Polymer compound, the production and use thereof, and...

Details Polymer compound, the production and use thereof, and... Polymer compound, the production and use thereof, and...

2000-10-11

2003-02-11

Foelak, Morton (Department: 1711)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Cellular products or processes of preparing a cellular...

Reexamination Certificate

active

06518323

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a polymer compound, manufacturing method and use thereof, and sintered bodies manufactured therefrom.
BACKGROUND INFORMATION
Ceramic Injection Molding (CIM) and extrusion represent two important methods for ceramic molding. In these processes a polymer compound must be initially manufactured by dispersion of ceramic particles in a high-viscosity polymeric matrix. The desired shape is obtained by processing such a mixture by ceramic injection molding or extrusion. After removing the organic auxiliary materials (debindering) a ceramic blank is obtained, which is compressed by sintering. In order for this sintering to result in a dense body, the content of ceramic solids in the blank must be sufficiently high, over 40% by volume, i.e., the polymer compound must also be filled at least 40% in this case.
Powders with particle sizes in the nanometer range are always present in the agglomerated form. The strength of the agglomerates, known as an agglomerate hardness, depends on the previous history of the powder. The spectrum ranges from Van der Waals interaction forces to hydrogen bridge bonds to true sintering necks. In order to reduce the tendency to agglomerate, the powder surfaces are protected with synthetic auxiliary materials. It is, however, considered a disadvantage in this case that no high temperatures can be used in producing the powder, so that the powders often still contain amorphous components. Furthermore, it is also considered disadvantageous that auxiliary materials interfere with subsequent processing.
In manufacturing ceramic blanks by extrusion or CIM and in producing highly filled plastics, normally powders whose specific surface area does not exceed 15 m
2
/g are currently used. Thus, powders with a relatively low specific surface area are used. This is explained by the fact that finer powders tend to agglomerate to a relatively much higher degree and their agglomerate hardness and the related energy required for breaking up these powder agglomerates is also much higher when such breaking up is even possible.
There are however applications in which a large surface area of the fillers is desirable. Interactions between fillers and the surrounding matrix increase with increasing surface area/volume ratio. The desired properties of particle-filled plastics are defined by these interactions.
Zirconium dioxide powders can be sintered using powder metallurgy to obtain bodies with less than 5% porosity. This material contains tetragonal grains, a mixture of tetragonal, monoclinic, and cubic grains, or only monoclinic grains. The tetragonal phase is stabilized by a small particle size, by doping with foreign elements, high temperature, intrinsic pressure of the material structure, and external pressure. In the following, the small particle size is referred to as particle size stabilization and the intrinsic pressure of the material structure is referred to as structure stabilization. Zirconium dioxide having mixed phase components exhibits intrinsic stresses of the structure, which stabilize the tetragonal component.
These intrinsic stresses result in very high material strength. However, zirconium dioxide having mixed phase components could be previously produced only using more than 1 mol-% of doping materials, which is considered disadvantageous. Known doping materials include Y
2
O
3
, CaO, CeO
2
, or MgO.
SUMMARY
The object of the present invention is to provide a polymer compound and a method for manufacturing it in which a dispersion of free nanocrystalline ceramic particles occurs.
This object is surprisingly achieved by a polymer compound containing a ceramic powder and a polymer, the powder having a specific surface area of more than 1.8·10
8
m
2
/m
3
and constituting more than 5 vol. % of the polymer compound, the polymer being shear resistant, and the pore sizes in the polymer compound being 3-15 nm.
It is also the object of the present invention to arrive at a zirconium dioxide sintered body having a very high strength by using a polymer compound and no more than 0.8 mol % of doping substances.
DETAILED DESCRIPTION
This object is achieved by the fact that the ceramic powder in the polymer compound according to the present invention constitutes more than 40 vol. %.
In a particularly advantageous manner, a blank manufactured from this polymer compound according to the present invention can be sintered at temperatures 200-300 K. lower than with the powders used according to the related art.
Preferably the ceramic powder constitutes more than 40 and less than 50 vol. % of the polymer compound.
Furthermore, the polymer compound preferably additionally has one or more saturated or unsaturated C
2
-C
18
carboxylic acids and/or one or more saturated or unsaturated C
2
-C
18
alkyl-dimethyl-substituted chlorosilanes and/or one or more saturated or unsaturated C
2
-C
18
alkylamines.
The ceramic powder in the polymer compound preferably has a specific surface area of more than 2.5·10
8
m
2
/m
3
.
Furthermore, a polymer compound in which the polymer includes a polyolefin, a polyester, or a polyamide as a thermoplast is preferred.
HD polyethylene, LD polyethylene, copolymers of polyethylene with vinyl acetate or butyl acrylate, polypropylene, or polypropylene grafted with acrylic acid or maleic anhydride are preferred as polyolefins.
Polyethylene copolymerized with vinyl acetate has up to 50% vinyl acetate; polyethylene polymerized with butyl acrylate has up to 30% butyl acrylate. Polyethylene grafted with maleic anhydride has 3% maleic anhydride and polypropylene grafted with acrylic acid has 6% acrylic acid.
Polyethylene terephthalate, polybutylene terephthalate, polycarbonate, or polylactone are preferred as polyesters. Polyamide 6, polyamide 12, and polyamide 66 are preferred as polyamides.
Oxides such as ZrO
2
, Al
2
O
3
, SiO
2
, MgO, TiO
2
, Y
2
O
3
, carbides, nitrides, or their mixtures are used as preferred ceramic powders. All kinds of zirconium dioxides, including those containing other metal oxides, are suitable as ceramic powders for the polymer compound. Furthermore, alpha, gamma, and delta aluminum oxides, as well as all simple and complex oxides having a basic or amphoteric surface are suitable, ceramic powders, and particularly preferred is amorphous SiO
2
(Aerosil®). When using silicon dioxide, the use of a silane dispergator is particularly preferred. Among carbides, silicon and tungsten carbides are particularly suitable. Si
3
N
4
and AlN are particularly well-suited as nitrides, an amine being preferably used as a dispergator.
The simple and very quick compounding of the powder into the mixture in a single piece of equipment, the kneader, is particularly advantageous in the method according to the present invention. Another advantage is the possibility of obtaining a heterogeneous material system whose properties are only determined by the interactions of the components at the phase boundary surfaces.
Thermoplasts having a strong tendency to thermomechanical degradation accompanied by predominant or full decomposition are not suitable for use in the method according to the present invention.
Another object of the present invention is a method for manufacturing the polymer compound using a ceramic powder and a thermoplast, the ceramic powder having a specific surface area of more than 1.8·10
8
m
2
/m
3
and the thermoplast being a shear-resistant polymer kneaded in a kneader with such a high shear force that the pore sizes in the polymer compound are 3-15 nm when the polymer is filled with at least 5 vol. % ceramic powder.
Using the method according to the present invention, even agglomerated powders can surprisingly be disintegrated down to their primary particle sizes, whereby polymer compounds and bodies manufactured thereof with the above-mentioned pore sizes can be manufactured.
In the method according to the present invention, a mixture of an agglomerated ceramic powder having a primary particle size of ≦30 nm and an agglomerated particle size of 1 &mgr;m or more, a disperg

Affiliated with

Also associated with

Rating

Polymer compound, the production and use thereof, and... does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Polymer compound, the production and use thereof, and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Polymer compound, the production and use thereof, and... will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3178700