Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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HOECHST AKTIENGESELLSCI~AET HOE 92/F 344 Dr.DA/-
Description
Plastic molding composition for the production of mold-
ings having a color-coordinatable decorative effect
The invention relates to a thermoplastic molding compo~i-
tion for the production of moldings having a special
decorative surface effect. The molding composition can be
processed by conventional proceRsing methods, such a~
injection molding, extrusion and extrusion blow molding.
Internal trim parts for motor vehicles and casings for
small domestic appliances are currently generally
produced by injection molding from thermopla~tics.
Polypropylene (PP), both in the form of standard grade
and in filled, reinforced or modified product grades, ha3
recently begun to find its way into an ever increasing
number of application~
The thermoplastic materials are dyed in the mass, and the
finished part~ are in very many case~ provided with a
surface structure (grain) for the sake of appearance and
feel. ~his grain is produced during the injection-molding
process by casting from corresponding 6tructures engraved
in the surfaces of the cavity of the injection mold. This
gives moldings having a structured ~urface, but with a ~ ;
homogeneous color. ~-~
Mass-dyed moldings having a surface grain are an adequate
solution for many applications vis-à-vis design and
quality requirements. However, there i~ a demand, in
particular for the interior of large family car3 and
executive cars, for moldings which are able to satisfy
higher demands regarding appearance and comfort.
In order to produce higher-quality surfaces in moldings
for the interior of motor vehicles, the trim part~ can
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either be painted (for example with a soft finish) or
laminated with films or textile materials. The lamination
is in each case carried out with the aid of adhesives.
Depending on the nature of the substrate material,
pretreatment of the moldings by flame treatment, corona
discharge or the like is nece~sary in order to achieve
good adhesive strength. These individual process steps
mean relatively high production cost~. A further associ-
ated disadvantage i8 the unfavorable fogging behavior.
Fogging is taken to mean condensation of (evaporated)
volatile constituent~ from the interior trim of motor
vehicles onto the windows, in particular the windscreen.
The fogging intensity is naturally dependent on a number
of factors and on the prevailing temperature conditions.
Since adhe~ives frequently contain relatively high
proportions of volatile ~ubstances, adhesive-laminated
parts virtually always represent a significant fogging-
promoting potential. ~ ~
A further disadvantage can occur in the case of adhesive- ~;
laminated parts regarding design freedom. Due to the only
re~tricted moldability of textiles and films in some
cases during the lamination process, restrictions may
have to be taken into account regarding the geometrical
design of the Rubstrate parts.
The object was therefore to develop thermoplastic materi-
als which can be processed by conventional shaping
method~ for plastics. The surfaces of the fini~hed parts
should have a special decorative, color-coordinatable
surface effect (sprinkled surface, heather mix effect,
textile look).
It is in principle possible to provide dyed polypropylene,
possibly additionally modified by means of reinforcing
substances, such as glas~ fibers or talc and/or elastomers,
with fibers of another color. It is known that fibers made
from, for example, thermoplastic polyester, polyamide or
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polyacrylonitrile which have good thermal and mechanical
resistance can be admixed with the polypropylene in an amount
of from about 0.5 to 3 ~ and homogeneously mixed with the
polymer in extruders. Test sheets produced therefrom and
provided with a grained surface exhibited a special textile-
like surface effect matched to the design of textile-
laminated moldings. ~owever, attempts to produce large-area
moldings in which long flow paths were present as a conQe-
quence of the geometry were unsatisfactory. The reason was
the inadequate thermal and mechanical resisting force of the
polyester, polyamide or polyacrylonitrile fiber~. The pro-
cessing temperature of from about 230 to 270C necessary
during injection molding of polypropylene and the material
shear occurring in screw injection-molding machines during
homogenization and during flow through hot runners and narrow
gates resulted in considerable heat damage to the fibers.
Furthermore, these shear forces, in combination with the high
temperature, in some cases even caused 1088 of the fiber
geometry, which meant that the impression of a textile-like
surface was completely lo~t.
Due to the problems with the use of polyester, polyamide
and polyacrylonitrile fibers, it has been proposed to use
carbon fibers ~cf. ~E 42 21 208). In this case, it was
found that use of carbon fiber~ was not accompanied by
any mechanical or thermal problems, and the desired
decorative effect of the molding surface can be achieved.
However, the use of carbon fiber~ does not allow the
coloring of the fibers which is necessary for special
decorative purposes.
It has now been found that the object can be achieved by
the use of natural vegetable fibers.
The use, for example, of flax fibers for reinforcing
polymers i5 known per se. Amounts of from 10 to 50 % as
cut flax fibers are usually added to polymer~ to achieve
a significant improvement in the mechanical properties
(flexural strength, modulus of elasticity, tensile
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strength, etc.).
The invention thus relates to a pla~tic molding compo~
tion for the production of moldings having a color-
coordinatable decorative effect, containing
a) from 100 to 50 % by weight of a thermoplastic
polymer,
b) from 0 to 50 % by weight of reinforcing material
and/or fillers, and
from 0.2 to 7.5 % by weight, based on the molding
composition, of natural vegetable fibers having
a fiber length of from 0.1 to 15 mm.
The plastic molding composition according to the inven-
tion contains a thermopla3tic organic polymer, for
example one of the following:
1. Polymers of mono- and diolefins, for example high-,
medium- or low-density polyethylene ~which may be cross-
linked) or polypropylene.
2. Mixtures of the polymers mentioned under 1) with one
another or with other olefin polymers, for example
mixtures of polypropylene with polyethylene, copolymers
of mono- and diolefins, ~uch as, for example, ethylene-
propylene copolymers, propylene-l-butene copolymers,
propylene-isobutylene copolymers, ethylene-l-butene
copolymers, propylene-butadiene copolymers, isobutylene-
isoprene copolymers, and terpolymers of ethylene withpropylene and a diene, such a~ hexadiene, dicyclopenta-
diene or ethylldenenorbornene.
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3. Polystyrene.
4. Copolymers of styrene or a-methylstyrene with dienes
or acrylic derivatives, such as, for example, styrene-
butadiene, styrene-maleic anhydride, styrene-acrylonit~
rile, styrene-ethyl methacrylate, 6tyrene-butadiene-ethyl
acrylate, styrene-acrylonitrile-methacrylate; ~-
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high-impact-strength mixtures of styrene copolymers and
another polymer, such a~, for example, a polyacrylate, a
diene polymer and an ethylene-propylene-diene terpolymer;
and block copolymers of styrene, such as, for example,
styrene--butadiene-styrene, styrene-isoprene-styrene,
styrene-ethylene/butylene-styrene or styrene-ethylene/
propylene-styrene.
5. Graft copolymers of styrene, such as, for example,
styrene on polybutadiene, ~tyrene and acrylonitrile on
polybutadiene, styrene and maleic anhydride on polybuta-
diene, ~tyrene and alkyl acrylates or alkyl methacrylates
on polybutadiene, ~tyrene and acrylonitrile on ethylene-
propylene-diene terpolymers, styrene and acrylonitrile on
polyalkyl acrylates or polyalkyl methacrylates, styrene
and acrylonitrile on acrylate-butadiene copolymers, and
mixtures thereof with the copolymers mentioned under 5),
which are known, for example, aæ ABS, MBS, ASA or
AES polymers. .
6. Polyvinyl chloride~
7. Polyacetal~, such a~ polyoxymethylene, and polyoxy-
methylenes which contain comonomers, such as, for ex-
ample, ethylene oxide.
8. Polyphenylene oxides and ~ulfides, and mixtures
thereof with styrene polymer~.
9. Polyurethanes derived from polyethers, polye~ters and
polybutadienes containing terminal hydroxyl group~i on the
one hand and aliphatic or aromatic polyisocyanatee on the
other hand, and precursors thereof (polyisocyanate polyol
prepolymers).
10. Polyamides and copolyamides derived from diamines and
dicarboxylic acids and/or from aminocarboxylic acid~ or
the corresponding lactams, such a~ nylon 4, nylon 6,
nylon 6.6, nylon 6.10, nylon 11, nylon 12, poly-2,4,4-
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trimethylhexamethyleneterephthalamide, poly-m-phenylene-
isophthalamide, and copolymers thereof with polyethers,
such as, for example, with polyethylene glycol, polyprop-
ylene glycol or polytetramethylene glycol.
11. Polyesters derived from dicarboxylic acids and diols
and/or from hydroxycarboxylic acidq or the corresponding
lactones, such as polyethylene terephthalate, polybutyl-
ene terephthalate, poly-1,4-dimethylolcyclohexane tereph-
thalate, poly(2,2-bis(4-hydroxyphenyl)propane)terephthal-
ate, polyhydroxybenzoate, and block polyether estersderived from polyethylene having hydroxyl terminal
groups, dialcohols and dicarboxylic acids.
12. Polycarbonates and polyester carbonates.
13. Mixtures of the abovementioned polymers, such as, for
example, PP/EPDM, nylon 6/EPDM or ABS, PVC/~VA, PVC/ABS,
PVC/MBS, PC/ABS, PBTP/ABS, PC/ASA, PC/PBT, PVC/CPE,
PVD/acrylate, POM/thermoplastic PUR, POM/acrylate,
POM/MBS, PPE/~IPS, PPE/nylon 6.6 and copolymer~, PA/HDPE,
PA/PP and PP~/PPE. .
Preference is given to olefin polymers, in particular
polypropylene. -
The ba6e material for the molding composition according
to the invention compri6es
a) from 100 to 50 % by weight, preferably from 90 to
60 % by weight, of polymer and
b) from O to 50 % by weight, preferably from 10 to 40 %
by weight, of reinforcing material~ and/or filler~.
Preference is given to a homopolymer or copolymer of
propylene having a melt flow index MFI 230/5 in accord~
ance with DIN 53 735 of from 0.5 to 95 g/10 mln.
In particular, the ba~e material comprises
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a) from 95 to 50 ~ by weight, preferably from 90 to
70 ~ by weight, of isota~tic polypropylene or
copolymers of propylene containing up to 15 % by
weight of ethylene,
b) from 5 to 50 % by weight, preferably from 10 to 30 %
by weight, of rubber-like copolymers which are
compatible with polypropylene, and
c) from 0 to 50 % by weight, preferably from 10 to 40 %
by weight, of reinforcing materials and/or filler~.
Particularly quitable rubber-like copolymers are amor-
phous copolymers comprising from 30 to 70 % by weight of
ethylene and from 70 to 30 % by weight of propylene,
terpolymers of ethylene, propylene and up to 5 % by
weight of dienes, preferably ethylidenenorbornene or 1,4-
hexadiene, copolymers of ethylene and from 10 to 45 ~ byweight of vinyl acetate, or block copolymers of styrene
and butadiene or styrene and isoprene which have poly-
styrene blocks at both ends of the molecule.
Preferred reinforcing materials and/or fillers are talc,
chalk, glass fibers or glass beads.
According to the invention, the base material i8 mixed
with natural veqetable fibers, such as, for example, ba3t
fibers, hard fibers or vegetable hairs, preferably bast
fi~ers, having a length of from 0.1 to 15 mm, preferably
from 1 to 5 mm, and a diameter of from 10 to 30 ~m, in
or~er to achieve a decorative effect. The amount added i8
from 0.2 to 7.5 ~ by weight, preferably from 1 to 3 % by
weight, based on the total molding composition.
Suitable natural vegetable fibere are flax, hemp, jute
and ramie, preferably flax.
Flax is the bast fiber from the flax plant (Linum usitat-
issimum) and, as an indu~trial fiber, i8 from about 20 to
140 cm in length and from 0.1 to 0.6 mm in thickness. ~he
individual fiber is from about 20 to 50 mm in length and
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from 10 to 30 ~m in thickness. Flax i8 a renewable raw
material which, compared with other natural fibers such
as cotton, hemp and 6isal, has excellent stiffness and
strength and is only inferior in mechanical properties to
ramie. Flax fibers can readily be dyed in different
colors, so that pale fibers in dark base molding co~pos-
itions and dark fibers in pale base molding compositions
can also be employed.
Hemp is a bast fiber from the hemp plant (Cannabis
sativa). The individual bast fiber i8 from about 5 to
55 mm in length and from about 15 to 30 ~m in thickness.
Jute is obtained ac the bast fiber from certain linden
species in India. The length of the fiber bundles is from
1.5 to 2.5 m, and the individual fibers are from 1 to
5 mm in length and from 10 to 30 ~m in thickness. - ~
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Ramie is the bast fiber from the stalks of the Boehmeria
plant genus. The individual fibers are from 60 to 250 mm
in length.
Other suitable natural vegetable fibers are hard fibers,
such as, for example, sisal, Manila hemp or coconut
fibers, and plant hairs, ~uch as, for example, cotton or
kapok. ;~-
The molding composition according to the invention may
furthermore contain conventional additives which 6Lmplify
processing and improve the physical properties. Bx2mples
which may be mentioned are light and heat stabilizer~,
antioxidants, antistatics and lubricants, and colored
pigments and flameproofing agents. The first group is
generally present in the molding composition in an amount
of from 0.01 to 5 % by weight, calculated with respect to
the amount of polymer (plu~ filler). Fillers, colored
pigments and flameproofing agents are employed in an
amount corresponding to requirement~.
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Examples of suitable processing methods are injection
molding, extrusion and extrusion blow molding.
The processing conditions for the molding composition
according to the invention correspond to the conditions
normally used in the processing of the plastic~ men-
tioned. The processing temperatures - measured directly
after leaving the die - are, for example in the case of
polypropylene, in the range from 240 to 280C, depending
on the size and complexity of the molding. The mold
temperature is generally from 40 to 70C.
For the production of particularly large-area and diffi-
cult moldings from a processing point of view, it i~ also
possible to choose particularly high processing tempera-
ture~ for such articles without impairing the color or
properties.
It should be particularly emphasized that the excellent
dyeability of the flax fibers in a very wide variety of
colors can be utilized to achieve color and decorative
effects in the finished part which are coordinated
specially with the application or environment. Colored,
textile-like decorative effects of this type open up
entirely new design opportunities in the use of
unlaminated plastic moldings.
An optimum effect i8 obtained on use of polymers in white
and very pale gray shades. Good result~ can also be
achieved with dark-colored fibers in base polymers which
have been colored in a relatively pale shade (for example
pale blue or pale brown). The effect can also be
influenced by surface treatment of the moldings.
Conversely, however, pale fibers in base molding composi-
tions which have been colored in a dark shade are also
po~sible.
The molding composition according to the invention
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facilitates the use of conventional, economically advant-
ageous processing methods for plastics (such as, for
example, injection molding) for applications which were
hitherto the province of molding~ produced in a more
complex manner (~uch as, for example, by adhesive l~m;na-
tion). Moldings made from the molding composition accord-
ing to the invention can be used, in particular, in the
interior of motor vehicles. However, they are just as
suitable for other applications, such as, for example,
for small domestic appliance~ or office and communication
equipment. From the large number of possible applica-
tion6, the following i~ a list of a few examples:
Motor vehicles: - door trim,
- column trim, door sill
strips,
- motorcycle panniers.
Office: - office furniture moldings
(backrests, armrest~, chair
legs, computer housings, fan
housings, etc.l,
- office furniture veneers,
- attaché case shell~.
Domestic: - toaster housing,
- domestic coffee machines,
- irons,
- freezer and cold storage
vessels, bowl~, etc.,
- garden furniture.
. Construction: - electrical installation pro-
grams (such as ~witches,
switch covers, etc.).
The particular advantages of the molding composition~
according to the invention are:
- the excellent, in some cases textile-like,
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decorative effect (heather mix effect, textile
look),
- the uperior dyeability of natural vegetable fibers
before admixing for color coordination of the
decorative effect with the base color of the molding
composition and/or other decorative elements or
moldings in the vicinity,
- the ready processibility without thermal or mechani-
cal decomposition and
10 - significant economic advantages of natural vegetable
fibers, for example compared with carbon fibers.
The examples below serve to illustrate the invention:
Example 1
(Motor vehicle column trim)
The trim of an A-column of a large European family car
was produced by injection molding. The molding had a
length of 1220 mm, a width of 76 mm and a wall thickness
of 2.3 mm. The injection was carried out centrally via
three pin gates, each with a diameter of 1.5 mm, arranged
12 mm apart. A melt temperature of from 270 to 275C was
u~ed in order to achieve optimum filling of the two-cavi-
ty mold in spite of the long flow paths. The injection-
molding machine used had a locking force of 10000 kN. The
screw diameter wa~ 90 mm. The temperatures set in the
injection-molding barrel were, starting from th~ feed
hopper: 240, 260, 280, 280 and 294C. The overall cycle
was 60 xec.
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The material used was a propylene copolymer containing
20 % by weight of talc and having an MFI 230/5 of `~
55 g/10 min in a pale-gray base color, to which 1.5 % by
weight of flax fibers having a fiber length of from 0.1
to 4 mm and a diameter of from 10 to 30 ~m which had been
colored black had been mixed. The desired visual coordin-
ation of the column trim provided with a fine grain with
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the adjacent textile-laminated headliner wae achieved
fully. As required, production was reliable, in spite of
the relatively high melt temperature necessary. ~ven
during production interruptions, there was no evidence of
a color shift or a change in propertie~ caused by addi-
tion of the fiber~.
Example 2
(Toaster housing)
A toaster housing wa~ produced, likewise by injection
molding, from a molding composition in a white base color
based on a propylene homopolymer containing 10 % by
weight of talc. In addition, 2 % by weight of flax fibers
which had been colored green (fiber diameter and length
as in Example 1) had additionally been admixed with the
molding composition. The molding was produced in an
injection-molding machine with a locking force of
5000 kN. All the housing walls were injected as one part
in a plane, the ~ide surfaces being provided with a
fluted pattern. By contrast, the end surfaces of the
housing were smooth. The housing was finally produced by
folding the molding by 90 degrees in each ca~e at the
three film hinges which had been incorporated. The folded
housing wa~ fixed together by snap hooks. The form hinges
were significant flow barrier~ during injection. For this
reason, a polypropylene having an MFI 230/5 of
85 g~10 min was selected and processed at a material
temperature of 265C. In spite of this relatively high
material temperature and the high material ~hear ocrurr-
ing at the bottlenecks of the film hinges, there were no
chanqes in color or other undesired surface defect~. The
heather-mix effect required by the design in a mlnt shade
was achieved in full.
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Example 3
(Motorcycle pannier)
A motorcycle pannier wa~ produced with twin walls in one
piece by extrusion blow molding from high-impact, un-
filled propylene copolymer. The two pannier shells andthe lid at the top are connected by continuous film
hinges. The extrusion blow molding process and the high
impact strength desired for the finished part required
the use of a high-viscosity material having an MFI 230/5
of about 0.5 g/10 min. 2.8 % by weight of flax fibers
which had been colored dark blue (fiber length and
diameter as in Example 1) had been admixed with the pale-
blue polypropylene base material. The molding composition
was processed at 240C. Not only design precautions, such
as the twin walls and the sealed-in air cushion, but also
the high-impact and rigid material type offer stability
and protection. The flax fiber-filled molding composition
in combination with a special grained structure provided
the scratch resistance necessary for practical use and
the ~urface decoration desired (heather-mix effect).
Example 4
i
(Vehicle door sill strip~)
Continuous extrusion was u~ed to produce a plastic
profile which is used - cut into 95 cm strips - as a door
sill strip in a large family car. For visual coordination
with the carpet and the interior trim parts of the car,
a dark-gray propylene copolymer which had been reinforced
with 20 % by weight of glase fibers and to which 1.5 ~ by
weight of flax fibers which had been colored black had
been admixed was used for the door ill strip. The
flowability of the material was characterized by an
MFI 230/5 of 5.5 g/10 min. The material temperature at
the exit from the extrusion die wa6 240C. No problems at
all occurred during processing of the flax fiber-modified
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material type. The fluted surface of the extruded prod-
ucts showed the desired textile-like decorative effect,
which harmonized excellently both with the carpet and
with the interior trim of the car.
