DE9110420U1 - Low-odor thermoplastic molding compounds - Google Patents

Description

The invention relates to low-odor thermoplastic molding compounds containing

A) 4-94 wt.% of a polyphenylene ether having an average molecular weight M" of 8000 to 30000.

B) 5-94 wt.% of a vinyl aromatic polymer and

C) 1-30 wt.% of a phosphine oxide of the general formula I 15

^{R1 R2}

where R ¹ , R ² and R ³ are identical or different alkyl, aryl, alkylaryl or cycloalkyl groups having 8 to 40 C atoms,

and 25

D) 0-60 wt.% of usual additives in effective amounts.

The invention also relates to the use of these molding compositions for the production of fibers, films and moldings as well as the moldings obtainable from the molding compositions according to the invention.

DE-A 25 46 621 discloses the use of triaryl phosphates, such as triphenyl phosphate, for flame retardant treatment of thermoplastic molding compounds based on polyphenylene ethers (PPE) with higher molecular weights and styrene polymers.

The addition of phosphine oxides is known from US-A 4 278 588.

However, these mixtures have the disadvantage that they lead to a strong odor during processing.

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DE-A 27 51 329 and US-A 4 154 712 disclose molding compounds made of low molecular weight PPE, styrene polymers, plasticizers and block rubber.

These can contain up to 50% by weight of one of the well-known, but very numerous, flame retardants.

The present invention was therefore based on the object of providing thermoplastic molding compounds made of polyphenylene ether and vinyl aromatic polymers which lead to a significantly reduced odor burden during processing.

According to the invention, this object is achieved by the thermoplastic molding compositions defined at the outset.
15

It has now surprisingly been found that low molecular weight polyphenylene ethers in PPE blends with phosphine oxides lead to a significantly reduced odor burden during processing.

Preferred masses of this type and their use can be found in the dependent claims.

The polyphenylene ethers A) contained in the molding compositions according to the invention are known per se. The polyphenylene ethers A) are contained in the molding compositions according to the invention in an amount of 4 to 94, preferably 10 to 80 and in particular 25 to 50 wt.%.

These are compounds based on substituted, in particular disubstituted polyphenylene ethers, where the ether oxygen of one unit is bonded to the benzene nucleus of the adjacent unit. Polyphenylene ethers substituted in the 2- and/or 6-position to the oxygen atom are preferably used. Examples of substituents are halogen atoms such as chlorine or bromine and alkyl radicals with 1 to 4 carbon atoms, which preferably do not have a tertiary hydrogen atom in the α position, e.g. methyl, ethyl, propyl or butyl radicals. The alkyl radicals can in turn be substituted by halogen atoms such as chlorine or bromine or by a hydroxyl group. Further examples of possible substituents are alkoxy radicals, preferably with up to 4 carbon atoms or phenyl radicals optionally substituted by halogen atoms and/or alkyl groups. Also suitable are copolymers of various phenols such as copolymers of 2,6-dimethylphenol and 2, 3,6-trimethylphenol. Of course, mixtures of various polyphenylene ethers can also be used.

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Examples of polyphenylene ethers are poly(2,6-dilauryl-l _f 4-phenylene ether), poly(2,6-diphenyl-l,4-phenylene ether), poly(2,6-dimethoxy-1,4-phenylene ether), poly(2,6-diethoxi-l,4-phenylene ether), poly(2-methoxy-6-ethoxy-l,4-phenylene ether), poly(2-ethyl-6-stearyloxy-1,4-phenylene ether), poly-(2,6-dichloro-l,4-phenylene ether), poly(2-methyl-6-phenyl-l,4-phenylene ether), poly(2,6-dibenzyl-l,4-phenylene ether), poly(2-ethoxy-l,4-phenylene ether), poly(2-chloro-l,4-phenylene ether), poly(2,5-dibromo-l,4-phenylene ether). Preference is given to using polyphenylene ethers in which the substituents are alkyl radicals having 1 to 4 carbon atoms, such as poly(2,6-dimethyl-1,4-phenylene ether), poly(2,6-diethyl-1,4-phenylene ether), poly(2-methyl-6-ethyl-1,4-phenylene ether), poly(2-methyl-6-propyl-1,4-phenylene ether), poly(2,6-dipropyl-1,4-phenylene ether) and poly(2-ethyl-6-propyl-1,4-phenylene ether).

Polyphenylene ethers within the meaning of the invention are also understood to include those that are modified with monomers such as fumaric acid, maleic acid or maleic anhydride.

Such polyphenylene ethers are described, among others, in WO 87/00540.

With regard to the physical properties of the polyphenylene ethers, those used in the molding compositions according to the invention are those which have an average molecular weight M _w (weight average) of 8,000 to 30,000, preferably 12,000 to 25,000 and in particular 15,000 to 25,000.

This corresponds to an intrinsic viscosity of 0.18 to 0.45, preferably from 0.25 to 0.42 and in particular from 0.3 to 0.42 dl/g, measured in chloroform at 25°C.

The molecular weight distribution is generally determined by gel permeation chromatography (Shodex separation columns 0.8 x 50 cm of type A 803, A 804 and A 805 with THF as eluent at room temperature). The PPE samples are dissolved in THF under pressure at 110 ⁰ C, injecting 0.16 ml of a 0.25 wt.% solution.

Detection is generally carried out using a UV detector. Calibration of the columns was carried out using PPE samples whose absolute molecular weight distributions were determined using a GPC-laser light scattering combination.

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Component B) is present in the molding compositions according to the invention in amounts of 5 to 94, preferably 16 to 80 and in particular 36 to 70% by weight, based on the total weight of components A) to C) and optionally D).
5

Component B) is a vinyl aromatic polymer which is preferably compatible with the polyphenylene ether used.

Examples of preferred vinyl aromatic polymers compatible with polyphenylene ethers can be found in the monograph by O. Olabisi, Polymer-Polymer Miscibility, 1979, pp. 224 to 230 and 245.

Both homopolymers and copolymers of vinylaromatic monomers with 8 to 12 carbon atoms are possible.

Monovinylaromatic compounds that are particularly suitable are styrene, as well as core- or side-chain alkylated styrenes. Examples include chlorostyrene, α-methylstyrene, styrene, p-methylstyrene, vinyltoluene and p-tert-butylstyrene.

20, however, styrene alone is used.

The homopolymers are generally prepared by known processes in bulk, solution or suspension (cf. Ulimanns Enzyklopädie der techn. Chemie, Volume 19, pages 265 to 272, Verlag Chemie, Weinheim 1980). The homopolymers can have weight average molecular weights Mw of 100 to 300,000, which can be determined by conventional methods.

Comonomers that can be used to produce copolymers include, for example, (meth)acrylic acid, (meth)acrylic acid alkyl esters with 1 to 4 C atoms in the alkyl radical, acrylonitrile and maleic anhydride as well as maleimides, acrylamide and methacrylamides as well as their N,N or N-alkyl-substituted derivatives with 1-10 C atoms in the alkyl radical.

The comonomers are contained in the styrene polymers in different amounts depending on their chemical structure. The decisive factor for the comonomer content in the copolymer is the miscibility of the copolymer with the polyphenylene ether. Such mixing limits are known and are described, for example, in US-P 4,360,618, 4,405,753 and in the publication by J.R. Fried, G.A. Hanna, Polymer Eng. Scie. Volume 22 (1982) page 7 05 ff. The copolymers are produced using known processes, which are described, for example, in Ullmann's Encyclopedia of Technical Chemistry, Volume 19, page 273 ff, Verlag Chemie, Weinheim (1980). The copolymers generally have

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mean weight average molecular weight (Mw) of 10 000 to 300 000, which can be determined by conventional methods.

Component B) is preferably impact-modified polystyrene, the rubber content of which is generally from 3 to 20% by weight, preferably from 4 to 15% by weight.

The most commonly used processes for producing impact-modified styrene polymers are polymerization in bulk or solution in the presence of a rubber, as described, for example, in US Patent 2,694,692, and processes for bulk suspension polymerization, as described, for example, in US Patent 2,862,906. Of course, other processes can also be used, provided the desired particle size of the rubber

15 phase is set.

The rubbers used are the natural or synthetic rubbers normally used for the impact modification of styrene polymers. Suitable rubbers within the meaning of the invention are, in addition to natural rubber, for example, polybutadiene, polyisoprene and copolymers of butadiene and/or isoprene with styrene and other comonomers which have a glass transition temperature, determined according to KH Illers and H. Breuer, Kolloidzeitschrift 190 (1), 16 - 34 (1963), below -20 ⁰ C.

Mixtures of impact-modified and non-impact-modified vinyl aromatic polymers can also be used, whereby the mixing ratio is arbitrary.

As component C), the molding compositions according to the invention contain a phosphine oxide of the general formula I

^R1

R ² P=O

^R3 '

where R ¹ , R ² and R ³ are identical or different alkyl, aryl, alkylaryl or cycloalkyl groups having 8 to 40 C atoms. 40

Examples of phosphine oxides are triphenylphosphine oxide, tritolylphosphine oxide, trisnonylphenylphosphine oxide, tricyclohexylphosphine oxide, tris-(&eegr;-butyl)-phosphine oxide, tris-(n-hexyl)-phosphine oxide, tris-(n-octyl)-phosphine oxide, tris-(cyanoethyl)-phosphine oxide, benzylbis-(cyclohe-

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xyl)-phosphine oxide, benzylbisphenylphosphine oxide, phenylbis-(n-hexyl)-phosphine oxide. Triphenylphosphine oxide, tricyclohexylphosphine oxide, tris-(n-octyl)-phosphine oxide and tris-(cyanoethyl)-phosphine oxide are particularly preferred.
5

The molecular weight is generally not more than 1000, preferably 150 to 800.

Mixtures of the phosphine oxides C) can of course also be used, whereby the mixing ratio is arbitrary.

The content of component C) in the molding compositions according to the invention is 1 to 30, preferably 4 to 20 and in particular 5 to 15, based on the total weight of components A) to C) and optionally D).

As component D), the thermoplastic molding compositions according to the invention can also contain conventional additives and processing aids. The proportion of these additives is generally not more than 60, in particular not more than 50 and especially not more than 30% by weight, based on the total weight of components A) to D).

Additives include impact modifiers, which can be contained in amounts of up to 20 wt.%, preferably up to 15 wt.% and which are different from component B).

Common rubbers are suitable, e.g. acrylate rubber and polymers of conjugated dienes, such as polybutadiene rubber and polyisoprene rubber. The diene polymers can be partially or fully hydrogenated in a manner known per se. Other suitable materials include: acrylonitrile-butadiene rubber, hydrogenated styrene-butadiene rubber, ethylene-propylene-diene rubber, polybutylene and polyoctamer rubbers, ionomers, block copolymers of vinyl aromatic monomers with dienes such as butadiene or isoprene (known per se from EP-A 62 282) with the structure M1M2-, M1M2M1M2-, M1M2M1- or M1M2M1'-, whereby these block polymers can also contain segments with a statistical distribution, as well as star block copolymers. Polymers of conjugated dienes such as polybutadiene rubber or polyisoprene rubber have proven to be particularly suitable. Such synthetic rubbers are familiar to the expert and are described in summary in "Ullmanns Encyklopädie der Technischen Chemie", 4th edition, volume 13, pages 595 to 634, Verlag Chemie GmbH, Weinheim 1977.

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Additives include heat and light stabilizers, lubricants and mold release agents, colorants such as dyes and pigments in usual amounts. Other additives are reinforcing agents such as glass fibers, asbestos fibers, carbon fibers, aromatic polyamide fibers and/or fillers, gypsum fibers, synthetic calcium silicates, kaolin, calcined kaolin, wollastonite, talc and chalk.

Low molecular weight or high molecular weight polymers can also be considered as additives, with polyethylene wax being particularly preferred as a lubricant.

Possible pigments include TiO ₂ and carbon black.

When using TiO ₂ , the average particle size is in the range of 50 - 400 nm, in particular 150 - 240 nm. Rutile and anatase are used in technical applications, which are optionally coated with metal oxides, e.g. Al oxide, Si oxides, oxides of Zn or siloxanes.

Soot is understood to mean microcrystalline, finely divided carbons (cf. Kunststofflexikon, 7th edition 1980).

Furnace blacks, acetylene blacks, gas blacks and thermal blacks obtained by thermal production are suitable.

The particle sizes are preferably in the range of 0.01 to 0.1 μπα and the surface areas in the range of 102 to 104 m ² /g (BET/ASTM D 3037) with DBP absorptions of 102 to 103 ml/100 g (ASTM d 2414).

The desired properties of the end products can be controlled to a large extent by the type and quantity of these additives.

The thermoplastic molding compositions according to the invention are conveniently produced by mixing the components at temperatures in the range from 250 to 320 ⁰ C in conventional mixing devices, such as kneaders, Banbury mixers and single-screw extruders, preferably with a twin-screw extruder. In order to obtain a molding composition that is as homogeneous as possible, intensive mixing is necessary. The order in which the components are mixed can be varied; two or, if appropriate, three components can be premixed or

40 all components are mixed together.

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From the thermoplastic molding compositions according to the invention, moldings with good flame retardant properties can be produced, for example by injection molding or extrusion, which in particular have a reduced odor burden during processing.
5

As a result of this range of properties, the molded articles that can be produced from the molding compositions according to the invention are particularly suitable for the production of films and semi-finished products by injection molding.

10 Examples The following components were used:

Component A) 15

A(I):Poly-2,6-dimethyl-l,4-phenylene ether with an average molecular weight (M _w ) of 16000.

A(2):Poly-2,6-dimethyl-l,4-phenylene ether with an average molecular weight (M _w ) of 24000.

A(3):Poly-2,6-dimethyl-l,4-phenylene ether with an average molecular weight (M _w ) of 40000.

25 Component B)

Impact-resistant Polystyrol® KR 27 97 from BASF AG with 13 wt.% polybutadiene, average particle size (dso value) 2-3 μηη.

30 Component C) C(I): Triphenylphosphine oxide

C(2): Triphenyl phosphate 35

C(3): Tricresyl phosphate

C(4): Diphenylpentaerythritol diphosphonate 40 The odour development was assessed according to the following test:

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The molding compounds were processed at 280 and 320°C using the injection molding process and the resulting odor development was evaluated by 5 test subjects using the school grading system. The average value was determined from the individual evaluations.
5

The composition of the molding compounds and the results of the measurements can be found in the table.

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Table

Example Component A
[Wt.%] Component B
[Wt.%] Component C
[Wt.%] Odour at processing temperature
280 ⁰ C 320 ⁰ C
Average grades 2.0 1 A(I)50 B40 C(I)10 1.6 5.4 2* A(I)50 B40 C(2) 10 3.8 5.8 3* A(3) 50 B40 C(I)10 4.0 1.4 4 A(2) 30 B62 C(I)8 1.2 4.6 5* A(2) 30 B62 C(3) 8 3.2 5.0 6* A(2) 30 B62 C(4) 8 4.2 5.8 7* A(I)32 B32 C(I)35 5.0

for comparison

σωσα

Claims (4)

A) 4-94 wt.% of a polyphenylene ether having an average molecular weight M" of 8000 to 30000. B) 5-94 wt.% of a vinyl aromatic polymer and 10 C) 1-30 wt.% of a phosphine oxide of the general formula I ^PO R ³ where R ¹ , R ² and R ³ are identical or different alkyl, aryl, alkylaryl or cycloalkyl groups having 8 to 40 C atoms, as well as D) 0-60% by weight of common additives in effective amounts. 25 2. Low-odor thermoplastic molding compositions according to claim 1, containing A) 10-80 wt.% 30 B) 16-80 wt.% C) 4-20 wt.% 3. Low-odor thermoplastic molding compositions according to claims 1 or 2, in which component A) is composed of a polyphenylene ether having an average molecular weight of 12,000 to 25,000. 4. Low-odor thermoplastic molding compositions according to claims 1 to 3, in which component C) is composed of triphenylphosphine oxide, tricyclohexylphosphine oxide or tris-(n-octyl)phosphine oxide or tris-(n-butyl)phosphine oxide or mixtures thereof. 45/91 äch/fa 22.08.91