WO2001034699A1

WO2001034699A1 - Thermoplastic molding materials with low inherent color and good processability

Info

Publication number: WO2001034699A1
Application number: PCT/EP2000/010773
Authority: WO
Inventors: Norbert Güntherberg; Peter Ittemann; Axel Gottschalk
Original assignee: Basf Aktiengesellschaft
Priority date: 1999-11-09
Filing date: 2000-10-31
Publication date: 2001-05-17
Also published as: DE19953955A1

Abstract

Thermoplastic molding materials containing (A) 80 -99.995 wt. %, in relation to the total weight of the molding material, of a copolymer comprised of (a1) 50 -99 wt. %, in relation to (A), of at least one vinyl aromatic monomer, and (a2) 1 - 50 wt.- %, in relation to (A), of at least one polar, copolymerizable comonomer, (B) 0.005 - 20 wt. %, in relation to (A), (B), and optionally (C), a rubber elastic block copolymer consisting of at least one polymerized unit block BA comprising aromatic monomers and forming a hard phase and at least one elastomer bock BB/A consisting of at least one polymerized unit comprising vinyl aromatic monomers in addition to a diene and forming a soft phase, wherein the glass transition temperature Tg of block BA is above 25 °C and the glass transition temperature of clock BB/A is below 25 °C, and (C) 0-300 wt. %, in relation to (A) and (B) of at least one other polymer, (D) 0 -30 wt. %, in relation to the total weight of the molding materials, of other additives and auxiliary processing agents.

Description

Thermoplastic molding compounds with low intrinsic color and easy to process

description

The present invention relates to thermoplastic molding compositions containing improved processing properties

(A) 80 to 99.995% by weight, based on the total weight of the molding composition, of a copolymer

(ai) 50 to 99% by weight, based on (A), of at least one vinyl aromatic monomer, and

(a ₂ ) 1 to 50% by weight, based on (A), of at least one polar, copolymerizable comonomer from the group acrylonitrile, methacrylonitrile, esters of acrylic acid or methacrylic acid having 1 to 4 carbon atoms in the alkyl radical, maleic anhydride and its imides , (Meth) acrylamide and / or vinyl alkyl ether with 1 to 8 carbon atoms in the alkyl radical or a mixture thereof,

(B) 0.005 to 20% by weight, based on (A), (B), and optionally (C), of a rubber-elastic block copolymer

at least one polymerized unit of a block B _A and comprising vinyl aromatic monomers which forms a hard phase

at least one polymerized unit of a vinyl aromatic monomer and a diene-containing elastomeric block B _B / _A forming a soft phase

wherein the glass transition temperature T _g of block B _{A is} above 25 ° C and that of block B _B / _{A is} below 25 ° C and

the phase volume ratio of block B _A to block B _B / _A is chosen so that the proportion of the hard phase in the total block copolymer is 1 to 40 vol. % and the weight fraction of the diene in the entire block copolymer is less than 50% by weight,

the relative proportion of 1,2-linkages of the polydiene, based on the sum of 1,2- and 1,4-cis / trans linkages, is below 15%. and

(C) 0-300% by weight, based on (A) and (B) of at least one polymer selected from polycarbonates, styrene-maleic anhydride copolymers, imidized styrene-maleic anhydride copolymers, polymethyl methacrylates, polymethacrylimides, styrene -Phenyl-maleimide copolymers and styrene -acrylonitrile-phenylmaleimide copolymers.

(D) 0 to 30% by weight, based on the total weight of the molding compositions, customary additives and processing aids.

The invention further relates to the use of these molding compositions for the production of moldings, foils, fibers and foams, and to shaped bodies, foils, fibers and foams made from these molding compositions. Finally, the invention relates to a method for producing the molding compositions.

Mixtures of thermoplastic copolymers based on vinyl aromatic polymers are known as SAN polymers

Known to those skilled in the art and commercially available. Blends of such SAN polymers with other thermoplastics, in particular polycarbonates or imidized styrene-maleic anhydride copolymers, are also known.

As a result of the introduction of ever faster processing machines, such products in particular require a high level of fluidity during processing in injection molding and unbroken demouldability. In the shaping by deep drawing, a high elongation at break is particularly important.

Various additives are generally used to optimize these properties, but these often only improve one parameter and negatively influence another desired property. Additives to improve the flowability and the deep-drawing properties often lead to a loss of mechanical properties, while additives to improve the demoldability often impair the flowability.

Since SAN (styrene-acrylonitrile) polymers are transparent, they can be dyed particularly well in any color, either transparent or non-transparent (opaque), by adding colorants (for example dyes and / or pigments). However, the slightly yellowish intrinsic color of the SAN polymer (yellow tinge) is annoying, since it falsifies the desired shade and makes it difficult to obtain the desired shade right away. Usually the yellow tinge is made by adding a soluble one Blue dye is compensated ("toned up") or higher amounts of colorant are used to obtain the desired shade. Both measures make the product more expensive because colorants are comparatively expensive.

The older, as yet unpublished application DE Az. 198 58 141.6 discloses molding compositions of the ABS and ASA type which are impact-resistant due to the rubber-elastic graft polymer they contain. The molding compositions described therein contain a block copolymer made from hard vinylaromatic blocks and soft vinylaromatic die blocks. DE Az mentions rubber-free molding compositions. 198 58 141.6 not.

The task was to remedy the disadvantages described. The object of the present invention was, in particular, to provide thermoplastic molding compositions based on vinylaromatic copolymers which have a balanced spectrum of properties. In particular, the task was to provide molding compositions with good mechanical properties (high impact strength and flexural strength, good heat resistance), good processing properties (good flowability and demoldability) and at the same time a low intrinsic color (low yellow tinge).

Accordingly, the molding compositions defined at the outset were found.

Furthermore, the use of the molding compositions for the production of moldings, films, fibers and foams, and a process for the production of the molding compositions, finally the moldings, films, fibers and foams, were found.

As component (A), the molding compositions according to the invention contain 80 to 99.995%, preferably 85 to 99.99% by weight, particularly preferably 90 to 99.9% by weight, based on the total weight of the molding composition, of a copolymer

(ai) 50 to 99, preferably 55 to 90 and in particular 65 to 85% by weight, based on (A), of vinyl aromatic monomers, preferably styrene and / or substituted styrenes of the general formula I

R2

with R ¹ , R ² : independently of one another H or -CC ₈ alkyl,

n: 0, 1, 2 or 3

and

(a) 1 to 50, preferably 10 to 45 and in particular 15 to

35% by weight, based on (A), of at least one polar, copolymerizable comonomer from the group acrylonitrile, methacrylonitrile, esters of acrylic acid or methacrylic acid with 1 to 4 carbon atoms in the alkyl radical, maleic anhydride and its imides, (meth) acrylic id and / or vinyl alkyl ether having 1 to 8 carbon atoms in the alkyl radical or a mixture thereof.

Such products can e.g. are produced by the process described in DE-A 10 01 001 and DE-A 10 03 436. Such copolymers are also commercially available. The weight-average molecular weight determined by light scattering is preferably in the range from 40,000 to 2,000,000, in particular from 40,000 to 1,000,000, particularly preferably from 80,000 to 250,000, which viscosity numbers are in the range from 40 to 200, in particular from 40 to 160 and particularly preferably 50 to 110 ml / g, corresponds (measured according to DIN 53726 in 0.5% by weight solution in dimethylformamide at 25 ° C).

Preferred monomers (ai) are styrene, α-methylstyrene and mixtures thereof. Preferred monomers (a) are acrylonitrile, methacrylonitrile and mixtures thereof.

The polymer (A) can also be a mixture of different copolymers e.g. B. of styrene or α-methylstyrene and acrylonitrile, which differ for example in the content of acrylonitrile or in the average molecular weight.

The proportion of component (B) in the molding compositions, based on the sum of components (A), (B) and, if appropriate, (C), is 0.005 to 20, preferably 0.01 to 15 and particularly preferably 0.1 to 10 wt .-%.

Component (B) is a rubber-elastic block copolymer

at least one polymerized unit of a block B _A and having vinyl aromatic monomers and forming a hard phase at least one polymerized unit of a vinyl aromatic monomer and a diene-containing elastomeric, soft phase-forming block B _B / _A , where

the glass transition temperature T _g of block B _{A is} above 25 ° C., preferably above 50 ° C., and that of block B _B / _{A is} below 25 ° C., preferably below 5 ° C., and

the phase volume ratio of block B _A to block B _B / _A is selected such that the proportion of the hard phase in the entire block copolymer is 1 to 40% by volume and the proportion by weight of the diene is less than 50% by weight, where

the relative proportion of 1,2-linkages of the polydiene, based on the sum of 1,2- and 1,4-cis / trans linkages, is below approximately 15%, preferably below 12%.

Detailed information on the structure and manufacture of component B is disclosed in DE-A 19 615 533, to which reference is made here.

Preferred vinylaromatic compounds are styrene and also α-methylstyrene, 1, 1-diphenylethylene and vinyltoluene and mixtures of these compounds. Preferred dienes are butadiene and isoprene, also piperylene, 1-phenylbutadiene and mixtures of these compounds.

A particularly preferred monomer combination is butadiene and styrene. All of the weight and volume information below relates to this combination; if the technical equivalents of styrene and butadiene are used, the information may have to be converted accordingly.

The B _B / _A block is composed, for example, of 75-30% by weight of styrene and 25-70% by weight of butadiene. A soft block particularly preferably has a butadiene content between 35 and 70% and a styrene content between 65 and 30%.

The weight fraction of the diene in the entire block copolymer is 15-65% by weight in the case of the styrene / butadiene monomer combination, and that of the vinylaromatic component accordingly

85-35% by weight. Butadiene-styrene block copolymers with a monomer composition of 25-60% by weight of diene and are particularly preferred

75-40% by weight of vinyl aromatic compound.

A block copolymer B can e.g. through one of the general

Formulas 1 through 11 are shown: (1) (B _A -B ( _B / A) ⁾ n;

(2) (B _A -B ( _B / _A )) _n -B _A ;

(3) B (B / A) ^{_ (B} AB (B / A)) ιι ^;

(4) X - [(BA-B (B / A)) n-π_ + i;

(5) X- (B (B / A) - ^B A) n] m + 1 »'

(6) X- (B _A -B (B / A)) n ^_B Al m + 1 • '

(7) X- (B (B / A) -BA) n ^_B (B / A) 1m + 1;

(8) Y- (BA-B ( _B / A)) i m + 1 »'

(9) Y- ( ^B (B / A) - ^B A) IJ m + 1 / '

(10) y- (B _A _B (B / A)) Π ^_ BA] m + 1 / ^*

(11) Y- (B (B / A) ^-B A) n ^_ B (B / A) 1m + 1;

where B _{A stands} for the vinylaromatic block and B (B / _A ) for the soft phase, that is to say the block built up statistically from diene and vinylaromatic units, X the rest of an n-functional initiator, Y the rest of an m-functional coupling agent and m and n are natural numbers from 1 to 10.

Block copolymers of one of the general formulas B _A -B (B / _A ) - ^B _A - X- [-B (B / A) -BA32 and Y- [-B _(B / A) ~ B _A ] 2 ⁽ meaning From the cuts ^¬ as above) and a block copolymer whose soft phase is divided into blocks is particularly preferred

(12) B (B / A) I-B (B / A) 2;

(13) B (B / A) I-B (B / A) 2-B (B / A) l;

(14) B ( _B / A) 1-B (B / A) 2-B (B / A) 3;

the blocks being constructed differently or their vinylaromatic / diene ratio in the individual blocks B < _B / _A ) changing such that a composition gradient B (β / A) pl ^< B ( _B / _A ) P2 ^<<: B ( _B / A) p3 ... occurs, the glass transition temperature T _{g of} each sub-block being below 25 ° C. Before block copolymers, which have, for example, p repeating sections (sub-blocks) with a changing monomer structure within a block B ( _B / A), the p Monomers are formed, where p is an integer between 2 and 10. The portionwise addition can serve, for example, to control the heat balance in the reaction mixture.

A block copolymer which has a plurality of blocks B ( _B / _A ) and / or B _A , each with a different molecular weight per molecule, is also preferred.

The block polymers are preferably produced by anionic polymerization in a non-polar solvent, the initiation being carried out using organometallic compounds. Compounds of alkali metals, especially lithium, are preferred. Examples of initiators are methyl lithium, ethyl lithium, propyllithium, n-butyllithium, sec. Butyllithium and tert. Butyl lithium. The organometallic compound is added as a solution in a chemically inert (inert) hydrocarbon. The dosage depends on the desired molecular weight of the polymer, but is generally in the range from 0.002 to 5 mol%, if it is based on the monomers. Aliphatic hydrocarbons such as cyclohexane or methylcyclohexane are preferably used as solvents.

The statistical blocks of the block copolymers which simultaneously contain vinylaromatic and diene are preferably prepared with the addition of a soluble potassium salt, in particular a potassium alcoholate.

There is the idea that the potassium salt enters into a metal exchange with the lithium carbanion ion pair, potassium carbanions forming, which preferably attach styrene, while lithium cabanions preferably add butadiene. Because potassium carbanions are much more reactive, a small fraction, namely 1/10 to 1/40, is enough to make the incorporation of styrene and butadiene equally likely on average, together with the predominant lithium carbanions. There is also the idea that during the polymerization process there is often a metal exchange between the living chains and between a living chain and the dissolved salt, so that the same chain preferably adds styrene and then butadiene again. As a result, the copolymerization parameters are then approximately the same for styrene and butadiene.

Particularly suitable potassium salts are potassium alcoholates, in particular tertiary alcoholates with at least 7 carbon atoms. Typical corresponding alcohols are, for example, 3-ethyl-3-pentanol and 2, 3-dimethyl-3-pentanol. Tetrahydrolinalool (3, 7-dimethyl-3-octanol) proved to be particularly suitable. Basically suitable In addition to potassium alcoholates, there are also other potassium salts which are inert towards metal alkyls. These include dialkyl potassium amides, alkylated diaryl potassium amides, alkyl thiolates and alkylated aryl thiolates.

At the time when the potassium salt is added to the reaction medium, the following should be said. Usually at least parts of the solvent and the monomer for the first block are placed in the reaction vessel. It is not advisable to add the potassium salt at this point as it is at least partially hydrolyzed to KOH and alcohol by traces of protic impurities. The potassium ions are then irreversibly deactivated for the polymerization. Therefore, the lithium organyl should be added and mixed in first, then the potassium salt. If the first block is a homopolymer, it is advisable to add the potassium salt just before the statistical block is polymerized.

The potassium alcoholate can easily be prepared from the corresponding alcohol by stirring a cyclohexane solution in the presence of excess potassium-sodium alloy. After 24 hours at 25 ° C, the evolution of hydrogen and thus the reaction is complete. The reaction can also be shortened to a few hours by refluxing at 80 ° C. An alternative implementation is to use alcohol with a small excess

Potassium methylate, potassium ethylate or potassium tert-butylate in the presence of a high-boiling inert solvent such as decalin or ethylbenzene, to distill off the low-boiling alcohol, here methanol, ethanol or tertiary butanol, to dilute the residue with cyclohexane and to filter off excess poorly soluble alcoholate.

The proportion of 1, 2 linkages in relation to the sum of 1,2 and 1, 4 linkages of diene is achieved by adding the potassium compound in general. between 11 and 9%. In contrast, the proportion of 1,2- or 1,4-linkages of the diene units when using a Lewis base according to DE-A 44 20 952 e.g. a value of 15-40% for the 1,2- and 85-60% for the 1,4-linkages, in each case based on the total amount of diene units polymerized.

The polymerization temperature can be between 0 and 130 ° C. The temperature range between 30 and 100 ° C. is preferred.

The volume fraction of the soft phase B _B / _A composed of diene and vinyl aromatic sequences is 60 to 99, preferably 70 to 90 and particularly preferably 80 to 90% by volume. The from the Blocks B _A formed from vinyl aromatic monomers form the hard phase, the volume fraction of which corresponds to 1 to 40, preferably 10 to 30 and particularly preferably 10 to 20% by volume.

It should be noted that there is no strict correspondence between the above-mentioned quantitative ratios of vinylaromatic compound and diene, the limit values of the phase volumes and the composition given above, which result from the ranges of the glass temperature according to the invention, since they are in full tens rounded numerical values. Rather, this could only happen accidentally.

The volume fraction of the two phases can be measured by means of contrasted electron microscopy or solid-state NMR spectroscopy. The proportion of the vinyl aromatic blocks can be determined by osmium breakdown of the polydiene fraction by precipitation and weighing. The future phase ratio of a polymer can also be calculated from the amounts of monomer used if it is allowed to polymerize completely each time.

In the block copolymer, the quotient of the volume fraction in percent of the soft phase formed from the B ( _B / _A ) blocks and the proportion of diene units in the soft phase for the styrene / butadiene combination is between 25 and 70% by weight.

The glass transition temperature (T _g ) is influenced by the static incorporation of the vinylaromatic compounds into the soft block of the block copolymer and the use of potassium alcoholates during the polymerization. A glass transition temperature between -50 and + 25 ° C, preferably -50 to + 5 ° C is typical. In the case of the potassium-catalyzed statistical copolymers according to the invention, the glass transition temperature is on average 2 to 5 ° C. lower than that of the corresponding Lewis base-catalyzed products, because the latter have an increased proportion of 1,2-butadiene linkages. 1,2-polybutadiene has a glass transition temperature that is 70-90 ° C higher than 1,4-polybutadiene.

The molecular weight of the block B _A is generally between 1000 and 200,000, preferably between 3,000 and 80,000 [g / mol]. The B blocks can have different molar masses within one molecule.

The molecular weight of block B ( _B / _A ) is usually between 2,000 and 250,000 [g / mol], values between 5,000 and 150,000 [g / mol] are preferred. A block B ( _B / _A ) can also, like a block B _A, within a

Different molecular weight values.

The coupling center X is formed by the reaction of the living anion chain ends with an at least bifunctional coupling agent. Examples of such compounds can be found in US 3,985,830, US 3,280,084, US 3,637,554 and US 4,091,053. For example, epoxidized glycerides such as epoxidized linseed oil or soybean oil are used; divinylbenzene is also suitable. Dichlorodialkylsilanes, dialdehydes such as terephthalaldehyde and esters such as ethyl formate or ethyl benzoate are particularly suitable for dimerization.

Preferred polymer structures are B _A -B ( _B / _A ) ~ CA; X ~ [ ^_ ( _B / A) ^_ BA] 2 and Y- [-B ( _B / _A ) "B _A ] ₂ 'where the statistical block B ( _B / A) itself again in blocks B _(BI / _AI ) ^-B _(B2 / _A2) ~ B _(B3 / A3) - • • • can be divided Before Trains t ^¬ is the random block of 2 to 15 random part-blocks, particularly preferably from 3 to 10 sub-blocks, the division of the random block B.. ( _B / _A ) in as many sub-blocks B _Bn / _A n offers the decisive advantage that even with a continuously changing composition (a gradient) within a sub-block B _Bn / _An / as it occurs in anionic polymerization under practical conditions is difficult to avoid (see below) that the B ( _B / _A ) block as a whole behaves like an almost perfect statistical polymer, so it makes sense to add less than the theoretical amount of potassium alcoholate be endowed with a high proportion of diene ate the polymer, even below the glass transition temperature of the predominant B ( _B / _A ) blocks, retains a residual toughness and did not become completely brittle.

The block copolymers according to the invention have a spectrum of properties which is very similar to that of soft PVC, but can be produced completely free of migratable, low molecular weight plasticizers. They are stable against crosslinking under the usual processing conditions (180 to 220 ° C). The excellent stability of the polymers according to the invention against crosslinking can be clearly demonstrated by means of rheography. The experimental setup corresponds to that of the MVR measurement. With a constant melt flow rate, the pressure rise is recorded as a function of time. The polymers according to the invention show no pressure rise even after 20 minutes at 250 ° C. and result in a smooth melt strand, while in a comparison sample produced according to DE-A 44 20 952 with tetrahydrofuran, the pressure triples and the pressure increases under the same conditions A barbed wire-like strand typical of networking

Appearance.

The polymerization is carried out in several stages and, for example, in the case of monofunctional initiation, the production of the hard block B _A begins. Some of the monomers are placed in the reactor and the polymerization is started by adding the initiator. In order to achieve a defined chain structure that can be calculated from the monomer and initiator metering, it is advisable to carry out the process up to a high conversion (over 99%) before the second monomer is added. However, this is not absolutely necessary.

The sequence of the monomer addition depends on the selected block structure. In the case of monofunctional initiation, for example, the vinylaromatic compound is either initially introduced or metered in directly. A cyclohexane solution of the potassium alcoholate is then added. Then diene and vinyl aromatic should be added at the same time if possible. The addition can take place in several portions. The statistical structure and the composition of block B ( _B / _A ) are determined by the quantitative ratio of diene to vinylaromatic compound, the concentration of the potassium salt and the temperature. The diene takes up a proportion by weight of 25% to 70% relative to the total mass, including vinyl aromatic compound. Block B _A can then be polymerized by adding the vinylaromatic. Instead, the required polymer blocks can also be connected to one another by a coupling reaction. In the case of functional initiation, the B ( _B / _A ) block is built up first, followed by the B _A block.

Further processing takes place according to the usual procedures. It is advisable to work in a stirred kettle and terminate the polymerization with an alcohol such as isopropanol, to make it weakly acidic with CO / water in the usual way before further processing, to polymerize with an oxidation inhibitor and a radical scavenger (commercial products such as trisnonylphenyl stabilize phosphite (TNPP) or α-tocopherol (vitamin E) or products available under the trade name Irganox 1076 or Irganox 3052), remove the solvent by conventional methods, extrude and granulate.

As component (C), the thermoplastic molding compositions according to the invention can contain 0 to 300% by weight, based on the sum of (A) and (B), preferably 0 to 200% by weight of at least one polymer selected from polycarbonates, styrene-maleic anhydride copolymers - Ren, imidized styrene-maleic anhydride copolymers, poly methyl methacrylates, polymethacrylimides, styrene - phenyl aleinini - mid copolymers, styrene - acrylonitrile - phenyl maleimide copolymers and methyl methacrylate - phenyl maleimide copolymers.

Suitable polycarbonates are, for example, those based on diphenols of the general formula II

wherein Z is a single bond, a Cι ~ to C ₃ alkylene, a C ₂ - to C ₃ alkylidene, a C ₃ - to C _δ cycloalkylidene, and -S- or -S0 ₂ - means.

Preferred diphenols of the formula II are, for example, 4,4'-dihydroxydiphenyl, 2,2-bis (4-hydroxyphenyl) propane,

2, 4-bis (4-hydroxyphenyl) -2-methylb an, 1, 1-bis (4-hydroxyphenyl) cyclohexane. 2,2-Bis- (4-hydroxyphenyl) propane and 1,1-bis (4-hydroxyphenyl) cyclohexane are particularly preferred. Both homopolycarbonates and copolycarbonates are suitable as component (C); in addition to the bisphenol A homopolymer, the copolycarbonates of bisphenol A are preferred.

The suitable polycarbonates can be branched in a known manner, preferably by incorporating 0.05 to 2.0 mol%, based on the sum of the diphenols used, of at least trifunctional compounds, for example those with three or more than three phenolic OH- Groups. Furthermore, the polycarbonates suitable as component (C) on the aromatic units can be substituted one to three times with halogen atoms, preferably with chlorine and / or bromine. However, halogen-free compounds are particularly preferred.

Polycarbonates which have relative viscosities h _re of 1.10 to 1.50, in particular 1.25 to 1.40, have proven to be particularly suitable. This corresponds to average molecular weights M _w (weight average) of 10,000 to 200,000, preferably 20,000 to 80,000.

The diphenols of the general formula II are known per se or can be prepared by known processes. The polycarbonates can be prepared, for example, by reacting the diphenols with phosgene by the interfacial process or with phosgene by a process in a homogeneous phase (the so-called pyridine process), the molecular weight to be set in each case being achieved in a known manner by a corresponding amount of known chain terminators , (Regarding polydiorganosiloxane-containing polycarbonates, see for example DE-A 33 34 782).

Suitable chain terminators are, for example, phenol, p-tert-butylphenol but also long-chain alkylphenols such as 4- (1,3-tetramethyl-butyl) phenol, according to DE-A 28 42 005 or monoalkylphenols or dialkylphenols with a total of 8 to 20 carbon atoms in the alkyl substituents according to DE-A 35 06 472, such as p-nonylphenyl, 3, 5-di-tert-butylphenol, p-tert. -Octylphenol, p-dodecylphenol, 2- (3, 5-dimethyl-heptyl) -phenol and 4- (3, 5-dimethyl-heptyl) -phenol.

Other suitable polycarbonates are those based on hydroquinone or resorcinol.

Suitable copolymers of styrene and maleic anhydride (MSA) are e.g. prepared by radical copolymerization of styrene with MA, preferably in solution or in bulk. The molar ratio MSA: styrene is preferably 1: 1 to 0.01: 1. Those skilled in the art can take further details e.g. Ullmann's Encyklopadie der Technischen Chemie, 14th edition, Verlag Chemie, Weinheim 1980, Volume 19, Chap. Polystyrene No. 4.3 and 5.8.3.

Suitable imidized styrene-MSA copolymers are obtained by subsequent reaction of the styrene-MSA copolymers with amines. The functional group of the MSA units is first amidated in a two-stage reaction, after which the ring closure to the maleic imide takes place. Suitable amines are e.g. Methylamine, ethylamine, cyclohexylamine and aniline. The reaction with the amines can e.g. in solution (for example in a stirred tank reactor) or in the melt (e.g. continuously, in particular in an extruder, reactive extrusion).

Suitable polymethyl methacrylate (PMMA) is, for example, polymerization in bulk, emulsion, solution or suspension of methyl methacrylate (MMA) or MMA mixtures containing up to 20% by weight of comonomers. Suitable comonomers are, for example, methyl, ethyl and butyl acrylate. Polymerization is usually carried out by free radicals at preferred temperatures of 40 to 150 ° C., or anionically at low temperatures, or coordinatively using transition metal catalysts. Radically and coordinatively polymerized PMMA contains prefers products with certain steric configurations. Bulk products are usually manufactured in bulk, solution or suspension. The specialist can find more information, for example, H. Raudi-Puntigam, T. Völker: Chemistry, Physics and Technology of Plastics in Individual Presentations, Volume 9: Acrylic and Methacrylic Compounds, Springer-Verlag 1967.

Suitable polymethacrylimides are prepared analogously to the imidized styrene-MSA copolymers by reacting PMMA with amines, as described, for example, in DE-A 41575, EP-A 549922, EP-A 576877 and DE-AS 1165861 is.

Suitable styrene-phenyl maleimide copolymers, styrene-acrylonitrile-phenyl maleimide copolymers and methyl methacrylate-phenyl maleimide copolymers are e.g. prepared by radical solution polymerization of the corresponding monomers. Details are given, for example, in J. Macromol. Be. All, p. 267 (1977), U.S. Patent 4,451,617 and U.S. Patent 4,491,647.

All of the polymers (C) mentioned are known and commercially available.

In addition to components (A), (B), (C), the thermoplastic molding compositions may also contain conventional additives and processing aids as component (D) in an amount of 0 to 30% by weight, based on the total weight of the molding compositions. Such additives and processing aids are lubricants and mold release agents, colorants such as pigments and dyes, flame retardants, antioxidants, light stabilizers, fibrous and powdery fillers and reinforcing agents and antistatic agents in the amounts customary for these agents.

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 150 to 300 ° C. However, the components can also be mixed "cold" without melting and the powdery or granular mixture is only melted and homogenized during processing.

The present invention therefore furthermore relates to a process for producing the thermoplastic molding compositions according to the invention by mixing the components by mixing processes known per se. Moldings of all kinds, in particular foils and flat structures, can be produced from the molding compositions. The films can be produced by extrusion, rolling, calendering and other processes known to the person skilled in the art. The molding compositions according to the invention are formed by heating and / or friction alone or with the use of plasticizing or other additives to form a processable film or a sheet (plate). The processing into three-dimensional shaped bodies of all kinds takes place, for example, by injection molding.

Another object of the present invention is thus the use of the thermoplastic molding compositions according to the invention for the production of moldings, films, fibers and foams. Furthermore, the molded articles obtainable by using the thermoplastic molding compositions are films, fibers and foams.

The thermoplastic molding compositions according to the invention have better flowability than, at the same time, improved mold release properties, deep-drawing strength and, in particular, a lower intrinsic color (less yellow tinge) and are largely free of evaporating and exuding components. They can be colored precisely and with small amounts of colorant.

They are suitable for the production of moldings, foils (especially sheets), fibers and foams, which can be further processed by thermoforming and deep drawing, and especially for the production of injection molded parts, especially for fast processing with short cycle times.

Examples

The following components were produced (all percentages are% by weight)

A: Production of component A:

Component A was produced by the process of continuous solution polymerization, as described in the plastics handbook, ed. R. Vieweg and G. Daumiller, vol. V "Polystyrene", Carl-Hanser-Verlag, Munich 1969, pages 122 to 124, is described.

AI: component AI: A copolymer of styrene and acrylonitrile with 25 wt .-% acrylonitrile (AN) and a viscosity number of 60 ml / g, measured as a 0.5% solution in dimethylformamide according to DIN 53726 at 25 ° C.

A2: component A-II

A copolymer of styrene and acrylonitrile with 35% by weight acrylonitrile and a viscosity number of 80 ml / g, measured as a 0.5% solution in dimethylformamide according to DIN 53726 at 25 ° C.

A3: Component A-III:

A copolymer of styrene and acrylonitrile with 24 wt .-%, acrylonitrile and a viscosity number of 64 ml / g, measured as a 0.5% solution in dimethylformamide according to DIN 53726 at 25 ° C.

A4: component A-IV

A copolymer of styrene and acrylonitrile with 24% by weight acrylonitrile and a viscosity number of 80 ml / g, measured as a 0.5% solution in dimethylformamide according to DIN 53726 at 25 ° C.

B: Production of component B:

To produce component B, a 50 liter stainless steel autoclave that could be heated and cooled simultaneously and was equipped with a crossbar stirrer was used by flushing with nitrogen, boiling with a solution of sec-butyllithium and 1,1-diphenylethylene in a molar ratio of 1: 1 prepared in cyclohexane and drying.

Then 22.8 l of cyclohexane were introduced and the amounts of initiator, monomers and potassium alcoholate given in Table 1 were added. The polymerization time, start and end temperatures T _A and T _{E / are also given} , the monomer feed time always being small compared to the polymerization time.

The temperature of the reaction mixture was controlled by heating or cooling the reactor jacket. After the end of the reaction (consumption of the monomers), titration was carried out until the mixture was colorless and the mixture was acidified with a 1.5-fold excess of formic acid. (Ciba-Geigy, Basel Irganox ^® 3052) and 82 g of tris-nonylphenyl phosphite are added last 34 g of a commercially available stabilizer were. The solution was worked up on a degassing extruder (three domes, forward and backward degassing) at 200 ° C. The granules obtained in this way were used to produce the molding composition.

Table 1: Polymerization and analysis of an S-SB-S block copolymer (component B)

The average molar masses (in g / mol) of the polymer were determined by gel permeation chromatography (calibration against polystyrene). M _{n means} number average, M _v viscosity average and M _w weight average.

The glass transition temperatures T _g were determined by DSC and were -55 ° C to -25 ° C for the soft phase and + 60 ° C to + 100 ° C for the hard phase. The melt volume index MVI was determined at 200 ° C. and a load of 5 kg according to DIN 53 735 and was 8.5 ml / 10 min.

Thermoplastic molding compounds

The molding compositions according to the invention and the comparison compositions were produced on a ZSK-30 extruder from Werner and Pfleiderer at 250 ° C. with 200 rpm and 10 kg / h throughput. The product was cooled in a water bath, granulated and sprayed into test specimens on an injection molding machine (Arburg Allrounder).

The following properties were determined:

Yellowness index YI: The yellowness index is a measure of the intrinsic color of the

Molding compound. The yellowness index YI was determined by determining the color coordinates X, Y, Z according to DIN 5033 with standard light D 65 and 10 ° normal observer using the following definition equation:

YI = (131.48 X - 116.46 Z) / Y

The smaller YI, the lower the intrinsic color.

Melt index MVR: it was determined on the granulate according to DIN 53735/30 at 220 ° C melting temperature and 10 kg load.

a _n : the Charpy impact strength a _n was determined on standard small bars according to ISO 179-2 / lell at 23 and at -30 ° C.

Vicat: The heat resistance according to Vicat (method B) was determined on pressing plates according to ISO 306 / B with a load of 50 N and a heating rate of 50 K / h.

θf _B : the bending strength was determined on test specimens 80 x 10 x 4 mm according to ISO 178 at 23 ° C and 50% relative humidity (RH).

Table 2 summarizes the results. Table 2

¹⁾ Melting temperature [° C] / load [kg] ² > V for comparison

The pairs of examples show that with component A identical in each case, the addition according to the invention of only 5% by weight of block copolymer B significantly improves the yellowness index (lower yellowness index = lower intrinsic color). At the same time, the block copolymer improves the fluidity (larger MVR), i.e. the molding compositions according to the invention can be better processed by injection molding.

In addition, the impact strength at room temperature and in the cold is better than in the case of molding compositions which do not contain B (not according to the invention) (a _n values are higher for molding compositions according to the invention).

The improvements achieved are not at the expense of other important properties: bending strength and heat resistance remain essentially constant.

Due to the overall improved and balanced property profile of the molding compounds according to the invention, with better intrinsic color, a higher processing speed and better mold release are guaranteed.

Claims

claims

1. Thermoplastic molding compositions containing

(ai) 50 to 99% by weight, based on (A), of at least one vinylaromatic monomer, and

at least one polymerized unit of a vinyl aromatic monomer and a diene-containing elastomeric block B _B / _A / forming a soft phase

the phase volume ratio of block B _A to block B _B / _A is selected such that the proportion of the hard phase in the entire block copolymer is 1 to 40% by volume and the proportion by weight of the diene in the entire block copolymer is less than 50% by weight,

wherein the relative proportion of 1,2-linkages of the polydene, based on the sum of 1,2- and 1,4-cis / trans-linkages, is below 15%,

and (C) 0-300% by weight, based on (A) and (B) of at least one polymer selected from polycarbonates, styrene-maleic anhydride copolymers, imidized styrene-maleic anhydride copolymers, polymethyl methacrylates, polymethacrylimides, styrene - phenylmaleimide copolymer,

Styrene-acrylonitrile-phenyl maleimide copolymers, and methyl methacrylate-phenyl maleimide copolymers,

2. Thermoplastic molding compositions according to claim 1, wherein styrene or α-methylstyrene or mixtures thereof are used as component (ai).

3. Thermoplastic molding compositions according to one of claims 1 and 2, wherein as component (a) acrylonitrile or methacrylonitrile or mixtures thereof are used.

4. Thermoplastic molding compositions according to one of claims 1 to 3, characterized in that in component (B) the relative proportion of 1, 2 linkages of the polydiene, based on the sum of 1,2- and 1, 4-cis / trans links, is below 12%.

5. Thermoplastic molding compositions according to one of claims 1 to 4, characterized in that in component (B) the glass transition temperature T _g of block B _{A is} above 50 ° C and that of block B _B / _{A is} below 5 ° C.

6. Thermoplastic molding compositions according to one of claims 1 to 5, characterized in that in component (B) the vinyl aromatic monomer is selected from styrene, α-methyl styrene, vinyl toluene, 1, 1-diphenylethylene and mixtures of these compounds and the diene from butadiene, isoprene, piperylene, 1-phenylbutadiene and mixtures of these compounds.

7. Thermoplastic molding compositions according to one of claims 1 to 6, in which component (B) is represented by one of the general formulas 1 to 11: (1) (B _A -B _(B / A)) _n ;

(3) B (B / A) - (B _A -B ( _B / A)) _n ;

(4) X- (B _A -B (B / A)) ι π_ + i; (5) X- ((B / A) - A) n] m + i; (6) X- (B _A -B (B / A) JΠ-BAIΠI + I; (7) X- (B (B / A) -BA) n ^_ B (B / A)] m + 1? ( 8) Y- (BA-B ( _B / A)) n-m + i; (9) Y- (B (B / A) -BA) Π] m + 1 / '

10 (10) Y- (B _A -B (B / A)) n-BA] + l ^*

(11) Y- (B (B / A) -BA) nB (B / A)] m + 1 where B _A for the vinylaromatic block and B ( _B / _A ) for the soft phase, i.e. the statistically from diene and vinylaroma¬

15 table units, X is the rest of an n-functional initiator, Y is the rest of an m-functional coupling agent and m and n are natural numbers from 1 to 10.

8. Thermoplastic molding compositions according to one of claims 1 to 7, characterized in that in the component (B) the molecular weight of block B _{A is} between 1000 and 200,000 and that of block B ( _B / _A ) is between 2,000 and 250 000 [g / mol].

25 9. Process for the preparation of thermoplastic molding compositions according to one of claims 1 to 8, characterized in that the components are mixed according to known mixing methods.

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

11. Moldings, foils, fibers and foams obtainable using the thermoplastic molding compositions according to one of claims 1 to 8.

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