Thermoplastic molding materials

Details Thermoplastic molding materials Thermoplastic molding materials

2001-08-09

2003-11-18

Mullis, Jeffrey (Department: 1711)

Plastic and nonmetallic article shaping or treating: processes

Direct application of fluid pressure differential to...

C264S510000, C525S064000, C525S071000

Reexamination Certificate

active

06649117

ABSTRACT:

The invention relates to thermoplastic molding compositions based on ASA (acrylonitrile-styrene-acrylate) with improved flowability and improved extrusion properties. The invention further relates to a process for preparing these thermoplastic molding compositions, their use, and also, produced therefrom, reduced-gloss and antistatic films and moldings, and coatings with reduced gloss, and the use of these.
There is a wide variety of application sectors for thermoplastic molding compositions, and there is therefore a wide variety of known molding compositions with differing mixes for different application sectors.
EP-A 0 526 813 describes polymer blends for flexible films. These are made from a graft copolymer of vinyl monomers as graft shell on an acrylate rubber as graft base, a partially crosslinked copolymer rubber based on acrylate, an uncrosslinked polymer based on styrene compounds and/or on acrylic compounds and an ethylene-vinyl acetate copolymer. The plastic material which can be obtained, in which no PVC is present, is suitable for producing leather-like films. However, these mixtures tend to discolor undesirably during processing and have a disadvantageous relationship between tensile strength and elongation at break. Films of this type also exhibit relatively severe fogging when processed by methods similar to those conventionally used.
DE-A 31 49 358 relates to thermoplastic molding compositions obtainable from a graft copolymer with a core made from a crosslinked alkyl acrylate and, if desired, comonomers and a shell obtainable by polymerizing a vinylaromatic monomer, with an ethylenically unsaturated monomer and with a copolymer obtainable by polymerizing a vinylaromatic monomer and with an ethylenically unsaturated monomer. Films produced from these thermoplastic molding compositions have the disadvantage of excessively low elongation at break together with excessively high hardness. Molding compositions of this type are moreover unsuitable for soft coextrusion compositions.
Plastic films with reduced-gloss surface and leather-like appearance are used, for example, for interior trim in motor vehicles, in the construction of buildings and in the sanitary and furniture sectors. The plastic usually used nowadays is PVC, mixed with a variety of vinyl polymers and plasticizers. These films are not fully aging-resistant at high temperatures, and they comprise volatile constituents and naturally contain halogen (see DE-A 42 11 415).
The use of alkylene oxide polymers (component (D)) in thermoplastic molding compositions is known.
AU-A 93 52 355 relates to thermoplastic synthetic mixtures for producing degradable single-use plastic products. These mixtures comprise from 65 to 95% by weight of high-molecular-weight polyethylene oxide, at least one high-molecular-weight thermoplastic polymer selected from the group consisting of nylon-11, nylon-12, polyethylene-co-acrylic acid, polyethylene-co-methacrylic acid, polyethylene-co-vinyl acetate and polyethylene-co-vinyl alcohol.
EP-A 0 603 147 describes antistatic thermoplastic styrene (co)polymers which comprise high-molecular-weight polyethylene oxide (average molecular weight from 100,000 to 400,000), a lithium salt and ethylene glycol, diethylene glycol or triethylene glycol.
The use of alkylene oxide polymers in thermoplastic molding compositions based on SAN and/or ABS is disclosed in a number of documents.
FR-B 1 239 902 describes the use of additives for rendering polymers antistatic. Examples of additives used are ethylene oxide-propylene oxide three-block copolymers. These antistats can be used in PVC, polymethacrylate, polyethylene, polystyrene or molding compositions made of ABS (acrylonitrile-butadiene-styrene).
EP-A 0 018 591 describes molding compositions which comprise styrene-acrylonitrile copolymers. These molding compositions also comprise linear three-block copolymers built up from two terminal ethylene oxide blocks and from a central propylene oxide block. The alkylene oxide three-block copolymers are used as lubricants. They affect the processing properties of styrene-acrylonitrile copolymers, in particular processing properties in injection molding. Adding the three-block polymers has no substantial effect on the mechanical properties.
There has been no previous disclosure of the use of alkylene oxide polymers in molding compositions which comprise mainly ASA graft rubber with SAN, and comprise at least one olefin copolymer.
It is an object of the present invention, therefore, to provide thermoplastic molding compositions which may be used either as films or else as soft, reduced-gloss surface coatings of hard, brittle or impact-resistant thermoplastics. These molding compositions are applied to coatings, for example by coextrusion, and for this have to have good flowability. A further object was to provide a process for preparing these thermoplastic molding compositions, as well as the use of the novel molding compositions for producing moldings or films, and as coextrusion compositions. The films should have reduced susceptibility to electrostatic charging and reduced Shore hardness. Further objects are the provision of films and moldings made from the novel molding compositions which have good and balanced mechanical properties, and the use of these.
We have found that this object is achieved by thermoplastic molding compositions, essentially comprising
(A) from 20 to 99% by weight of at least one graph copolymer, essentially obtainable from
(a1) from 30 to 90% by weight of a core, obtainable by polymerizing a monomer mixture, essentially consisting of
(a11) from 80 to 99.99% by weight of at least one C
1
-C
10
-alkyl acrylate,
(a12) from 0.01 to 20% by weight of at least one copolymerizable, polyfunctional, crosslinking monomer, and
(a13) from 0 to 40% by weight, based on the total weight of components (a11) and (a12), of at least one other copolymerizable, monoethylenically unsaturated monomer, and
(a2) from 10 to 70% by weight of a graft shell, obtainable by polymerizing a monomer mixture in the presence of the core (a1), and essentially consisting of
(a21) from 50 to 100% by weight of at least one styrene compound of the formula (I)
 where R
1
and R
2
, independently of one another, are hydrogen or C
1
-C
8
-alkyl and/or of a C
1
-C
8
-alkyl (meth)acrylate, and
(a22) from 0 to 50% by weight of at least one monofunctional comonomer, and
(B) from 1 to 80% by weight of a copolymer obtainable from at least one alpha-olefin and from at least one polar comonomer, with the proviso that the monomers used are not vinyl acetate or any vinylaromatic monomer, and
(C) from 0 to 80% by weight of a thermoplastic polymer, obtainable by polymerizing a monomer mixture, essentially consisting of
(c1) from 50 to 100% by weight of at least one vinylaromatic monomer and/or of a C
1
-C
8
-alkyl (meth)acrylate, and
(c2) from 0 to 50% by weight of at least one monofunctional comonomer, and
(D) from 0.1 to 15% by weight of a three-block polymer made from
(d1) from 5 to 90% by weight of polyethylene oxide and
(d2) from 95 to 10% by weight of polypropylene oxide
and having a central polypropylene oxide block with a molar mass of from 800 to 5000 g/mol, and terminal blocks made from polyethylene oxide,
where components A to D give 100% by weight in total.
These molding compositions feature excellent flowability and very good extrusion properties. They may be extruded to give films, or coated thermoformed sheets with a soft, mat surface, with consistent product quality or they may be processed to give moldings, for example by injection molding. The molding compositions have a high level of mechanical strength and heat resistance. They give good coextrusion. Films and moldings made from these molding compositions have reduced surface gloss and reduced electrostatic charging. They are suitable for internal trim of motor vehicles and for use in the construction of houses and in the sanitary and furniture sectors.
This type of combination of properties is achieved by the novel molding compositions. The fundamental prope

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