Patent Description:
Styrene-butadiene block copolymers are known for years to provide effective modifiers to gain impact strength in blends with styrene-methyl methacrylate copolymers while still maintaining a good transparency and/or low haze.

<CIT> and <CIT> describe blends of SMMA copolymers (MMA <NUM> to <NUM> wt. -%) and SBC with the SBC having a tapered, linear or radial, di-block (vinyl aromatic monomer-conjugated diene) or tri-block (vinyl aromatic monomer-conjugated diene-vinyl aromatic monomer) molecular architecture. The optical properties such as clarity and haze as well as the mechanical properties such as toughness (Notched Izod Impact strength) of the obtained materials are still in need of improvement.

<CIT> discloses a polymer composition comprising <NUM> to <NUM> wt. -% of a SMMA copolymer (MMA content: <NUM> to <NUM> wt. -%) and <NUM> to <NUM> wt. -% of a star-shaped vinyl- aromatic diene block copolymer (diene content: <NUM> to <NUM> wt. -%) comprising at least two terminal vinyl-aromatic polymer blocks S<NUM> and S<NUM> and at least one random vinyl-aromatic/diene copolymer block (B/S). Said compositions show an improved toughness and clarity. However, the heat resistance and the scratch resistance (i.e. surface hardness) of said prior art compositions are still in need of improvement.

It is an object of the invention to provide a molding composition comprising SMMA copolymers and SBC block copolymers with a good balance of stiffness and toughness, with a high surface hardness and Vicat softening temperature while maintaining a high transmittance and clarity. It is a further object of the invention to provide a SMMA/SBC-molding composition having an improved processability (i.e. in an extrusion process).

According to the invention, this object is achieved by providing a molding composition according to the claims.

One aspect of the invention is a molding composition comprising (or consisting of) the components (a), (b) and (c):.

wherein the total amount of components (a), (b) and (c) is <NUM> wt.

In this document, wt. -% means percent by weight.

A random copolymer (a) means a copolymer having a statistical distribution of the polymerized units of the vinylaromatic monomer and methyl methacrylate.

Preferably the molding composition according to the invention comprises (or consists of) components (a), (b) and (c) in the following amounts:.

More preferably the molding composition according to the invention comprises (or consists of) components (a), (b) and (c) in the following amounts:.

In particular preferred is a molding composition according to the invention comprising or (consisting of):.

If component (c) is present, its minimum amount is usually <NUM> wt.

Preferred are molding compositions according to the invention wherein component (a) forms a continuous phase in which component (b) is finely dispersed.

Preferred are molding compositions wherein the values of the refractive index of components (a) and (b) differ no more than <NUM>, preferably <NUM>, more preferably <NUM>. This results in a product of particular high clarity and low haze.

In one preferred embodiment, the molding composition according to the invention consists of the components (a), (b) and optionally (c).

Preferred are random copolymers (a) - as component (a) - made from <NUM> to <NUM> wt. -% vinylaromatic monomer (a11), in particular styrene, and <NUM> to <NUM> wt. -% methyl methacrylate (a12); more preferred are random copolymers (a) made from <NUM> to <NUM> wt. -% (a11) and <NUM> to <NUM> wt. In said compositions the total amount of (a11) and (a12) is <NUM> wt.

Styrene-methyl methacrylate (SMMA) copolymers (a) may be obtained in a known manner by bulk, solution, suspension, precipitation or emulsion polymerization. Details of these processes are described, for example, in Kunststoffhandbuch, ed. Vieweg and G. Daumiller, Vol. V "Polystyrol", Carl-Hanser-Verlag Munich, <NUM>, p. SMMA copolymers (a) are known products which are commercially available e.g. from Ineos Styrolution (Frankfurt, Germany) as NAS® XC.

The at least one, preferably one, vinylaromatic-diene block copolymer (b) - as component (b) - may be a linear or star-shaped block copolymer and comprises at least two hard blocks S (preferably terminal blocks) made from vinylaromatic monomers, in particular styrene, and at least one soft block B made from dienes and/or at least one soft block B/S made from dienes and vinylaromatic monomers.

Generally - based on the entire block copolymer - the proportion of the diene is from <NUM> to <NUM> wt. -%, and the proportion of the vinylaromatic monomer is from <NUM> to <NUM> wt.

Preferably - based on the entire block copolymer - the proportion of the diene is from <NUM> to <NUM> wt. -%, and the proportion of the vinylaromatic monomer is from <NUM> to <NUM> wt. Vinyl aromatic monomers which may be used for the hard (polymer) blocks S or else for the soft (copolymer) block B/S are styrene, α-methylstyrene, p-methylstyrene, ethylstyrene, tert-butylstyrene, vinyl toluene or mixtures of these, preferably styrene. The hard (polymer) blocks S of the block copolymer (b) are hard phases with a glass transition temperature (Tg) > <NUM>.

The hard blocks S can be made from <NUM> to <NUM> wt. -% of at least one vinylaromatic monomer and <NUM> to <NUM> wt. -% of at least one diene, preferably the hard blocks S are homopolymers made from vinylaromatic monomers, in particular styrene.

Suitable dienes which may be used for the preparation of component (b) are conjugated dienes. Preferred dienes for the at least one soft block B or the at least one soft block B/S (or optionally for the hard blocks S) are <NUM>,<NUM>-butadiene, isoprene, <NUM>,<NUM>-dimethylbutadiene, <NUM>,<NUM>-pentadiene, <NUM>,<NUM>-hexadienes or piperylene or mixtures of these, particularly preferably <NUM>,<NUM>-butadiene. The soft (polymer) block B and/or soft (copolymer) block B/S is a soft phase with a Tg < <NUM>.

The soft block B may be made from <NUM> to <NUM> wt. -% of at least one diene and <NUM> to <NUM> wt. - % of at least one vinylaromatic monomer, preferably the soft block B is a homopolymer made from a conjugated diene, in particular <NUM>,<NUM>-butadiene.

Often the soft block is a block B/S, in particular a random block B/S. A "random" block B/S means a copolymer block having a statistical distribution of the polymerized units of the vinylaromatic monomers and dienes.

Often the (copolymer) block B/S, in particular the random copolymer block B/S, is made from more than <NUM> to <NUM> wt. -%, in particular <NUM> to <NUM> wt. -%, vinylaromatic monomer, in particular styrene, and from <NUM> to less than <NUM> wt. -%, in particular <NUM> to <NUM> wt. -%, diene, in particular <NUM>,<NUM>-butadiene, wherein the total amount of the vinyl aromatic monomer and the diene is <NUM> wt.

Preferably block copolymer (b) is a linear block copolymer with two hard blocks S, preferably terminal hard blocks S, and, at least one soft block B and/or at least one soft block B/S.

There may also be more than one, preferably random, (copolymer) block B/S. Often block copolymer (b) comprises at least <NUM>, in particular random, soft (copolymer) blocks (B/S), and (B/S)<NUM> having different proportions of vinylaromatic monomers and therefore different glass transition temperatures. For all copolymer blocks B/S such as (B/S)<NUM>, (B/S)<NUM> etc, Tg is < <NUM>, generally in the range between -<NUM>° to <NUM>, preferably in the range from -<NUM> to -<NUM>, particularly preferably from -<NUM> to -<NUM>. Tg is measured by methods known to the SBC-polymer chemist.

According to one embodiment block copolymer (b) is a block copolymer of the structure S-B-S, in particular a styrene-butadiene block copolymer of the structure S-B-S.

According to an embodiment block copolymer (b) is a block copolymer of the structure S-B/S-S, in particular a styrene-butadiene block copolymer of the structure S-B/S-S.

The block copolymers (b) are prepared preferably by sequential anionic polymerization. The aforementioned SBC products are known. Their preparation is described in "<NPL>), in <NPL>) and in <CIT> (col. <NUM> to col. <NUM>, line <NUM>). Block copolymer (b) is a known product and commercially available as Calprene® 743X from Dynasol, USA.

Optionally the thermoplastic molding composition may comprise up to <NUM> wt. -%, preferably <NUM> to <NUM> wt. -%, of at least one further additive and/or processing aids (c) (as component (c)).

Suitable additives and/or processing aids (c) include all substances customarily employed for processing or finishing the polymers, except of fillers/fibers and pigments (see e.g. "<NPL>).

Preferred additives and/or processing aids (c) are such as stabilizers (e.g. UV-stabilizers), oxidation retarders, anti-oxidants, agents to counter thermal decomposition and decomposition due to light, lubricants and dyes.

These additives and/or processing aids (c) may be admixed at any stage of the manufacturing operation, but preferably at an early stage in order to profit early on from the stabilizing effects (or other specific effects) of the added substance.

Suitable antioxidants are, e.g., one or more compounds selected from monophosphite-based antioxidants, diphosphite-based antioxidants and sterically hindered phenolic antioxidants. If one or more antioxidants are present, they are preferably selected from monophosphite-based antioxidants, such as trisubstituted monophosphite derivatives, diphosphite-based antioxidants, such as substituted pentaerythrirol diphosphite derivatives and sterically hindered phenolic antioxidants, such as <NUM>,<NUM>-di-tertbutylphenolic derivatives.

Suitable lubricants/glidants and demolding agents include stearic acids, stearyl alcohol, stearic esters, amide waxes (bisstearylamide, in particular ethylenebisstearamide), polyolefin waxes and/or generally higher fatty acids, derivatives thereof and corresponding fatty acid mixtures comprising <NUM> to <NUM> carbon atoms.

Suitable dyes are any of the dyes which can be used for the transparent, semitransparent, or non-transparent coloring of polymers, in particular those dyes which are suitable for coloring styrene copolymers. Dyes of this type are known to the skilled worker.

Examples of oxidation retarders and heat stabilizers are halides of the metals from group I of the periodic table, examples being sodium, potassium and/or lithium halides, optionally in combination with copper (I) halides, e.g., chlorides, bromides, iodides, sterically hindered phenols, hydroquinones, different substituted representatives of these groups, and mixtures thereof, in concentrations of up to <NUM> wt. -%, based on the weight of the molding composition.

Examples of suitable stabilizers to counter the effect of light (e. g UV-stabilizers) are various substituted resorcinols, salicylates, benzotriazoles, benzophenones, and HALS (hindered amine light stabilizers), for example those commercially available as Tinuvin®, which are generally used in amounts of up to <NUM> wt. -%, based on the molding composition.

A further aspect of the invention is a process for the preparation of a molding composition according to the invention by melt-mixing of components (a), (b) and, if appropriate, component (c). Preferably the melt-mixing of the components (a), (b) and, if appropriate, (c) is performed in an extruder, preferably a twin screw extruder.

The melt-mixing may be performed, preferably in an extruder, at temperatures in the range of from <NUM> to <NUM>.

Preferably melt-mixing is performed in an extruder at temperatures in the range of from <NUM> to <NUM>.

The molding composition obtained by said process shows a good processability and thus can be easily processed, i.e. molded to any desired shape e.g. by extrusion and hot molding (e.g. injection molding).

Accordingly a further aspect of the invention is a shaped article produced from the molding composition according to the invention.

The molding composition according to the invention and shaped articles produced therefrom show a good balance of stiffness and toughness, with a high surface hardness and Vicat softening temperature while maintaining a high transmittance and clarity. They can advantageously be used for many applications.

A further subject of the invention is the use of molding compositions according to the invention and shaped articles produced therefrom for various applications for housewares, home appliances, thermoformed packaging and blow molded bottles.

The examples, Figures and the patent claims provide further illustrate the invention.

Tensile stress at yield and tensile strain at break were determined in the test according to norm ASTM D638 -<NUM>.

Flexural modulus was determined in the test according to ASTM D790 -<NUM>.

Melt flow rate (MFR) was determined according to ASTM D1238 at <NUM> and <NUM>.

Gardner impact strength was determined in accordance with ASTM D5420 -<NUM>.

Notched and un-notched Izod impact strength was determined in accordance with ASTM D256 -<NUM> (<NUM>).

Vicat softening temperature (VST) was determined according to ASTM D1525 (<NUM> N force and <NUM>/hour rate).

Rockwell hardness was determined according to ASTM D785.

Haze and optical properties (transmission, clarity) were determined in accordance with ASTM D1003.

The materials as shown in Tables <NUM> to <NUM> were melt-mixed using a <NUM> twin screw extruder with zone temperatures set from <NUM> to <NUM>. From the obtained molding compositions specimens were injection molded and the parts tested for their mechanical and optical properties. Tables <NUM> to <NUM> show the properties of the injection molded specimens made as a function of the block copolymer (b) content for examples <NUM> to <NUM>.

Tables <NUM> to <NUM> further evidence the benefit of samples according to the invention (Examples <NUM> to <NUM>) as compared to current commercial styrenic impact modified clear molding compositions such as Terlux® <NUM>, Terlux <NUM> (both methacrylate acrylonitrile butadiene styrene (MABS) resins), Zylar® <NUM> (impact modified styrene acrylic copolymer (methyl methacrylate butadiene styrene (MBS) resin), Zylar <NUM> EX (MBS resin) and Denka TH-<NUM> (MBS resin) used in comparative Examples <NUM> to <NUM>.

As shown by Tables <NUM> to <NUM> the molding compositions according to the invention (examples <NUM> to <NUM>) create a better balance of stiffness and toughness, with higher hardness and Vicat softening temperature being achieved without a sacrifice in appearance compared to current commercial styrenic impact modified clear molding compositions. By using a rubber component (block copolymer (b)) with a specific high diene content in combination with a specific SMMA copolymer having a high MMA-content, lower amounts of the rubber component are needed, which provides an SMMA continuous phase with the rubber component (b) finely dispersed therein while maintaining high transmittance and clarity.

<FIG> are TEM images which show the morphology of SMMA/SBS molding compositions - obtained by an extrusion molding process - which differ only in the amount of SBS rubber component (b).

<FIG> shows a SMMA/SBS molding composition according to the invention having a SBS rubber component content of <NUM> wt.

<FIG> shows a SMMA/SBS molding composition (non-inventive) having a SBS rubber component content of <NUM> wt.

The molding compositions according to the invention with <NUM> wt. -% or <NUM> wt. -% SBS rubber component (b) (cp. <FIG>) show an SMMA continuous phase in which the SBS rubber component is finely dispersed whereas a corresponding molding composition with <NUM> wt. -% SBS rubber component has a changed - i.e. discontinuous - morphology for the SMMA (cp.

<FIG> is a TEM image which shows an impact modified SMMA copolymer according to comparative example <NUM> (Denka TH-<NUM>) which is made via a reactor technology by adding the rubber component to the polymerization reaction of styrene and MMA monomers.

Preferred molding compositions according to the invention form a SMMA continuous phase in which the SBS rubber component (b) is dispersed which allows for better extrusion, thermal and chemical resistance, while maintaining high transmittance and clarity (cp. <FIG> and <NUM> and Table <NUM>).

The composition comprising a SMMA copolymer and a SBC-block copolymer as described by the invention showed high clarity and ductile properties.

As shown on Tables <NUM> to <NUM> the molding compositions of Examples <NUM> to <NUM> have the optimal loading level of the SBS rubber component (B) to achieve the best balance of properties.

Table <NUM> demonstrates the benefits of the molding compositions of Examples <NUM> to <NUM> compared to current commercial styrenic impact modified clear resins (see comp. <NUM> to <NUM>). Compared to clear MABS products of comparative examples <NUM> and <NUM> - the molding compositions of examples <NUM> to <NUM> have a higher melt flow rate, tensile strength and Gardner impact strength, while maintaining similar hardness, VST, and optical properties. When comparing the molding compositions of Examples <NUM> to <NUM> to a current commercial MBS product of comparative example <NUM>, the benefit in the hardness, stiffness, and Vicat is significant.

Claim 1:
Molding composition comprising components (a), (b) and (c),
(a) <NUM> to <NUM> wt.-% of at least one random copolymer (a) made from <NUM> to <NUM> wt.-% of at least one vinylaromatic monomer (a11), in particular styrene, and <NUM> to <NUM> wt.-%, methyl methacrylate (a12);
(b) <NUM> to <NUM> wt.-% of at least one vinylaromatic-diene block copolymer (b) which comprises at least two, preferably terminal, hard blocks S made from vinylaromatic monomers, in particular styrene, and at least one soft block B made from dienes, in particular butadiene, and/or at least one soft block B/S made from dienes and vinylaromatic monomers, in particular butadiene and styrene;
where the proportion of the diene - based on the entire block copolymer (b) - is from <NUM> to <NUM> wt.-%; and
(c) <NUM> to <NUM> wt.-% of one or more additive(s) and/or processing aid(s) (c),
wherein the total amount of components (a), (b) and (c) is <NUM> wt.-%.