Glass-fiber-reinforced thermoplastic ABS compositions

Details Glass-fiber-reinforced thermoplastic ABS compositions Glass-fiber-reinforced thermoplastic ABS compositions

1998-10-23

2001-04-03

Hoke, Veronica P. (Department: 1714)

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

Synthetic resins

Processes of preparing a desired or intentional composition...

C524S182000, C524S494000

Reexamination Certificate

active

06211269

ABSTRACT:

This invention relates to glass-fiber-reinforced thermoplastic ABS compositions containing special additives for improving the coupling between polymer and glass fibers.
Blends of graft polymers of resin-forming monomers on rubbers, thermoplastic polymers (resins) and fillers are known (H. G. Elias, “Makromoleküle”, Hüthig & Wepf Verlag Basel/Heidelberg/New York 1981, pages 994 et seq.) because the strength and rigidity of non-reinforced plastics are unsatisfactory for numerous applications. Most of these disadvantages can be overcome by incorporation of reinforcing materials. Thus, glass fibers of modified minerals, for example, are added to the plastics.
To reinforce plastics with glass fibers, a suitable size normally has first to be applied to the glass fibers, more particularly to low-alkali glass fibers, to promote firm adhesion between the plastic matrix and the reinforcing material. In practice, the glass fibers are finished with a spinning size. For the production of glass filaments, the size mainly contains binders in the form of an aqueous dispersion for bunching the many individual fibers together and also suitable coupling agents (for example trimethoxyaminopropyl silane) which are intended to guarantee better adhesion between filler and polymer matrix and also effective incorporation of the fillers. In addition, the size may contain auxiliaries for the processing of the filaments in subsequent process steps (see K. L. Löwenstein, “The Manufacturing Technology of Continuous Glass Fibres”, Elsevier Scientific Publishing Company, Amsterdam/London/New York, 1973, pages 191-233).
In most cases, reinforcement with glass fibers leads to only a partial improvement in the properties. Whereas rigidity and strength are generally increased to a considerable extent, elasticity and particularly impact strength are often clearly reduced. To achieve effective reinforcement with a minimal loss of toughness, firm adhesion or coupling must exist between the matrix and the glass fibers.
Japanese patent application 56/095 953 describes glass-fiber-reinforced thermoplastic molding compositions consisting of glass-fiber-containing polymer pellets and glass-fiber-free thermoplastic resins. The glass-fiber-containing polymer pellets are produced by polymerization of styrene/acrylonitrile in the presence of soluble, i.e. uncrosslinked, acid-functional acrylate rubber and glass fibers in suspension and subsequent drying. In this process (suspension polymerization and drying in the presence of glass fibers), which is difficult to control on an industrial scale, the glass fibers are not firmly phasecoupled to the thermoplastic matrix.
DE-OS 3 436 602 describes glass-fiber-reinforced thermoplastic resin compounds consisting of a polymer resin A) of an aromatic vinyl monomer (styrene), unsaturated nitrile (acrylonitrile) and methacrylates, a polymer resin B) of maleic imides, aromatic vinyl compounds (styrene) and vinyl monomers (acrylonitrile) and a polymer resin C) of aromatic vinyl monomers (styrene) and unsaturated nitrile monomers (acrylonitrile) and a graft rubber D). A) is prepared in the presence of the glass fibers by suspension polymerization. The mixture has particularly high heat resistance. It is evident from its physical properties that the coupling of the glass fibers to the resin is inadequate.
According to Australian patent 86 60580, high-impact resins are obtained from copolymers of aromatic vinyl compounds and unsaturated nitrile containing less than 15% by weight rubber providing the rubber is added in the form of a graft polymer of a rubber core and a graft shell of aromatic vinyl compounds, vinyl cyanides and methacrylic acid derivatives. These blends may also contain glass fibers.
These reinforced plastics do not perform satisfactorily under multiaxial load so that they cannot be used for making, for example, housing parts which are exposed to impact stress.
EP-A 303 919 describes a glass-fiber-containing molding composition of A) a copolymer of an aromatic vinyl compound and acrylonitrile or methacrylonitrile and B) a special terpolymer of an aromatic vinyl compound, acrylonitrile (or methacrylonitrile) or methyl acrylate (or methyl methacrylate) and tert. butyl acrylate or methacrylate, which may additionally contain a graft rubber. However, a monomer which is not available on an industrial scale is required for the production of these molding compositions.
Accordingly, there is a need for glass-fiber-containing thermoplastic ABS compositions which are based on conventionally produced ABS molding compositions successfully used in non-reinforced form, but which show firm adhesion or phase coupling between the plastic matrix and the glass fibers and, hence, improved properties.
The present invention relates to glass-fiber-reinforced thermoplastic ABS compositions containing up to 5% by weight (preferred ranges include 0.5 to 5%, 1 to 5% and 0.5 to 2% by weight) of a special tin-containing organic compound.
In a preferred embodiment, the invention relates to thermoplastic ABS compositions of:
35 to 89% by weight and preferably 40 to 85% by weight of a mixture of
A) a graft polymer of resin-forming monomers on a rubber,
B) a thermoplastic resin and
C) 0.1 to 5% by weight and, more particularly, 0.25 to 4% by weight of a tin-containing organic compound corresponding to formula (I) and/or (II)
 in which
R
1
and R
2
=C
1-12
alkyl,
R
3
, R
4
=C
1-18
alkyl,
R
5
=—(CH
2
)—
n
, —CH═CH—, —CH═CR
1
—,
X=H, 1 equivalent of an alkali metal, preferably Na or K, ½ equivalent of an alkaline earth metal, preferably Mg or Ca,
n=2-8,
and
D) 10 to 60% by weight, preferably 10 to 50% by weight, more preferably 12 to 40% by weight and, most preferably, 12 to 25% by weight glass fibers.
The thermoplastic compositions according to the invention show improved adhesion between the plastic and the glass fibers and exhibit improved technological properties, such as increased toughness coupled with very good processability and high heat resistance.
In one particular embodiment, mixture of A) and B) according to the invention are mixtures of
A-a) 5 to 70% by weight of one or more graft polymers and
B)-a) 95 to 30% by weight of one or more thermoplastic resins.
Graft products (A-a) are preferably polymers obtained by polymerization of resin-forming monomers in the presence of a rubber as graft base. The percentage rubber content is between 5 and 80% by weight and is determined inter alia by the polymerization process.
Particularly suitable rubbers (graft base) are butadiene, butadiene/acrylonitrile and butadiene/styrene polymers and also butadiene/styrene block polymers. Other suitable rubbers are acrylate polymers, acrylate/vinyl ether copolymers and EPDM terpolymers. Resin-forming monomers are mainly styrene, mixtures of styrene and acrylonitrile, preferably in a ratio by weight of 90:10 to 60:40, mixtures of styrene and methyl methacrylate, preferably in a ratio by weight of 5:95 to 95:5, and styrene/acrylonitrile/methyl methacrylate mixtures.
The production of the graft polymers is known:
The resin-forming monomers (graft monomers) may be polymerized in the presence of a latex of the rubber (graft base) in emulsion using radical initiators, the average particle diameter of the rubber latex particles generally being from 0.04 to 0.8 &mgr;m and preferably from 0.05 to 0.6 &mgr;m. If the graft base is partly crosslinked and providing certain graft monomer/graft base ratios are maintained, the particle size of the latex of the graft base also determines the particle size of the graft polymer. The graft shell of chains of the polymer of the graft monomers attached chemically to the rubber particles is relatively thin and does not significantly alter the diameter of the rubber particle. “Diameter” or “particle size” is the mean diameter d
50
, i.e. the diameter above which the diameters of 50% by weight of the particles and below which the diameters of 50% by weight of the particles lie. The grafting reaction is generally incomplete. In addit

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