WO2005059021A1 - Block copolymers composed of styrole monomer and diene monomer with an improved stabilizer system - Google Patents

Abstract

The invention relates to thermoplastic molding materials containing, the sum amounting to 100 weight %: a) at least one block copolymer A containing in polymerized form in relation to A: a1) 10 to 90 weight % of at least one styrole monomer and a2) 10 to 90 weight % of at least one diene monomer and as stabilizers, in relation to the molding material: b) 0.001 to 0.5 weight % of at least one phenolic acrylates B of formula (I), wherein R1, R2 and R3, independent of one another, represent hydrogen or an alkyl; radical, an aryl radical, an alkylaryl radical or a cycloalkyl radical having 1 to 20 C atoms, and Z represents tert-pentyl; c) 0.05 to 1 weight % of at least one organic phosphite C, and d) 0.001 to 1 weight % of at least one stabilizer compound D selected from amongst the sterically hindered phenols differing from phenolic acrylate B, in addition to aromatic amines.

Description

Block copolymers of styrene monomer and diene monomer with an improved stabilizer system

description

The invention relates to thermoplastic molding compositions containing, the sum being 100% by weight,

a) at least one block copolymer A, containing in polymerized form, based on A, a1) 10 to 90% by weight of at least one styrene monomer, and a2) 10 to 90% by weight of at least one diene monomer,

and as stabilizers, based on the molding compound,

b) 0.001 to 0.5% by weight of at least one phenolic acrylate B of the formula I.

in which R ¹ , R ² and R ³ independently of one another are hydrogen or an alkyl radical, aryl radical, alkylaryl radical or cycloalkyl radical having 1 to 20 C atoms, and Z is tert-pentyl,

c) 0.05 to 1 wt .-% of at least one organic phosphite C, and

d) 0.001 to 1% by weight of at least one stabilizer compound D selected from sterically hindered phenols which differ from the phenolic acrylate B and aromatic amines.

The invention further relates to a process for the production of the molding compositions, the use of the molding compositions for the production of moldings, foils, films, fibers and foams, and the moldings, foils, films, fibers and foams from the molding compositions.

Signs of aging in the case of polymers can be produced, Work on molded parts, or use of the molded parts occur and are usually based on an oxidation reaction, eg attack of the polymer by atmospheric oxygen, possibly increased by exposure to light (UV radiation). In particular, polymers based on dienes, such as rubbers or rubber-containing thermoplastics, for example block copolymers containing, for example, butadiene blocks and styrene blocks, are sensitive to aging. Oxidative aging worsens the optical and mechanical properties of the polymers (eg clouding of transparent polymers, yellowing; decrease in impact strength, elongation at break and elasticity) until they are unusable.

Antioxidants are usually used to stabilize the polymers against oxidative aging. A distinction is made between primary antioxidants such as e.g. hindered phenols and secondary aromatic amines, and secondary antioxidants such as e.g. Phosphites and thioethers. The connection classes mentioned include numerous individual connections of different structure, see for example R. Gächter, H. Müller: Plastic Additives Handbook, 4th edition, Hanser 1993, Reprint Nov. 1996, pages 1 to 128 and in particular pages 40 to 48.

Mixtures of various antioxidants, also known as stabilizer systems, are often used, e.g. primary mixed with secondary antioxidants, and thus achieves synergistic effects by mutually reinforcing the effects of the individual components.

In the case of styrene-butadiene block copolymers, so-called micro-phase separation is generally observed. The polymers usually have a co-continuous lamella or cylinder morphology on the order of a few nanometers - in contrast to the particle morphology of impact-resistant polystyrene or acrylonitrile-butadiene-styrene polymer (ABS) - and are particularly sensitive to oxidative aging, since the rubber lamellae or cylinders are exposed to high loads, in particular during polymer processing. For example, high shear forces occur during extrusion or injection molding, which lead to increased thermal-oxidative degradation of the polymer. This aging is particularly noticeable through the gel formation of the polymer: the degradation reactions result in gels in the polymer, which are noticeable in the molded part or in a film as disruptive gel particles with specks or other surface defects. Therefore highly effective stabilizers or stabilizer systems are required for these block copolymers.

US Pat. No. 5,422,389 describes the stabilization of styrene-butadiene block copolymers with an organic phosphite, for example tris (nonylphenyl) phosphite (TNPP) and a sterically hindered phenol, for example n-octadecyl- [3- (3,5-di -t-butyl-4-hydroxyphenyl) propionate (Irganox® 1076 from Ciba) or tetrakis [3- (3,5-di-t-butyl-4- hydroxyphenyl) propionyloxymethyl] methane (Irganox® 1010 from Ciba). In addition, a sterically hindered phenolic acrylate of formula 1

are used, where t-Bu stands for tert-butyl and the radicals R 1, R ₂ and R ₃ independently of one another denote hydrogen, alkyl, aryl, cycloalkyl or alkyl-substituted aryl, each having 1 to 16 carbon atoms.

US Pat. No. 4,956,408 describes the stabilization of diene-vinylaromatic copolymers with a complex acrylate of the above formula (1) (for example Sumilizer® GM from Sumitomo Chemical) in amounts of 0.05 to 1.5 phr (parts by weight per hundred parts by weight of the resin), an organic phosphite such as TNPP, and a non-acrylate-containing, sterically hindered phenol, e.g. n-octadecyl- [3- (3,5-di-t-butyl-4-hydroxyphenyopropionate ( Irganox® 1076 from Ciba) or tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxymethyl] methane (Irganox® 1010 from Ciba) The polymer of Example X contains Sumilizer® GM, TNPP and Irganox® 1076.

JP-A Sho 63-27551, published on February 5, 1988, teaches the stabilization of styrene-diene block copolymers with, based on 100 parts of the polymer, 0.05 to 5 parts of a compound of the formula 2

with Ri = C _1- alkyl, R ₂ = C _2-4 alkenyl and R ₃ = tert-butyl or cyclohexyl, and 0.05 to 5 parts of a phenolic compound, including those of the formula (3) and (4 ) R ₄ CH ₂ CH ₂ COR ₅ (3) O (R ₄ CH ₂ CH ₂ C tnOC.wH ₂ ) ₄ —— r C. (4)

where Rj

and R _{5 is} C _2-22 alkyl. Tl means parts by weight. In addition, phosphorus-containing stabilizers such as TNPP can also be used. The polymers of Examples 1 to 6, 10 and 11 according to the invention contain mixtures of 2,2-methylene-bis (6-tert-butyl-4-methylphenol) monoacrylate in amounts of 0.2 to 1.5 parts per 100 Tl. Polymer, also n-octadecyl- [3- (3 ', 5'-di-tert-butyl-4'-hydroxyphenyl) propionate or tetrakis [methylene-3- (3', 5'-di-tert- butyl 4'-hydroxyphenyl) propionate] methane, and TNPP.

According to EP-A 322 166, butadiene polymers, for example styrene-butadiene block copolymers, can be stabilized with 0.05 to 2 parts per 100 parts of polymer of a compound of the formula II given below. It is mentioned that additional additives can also be used, i.a. also phenolic antioxidants such as n-octadecyl- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate or pentaerythrityl tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate ], and phosphorus-containing antioxidants, for example phosphites such as tris (2,4-di-t-butylphenyl) phosphite. Quantities for the other additives are not given. In the examples, either the compound of formula II or such other phenolic antioxidants is used, but never the compound of formula II and other additives together.

These stabilizer systems of the prior art have the disadvantage that quite large amounts of the phenolic acrylate of the formula 1 or 2 are required in order to achieve a stabilizing effect at all.

Another disadvantage is that the stabilization is insufficient - ie gel formation occurs which leads to specks in the molded part - if the copolymer is processed at high shear and / or at high temperature, for example above 200 ° C. Furthermore, the stabilizer systems mentioned are inadequate if molded parts for demanding applications, in particular thin foils or films, are produced from the copolymers. should be put.

Another disadvantage is that the stabilized polymers yellow. This yellow cast, which occurs when the polymer is processed or when the molded parts obtained are used, is particularly troublesome because the styrene-butadiene block copolymers, because of their high transparency, for optically demanding applications such as sight glasses, toys, boxes, office articles, medical or medical technology parts, food packaging , e.g. transparent packaging films and trays, drinking cups, drinks bottles, as well as transparent shrink films or "transparent" hangers can be used. In these applications, a yellow tinge is annoying.

A part of the added amount of the acrylate of the above formula 1 or 2 can be lost due to volatilization in the preparation of the stabilized polymer mixture, in particular when removing the solvent used in the polymerization, and / or during processing into molded parts. This loss is also disadvantageous since it has to be compensated for by increased addition amounts.

The task was to remedy the disadvantages described. In particular, the object was to provide styrene-diene copolymers which contain a more effective stabilizer system. The stabilizer system should be optimized with regard to the components and in particular their quantities for demanding applications of the molding compositions.

The stabilized block copolymers should also show reduced gel formation at processing temperatures of 200 to 280 ° C and high shear forces (e.g. extrusion). Aging should also be effectively prevented in the event of severe processing conditions. The gel content should be low and the molded parts or foils and films should have fewer gel specks.

The stabilized polymer should yellow less than the prior art polymers. In particular, the yellowing should be so low that optically demanding molded parts can be produced that are permanently colorless and transparent.

Finally, losses of the stabilizers added during the production or processing of the stabilized polymer should be avoided.

We have found that this object is achieved by the thermoplastic molding compositions defined at the outset. In addition, a process for the production of the molding compositions, the use of the molding compositions for the production of moldings, foils, films, fibers and foams, and the moldings, foils, films, fibers and foams from the molding compositions were found. Preferred embodiments of the invention can be found in the subclaims. EP-A 322 166 mentioned is silent on the amounts of the phenolic antioxidants and the organic phosphites, and in particular does not teach to use the components B to D present here precisely in the narrowly defined amount ranges according to the invention.

Component A

Component A is contained in the molding compositions in a proportion which is 100% by weight with the other components of the molding composition.

A is a block copolymer containing in polymerized form, based on A,

a1) 10 to 90, preferably 50 to 85 and in particular 60 to 85% by weight of at least one styrene monomer, and

a2) 10 to 90, preferably 15 to 50 and in particular 15 to 40% by weight of at least one diene monomer.

In addition to or in a mixture with styrene, vinylaromatic monomers which are substituted on the aromatic ring and / or on the C = C double bond with C _2-2 hydrocarbon radicals can also be used as styrene monomers. Styrene, α-methylstyrene, p-methylstyrene, ethylstyrene, tert-butylstyrene, vinyltoluene, 1,2-diphenylethylene, 1,1-diphenylethylene or mixtures thereof are preferably used. Styrene is particularly preferably used.

Examples of diene monomers are 1,3-butadiene, 2,3-dimethylbutadiene, 1,3-pentadiene, 1,3-hexadiene, isoprene and piperylene. 1,3-butadiene and isoprene are preferred, in particular 1,3-butadiene (hereinafter referred to as butadiene for short).

The monomers and other feedstocks, such as Solvent, in the purity typically required for the process, i.e. disruptive accompanying substances such as residual moisture, polar substances and oxygen are removed immediately prior to the polymerization in a manner known per se.

In addition to the styrene and diene monomers, other comonomers can also be used. The proportion of the comonomers is preferably 0 to 50, particularly preferably 0 to 30 and in particular 0 to 15% by weight, based on the total amount of the monomers used. Suitable comonomers are, for example, acrylates, in particular C _1-12 alkyl acrylates such as n-butyl acrylate or 2-ethylhexyl acrylate, and the corresponding methacrylates, in particular Cι_ι ₂ alkyl methacrylates such as methyl methacrylate (MMA). In addition, those in DE-A 19633626 on page 3, lines 5-50 are named under M1 to M10. ten monomers are suitable as comonomers. Reference is expressly made to this document.

Styrene is preferably used as the styrene monomer and butadiene, i.e. block copolymer A is preferably a styrene-butadiene block copolymer. As a rule, the block copolymers, known as such, are prepared by anionic polymerization in a manner known per se.

Usually initiators for anionic polymerization are mono-, bi- or multifunctional alkali metal alkyls, aryls or aralkyls. Organic lithium compounds are expediently used, such as ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, phenyl, diphenylhexyl, hexamethylenedi, butadienyl, isoprenyl, polystyryllithium or the multifunctional ones 1, 4-dilithiobutane, 1, 4-dilithio-2-butene or 1, 4-dilithiobenzene. The amount of alkali metal organyl required depends on the desired molecular weight, the type and amount of the other metal organyls used, and the polymerization temperature. As a rule, it is in the range from 1 ppm (w) (parts per million by weight) to 2% by weight, preferably 100 ppm (w) to 1% by weight, in particular 1000 to 5000 ppm (w), based on the total amount of monomers.

The polymerization can be carried out in the absence or in the presence of a solvent, that is to say as bulk polymerization or solution polymerization. The - preferred - solution polymerization is advantageously carried out in an aliphatic, isocyclic or aromatic hydrocarbon or hydrocarbon mixture, such as benzene, toluene, ethylbenzene, xylene, cumene, pentane, heptane, octane, cyclohexane or methylcyclohexane. Solvents with a boiling point above 70 ° C. are preferably used. Toluene or cyclohexane is particularly preferably used.

To control the reaction rate, additives reducing the polymerization rate, so-called retarders as described in WO 98/07766, can be added if necessary. However, retarders are not absolutely necessary. For example, metal organyls of an element of the periodic table are suitable as retarders. For example, the organyls of the elements Be, Mg, Ca, Sr, Ba, B, Al, Ga, In, Tl, Zn, Cd, Hg can be used. The magnesium and aluminum organyls are preferably used.

Organyls are understood to mean the organometallic compounds of the elements mentioned with at least one metal-carbon d bond, in particular the alkyl or aryl compounds. In addition, the metal organyls can also contain hydrogen, halogen or organic radicals bound via heteroatoms, such as alcoholates or phenolates, on the metal. The latter can be obtained, for example, by whole or partial hydrolysis, alcoholysis or aminolysis. Mixtures of different tallorganyle can be used.

Suitable magnesium organyls are those of the formula R ₂ Mg, where the radicals R independently of one another are hydrogen, halogen, C ₁ -C ₂ -alkyl or C ₆ -C ₂₀ aryl. Dialkyl magnesium compounds, in particular the ethyl, propyl, butyl, hexyl or octyl compounds available as commercial products, are preferably used. The hydrocarbon-soluble (n-butyl) (s-butyl) magnesium or (n-butyl) (n-octyl) magnesium is particularly preferably used.

Aluminum organyls which can be used are those of the formula R ₃ AI, where the radicals R independently of one another are hydrogen, halogen, CC ₂₀ alkyl or C ₆ -C ₂₀ aryl. Preferred aluminum organyls are the aluminum trialkyls such as triethylaluminium, tri-iso-butylaluminium (TIBA), tri-n-butylaluminium, tri-iso-propylaluminium, trin-hexylaluminium. Triisobutyl aluminum is particularly preferably used. Aluminum organyls which can also be used are those which are formed by partial or complete hydrolysis, alcoholysis, aminolysis or oxidation of alkyl or arylaluminum compounds. Examples are diethyl aluminum ethoxide, diisobutyl aluminum ethoxide, diisobutyl (2,6-di-tert-butyl-4-methylphenoxy) aluminum (CAS No. 56252-56-3), methylaluminoxane, isobutylated methylaluminoxane, Isobutylaluminoxane, tetraisobutyldialuminoxane or bis (diisobutyl) aluminum oxide.

Various magnesium compounds or aluminum compounds can also be used together. The anionic polymerization is particularly preferably carried out in the presence of a trialkylaluminum and / or dialkylmagnesium compound.

The molar ratios of the lithium compounds and the magnesium or aluminum compound can be varied in further ranges. They depend primarily on the desired molecular weight, the desired polymerization rate and the polymerization temperature, and the type and amount of the monomers. The molar ratio of magnesium or aluminum to alkali metal is expediently in the range from 0.2: 1 to 5: 1. If magnesium and aluminum compounds are used together, the polymerization is carried out at a molar ratio of the sum of magnesium and aluminum to lithium Range from 0.2: 1 to 5: 1 through.

After the end of the polymerization, the living polymer chains can be closed with a chain terminator. Suitable chain terminators are proton-active substances or Lewis acids such as water, alcohols, aliphatic and aromatic carboxylic acids and inorganic acids such as carbonic acid or boric acid. The styrene-butadiene block copolymers A can be, for example, linear two-block copolymers S-B or three-block copolymers SBS or BSB (S = styrene block, B = butadiene block), as can be obtained by anionic polymerization according to processes known per se. The block structure is essentially created by first anionically polymerizing styrene alone, creating a styrene block. After the styrene monomers have been consumed, the monomer is changed by adding monomeric butadiene and polymerizing anionically to form a butadiene block (so-called sequential polymerization). The two-block polymer SB obtained can be polymerized by renewed monomer change on styrene to a three-block polymer SBS, if desired. The same applies analogously to three-block copolymers BOD. Four-block and poly-block copolymers are also suitable as styrene-butadiene block copolymers.

In the case of the three-block copolymers, the two styrene blocks can be of the same size (same molecular weight, that is to say a symmetrical structure)

or of different sizes (different molecular weight, ie asymmetrical structure Sι.BS ₂ ). The same applies mutatis mutandis to the two butadiene blocks of the block copolymers BOD. Of course, block sequences SSB or S ^ Sa.B, or SBB or SB ^, are also possible. The indices for the block sizes (block lengths or molecular weights) are given above. The block sizes depend, for example, on the amounts of monomer used and the polymerization conditions.

Instead of the rubber-elastic "soft" butadiene blocks B or in addition to the blocks B, blocks B / S can also be used. The blocks B / S are also soft and contain butadiene and styrene, for example randomly distributed or as a tapered structure (tapered = gradient from styrene-rich to low styrene or vice versa). If the block copolymer contains several B / S blocks, the absolute amounts and the relative proportions of styrene and butadiene in the individual B / S blocks may be the same or different (resulting in different blocks (B / S) ^ (B / S) ₂ , etc.). The blocks B / S - regardless of whether their structure is statistical or tapered or different - are collectively referred to as "mixed" blocks.

The block copolymers mentioned can have a linear structure (described above). However, branched and in particular star-shaped structures are preferred. Branched block copolymers are obtained in a known manner, e.g. by grafting reactions from polymeric "side branches" onto a polymer main chain.

The preferred star-shaped block copolymers can be obtained, for example, by reacting the living anionic chain ends with an at least bifunctional coupling agent. Such coupling agents are described, for example, in US Pat. Nos. 3,985,830, 3,280,084, 3,637,554 and 4,091,053. Epoxidized glycerides (for example epoxidized linseed oil or soybean oil), silicon halides such as SiCl, or also divinyl benzene, and also polyfunctional aldehydes, ketones, esters, anhydrides or epoxides are preferred. Carbonates such as diethyl carbonate, propylene carbonate or ethylene carbonate (1,3-dioxolan-2-one) are also preferred. Dichlorodialkylsilanes, dialdehydes such as terephthalaldehyde and esters such as ethyl formate or ethyl acetate are also particularly suitable for dimerization.

By coupling the same or different polymer chains, symmetrical or asymmetrical star structures can be produced, i.e. the individual star branches can be the same or different, in particular contain different blocks S, B, B / S or different block sequences. Further details on star-shaped block copolymers can be found, for example, in WO-A 00/58380.

For example, styrene-butadiene block copolymers of the following embodiments 1) to 4) are used as component A:

1) an asymmetrically star-branched styrene-butadiene block copolymer of the general structure i

(Y-) mX - (- Z) _n (i)

- in the Y a block copolymer section of at least one polystyrene block with a molecular weight of 3000 to 230,000 and a polybutadiene block with a molecular weight of 2000 to 30,000 and

Z is a block copolymer section of at least one polystyrene block with a molecular weight of 2,000 to 60,000 and a polybutadiene block with a molecular weight of 2,000 to 30,000,

the total molar mass of Y is 50,000 to 250,000 and the total molar mass of Z is 5000 to 75,000,

- the block transitions are sharp or smeared,

- X represents the rest of a coupling agent and - the number of star branches m + n is a total of 3 to 15,

- with the proviso that m <_n.

2) a symmetrically or asymmetrically star-branched styrene-butadiene block copolymer with styrene blocks and mixed blocks B / S composed of butadiene and styrene. At least one star branch preferably has the block sequence Sj- (B / S) - and at least one further star branch has the block sequence S ₂ - (B / S) -, or at least one branch has the block sequence Sr (B / S) -S ₃ - and at least one branch the block sequence S ₂ - (B / S) -S ₃ -.

Further preferred embodiments 2) are block copolymers with structures which have at least one star branch with the block sequence S ₁ - (B / S) ₁ - (B / S) ₂ - and at least one star branch with the block sequence S ₂ - (B / S) ( B / S) ₂ -, or at least one star branch with the block sequence Sr (B / S) r (B / S) ₂ -S ₃ - and at least one star branch with the block sequence ge S ₂ - (B / S) r (B / S) ₂ -S ₃ -. In principle, each external (terminal) styrene block S can also be replaced by two or more consecutive styrene blocks SS ₂ , whereby block sequences S ₁ -S ₂ - (B / S) ₁ - (B / S) ₂ - or SS ₂ - ( BS) (B / S) ₂ -S3- arise.

Very particularly preferred embodiments 2) are block copolymers of the following structures ii and iii

SS ₂ - (B / S) - _(jj) S ₂ - (B / S) - / ^

and

SS ₂ - (B / S) -S ₃ - v _(iii) S ₂ - (B / S) ~ S ₃ - ^X

wherein X represents the rest of the coupling agent. A block sequence (B / S) _r (B / S) ₂ can also be used instead of the block B / S. Structures I and II mentioned in WO 00/58380 on page 8 in Examples 6 to 8 and structures Ib, Mb and III mentioned on page 12 in Examples 12 to 19 are likewise very particularly preferred.

3) a linear styrene-butadiene block copolymer with at least two styrene blocks and at least one polybutadiene block, the molar mass data given above for embodiment 1) applying to the polystyrene or polybutadiene blocks.

4) a linear styrene-butadiene block copolymer with at least two styrene blocks S and at least one mixed block B / S of butadiene and styrene. The two styrene blocks are preferably external (terminal), the styrene block lengths can be the same, structure S ₁ - (B / S) -S ₁ , or different, structure S (B / S) -S ₂ . Instead of a mixed block B / S, n mixed blocks (B / S) ι _{to n} can be placed between the styrene blocks. For example, with three mixed blocks there is a structure S ₁ - (B / S) ₁ - (B / S) ₂ - (B / S) ₃ -S ₁ or S ₁ - (B / S) ₁ - (B / S ) ₂ - (B / S) ₃ -S ₂ before.

A possible embodiment 4) is a block copolymer of the structure Sr (B / S) -S ₁ , with particular preference the two styrene blocks S ^ each about 16% by weight of the block copolymer and the mixed B / S block about 68% by weight .-% of the block copolymer. The butadiene content of this block copolymer is very particularly preferably about 35% by weight. This polymer has the property profile of thermoplastic elastomers (TPE). Further details of the embodiments described under 2) and 4) can be found in WO 00/58380, in particular pages 3 to 4.

The block copolymer particularly preferably has a star-shaped structure, for example in accordance with the above embodiments 1) and 2).

The monomer names styrene and butadiene used above are also examples of other vinyl aromatics and dienes.

The molding compositions according to the invention can contain the block copolymers A as the only polymer. However, they can additionally contain further polymers A ', for example in amounts of 0 to 90, preferably 0 to 70 and particularly preferably 0 to 30% by weight, based on the molding composition. For example, polymers based on vinyl aromatic monomers are suitable. The polymers A 'can contain comonomers, for example the comonomers already mentioned above.

Suitable further polymers A 'are, in particular, homopolymers and copolymers of styrene, for example homopolystyrene (GPPS, general purpose polystyrene), styrene-acrylonitrile copolymer (SAN), impact-resistant, that is to say rubber-containing polystyrene (HIPS, high impact polystyrene), acrylonitrile-butadiene Styrene copolymer (ABS) or acrylonitrile-styrene-acrylic ester copolymer (ASA). Homopolystyrene or HIPS is preferably used as A ', particularly preferably homopolystyrene in amounts of 0 to 70% by weight, based on the molding composition. 0 to 50 and, for their use in foils and films, 30 to 70% by weight, based on the molding composition, of further polymer A 'are particularly preferably used for the molding composition according to the invention.

The thermoplastic molding compositions according to the invention are generally transparent, or at least opaque (translucent). Usually, with a styrene monomer content of at least 50% by weight in component A, they have rather tough and stiff properties, and otherwise tend to be elastomeric or soft properties.

Component B

Component B is present in the molding compositions in a proportion of 0.001 to 0.5, preferably 0.01 to 0.4, in particular 0.02 to 0.3% by weight. The proportion of B is very particularly preferably 0.03 to 0.2, in particular 0.04 to 0.19,% by weight, based on the molding composition.

Component B is a phenolic acrylate of the formula I

In the formula, R ² and R ³ independently of one another denote hydrogen or an alkyl radical, aryl radical, alkylaryl radical or cycloalkyl radical, where these radicals can each contain 1 to 20 carbon atoms; Z means tert-pentyl, that is, -C (CH ₃ ) ₂ CH ₂ CH ₃ .

The phenolic acrylates B are prepared in a manner known per se by reacting corresponding phenol compounds with acrylic acid or their derivatives and is described, for example, in EP-A 322 166.

R ¹ is preferably R ² is R ³ is hydrogen, resulting in the acrylate radical - O (CO) CH = CH ₂ , or R ¹ is methyl and R ² is R ³ is hydrogen, which results in the methacrylate -Rest -O (CO) C (CH ₃ ) = CH ₂ results.

The acrylate residue, i.e. In a particularly preferred embodiment, the phenolic acrylate is a compound of the formula II

in which Z means tert-pentyl, and which is commercially available, for example, as Sumilizer® GS from Sumitomo Chemical.

Component C

Component C is present in the molding compositions in a proportion of 0.05 to 1, preferably 0.1 to 0.8, in particular 0.15 to 0.5% by weight. The proportion of C is very particularly preferably 0.19 to 0.37% by weight, based on the molding composition. Component C is an organic phosphite. For example, organic phosphites of the formulas are suitable

wherein R ^{1 is} hydrogen or an organic radical, and R ² to R ^{6 are the} same or different organic radicals. Phosphites are also to be understood as phosphites.

Particularly suitable phosphites and phosphonites are, for example

triphenylphosphite,

diphenyl,

phenyldialkylphosphites,

Tris (nonylphenyl) phosphite (TNPP), trilauryl phosphite,

Trioctadecylphosphit.Distearylpentaerythritdiphosphit,

Tris (2,4-di-tert-butylphenyl) phosphite,

diisodecyl pentaerythritol diphosphite,

Bis (2,4-di-tert-butylphenyl) pentaerythritol diphosphite, bis (2,6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphite,

diisodecyloxypentaerythritol diphosphite,

Bis (2,4-di-tert-butyl-6-methylphenyl) pentaerythritol diphosphite,

Bis (2,4,6-tris (tert-butylphenyl) pentaerythritol diphosphite,

Tristearyl sorbitol triphosphite, tetrakis (2,4-di-tert-butylphenyl) -4,4'-biphenylene diphosphonite,

6-lsooctyloxy-2,4,8,10-tetra-tert-butyl-l2-H-dibenz [d, g] -1,3,2-dioxaphosphocin,

Bis (2,4-di-tert-butyl-6-methylphenyl) methyl phosphite,

Bis (2,4-di-tert-butyl-6-methylphenyl) ethyl phosphite,

6-fluoro-2,4,8,10-tetra-tert-butyl-12-methyldibenz [d, g] -1,3,2-dioxaphosphocin, 2,2 ', 2 "-nitrilo [triethyltris (3.3 ', 5,5 ^, -tetra-tert-butyl-1, 1'-biphenyl-2,2'-diyl) phosphite],

2-ethylhexyl (3,3 \ 5,5'-tetra-tert-butyl-1, 1'-biphenyl-2,2'-diyl) phosphite and

5-butyl-5-ethyl-2- (2,4,6-tri-tert-butylphenoxy) -1,3,2-dioxaphosphirane.

The phosphites C are known and commercially available. They are manufactured in a manner known per se. Triaryl phosphites such as triphenyl phosphite, tris (2,4-di-tert-butylphenyl) phosphite and tris (nonphenyl) phosphite (TNPP) are particularly preferably used. The organic phosphite C is very particularly preferably selected from TNPP, commercially available, for example, as Irgafos® TNPP from Ciba Specialty Chemicals, and tris (2,4-di-tert-butylphenyl) phosphite, commercially available, for example as Irgafos® 168 from Ciba Specialty Chemicals.

Component D

Component D is present in the molding compositions in a proportion of 0.001 to 1, preferably 0.01 to 0.7, in particular 0.05 to 0.5% by weight. The proportion of D is very particularly preferably from 0.08 to 0.4, in particular 0.09 to 0.3,% by weight, based on the molding composition.

Component D is a stabilizer compound D selected from sterically hindered phenols, which differ from phenolic acrylate B, and aromatic amines. The stabilizer compound D is therefore a primary antioxidant, which presumably acts as a scavenger of oxygen radicals.

The sterically hindered phenols D differ from the phenolic acrylate B. As a rule, they contain no acrylate groups. Particularly suitable sterically hindered phenols are, for example, the following connecting groups Nos. 1 to 12:

1. Alkylated monophenols, for example 2,6-di-tert-butyl-4-methylphenol, 2-tert-butyl-4,6-dimethylphenol, 2,6-di-tert-butyl-4-ethylphenol, 2,6-di tert-butyl-4-n-butylphenol, 2,6-di-tert-butyl-4-isobutylphenol, 2,6-dicyclopentyl-4-methylphenol, 2- (a-methylcyclohexyl) -4,6-dimethylphenol , 2,6-dioctadecyl-4-methylphenol, 2,4,6-tricyclohexylphenol, 2,6-di-tert-butyl-4-methoxymethylphenol, nonylphenols which are linear or branched in the side chains, for example, 2,6 -Dinonyl-4-methylphenol, 2,4-dimethyl-6- (1 '- methylundec-1'-yl) phenol, 2,4-dimethyl-6- (1'-methylheptadec-1'-yl) phenol, 2 , 4-dimethyl-6- (1'-methyltridec-1'-yl) phenol and mixtures thereof.

2. Alkylthiomethylphenols, for example 2,4-dioctylthiomethyl-6-tert-butylphenol, 2,4-dioctylthiomethyl-δmethylphenol, 2,4-dioctylthiomethyl-6-ethylphenol, 2,6-didodecylthiomethyl-4-nonylphenol.

3. Hydroquinones and alkylated hydroquinones, for example 2,6-di-tert-butyl-4-methoxyphenol, 2,5-di-tert-butylhydroquinone, 2,5-di-tert-amylhydroquinone, 2,6-diphenyl-4 octadecyloxyphenol, 2,6-di-tert-butylhydroquinone, 2,5-di-tert-butyl-4- hydroxyanisole, 3,5-di-tert-butyl-4-hydroxyanisole, 3,5-di-tert-butyl-4-hydroxyphenyl stearate, bis (3,5-di-tert-butyl-4-hydroxyphenyl) adipate ,

4. Hydroxylated thiodiphenyl ethers, for example 2,2'-thiobis (6-tert-butyl-4-methylphenol), 2,2'-thiobis (4-octylphenol), 4,4'-thiobis (6-tert- butyl-3-methylphenol), 4,4'-

Thiobis (6-tert-butyl-2-methylphenol), 4,4'-thiobis (3,6-di-secamylphenol), 4,4'-bis (2,6-dimethyl-4-hydroxyphenyl) disulfide.

5. Alkylidenebisphenols, for example 2,2'-methylenebis (6-tert-butyl-4-methylphenol), 2,2'-methylenebis (6-tert-butyl-4-ethylphenol), 2,2-methylenebis [4- methyl-6- (a-methyl-cyclohexyl) phenol], 2,2'-methylenebis (4-methyl-6-cyclohexylphenol), 2,2'-methylenebis (6-nonyl-4-methylphenol), 2,2 ' -Methylene bis (4,6-di-tert-butylphenol), 2,2'-ethylidenebis (4,6-di-tert-butylphenol), 2,2'-ethylidenebis (6-tert-butyl-4-isobutylphenol), 2,2'-methylenebis [a-methylbenzyl) -4-nonylphenol], 2,2'-methylenebis [6- (a, a-dimethylbenzyl) -4-nonylphenol], 4,4'-methylenebis (2,6-di -tert-butylphenol), 4,4'-methylenebis (6-tert-butyl-2-methylphenol), 1,1-bis (5-tert-butyl-4-hydroxy-2-methylphenyl) butane, 2,6- Bis (3-tert-butyl-5-methyl-2-hydroxybenzyl) -4-methylphenoI, 1, 1, 3-tris (5-tert-butyl-4-hydroxy-2-methylphenyl) butane, 1, 1- Bis (5-tert-butyl-4-hydroxy-2-methylphenyl) -3-n-dodecyl mercaptobutane, ethylene glycol bis [3,3-bis (3'-tertbutyl-4'-hydroxyphenyl) butyrate], bis (3- tert-butyl-4-hydroxy-5-methylphenyhdicyclopentadiene, bis [2- ( 3'-tert-butyl-2'-hydroxy-5'-methylbenzyl) 6-tert-butyl-4-methylphenyl] terephthalate, 1, 1-bis- (3,5-dimethyl-2-hydroxyphenyl) butane, 2, 2- bis (3,5-di-tert-butyl-4-hydroxyphenyl) propane, 2,2-bis (5-tert-butyl-4-hydroxy-2-methylphenyl) -4-n-dodecyl mercaptobutane , 1, 1, 5,5-tetra- (5-tert-butyl-4-hydroxy-2-methylphenyl) pentane.

6. Hydroxybenzylated malonates, for example dioctadecyl 2,2-bis - (3,5-di-tert-butyl-2-hydroxybenzyl) malonate, dioctadecyl-2- (3-tert-butyl-4-hydroxy-5-methylbenzyl ) - malonate, didodecylmercaptoethyl-2,2-bis (3,5-di-tert-butyl-4-hydroxybenzyl) malonate, bis (4- (1,1,3,3-tetramethylbutyl) phenyl] -2,2 -bis (3,5-di-tert-butyl-4-hydroxybenzyl) malonate.

7. Aromatic hydroxybenzyl compounds, for example 1,3,5-tris (3 _{l of} 5-di-tert-butyl-4-hydroxybenzyl) -2,4,6-trimethylbenzene, 1,4-bis (3,5-di tert-butyl-4-hydroxybenzyl) - 2,3,5,6-tetramethylbenzene, 2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) phenol.

8. Esters of β- (3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid with mono- or polyhydric alcohols, for example with methanol, ethanol, n-octanol, i-octanoI, octadecanol, 1, 6 -Hexanediol, 1, 9-nonanediol, ethylene glycol, 1,2-propanediol, neopentyl glycol, thio-diethylene glycol, diethylene glycol, triethylene glycol, pentaerythritol, tris (hydroxyethyl) isocyanurate, N, N'-bis (hydroxyethyl) oxamide, 3- Thiaundecanol, 3-thiapentadecanol, trimethylhexanediol, trimethylolpropane, 4-hydroxymethyl-l-phospha-2,6,7-trioxabicyclo [2.2.2] octane. 9. esters of β- (5-tert-butyl-4-hydroxy-3-methylphenyl) propionic acid with mono- or polyhydric alcohols, for example with methanol, ethanol, n-octanol, i-octanol, octa-decanol, 1, 6 -Hexanediol, 1,9-nonanediol, ethylene glycol, 1,2-propanediol, neopentyl glycol, thiodiethylene glycol, diethylene glycol, triethylene glycol, pentaerythritol, tris (hydroxyethyl) isocyanurate, N, N'-bis (hydroxyethyl) oxamide, 3-thiaundecanol, 3 -Thiapentadecanol, trimethylhexanediol, trimethylolpropane, 4-hydroxymethyl-l-phospha-2,6,7-trioxabicyclo- [2.2.2] octane.

10. esters of β- (3,5-dicyclohexyl-4-hydroxyphenyl) propionic acid with mono- or polyhydric alcohols, for example with methanol, ethanol, octanol, octadecanol, 1,6-hexanediol, 1,9-nonanediol, ethylene glycol, 1 , 2-propanediol, neopentyl glycol, miodiethylene glycol, diethylene glycol, triethylene glycol, pentaerythritol, tris (hydroxyethyl) isocyanurate, N, N'-bis (hydroxyethyl) oxamide, 3-thiaundecanol, 3-thiapentadecanol, trimethylhexanediol, trimethylolpropane, trimethylolpropane hydroxymethyl-1-phospha-2,6,7-trioxabicyclo [2.2.2] octane.

11. esters of 3,5-di-tert-butyl-4-hydroxyphenylacetic acid with mono- or polyhydric alcohols, for example with methanol, ethanol, octanol, octadecanol, 1,6-hexanediol, 1,9-nonanediol, ethylene glycol, 1, 2-propanediol, neopentyl glycol, thiodiethylene glycol, diethylene glycol, triethylene glycol, pentaerythritol, tris (hydroxyethyl) isocyanurate, N, N'-bis (hydroxyethyl) oxamide, 3-thiaundecanol, 3-thiapentadecanol, trimethylhexanediol, trimethylymethyl propane, 4-hydroxa methyl propane -2,6,7-trioxabicyclo [2.2.2] octane.

12. Amides of b- (3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid, for example N, N'-bis (3,5-di-tert-butyl-4-hydroxyphenylpropionyl) hexamethylenediamide, N, N '-Bis (3,5-di-tert-butyl-4-hydroxyphenylpropionyl) trimethylenediamide, N, N'-bis (3,5-di-tert-butyl-4-hydroxyphenylpropionyl) hydrazide, N, N'-bis [ 2- (3- [3,5-di-tert-butyl-4-hydroxyphenyl] propionyloxy) ethyl] oxamide.

Particularly suitable, in particular secondary, aromatic amines are, for example, N, N'-di-isopropyl-p-phenylenediamine, N, N'-di-sec-butyl-p-phenylenediamine, N, N'-bis (1,4-dimethylpentyl ) -p-phenylenediamine, N, N'-bis (1-ethyl-3-methylpenty1) -p-phenylenediamine, N, N'-bis (1-methylheptyl) -p-phenylenediamine, N, N'-dicyclohexyl-p -phenylene diamine, N, N'-diphenyl-p-phenylene diamine, N, N'-bis (2-naphthyl) -p-phenylene diamine, N-isopropyl-N-phenyl-p-phenylene diamine, N- (1,3-dimethylbutyl ) -N-phenyl-p-phenylenediamine, N- (1-

Methylheptyl) -N'-phenyl-p-phenylene diamine, N-cyclohexyl-N'-phenyl-p-phenylene diamine, 4- (p-toluenesulfamoyl) diphenyamine, N, N'-dimethyl-N, N'-di-sec- butyl-p-phenylenediamine, diphenylamine, N-allyldiphenyiamine, 4-isopropoxydiphenylamine, N-phenyl-1-naphthylamine, N- (4-tert-octylphenyl) -1-naphthylamine, N-phenyl-2-naphthylamine, octylated diphenylamine , for example p, p'-di-tert-octyldiphenylamine, 4-n-butylaminophenol, 4-butyrylaminophenol, 4-nonanoylaminophenol, 4-dodecanoylaminophenol, 4-octadecanoylaminophenol, bis (4-methoxyphenyl) amine, 2,6-di- tert-butyt-4 dimethylaminomethylphenol, 2,4'-diaminodiphenyImethane 4,4'-diaminodiphenylmethane, N, N, N ', N-tetramethyl-4,4'-diaminodiphenylmethane, 1,2-bis [(2-methylphenyl) amino] ethane, 1,2-bis (phenylamino) propane, (o-tolyl) biguanide, bis [4- (1 ', 3'-dimethylbutyl) phenylamine, tert-octylated N-phenyl-1-naphthylamine, a mixture of mono - And dialkylated tert-butyl-tert-octyldiphenylamines, a mixture of mono- and dialkylated nonyldiphenylamines, a mixture of mono- and dialkylated dodecyldiphenylamines, a mixture of mono- and dialkylated isopropyl / isohexyldiphenylamines, a mixture of mono- and dialkylamines tert-butyldiphenylamines, 2,3-dihydro-3,3-di-methyl-4-H-1, 4-benzothiazine, phenothiazine, a mixture of mono- and dialkylated tert-butyl-tert-octylphenothiazines, a mixture of mono and dialkylated tert

Octylphenothiazines, N-allylphenothiazine, N, N, N, N'-tetraphenyl-1, 4-diaminobut-2-ene, N, N-bis (2,2,6,6-tetramethylpiperid-4-yI) hexamethylenediamine, Bis (2,2,6,6-tetra-methyl piperid-4-yl) sebacate, 2,2,6,6-tetramethylpiperidin-4-one, 2,2,6,6-tetramethylpiperidin-4-ol.

Benzylamines such as tris (3,5-di-tert-butyl-4-hydroxybenzyl) amine, and acylaminophenols such as 4-hydroxylauranilide, 4-hydroxystearanilide or octyl-N- (3,5-di-tert-butyl-4-hydroxy- phenyl) carbamate, are also particularly suitable.

The particularly suitable stabilizer compounds D also include sterically hindered phenols and aromatic amines which contain triazine as a structural element. Such triazine compounds are e.g. 2,4-bis (octylmercapto) -6- (3,5-di-tert-butyl-4-hydro-xyanilino) -1,3,5-triazine, 2-octylmercapto-4,6-bis (3,5 -di-tert-butyl-4-hydroxy-anilino) -1, 3,5-triazine, 2-octylmercapto-4,6-bis (3,5-di-tert-butyl-4-hydroxyphenoxy) - 1,3 , 5-triazine, 2,4,6-tris- (3,5-di-tert-butyl-4-hydroxyphenoxy) -1,2, 3-triazine, 1,3,5-tris- (3,5- di-tert-butyl-4-hydroxybenzyl) isocyanurate, 1,3,5-tris (4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanurate, 2,4,6-tris (3,5 -di-tert-butyl-4-hydroxyphenylethyl) -1,3,5-triazine, 1,3,5-tris (3,5-di-tert-butyl-4-hydroxyphenylpropionyl) hexahydro-1,3,5- triazine and 1,3,5-tris (3,5-dicyclohexyl-4-hydroxybenzyl) isocyanurate.

The stabilizer compounds D are known and commercially available or can be prepared in a manner known per se.

The stabilizer compounds D used are particularly preferably sterically hindered phenols, in particular esters of β- (3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid, see above under No. 8.

The stabilizer compound D is very particularly preferably a sterically hindered phenol of the formula III

or of formula IV

or their mixture. In particular, compound III is used as component D alone.

Compound III is pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] and compound IV is n-octadecyl- [3- (3,5-di-tert-butyl-4 hydroxyphenyl) propionate. Compound III is e.g. as Irganox® 1010, and compound IV is e.g. commercially available as Irganox® 1076, both from Ciba Specialty Chemicals.

It goes without saying that, instead of a single phenolic acrylate B, it is also possible to use a plurality of phenolic acrylates Bi, B ₂ , etc. In the latter case, the proportions for B apply to the sum of all n components Bi to B _n . This applies mutatis mutandis to component C, organic phosphites, and component D, stabilizer compound selected from sterically hindered phenols and aromatic amines.

The quantitative ratio of stabilizer compound D to phenolic acrylate B in the molding compositions according to the invention is preferably 0.5: 1 to 50: 1, in particular 1: 1 to 10: 1, and particularly preferably 2: 1 to 5: 1.

It is believed that phenolic acrylate B acts as a scavenger of carbon radicals, which occur particularly when the polymer is subjected to a combination of thermal stress and shear. The organic phosphite C presumably acts as a scavenger of oxygen O, which causes aging. Stabilizer compound D apparently acts as a scavenger of oxygen radicals, which are also involved in polymer aging. Optional additional components

The molding compositions according to the invention can contain further components in addition to components A to D. These are, in particular, customary additives and processing aids, different from the aforementioned components A to D, such as e.g. Lubricants or mold release agents, colorants such as e.g. Pigments or dyes, flame retardants, antioxidants, light stabilizers, fibrous and powdery fillers or reinforcing agents or antistatic agents, as well as other additives or their mixtures.

Suitable lubricants and mold release agents are e.g. Stearic acids, stearyl alcohol, stearic acid esters or amides, metal stearates, montan waxes and those based on polyethylene and polypropylene.

Pigments are, for example, titanium dioxide, phthalocyanines, ultramarine blue, iron oxides or carbon black, and the class of organic pigments. Dyes are to be understood as all dyes that can be used for the transparent, semi-transparent or non-transparent coloring of polymers. Dyes of this type are known to the person skilled in the art.

As flame retardants e.g. the halogen-containing or phosphorus-containing compounds known to the person skilled in the art, magnesium hydroxide and other customary compounds, or mixtures thereof, are used.

Compounds which are different from the aforementioned components B to D are suitable as further antioxidants.

Suitable light stabilizers are e.g. various substituted resorcinols, salicylates, benzotriazoles, benzophenones, HALS (hindered amine light stabilizers), such as those e.g. are commercially available as Tinuvin® from Ciba Specialty Chemicals.

Examples of fibrous or pulverulent fillers are carbon or glass fibers in the form of glass fabrics, glass mats or glass silk rovings, cut glass, glass balls and woolastonite, particularly preferably glass fibers. If glass fibers are used, they can be equipped with a size and an adhesion promoter for better compatibility with the blend components. Glass fibers can be incorporated both in the form of short glass fibers and in the form of continuous strands (rovings). Suitable particulate fillers are carbon black, amorphous silica, magnesium carbonate (chalk), powdered quartz, mica, mica, bentonite, talc, feldspar or, in particular, calcium silicates such as woolastonite and kaolin.

Suitable antistatic agents are, for example, amine derivatives such as N, N-bis (hydroxyalkyl) alkylamines or alkylene amines, polyethylene glycol esters or glycerol mono- and distearates, and mixtures thereof.

The individual additives are used in the usual amounts, so that further details are not necessary.

Production of molding compounds

The molding compositions according to the invention can be produced by mixing processes known per se, for example by melting in an extruder, Banbury mixer, kneader, roller mill or calender at temperatures of 180 to 280 ° C. However, the components can also be mixed "cold" without melting, and the powdery or granular mixture is only melted and homogenized during processing. Likewise, one can pre-mix individual components, or mix some or all components in solution and then remove the solvent again, e.g. in degassing extruders.

Components B, C and D can be added to block copolymer A in any known manner, e.g. in pure form or as a solution directly in the working up of the reaction mixture which is obtained in the production of the block copolymer, or in the processing of the block copolymer to give moldings, films, etc. However, one or more of components B to D can also be used with the polymer premix, either as a solid or in solution, the solution being freed from the solvent in the customary manner, for example by degassing. Components B to D can also be metered in as a masterbatch (concentrate of polymer and large amounts of B, C and / or D).

As a rule, the molding compositions according to the invention are prepared in such a way that they are not basic. The molding compositions are preferably neutral to slightly acidic. This is described by means of suitable measures in the production of the molding compositions described below.

Neutral to weakly acidic means that the molding compositions have a pH of from 3 to 7, particularly preferably from about 5 to 6. Production comprises the entire process from the monomers to the finished molding composition, for example the polymerization of the monomers to the block copolymer A, the addition of components B to D, the addition and removal of polymerization auxiliaries, and mixing and conditioning to the finished molding compound. Accordingly, the production in particular also includes the processing of the block copolymer to give the molding composition and the conditioning of the molding composition to give the end product.

It is believed that the effect of the stabilizers (components B to D) is improved under neutral to weakly acidic conditions, and that the block copolymer shows less yellowing, since no strongly colored phenolates are formed.

As a rule, the molding composition is neutral to weakly acidic by adjusting the block copolymer A, which is usually worked up onto the molding composition, to an appropriate pH. For this purpose, preference is given to adding CO ₂ and water during the production of the molding composition (including working up to the molding composition). The invention accordingly also relates to a method for producing the molding compositions, the inventive method being used during production

Molding composition is neutral to weakly acidic by adding CO ₂ and water.

In a preferred embodiment, CO ₂ and water are added after the polymerization of the block copolymer A: the block copolymer A is prepared from the styrene and diene monomers in a polymerization reactor in a solvent such as cyclohexane, and for example the CO ₂ and water of the meter in substantially fully reacted reaction mixture which is either present in the reactor or which is removed from the reactor (ie after the polymerization). One or more of components B, C and D can also be added together with CO ₂ / water, if desired.

In a particularly preferred embodiment, CO ₂ and / or water is metered in again at a later stage in the production of the molding composition, in particular in a later stage in the workup. For example, when removing the solvent that was used in the polymerization of the block copolymer, or when mixing components A to D, CO ₂ and / or water can be added again. A renewed metering can be particularly advantageous if the working up completely or partially loses the CO ₂ and / or the water.

It has proven to be advantageous to design the molding compositions according to the invention by adding CO ₂ and water in a manner known per se such that no basic conditions prevail during the entire workup, but rather neutral to weakly acidic conditions. For example, before removing the solvent used in the polymerization, it is advantageous to set a CO ₂ pressure which is higher than the vapor pressure of the removing solvent, so that sufficient CO _{2 is present} in the reaction mixture even when the solvent is separated, in order to keep the mixture in the neutral to weakly acidic range.

As a rule, CO ₂ and water are added together. However, a separate addition is also possible. Likewise, water or CO _{2 can} be metered in alone when adding again, depending on whether water or CO _{2 is lost} in the workup.

In another, likewise preferred embodiment, the addition of CO ₂ and water is carried out as conditioning the molding composition initially obtained in the working up, ie as an aftertreatment of the molding composition. This post-treatment creates the final product, the finished molding compound. For this purpose, the molding compound - usually after solidification or cooling - is annealed in the presence of water and CO ₂ . Annealing should be understood to mean storage for a certain time at a defined temperature, which is usually above room temperature. It has been found that annealing at 20 to 60 ° C., in particular 30 to 50 ° C., preferably approximately 40 ° C., and 10 to 200, in particular 40 to 100, preferably 60 to 80 hours is advantageous.

When conditioning (tempering), the molding composition is preferably present in divided form, for example in the form of granules, powder or chips. Annealing can be carried out in a simple manner by placing the molding compound and water in a closed stirred vessel, heating the reactor to the annealing temperature and metering in CO ₂ . The polymer-water mixture is expediently stirred. To increase the CO ₂ content of the water, you can anneal under CO ₂ overpressure.

Annealing can be carried out in a particularly simple manner by storing the, for example, granular molding composition in an oven or drying cabinet at the tempering temperature in the presence of water (steam) and CO ₂ . It is advisable to add CO ₂ as solid CO ₂ (dry ice) and water into the drying cabinet using a water-filled open container (bowl, beaker) or a water-soaked fabric (wet cloth), so that water vapor is generated.

One can also combine the above two embodiments of adding CO ₂ and water, that is, both the reaction mixture CO ₂ and water zufü- gene and the granulated molding compound with CO ₂ and water post-treated (be conditioned).

Instead of CO ₂ and water, other - preferably aqueous - acids or buffer systems can also be used, in particular weak organic or inorganic acids or their salts. The pH of the acidified water is preferably 3 to 7, in particular 5 to 6, regardless of the acidifying agent.

Molding compositions which have been produced as described above with the addition of CO ₂ and water generally have a lighter intrinsic color, in particular a reduced yellow tinge. The molding compound granules or powder and the moldings, foils, films, fibers and foams produced therefrom are colorless and not yellowish due to the tempering.

The thermoplastic molding compositions according to the invention can be processed by the known methods of thermoplastic processing, for example by extrusion, injection molding, calendering, blow molding or sintering.

The molding compositions according to the invention can be used for the production of moldings, foils, films, fibers and foams. This use is also the subject of the invention. Films are understood to mean both (thin) foils and surface coatings.

The films and films according to the invention are particularly suitable, inter alia. also because of their good printability, for packaging purposes, e.g. for food packaging. They are also suitable as shrink films. Such shrink films are e.g. used for the packaging of small parts, or pre-printed as labeling and sealing of containers (beverage bottles, cans, jars, etc.). The films and films according to the invention are also suitable as thermoformed films and as stretching and cling films. In particular, the self-adhesive cling foils are used as cling films for food.

The moldings, foils, films, fibers and foams mentioned are likewise the subject of the invention.

The molding compositions according to the invention have economic advantages over the molding compositions of the prior art due to the low stabilizer contents. Despite the lower amounts of stabilizers, they are reliably protected against aging and against degradation reactions during processing. This is especially true at high temperatures and high shear forces.

The gel content of the molding compounds is low. It should be emphasized that the molding compositions have a significantly lower gel formation even at processing temperatures of 200 to 280 ° C and high shear (for example by extrusion). The molded parts available from the molding compounds have significantly fewer gel specks. In particular, the stabilizer mixture (components B to D) is effective even with the small amounts of component B according to the invention. In addition, there is hardly any loss of stabilizer due to volatilization.

The lower amounts of stabilizers also result in lower global migration. Global migration is the sum of all migrable components and should e.g. be as low as possible for food packaging.

This makes the block copolymers according to the invention particularly suitable for food applications, e.g. as a food packaging film or tray, drinking cups, drinks bottles, cutlery, plates, cling film, etc.

Examples

The feedstocks were cleaned and dried using aluminum oxide pores, if necessary. It means:

s-BuLi: 12% by weight solution of sec-butyllithium in cyclohexane, ready-to-use solution from Chemetall,

Polystyrene: rubber-free polystyrene, produced by radical polymerization, with a number average molecular weight M _n of 96,000 and a weight average molecular weight M _w of 272,000, determined using gel permeation chromatography and polystyrene calibration standards (PS standard kit from Polymer Laboratories). The commercial product Polystyrol® 158K from BASF was used.

Edenol: an epoxidized linseed oil as a coupling agent; the commercial product Edenol® B 316 from Henkel was used.

Acrawax: a commercially available fatty acid amide; the commercial product Acra-wax® from Lonza was used.

White oil: the mineral oil Winog® 70 from Wintershall was used.

The following stabilizers were used:

B: Phenolic acrylate of the formula II already mentioned. The commercial product Sumilizer® GS from Sumitomo Chemical was used.

C1: Tris (nonylphenyl) phosphite, TNPP. A common commercial product was used. C2: Tris (2,4-di-tert-butylphenyl) phosphite. A common commercial product was used.

D1: Sterically hindered phenol of the formula III already mentioned. The commercial product Irganox® 1010 from Ciba Specialty Chemicals was used.

D2: Sterically hindered phenol of the formula IV already mentioned. The commercial product Irganox® 1076 from Ciba Specialty Chemicals was used.

1. Production of the molding compositions containing a star-shaped styrene-butadiene block copolymer and polystyrene

a) Star-shaped styrene-butadiene block copolymers of the structure ii

were obtained by sequential anionic polymerization of styrene and butadiene in cyclohexane as solvent and subsequent coupling. For this purpose, 654 kg of cyclohexane and 78 kg of styrene (initially charged for block S, heated to 40 ° C., and titrated with s-BuLi solution to remove impurities were stirred in a 15001 stirred reactor flushed with nitrogen Blocks S _T initiated the polymerization by adding 600 g of s-BuLi solution and, after reaching the maximum temperature, the reaction mixture was cooled to 60 ° C. Then, for the production of block S _2, 2100 g of s-BuLi solution were initiated and 47 kg of styrene were added and, after the maximum temperature had been reached, the temperature was raised to 50 ° C. 52 kg of butadiene and 26 kg of styrene were then added simultaneously as separate feeds to produce block B / S. After the maximum temperature had been reached, the mixture was left to react for 10 minutes 540 ml of Edenol were added to couple the block copolymers obtained, the temperature was raised to 55 ° C. and the mixture was left to react for 10 minutes.

b) 1000 ml of water were then added to the polymer solution obtained with rapid stirring, after 5 min again 1000 ml of water and after another 5 min again by 1000 ml of water. CO ₂ gas was then bubbled into the solution for 20 minutes, making it weakly acidic.

c) A mixture of 1700 g of stabilizer C1 and 1000 ml of cyclohexane was then added to this acidified polymer solution, as was a solution of 470 g Acrawax in 3000 ml cyclohexane, and finally 4300 g white oil. The mixture was stirred for 10 minutes.

d) The polymer solution obtained was finally added in portions (one portion for each example) on a ZSK 40 twin-screw degassing extruder from Werner + Pfleiderer,

Stuttgart, freed from the solvent cyclohexane and at the same time mixed with the other stabilizers B and D. The following were fed into the extruder at 200 ° C.:

100 kg / h of the polymer solution (corresponds to 29 kg / h block copolymer), the stabilizers B and D in amounts such that the block copolymer contained the proportions of B and D given in the table, and 3.92 kg / h polystyrene.

The amounts of stabilizer given in Table 1 relate to the stabilized block copolymer, ie the sum of components A to D, before the polystyrene is added. The molding compound was extruded and granulated after cooling. The product obtained contained about 12% by weight of polystyrene.

e) Each of the granules obtained was then conditioned (post-treated) with CO ₂ and water. For this purpose, 100 g of granules were closed at 40 ° C.

Drying cabinet containing CO ₂ dry ice and a water-soaked cloth was stored for 72 hours. A colorless, transparent granulate was obtained.

2. Testing the molding compositions for aging resistance

In order to determine the stability of the stabilized block copolymers according to the invention against aging, the granules obtained were examined by means of rheography. The Rheograph 2000 from Göttfert, Buchen, was used. The measuring principle is as follows:

In rheography, similar to the measurement of the melt volume rate MVR or the melt volume index MVI, the polymer is melted in a heated container provided with an outlet nozzle. The melt is pushed through the nozzle by means of a piston that moves at a constant feed rate (ie not by means of an applied load as with the MVR or MVI). The melt pressure is measured at constant piston feed. In the course of the measurement time, the rubber phase crosslinks (gel formation) due to the thermal-oxidative aging of the polymer. This increases the melt viscosity and thus the melt pressure.

The effect of a stabilizer can be caused by an increase in the melt pressure which is more or less delayed compared to the non-stabilized polymer be recognized. The pressure difference between the start (time t = t ₀ ) and the end (t = t _E ) of the measurement time, the so-called cross-linking pressure p _v, serves as a measure of the aging stability and thus as a measure of the effectiveness of the stabilization. The following applies: p _v = p (t _E ) - p (t ₀ ).

The lower the pressure difference, the less the melt pressure or melt viscosity increased, ie the less crosslinked the rubber phase (less gel formation) and the lower the polymer aging. Accordingly, the following applies: the lower the crosslinking pressure p _v , the more effective the stabilization.

The melt temperature in the rheography was 250 or 270 ° C., and the crosslinking pressure p _{v was determined} after t _E = 15, 30, 45 and 60 min measuring time.

The compositions and results are summarized in Table 1 below.

Table 1: Composition and results, V for comparison

100% by weight missing is block copolymer A. Amounts of stabilizer based on the sum of components A to D, that is the stabilized block copolymer without mixed polystyrene. The rheographically examined product also contained 12% by weight of polystyrene, 2) approximate value 3. Production of the molding compositions containing a star-shaped styrene-butadiene block copolymer

The procedure was as described under point 1 above, but instead of the phosphite C1, the phosphite C2 was used and no polystyrene was added. D1 alone was used as the sterically hindered phenol.

The stabilized styrene-butadiene block copolymer obtained was tested rheographically at 270 ° C. for resistance to aging as described under item 2 above.

It was also examined for speck formation. For this purpose, the polymer granules were extruded on a flat film extruder from Brabender at 200 ° C. to a film of 100 μm thickness, and the number of gel particles on the film was determined by light microscopy.

Table 2 summarizes the compositions and results. The number of gel particles per square meter of film surface whose diameter was greater than 100, 300 or 600 μm is given. Table 2: Composition and results

100% by weight of the missing fraction is block copolymer A. Amounts of stabilizer based on the sum of components A to D, that is to say the stabilized block copolymer. The examples show that the stabilizer system according to the invention significantly improved the aging resistance of the styrene-butadiene block copolymers. In particular, gel formation was greatly reduced and fewer specks developed.

Claims

claims

1. Containing thermoplastic molding compositions, the sum adding up to 100% by weight, a) at least one block copolymer A, containing in polymerized form, based on A, a1) 10 to 90% by weight of at least one styrene monomer, and a2) 10 to 90% by weight of at least one diene monomer, and as stabilizers, based on the molding composition, b) 0.001 to 0.5% by weight of at least one phenolic acrylate B of the formula I.

in which R ¹ , R ² and R ³ independently of one another are hydrogen or an alkyl radical, aryl radical, alkylaryl radical or cycloalkyl radical having 1 to 20 carbon atoms, and Z is tert-pentyl, c) 0.05 to 1% by weight at least one organic phosphite C, and d) 0.001 to 1% by weight of at least one stabilizer compound D selected from sterically hindered phenols which differ from the phenolic acrylate B and aromatic amines.

2. Molding compositions according to claim 1, wherein the block copolymer A is a styrene-butadiene block copolymer.

3. Molding compositions according to claims 1 to 2, wherein the block copolymer A has a star-shaped structure.

4. Molding compositions according to claims 1 to 3, wherein the phenolic acrylate B is a compound of formula II

is in which Z means tert-pentyl.

5. Molding compositions according to claims 1 to 4, wherein the organic phosphite C is selected from tris (nonylphenyl) phosphite and tris (2,4-di-tert-butylphenyl) phosphite.

Molding compositions according to claims 1 to 5, wherein the stabilizer compound D is a sterically hindered phenol of the formula III

or of formula IV

or their mixture.

7. Molding compositions according to claims 1 to 6, wherein the quantitative ratio of stabilizer compound D to phenolic acrylate B is from 0.5: 1 to 50: 1 parts by weight.

8. Molding compositions according to claims 1 to 7, wherein the molding composition is neutral to slightly acidic.

9. A process for the preparation of the molding compositions according to claims 1 to 8, wherein the molding composition is neutral to weakly acidic by adding CO ₂ and water during manufacture.

10. Use of the molding compositions according to claims 1 to 8 for the production of moldings, foils, films, fibers and foams.

11. Moldings, foils, films, fibers and foams from the molding compositions according to claims 1 to 8.

Block copolymers of styrene monomer and diene monomer with an improved stabilizer system

Summary

Containing thermoplastic molding compositions, the sum being 100% by weight,

a) at least one block copolymer A, containing in polymerized form, based on A, a1) 10 to 90% by weight of at least one styrene monomer, and a2) 10 to 90% by weight of at least one diene monomer,

and as stabilizers, based on the molding compound,

b) 0.001 to 0.5% by weight of at least one phenolic acrylate B of the formula

wherein R ¹ , R ² and R ³ independently of one another are hydrogen or an alkyl radical, aryl radical, alkylaryl radical or cycloalkyl radical having 1 to 20 carbon atoms, and Z is tert-pentyl, c) 0.05 to 1% by weight of at least one organic phosphite C, and

d) 0.001 to 1% by weight of at least one stabilizer compound D selected from sterically hindered phenols which differ from the phenolic acrylate B and aromatic amines.