Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Reexamination Certificate
2000-10-26
2002-11-19
Kelly, Cynthia H. (Department: 1774)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
C428S374000, C428S378000, C428S383000, C428S390000
Reexamination Certificate
active
06482515
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a colored long-fiber-reinforced polyolefin structure and to shaped articles produced therefrom and having very good impact strength and high heat resistance (HDT).
2. Description of the Prior Art
Polyolefins, in particular those which comprise polyethylene or polypropylene, are low-cost, low-density thermoplastics which melt readily and are resistant to chemicals. These materials therefore have many uses in areas such as general household items and electrical and electronic parts. However, polyolefins usually have low heat resistance (HDT) and modest mechanical properties. These plastics are therefore unsuitable for use in areas which require high heat resistance and high mechanical strength.
It was known that a reinforcing fiber, such as glass fiber, can be mixed with a polyolefin to improve its strength. The fiber-reinforced polyolefin composition obtained was usually one in which a polyolefin was mixed with short reinforcing fibers, followed by extrusion of the mixture. However, a disadvantage of this process is that the fibers break during grinding within the extruder. This process cannot therefore fulfill the requirement for 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 to unwind a continuous 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.
In the automotive industry and similar sectors increasingly high impact strength is being demanded, and conventional long-fiber-reinforced polyolefins cannot fulfill this requirement. For further improvement in impact strength it is possible to mix another thermoplastic with very good impact strength with the long-fiber-reinforced polyolefin. However, products with mechanical properties which are useful for practical purposes cannot be obtained simply by mixing the polyolefin with another plastic. The reason for this appears to be the low mutual dispersibility of the plastics. U.S. Pat. No. 5,409,763 discloses a rod- or bar-shaped long-fiber-reinforced polyolefin structure of length at least 3 mm, produced by mixing 100 parts by weight of a plastic component comprising from 99 to 50 parts by weight of a polyolefin and 1 to 50 parts by weight of a polyamide with from 10 to 200 parts by weight of a reinforcing fiber. The reinforcing fiber has the same length as the structure and its arrangement is essentially longitudinal. Another product disclosed in that publication is a product molded from a rod- or bar-shaped long-fiber-reinforced polyolefin structure of this type. The reinforcing fiber has an average fiber length of at least 1 mm when dispersed in the polyamide, and during the process penetration of the polyolefin and the polyamide occurs, thus forming a crosslinked dispersion.
The polyamide used is stronger than the polyolefin and in terms of surface tension it lies between the polyolefin and the reinforcing fiber, such as glass fiber. A rod- or bar-shaped structure is produced by mixing the polyolefin melt with the polyamide melt and immersing the reinforcing fiber into the melt, and molding the rod- or bar-shaped structure. This gives a shaped article with extremely high impact strength. Within this, the polyamide forms a network structure with the reinforcing fibers and at the same time with the polyolefin. This network structure is further improved as the fiber length increases.
SUMMARY OF THE INVENTION
It is known to be preferable to use a modified polyolefin which bears functional groups having high affinity for the polyamide. This increases the affinity between the polyolefin and the polyamide, thus allowing a network structure to be developed more readily. If the proportion of modified polyolefin is below 1% by weight the effect does not arise. If the proportion is above 50% by weight, the viscosity of the composition increases, and this can lead to difficulties in molding.
The polyolefin can be prepared by polymerization of an &agr;-olefin, such as ethylene or propylene, using a suitable catalyst.
A variety of known polyamides may be used as the polyamide. If the proportion of polyamide in the mixture is below 1% no effective improvement in impact strength is achieved. If the proportion exceeds 50%, the problem of dimensional change of the shaped article due to water absorption is exacerbated.
DETAILED DESCRIPTION OF THE INVENTION
If the proportion of reinforcing fiber is below 10 parts by weight, the fiber achieves only a slight reinforcing effect. If the proportion of reinforcing fiber exceeds 200 parts by weight, the rod- or bar-shaped structure becomes more difficult to produce, or capability for processing to give a shaped article is considerably impaired.
Compositions made from polyolefin, polyamide, modified polyolefin and glass fiber are known from the prior art. These compositions are described 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, inter alia.
Many applications demand a colored long-fiber-reinforced polyolefin structure. Addition of even small amounts of at least one dye and/or pigment has considerable effects on the mechanical properties of the polyolefin. It is known that pigments in glass-fiber-reinforced plastics cause mechanical damage to the reinforcing fiber and thus considerably impair mechanical properties.
The object of the present invention is to provide a colored long-fiber-reinforced polyolefin structure with very good mechanical properties, good heat resistance and low water absorption, and to provide an environmentally compatible and cost-effective process for producing this structure, and the use of the structure for producing shaped articles.
The object of the present invention is achieved by means of a colored long-fiber-reinforced polyolefin structure of length ≧3 mm, which comprises
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, and
e) from 0.1 to 5.0% by weight of at least one dye and/or pigment.
The present invention is characterized by the use of at least one dye and/orpigment. Unexpectedly and surprisingly, and despite the 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. Examples of pigments which may be used are titanium dioxide (white pigment), iron oxide, Sachtolit HDS (red pigments), carbon black, Renol black VE (black pigments), Sicotan Yellow 2112 (yellow pigment), and also Cobalt Green 7911 (green pigment). Other pigments which may be used are those described in Saechtling, Kunststoff-Taschenbuch [Plastics Handbook], Hanser Verlag, 27th edition, on pages 764-766, included herein by way of reference. The pigments may also be added as pigment concentrates, such as pigment pastes or masterbatches.
One preferred embodiment of the invention is a colored long-fiber-reinforced polyolefin structure which comprises
a) from 4.0 to 70% by weight of at least one polyolefin,
b) from 1.0 to 40% by weight of at least one polyamide,
c) from 0.8 to 13% by weight of at least one modified polyolefin,
d) from 10 to 65% by weight of at least one reinforcing fiber, and
e) from 0.15 to 3.0% by weight of at least one dye and/or pigment.
This composition has excellent mechanical properties and heat resistance, and very low water absorption.
One particularly preferred embodiment of the inv
Berndt Heinz
Borgner Thomas
Heydweiller Joachim
Thomas Gabriele
Connolly Bove & Lodge & Hutz LLP
Kelly Cynthia H.
Thompson Camie S.
Ticona GmbH
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