Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
2002-10-31
2004-09-21
Thexton, Matthew A. (Department: 1714)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C428S392000, C524S099000, C524S100000, C524S104000, C524S106000, C524S195000, C524S213000, C524S214000, C524S216000, C524S420000
Reexamination Certificate
active
06794032
ABSTRACT:
The present invention relates to a long-fiber-reinforced polyolefin structure and to moldings produced therefrom with very good impact strength and with high heat distortion temperature (HDT), and with markedly reduced odor emission. The present invention further relates to the use of the moldings produced in the interior of motor vehicles.
Polyolefins, in particular those encompassing polyethylene and polypropylene, are low-cost thermoplastics with low density, and good fusibility, and also chemicals resistance. They are therefore widely used in sectors such as general household items, and electrical and electronic components. However, polyolefins usually have low heat distortion temperature (HDT) and low levels of mechanical properties. These plastics are therefore unsuitable for use in areas where there is a need for high heat distortion temperature and high mechanical strength.
It was known that a reinforcing fiber, such as glass fiber, can be mixed with the polyolefin to improve its strength. The fiber-reinforced polyolefin composition obtained has generally been one in which a polyolefin has been mixed with short reinforcing fibers and then the mixture has been extruded in an extruder. However, a disadvantage of this process is that the fibers break during grinding in the extruder. This process cannot give moldings which have the required relatively high mechanical strength.
It was also known that a polyolefin can be reinforced with long fibers, utilizing the character of the reinforcing fiber for the polyolefin with which it is to be mixed. One way of obtaining a long-fiber-reinforced polyolefin structure of this type is continuously to unwind a reinforcing fiber and immerse this in an emulsion or solution of a polyolefin, or in a polyolefin melt. The long-fiber-reinforced polyolefin has better mechanical properties than the short-fiber-reinforced polyolefin described above.
Although there is a requirement in the automotive industry and in similar sectors for a further increase in impact strength, this requirement cannot be complied with by conventional long-fiber-reinforced polyolefins. In order to give a further improvement in impact strength it is possible for another thermoplastic with very good impact strength to be mixed with the long-fiber-reinforced polyolefin. However, simple mixing of the polyolefin with another plastic cannot give products whose mechanical properties are industrially useful. The reason for this appears to be the low mutual dispersibility of the plastics.
U.S. Pat. No. 5,409,763 discloses a rod-shaped long-fiber-reinforced polyolefin structure with a length of at least 3 mm, produced by mixing 100 parts by weight of a plastics component encompassing from 99 to 50 parts by weight of a polyolefin and from 1 to 50 parts by weight of a polyamide with from 10 to 200 parts by weight of a reinforcing fiber. The length of the reinforcing fiber is the same as that of the structure, and the arrangement of the reinforcing fiber is substantially longitudinal. That publication also discloses an article which has been molded from this rod-shaped long-fiber-reinforced polyolefin. The dispersed reinforcing fiber in the polyamide has an average fiber length of at least 1 mm, and there is interpenetration of the polyolefin and the polyamide to form a network dispersion.
The polyamide plastic used has strength which exceeds that of the polyolefin, and has surface tension between that of the polyolefin and that of a reinforcing fiber, such as glass fiber. A rod-shaped structure is produced by mixing, in the melt, of the polyolefin with the polyamide, and immersing the reinforcing fiber in the melt, and molding the rod-shaped structure. This gives a molding with extremely high impact strength. In this, the polyamide forms a network structure with the reinforcing fiber and at the same time with the polyolefin. This network structure is further improved as fiber length increases.
It is known that it is preferable to use a modified polyolefin, since it bears functional groups which have high affinity for the polyamide. This increases the affinity between the polyolefin and the polyamide, and therefore improves capability to develop a network structure. The effect cannot begin to occur until the proportion of modified polyolefin is at least 1% by weight. If the proportion exceeds 50% by weight, the viscosity of the composition rises, and this can cause difficulties during shaping.
The polyolefin may be prepared by polymerizing an &agr;-olefin, such as ethylene or propylene, using a suitable catalyst.
Various known polyamides may be used as polyamide. If the proportion of polyamide in the mixture is below 1%, no effective improvement in impact strength can be achieved. If the proportion exceeds 50%, the volume change of the molding due to water absorption becomes problematic.
If the proportion of reinforcing fiber is less than 10 parts by weight, the fibers achieve only a small reinforcing effect. If the proportion of reinforcing fiber exceeds 200 parts by weight, the production of the rod-shaped structure becomes difficult, or capability for processing to give a molding is considerably impaired.
There are prior-art compositions made from polyolefin, polyamide, modified polyolefin, and glass fiber. Examples of these compositions are described, inter alia, in JP-A 03126740, JP-A 03124748, GB-A 2225584, JP-A 02107664, JP-A 01087656, JP-A 01066268, JP-A 63305148, JP-B 06018929, JP-A 60104136, JP-B 61026939, JP-A 56030451, JP-A 6322266, JP-A 7053861, and JP-A 6234896.
There are many applications demanding a long-fiber-reinforced polyolefin structure. For stabilization with respect to oxidation and UV irradiation, and also for coloring, the long-fiber-reinforced polyolefin structure is treated with at least one additive. The addition of even small amounts of at least one additive, such as dye and/or pigment, has considerable effects on the mechanical properties of the polyolefin.
A pigment which can be used in a short-fiber-reinforced polyolefin structure is TiO
2
. TiO
2
is not a suitable pigment in a long-fiber-reinforced polyolefin structure, since addition of TiO
2
impairs mechanical properties.
It has been found that sulfur-containing additives are particularly suitable in a long-fiber-reinforced polyolefin structure, since they do not affect mechanical properties. However, a decisive disadvantage of sulfur-containing additives is unpleasant odor emission. The odor emission makes the long-fiber-reinforced polyolefin structure with sulfur-containing additives unusable for production of parts of the interior of motor vehicles, despite good mechanical properties.
The object of the present invention is to provide a long-fiber-reinforced polyolefin structure with very good mechanical properties, with good heat resistance and low water absorption, and with low odor emission, together with an environmentally compatible and cost-effective process for its production.
The object of the present invention is achieved by means of a long-fiber-reinforced polyolefin structure with a length of ≧3 mm, comprising
a) from 0.1 to 90% by weight of at least one polyolefin,
b) from 0.1 to 50% by weight of at least one polyamide,
c) from 0.1 to 15% by weight of at least one modified polyolefin,
d) from 5.0 to 75% by weight of at least one reinforcing fiber,
e) from 0.1 to 10% by weight of at least one sulfur-containing additive.
The present invention is characterized by the use of at least one sulfur-containing additive, such as a dye and/or pigment. Unexpectedly and surprisingly, despite addition of at least one dye and/or pigment, the resultant colored long-fiber-reinforced polymer mixture has very good mechanical properties, very good heat resistance, and low water absorption. This polymer mixture has not only good mechanical properties but also surprisingly low odor emission, despite the use of at least one sulfur-containing additive.
The sulfur-containing additive in colored long-fiber-reinforced polyolefin structures is preferably a sulfur-containing colorant, with preference a su
Bernd Heinz
Borgner Thomas
Heydweiller Joachim
Thomas Gabriele
Connolly Bove & Lodge & Hutz LLP
Thexton Matthew A.
Ticona GmbH
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