the carbon
fibers (A) and the number average fiber length of the organic
fibers (B) using the above-mentioned equation.
[0115] In the present invention, the carbon fiber (A) preferably
has a number average fiber length l.sub.n, of 100 m or more. The
number average fiber length of 100 .mu.m or more enhances the
elastic modulus of the molded article, enhances the flexural
strength, and thus, is preferable. The number average fiber length
is more preferably 200 .mu.m or more, still more preferably 500
.mu.m or more. Although having no particular lower limit, the
number average fiber length at 50 .mu.m or less has the possibility
of saturating the flexural strength.
[0116] In the present invention, the organic fiber (B) preferably
has a number average fiber length l.sub.no of 2000 .mu.m or more
and 15000 .mu.m or less. A number average fiber length of 2000
.mu.m or more enhances the ratio (L.sub.co/l.sub.no), enhances the
impact strength, and thus, is preferable. The number average fiber
length is more preferably 3000 .mu.m or more, still more preferably
5000 .mu.m or more, yet more preferably 6000 .mu.m or more. The
number average fiber length of 15000 .mu.m or less enhances the
flowability during molding, makes the moldability better,
additionally enhances the impact strength, and thus, is
preferable.
[0117] In this regard, the number average fiber lengths of the
carbon fiber (A) and organic fiber (B) in a molded article can be
adjusted, for example, with molding conditions, the length of a
molding material, and the like. In injection molding, examples of
such molding conditions include pressure conditions such as back
pressure and dwelling pressure, time conditions such as injection
time and dwell time, temperature conditions such as cylinder
temperature and mold temperature, and the like. Specifically,
increasing the pressure conditions such as back pressure makes it
possible to increase a shear force in the cylinder, and thus, to
shorten the number average fiber lengths of the carbon fiber (A)
and organic fiber (B). In addition, shortening the injection time
makes it possible to increase a shear force during injection, and
thus, to shorten the number average fiber lengths of the carbon
fiber (A) and organic fiber (B). Furthermore, decreasing the
temperature such as cylinder temperature and mold temperature makes
it possible to increase the viscosity of a flowing resin, enhance
the shear force, and thus, to shorten the number average fiber
lengths of the carbon fiber (A) and organic fiber (B). Specific
examples of preferable injection molding conditions include, but
are not limited particularly to: an injection time of 0.5 seconds
to 10 seconds, more preferably 2 seconds to 10 seconds; aback
pressure of 0.1 MPa to 10 MPa, more preferably 2 MPa to 8 MPa; a
dwelling pressure of 1 MPa to 50 MPa, more preferably 1 MPa to 30
MPa; a dwell time of 1 second to 20 seconds, more preferably 5
seconds to 20 seconds; a cylinder temperature of 200.degree. C. to
320.degree. C.; and a mold temperature of 20.degree. C. to
100.degree. C. Here, cylinder temperature refers to the temperature
of that portion of an injection molding machine which melts a
molding material by heating, and mold temperature refers to the
temperature of a mold into which a resin is injected to be formed
in predetermined form. Suitably selecting these conditions,
particularly injection time, back pressure, and mold temperature,
makes it possible to easily adjust the fiber lengths of the carbon
fiber and organic fiber in a molded article.
[0118] In cases where a long molding material is used to obtain a
molded article, the carbon fiber and organic fiber remaining in the
molded article have a long fiber length with the result that the
carbon fiber (A) and organic fiber (B) in the molded article have a
long number average fiber length.
[0119] The molding material preferably has a length of 3 mm or more
and 30 mm or less. The length of 3 mm or more causes the carbon
fiber (A) and organic fiber (B) remaining in the molded article to
have a long fiber length, enhances the impact strength, and thus,
is preferable. The length is more preferably 7 mm or more. The
length of 30 mm or less causes the carbon fiber (A) and organic
fiber (B) to have a good dispersibility during molding, enhances
the impact strength, and thus, is preferable.
[0120] In the present invention, changing the conditions suitably
as above-mentioned enables the carbon fiber (A) and organic fiber
(B) in a molded article to have a number average fiber length in a
desired range.
[0121] To obtain a molded article in the present invention, for
example, the following molding material can be used.
[0122] In this regard, a "molding material" in the present
invention means a raw material used in forming a molded article by
injection molding and the like.
[0123] A molding material in the present invention may contain a
component (D) in addition to the carbon fiber (A), the organic
fiber (B), and thermoplastic resin (C) to impart good fiber
dispersion in a molded article. For the carbon fiber (A), the
organic fiber (B), and thermoplastic resin (C) in the molding
material, the above-mentioned materials can be used.
[0124] The component (D) often has a low molecular weight, and is
often a solid or a liquid that is usually relatively brittle and
more breakable at normal temperature. The component (D) has a low
molecular weight, thus has high flowability, and enables the carbon
fiber (A) and the organic fiber (B) to enhance the effect of
dispersing into the thermoplastic resin (C). Examples of the
component (D) include epoxy resins, phenol resins, terpene resins,
cyclic polyarylene sulfide resins, and the like. The component (D)
may contain two or more kinds of these. The component (D)
preferably has a high affinity for the thermoplastic resin (C).
Selecting a component (D) having a high affinity for the
thermoplastic resin (C) allows the component (D) to be efficiently
compatible with the thermoplastic resin (C) during production of a
molding material and during molding, and thus, makes it possible to
further enhance the dispersibility of the carbon fiber (A) and the
organic fiber (B).
[0125] The component (D) is selected suitably according to
combination with the thermoplastic resin (C). For example, a
molding temperature range of from 150.degree. C. to 270.degree. C.
allows a terpene resin to be used suitably. A molding temperature
range of from 270.degree. C. to 320.degree. C. allows an epoxy
resin, a phenol resin, and a cyclic polyarylene sulfide resin to be
used suitably. Specifically, in cases where the thermoplastic resin
(C) is a polypropylene resin, the component (D) is preferably a
terpene resin. In cases where the thermoplastic resin (C) is a
polycarbonate resin or a polyarylene sulfide resin, the component
(D) is preferably an epoxy resin, a phenol resin, or a cyclic
polyarylene sulfide resin. In cases where the thermoplastic resin
(C) is a polyamide resin or a polyester resin, the component (D) is
preferably a terpene phenol resin.
[0126] The component (D) preferably has a melt viscosity of 0.01 to
10 Pas at 200.degree. C. The melt viscosity of 0.01 Pas or more at
200.degree. C. makes it possible to prevent the component (D) from
agglomerating in the carbon fiber (A) and the organic fiber (B)
impregnated with the component (D), and to adhere the component (D)
to the fibers uniformly. Accordingly, this melt viscosity makes it
possible to further enhance the dispersibility of the carbon fiber
(A) and the organic fiber (B) in molding a molding material
according to the present invention. The melt viscosity is more
preferably 0.05 Pas or more, still more preferably 0.1 Pas or more.
On the other hand, the melt viscosity of 10 Pas or less at
200.degree. C. causes the component (D) to have a higher
impregnation speed, and thus, the melt viscosity is preferably 5
Pas or less, more preferably 2 Pas or less, so that the component
(D) can be adhered uniformly to the carbon fiber (A) and the
organic fiber (B). Here, the melt viscosity of each of
thermoplastic resin (C) and the component (D) at 200.degree. C. can
be measured using a viscoelasticity measurement device with a 40 mm
parallel plate at 0.5 Hz.
[0127] In production of a molding material according to the present
invention, it is preferable to adhere the component (D) to the
carbon fiber (A) and the organic fiber (B) to first obtain a
composite fiber bundle (E) as below-mentioned, and a melting
temperature (a temperature in a melting bath) in supplying the
component (D) is preferably 100 to 300.degree. C. In view of this,
the melt viscosity of the component (D) at 200.degree. C. has been
noticed as an index for the impregnating property of the component
(D) in the carbon fiber (A) and the organic fiber (B). A
200.degree. C. melt viscosity in the above-mentioned preferable
range allows the component (D) to have an excellent impregnating
property in the carbon fiber (A) and the organic fiber (B) in such
a preferable melting temperature range, and thus, makes it possible
to enhance the dispersibility of the carbon fiber (A) and organic
fiber (B) in a molded article and to enhance the mechanical
properties, particularly impact strength, of the molded
article.
[0128] The component (D) preferably has a number average molecular
weight of 200 to 50,000. The number average molecular weight of 200
or more makes it possible to enhance the mechanical properties,
particularly impact strength, of the molded article. The number
average molecular weight is more preferably 1,000 or more. In
addition, the number average molecular weight of 50,000 or less
allows the component (D) to have a suitably low viscosity and thus
to have an excellent impregnating property in the carbon fiber (A)
and the organic fiber (B) contained in a molded article, and makes
it possible to further enhance the dispersibility of the carbon
fiber (A) and organic fiber (B) in the molded article. The number
average molecular weight is more preferably 3,000 or less. In this
regard, the number average molecular weight of such a compound can
be measured by gel permeation chromatography (GPC).
[0129] The component (D) preferably undergoes a loss of 5 wt % or
less when heated at 10.degree. C./minute (in air) in molding
temperature. The loss on heating is more preferably 3 wt % or less.
Such a loss of 5 wt % or less on heating makes it possible to
suppress generation of decomposition gas when the carbon fiber (A)
and the organic fiber (B) are impregnated with the component (D),
and to suppress generation of voids in molding. In addition, the
generation of gas can be suppressed particularly in molding at high
temperature.
[0130] In this regard, a loss on heating in the present invention
refers to a weight loss rate of the weight that the component (D)
has before heating to the weight after heating under the
above-mentioned heating conditions, assuming that the weight that
the component (D) has before heating is 100%. Then, the loss on
heating can be determined using the following equation. The weights
before and after heating can be determined by measuring the weights
at molding temperature by thermogravimetric analysis (TGA) using a
platinum sample pan under the condition: a heating speed of
10.degree. C./minute under an air atmosphere.
Loss on heating [wt %]={(weight before heating-weight after
heating)/weight before heating}.times.100.
[0131] In addition, the component (D) preferably has a melt
viscosity variation rate of 2% or less after heating at 200.degree.
C. for two hours. Even in producing a composite fiber bundle (E)
for many hours, allowing the melt viscosity variation rate to be 2%
or less makes it possible to suppress the adhesion nonuniformity
and the like and produce the composite fiber bundle (E) stably. The
melt viscosity variation rate is more preferably 1.5% or less,
still more preferably 1.3% or less.
[0132] Here, the melt viscosity variation rate of the component (D)
can be determined by the following method. First, the melt
viscosity at 200.degree. C. is measured using a viscoelasticity
measurement device with a40 mm parallel plate at 0.5 Hz. Then, the
component (D) is left to stand in a hot air dryer at 200.degree. C.
for two hours, followed by measuring the melt viscosity at
200.degree. C. in the same manner, and the viscosity variation rate
is calculated using the following equation.
Melt viscosity variation rate [%]={(melt viscosity at 200.degree.
C. before heating at 200.degree. C. for two hours-melt viscosity at
200.degree. C. after heating at 200.degree. C. for two hours)/(melt
viscosity at 200.degree. C. before heating at 200.degree. C. for
two hours)}.times.100.
[0133] In the present invention, an epoxy resin preferably used as
the component (D) refers to a compound which has two or more epoxy
groups and which contains substantially no curing agent and is not
cured by what is called three-dimensional cross-linking even if
heated. An epoxy resin has an epoxy group, and thus, interacts with
the carbon fiber (A) and the organic fiber (B) easily. Because of
this, an epoxy resin is well suited for the carbon fiber (A) and
the organic fiber (B) which form the composite fiber bundle (E)
during impregnation. In addition, an epoxy resin further enhances
the dispersibility of the carbon fiber (A) and the organic fiber
(B) during molding.
[0134] Here, examples of epoxy resins to be preferably used as the
component (D) include glycidyl ether epoxy resins, glycidyl ester
epoxy resins, glycidyl amine epoxy resins, and alicyclic epoxy
resins. These may be used in combination of two or more kinds
thereof.
[0135] Examples of glycidyl ether epoxy resins include bisphenol A
epoxy resins, bisphenol F epoxy resins, bisphenol AD epoxy resins,
halogenated bisphenol A epoxy resins, bisphenol S epoxy resins,
resorcinol epoxy resins, hydrogenated bisphenol A epoxy resins,
phenol novolac epoxy resins, cresol novolac epoxy resins, aliphatic
epoxy resins having an ether bond, naphthalene epoxy resins,
biphenyl epoxy resins, biphenylaralkyl epoxy resins,
dicyclopentadiene epoxy resins, and the like.
[0136] Examples of glycidyl ester epoxy resins include
hexahydrophthalic acid glycidyl esters, dimer acid diglycidyl
esters, and the like.
[0137] Examples of glycidyl amine epoxy resins include triglycidyl
isocyanurate, tetraglycidyl diaminodiphenylmethane, tetraglycidyl
metaxylenediamine, aminophenol epoxy resins, and the like.
[0138] Examples of alicyclic epoxy resins include
3,4-epoxy-6-methylcyclohexylmethyl carboxylate,
3,4-epoxycyclohexylmethyl carboxylate, and the like.
[0139] Among these, glycidyl ether epoxy resins have an excellent
balance between viscosity and heat resistance, and thus, is
preferable. Bisphenol A epoxy resins and bisphenol F epoxy resins
are more preferable.
[0140] In addition, an epoxy resin to be used as the component (D)
preferably has a number average molecular weight of 200 to 5000. An
epoxy resin having a number average molecular weight of 200 or more
makes it possible to enhance the mechanical properties of the
molded article further. The number average molecular weight is more
preferably 800 or more, still more preferably 1000 or more. On the
other hand, an epoxy resin having a number average molecular weight
of 5000 or less allows the resin to have an excellent impregnating
property for the carbon fiber (A) and the organic fiber (B)
constituting the composite fiber bundle (E), and makes it possible
to further enhance the dispersibility of the carbon fiber (A) and
organic fiber (B) in a molded article. The number average molecular
weight is more preferably 4000 or less, still more preferably 3000
or less. In this regard, the number average molecular weight of an
epoxy resin can be measured by gel permeation chromatography
(GPC).
[0141] In addition, examples of terpene resins include polymers or
copolymers obtained by polymerizing a terpene monomer with an
aromatic monomer and the like, if necessary, in the presence of a
Friedel-Crafts catalyst in an organic solvent.
[0142] Examples of terpene monomers include .alpha.-pinene,
.beta.-pinene, dipentene, d-limonene, myrcene, allo-ocimene,
ocimene, .alpha.-phellandrene, .alpha.-terpinene,
.gamma.-terpinene, terpinolene, 1,8-cineol, 1,4-cineol,
.alpha.-terpineol, .beta.-terpineol, .gamma.-terpineol, sabinene,
para-menthadienes, carenes, and the like. In addition, examples of
aromatic monomers include styrene, .alpha.-methylstyrene, and the
like. Among these, .alpha.-pinene, .beta.-pinene, dipentene, and
d-limonene have excellent compatibility with the thermoplastic
resin (C) and thus, are preferable. Furthermore, homopolymers of
these terpene monomers are more preferable.
[0143] It is also possible to use hydrogenated terpene resins
obtained by hydrogenation of these terpene resins and use terpene
phenol resins obtained by allowing a terpene monomer to react with
a phenol in the presence of a catalyst. Here, phenols that are
preferably used have, on the benzene ring of the phenol, one to
three substituents of at least one kind selected from the group
consisting of alkyl groups, halogen atoms, and a hydroxyl group.
Specific examples thereof include cresol, xylenol, ethylphenol,
butylphenol, t-butylphenol, nonylphenol, 3,4,5-trimethylphenol,
chlorophenol, bromophenol, chlorocresol, hydroquinone, resorcinol,
orcinol, and the like. These may be used in combination of two or
more kinds thereof. Among these, phenols and cresols are
preferable. Among these, hydrogenated terpene resins have excellent
compatibility with the thermoplastic resin (C), particularly a
polypropylene resin, and thus, are preferable.
[0144] In addition, the glass transition temperature of a terpene
resin is not limited to any particular value, but is preferably 30
to 100.degree. C. The glass transition temperature of 30.degree. C.
or more allows the component (D) to have excellent handling
properties during molding. In addition, the glass transition
temperature of 100.degree. C. or less makes it possible to suitably
suppress the flowability of the component (D) during molding and
enhance the moldability.
[0145] In addition, a terpene resin used as the component (D)
preferably has a number average molecular weight of 200 to 5000.
The number average molecular weight of 200 or more makes it
possible to enhance the mechanical properties, particularly impact
strength, of the molded article. In addition, the number average
molecular weight of 5000 or less allows a terpene resin to have a
suitably low viscosity and thus to have an excellent impregnating
property for the carbon fiber (A) and the organic fiber (B), and
makes it possible to further enhance the dispersibility of the
carbon fiber (A) and organic fiber (B) in the molded article. In
this regard, the number average molecular weight of a terpene resin
can be measured by gel permeation chromatography (GPC).
[0146] The component (D) content of a molding material according to
the present invention is preferably 1 to 20 parts by weight with
respect to 100 parts by weight of the total of the carbon fiber
(A), the organic fiber (B), the thermoplastic resin (C), and the
component (D). The component (D) content of 1 part by weight or
more further enhances the flowability of the carbon fiber (A) and
the organic fiber (B) in production of the molded article and
further enhances the dispersibility. The component (D) content is
preferably 2 parts by weight or more, preferably 4 parts by weight
or more, more preferably 7 parts by weight or more. On the other
hand, the component (D) content of 20 parts by weight or less makes
it possible to further enhance the flexural strength, tensile
strength, and impact strength of the molded article. The component
(D) content is preferably 15 parts by weight or less, more
preferably 12 parts by weight or less, still more preferably 10
parts by weight or less.
[0147] In a molding material according to the present invention,
the carbon fiber (A) and the organic fiber (B) are arranged
substantially in parallel in the axial direction, and the lengths
of the carbon fiber (A) and the organic fiber (B) are preferably
substantially the same as the length of the molding material.
Allowing the length of the fiber bundle to be substantially the
same as the length of the molding material makes it easier to
control the fiber lengths of the carbon fiber (A) and the organic
fiber (B) in a molded article produced using the molding material.
More specifically, varying the below-mentioned molding conditions
makes it possible to more easily control the fiber lengths of the
carbon fiber (A) and the organic fiber (B) in a molded article
produced using the molding material, and to obtain a molded article
having more excellent mechanical properties.
[0148] Subsequently, a method of producing a molding material
according to the present invention will be described. A molding
material according to the present invention can be obtained, for
example, by the following method.
[0149] First, a roving of the carbon fiber (A) and a roving of the
organic fiber (B) are doubled in parallel in the longitudinal
direction of the fibers to produce a fiber bundle having the carbon
fiber (A) and the organic fiber (B). Then, the fiber bundle is
impregnated with a melted component (D) to produce the composite
fiber bundle (E). Furthermore, the composite fiber bundle (E) is
introduced into an impregnation die filled with a melted
composition containing the thermoplastic resin (C) to coat the
external side of the composite fiber bundle (E) with the
composition containing the thermoplastic resin (C), and the
resulting material is pulled out through a nozzle. The material is
solidified by cooling and pelletized to a predetermined length to
obtain a molding material. This is an example of a method of
obtaining a molding material (an aspect I). The thermoplastic resin
(C) may be contained in the composite fiber bundle (E) through
impregnation as long as the resin is contained in at least the
external side of the fiber bundle.
[0150] In addition, the composite fiber bundle (E) produced by the
above-mentioned method may be pellet-blended with a molding
material having a coating of the composition containing the
thermoplastic resin (C) and with pellets containing the
thermoplastic resin (C) (pellets not containing the carbon fiber
(A) or the organic fiber (B)) to obtain a molding material mixture
(an aspect II). In this case, the carbon fiber (A) content and
organic fiber (B) content of a molded article can be easily
adjusted. In addition, a molding material obtained by coating the
carbon fiber (A) with a composition containing the thermoplastic
resin (C) may be pellet-blended with a molding material obtained by
coating the organic fiber (B) with a composition containing the
thermoplastic resin (C) to obtain a molding material mixture (an
aspect III). The carbon fiber (A) and/or the organic fiber (B)
are/is preferably impregnated with the component (D). It is more
preferable that the carbon fiber (A) is impregnated with the
component (D), and that the organic fiber (B) is impregnated with
the below-mentioned component (G). Here, pellet-blending is
different from melt-kneading and refers to allowing a plurality of
materials to be mixed by stirring at a temperature at which a resin
component is not melted and to become substantially uniform.
Pellet-blending is preferably used for a molding material in pellet
form mainly in injection molding, extrusion molding, and the
like.
[0151] A molding material mixture in the aspect III will be
described in further detail. To obtain a molding material mixture,
it is preferable that a carbon fiber reinforced thermoplastic resin
molding material (X) (referred to as a "carbon fiber reinforced
molding material (X)" in some cases) containing at least the
thermoplastic resin (C), the carbon fiber (A), and the component
(D) and an organic fiber reinforced thermoplastic resin molding
material (Y) (referred to as an "organic fiber reinforced molding
material (Y)" in some cases) containing at least a thermoplastic
resin (F), the organic fiber (B), and a component (G) (referred to
as a "component (G)" in some cases) are separately prepared, and
that these are pellet-blended. It is preferable that the carbon
fiber reinforced molding material (X) contains a composite fiber
bundle (H) obtained by impregnating the carbon fiber (A) with the
component (D), and has a structure in which the thermoplastic resin
(C) is contained in the external side of the composite fiber bundle
(H). The carbon fiber (A) preferably has substantially the same
length as the carbon fiber reinforced molding material. The carbon
fiber (A) is preferably arranged substantially in parallel in the
axial direction of the carbon fiber reinforced molding material
(X). The carbon fiber reinforced molding material (X) preferably
has a length of 3 mm or more, more preferably 7 mm or more. The
carbon fiber reinforced molding material (X) preferably has a
length of 30 mm or less. In addition, the organic fiber reinforced
molding material (Y) preferably contains a composite fiber bundle
(I) obtained by impregnating the organic fiber (B) with the
component (G), and has a structure in which the thermoplastic resin
(F) is contained in the external side of the composite fiber bundle
(I). The organic fiber (B) preferably has substantially the same
length as the organic fiber reinforced molding material. The
organic fiber (B) is preferably arranged substantially in parallel
in the axial direction of the organic fiber reinforced molding
material (Y). The organic fiber reinforced molding material (Y)
preferably has a length of 3 mm or more, more preferably 7 mm or
more. The carbon fiber reinforced molding material (Y) preferably
has a length of 30 mm or less. In this regard, the compounds
enumerated as the component (D) described above can be used as the
component (G), and the component (D) and the component (G) may be
the same compound or different compounds. The resins enumerated as
the thermoplastic resin (C) described above can be used as the
thermoplastic resin (F), and the thermoplastic resin (C) and the
thermoplastic resin (F) may be the same compound or different
compounds.
[0152] The carbon fiber reinforced molding material (X) preferably
contains 5 to 45 parts by weight of the carbon fiber (A), 10 to 94
parts by weight of the thermoplastic resin (C), and 1 to 20 parts
by weight of the component (D) with respect to 100 parts by weight
of the total of the carbon fiber (A), the thermoplastic resin (C),
and the component (D). The organic fiber reinforced molding
material (Y) preferably contains 1 to 45 parts by weight of the
organic fiber (B), 10 to 98 parts by weight of the thermoplastic
resin (F), and 1 to 20 parts by weight of the component (G) with
respect to 100 parts by weight of the total of the organic fiber
(B), the thermoplastic resin (F), and the component (G).
[0153] It is preferable to blend 50 to 80 parts by weight of the
carbon fiber reinforced molding material (X) and 20 to 50 parts by
weight of the organic fiber reinforced molding material (Y) with
respect to 100 parts by weight of the total of the carbon fiber
reinforced molding material (X) and the organic fiber reinforced
molding material (Y). That is, in cases where a pellet blend
(mixture) of the carbon fiber reinforced molding material (X) and
the organic fiber reinforced molding material (Y) is produced, such
a pellet blend is preferably prepared in such a manner that the
whole mixture contains 5 to 45 parts by weight of the carbon fiber
(A), 1 to 45 parts by weight of the organic fiber (B), 10 to 93
parts by weight of the thermoplastic resin (C), and 1 to 20 parts
by weight of the component (D) with respect to 100 parts by weight
of the total of the carbon fiber (A), the organic fiber (B), the
thermoplastic resin (C), and the component (D). In this regard,
such ratios are calculated, using, in place of the thermoplastic
resin (C), a thermoplastic resin to be used as the thermoplastic
resin (F), and using the component (G) in place of the component
(D) if the component (G) is used as a component corresponding to
the component (D).
[0154] Next, a method of producing a molded article according to
the present invention will be described. Using the above-mentioned
molding material according to the present invention for molding
makes it possible to obtain a molded article having excellent
dispersibility of the carbon fiber (A) and the organic fiber (B)
and excellent flexural strength and impact strength. Preferable
examples of molding methods include a molding method carried out
using a mold, and various molding methods such as injection
molding, extrusion molding, and press molding can be used. In
particular, molding methods carried out using an injection molding
machine make it possible to obtain molded articles continuously and
stably. Examples of preferable injection molding conditions
include, but are not limited particularly to: an injection time of
0.5 seconds to 10 seconds, more preferably 2 seconds to 10 seconds;
a back pressure of 0.1 MPa to 10 MPa, more preferably 2 MPa to 8
MPa; a dwelling pressure of 1 MPa to 50 MPa, more preferably 1 MPa
to 30 MPa; a dwell time of 1 second to 20 seconds, more preferably
5 seconds to 20 seconds; a cylinder temperature of 200.degree. C.
to 320.degree. C.; and a mold temperature of 20.degree. C. to
100.degree. C. Here, cylinder temperature refers to the temperature
of that portion of an injection molding machine which melts a
molding material by heating, and mold temperature refers to the
temperature of a mold into which a resin is injected to be formed
in predetermined form. Suitably selecting these conditions,
particularly injection time, back pressure, and mold temperature,
makes it possible to easily adjust the fiber lengths of the carbon
fiber and organic fiber in a molded article.
[0155] A molded article according to the present invention has
excellent mechanical properties, particularly flexural strength and
impact strength. More specifically, a molded article according to
the present invention preferably has a flexural strength of 140 MPa
or more and 300 MPa or less. The flexural strength of 140 MPa or
more enables the molded article to have higher durability. The
flexural strength is more preferably 150 MPa or more, still more
preferably 160 MPa or more. The flexural strength of 300 MPa or
less enhances the impact strength of the molded article, and thus,
is preferable. Here, the flexural strength can be measured in
accordance with ISO178.
[0156] A molded article according to the present invention
preferably has an impact strength of 25 kJ/m.sup.2 or more and 50
kJ/m.sup.2 or less. The impact strength of 25 kJ/m.sup.2 or more
enables the molded article to have higher durability. The impact
strength is more preferably 27 kJ/m.sup.2 or more, still more
preferably 29 kJ/m.sup.2 or more. The impact strength of 50
kJ/m.sup.2 or less enhances the flexural strength, and thus, is
preferable. Here, the impact strength can be measured by carrying
out a Charpy V-notch impact test in accordance with ISO179.
[0157] Examples of methods of allowing a molded article to have a
flexural strength or an impact strength in the above-mentioned
range include methods allowing the organic fiber (B) to have a
strand strength in the above-mentioned range, methods of allowing
the interfacial shear strength to be in the above-mentioned range,
methods of allowing the ratio (L.sub.co/l.sub.no) to be in the
above-mentioned range, and the like.
[0158] Either of the flexural strength and impact strength of a
molded article preferably falls within the above-mentioned range,
and both the flexural strength and impact strength preferably fall
within the above-mentioned ranges.
[0159] Examples of applications of molded articles and molding
materials according to the present invention include: automobile
parts such as instrument panels, door beams, undercovers, spare
tire covers, front ends, structural members, and internal parts;
home and office electrical appliances and components such as
telephones, facsimiles, VTRs, copy machines, television sets,
microwave ovens, acoustic equipment, toiletries, laser discs
(registered trademark), refrigerators, and air-conditioners;
electrical and electronic equipment members typified by housings
used for personal computers, mobile phones, and the like and by
keyboard supports for supporting a keyboard in a personal computer;
and the like.
EXAMPLES
[0160] The present invention will be more specifically described
with reference to the following Examples, but the present invention
is not limited to the description of these Examples. First, the
evaluation methods of various characteristics used in the Examples
will be described.
[0161] (1) Measurement of Number Average Fiber Length
[0162] An ISO type of dumbbell specimen obtained in each of the
Examples and Comparative Examples was sandwiched between glass
plates, heated on a hot stage set to 200 to 300.degree. C., and
uniformly dispersed in film form. The film having the carbon fiber
(A) and the organic fiber (B) uniformly dispersed therein was
observed using an optical microscope (at 50 to 200.times.).
Randomly selected 1000 carbon fibers (A) and similarly randomly
selected 1000 organic fibers (B) were measured for fiber length to
calculate the number average fiber lengths using the
below-mentioned equation.
Number average fiber length=.SIGMA.(Mi)/N
[0163] Mi: fiber length (mm)
[0164] N: number of fibers
[0165] (2) Measurement of Flexural Strength of Molded Article
[0166] The ISO type of dumbbell specimen obtained in each of the
Examples and Comparative Examples was measured for flexural
strength in accordance with IS0178 using a three-point bending test
jig (the indenter radius: 5 mm) with the inter-fulcrum distance set
to 64 mm under the test condition: a test speed of 2 mm/minute. A
tester used was an "INSTRON (registered trademark)" universal
tester 5566 (manufactured by Instron Corporation).
[0167] (3) Charpy Impact Strength Measurement of Molded Article
[0168] A parallel portion was cut out of the ISO type of dumbbell
specimen obtained in each of the Examples and Comparative Example
was subjected to a Charpy V-notch impact test in accordance with
ISO179 using a C1-4-01 tester manufactured by Tokyo Koki Testing
Machine Co. Ltd., and the impact strength (kJ/m.sup.2) was
calculated.
[0169] (4) Fiber Dispersibility Evaluation of Molded Article
[0170] In each of the Examples and Comparative Examples, an 80
mm.times.80 mm.times.2 mm thick specimen was obtained, and the
number of undispersed carbon fiber (CF) bundles present in each of
the front and back sides of the specimen was counted through visual
observation. Molded articles, 50 sheets, were evaluated. The total
number for each of them was rated on the basis of the following
criteria for fiber dispersibility, and A and B were regarded as
acceptable.
A: less than one undispersed CF bundle B: one or more undispersed
CF bundles C: three or more undispersed CF bundles
[0171] (5) Adhesion Evaluation
[0172] <First Step>
[0173] First, single fiber or fiber bundles were cut to a length
easy to handle, and in cases where fiber bundles were used, single
fiber were extracted from the fiber bundles.
[0174] As depicted in FIG. 1, a single yarn 2 that had been
extracted was adhered, in straight form, to a fixing jig 1 using an
adhesive 3. After the adhesive was cured, the single yarn was cut
in such a manner that the lengths of those portions of the single
yarn which were protruded from both ends of the fixing jig 1 became
the largest. Through this step, a single yarn attached to the
fixing jig 1 and protruded straight from both ends of the fixing
jig 1 was obtained as depicted in FIG. 2. A fiber that was taken
out was observed using an optical microscope (at 200.times.), three
points of the fiber were measured for length in the fiber diameter
direction, and the average of the measurements was regarded as a
fiber diameter df.
[0175] <Second Step>
[0176] The single yarn 2 obtained in the first step was brought
down from above to a thermoplastic resin 6 heated on a heater, and
the single yarn 2 was embedded into the resin. During this, a
micrometer was used to regulate the embedded depth to approximately
300 .mu.m. The resin having the single yarn 2 embedded therein was
cooled to normal temperature, and then, the single yarn was cut at
the position up to which the single yarn was protruded several
millimeters from the resin. The resulting object together with the
base was taken out to obtain a sample depicted in FIG. 3.
[0177] <Third Step>
[0178] As depicted in FIG. 4, the sample produced in the second
step was fixed on the stage of a pull-out tester of a vertical type
using the adhesive 3, and tested at a speed of 1 .mu.m/second until
the whole fiber was displaced, i.e., pulled out of the resin.
During this, the load was measured using a load cell, and the
maximum load value was defined as F.
[0179] The embedded depth H was determined in accordance with the
following Equation using the distance X shown between the base and
the tip of the single yarn when the single yarn was embedded, and
using the body material height Y shown after the embedding was
finished.
H=Y-X
[0180] The interfacial shear strength .tau. and the critical fiber
length L.sub.c were obtained using the following Equation.
.tau.=F/(.pi.dfH)
L=(.sigma.f.times.df)/2.tau.
[0181] Here, .tau., .pi., .sigma.f, and df represent an interfacial
shear strength at the interface between fiber and matrix resin, the
circumference ratio, a single fiber strength, and a fiber diameter
(a single fiber diameter) respectively, a strand strength was used
as the single fiber strength.
[0182] The strand strength can be determined in accordance with the
resin-impregnated strand testing method described in JIS-R-7608
(2004). In formulation of a resin, CELLOXIDE (registered trademark)
2021P (manufactured by Daicel Corporation), boron trifluoride
monoethyl amine (manufactured by Tokyo Chemical Industry Co.,
Ltd.), and acetone were used at a ratio of 100:3:4 (parts by
weight), and the curing conditions: 130.degree. C. and 30 minutes
were used. As the fiber diameter df, the value measured by the
above-mentioned method was used.
Reference Example 1. Production of Carbon Fiber (A-1)
[0183] A copolymer the main component of which was
polyacrylonitrile was allowed to undergo spinning, firing
treatment, and surface oxidation treatment to obtain a continuous
carbon fiber having a total of 24,000 single fibers, a single fiber
diameter of 7 .mu.m, a per-unit-length mass of 1.6 g/m, a specific
gravity of 1.8 g/cm.sup.3, and a surface oxygen concentration ratio
[O/C] of 0.2. This continuous carbon fiber had a strand strength of
5000 MPa and a strand tensile modulus of 225 GPa. Subsequently, 2
wt % glycerol polyglycidyl ether as a multi-functional compound was
dissolved in water to prepare a sizing agent mother liquid, the
sizing agent was applied to the carbon fiber by an immersion
method, and the resulting product was dried at 230.degree. C. The
adhered amount of the sizing agent in the thus obtained carbon
fiber was 1.0 wt %.
[0184] Organic Fiber (B)
[0185] (B-1)
[0186] Polyester fiber ("TETORON (registered trademark)"
1700T-288-702C, manufactured by Toray Industries, Inc., (the single
fiber diameter: 23 .mu.m)
[0187] (B-2)
[0188] Polyester fiber ("TETORON (registered trademark)"
1100T-360-704M, manufactured by Toray Industries, Inc., (the single
fiber diameter: 17 .mu.m)
[0189] (B-3)
[0190] Polyester fiber ("TETORON (registered trademark)"
1700T-144-702C, manufactured by Toray Industries, Inc., (the single
fiber diameter: 32 .mu.m)
[0191] (B-4)
[0192] Liquid crystal polyester fiber ("SIVERAS" (registered
trademark) 1700T-288f, manufactured by Toray Industries, Inc., the
single fiber fineness: 5.7 dtex, the melting point: 330.degree. C.)
was used. (the single fiber diameter: 23 .mu.m)
[0193] (B-5)
[0194] Liquid crystal polyester fiber having polyglycidyl ether
epoxy resin adhered thereto (1 part by weight of polyglycidyl ether
epoxy resin applied to 100 parts by weight of "SIVERAS" (registered
trademark) 1700T-288f, manufactured by Toray Industries, Inc., (the
single fiber diameter: 23 .mu.m))
[0195] (B-6)
[0196] Para-aramid fiber ("KEVLAR" (registered trademark) 29,
manufactured by Du Pont-Toray Co., Ltd., the single fiber fineness:
1.6 dtex, no melting point) was used. (the single fiber diameter:
12 .mu.m)
[0197] (B-7)
[0198] Polypara-phenylene benzobisoxazole fiber ("ZYLON"
(registered trademark), manufactured by Toyobo Co., Ltd.) was used.
(the single fiber diameter: 12 .mu.m)
[0199] Thermoplastic Resin (C)
[0200] (C-1) Polypropylene resin ("PRIME POLYPRO" (registered
trademark) J137G, manufactured by Prime Polymer Co., Ltd.)
[0201] (C-2) Maleic acid-modified polypropylene resin ("PRIME
POLYPRO" (registered trademark) J137G, manufactured by Prime
Polymer Co., Ltd./"ADMER" (registered trademark) QE840,
manufactured by Mitsui Chemicals, Inc., blended at a weight ratio
of 99:1)
[0202] (C-3) Maleic acid-modified polypropylene resin ("PRIME
POLYPRO" (registered trademark) J137G, manufactured by Prime
Polymer Co., Ltd./"ADMER" (registered trademark) QE840,
manufactured by Mitsui Chemicals, Inc., blended at a weight ratio
of 97:3)
[0203] (C-4) Maleic acid-modified polypropylene resin ("PRIME
POLYPRO" (registered trademark) J137G, manufactured by Prime
Polymer Co., Ltd./"ADMER" (registered trademark) QE840,
manufactured by Mitsui Chemicals, Inc., blended at a weight ratio
of 95:5)
[0204] (C-5) Maleic acid-modified polypropylene resin ("PRIME
POLYPRO" (registered trademark) J137G, manufactured by Prime
Polymer Co., Ltd./"ADMER" (registered trademark) QE840,
manufactured by Mitsui Chemicals, Inc., blended at a weight ratio
of 90:10)
[0205] (C-6) Maleic acid-modified polypropylene resin ("PRIME
POLYPRO" (registered trademark) J137G, manufactured by Prime
Polymer Co., Ltd./"ADMER" (registered trademark) QE840,
manufactured by Mitsui Chemicals, Inc., blended at a weight ratio
of 80:20)
[0206] Component (D)
[0207] (D-1)
[0208] Solid hydrogenated terpene resin ("CLEARON" (registered
trademark) P125, manufactured by Yasuhara Chemical Co., Ltd., the
softening point: 125.degree. C.)
Example 1
[0209] The fiber (A-1) or (B-4) was embedded in the resin (C-1) in
accordance with the procedures for the above-mentioned adhesion
evaluation, and the resulting sample was used for measurement.
[0210] A long fiber reinforced resin pellet production device was
used, wherein, in the device, a coating die for a wire coating
method was installed at the tip of a TEX-30u twin-screw extruder
(the screw diameter: 30 mm, L/D=32) manufactured by Japan Steel
Works, Ltd. The above-mentioned thermoplastic resin (C-1) was
supplied through the main hopper with the extruder cylinder
temperature set to 220.degree. C., and melt-kneaded at a screw
rotational speed of 200 rpm. The discharge amount of the component
(D) melted by heating at 200.degree. C. was adjusted so as to be
8.7 parts by weight with respect to 100 parts by weight of the
total of (A) to (C), and the component (D) was added to a fiber
bundle composed of the carbon fiber (A-1) and the organic fiber
(B-4) to form the composite fiber bundle (E), which was then
supplied into a die mouth (having a diameter of 3 mm) through which
a composition containing the melted thermoplastic resin (C-1) was
discharged, and continuously arranged so as to cover the
peripheries of the carbon fiber (A-1) and the organic fiber (B-4).
The obtained strand was cooled and cut to a pellet length of 8 mm
using a cutter to produce long fiber pellets. At this time, the
take-off speed was adjusted in such a manner that the carbon fiber
(A) content was 20 parts by weight, and the organic fiber (B-4)
content was 4 parts by weight, with respect to 100 parts by weight
of the total of (A) to (C).
[0211] The thus obtained long fiber pellets were injection-molded
using an injection molding machine (J110AD manufactured by Japan
Steel Works, Ltd.) under the conditions: an injection time of 2
seconds, a back pressure of 5 MPa, a dwelling pressure of 20 MPa, a
dwell time of 10 seconds, a cylinder temperature of 230.degree. C.,
and a mold temperature of 60.degree. C., to produce an ISO type of
dumbbell specimen and an 80 mm.times.80 mm.times.2 mm specimen as
molded articles. Here, cylinder temperature refers to the
temperature of that portion of an injection molding machine which
melts a molding material by heating, and mold temperature refers to
the temperature of a mold into which a resin is injected to be
formed in predetermined form. The obtained specimens (molded
articles) were left to stand for 24 hours in a steady temperature
and humidity room adjusted to a temperature of 23.degree. C. and
50% RH, and were used for characteristic evaluation. The evaluation
results obtained by the above-mentioned methods are summarized in
Table 1.
Examples 2 to 8 and 10
[0212] Adhesion evaluation and molded article evaluation were
carried out in the same manner as in Example 1 except that the
composition and the like were changed as shown in Table 1. The
evaluation results are summarized in Table 1.
Example 9
[0213] Adhesion evaluation and molded article evaluation were
carried out in the same manner as in Example 1 except that the
pellets were cut to a length of 4 mm and that the type of the
thermoplastic resin (C) was changed to (C-2). The evaluation
results are summarized in Table 1.
Comparative Examples 1 to 14
[0214] Adhesion evaluation and molded article evaluation were
carried out in the same manner as in Example 1 except that the
composition and the like were changed as shown in Tables 2 and 3.
The evaluation results are summarized in Tables 2 and 3.
Comparative Example 15
[0215] Adhesion evaluation and molded article evaluation were
carried out in the same manner as in Example 1 except that the
molding back pressure for injection molding and the type of the
organic fiber (B) or the type of the thermoplastic resin (C) were
changed as shown in Table 3. The evaluation results are summarized
in Table 3.
TABLE-US-00001 TABLE 1 Example 1 Example 2 Example 3 Example 4
Example 5 Example 6 Raw Carbon Fiber (A) Type -- A-1 A-1 A-1 A-1
A-1 A-1 Material Blended parts by 20 20 20 20 20 20 Amount weight
Strand MPa 5000 5000 5000 5000 5000 5000 Strength Fiber .mu.m 7 7 7
7 7 7 Diameter Organic Fiber (B) Type -- B-4 B-4 B-4 B-5 B-6 B-7
Blended parts by 4 4 4 4 4 4 Amount weight Strand MPa 3500 3500
3500 3500 2800 5800 Strength Fiber .mu.m 23 23 23 23 12 12 Diameter
Single Fiber cN 150 150 150 150 40 70 Tenacity Thermoplastic Type
-- C-1 C-2 C-3 C-1 C-3 C-3 Resin (C) Blended parts by 76 76 76 76
76 76 Amount weight Component (D) Type -- D-1 D-1 D-1 D-1 D-1 D-1
Blended parts by 8.7 8.7 8.7 8.7 8.7 8.7 Amount weight Molding Back
Pressure -- MPa 5.0 5.0 5.0 5.0 5.0 5.0 Conditions Molded Critical
Fiber Length Lcc .mu.m 2800 2100 1400 2800 1400 1400 Article Lco
.mu.m 8600 7200 6400 8000 2700 5100 Number Average Fiber lnc .mu.m
520 530 520 520 520 520 Length lno .mu.m 6700 6700 6700 6700 2300
5200 Lco/lno -- -- 1.3 1.1 1.0 1.2 1.2 1.0 Lcc/Lco -- -- 0.3 0.3
0.2 0.4 0.5 0.3 Interfacial Shear Strength -- MPa 6.3 8.3 12.5 6.3
12.5 12.5 of Component (A) .tau. Interfacial Shear Strength -- MPa
4.7 5.6 6.3 5.0 6.2 6.8 of Component (B) .tau. Evaluation
Dispersibility -- -- A A A A A A Results Charpy Impact Strength --
kJ/m.sup.2 30 30 28 28 23 25 Flexural Strength -- MPa 140 150 160
150 160 160 Example 7 Example 8 Example 9 Example 10 Raw Carbon
Fiber (A) Type -- A-1 A-1 A-1 A-1 Material Blended parts by 10 30
20 20 Amount weight Strand MPa 5000 5000 5000 5000 Strength Fiber
.mu.m 7 7 7 7 Diameter Organic Fiber (B) Type -- B-4 B-4 B-4 B-4
Blended parts by 2 6 4 20 Amount weight Strand MPa 3500 3500 3500
3500 Strength Fiber .mu.m 23 23 23 23 Diameter Single Fiber cN 150
150 150 150 Tenacity Thermoplastic Type -- C-1 C-1 C-2 C-1 Resin
(C) Blended parts by 88 64 76 60 Amount weight Component (D) Type
-- D-1 D-1 D-1 D-1 Blended parts by 4.4 13.1 8.7 8.7 Amount weight
Molding Back Pressure -- MPa 5.0 5.0 5.0 5.0 Conditions Molded
Critical Fiber Length Lcc .mu.m 2800 2800 2100 2800 Article Lco
.mu.m 8600 8600 7200 8600 Number Average Fiber lnc .mu.m 520 520
350 520 Length lno .mu.m 6700 6700 3700 6700 Lco/lno -- -- 1.3 1.3
1.9 1.3 Lcc/Lco -- -- 0.3 0.3 0.3 0.3 Interfacial Shear Strength --
MPa 6.3 6.3 8.3 6.3 of Component (A) .tau. Interfacial Shear
Strength -- MPa 4.7 4.7 5.6 4.7 of Component (B) .tau. Evaluation
Dispersibility -- -- A A A B Results Charpy Impact Strength --
kJ/m.sup.2 15 34 20 35 Flexural Strength -- MPa 90 150 140 150
TABLE-US-00002 TABLE 2 Comparative Comparative Comparative
Comparative Comparative Example 1 Example 2 Example 3 Example 4
Example 5 Raw Inorganic Fiber(A) Type -- A-1 A-1 A-1 A-1 A-1
Material Blended parts by 20 20 20 20 20 Amount weight Strand MPa
5000 5000 5000 5000 5000 Strength Fiber .mu.m 7 7 7 7 7 Diameter
Organic Fiber (B) Type -- B-1 B-2 B-2 B-3 B-1 Blended parts by 4 4
4 4 4 Amount weight Strand MPa 1000 1000 1000 1000 1000 Strength
Fiber .mu.m 23 17 17 32 23 Diameter Single Fiber cN 45 25 25 90 45
Tenacity Thermoplastic Type -- C-3 C-3 C-5 C-5 C-1 Resin (C)
Blended parts by 76 76 76 76 76 Amount weight Component (D) Type --
D-1 D-1 D-1 D-1 D-1 Blended parts by 8.7 8.7 8.7 8.7 8.7 Amount
weight Molding Back Pressure -- MPa 5.0 5.0 5.0 5.0 5.0 Conditions
Molded Critical Fiber Length Lcc .mu.m 1400 1400 790 790 2800
Article Lco .mu.m 3800 2600 2200 5000 4300 Number Average Fiber lnc
.mu.m 550 520 530 510 520 Length lno .mu.m 3900 3000 2800 2800 3900
Lco/lno -- -- 1.0 0.9 0.8 1.8 1.1 Lcc/Lco -- -- 0.4 0.5 0.4 0.2 0.7
Interfacial Shear Strength -- MPa 12.5 12.5 22.2 22.2 6.3 of
Component (A) .tau. Interfacial Shear Strength -- MPa 3.0 3.3 3.9
3.2 2.7 of Component (B) .tau. Evaluation Dispersibility -- -- A A
A A A Results Charpy Impact Strength -- kJ/m.sup.2 26 20 18 18 28
Flexural Strength -- MPa 160 160 190 190 120 Comparative
Comparative Comparative Comparative Example 6 Example 7 Example 8
Example 9 Raw Inorganic Fiber(A) Type -- A-1 A-1 A-1 A-1 Material
Blended parts by 20 20 20 50 Amount weight Strand MPa 5000 5000
5000 5000 Strength Fiber .mu.m 7 7 7 7 Diameter Organic Fiber (B)
Type -- B-4 B-4 B-1 B-4 Blended parts by 4 4 20 4 Amount weight
Strand MPa 3500 3500 1000 3500 Strength Fiber .mu.m 23 23 23 23
Diameter Single Fiber cN 150 150 45 150 Tenacity Thermoplastic Type
-- C-4 C-6 C-3 C-3 Resin (C) Blended parts by 76 76 60 46 Amount
weight Component (D) Type -- D-1 D-1 D-1 D-1 Blended parts by 8.7
8.7 9.2 8.7 Amount weight Molding Back Pressure -- MPa 5.0 5.0 5.0
5.0 Conditions Molded Critical Fiber Length Lcc .mu.m 1000 800 1400
1400 Article Lco .mu.m 5500 2400 3800 6400 Number Average Fiber lnc
.mu.m 520 540 550 410 Length lno .mu.m 6700 6700 3900 3900 Lco/lno
-- -- 0.8 0.4 1.0 1.6 Lcc/Lco -- -- 0.2 0.3 0.4 0.2 Interfacial
Shear Strength -- MPa 17.5 21.9 12.5 12.5 of Component (A) .tau.
Interfacial Shear Strength -- MPa 7.3 16.8 3.0 6.3 of Component (B)
.tau. Evaluation Dispersibility -- -- A A B C Results Charpy Impact
Strength -- kJ/m.sup.2 16 15 28 5 Flexural Strength -- MPa 190 200
140 230
TABLE-US-00003 TABLE 3 Comparative Comparative Comparative
Comparative Comparative Comparative Example 10 Example 11 Example
12 Example 13 Example 14 Example 15 Raw Inorganic Fiber(A) Type --
A-1 -- A-1 A-1 A-1 A-1 Material Blended parts by 20 -- 10 10 30 20
Amount weight Strand MPa 5000 -- 5000 5000 5000 5000 Strength Fiber
.mu.m 7 -- 7 7 7 7 Diameter Organic Fiber (B) Type -- -- B-4 -- B-1
-- B-4 Blended parts by -- 4 -- 2 -- 4 Amount weight Strand MPa --
3500 -- 1000 -- 3500 Strength Fiber .mu.m -- 23 -- 23 -- 23
Diameter Single Fiber cN -- 150 -- 45 -- 150 Tenacity Thermoplastic
Type -- C-3 C-3 C-1 C-1 C-1 C-3 Resin (C) Blended parts by 80 96 90
88 70 76 Amount weight Component (D) Type -- D-1 D-1 D-1 D-1 D-1
D-1 Blended parts by 7.3 1.5 4.4 4.4 13.1 8.7 Amount weight Molding
Back Pressure -- MPa 5.0 5.0 5.0 5.0 5.0 30.0 Conditions Molded
Critical Fiber Lcc .mu.m 1400 -- 2800 2800 2800 1400 Article Length
Lco .mu.m -- 6400 -- 4300 -- 6400 Number Average lnc .mu.m 550 --
520 520 520 150 Fiber Length lno .mu.m -- 3900 -- 3900 -- 3000
Lco/lno -- -- -- 1.6 -- 1.1 -- 2.1 Lcc/Lco -- -- -- -- -- 0.7 --
0.2 Interfacial Shear Strength -- MPa 12.5 -- 6.3 6.3 6.3 12.5 of
Component (A) .tau. Interfacial Shear Strength -- MPa -- 6.3 -- 2.7
-- 6.3 of Component (B) .tau. Evaluation Dispersibility -- -- A A A
A A A Results Charpy Impact Strength -- kJ/m.sup.2 5 7 5 12 10 16
Flexural Strength -- MPa 160 80 90 90 150 120
[0216] All molded articles in Examples 1 to 10 each exhibited high
flexural strength and impact strength because the ratio
L.sub.co/l.sub.no of the organic fiber was in a specific range, and
the strand strength of the organic fiber and the interfacial shear
strength between the organic fiber and the thermoplastic resin were
each in a specific range. In contrast, the organic fibers in
Comparative Examples 1 to 4, 8, and 13 each had a strand strength
of less than 1500 MPa, with the result that the impact strength was
low. In Comparative Example 5, the interfacial shear strength
between the organic fiber (B) and the thermoplastic resin (C) was
less than 3.0 MPa, and thus, the flexural strength was
insufficient. In Comparative Examples 6 and 7, the ratio
L.sub.co/l.sub.no was less than 0.9, with the result that the
impact strength was low. In Comparative Example 9 in which the
carbon fiber (A) content was larger, the carbon fibers (A) were
entangled with one another, the fiber dispersibility was poor, and
the organic fiber was fractured in the molded article, with the
result that the impact strength was low. Comparative Examples 10,
12, and 14 each did not include the organic fiber (B), with the
result that the impact strength was low. Comparative Example 11 did
not include the carbon fiber (A), with the result that the impact
strength and flexural strength were low. In Comparative Example 15,
the higher back pressure during molding caused the organic fiber
(B) to have a shorter fiber length, and the ratio L.sub.co/l.sub.no
was not satisfied, with the result that the impact strength was
low.
REFERENCE SIGNS LIST
[0217] 1: Fixing Jig [0218] 2: Single Fiber [0219] 3: Adhesive
[0220] 4: Central Line [0221] 5: Base [0222] 6: Thermoplastic Resin
[0223] 7: Vertically Movable Portion [0224] 8: XY Stage [0225] 9:
Base [0226] 10: Single Fiber Adhering Jig of Pull-out Tester
* * * * *