CA2102044A1

CA2102044A1 - Plastic molding composition for the production of moldings having a color-coordinatable decorative effect

Info

Publication number: CA2102044A1
Application number: CA002102044A
Authority: CA
Inventors: Frank Reuter; Ulrich Mohr-Matuschek; Christiane Strohm
Original assignee: Individual
Current assignee: Hoechst AG
Priority date: 1992-10-31
Filing date: 1993-10-29
Publication date: 1994-05-01
Also published as: KR940009259A; EP0596379A1; JPH06200169A; ZA938093B; AU5034993A; AU663978B2; BR9304396A; CN1090588A

Abstract

Abstract of the disclosure Plastic molding composition for the production of mold-ings having a color-coordinatable decorative effect A plastic molding composition which contains from 0.2 to 7.5 % by weight of natural vegetable fibers having a fiber length of from 0.1 to 15 mm can be converted into moldings having a color-coordinatable decorative effect, where the good thermal and mechanical resistance and dyeability of the natural vegetable fibers is a particu-lar advantage. These moldings are used, in particular, in the interior of motor vehicles, but are also suitable for other applications, for example for small domestic appliances, garden furniture or office equipment.

Description

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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 ~ 2 1 ~ 4 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 ~ 2 ~

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 ' 2~2~

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.
~ ., -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; ~-~, ' ~' ' ~' " ' ' - ';' ' , :

'' . ' ,: . : ' .''". ' ' ': ' 2 ~ ~ ~

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-'." " ' ' ' . '' . . ' '' ' ' ' ' ~- ` .

.j:. ' , ` , ' , ' ', ~, ,. ' : ' .. ,. ~ " ,,, .; " . , ~ - 6 _ 2~2 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 2~2~

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. - ~
: ,-' 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~.

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 2 ~ Q ~ ~

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.
'.~ -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.

Claims

1. A plastic molding composition for the production of moldings having a color-coordinatable decorative effect, comprising a) from 100 to 50 % by weight of a thermoplastic poly-mer, b) from 0 to 50 % by weight of reinforcing materials 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.

2. A molding composition as claimed in claim 1, which contains bast fibers having a fiber length of from 0.1 to 15 mm.

3. A molding composition as claimed in claim 1, which contains flax fibers having a fiber length of from 0.1 to 15 mm.

4. A molding composition as claimed in claim 1, which comprises a) from 95 to 50 % by weight of isotactic polypropylene or copolymers of propylene containing up to 15 % by weight of ethylene, b) from 5 to 50 % by weight of rubber-like copolymers which are compatible with polypropylene, c) from 0 to 50 % by weight of reinforcing materials and/or fillers, and from 0.2 to 7.5 % by weight, based on a) + b) + c), of flax fibers having a fiber length of from 0.1 to 15 mm.

5. A molding composition as claimed in claim 1, wherein the reinforcing materials and/or fillers are talc, chalk, glass fibers or glass beads.

6. A molding composition as claimed in claim 1, wherein the base polymer has been dyed in a pale base color.

7, A molding composition as claimed in claim 1, wherein the natural vegetable fibers have been dyed, before admixing with the base polymer, in a color which is matched to the visual coordination of the molding surface with the surroundings.

8. The use of a plastic molding composition as claimed in claim 1 for the production of moldings having a color-co-ordinatable decorative effect.