The present invention relates to fiber-reinforced thermoplastic resin
pellets that use natural discontinuous fiber as reinforcing fiber and a manufacturing
method thereof. Furthermore, the present invention relates to the automobile parts
manufactured using the pellets.
Recently, fiber-reinforced resin in which vegetable fibers such as
wood pulp, hemp, and hemp palm are used as reinforcing fiber has been actively developed.
Nowadays, awareness of waste pollution has been increasing. The reason for this
will be described hereinafter. Natural fiber does not cause waste pollution even
if it is used for land filling as it is an environment-friendly material. In addition,
when natural fiber is burnt, it generates a great deal of combustion energy allowing
high energy recovery without causing secondary pollution such as residual ash or
flue gas pollution.
However, natural fiber is a discontinuous fiber differing from continuous
fibers such as glass fiber, carbon fiber, metal fiber, and various synthetic fibers
that have conventionally been used as reinforcing fibers for fiber reinforced-resin.
Therefore, a special technique is required to manufacture molding resin pellets
mixed with natural fiber that exhibit the characteristics of long fiber. For example,
a continuous fiber strand is impregnated in a molten resin bath continuously and
pultruded, and cooled to solidify the resin and then cut into pellets of an arbitrary
length. This method is widely used to manufacture fiber-reinforced resin pellets
continuously with high productivity. However, even if discontinuous natural fibers
are twisted into yarns, the strength of the spun yarns is insufficient to be processed
in a molten resin bath, discontinuous fiber spun yarns are often broken due to the
release of discontinuous fiber in the resin bath when the spun yarns are impregnated
and pultruded in the molten resin bath. This makes it difficult to continue stable
For example, methods for manufacturing fiber-reinforced resin pellets
using discontinuous natural fiber as a reinforcing fiber described are proposed
hereinafter, but the methods have both merits and demerits.
(1) A method in which natural fiber is kneaded to mix it homogeneously in molten
thermoplastic resin using a roll kneader and then the mixture is cooled to solidify,
and the product is crushed to form resin pellets (J-P-A No. 108161/1982). By applying
this method, molding material in which discontinuous fiber is dispersed homogeneously
in matrix resin is obtained. However, the molding material has disadvantages in
that the handling process, including the molding process, is difficult and quality
stability of the molded product is poor due to irregularity in the size of the resin
(2) A method in which discontinuous fiber is spun to form spun yarn, spun yarn
is processed to form fabrics or wovens, nonwovens, or mats, the processed product
is impregnated in a molten resin bath and then cooled to solidify, and the cooled
product is cut into the product of a suitable configuration and size to form resin
pellets. (J-P-A Nos. 28307/1983, 7307/1991, 30916/1991, and 41280/1997). This method
is suitable for applications in which the product is used for secondary molded material
such as a resin-impregnated sheet, but when the product is used in the form of a
pellet, the product that has been cooled and solidified is cut into pellets of a
suitable configuration and size, and the cutting process requires much working and
results in a low productivity. Furthermore, the cutting process is involved in a
problem of much loss, and dust generated in cutting process causes pollution of
the working environment.
(3) A method in which molten resin and discontinuous fiber are kneaded using
a kneader or a kneading extruder and then the molten mixture is extruded, cooled,
and solidified to form a rod product, afterwards, the rod product is cut into pellets
of an arbitrary length (J-P-A Nos. 146945/1987, 146947/1987, and 290453/1991). This
method has disadvantages in that it is difficult to feed cotton-like fiber into
a kneading extruder, and the reinforcing fiber is subjected to thermal deterioration
when resin is heated for melt kneading, and reinforcing fiber is subjected to mechanical
damage due to the kneading force. As a result, the reinforcing effect is poor. In
particular, because heat decomposition usually begins at a temperature range of
150 to 180°C in the case of vegetable fibers such as wood pulp and linen, thermoplastic
resin that does not cause such problems must be selected for composite forming depending
on the fiber type and kneading time. Therefore, the freedom in selection of matrix
resin is limited. Furthermore, because such resin with a low melting point is generally
not strong, the application of the fiber-reinforced resin molded product is naturally
(4) A method in which composite fiber strands comprising reinforcing spun yarn
and thermoplastic resin fiber is formed, and the composite fiber strand is heated
to melt the thermoplastic resin fiber, it is cooled and solidified, and then the
solidified product is cut into pellets of a suitable length (J-P-A No. 163002/1992).
To apply this method, thermoplastic resin fiber is manufactured previously or mixed
yarn containing reinforcing fiber and thermoplastic resin fiber is manufactured,
the manufacturing process requires a lot of work, and this method is troublesome.
Furthermore, insufficient impregnation can occur causing void defects depending
on the heat melting conditions for melting the thermoplastic resin fiber.
(5) A method in which a reinforcing fiber strand is impregnated with molten
thermoplastic resin, cooled and solidified, and then cut into pellets of a suitable
length (for example, J-P-B Nos. 37694/1988, 57407/1994 and J-P-ANos. 178411/1989,
119807/1992). This literature disclose a case where jute (linen fiber) can be used
as a reinforcing fiber, however, they mainly disclose cases where continuous fiber
is used as a reinforcing fiber. This literature does not reveal any detailed problem
arising when discontinuous fiber is mixed with thermoplastic resin as a reinforcing
fiber to form composite material.
DE-A-197 11 247 discloses the use of hybrid slivers of natural fibers
and low-melting matrix fibres to produce long fibre pellets.
The inventors of the present invention are interested in a natural
discontinuous fiber that has attracted much attention as a reinforcing fiber in
the above-mentioned known circumstances, and have developed a technique for manufacturing
discontinuous fiber reinforced thermoplastic resin pellets that solve problems of
conventional resin pellets as described hereinbefore caused in the manufacturing
process of molding thermoplastic resin pellets consisting of a composite material
containing reinforcing fiber in thermoplastic resin. Particularly, all the problems
in the continuous manufacturing process, in quality stability (homogeneous impregnation
and deterioration prevention of reinforcing fiber), and in the strength characteristic
of the molded product are to be solved.
Accordingly, it is an object of the present invention to provide discontinuous
fiber reinforced thermoplastic resin pellets that satisfy the conditions required
for continuous production, quality stability of the molded material (homogeneous
impregnation and deterioration prevention of reinforcing fiber), and the strength
characteristics of the molded product, and a manufacturing method thereof.
According to the present invention, there are provided natural fiber-reinforced
thermoplastic resin pellets comprising thermoplastic resin and strand comprising
a plurality of spun yarns of natural fiber twisted in a range from 10 to 200 turns/m,
wherein the spun yarn is 172,24·10-6 kg/m to 2756·10-6 kg/m
(No. 5 to 80 counts) in diameter.
Further, there is provided a method for manufacturing natural fiber-reinforced
thermoplastic resin pellets comprising the steps of: impregnating step for impregnating
in a thermoplastic resin bath, a plurality of spun yarns of natural fiber being
172,24·10-6 kg/m to 2756·10-6 kg/m (No. 5 to 80 counts) in
diameter, pultruding step for pultruding the spun yarns with twisting 10 to 200
turns/m to obtain natural fiber-reinforced thermoplastic, and pelletizing step for
pelletizing the natural fiber-reinforced thermoplastic resin.
Moreover, there are provided natural fiber-reinforced thermoplastic
resin-made automobile parts manufactured using natural fiber-reinforced thermoplastic
resin pellets as the molding material.
Other objects and advantages of the present invention will become
apparent from the detailed description to follow taken in conjunction with the appended
As described hereinbefore, in the present invention, molten thermoplastic
resin is impregnated in discontinuous natural fiber and the impregnated fiber is
pultruded, and then cut into fiber-reinforced thermoplastic resin pellets of a suitable
length. In the manufacturing process, the spun yarn that is formed by twisting natural
fiber properly is used wherein the yarn number count of the spun yarn is specified,
a plurality of spun yarns are paralleled to form a paralleled yarn, the paralleled
yarn is twisted properly and impregnated with thermoplastic resin, the impregnated
yarn is pultruded and cooled and solidified, and then it is cut into fiber-reinforced
resin pellets of a suitable length. By employing this method, long fiber-reinforced
thermoplastic resin pellets in which discontinuous natural fiber is used as a reinforcing
fiber is manufactured continuously with high productivity.
The fiber-reinforced thermoplastic resin pellets of the present invention
obtained by this method are characteristic based on the feature of the manufacturing
process described hereinbefore in that a plurality of discontinuous fiber spun yarns
that have been twisted properly is embedded in thermoplastic resin.
Examples of natural fiber used in the present invention include flax,
ramie, abaca, sisal, jute, hemp, kenaf, Boehmeria nipponivea fiber or Japanese ramie,
coir, cotton, kapok, hemp palm, rice straw, wheat straw, pineapple fiber, wool,
and silk. These fibers are used alone individually, or a plurality of these fibers
are used in combination as required. When a plurality of natural fibers are used
combinedly, blended yarn that is formed by blending fibers in a spinning process
may be used or a blended strand that is formed by blending different spun yarns
in a paralleling process may be used. Furthermore, it is possible to combine a plurality
of types of spun yarns when thermoplastic resin is impregnated in a plurality of
spun yarns (bundle) to form a composite. Furthermore, it is possible to mix a small
amount of discontinuous synthetic fiber with natural fiber depending on the case.
The thickness of spun yarn to be used is preferably of 172,24·10-6
kg/m to 2756·10-6 kg/m (a No. 5 to 80 count) (spun yarn with a weight
of 1 kg and a length of 29,029 m is a No. 1 count) represented by a jute yarn number
count according to JIS L0101 (based on a given length), thin spun yarn is preferably
used from the view point of good penetration of thermoplastic resin, and 241,14·10-6
kg/m to 2756·10-6 kg/m (a No. 7 to 80 count), or preferably 344,48·10-6
kg/m to 1378·10-6 kg/m (a No. 10 to 40 count) is used.
If thin yarn thinner than 172,24·10-6 kg/m (a No. 5 count)
is used, the strength of the single yarn is too weak to withstand the drawing force,
the yarn can be broken due to drawing tension thus causing difficulty in stable
continuous manufacturing. On the other hand, If yarn thicker than 2756·10-6
kg/m (a No. 80 count) is used, impregnation of resin is insufficient, and when the
impregnated strand is cut using a pelletizer, the fluffing caused results in a polluted
working environment, or a bridging of pellets occurs due to fluff at the hopper,
thus resulting in poor productivity of the molded product and insufficient mechanical
properties of the molded product when the obtained resin pellet is used.
Next, the detailed manufacturing method will be described hereinafter.
Natural discontinuous fiber is twisted to form a spun yarn, a plurality of spun
yarns are paralleled, the paralleled yarns are passed through a molten thermoplastic
resin bath where thermoplastic resin extruded from an extruder is filled. The plurality
of spun yarns is twisted in the molten thermoplastic resin bath to form a strand.
In the molten thermoplastic resin bath, the molten thermoplastic resin is impregnated
into the spun yarn strand. The spun yarn strand impregnated with thermoplastic resin
is pultruded through a nozzle and cooled, and it is cut to form fiber-reinforced
thermoplastic resin pellets containing a natural discontinuous fiber of a certain
At that time, it is preferable to control the impregnating duration
from the time when the spun yarn strand enters the molten thermoplastic resin bath
to the time when it is pultruded through the nozzle to be less than 10 seconds,
or preferably less than 5 second. If the impregnating duration is excessively long,
the duration while the natural fiber is being subjected to heat in the molten thermoplastic
resin bath is also too long, and heat deterioration of the fiber can be caused.
On the other hand, if the impregnating duration is excessively short, the impregnation
is not sufficient. The time is preferably equal to 0.1 seconds or longer, or better
still equal to 0.15 seconds or longer.
During the process in which the spun yarn strand is impregnated in
the bath, passed through the bath, and pultruded from the bath, the paralleled spun
yarns are twisted with a pitch of 10 to 200 turns/m, preferably 15 to 150 turns/m,
or better still 20 to 120 turns/m. The molten thermoplastic resin penetrates into
the spun yarn strand due to proper twisting, and the proper twisting brings about
good impregnation. Even if some spun yarns are partially loosened to result in released
yarn, such yarns are twisted together with other spun yarns to form a strand. Therefore,
the spun yarn strand will not be broken in the impregnating bath, and is pultruded
stably to form a resin-impregnated continuous strand. The continuous manufacturing
process will not suffer from stoppage problems.
Spun yarns may be Z twist yarns or S twist yarns, but usually Z twist
yarns are employed. In the present invention, for example, when Z twist yarns are
used, it is preferable that the paralleled Z twist yarns are S-twisted in the molten
thermoplastic resin bath, because Z twist yarns are untwisted slightly during the
impregnating process and the molten resin penetrates easily into the spun yarn strand.
However, when spun yarns of a small yarn number count are used, because the untwisting
of the spun yarn can result in insufficient strength, it is preferable that paralleled
Z twist yarns are z-twisted to secure sufficient strength. Based on the above, it
is desirable that Z-twisting is employed for spun yarns with 172,24·10-6
kg/m to 688,97·10-6 kg/m (No. 5 to 20 counts) to supplement the insufficient
strength, and on the other hand S-twisting is employed for spun yarns with 723,41·10-6
kg/m to 2756·10-6 kg/m (No. 21 to 80 counts) to improve penetration.
The impregnated strand is cooled downstream after pultruding to solidify
the impregnated thermoplastic resin, and then cut to form fiber-reinforced resin
pellets containing discontinuous natural fiber of a suitable length. The fiber-reinforced
resin pellets obtained as described hereinbefore contains natural fiber spun yarn
and a twisted strand comprising a plurality of spun yarns in a solidified matrix
thermoplastic resin because of the characteristics of the manufacturing method.
Such a distribution of natural fibers in pellets is different from that of reinforcing
fiber in known continuous long fiber-reinforced resin pellets and in another type
of fiber-reinforced resin pellet that is formed by a method in which woven or knitted
fabric formed using discontinuous fiber spun yarn is impregnated with resin and
then cut to form resin pellets.
In the fiber-reinforced resin pellets of the present invention, discontinuous
natural fiber is doubly twisted resultantly in the resin. Therefore, the length
of natural fiber contained in a pellet is slightly longer because of the double
twisting with respect to the pellet length. Therefore, it is possible to handle
pellets containing longer natural fiber as a reinforcing material advantageously
(usually, long pellets cause bridging at a hopper in the molding process).
If the number of twistings in the above-mentioned impregnating and
drawing process is less than 10 turns/m, the improvement in tensile strength due
to twisting is insufficient, short fiber is released from spun yarn and mixed in
the molten resin bath to cause increased drawing resistance and break of the natural
fiber spun yarn strand. On the other hand, if the number of twistings is as excessive
as 200 turns/m, the penetration of resin into the spun yarn strand is insufficient
and results in a poor quality of fiber-reinforced resin pellets and a poor property
of the molded product.
The type of thermoplastic resin used as the matrix resin in the present
invention is not limited particularly, and any thermoplastic resin can be used.
For example, polyolefin resin such as polypropylene (PP), high density polyethylene
(HDPE), linear low density polyethylene (LLDPE), low density polyethylene (LDPE);
polyamide resin such as polyamide 4, polyamide 6, polyamide 66, polyamide 6, polyamide
10, polyamide 11, polyamide 12, and aromatic polyamide; polyester resin such as
polyethylene-terephthalate (PET) and polybutylene-terephthalate (PBT); polycarbonate
resin; polystyrene resin; acrylic resin; AS resin; ABS resin; PPS resin; POM resin
may be used in the form of homopolymers or copolymers, or in the form of blend polymers
containing two or more polymers. The thermoplastic resin to be used may be arbitrarily
selected in consideration of the required property of the fiber-reinforced resin
molded product to be obtained as the final product.
However, because, in the present invention in which natural fiber
is used as a reinforcing fiber, natural fiber is decomposed and deteriorated thermally
resulting in a damaged reinforcing function of the material when natural fiber is
exposed to a high temperature during molding, it is preferable to use thermoplastic
resin with a melting or softening temperature less than 220°C, more preferably less
than 220°C, and further preferably less than 180°C.
Among the above-mentioned thermoplastic resins, polyolefin resin such
as polypropylene (PP), high density polyethylene (HDPE), linear low density polyethylene
(LLDPE), low density polyethylene (LDPE), polymer of α-olefin such as butene-1,
hexene-1, and octane-1 or a copolymer of these olefins, modified polyolefin resin
modified with unsaturated carboxylic acid or derivatives thereof; ethylene-vinylacetate
resin (EVA); or blend resins containing two or more polymers described hereinbefore
may be used in view of the balance between the product property and cost.
Examples of the above-mentioned unsaturated carboxylic acid or derivatives
thereof used for modification include acrylic acid, methacrylic acid, maleic acid,
itaconic acid, fumaric acid, esters of these acids, maleic anhydride, and itaconic
anhydride. Among these substances,it is preferable to use maleic anhydride and glycidyl
Various modified resins that are compatible with natural fibers and
thermoplastic resin may be added to thermoplastic resin to improve the adhesion
to the natural fiber. Effective examples of modified resin include, for example,
polyolefin modified with maleic anhydride, polyolefin modified with oxazoline, and
polyolefin modified with glycidyl methacrylate for polyolefin resin. The property
of the molded product can be further improved by adding an adequate amount of these
substances. The preferable amount of modified polyolefin resin to be added is 0.1
to 15 % by weight, preferably 0.2 to 12 % by weight, and more preferably 0.5 to
10 % by weight.
An inorganic filler or various additives may be added to the above-mentioned
thermoplastic resin depending on the application of the molded product and the required
property. Examples of inorganic filler include talc, calcium carbonate, calcium
hydroxide, barium sulfate, mica, calcium silicate, clay, kaolin, silica, alumina,
wollastonite, magnesium carbonate, magnesium hydroxide, titanium oxide, zinc oxide,
and zinc sulfide. These materials may be used solely or in combination as required.
Examples of various additives include dispersant, lubricant, flame
retardant, anti-oxidant, antistatic agent, anti-light agent, ultraviolet ray absorbing
agent, carbon black, crystallization accelerator (nucleating agents), plasticizer,
water absorbent, pigment, and dye. These materials may be used solely or in combination.
The pellet length of the fiber-reinforced thermoplastic resin pellet
in accordance with the present invention is not particularly limited, but a pellet
length of 2 to 24 mm is preferably used in view of the moldability and property
of the molded product. A pellet length shorter than 2 mm results in the molded product
with an insufficient property because of the short fiber length of thereinforcing
fiber. On the other hand, a pellet length longer than 24 mm causes bridging at a
hopper during the molding process and results in a difficult molding process. In
view of these merits and demerits, the pellet length is preferably 3 to 18 mm, and
more preferably 3 to 15 mm.
The pellet diameter is not particularly limited, but ranges from 1
to 5 mm, preferably 2 to 4 mm in view of the productivity and handling of the pellets
during the molding process.
The preferable relation between the pellet length (L) and the pellet
diameter (D) is represented by the aspect ratio. The preferable L/D ranges from
1 to 6. An L/D of less than 1 results in vertical cracking of the pellet during
pelletizing, causing fluffing of the reinforcing natural fiber, and results in difficulty
in handling. On the other hand, an L/D larger than 6 not only results in reduced
pellet productivity because the pellet is too long and thin, but also results in
the breaking of the pellet due to the jamming of pellets in a screw when it is used
for injection molding. The reinforcing natural fiber is shortened due to breaking,
and the breaking results in a poor mechanical property of the molded product. In
view of the above, the preferable L/D ranges from 2 to 5.
The natural fiber used as a reinforcing fiber in the present invention
is generally apt to deteriorate thermally from a temperature of approximately 150°C
or higher, though this depends on the type of the natural fiber. Therefore, it is
desirable that attention is paid to prevent the thermal deterioration of the natural
fiber when thermoplastic resin with a high melting point or softening point is used.
A low molten resin temperature is desirable when thermoplastic resin is impregnated
in natural fiber, and a suitable temperature should be selected in view of the balance
between the penetration of the resin into the natural fiber and the melt viscosity
of resin that affects the drawing speed of the strand (fiber-reinforced resin strand
impregnated with resin).
When thermoplastic resin is selected, thermoplastic resin with a melt
viscosity suitable for impregnation in a natural fiber strand is selected, and the
thermoplastic resin is heated to a sufficiently high temperature in the allowable
range so that the melt viscosity becomes sufficiently low. Furthermore, the type
of thermoplastic resin should be selected in view of the mechanical property of
the molded product. For example, in the case of polypropylene resin, the melt flow
rate (MFR: 230°C, 21,17N (2.16 kgf)) is in a range from 10 g/10 min to 200 g/10
min, preferably in a range from 20 g/10 min to 150 g/10 min, and more preferably
in a range from 30 g/10 min to 100 g/10 min. The molten resin temperature is in
a range from 230 to 280°C, preferably in a range from 240 to 260°C, and more preferably
in a range from 245 to 255°C.
An MFR of the polypropylene resin smaller than the above-mentioned
range results in reduced productivity of pellets that contain natural fiber and
results in insufficient impregnation of resin into natural fiber even though the
pellets can be manufactured. At that time, natural fiber is released partially from
the obtained resin pellet resulting in poor handling, the natural fiber is dispersed
insufficiently in the matrix resin when the molded product is manufactured, and
the scattering of property becomes significant. On the other hand, an MFR larger
than the above-mentioned range results in the disadvantage of poor material performance
such as strength, modulus, and heat resistance.
The preferable natural fiber content in thermoplastic resin in accordance
with the present invention is 10 to 65 % by volume, and more preferably 12 to 60
% by volume. If the natural fiber content is smaller than 10 % by volume, the absolute
quantity of natural fiber is insufficient and the property reinforcing function
is exhibited insufficiently. On the other hand, if the natural fiber content is
larger than 65 % by volume, the impregnation of resin into natural fiber is apt
to be insufficient, natural fiber is apt to be released from resin pellets to cause
a problem in handling and a problem of bridging at part of a hopper of an injection
molding machine. Furthermore, the high natural fiber content causes insufficient
dispersion of reinforcing fiber in the molded product and the scattering of property
When resin pellets of the present invention are used as the molding
material, a method may be employed, in which composite resin pellets with a high
reinforcing fiber content, which is used as the master batch, is dry-blended with
resin pellets formed of the same resin as the matrix resin of the composite resin
pellets or a different resin compatible with the matrix resin of the composite resin
to adjust the reinforcing fiber content to the desired value.
Resin pellets of the present invention are suitably used for manufacturing
automobile parts (for example, inner panel), from which a large amount of waste
is generated. The automobile parts obtained as described hereinbefore is excellent
in strength and is helpful in reducing waste pollution.
The present invention will be described in detail hereinafter with
reference to examples. However, the present invention is by no means limited to
the examples described hereinafter, and may be modified without departing from the
scope thereof, and these modifications are included in the technical scope of the
100 part by weight of homo-polypropylene resin with a density of 0.91
g/cm3, MFR (230°C, 21,17N (2.16 kgf)) of 60 g/10 min, and with a melting
point of 165°C was blended with 3 parts by weight of maleic anhydride-modified polypropylene
resin [product of Sanyo Kasei Kogyo, brand name: Umex 1001] with an acid number
of 26 mgKOH/g, density of 0.95 g/cm3, molecular weight of 40,000 (weight
average molecular weight by GPC method) to form blended resin pellets.
Spun yarn of jute with 103,34·10-6kg/m; 241,14·10-6
kg/m; 516,72·10-6 kg/m ; 1240·10-6 kg/m ; 2067·10-6
kg/m and 3445·10-6 kg/m (No. 3, 7, 15, 36, 60, and 100 counts) of the
first type D specified in JIS L2401 was used as the natural fiber.
A spun yarn strand was impregnated in a bath containing molten resin
formed by melting the above-mentioned resin pellets at 250°C where the spun yarn
strand was twisted under the conditions listed in table 1 and pultruded at a line
speed of 15 m/min (resin bath passing time of the spun yarn was about 0.8 seconds).
The obtained fiber-reinforced resin was cooled and solidified, and cut into 9 mm
lengths. As described hereinbefore, fiber-reinforced resin pellets with a diameter
of 3 mm and a length of 9 mm were manufactured, and one-hour continuous production
(pultruding of strand) was evaluated. Furthermore, the degree of impregnation of
resin into fiber-reinforced resin pellet was evaluated by visual observation, and
also the release of fiber from the cross section of each pellet was observed to
evaluate the degree of impregnation, and the results are listed in table 1.
[Impregnation of resin]
o○:there is a non-impregnated portion
and the release of fiber from the cross section is not found.
○: there is a non-impregnated portion apparent, but slight release of fiber
from the cross section is found.
×: there is a non-impregnated portion apparent, and remarkable release
of fiber from the cross section is found.
All the examples listed in Table 1 satisfy the conditions specified
in the present invention. The strand was not broken during one-hour of continuous
operation, fiber-reinforced resin pellets were manufactured smoothly, and impregnation
of resin of the obtained pellets was good. On the other hand, in the comparative
examples 1 and 4 in which natural fiber spun yarn with an insufficient yarn number
count was used, the strand was broken due to insufficient strength of the spun yarn
strand to withstand the impregnating tension and continuous operation was interrupted
though impregnation of resin was good. In the comparative examples 2, 3, and 6 in
which natural fiber spun yarn with an excessively large yarn number count was used,
insufficient impregnation of resin was found.
In the comparative example 5 in which spun yarn with suitable yarn
number count was used, but the spun yarn strand was not twisted during the running
of the impregnating process, the strand was broken. On the other hand, when the
spun yarn strand was twisted excessively (comparative example 7), insufficient impregnation
of resin was clearly found though the stability of running the impregnating process
A flat plate with a thickness of 3.2 mm, a width of 100 mm, and a
length of 200 mm was manufactured using an injection molding machine (Japan Steel
Works, brand name: "JSW J200SA") under a resin temperature of 180°C and a mold temperature
of 50°C using fiber-reinforced resin pellets obtained in the above-mentioned example
1 as the molding material. The bending property and impact property were tested
according to the measurement method described hereinafter and the result listed
in table 2 was obtained.
As a reference example, a flat plate of the same size as described
hereinbefore was manufactured by a method in which 20% of the glass fiber that had
been treated so as to be used suitably for polypropylene resin is mixed with polypropylene
resin that is the same as that described hereinbefore served as the matrix resin,
the mixed resin material was used to manufacture glass fiber-reinforced polypropylene
resin pellets using a kneading extruder, and the resin pellets are used as molding
material to manufacture the flat plate. The flat plate was subjected to the same
test as applied in Table 1.
Flexural strength and flexural modulus: JIS K7203
Izod impact value: JIS K7110
Density: JIS K7112
Example 1Reference ExampleDensity1.061.04Flexural strength (Mpa)68110Flexural modulus (Gpa)4.94.1Izod impact value (notched: kJ/m268
The present invention has the constitution as described hereinbefore,
natural discontinuous fiber, which has attracted attention for use as a reinforcing
fiber, is used, fiber-reinforced thermoplastic resin pellets that satisfy the quality
stability of molding material (homogeneous impregnation, deterioration prevention
of reinforcing fiber) and strength performance of the molded product can be manufactured
continuously with excellent productivity.
The foregoing invention has been described in terms of preferred embodiments.
However, those skilled, in the art will recognize that many variations of such embodiments
exist. Such variations are intended to be within the scope of the present invention
and the appended claims.
Naturfaserverstärkte thermoplastische Harzpellets, umfassend ein thermoplastisches
Harz und einen Strang, welcher eine Vielzahl von in einem Bereich von 10 bis 200
Drehungen/m verdrehten Spinngarnen aus Naturfaser umfaßt, wobei das Spinngarn
im Durchmesser 172,24 x 10-6 kg/m bis 2.756 x 10-6 kg/m (Nr.
5 bis 80 Feinheit) ist.
Verfahren zur Herstellung von naturfaserverstärkten thermoplastischen Harzpellets,
umfassend die Schritte:
einen Imprägnierschritt zum Imprägnieren einer Vielzahl von Spinngarnen aus
Naturfaser, welche im Durchmesser 172,24 x 10-6 kg/m bis 2.756 x 10-6
kg/m (Nr. 5 bis 80 Feinheit) sind, in einem Bad mit thermoplastischem Harz,
einen Pultrusionsschritt zum Strangziehen der Spinngarne mit Verdrehungen von
10 bis 200 Drehungen/m, um naturfaserverstärktes thermoplastisches Harz zu erhalten,
einen Pelletierschritt zum Pelletieren des naturfaserverstärkten thermoplastischen
Verwendung der naturfaserverstärkten thermoplastischen Harzpellets nach Anspruch
1 als die Formmasse zur Herstellung eines aus naturfaserverstärktem Harz hergestellten
Natural fiber-reinforced thermoplastic resin pellets comprising thermoplastic
resin and strand comprising a plurality of spun yarns of natural fiber twisted in
a range from 10 to 200 turns/m, wherein the spun yarn is 172,24·10-6
kg/m to 2756·10-6 kg/m (No. 5 to 80 counts) in diameter.
A method for manufacturing natural fiber-reinforced thermoplastic resin pellets
comprising steps of:
impregnating step for impregnating in a thermoplastic resin bath, a plurality
of spun yarns of natural fiber being 172,24·10-6 kg/m to 2756·10-6
kg/m (No. 5 to 80 counts) in diameter,
pultruding step for pultruding the spun yarns with twisting 10 to 200 turns/m
to obtain natural fiber-reinforced thermoplastic resin, and
pelletizing step for pelletizing the natural fiber-reinforced thermoplastic
The use of natural fiber-reinforced thermoplastic resin pellets according to
claim 1 as the molding materialfor the manufacture of a natural fiber-reinforced
resin-made automobile part.
Pastilles de résine thermoplastique renforcée par une fibre naturelle discontinue
comprenant une résine thermoplastique et un fil comprenant une pluralité de filaments
filés d'une fibre naturelle torsadée dans une gamme de 10 à 200 torsades/m, dans
lesquelles le filament filé a un diamètre de 172, 24.10-6 kg/m à 2756.
10-6 kg/m (N° de finesse de 5 à 80).
Procédé de fabrication de pastilles de résine thermoplastique renforcée par
une fibre naturelle discontinue comprenant les étapes :
une étape d'imprégnation pour imprégner dans un bain de résine thermoplastique,
une pluralité de filaments filés d'une fibre naturelle ayant un diamètre de 172,24.10-6
kg/m à 2756.10-6 kg/m (N° de finesse de 5 à 80),
une étape d'extrusion par étirage pour extruder par étirage les filaments filés
avec une torsade de 10 à 200 torsades/m pour donner une résine thermoplastique renforcée
par une fibre naturelle, et
une étape de pastillage pour mettre sous forme de pastilles la résine thermoplastique
renforcée par une fibre naturelle.
Utilisation des pastilles de résine thermoplastique renforcée par une fibre
naturelle selon la revendication 1 comme matériau de moulage pour la fabrication
d'une pièce automobile faite de la résine renforcée par une fibre naturelle.