Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1999-03-03
2001-08-28
Gorr, Rachel (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S288000, C525S383000, C524S504000, C524S858000, C524S855000, C524S881000
Reexamination Certificate
active
06281288
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a reinforced molding material which contains a filler or a fibrous reinforcing material and a silane-grafted polyolefin.
2. Discussion of the Background
The reinforcement of thermoplastics by means of a filler or of a fibrous reinforcing material such as, for example, glass fibers, has long been part of the prior art. By means of this measure, the modulus of elasticity can be very effectively increased but the fracture behavior is often unsatisfactory, which is manifest, for example, in substantially reduced impact strength. In these cases, it was found that there is only poor binding or no binding at all between polymer matrix and reinforcing material. The tensile strength, too, is greatly dependent on the binding so that the full potential of this material combination can be utilized only in the case of strong interphase adhesion. This problem is encountered in particular in the case of molding materials based on polyolefins or polyesters.
One possibility for increasing the interphase adhesion between polymer matrix and reinforcing material is the use of a size. Although extensive work in this context has long been known, the result is still unsatisfactory in many cases, especially since the sizing of the reinforcing material constitutes an additional complication in the process.
Japanese patent application JP-A-58217532 states that glass fiber-reinforced polyolefin molding materials having excellent mechanical properties are obtained if a polyolefin is used which was subjected to free radical grafting with an aliphatically unsaturated trialkoxysilane.
Over and above the fact that this implies limitation to polyolefin molding materials, this method also has some disadvantages which prevent its use. On the one hand, the total matrix material is in fact remelted and is functionalized during this procedure, which gives rise to considerable additional process costs. In particular, a substantial amount of the expensive silane must be used, the unconverted proportion having to be removed subsequently. In addition, undesired changes in the melt viscosity result, free radical degradation taking place in the case of polypropylene and free radical synthesis in the case of polyethylene. In addition, the fact that the incorporation of glass fibers into a highly viscous polymer melt requires high shear forces is a general disadvantage, which may lead to a decrease in the molecular weight in the case of a matrix- in particular, however, this leads to considerable mechanical comminution of the fibers and hence to a deterioration in the mechanical properties. In general, establishing a desired specification in a controlled manner is virtually impossible in this way.
Japanese patent application JP-A-54064545 describes molding materials which contain
a) 100 parts by weight of polyolefin,
b) from 2 to 100 parts by weight of a polymer in which a silane, for example, vinyltrimethoxysilane, has been grafted onto polyethylene, a copolymer based on ethylene or a halogenated polymer derived therefrom, and
c) from 10 to 25 parts by weight of a reinforcing material.
Here too, the incorporation of the reinforcing material into the highly viscous polymer melt is problematic.
A further, very specific molding material which consists of many components and contains a silane-modified polypropylene is described in German Offenlegungsschrift 41 36 687.
SUMMARY OF THE INVENTION
It was an object of the present invention to provide reinforced molding materials which have a higher tensile strength and improved impact strength and in the preparation of which unsized reinforcing materials can be used. According to a further object, it should be possible further to increase the heat deflection temperature of such molding materials. Furthermore, the reinforced molding materials should be capable of being prepared by a simplified process, it being possible to establish desired specifications in a controlled manner.
This object is achieved by a molding material which comprises:
(a) from 0 to 98 parts by weight of one or more thermoplastics,
(b) from 2 to 100 parts by weight of a substantially amorphous polyolefin which has been subjected to free radical grafting with a silane which has at least one olefinic double bond and one to three alkoxy groups bonded directly to the silicon, this grafted polyolefin having a melt viscosity at 190° C. in the range from 100 to 50,000 mPas, measured on the basis of DIN 53 019 in a rotational viscometer at a shear rate of 30.5 s
−1
, the parts by weight of (a) and (b) summing to 100, and
(c) from 0.5 to 400 parts by weight of a reinforcing material, with the exception of those molding materials in which less than 28 parts by weight of barite are used as reinforcing material.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The thermoplastic (component (a)) may be, for example, a polyolefin, a polystyrene, a polyphenylene ether, a polycondensate, such as polyester or polyamide, a polyurethane and/or a rubber.
Suitable polyolefins are in principle any polyolefin of the prior art, for example polyethylene, polypropylene and poly-1-butene, as well as copolymers of ethene, propene or 1-butene, either as a random copolymer, such as, for example LLDPE or propene/ethene random copolymers containing about 1-15% by weight of ethene, or as block copolymers such as, for example, propenelethene block copolymers. The polyolefin may also be a substantially amorphous polyolefin, as may be used as a grafting base for the component (b). The polyolefin may also contain a rubber as an impact modifier, for example ethene/propene rubber (EPM) or ethene/propene/diene rubber (EPDM). All these polymers are well known to a person skilled in the art, making further description superfluous.
The polystyrene can be used either as such or in rubber-modified form, the choice of the rubber, for example butadiene rubber (BR), EPDM, styrene/butadiene/styrene block copolymers (SBS) or polyoctenamer (TOR), being uncritical. The polystyrene may be present as a homopolymer; however, in order to increase the heat deflection temperature, it may also contain comonomers, such as &agr;-methylstyrene, acrylonitrile, methyl methacrylate or N-phenylmaleimide, as polymerized units.
The polyphenylene ethers are formed by oxidative coupling of 2,6-dialkylphenols; they are described, for example, in U.S. Pat. Nos. 3,306,874 and 3,306,875 and in EP-A-0 122 394. Usually, they are used as a polymer blend with polystyrene.
Suitable polyesters are, for example, polyethylene terephthalate, polybutylene terephthalate or copolyesters which contain 1,4-cyclohexanedimethanol as a comonomer.
The polyamide (PA) used may be of any available type, for example PA 46, PA 6, PA 66, PA 612, PA 1010, PA 1012, PA 11, PA 12, PA 1212 or PA 6,3 T. These types need not be explained in more detail to a person skilled in the art.
Suitable polyurethanes are those which can be processed by a thermoplastic method, the type of monomers used being uncritical.
For example, the following may be mentioned as a suitable rubber: EPM, EPDM, SBS, hydrogenated styrenelbutadiene/styrene block polymers (SEBS), SIS, styrene/butadiene rubber (SBR), butadiene rubber (BR), silicone rubber, natural rubber (NR), butyl rubber and chloroprene rubber. A person skilled in the art knows that such rubbers may be present in the rubber compounds as mixtures with a plurality of rubber types, the compounds usually also containing plasticizer oils, vulcanizing agents and optionally vulcanization accelerators, in addition to fillers.
Generally preferred thermoplastics are those which are semicrystalline.
Furthermore, polyolefins are preferred owing to the good compatibility with the component (b).
The molding material contains preferably from 1 to 97 parts by weight, particularly preferably from 10 to 96 parts by weight and very particularly preferably from 20 to 95 parts by weight of the thermoplastic or thermoplastics.
For example, atactic polypropylene, atactic poly-1-butene, ethene/propene copolymers, e
Bickert Peter
Laven Ralf
Wey Hans Guenther
Degussa-Huels Aktiengesellschaft
Gorr Rachel
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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