Note: Descriptions are shown in the official language in which they were submitted.
~38S~8
BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates to a composite material com-
position using wastepaper obtained by first cutting wastepaper
with no pretreatment and then mixing it with a thermoplastic
resin, and a method of producing such composition.
Description of Prior Art
Heretofore, synthetic resins either with or without
an inorganic filler or woodmeal and compressed boards using
regenerated wastepaper have been available as boarding material
for interior parts of automobilesO
However, synthetic resin moldings are generally un-
suited for use as interior parts of automobiles because of
poor heat resistance and flame retardancy.
The woodmeal-incorporated synthetic resins have had
problems in mechanical strength such as tensile strength,
bending modulus of elasticity, bending strength and impact
- strength.
In the case of synthetic resins provided with an
inorganic filler such as talc or calcium carbonate, for improv-
ing said defective properties of said synthetic resins alone or
woodmeal-incorporated synthetic resins, although heat resistance
and flame retardancy as well as mechanical strength are improved,
linear shrinkage in molding such resins (0.8 - 1.5%) is not
much different from that of the normal synthetic
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1~3~588
resins (1-2%), so that the molded parts therefrom, particularly
those exceeding 1,000 mm in length such as for example front
boards for automobiles, are elevated in dimensional tolerance
to discommode mating or combined use of moldings.
s
As for the compressed boards utilizing regenerated
wastepaper, they are variable in water content as they absorb
moisture from the air, and they are also subject to extention
or shrinkage in accordance with the change of water content,
resulting in irregular deformations such as warp or torsion.
~urther, such compressed boards, as compared with synthetic
resins, have a certain limitation in bending or drawing work
and are unsuitable for use to make the moldings with an in-
tricate configuration.
Generally, such compressed boards have been produced
by first beating wastepaper in water, subjecting the beaten
wastepaper to a paper-making process, drying the thus processed
wastepaper and then subjecting dried wastepaper to compression
molding. According to this method, large equipment must be provided
for performing such beating, paper processing and drying, and
naturally high equipment costs result. Also, a large volume of
industrial water is required for beating and paper processing
of wastepaper, and this necessitates anti-pollution equipment
for treating waste water released from said processes.
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1~3~88
SUMMARY OF THE INVENTION
This invention provides a composite material
composition by utilizing wastepaper such as old newspaper,
corrugated board, cardboard, and scrap paper, which usually
are thown away in huge volumes every day, so as to contribute
to saving of pulp resources as well as saving of petroleum
resources by lessening the amount of use of petroleum-derived
resins for said type of compositions.
The present invention principally provides a
composite material composition using wastepaper which composition
has the properties suited for use in the manufacture of automobile
parts.
The present invention also provides a composite
material composition using wastepaper which composition is free
of the deficiencies of heat resistance and flame retardancy
of synthetic resins, mechanical strength of woodmeal-blended
synthetic resins and linear shrinkage in molding of inorganic
filler-incorporated synthetic resins.
The present invention also provides a composite
material composition using wastepaper which composition does not
absorb moisture from the air as do compressed boards using
regenerated wastepaper and hence is free from deformation such
as warp or torsion after molding, and also has a same degree
of moldability as normal synthetic resins.
3Q The composite material composition according to this
invention comprises
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adding about 70 to about 150 parts by weight of a thermo-
plastic resin to 100 parts by weight of wastepaper. The
composition may suitably also contain synthetic or natural
rubber, an inorganic filler or there additives so as to provide
the composition with the properties that are suitable for use as
moldings.
The present invention also provides a method of
producing a composite material composition using wastepaper which
method avoids the steps of beating, paper processing and
drying which require great volumes of industrial water.
The present invention further provides a method
of producing a composite material composition using wastepaper
in a short time and with high efficiency by using only a small
amount of e~uipment for cutting the wastepaper and mixing and
granulation of the blend.
According to this invention there is provided a
method of producing a composite material composition using waste-
paper which method comprises a wastepaper cutting step, a mixing
and drying step in which cut wastepaper, a thermoplastic resin
and/or other additives are mixed under stirring at high speed
in a mixer while water contained in wastepaper is removed
by frictional heat generated during the mixing to dry the mixture,
a melting step în which high-speed stirring is further continued
in the mixer to develop frictional heat thereby to melt the
,~
thermoplastic resin and additives, a kneading step in which
high-speed stirring is still continued in the mixer to beat
wastepaper in the melt phase so that wastepaper is impregnated
with the melt, and a granulation step in which the kneaded
composition is granulated. This method may further comprise
preheating of the mixer for effecting the process in a shorter
period of time with higher efficiency, incorporation of a nu-
cleation step between the kneading and granulation steps, and
employment of a controlling means.
The method of this invention can be applied for pro-
ducing of a new composite material composition from a used one
by pulverizing the scraps of the moldings from the composition
of this invention and adding the pulverized material to the mix-
ture of wastepaper, thermoplastic resin and/or additives.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The composite material composition according to this
invention comprises 100 parts by weight of wastepaper and about70 to 150 parts by weight of a thermoplastic resin. The
wastepaper used here is, for example, newspaper, corrugated
board, cardboard and scraps thereof. Any sort of paper that
is available in bulk at low cost may be used. Such wastepaper
may be used with no such pretreatment as washing, tempering or
drying. Therefore, the wastepaper, when used, may contain
a size, filler, pigment, ink and other like substances.
It also contains moisture of usually about 10 to 15% when it
is in an equilibrium state. Since large-sized wastepaper re-
~uires a substantial time for mixing an~ milling with the ther-
moplastic resin and other additives, wastepaper is usually cut-
out small pieces with a size of less than 30 mm, preferablyabout 5 mm and then mixed and milled with the resin, etc.
The thermoplastic resin used in this invention may be
of any type of thermoplastic polymer. Examples of such thermo-
plastic resins are polyethylene, polypropylene, ethylene/propy-
len~ copol~ymer, polybutene, polyvinyl chloride, polyvinyl ace-
tate, polymethacrylic acid esters (particularly methyl esters),
polyacrylic acid esters and polystyrene. These thermoplastic
resins may be used singly, or they may be used in combination
for imparting the properties that suit the intended use of the
moldings. Also, the thermoplastic resin used in the process of
this invention may be in the form of either pellets or powder.
The mixing ratio of the thermoplastic resin may be suitably
selected within the range of about 70 to about 150 parts by
weight per 100 parts by weight of wastepaper. If the amount of
the thermoplastic resin mixed exceeds about 150 parts by weight,
the properties of the resultantly produced composition appro-
ximate to those of the thermoplastic resin per se, resulting
in poor heat resistance and flame retardancy. On the other
hand, if the amount of the thermoplastic resin mixed is less
than about 75 parts
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1~,~8588
by weight~ mechanical strength, particularly impact strength,
of the resultant composition is excessively lowered. For this
reason, the most preferred mixing ratio of thermoplastic
resin to wastepaer is 100:100 by weight part~
The composite material composition using wastepaper
according to this invention may be blended with an additive or
additives to provide the properties that are required of the
moldings. ~enerally, if the mixing ratio of thermoplastic
resin to wastepaper is lessened, mechanical strength (impact
strength) of the moldings is deteriorated. In order to overcome
such problem, æynthetic or natural rubber may be added in an
amount of up to 20 parts by weight, together with about 70 to
about 150 parts by weight of a thermoplastic resin, to 100
parts by weight of wastepaper. Addition of such rubber leads
to a marked improvement of impact strength of the composition.
Synthetic rubber used for this purpose ~ay be suitably selected
from the thermoplastic synthetic rubbers ~uch as styrene
rubber, polybutadiene rubber, butyl rubber, nitrile rubber,
ethylene/propylene rubber and ethylene/vinyl acetate rubber.
Such syntheti~ or natural rubber may be used in the form of
either pellets or powder. Also, such rubber may be previously
blended with a thermoplastic resin and used in the form of a
comp~und.
In order to ~urther improve impact strength of the
composition, an inorganic filler may be ~lended in an
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113~S88
amount of up to 25 parts by weight to 100 parts by weight of
wastepaper, about 50 to 150 parts by weight of a thermoplastic
resin and up to 20 parts by weight of synthetic or natural rub-
ber. Such înorganic filler may be calcium carbonate, talc,
calcium sulfate, barium sulfate or the like.
It is also possible to blend stearic acid as lubri-
cant so as to improve compatibility of wastepaper with thermo-
plastic resin and/or other additives to facilitate mixing and
kneading thereof and to thereby further improve the properties
of the moldings.
rJe will now describe the method of producing the com-
posite material composition using wastepaper that has been
discussed above.
In the following description, the te~m "materials"
refers to wastepaper, thermoplastic resin and/or other addi-
tives. Also, the term "thermoplastic substances" refers to
thermoplastic resins and other thermoplastic materials in gen-
eral, such as synthetic rubber among the additives.
First, wastepaper is cut into small pieces with size
of less than 30 mm in the wastepaper cutting step for allowing
efficient mlxingand kneading of the wastepaper, thermoplastic
resin and/or other additive(s). Such cutting of wastepaper may
be effected in various ways. For example, wastepa2er is first
cut longitudinally and crosswise by a cutter and then the thus
cut paper is crushed by a mill. This method is favorable as it
allows obtention of cut pieces
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at high efficiency.
Then the cut peices of wastepaper are mixed with
a thermoplastic resin and/or other additive(s) in a mixer. In
this case, the thermoplastic resin, synthetic or natural rubber
and an inorganic filler may be fed into the mixer independently
in the form of pellets or powders, or all of these materials may
be pre-compounded and then fed into the mixer. As the materials
are thus supplied into the mixer, they are then agitated therein
at high speed, whereby the materials are well mixed up and at
the same time the water content of wastepaper is reduced to
about 0.3 to 1.0~ by dint of frictional heat that is generated
during said mixing, thus effecting drying of wastepaper.
As high-speed agitation of the materials in the mixer
is further continued, the temperature in the mixer is raised
by the frictional heat of mixing to a thermoplastic substance
melting temperature, whereupon the thermoplastic substances be-
gin to melt. Heating of the materials in the mixer is effected
by said frictional heat until reaching the melt temperature,
but since heating by such frictional heat alone takes a long
time for raising the temperature from ambient to melt starting
temperature, it is desirable to preheat the mixer by using a
heating medium to a temperature suited for drying of wastepaper
and then effect further drying of wastepaper and melting of the
thermoplastic substances by
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~138S0
frictional heat of the materials. This can appreciably shorten
the production time.
When high-speed stirring of the materials in the
mixer is further continued, the wastepaper begins to beat into
the melted thermoplastic substances to effect kneading of the
wastepaper, thermoplastic resin and other additives. This
kneading should not be continued for a long time because the
material temperature in the mixer rises so high as to cause
thermal decomposition of the wastepaper, etc., in the materials.
Also, too long time of beating and kneading excessively pro-
motes beating of the wastepaper, resulting in reduced mechani-
cal strength of the composition moldings.
.
Then the kneaded mass of materials is granulated by
using a known granulator to form a composite material composi-
tion. Molding of this composition into a form of use may be
accomplished by using a known molding means. For example, said
composition can be molded by a vented injection molding machine
in the same was as molding of an ordinary thermoplastic resin.
In a preferred mode of practice of this invention,
stirring in the mixer is decelerated to a medium speed for a
short period of time upon completion of material kneading and
then stirring of the materials is further continued to effect
nucleation in the early stage of granulation. This can reduce
the time required for the next granulation step.
No waste of material is suffered if the scraps of the
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11385~8
moldings from said composition are asain crushed into powder
and mixed in the fresh feed of materials.
Now, the composite material composition using waste-
paper according to this invention and the method of producing
such composition are described in further detail by way of
the embodiments thereof.
Described first is a preferred example of the compo-
sition production method according to this invention.
First, old newspapers (wastepaper) are cut into
square pieces with size of 7 cm x 7 cm, and the cut pieces of
newspaper are further cut into smaller pieces by a turbo-mill.
Only those of the finely cut newspaper pieces which have pas-
sed a 5 mm x 5 mm mesh screen are used as the ~astepaper ma-
terial for the process. Used in the process of this example
are 42.5 kg of the thus obtained newspaper cut pieces, 34 kg
of ethylene-propylene copolymer resin as therr.~oplastic resin,
4.25 kg of high-density polyethylene resin, 4.25 kg of ethylene-
propylene rubber and 0.04 kg of 2,6-di-t-butyl-4-methylphenol
(BHT~ as antioxidant (these materials are hereinafter referred
to as blend). This blend is supplied into a mixer which has
been previously heated to 75-80C by a heating medium,and then
is continuously stirred therein at the rate of 1,060 r.p.m.
for about 25 minutes. Thus, the interior of the mixer is ini-
tially kept at said preheating temperature 75-80C, but as the
blend with a lower temperature than such preheatin~
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temperature is supplied into the mixer, the temperature therein
drops temporarily. However, since the blend is stirred at high
speed in the mixer, the tempera,ure in the mixer begins to rise
5 minutes after the start of stirring owing to frictional heat
which is generated by mixing of the blend materials. Such rise
of temperature takes place slowly until moisture in the waste-
paper in the blend is driven off to effect sufficient drying
thereof. When drying of the wastepaper in the blend is sub-
stantially completed, there takes place more sharp rise of intra-
mixer temperature by dint of frictional heat, and when the tem-
perature in the mixer reaches 162C, the thermoplastic sub-
stances in the blend begin to melt. 20 minutes was required
until such melting began from start of stirring. Melting of
the thermoplastic substances causes sharp increase of the
blend viscosity, so that frictional heat is generated succes-
sively by the continued agitation to effect perfect melting of
the thermoplastic substances. As the thermoplastic substances
are thus melted, the wastepaper is beating into the melt phase.
In this condition, the beaten wastepaper and molten thermo-
plastic substances (which rope) are kneaded while further pro-
moting beating of the wastepaper and causing impregnation of the
theremoplastic substances in the beaten wastepaper. If stir-
ring isfurther continued for a long time, the temperaturein the
mixer excessively rises to give rise to an unfavorable
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situation such as carbonatization of the wastepaper component
in the blend, so that this kneading step was switched to the
next nucleation step upon passage of about 25 minutes after
start of stirring in the mixer. In the above-described process,
the load current of the mixer motor is a~ound 200 A at the
` B~ stage where mixing and ~ 9 of the blend has been completed,
but said load current ~egins to inrease with start of melting
of the thermoplastic substances in the blend and the viscosity
of the blend ri~o~ u~ in accordance ~ith advancement of melting,
causing further increase of the load current of the mixer
motor. When the load current of saia mixer motor has reached
about 250 A, control of proceeding to the next nucleation
step was performed. The blend temperature at the time of
proceeding to the nucleation step was 180-190C. In the next
nucleation step, additional stirring was'carried out for 6-
7 minutes by dropping the stirring rate to 530 r.p.m. This
has initiated ~ormation of clusters of small particles oi the
kneaded blend (early phase of granulation). The blend tempera-
ture upon completion of this nucleation step was 225C.
After completion of this nucleation step, the blend was
transferred into another mixer which had been water-cooled
to about 20C, and further subjected to additional 15-minute
stirring at the rate of 100 r.p.m., whereby the blend wa~
formed into particles with diameter of approximately 2-3 mm,
with temperature thereof being down to 70C. The thus granulated
blend may be molded into a desired form of use by a vented
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injection molding machine in the same way as molding of an
ordinary synthetic resin.
'rhe moldings obtained from the above-described composite
material compositions according to this invention had the
properties shown in the following table. In Example 1, a
composite material composition was prepared according to the
above-described method by using 42.5 kg of wastepaper, 34 kg
of ethylene-propylene copolymer resin, 4.25 kg of high-density
polyethylene resin, 4.25 kg of ethylene-propylene rubber and
0.04 kg of ~H~, and a molding was formed from such composition.
In Example 2, a similar composition was prepared in the
similar way by using 25.5 kg of wastepaper, 40.8 kg of ethylene-
polypropylene copolymer resin, 5.1 kg of high-density polyethylene
resin, 5.1 kg of ethylene-propylene rubber, 8.5 kg of calcium
carbonate, 0.2 kg of stearic acid and 0.05 kg of BHT. In Comparative
Example 1, a molding was formed from a blend consisting of
80 kg of ethylene-propylene copolymer resin, 10 kg of high-
density polyethylene resin, 10 kg of ethylene-propylene rubber
and 0.1 kg of BHT. The composition ~f Comparative Example 1
is same as that of Example 1 from which wastepaper was
excluded. In Comparative Example 2, a composition was
prepared by using 3 parts by weight of a thermoplastic resin
and 2 parts by weight of talc. Thus, it shows the properties
of a composition in which an înorganic filler is incorporated.
In Comparative Example 3, a composition was prepared
according to Example 1 without using wastepaper but by using
instead woodmeal crushed to the size of less than 30 meshes.
The ~n~g rate in the table was mea~red accord~g to the U.S. Federal Motor
Vehicle Safety Standard~.
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