U.S. patent application number 12/500413 was filed with the patent office on 2009-10-29 for thermoplastic resin composition containing a carbon fiber bundle.
This patent application is currently assigned to Mitsubishi Rayon Co., Ltd.. Invention is credited to Shinobu FUJIE, Akihiko FUKUSHIMA, Naoki SUGIURA.
Application Number | 20090270547 12/500413 |
Document ID | / |
Family ID | 34119570 |
Filed Date | 2009-10-29 |
United States Patent
Application |
20090270547 |
Kind Code |
A1 |
SUGIURA; Naoki ; et
al. |
October 29, 2009 |
THERMOPLASTIC RESIN COMPOSITION CONTAINING A CARBON FIBER
BUNDLE
Abstract
A thermoplastic resin composition, suitable for producing a
molded article (carbon fiber reinforced composite molded article)
is provided. Such a molded article has excellent mechanical
properties, and is also superior in terms of production efficiency
and economic cost, and is thus suitable for automotive parts,
housing parts of a portable electric appliances, housing parts of
common home electric appliances and the like.
Inventors: |
SUGIURA; Naoki; (Otake-shi,
JP) ; FUKUSHIMA; Akihiko; (Tokyo, JP) ; FUJIE;
Shinobu; (Tokyo, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND MAIER & NEUSTADT, L.L.P.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
Mitsubishi Rayon Co., Ltd.
Tokyo
JP
|
Family ID: |
34119570 |
Appl. No.: |
12/500413 |
Filed: |
July 9, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10566473 |
Jan 31, 2006 |
|
|
|
PCT/JP04/11053 |
Aug 2, 2004 |
|
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12500413 |
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Current U.S.
Class: |
524/502 |
Current CPC
Class: |
D06M 15/55 20130101;
Y10T 428/2918 20150115; Y10T 428/30 20150115; D06M 15/227 20130101;
Y10T 428/249945 20150401; D06M 2101/40 20130101; D06M 13/513
20130101; Y10S 428/902 20130101; C08J 2323/12 20130101; C08J 5/06
20130101; Y10T 428/249931 20150401; D06M 15/263 20130101 |
Class at
Publication: |
524/502 |
International
Class: |
C08L 23/00 20060101
C08L023/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 31, 2003 |
JP |
2003-283882 |
Jul 31, 2003 |
JP |
2003-283902 |
Jul 31, 2003 |
JP |
2003-283903 |
Claims
1. A thermoplastic resin composition comprising: a thermoplastic
resin; and a carbon fiber bundle; wherein the carbon fiber bundle
comprises: a plurality of single carbon fibers; a presize; and at
least one sizing agent; wherein the presize is obtained by
pre-sizing before a sizing treatment with a pre-sizing agent
consisting of an epoxy resin, the plurality of single carbon fibers
are sized with the at least one sizing agent, a content of the
carbon fiber bundle is 3 to 60 wt % based on total weight, and the
at least one sizing agent comprises: a polymer having a main chain
formed of carbon-carbon bonds, comprising an acid group in at least
a part of side chains or at least a part of main chain ends, and an
acid value of the polymer is in the range from 23 to 120 mg KOH/g
as measured in accordance with ASTM D1386; or a polymer having a
main chain formed of carbon-carbon bonds, comprising at least one
of an epoxy group or an ester group in at least a part of side
chains or at least a part of main chain ends.
2. The thermoplastic resin composition according to claim 1,
wherein the thermoplastic resin is a polyolefin-based resin.
3. A molded article obtained by molding the thermoplastic resin
composition according to claim 1.
4. A molded article obtained by molding the thermoplastic resin
composition according to claim 2.
5. A thermoplastic resin composition comprising: a thermoplastic
resin; and a carbon fiber bundle; wherein a content of the carbon
fiber bundle content is 3 to 60 wt % of a total weight, and the
carbon fiber bundle comprises: a plurality of single carbon fibers;
and at least one sizing agent; wherein the plurality of single
carbon fibers are sized with the at least one sizing agent, and the
at least one sizing agent comprises: a polymer having a main chain
formed of carbon-carbon bonds, comprising an acid group in at least
a part of side chains or at least a part of main chain ends, and an
acid value of the polymer is in the range from 23 to 120 mg KOH/g
as measured in accordance with ASTM D1386; or a polymer having a
main chain formed of carbon-carbon bonds, comprising at least one
of an epoxy group or an ester group in at least a part of side
chains or at least a part of main chain ends; and the single carbon
fibers comprise a plurality of wrinkles on their surface, and a
vertical difference between a highest portion and a lowest portion
in a region defined by 2 .mu.m of circumferential length.times.1
.mu.m of fiber axial direction length of the single fibers is 40 nm
or more.
6. The thermoplastic resin composition according to claim 5,
wherein the thermoplastic resin is at least one selected from the
group consisting of polyolefin-based resin, polycarbonate resin,
ABS resin, AS resin, polyoxymethylene resin, nylon resin,
polyphenylene sulfide resin, polyether sulfine resin, polyether
imide resin, polyester resin and alloy-based resins thereof.
7. A molded article obtained by molding the thermoplastic resin
composition according to claim 5.
8. A molded article obtained by molding the thermoplastic resin
composition according to claim 6.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional application of prior U.S.
application Ser. No. 10/566,473, filed Jan. 31, 2006, the
disclosure of which is incorporated herein in its entirety. The
parent application is the National Stage of PCT/JP04/11053, filed
Aug. 2, 2004, the disclosure of which is incorporated herein in its
entirety. The parent application claims priority to Japanese
Application Nos. 2003-283882, filed Jul. 31, 2003, 2003-283902,
filed Jul. 31, 2003, and JP 2003-283903, filed Jul. 31, 2003, the
disclosures of which are incorporated herein in their
entireties.
TECHNICAL FIELD
[0002] The present invention relates to a carbon fiber bundle, and
method for producing the same, which can be used as a thermoplastic
reinforcing material. The present invention further relates to a
thermoplastic resin composition, and molded article thereof, which
uses such a carbon fiber bundle.
BACKGROUND ART
[0003] A carbon fiber bundle is a form gathering together a
plurality single fibers consisting of carbon, and is used as a
reinforcing material for thermoplastic resins or the like.
[0004] When used as a reinforcing material for thermoplastic
resins, carbon fiber bundles are usually supplied being a form cut
into lengths of 5 to 15 mm. a thermoplastic resin, it is necessary
to supply the carbon fiber bundles in a fixed quantity into an
extruder. In order to do this, the form stability of the carbon
fiber bundles is important. A form that is not suitable can become
a cause for discharge unevenness. Also, because a fixed extrusion
rate cannot be attained, strand breakage occurs, whereby there is
the risk of pellet productivity dramatically falling.
[0005] Materials known as long-fiber pellets are also attracting
attention, in which carbon fiber bundles having a continuous fiber
form are charged in the pellet production process. During this
process, fluff or fly is easily formed on the carbon fiber bundle,
or, the bundle is easily loosened, so that the handling is
difficult.
[0006] Carbon fiber bundles can also be formed into a fabric and
used as a sheet material impregnated with a thermoplastic resin,
wherein the weaving quality of the carbon fiber bundles, the
handleability of the cloth after being woven and the like are
important properties.
[0007] For reasons as described above, to improve carbon fiber
bundle handleability and the physical properties of a material into
which carbon fiber bundles have been blended, it is conventional to
use carbon fiber bundles which have been converged by a sizing
treatment which deposits, for example, about 2 to 5 wt % of a
sizing agent that is compatible with the matrix resin, such as an
agent having an epoxy resin as a main component.
[0008] Examples of the thermoplastic resin used as the matrix resin
typically include polycarbonate resin, nylon resin, polyester resin
and the like. Recently, however, the number of cases of using a
polyolefin-based resin has been increasing for reasons of
recyclability and cost. Polypropylene resin in particular has been
drawing attention in recent years.
[0009] Since polyolefin-based resins are basically nonpolar, their
interfacial adhesion with the carbon fibers or glass fibers is
extremely poor and the effects of improved mechanical properties as
a reinforcing material cannot be adequately expressed in many
cases. Countermeasures for this are known to include a method which
improves adhesion by adding an acid modified polyolefin-based resin
to the matrix resin, and a method which subjects the carbon fibers
or glass fibers to a sizing treatment with a sizing agent
constituted from a polyolefin-based resin and a silane coupling
agent and the like. Another known method, as described in Japanese
Patent Application Laid-Open No. 6-107442 (Patent Document 1),
subjects the carbon fibers or glass fibers to a sizing treatment
using a sizing agent having acid modified polypropylene as an
essential component.
[0010] However, in the method which adds an acid modified
polyolefin-based resin to the matrix resin, a large amount of acid
modified polyolefin-based resin has to be added, whereby a product
having excellent recyclability and cost effectiveness cannot be
obtained. On the other hand, in the method sizing with a sizing
agent containing a silane coupling agent, because carbon fibers do
not have so many oxygen groups on the surface as compared with
glass fibers, the effects for improving interfacial adhesion are
rather minimal.
[0011] Further, although the method sizing with a sizing agent
having acid modified polypropylene as an essential component
described in Patent Document 1 achieves good interfacial adhesion
as compared with a polyolefin-based resin, in the case of carbon
fibers the effects were not sufficient.
Patent Document 1: Japanese Patent Application Laid-Open No.
6-107442
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0012] The present invention was created in view of the
above-described matters, wherein it is an object thereof to provide
a carbon fiber bundle which can develop satisfactory interfacial
adhesion with a polyolefin-based resin, especially polypropylene
resin.
Means for Solving the Problems
[0013] The present invention includes:
[0014] a carbon fiber bundle comprising a plurality of single
fibers, and sized with a sizing agent comprising:
[0015] a polymer having a main chain formed of carbon-carbon bonds,
containing an acid group in at least a part of side chains or at
least a part of main chain ends, and representing an acid value of
23 to 120 mgKOH/g as measured in accordance with ASTM D1386; or
[0016] a polymer having a main chain formed of carbon-carbon bonds,
and containing at least either of an epoxy group and an ester group
in at least a part of side chains or at least a part of main chain
ends. The present invention especially includes the following
embodiments:
[0017] (1) The carbon fiber bundle, wherein the sizing was
conducted after pre-sized with a pre-sizing agent consisting of an
epoxy resin;
[0018] (2) The carbon fiber bundle, wherein the single fibers
comprise a plurality of wrinkles on their surface, wherein a
vertical difference between a highest portion and a lowest portion
in a region defined by 2 .mu.m of circumferential length.times.1
.mu.m of fiber axial direction length of the single fibers is 40 nm
or more.
[0019] The method for producing the carbon fiber bundle of the
above (1) especially includes the following embodiment:
[0020] A method for producing a carbon fiber bundle comprising a
plurality of single fibers, comprising the steps of:
[0021] pre-sizing the carbon fiber bundle with a pre-sizing agent
consisting of an epoxy resin;
[0022] sizing the pre-sized carbon fiber bundle, so that an amount
of a sizing agent to the total is 1 to 5 wt %, by using an aqueous
sizing agent solution dissolving or dispersing in water the sizing
agent comprising:
[0023] a polymer having a main chain formed of carbon-carbon bonds,
containing an acid group in at least a part of side chains or at
least a part of main chain ends, and representing an acid value of
23 to 120 mgKOH/g as measured in accordance with ASTM D1386; or
[0024] a polymer having a main chain formed of carbon-carbon bonds,
containing at least either of an epoxy group and an ester group in
at least a part of side chains or at least a part of main chain
ends;
[0025] cutting the carbon fiber bundle to a prescribed length;
and
[0026] drying the carbon fiber bundle cut to the prescribed
length.
[0027] The method for producing the carbon fiber bundle of the
above (2) especially includes the following preferable
embodiment:
[0028] A method for producing a carbon fiber bundle comprising a
plurality of single fibers, wherein the single fibers comprise a
plurality of wrinkles on their surface, wherein a vertical
difference between a highest portion and a lowest portion in a
region defined by 2 .mu.m of circumferential length.times.1 .mu.m
of fiber axial direction length of the single fibers is 40 nm or
more, comprising the steps of:
[0029] sizing the carbon fiber bundle, so that an amount of a
sizing agent to the total is 1 to 5 wt %, by using an aqueous
sizing agent solution dissolving or dispersing in water the sizing
agent comprising:
[0030] a polymer having a main chain formed of carbon-carbon bonds,
containing an acid group in at least a part of side chains or at
least a part of main chain ends, and representing an acid value of
23 to 120 mgKOH/g as measured in accordance with ASTM D1386; or
[0031] a polymer having a main chain formed of carbon-carbon bonds,
containing at least either of an epoxy group and an ester group in
at least a part of side chains or at least a part of main chain
ends;
[0032] cutting the carbon fiber bundle to a prescribed length with
regulating the moisture content of the carbon fiber bundle to 20 to
60 wt %; and
[0033] drying the carbon fiber bundle cut to a prescribed
length.
[0034] In addition, the present invention includes a thermoplastic
resin composition comprising a thermoplastic resin and the carbon
fiber bundle, wherein the carbon fiber bundle content is 3 to 60 wt
%.
[0035] Further, the present invention includes a molded article
obtained by molding the thermoplastic resin composition.
EFFECTS OF THE INVENTION
[0036] According to the carbon fiber bundle of the present
invention, satisfactory interfacial adhesion with polyolefin-based
resins, especially polypropylene resin, can be developed.
BEST MODE FOR CARRYING OUT THE INVENTION
[0037] The carbon fiber bundle according to the present invention
is a carbon fiber bundle comprising a plurality of single fibers,
and sized with a sizing agent comprising:
[0038] a polymer having a main chain formed of carbon-carbon bonds,
containing an acid group in at least a part of side chains or at
least a part of main chain ends, and representing an acid value of
23 to 120 mgKOH/g as measured in accordance with ASTM D1386; or
[0039] a polymer having a main chain formed of carbon-carbon bonds,
and containing at least either of an epoxy group and an ester group
in at least a part of side chains or at least a part of main chain
ends. Especially, following preferable embodiments are
provided:
[0040] (1) The carbon fiber bundle, wherein the sizing was
conducted after pre-sized with a pre-sizing agent consisting of an
epoxy resin;
[0041] (2) The carbon fiber bundle, wherein the single fibers
comprise a plurality of wrinkles on their surface, wherein a
vertical difference between a highest portion and a lowest portion
in a region defined by 2 .mu.m of circumferential length.times.1
.mu.m of fiber axial direction length of the single fibers is 40 nm
or more.
(Carbon Fiber Bundle Before Sizing)
[0042] In the present invention there are no particular limits on
the carbon fiber bundle before sizing, so that a carbon fiber
bundle comprising a plurality of known single fibers can be
employed. Normally, it is a form gathering together about 1,000 to
50,000 single fibers having an average diameter of 5 to 8 .mu.m.
The single fibers constituting such a carbon fiber bundle are
obtained by making an acrylonitrile polymer, pitch obtained from
petroleum or coal, or the like into a fiber, and then carbonizing
the fiber. Fibers that can be used include those which have
undergone the carbonizing treatment, fibers which have undergone a
wet electrolytic oxidation treatment to thereby incorporate an
oxygen-containing functional group onto the surface, and fibers
which have bee pre-sized.
[0043] In particular, examples of a carbon fiber bundle before
sizing which can be preferably used in the present invention
include:
[0044] (I-1) A carbon fiber bundle comprising a plurality of single
fibers, wherein the single fibers comprise a plurality of wrinkles
on their surface, wherein a vertical difference between a highest
portion and a lowest portion in a region defined by 2 .mu.m of
circumferential length.times.1 .mu.m of fiber axial direction
length of the single fibers is 40 nm or more; and
[0045] (I-2) A carbon fiber bundle pre-sized with a pre-sizing
agent consisting of an epoxy resin.
[0046] In the present invention, the carbon fiber bundle preferably
comprises a plurality of single fibers, wherein the single fibers
comprise a plurality of wrinkles on their surface, wherein a
vertical difference between a highest portion and a lowest portion
in a region defined by 2 .mu.m of circumferential length.times.1
.mu.m of fiber axial direction length of the single fibers is 40 nm
or more (I-1). Further, the vertical difference between the highest
portion and the lowest portion is preferably 10% or less of the
diameter of the single fibers. The depth of the wrinkles which are
present on the single fiber surface is defined by the vertical
difference between the highest portion and the lowest portion in
the region defined by 2 .mu.m of circumferential length.times.1
.mu.m of fiber axial direction length. A wrinkle on the single
fiber surface refers to an uneven shape having a length of 1 .mu.m
or more in a given direction. This direction is not particularly
limited, and may be parallel, perpendicular or at an angle to the
fiber axial direction. In the general production method for a
carbon fiber bundle comprising a plurality of single fibers,
wrinkles which are approximately parallel to the fiber axial
direction are present on the usual single fiber surface. The
vertical difference can be estimated in the following manner based
on the surface shape obtained by scanning the surface of the single
fibers with a scanning atomic force microscope (AFM).
[0047] Several single fibers of a carbon fiber bundle are placed
onto a specimen stage, and fixed at both ends. Dotite is applied
around their periphery to form measurement samples. Employing a
cantilever made from silicon nitride, an atomic force microscope
(Model: SPI 3700/SPA-300 (trade name), manufactured by Seiko
Instruments Inc.) is used to measure in AFM mode by repeatedly
scanning a 2 to 7 .mu.m range in the periphery direction of the
single fibers while slowly moving in 1 .mu.m intervals across the
fibers in a fiber axial direction. The low frequency component of
the obtained measured images is cut by two-dimensional Fourier
transform, and the cut images then undergo an inverse transform.
The vertical difference between the highest portion and the lowest
portion in the region defined by 2 .mu.m of circumferential
length.times.1 .mu.m of fiber axial direction length is then read
from the planar image of the cross-section from which the obtained
single fiber curvature has been removed.
[0048] Examples of a carbon fiber bundle having a plurality of such
single fibers include, for example, TR50S and TR30L (trade names),
manufactured by Mitsubishi Rayon Co., Ltd.
[0049] The above-described single fibers preferably have a ratio of
major axis to minor axis (major axis/minor axis) of the
cross-section of 1.03 to 1.20. If the major axis/minor axis is less
than 1.03, adhesion between the single fibers is so strong as a
result of the sizing agent after sizing, which worsens the
loosening property of the single fibers when mixed or impregnated
with the resin, whereby on occasion an evenly dispersed molded
article cannot be obtained. If the major axis/minor axis is more
than 1.20, the adhesion between single fibers is so weak, and the
carbon fiber bundle is easily loosened, whereby on occasion
stability during the fixed length cutting step and the
morphological stability of the carbon fiber bundle after being cut
may deteriorate. Especially preferable is 1.05 to 1.15. The
above-described major axis/minor axis value can be measured as
described below.
[0050] After passing the carbon fiber bundle to be measured through
a tube with the inner diameter of 1 mm made from a vinyl chloride
resin, the carbon fiber bundle is cut with a knife into round
slices to be used as specimens. These specimens are then adhered
with their cross-section facing upwards onto a SEM specimen stage,
and sputtered with Au to a 10 nm thickness. The cross-sections are
then observed with a scanning electron microscope (XL20 (trade
name), manufactured by Philips) under the conditions of an
accelerating voltage of 7.00 kV, and operating distance of 31 mm,
and the major axis and minor axis of the single fiber cross-section
are then measured.
[0051] The above-described single fibers preferably have a Si
content of 500 ppm or less as measured by ICP emission
spectrometry. If the Si content is more than 500 ppm, the
wettability and interfacial adhesion with the matrix resin can
deteriorate. Especially preferable is 350 ppm or less. The
above-described Si content can be measured as described below.
[0052] A carbon fiber bundle is placed in a platinum crucible with
a known tare and incinerated in a muffle furnace at from 600 to
700.degree. C. The incinerated matter is weighed to obtain the ash
content. A fixed amount of sodium carbonate is subsequently charged
thereto, and the resulting mixture is melted by a burner and is
dissolving with DI water (ion-exchange water) to be a constant
volume in a 50 ml plastic graduated flask. The Si content of this
sample is then obtained by ICP emission spectrometry.
[0053] In the present invention, the carbon fiber bundle has
preferably been pre-sized with a pre-sizing agent consisting of an
epoxy resin (I-2). The pre-sizing treatment refers to a treatment
for depositing a pre-sizing agent onto the carbon fiber bundle.
This pre-sizing treatment allows the convergence of the carbon
fiber bundle to be increased, while simultaneously also enabling
the affinity of the below-described pre-sizing agents with the
carbon fiber bundle to be increased.
[0054] A pre-sizing agent consisting of an epoxy resin is
preferable because of its excellent affinity with the single fibers
of the carbon fiber bundle and handleability, and also because just
a small amount can cause the single fibers to converge. In
addition, a carbon fiber bundle which has been pre-sized with a
pre-sizing agent consisting of an epoxy resin provides a
significantly excellent process passing; for instance the carbon
fiber bundle does not wind onto the roller during the subsequent
sizing step. Further, wettability with the sizing agent used in the
present invention is satisfactory, whereby the sizing agent can be
evenly deposited.
[0055] When a carbon fiber bundle is pre-sized with a pre-sizing
agent consisting of an epoxy resin, usually, an aqueous pre-sizing
agent solution is used in which a water-soluble or
water-dispersible epoxy resin is dissolved or dispersed in water.
The water-soluble or water-dispersible epoxy resin is not
particularly restricted, so that a known resin can be used. If the
resin can be used in an aqueous solution, a modified epoxy resin
can also be used. In addition, a single kind of epoxy resin can be
used alone, or 2 or more kinds can be used mixed together. From the
viewpoint of process passing for the below-described step for
depositing the sizing agent and other factors, it is more
preferable that a resin which is liquid at room temperature and a
resin which is solid at room temperature are used in combination as
the epoxy resin.
[0056] Examples of water-soluble epoxy resins include resins having
glycidyl groups on both ends of a ethylene glycol chain, and resins
having glycidyl groups on both ends of ethylene oxide added on both
ends of bisphenol A, F, S, etc. A compound having an alicyclic
epoxy group in place of the glycidyl group can also be used.
[0057] Examples of water-dispersible epoxy resins include bisphenol
A type epoxy resins, bisphenol F type epoxy resins and bisphenol S
type epoxy resins, phenol novolak type epoxy resins, cresol novolak
type epoxy resins, biphenyl type epoxy resins, naphthalene-skeleton
type epoxy resins, aliphatic-based epoxy resins, dicyclopentadiene
type epoxy resins (e.g. HP 7200 (trade name) manufactured by
Dainippon Ink and Chemicals, Incorporated), glycidyl amine type
epoxy resins, and DPP novolak type epoxy resins (e.g. Epikote
157S65 (trade name) manufactured by Japan Epoxy Resins Co., Ltd.).
A compound having an alicyclic epoxy group in place of the glycidyl
group can also be used.
[0058] If using a pre-sizing agent consisting of a
water-dispersible epoxy resin, it is preferable to conduct the
pre-sizing treatment with an aqueous emulsion to which an
emulsifier has been further added. The emulsifier is not
particularly restricted, so that anionic, cationic, nonionic or the
like emulsifiers can be used. Among these, anionic or nonionic
emulsifiers are preferable, as they have good emulsification
property, and are low cost. Non-ionic emulsifiers are especially
preferable, as they do not interfere with pre-sizing agent
stability.
[0059] Examples of nonionic emulsifiers include polyethylene glycol
type (higher alcohol ethylene oxide adducts, alkylphenol ethylene
oxide adducts, aliphatic ethylene oxide adducts, polypropylene
glycol ethylene oxide adducts and the like), and polyhydric alcohol
type (glycerin fatty acid esters, sorbitol fatty acid esters, fatty
acid alkanolamide and the like). However, the HLB of the nonionic
emulsifier is usually 8 to 20. If a nonionic emulsifier is used
whose HLB is outside of this range, a stable aqueous emulsion may
not be attained.
[0060] Examples of anionic emulsifiers include carboxylate type
(potassium oleate, sodium oleate and the like), sulfonate type
(sodium dodecylbenzene sulfonate, sodium dioctylsulfosuccinate and
the like), and sulfate type (sodium lauryl sulfate and the like).
Examples of the neutralizer include potassium hydroxide, sodium
hydroxide, magnesium hydroxide, calcium hydroxide, sodium
carbonate, sodium bicarbonate, potassium carbonate, potassium
bicarbonate, calcium carbonate, calcium bicarbonate, magnesium
carbonate, magnesium bicarbonate, monolaurylamine, trimethylamine,
dimethyl monoethanolamine, triethanolamine, ethylenediamine,
ammonia, and the like. Examples of the reducing agents include
sodium sulfite and the like.
[0061] Examples of the emulsification method include a method which
employs a batch system with a stirrer, a method which employs a
ball mill, a method which employs a shaking apparatus and a method
which employs a high-shear emulsion machine, such as a Gaulin
homogenizer. By setting the emulsification temperature higher than
the softening temperature of the pre-sizing agent to be used, an
aqueous emulsion can be obtained which has sufficient stability.
The time required for emulsification is usually several minutes to
2 hours. After emulsification, an aqueous emulsion can be obtained
by cooling to room temperature. While the aqueous emulsion
concentration is not particularly limited, the emulsion is diluted
with water so as to have the pre-sizing agent concentration of
about 5 to 60 wt %.
[0062] For an aqueous emulsion in which a pre-sizing agent is
dispersed, other sizing agents (e.g. vinyl acetate resin emulsion,
urethane resin emulsion, acrylic resin emulsion or the like), a
silane coupling agent, and an antistatic agent can be used in
combination as necessary. In addition, a lubricant or smoothing
agent can also be used in combination therewith.
[0063] The amount of such a pre-sizing agent deposited is
preferably 0.1 to 2.0 wt % to the total carbon fiber bundle, and
0.2 to 1.2 is more preferable. This range is preferable because
within such a range the number of molecular layers of the
pre-sizing agent covering the carbon fiber surface of the carbon
fiber bundle is about 1 to 3. If the amount deposited is more than
2.0 wt %, the pre-sizing agent acts to cause bridging between the
carbon fibers to cause pseudo-adhesion between the single fibers
and to constrain movement of single fibers, whereby the carbon
fiber bundle become less spreadable, which can even result in a
risk that the uniformity of the carbon fiber bundle is harmed.
Further, the permeability of the sizing agent which is deposited in
a later step is interfered with, whereby there is a risk of a
deterioration in the properties as a carbon fiber bundle, such as
it becoming more difficult to obtain a uniform carbon fiber bundle.
On the other hand, if the amount deposited is less than 0.1 wt %,
the effects of depositing the pre-sizing agent are not exhibited,
whereby there is a risk that a carbon fiber bundle having excellent
process passing, handleability, and affinity with the sizing agent
cannot be obtained.
[0064] The pre-sizing treatment can be carried out in the same
manner as that for the below-described sizing treatment with a
sizing agent.
(Sizing Agent Used in the Sizing Treatment)
[0065] In the present invention, the carbon fiber bundle is sized
with a sizing agent comprising:
[0066] a polymer having a main chain formed of carbon-carbon bonds,
containing an acid group in at least a part of side chains or at
least a part of main chain ends, and representing an acid value of
23 to 120 mgKOH/g as measured in accordance with ASTM D1386; or
[0067] a polymer having a main chain formed of carbon-carbon bonds,
containing at least either of an epoxy group and an ester group in
at least a part of side chains or at least a part of main chain
ends.
[0068] The method of sizing treatment according to the present
invention comprises a step for depositing a sizing agent which
comprises the above-described polymer onto a carbon fiber bundle.
As mentioned above, a carbon fiber bundle onto which a sizing agent
comprising the above-described polymer is deposited may be one
pre-sized, in which case the method of sizing treatment comprises a
pre-sizing step with a pre-sizing agent and a main sizing step with
a sizing agent comprising the above-described polymer. From this
sizing treatment, convergence of the carbon fiber bundle can be
further increased, and at the same time the affinity of the carbon
fiber bundle with the matrix resin can be increased.
[0069] In particular, examples of preferable sizing agents in the
present invention include:
[0070] (i) A sizing agent comprising at least 35 wt % of an acid
modified polypropylene resin (compound a1) having a weight average
molecular weight of 45,000 or less, and an acid value of 23 to 120
mgKOH/g as measured in accordance with ASTM D1386;
[0071] (ii) A sizing agent comprising at least 35 wt % of an acid
modified polypropylene resin (compound a2) having a number average
molecular weight of 45,000 or less, and an acid value of 23 to 120
mg KOH/g as measured in accordance with ASTM D1386, and at least 5
wt % of an olefin-based thermoplastic elastomer resin (compound
b);
[0072] (iii) A sizing agent comprising at least 40 wt % of a
copolymer (compound c) obtained by copolymerizing ethylene or
propylene and an epoxy-containing monomer;
[0073] (iv) A sizing agent comprising at least 40 wt % of a
copolymer (compound d) obtained by copolymerizing ethylene or
propylene, an epoxy-containing monomer and an acrylic ester;
and
[0074] (v) A sizing agent comprising at least 40 wt % of copolymer
components consisting of the compound c and the compound d.
[0075] The acid modified polypropylene resin (compound a1), which
is an essential component of the sizing agent represented by the
above-described (i), is the component to act as an efficient
coupling agent, which the acidic group in the molecule boost the
interaction with the single fiber surface of the carbon fiber
bundle or the pre-sizing agent deposited to the carbon fiber bundle
surface when the complex of the carbon fiber bundles and
polyolefin-based resin or other such matrix resin is formed, while
the polypropylene chain in the skeleton causes strong bonds to form
with the matrix resin as a result of the molecules being entangled
together. Therefore, the acid modified polypropylene resin
(compound a1) preferably comprises 35 wt % or more of the sizing
agent and more preferably 40 wt % or more.
[0076] The weight average molecular weight of the acid modified
polypropylene resin (compound a1) is preferably 45,000 or less,
more preferably 30,000 or less and further preferably 20,000 or
less. If the weight average molecular weight is more than 45,000,
the mobility in the interfacial phase vicinity may be insufficient,
and the intermolecular entanglement with the matrix resin may be
lower, whereby interfacial adhesion cannot be made sufficiently
strong. Further, from the viewpoint of the required molecule length
for exhibiting coupling effects at the interfacial phase of a
carbon fiber bundle and the resin, weight average molecular weight
is preferably 500 or more. Here, the weight average molecular
weight is measured by GPC.
[0077] The acid value as measured in accordance with ASTM D1386 of
the acid modified polypropylene resin (compound a1) is preferably
23 to 120 mgKOH/g, more preferably 29 to 90 mgKOH/g, further
preferably 35 to 80 mgKOH/g and especially preferably 40 to 75
mgKOH/g. If the acid value is less than 23 mgKOH/g, interaction
with the single fiber surface of the carbon fiber bundle or the
pre-sizing agent deposited to the carbon fiber bundle surface is
low, whereby high interfacial adhesion cannot be obtained. On the
other hand, if the acid value is more than 120 mgKOH/g, affinity
with the matrix resin, especially with a polyolefin-based resin,
deteriorates, whereby consequently entangling with the molecules
does not sufficiently occur, wherein interfacial adhesion cannot be
made sufficiently strong.
[0078] Specific examples of such an acid modified polypropylene
resin (compound a1) include GF-101 (Trade name, aqueous emulsion)
manufactured by Yoshimura Oil Chemical Co., Ltd., Hostamont AR 503
and AR 504 (trade names) manufactured by Clariant and the like.
[0079] The sizing agent represented by the above-described (i)
preferably further comprises at least 5 wt % of an olefin-based
thermoplastic elastomer resin (compound b). The olefin-based
thermoplastic elastomer resin (compound b) may make the carbon
fiber bundle sufficiently convergent and drapable. Also, it keeps
itself sufficient affinity with the polyolefin-based resin or other
such matrix resin. More preferable is 8 wt % or more. The weight
ratio between the acid modified polypropylene resin (compound a1)
and the olefin-based thermoplastic elastomer resin (compound b) is
preferably 15/1 to 1/1.
[0080] The Vicat softening point as measured in accordance with
ASTM D1525-70 of the olefin-based thermoplastic elastomer resin
(compound b) is preferably 120.degree. C. or less. More preferable
is 110.degree. C. or less, and further preferable is 90.degree. C.
or less. This is because the carbon fiber bundle after it is dried
will be satisfactory convergent if the olefin-based thermoplastic
elastomer resin (compound b) has been sufficiently softened for
during the step evaporating off the water, which are usually
conducted at about 140.degree. C., after depositing an aqueous
sizing agent solution in which a sizing agent has been dissolved or
dispersed in water.
[0081] Specific examples of such an olefin-based thermoplastic
elastomer resin (compound b) include GFE-1030 (Trade name, aqueous
emulsion) manufactured by Yoshimura Oil Chemical Co., Ltd.,
TPO-M142, R110E and T310E (trade names) manufactured by Idemitsu
Petrochemical Co., Ltd., and the like.
[0082] The acid modified polypropylene resin (compound a2), which
is an essential component of the sizing agent represented by the
above-described (ii), is the component to act as an efficient
coupling agent, which the acidic group in the molecule boost the
interaction with the single fiber surface of the carbon fiber
bundle or the pre-sizing agent deposited to the carbon fiber bundle
surface when the complex of the carbon fiber bundles and
polyolefin-based resin or other such matrix resin is formed, while
the polypropylene chain in the skeleton causes strong bonds to form
with the matrix resin as a result of the molecules being entangled
together.
[0083] The number average molecular weight of the acid modified
polypropylene resin (compound a2) is preferably 45,000 or less,
more preferably 30,000 or less, further preferably 20,000 or less
and especially preferably 10,000 or less. If the weight average
molecular weight is more than 45,000, the mobility in the
interfacial phase vicinity may be insufficient, and the
intermolecular entanglement with the matrix resin may be lower,
whereby interfacial adhesion cannot be made sufficiently strong.
Further, from the viewpoint of the required molecule length for
exhibiting coupling effects at the interfacial phase of a carbon
fiber bundle and the resin, number average molecular weight is
preferably 500 or more. Here, the number average molecular weight
is measured by GPC.
[0084] The acid value as measured in accordance with ASTM D1386 of
the acid modified polypropylene resin (compound a2) is preferably
23 to 120 mgKOH/g, more preferably 29 to 90 mgKOH/g, and further
preferably 35 to 80 mgKOH/g. If the acid value is less than 23
mgKOH/g, interaction with the single fiber surface of the carbon
fiber bundle or the pre-sizing agent deposited to the carbon fiber
bundle surface is low, whereby high interfacial adhesion cannot be
obtained. On the other hand, if the acid value is more than 120
mgKOH/g, affinity with the matrix resin, especially with a
polyolefin-based resin, deteriorates, whereby consequently
entangling with the molecules does not sufficiently occur, wherein
interfacial adhesion cannot be made sufficiently strong.
[0085] Specific examples of such an acid modified polypropylene
resin (compound a2) include GF-101 (Trade name, aqueous emulsion)
manufactured by Yoshimura Oil Chemical Co., Ltd., Hostamont AR 503
and AR 504 (trade names) manufactured by Clariant and the like.
[0086] The olefin-based thermoplastic elastomer resin (compound b)
contained in the sizing agent represented by the above-described
(ii) may make the carbon fiber bundle sufficiently convergent and
drapable. Also, it keeps itself sufficient affinity with the
polyolefin-based resin or other such matrix resin.
[0087] The Vicat softening point as measured in accordance with
ASTM D1525-70 of the olefin-based thermoplastic elastomer resin
(compound b) is preferably 120.degree. C. or less. More preferable
is 110.degree. C. or less, and further preferable is 90.degree. C.
or less. This is because the carbon fiber bundle after it is dried
will be satisfactory convergent if the olefin-based thermoplastic
elastomer resin (compound b) has been sufficiently softened for
during the step evaporating off the water, which are usually
conducted at about 140.degree. C., after depositing an aqueous
sizing agent solution in which a sizing agent has been dissolved or
dispersed in water.
[0088] Specific examples of such an olefin-based thermoplastic
elastomer resin (compound b) include GFE-1030 (Trade name, aqueous
emulsion) manufactured by Yoshimura Oil Chemical Co., Ltd.,
TPO-M142, R110E and T310E (the above are trade names) manufactured
by Idemitsu Petrochemical Co., Ltd. and the like.
[0089] The sizing agent represented by the above-described (ii)
preferably further comprises 35 wt % or more, preferably 40 wt % or
more, of the acid modified polypropylene resin (compound a2), and 5
wt % or more, preferably 8 wt % or more, of the olefin-based
thermoplastic elastomer resin (compound b). Since these two
compounds take on an important role in the manner described above,
in order to effectively express their roles their minimum content
is respectively independently prescribed. The weight ratio between
the acid modified polypropylene resin (compound a1) and the
olefin-based thermoplastic elastomer resin (compound b) is
preferably 15/1 to 1/1.
[0090] The essential components of the sizing agents represented by
the above-described (iii) to (v), that is a copolymer component
consisting of one or both of a copolymer (compound c) obtained by
copolymerizing ethylene or propylene and an epoxy-containing
monomer, and a copolymer (compound d) obtained by copolymerizing
ethylene or propylene, an epoxy-containing monomer and an acrylic
ester, act extremely efficiently as a coupling agent between the
matrix resin such as a polyolefin-based resin and the carbon fiber
bundle. The reason for this is that since the main skeleton of the
polymer is formed from ethylene or propylene units, its
compatibility with the matrix resin is very excellent, and further,
that since an epoxy group is contained in the molecule, a strong
chemical interaction can be formed with the single fiber surface of
the carbon fiber bundle or the pre-sizing agent deposited to the
carbon fiber bundle surface. The sizing agent contains these
copolymer components of preferably 40 wt % or more, more preferably
50 wt % or more. If less than 40 wt %, the improved performance of
interfacial adhesion due to the copolymer components cannot be
sufficiently exhibited in some cases.
[0091] The copolymer (compound c) obtained by copolymerizing
ethylene or propylene and an epoxy-containing monomer can be used
alone (iii). The copolymer (compound d) obtained by copolymerizing
ethylene or propylene, an epoxy-containing monomer and an acrylic
ester can be used alone (iv). The copolymer (compound c) obtained
by copolymerizing ethylene or propylene and an epoxy-containing
monomer and the copolymer (compound d) obtained by copolymerizing
ethylene or propylene, an epoxy-containing monomer and an acrylic
ester can be used together (v).
[0092] The ratio of units derived from the epoxy-containing monomer
in these copolymer components, although not particularly limited,
is preferably 5% or more by mole ratio, and more preferably 10% or
more, in order for the effects of the epoxy group to be expressed.
The Vicat softening point of these copolymer components, although
not particularly limited, is preferably 120.degree. C. or less,
more preferably 110.degree. C. or less, and further preferably
90.degree. C. or less. This is, as described above, because
satisfactory convergence of the carbon fiber bundle after the
drying step can be conferred.
[0093] Examples of such a copolymer (compound c) obtained by
copolymerizing ethylene or propylene and an epoxy-containing
monomer include Bondfast 2C and Bondfast E (trade names)
manufactured by Sumitomo Chemical Co., Ltd., Rexpearl RA3150 (trade
name) manufactured by Japan Polyolefin Corporation, Sepolsion G118
(trade name) manufactured by Sumitomo Seika Chemicals Co., Ltd.,
and the like. Examples of a copolymer (compound d) obtained by
copolymerizing ethylene or propylene, an epoxy-containing monomer
and an acrylic ester include Bondfast 7L and Bondfast 7M (trade
names) manufactured by Sumitomo Chemical Co., Ltd., and the
like.
[0094] The sizing agent represented by the above-described (iii) to
(v) preferably further comprises a copolymer (compound e) of
ethylene or propylene, an acrylic ester and a monomer containing an
acid anhydride group. Copolymer (compound e) of ethylene or
propylene, an acrylic ester and a monomer containing an acid
anhydride group also acts extremely efficiently as a coupling agent
between the matrix resin such as a polyolefin-based resin and the
carbon fiber bundle. The reason for this is that since the main
skeleton of the polymer is formed from ethylene or propylene units,
its compatibility with the matrix resin is very excellent, and
further, that since an acid group is contained in the molecule, a
strong chemical interaction can be formed with the single fiber
surface of the carbon fiber bundle or the pre-sizing agent
deposited to the carbon fiber bundle surface. The sizing agent
contains the copolymer (compound e) of ethylene or propylene, an
acrylic ester and a monomer containing an acid anhydride group of
preferably 40 wt % or more, more preferably 50 wt % or more. If
less than 40 wt %, the improved performance of interfacial adhesion
due to this copolymer component cannot be sufficiently exhibited in
some cases.
[0095] The Vicat softening point of the copolymer (compound e) of
ethylene or propylene, an acrylic ester and a monomer containing an
acid anhydride group, although not particularly limited, is
preferably 120.degree. C. or less and more preferably 110.degree.
C. or less. This is, as described above, because satisfactory
convergence of the carbon fiber bundle after the drying step can be
conferred.
[0096] Specific examples of such a copolymer (compound e) of
ethylene or propylene, an acrylic ester and a monomer containing an
acid anhydride group include the Bondine (registered trademark)
series, manufactured by Sumitomo Chemical Co., Ltd., the Rexpearl
ET series (trade name) manufactured by Japan Polyolefin
Corporation, Sepolsion M220E (trade name) manufactured by Sumitomo
Seika Chemicals Co., Ltd., and the like.
[0097] The amount of the sizing agent deposited onto a carbon fiber
bundle in all these embodiments is not particularly restricted, and
may be set as the amount necessary to express the desired functions
from the sizing agent. For example, for a carbon fiber bundle in
continuous form, the amount deposited is preferably 0.3 to 5 wt %
of the total. Especially preferable is 0.8 to 4 wt %. Further, for
a carbon fiber bundle cut to a prescribed length, from 1 to 5 wt %
is preferable. Especially preferable is 1.2 to 4 wt %. If t there
is too little sizing agent, the bundle may be inadequately
convergent and the form stability of the cut bundle may
deteriorate. If there is too much sizing agent, in some cases
wettability during the blending step with the resin and the
loosening property for the single fibers dramatically deteriorate.
The amount of sizing agent deposited onto a carbon fiber bundle is,
as the component amount excluding water of the carbon fiber bundle
total, the amount of the sizing agent deposited measured by thermal
decomposition in accordance with SACMA method SRM 14-90. When
conducting a pre-sizing treatment, this can be calculated by
subtracting the amount of the pre-sizing agent deposited which is
separately-measured.
(Sizing Method)
[0098] When sizing with an above-described sizing agent, usually,
the carbon fiber bundle is sized with an aqueous sizing agent
solution in which the sizing agent is dissolved or dispersed in
water. Giving consideration to industrial production, it is
preferable in terms of safety and economy to carry out the sizing
treatment with an aqueous emulsion in which the sizing agent is
dispersed in water. In such a case, a surfactant can be used as an
emulsifier for the purpose of evenly dispersing the components in
water. The emulsifier at such a stage is not particularly
restricted, so that anionic, cationic, nonionic or the like
emulsifiers can be used. Among these, anionic or nonionic
emulsifiers are preferable, as they have good emulsification
property, and are low cost. Further, as is described below, when
adding a silane coupling agent into the aqueous emulsion, nonionic
emulsifiers are especially preferable, in terms of its stability of
the silane coupling agent in the water and also in terms of the
stability of the physical properties of the molded article.
[0099] Examples of nonionic emulsifiers include polyethylene glycol
type (higher alcohol ethylene oxide adducts, alkylphenol ethylene
oxide adducts, aliphatic ethylene oxide adducts, polypropylene
glycol ethylene oxide adducts and the like), and polyhydric alcohol
type (glycerin fatty acid esters, sorbitol fatty acid esters, fatty
acid alkanolamide and the like). However, the HLB of the nonionic
emulsifier is usually 8 to 20. If a nonionic emulsifier is used
whose HLB is outside of this range, a stable aqueous emulsion may
not be attained.
[0100] Examples of anionic emulsifiers include carboxylate type
(potassium oleate, sodium oleate and the like), sulfonate type
(sodium dodecylbenzene sulfonate, sodium dioctylsulfo succinate and
the like), and sulfate type (sodium lauryl sulfate and the like).
Examples of the neutralizer include potassium hydroxide, sodium
hydroxide, magnesium hydroxide, calcium hydroxide, sodium
carbonate, sodium bicarbonate, potassium carbonate, potassium
bicarbonate, calcium carbonate, calcium bicarbonate, magnesium
carbonate, magnesium bicarbonate, monolaurylamine, trimethylamine,
dimethyl monoethanolamine, triethanolamine, ethylenediamine,
ammonia and the like. Examples of the reducing agents include
sodium sulfite and the like.
[0101] Examples of the emulsification method include a method which
employs a batch provided with a stirrer, a method which employs a
ball mill, a method which employs a shaking apparatus and a method
which employs a high-shear emulsion machine, such as a Gaulin
homogenizer. By setting the emulsification temperature higher than
the softening temperature of the sizing agent to be used, an
aqueous emulsion can be obtained which has sufficient stability.
The time required for emulsification is usually several minutes to
2 hours. After emulsification, an aqueous emulsion can be obtained
by cooling to room temperature. While the aqueous emulsion
concentration is not particularly limited, the emulsion is diluted
with water so as to have the sizing agent concentration of about 5
to 60 wt %.
[0102] For an aqueous emulsion in which a sizing agent is
dispersed, other sizing agents (e.g. vinyl acetate resin emulsion,
urethane resin emulsion, acrylic resin emulsion, epoxy resin
emulsion or the like), a silane coupling agent, and an antistatic
agent can be used in combination as necessary. In addition, a
lubricant or smoothing agent can also be used in combination
therewith.
[0103] Examples of silane coupling agents which can be used include
a silane coupling agent having in the molecule any one of an epoxy
group, a vinyl group, an amino group, a methacrylic group, an
acrylic group and a straight chain alkyl group. The silane coupling
agent can be employed alone, or two or more kinds thereof can be
employed mixed together. Among silane coupling agents, epoxy
silanes, amino silanes and straight chain silanes having in the
molecule an epoxy group, an amino group or a straight chain alkyl
group are particularly preferable. Preferable examples for a epoxy
group contained in the silane coupling agent of epoxy silanes
include glycidyl groups, alicyclic epoxy groups and the like, and
specific examples of the silane coupling agent include A-186,
A-187, AZ-6137, AZ-6165 (trade names) manufactured by Nippon Unicar
Company Limited and the like. Examples of the silane coupling agent
of amino silanes agent include substances having a primary amine, a
secondary amine, or both of these, and specific examples include
A-1100, A-1110, A-1120, Y-9669, A-1160 (trade names) manufactured
by Nippon Unicar Company Limited and the like. Examples of straight
chain alkyl silanes include substances having a hexyl group, an
octyl group or a decyl group and specific examples include AZ-6171,
AZ-6177 (trade names) manufactured by Nippon Unicar Company
Limited, and KBM-3103C (trade name) manufactured by Shin-Etsu
Chemical Co., Ltd. and the like.
[0104] The amount of silane coupling agent is preferably 5 wt % or
less, more preferably 4 wt % or less, with respect to 100 wt % of
the total component amount (total solid amount) excluding water of
the aqueous emulsion in which the sizing agent is dispersed. If the
amount added is more than 5 wt %, cross-linking of the silane
coupling agent proceeds, whereby the carbon fiber bundle become
hard and brittle, to be a reason to form longitudinal cracks and to
lower interfacial adhesion.
[0105] Examples of a method for sizing with an aqueous sizing agent
solution containing a sizing agent such as that described above
include a touch roll method which deposits the aqueous sizing agent
solution by contacting the roll with a carbon fiber bundle
consisting of single carbon fibers after surface transcription by
dipping part of a roll in an aqueous sizing agent solution, and a
dipping method which controls the amount of the aqueous sizing
agent solution deposited by directly dipping a carbon fiber bundle
consisting of single carbon fibers into an aqueous sizing agent
solution and then passing it through a nip roll as necessary.
Between these the touch roll method is preferable. Especially
preferable in terms of the amount of sizing agent deposited or
bundle width control is a method wherein a carbon fiber bundle is
brought into contact with a plurality of touch rolls and then the
aqueous sizing agent solution is deposited over multiple stages.
Subsequently, pre-drying and heat treatment are carried out as
necessary. The specific conditions can be selected as appropriate
so that the carbon fiber bundles can express the desired
properties.
(Sized Carbon Fiber Bundles)
[0106] The carbon fiber bundle according to the present invention
may be in continuous form or may be cut to a prescribed length.
[0107] The mass per unit length of a carbon fiber bundle cut to a
prescribed length is preferably 0.4 to 15 g/m. A carbon fiber
bundle having a mass per unit length less than 0.4 g/m is not only
economically disadvantageous, but also may affect the incorporating
process passing of the carbon fiber bundle in the pellet production
step. On the other hand, if greater than 15 g/m, it becomes more
difficult to completely carry out impregnation of the carbon fiber
bundles into the aqueous sizing agent solution, and it may be more
difficult to produce a carbon fiber bundle having a stable form.
More preferable is 0.6 to 10 g/m, and especially preferable is 0.8
to 8 g/m.
[0108] Although the method of cutting the carbon fiber bundle is
not particularly limited, a rotary cutter method is preferable.
Further, the cut length (length of the carbon fiber bundles) may be
2 to 30 mm, preferably 4 to 24 mm and more preferably 6 to 20 mm. A
rotary cutter method allows the cut length to be regulated by
adjusting the interval between the teeth of the apparatus being
used.
[0109] When cutting by a rotary cutter method, if the carbon fiber
bundle thickness becomes too thick to result cutting defects,
operation impossibility by winding a carbon fiber bundle around the
rotor, and form irregularities after cutting, it is advantageous
for the carbon fiber bundle thickness to be thin. In the case of
the carbon fiber bundle having a large mass per unit length whose
mass per unit length is more than 1.5 g/m, it is important that the
fibers of the carbon fiber bundle are opened up as much as possible
so that the aqueous sizing agent solution can be evenly deposited
as far as the interior portions of the carbon fiber bundle.
Therefore, it is preferable to transfer in a manner with
essentially no twisting of the carbon fiber bundle while
controlling so that the carbon fiber bundle width/thickness
increases using a guide roll, comb guide, spreader bar and the
like.
[0110] However, if the width of a carbon fiber bundle cut to a
prescribed thickness widens, longitudinal cracks form more easily
along the fiber orientation direction, whereby maintaining the form
tends to be more difficult during production or when used after
being produced. This tendency is especially pronounced in carbon
fiber bundles having a large mass per unit length. Therefore, it is
preferable to control the width/thickness of the carbon fiber
bundle of 3 to 10 by adjusting the width of a guide attached to the
rotary cutter. If width/thickness is 3 or more, the occurrence of
miscuts during the cutting process using a rotary cutter can be
suppressed. If width/thickness is more than 10, although miscuts
during cutting are less likely to occur, the thickness becomes too
thin, whereby it is easier for longitudinal cracks of the carbon
fiber bundle to form after cutting to give rise to the risk that
subsequent process passing may deteriorate. Further, to cut a
carbon fiber bundles having a large mass per unit length thinly and
broadly in the manner of a conventional type, the number of carbon
fibers which can be simultaneously treated decreases, so that to
make up for the decreased amount the cutter width needs to be
broadened or the treatment speed has to be increased, thereby
inviting the risk of increasing the load placed on equipment or
decreasing the production efficiency.
[0111] This cutting is preferably conducted on a carbon fiber
bundle which is in a moist state after the aqueous sizing agent
solution has been deposited to the carbon fiber bundle. This
utilizes convergent effect caused by the surface tension of the
aqueous sizing solution and absorption of impact shearing stress
generated during the cutting by soft state in a moist of to prevent
fiber cracking. During the cutting, preferable is a moist state in
which the moisture content of a carbon fiber bundle is 20 to 60 wt
%, especially 25 to 50 wt %. If the moisture content is less than
20 wt %, fiber cracking and fluff are more likely to occur during
cutting. On the other hand, if the moisture content is more than 60
wt %, water is excessively deposited to the single fiber surface,
thereby increasing the risk that single fibers converge in a circle
due to the surface tension of the water, thus causing higher
incidence of miscuts and blade clogging during cutting. In
addition, extra treatments can be carried out prior to cutting
using water or an aqueous sizing agent solution to adjust the
moisture content, as necessary.
[0112] Examples of a method for drying the carbon fiber bundle
after cutting include hot-air drying. If a hot-air drying method is
employed, the bundle is preferably dried while it is transferred
with vibrating, because not only the moisture evaporation
efficiency is improved, but the carbon fiber bundles can be
prevented from adhering together. If the vibration is too
vigorously during drying, fiber cracking may occur more readily,
and the ratio of carbon fiber bundles having a width/thickness of
less than 3 may increase. If the vibration is too weak,
pseudo-adhesion takes place between the fibers, which leads to a
bunched up form. Accordingly, it is necessary to set to appropriate
vibration conditions. In order to not only eliminate the fragmented
carbon fiber bundles, but improve the hot-air flow, it is more
preferable to vibrate and dry while transferring on a vibrating
mesh. Further, to improve drying efficiency, auxiliary means, such
as infrared emission can also be simultaneously used.
(Thermoplastic Resin Composition)
[0113] The carbon fiber bundle according to the present invention
can be formed into a thermoplastic resin composition by kneading
with a thermoplastic resin as the matrix resin. When kneading a
carbon fiber bundle into thermoplastic resin, preferably the carbon
fiber bundles are fed into an extruder in a continuous form or a
form that has been cut into predetermined lengths, and then kneaded
with the thermoplastic resin to form into pellets. The
thermoplastic resin composition according to the present invention
can also provide an arbitrarily shaped molded article (carbon fiber
reinforced composite molded article) by molding in accordance with
a well-known molding method such as injection molding or the
like.
[0114] Concerning preparation of the thermoplastic resin
composition according to the present invention, 3 and 60 wt %, more
preferably 5 to 50 wt %, of the carbon fiber bundle according to
the present invention preferably are blended. By blending 3 wt % or
more of the carbon fiber bundles, the improved effect on mechanical
properties of the molded article is remarkable. On the other hand,
if this exceeds 60 wt %, no further remarkable improvement in
effects is seen, while the process stability during pellet
production may deteriorate and additionally unevenness or the like
may occur in the pellets, whereby there is the risk that quality
stability of the molded article may worsen.
[0115] The thermoplastic resin used as the matrix resin in the
present invention is not particularly restricted, but an
polyolefin-based resin is most preferable, due to its affinity with
the sizing agent deposited to the single fibers of the carbon fiber
bundle. Other examples include at least one selected from the group
consisting of a polycarbonate resin, ABS resin, AS resin,
polyoxymethylene resin, nylon resin, polyphenylene sulfide resin,
polyether sulfine resin, polyether imide resin, polyester resin and
alloy-based resins thereof. Especially when employing a
polyolefin-based resin as the matrix resin, a small amount of
various modified polyolefin-based resins may be added to further
improve the mechanical properties.
[0116] A molded article obtained by molding the thermoplastic resin
according to the present invention has excellent mechanical
properties, as well as excellent production efficiency and economic
cost. Such a molded article is suitable for automotive parts,
housing parts of a portable electric appliance, housing parts of
common home electric appliances and the like.
EXAMPLES
[0117] The present invention will now be explained in further
detail with reference to the following Examples. The measurement
and evaluation of the various properties in the present Examples
was conducted in accordance with the following methods.
(Depth of the Wrinkle on the Surface of Single Fibers of Carbon
Fiber Bundle)
[0118] The depth of wrinkles which are present on the surface of
single fibers of the carbon fiber bundle according to the present
invention was measured from the vertical difference between a
highest portion and a lowest portion in a region defined by 2 .mu.m
of circumferential length.times.1 .mu.m of fiber axial direction
length. The vertical difference was measured based on a surface
shape obtained by scanning the surface of the single fibers with a
scanning atomic force microscope (AFM). Specifically, this was as
follows.
[0119] Several single fibers of a carbon fiber bundle were placed
onto a specimen stage, and fixed at both ends. Dotite was applied
around their periphery to form measurement samples. Employing a
cantilever made from silicon nitride, an atomic force microscope
(Model: SPI 3700/SPA-300 (trade name), manufactured by Seiko
Instruments Inc.) was used to measure in AFM mode by repeatedly
scanning a 2 to 7 .mu.m range in the periphery direction of the
single fibers while slowly moving in 1 .mu.m intervals across the
fibers in a fiber axial direction. The low frequency component of
the obtained measured images was cut by two-dimensional Fourier
transform, and the cut images then underwent an inverse transform.
The vertical difference between the highest portion and the lowest
portion in the region defined by 2 .mu.m of circumferential
length.times.1 .mu.m of fiber axial direction length was then read
and evaluated from the planar image of the cross-section from which
the obtained single fiber curvature had been removed.
(Ratio of Major Axis to Minor Axis (Major Axis/Minor Axis) of
Single Fiber Cross-Sections in Carbon Fiber Bundle)
[0120] After passing the carbon fiber bundle to be measured through
a tube with the inner diameter of 1 mm made from a vinyl chloride
resin, the carbon fiber bundle was cut with a knife into round
slices to be used as specimens. These specimens were then adhered
with their cross-section facing upwards onto a SEM specimen stage,
and sputtered with Au to a 10 nm thickness. The cross-sections were
then observed with a scanning electron microscope (XL20 (trade
name) manufactured by Philips) under the conditions of an
accelerating voltage of 7.00 kV, and operating distance of 31 mm,
for evaluation by measuring the major axis and minor axis of the
single fiber cross-sections.
(Strand Strength and Strand Elastic Modulus)
[0121] These evaluated in accordance with JIS R7601.
(Amount of Pre-Sizing Agent Deposited)
[0122] The amount of the pre-sizing agent deposited on a pre-sized
carbon fiber bundle was measured by the Soxhlet extraction method
using methylethylketone in accordance with JIS R7601.
(Amount of Sizing Agent Deposited)
[0123] The amount of the sizing agent deposited on a sized carbon
fiber was measured by thermal decomposition in accordance with
SACMA method SRM 14-90. When the bundle was pre-sized and then
sized, the amount of the sizing agent deposited was determined by
calculating the increase from the amount of pre-sizing agent
deposited which is already determined separately.
(Moisture Content)
[0124] A carbon fiber bundle cut to a prescribed length was dried
for hour at 110.degree. C. The weight change before and after
drying was taken as the moisture content.
(Si Content)
[0125] A carbon fiber bundle was placed in a platinum crucible with
a known tare and incinerated in a muffle furnace at 600 to
700.degree. C. The incinerated matter is weighed to obtain the ash
content. A fixed amount of sodium carbonate is subsequently charged
thereto, and the resulting mixture is melted by a burner and is
dissolved in DI water (ion-exchange water) to be a constant volume
in a 50 ml plastic graduated flask. The Si amount of this sample is
then obtained by ICP emission spectrometry.
(Evaluation of Mechanical Properties of Molded Articles)
[0126] Tensile strength at break was evaluated in accordance with
JIS K7113, bending strength and elastic modulus were evaluated in
accordance with JIS K7203, and Izod strength (1/8'' notch, 1/8''
reverse notch) was evaluated in accordance with ASTM D256. These
measurements were conducted at room temperature.
<Carbon Fiber Bundles (Raw Materials)>
[0127] The carbon fiber bundles TR50S, TR30L, MR40 and TR40 (trade
names, manufactured by Mitsubishi Rayon Co., Ltd.; non-pre-sized
products) consisting of 12,000 or 50,000 filaments which use
polyacrylic fiber as their raw material, were employed as the raw
materials.
[0128] In addition, the carbon fiber bundle (raw material) CF1 was
prepared according to the following method.
[0129] A spinning solution of an acrylonitrile-based polymer
dissolved in dimethylacetoamide was expelled into a first
coagulation bath containing an aqueous dimethylacetoamide solution
at a concentration of 50 to 70 wt % and a temperature of 30 to
50.degree. C., to thereby form coagulated fibers. Next, the
coagulated fibers were drawn by a fixed length in a second
coagulation bath containing an aqueous dimethylacetoamide solution
at a concentration of 50 to 70 wt % and a temperature of 30 to
50.degree. C. The resulting product was wet-heat drawn by 4-fold or
more to thereby obtain a carbon fiber precursor fiber bundle.
[0130] The ratio of the major axis and minor axis of the carbon
fiber precursor fiber bundle cross-section and the depth of the
wrinkles formed on the surface can be adjusted by changing the
concentration and temperature of the second coagulation bath, as
well as by changing the drawing conditions. A silicon-based oil was
then deposited to maintain the stability of the carbon fiber
precursor fiber bundle.
[0131] Subsequently, a plurality of carbon fiber precursor fiber
bundles were aligned in parallel and placed into a furnace for
flame-proofing treatment. An oxidizing gas such as air heated to
200 to 300.degree. C. was blown onto the carbon fiber precursor
fiber bundles to flame-proof the carbon fiber precursor fiber
bundles, whereby flame-proofed fiber bundles were obtained. Next,
these flame-proofed fiber bundles were placed in a carbonizing
furnace, and carbonized in an inert atmosphere at a temperature of
1,200 to 1,400.degree. C. To improve the affinity with the resin, a
wet electrolytic oxidation treatment was then employed to
incorporate an oxygen-containing functional group onto the
surfaces, whereby the carbon fiber bundle (raw material) CF1 was
produced.
[0132] The properties of the above-described carbon fiber bundles
(raw materials) are shown in Table 1.
TABLE-US-00001 TABLE 1 Carbon fiber bundle (raw material) TR50S
TR30L MR40 TR40 CF1 Depth of the wrinkle (nm) 100 100 10 10 100
Major axis/minor axis 1.08 1.08 1.00 1.00 1.08 Mass per unit length
(g/m) 0.80 3.33 0.60 0.83 0.80 Number of single fibers 12,000
50,000 12,000 12,000 12,000 Si content (ppm) 300 300 140 140 900
Strand strength (MPa) 4700 4400 4500 4500 4600 Strand elastic
modulus (GPa) 240 240 295 235 240
<Pre-Sizing Treatment>
[0133] The above-described carbon fiber bundles (raw materials)
were pre-sized as necessary with a water-dispersible pre-sizing
agent consisting of an epoxy compound, then dried and wound onto a
bobbin. A pre-sizing agent having the following composition was
used adjusting the condition so that the amount deposited was 0.5
wt %.
(Main Agent)
[0134] 50 parts by weight of "Epikote 828" (trade name)
manufactured by Japan Epoxy Resins Co., Ltd. 30 parts by weight of
"Epikote 1001" (trade name) manufactured by Japan Epoxy Resins Co.,
Ltd.
(Emulsifier)
[0135] 20 parts by weight of "Pluronic F88" (trade name)
manufactured by Asahi Denka Co., Ltd.
<Production of Carbon Fiber Bundles I to XVI>
[0136] The carbon fiber bundles (raw materials) shown in Tables 4
and 5 were passed through a opening bar and a carbon fiber
width-regulating bar alternatingly by multiple times to set them to
a certain carbon fiber width, after which they were sized with a
given sizing agent. The sizing agents shown in Tables 4 and 5 were
used among the sizing agents A to J which were prepared by blending
the compounds shown in Table 2 in the ratio shown in Table 3. The
aqueous emulsions were used where the sizing agent concentration
was adjusted as shown in Tables 4 to 6 by regulating the water
content. The touch roll method described below was employed to
deposit the aqueous emulsions.
(Touch Roll Method)
[0137] After surface transcription onto the touch roll surface was
carried out by dipping part of the touch roll in a bath of the
aqueous emulsion, the aqueous emulsion was then deposited by
contacting the carbon fiber bundles (raw materials) onto the touch
roll. This treatment was performed on both the front and back sides
by using two touch rolls.
[0138] Next, the carbon fiber bundles were cut to a prescribed
length (6 mm) by using a rotary cutter and finally dried by being
continuously charged into a floor-vibrating hot-air furnace set at
150.degree. C., to thereby yield carbon fiber bundles I to XVI.
[0139] The employed aqueous emulsions all possessed satisfactory
emulsion stability. The carbon fiber bundle throughput and cutting
process during the sizing treatment were also satisfactory. After
drying, no cracks were formed in any of the carbon fiber bundles.
The evaluated results for the produced carbon fiber bundles I to
XVI are shown in Tables 4 and 5.
TABLE-US-00002 TABLE 2 Product Number Kind (product name) Details
Compound a GF-101 Acid modified polypropylene (aqueous emulsion
containing 10 wt % or less emulsifier) Number average molecular
weight: 4,500 Acid value: 47 mgKOH/g Manufactured by Yoshimura Oil
Chemical Co., Ltd. Compound b GFE-1030 Olefin-based thermoplastic
elastomer (aqueous emulsion containing 10 wt % or less emulsifier)
Vicat softening temperature: 56.degree. C. Manufactured by
Yoshimura Oil Chemical Co., Ltd. Compound c Sepolsion G118
Copolymer of ethylene or propylene and an epoxy-containing monomer
(main component: ethylene-glycidyl methacrylate copolymer) (aqueous
emulsion containing 10 wt % or less emulsifier) Vicat softening
temperature: 70.degree. C. Manufactured by Sumitomo Seika Chemicals
Co., Ltd. Compound d Bondfast 7M Copolymer of ethylene or
propylene, an epoxy-containing monomer and an acrylic ester (main
component: ethylene-glycidyl methacrylate-methyl acrylate
copolymer) (used as an aqueous emulsion adding 20 wt % of an
emulsifier*) Vicat softening temperature: 25.degree. C. or less
Manufactured by Sumitomo Chemical Co., Ltd. Compound e Sepolsion
M220E Copolymer of ethylene or propylene, an acrylic ester and a
monomer containing an acid anhydride group (main component:
ethylene-ethyl acrylate-maleic anhydride copolymer) (aqueous
emulsion containing 10 wt % or less emulsifier) Vicat softening
temperature: 60.degree. C. Manufactured by Sumitomo Seika Chemicals
Co., Ltd. Others OREVAC CA100 Acid modified polypropylene (used as
an aqueous emulsion adding 20 wt % of an emulsifier*) Acid value:
12 mgKOH/g Manufactured by Atofina Japan Hydran HW-930
Urethane-based sizing agent (aqueous emulsion) Manufactured by
Dainippon Ink and Chemicals, Incorporated Epoxy-based Epoxy-based
sizing agent sizing agent (aqueous emulsion, EP1001/EP1002/F88 =
40/40/20 (weight ratio)) EP1001, EP1002: bisphenol A diglycidyl
ether Manufactured by Japan Epoxy Resins Co., Ltd. (trade name)
F88: Pluronic-type polyether (surfactant) Manufactured by Asahi
Denka Co., Ltd. (trade name) A-187 Epoxy silane coupling agent
Manufactured by Nippon Unicar Company Limited A-1100 Amino silane
coupling agent Manufactured by Nippon Unicar Company Limited
*Pluronic F88 (trade name) manufactured by Asahi Denka Co.,
Ltd.
TABLE-US-00003 TABLE 3 Sizing Agent A B C D E F G H I Compound a
GF-101 70 70 70 Compound b GFE-1030 27 30 27 47 Compound c
Sepolsion G118 97 60 Compound d Bondfast 7M 97 Compound e Sepolsion
M220E 37 Others OREVAC CA100 50 Hydran HW-930 97 Epoxy-based sizing
agent 97 A-187 3 3 3 3 3 3 3 A-1100 3 The numbers are represent the
percentage by weight of each component except the water contained
in the respective component.
TABLE-US-00004 TABLE 4 Produced carbon fiber bundle I II III IV V
VI VII VIII Carbon fiber bundle (raw material) TR50S TR30L TR50S
TR50S TR50S TR50S TR50S TR40 Pre-sizing treatment No No No No No No
No No Sizing Kind A A B C D E F A agent Concentration (wt %) 6.0
6.5 6.0 6.0 6.0 6.0 6.0 5.0 Amount deposited (wt %) 2.5 2.7 2.5 2.5
2.5 2.5 2.5 2.0 Moisture content (wt %) 42 40 42 42 42 42 42 40
Carbon fiber bundle width (mm) 8 20 8 8 8 8 8 8 Carbon fiber bundle
width/thickness 4 6 4 4 4 4 4 4 presence of cracks No No No No No
No No No
TABLE-US-00005 TABLE 5 Produced carbon fiber bundle IX X XI XII
XIII XIV XV XVI Carbon fiber bundle (raw material) MR40 CF1 TR50S
TR30L TR50S TR50S TR50S TR50S Pre-sizing treatment No No Yes Yes
Yes No Yes Yes Sizing Kind A A A A B G H I agent Concentration (wt
%) 5.0 6.0 6.0 6.5 6.0 6.0 6.0 6.0 Amount deposited (wt %) 2.0 2.5
2.5 2.7 2.5 2.5 2.5 2.5 Moisture content (wt %) 40 42 42 40 42 42
42 42 Carbon fiber bundle width (mm) 6 8 8 20 8 8 8 8 Carbon fiber
bundle width/thickness 4 4 4 6 4 4 4 4 presence of cracks No No No
No No No No No
Examples 1 to 13 and Comparative Examples 1 to 3
Production of the Pellets and Molded Articles of the Thermoplastic
Resin Composition
[0140] 68 parts by weight of a polypropylene resin (EPR co-polymer
polypropylene; trade name: J-5051 HP, manufactured by Idemitsu
Petrochemical Co., Ltd.) and 12 parts by weight of a modified
polypropylene resin (maleic anhydride co-polymer polypropylene
master batch P503, manufactured by Mitsubishi Chemical Corporation)
were charged into a twin screw extruder heated to 250.degree. C. 20
parts by weight of the carbon fiber bundles shown in Tables 6 and 7
were charged via a side feeder, and the resulting mixture was
kneaded, whereby pellets of the thermoplastic resin composition
were obtained. In none of the examples, there were any residue in
the twin screw extruder.
[0141] The obtained pellets of the thermoplastic resin composition
were manufactured into a molded article by screw inline molder of a
20 mm+.phi. and 35 ounce under conditions of a cylinder temperature
of 250.degree. C. and a die temperature of 60.degree. C. The
mechanical properties of the obtained molded articles are shown in
Tables 6 and 7. The molded articles according to Examples 1 to 13
were superior to those of Comparative Examples 1 to 3 in tensile
strength at break, bending strength and Izod strength. It was
thereby learned that the carbon fiber bundle according to the
present invention possessed satisfactory interfacial adhesion.
TABLE-US-00006 TABLE 6 Example 1 2 3 4 5 6 7 8 Carbon Fiber Bundle
I II III IV V VI VII VIII Tensile Strength at Break (MPa) 110 100
95 95 95 105 100 80 Bending Strength (MPa) 150 140 135 135 134 145
140 115 Bending elastic modulus (MPa) 7500 7400 7300 7400 7300 7400
7400 7200 Izod Strength (1/8'' notch) (J/m) 80 75 75 72 70 85 75 70
Izod Strength (1/8'' reverse notch) (J/m) 240 230 230 220 220 250
240 200
TABLE-US-00007 TABLE 7 Example Comp. Example 9 10 11 12 13 1 2 3
Carbon Fiber Bundle IX X XI XII XIII XIV XV XVI Tensile Strength at
Break (MPa) 75 90 135 125 120 67 65 57 Bending Strength (MPa) 110
125 175 170 165 97 94 80 Bending elastic modulus (MPa) 8400 7200
7500 7400 7400 6800 6800 6300 Izod Strength (1/8'' notch) (J/m) 70
70 85 80 85 67 65 45 Izod Strength (1/8'' reverse notch) (J/m) 190
210 270 270 260 190 180 110
Examples 14 and 15, and Comparative Example 4
Production of the Pellets and Molded Articles of the Thermoplastic
Resin Composition
[0142] 80 parts by weight of a polypropylene resin (EPR co-polymer
polypropylene; trade name: J-5051 HP, manufactured by Idemitsu
Petrochemical Co., Ltd.) were charged into a twin screw extruder
heated to 250.degree. C. 20 parts by weight of the carbon fiber
bundles shown in Table 8 were charged via a side feeder, and the
resulting mixture was kneaded, whereby pellets of the thermoplastic
resin composition were obtained. In none of the examples, there
were any residue in the twin screw extruder.
[0143] The obtained pellets of the thermoplastic resin composition
were manufactured into a molded article by screw inline molder of a
20 mm.phi. and 35 ounce under conditions of a cylinder temperature
of 250.degree. C. and a die temperature of 60.degree. C. The
mechanical properties of the obtained molded articles are shown in
Table 8. The molded articles according to Examples 14 and 15 were
superior to the molded article of Comparative Example 4 in tensile
strength at break, bending strength and Izod strength. It was
thereby learned that the carbon fiber bundle according to the
present invention possessed satisfactory interfacial adhesion.
TABLE-US-00008 TABLE 8 Comp. Example Example 14 15 4 Carbon Fiber
Bundle XI I XVI Tensile Strength at Break (MPa) 90 70 40 Bending
Strength (MPa) 105 90 56 Bending elastic modulus (MPa) 7300 7300
5100 Izod Strength (1/8'' notch) (J/m) 80 70 50 Izod Strength
(1/8'' reverse notch) (J/m) 140 110 90
INDUSTRIAL APPLICABILITY
[0144] The present invention provides a thermoplastic resin
composition, suitable for producing a molded article (carbon fiber
reinforced composite molded article). Such a molded article has
excellent mechanical properties, and is also superior in terms of
production efficiency and economic cost, and is thus suitable for
automotive parts, housing parts of a portable electric appliances,
housing parts of common home electric appliances and the like.
* * * * *