WO1998004634A1

WO1998004634A1 - Housings of electric appliances containing small transformers

Info

Publication number: WO1998004634A1
Application number: PCT/EP1997/004035
Authority: WO
Inventors: Herbert Naarmann; Graham Edmund Mc Kee; Alfred Pirker; Hans-Josef Sterzel; Franz Brandstetter; Bernd-Steffen Von Bernstorff; Bernhard Rosenau; Ulrich Endemann; Burkhard Straube
Original assignee: Basf Aktiengesellschaft
Priority date: 1996-07-25
Filing date: 1997-07-24
Publication date: 1998-02-05
Also published as: DE19630120A1

Abstract

The invention concerns the use of thermoplastic moulding materials which are different from ABS and which, in relation to the sum of the quantities of components A, B, C and optionally D resulting in a total of 100 wt %, contain a) 1-98 wt %, preferably 1-20 wt %, in particular 1-15 wt % of a particulate emulsion polymer with a glass transition temperature of less than 0 °C and a mean particle size of 50-1000 nm, preferably 50-500 nm as component A, b) 1-98 wt %, preferably 3-30 wt %, in particular 5-25 wt % of at least one semi-crystalline polymer as component B, c) 1-98 wt %, preferably 50-95 wt %, particular 60-90 wt % polycarbonates as component C and d) 0-50 wt % fibre or particle-shaped filling materials or their mixtures as component D, for producing housings of electric appliances containing small transformers.

Description

Housings of small transformers containing electrical devices

The invention relates to housings of small transformers containing electrical devices. In particular, the invention relates to such housings which have high dimensional stability and aging resistance, in particular under thermal stress.

To date, various materials have been used to manufacture housings for small transformers, such as for low-voltage power supplies for small electrical devices.

Fire protection-equipped polyamide has only an extremely limited choice of colors due to the black-colored fire protection agent it contains. The housings also tend to shrink and warp. In a humid environment there is a high tendency to absorb water, which leads to dimensional changes. In addition, the housings are susceptible to yellowing.

Polypropylene housings tend to shrink and warp. In addition, the heat resistance is low.

PPE / HIPS blends (polyphenylene ether / high impact poly styrene) tend to yellow under thermal stress. Therefore the production of light colors is restricted. In addition, the blends have an insufficient resistance to stress cracking when exposed to household cleaners. With ABS / PC blends (acrylonitrile-butadiene-styrene / polycarbonate), fire protection equipment in some cases has a negative effect on the color stability and the UV resistance behind glass.

An object of the present invention is to provide housings for electrical equipment containing small transformers, which have high color stability and colorability, at the same time show good aging resistance, and meet the fire protection regulations.

Another object of the invention is to provide housings for small transformers containing electrical devices that avoid the disadvantages of the materials listed above.

According to the invention, these objects are achieved by using a thermoplastic molding composition different from ABS, comprising, based on the sum of the amounts of components A, B, C and, if appropriate, D, which gives a total of 100% by weight,

a: 1-98% by weight of a particulate emulsion polymer with a glass transition temperature below 0 ° C. and an average particle size of 50-1000 nm as component A,

b: 1-98% by weight of at least one amorphous or partially crystalline polymer as component B,

c: 1-98% by weight of polycarbonates as component C, and

d: 0 - 50% by weight of fibrous or particulate fillers or mixtures thereof as component D. for the manufacture of housings for small transformers containing electrical devices.

Housings of electrical devices that contain small transformers, in particular power supplies or battery chargers for accumulators, must meet the UL94 (UL Standard 94 Vertical Burning Test) fire protection regulations for the corresponding wall thicknesses. A UL-VO rating of 1.6 mm and 0.8 mm wall thickness is usually required.

It has been found that the thermoplastic molding compositions described below meet these requirements.

The thermoplastic molding compositions used according to the invention for producing the housings according to the invention are known per se. For example, DE-A-12 60 135, DE-C-19 11 882, DE-A-28 26 925, DE-A-31 49 358, DE-A-32 27 555 and DE-A-40 11 162 Molding compositions which can be used according to the invention are described.

According to one embodiment, the molding compositions used in accordance with the invention to produce the housings according to the invention which are different from ABS contain the components A, B, C and optionally D listed below, as defined below. They contain, based on the sum of the amounts of components A, B, C and, if appropriate, D, which gives a total of 100% by weight,

a: 1-98% by weight, preferably 1-20% by weight, in particular 1-15% by weight, of a particulate emulsion polymer having a glass transition temperature below 0 ° C. and an average particle size of 50-1000 nm, preferably 50 - 500 nm as component A, b: 1-98% by weight, preferably 3-30% by weight, in particular 5-25% by weight, of at least one amorphous or partially crystalline polymer as component B,

c: 1-98% by weight, preferably 50-95% by weight, in particular 60-90% by weight, of polycarbonates as component C, and

d: 0 - 50% by weight of fibrous or particulate fillers or their mixtures as component D.

The invention is explained in more detail below.

The molding compositions used to produce the housings according to the invention and the components from which they are constructed are first described.

COMPONENT A

Component A is a particulate emulsion polymer with a glass transition temperature below 0 ° C and an average particle size of 50-1000 nm.

Component A is preferably a graft copolymer

al: 1-99% by weight, preferably 55-80% by weight, in particular 55-

65% by weight, of a particulate graft base AI with a glass transition temperature below 0 ° C, a2: 1-99% by weight, preferably 20-45% by weight, in particular 35-

45% by weight of a graft A2 composed of the monomers, based on A2,

a21: 40-100% by weight, preferably 65-85% by weight, units of a vinyl aromatic monomer, preferably styrene, a substituted styrene or a (meth) acrylic acid ester or mixtures thereof, in particular styrene and / or α-methylstyrene as component A21 and

a22: up to 60% by weight, preferably 15-35% by weight, of units of an ethylenically unsaturated monomer, preferably acrylonitrile or methacrylonitrile, in particular acrylonitrile as component A22.

The graft pad A2 consists of at least one graft shell, the graft copolymer A overall having an average particle size of 50-1000 nm.

According to one embodiment of the invention, component AI consists of the monomers

all: 80-99.99% by weight, preferably 95-99.9% by weight, of a C ₈ -alkyl ester of acrylic acid, preferably n-butyl acrylate and / or ethylhexyl acrylate as component All,

al2: 0.01-20% by weight, preferably 0.1-5.0% by weight, of at least one polyfunctional crosslinking monomer, preferably diallyl phthalate and / or DCPA as component A12. According to one embodiment of the invention, the average particle size of component A is 50-800 nm, preferably 50-600 nm.

According to a further embodiment of the invention, the particle size distribution of component A is bimodal, 60-90% by weight having an average particle size of 50-200 nm and 10-40% by weight having an average particle size of 50-400 nm on the total weight of component A.

The sizes determined from the integral mass distribution are given as the average particle size or particle size distribution. The mean particle sizes according to the invention are in all cases the weight average of the particle sizes, as determined by means of an analytical ultracentrifuge according to the method of W. Scholtan and H. Lange, Kolloid-Z. and Z. Polymers 250 (1972), pages 782-796. The ultracentrifuge measurement provides the integral mass distribution of the particle diameter of a sample. From this it can be seen what percentage by weight of the particles have a diameter equal to or smaller than a certain size. The mean particle diameter, which is also referred to as the O ^ _Q value of the integral mass distribution, is defined as the particle diameter at which 50% by weight of the particles have a smaller diameter than the diameter which corresponds to the d ^ value. Likewise, 50% by weight of the particles then have a larger diameter than the d ₅₀ value. To characterize the width of the rubber Teilchengrößenvertei- lung addition to the d ₅₀ value (average particle diameter) resulting from the integral mass distribution are d ₁₀ - d grown and _Q values. The d ₁₀ or d ^ value of the integral mass distribution is defined in accordance with the d ₅₀ value with the difference that they are based on 10 or 90% by weight of the particles. The quotient * 90 * 10

= Q

* 50

represents a measure of the distribution width of the particle size. Emulsion polymers A which can be used according to the invention as component A preferably have Q values less than 0.5, in particular less than 0.35.

The glass transition temperature of the emulsion polymer A and also of the other components used according to the invention is determined by means of DSC (Differential Scanning Calorimetry) according to ASTM 3418 (mid point temperature).

Relevant common rubbers can be used as emulsion polymer A, such as epichlorohydrin rubbers, ethylene-vinyl acetate rubbers, polyethylene chlorosulfone rubbers, silicone rubbers, polyether rubbers, hydrogenated diene rubbers, polyalkylene rubber rubbers, polyalkylene rubber rubbers, polyalkylene rubber rubbers, according to one embodiment of the invention. Ethylene propylene diene rubbers, butyl rubbers and fluororubbers. Acrylate rubber, ethylene-propylene (EP) rubber, ethylene-propylene-diene (EPDM) rubber, in particular acrylate rubber, are preferably used.

Pure butadiene rubbers, such as those used in ABS, cannot be used as exclusive component A.

According to one embodiment, the diene basic building block content in the emulsion polymer A is kept so low that as few unreacted double bonds remain in the polymer. According to one embodiment, there are no basic diene building blocks in the emulsion polymer A. The acrylate is preferably alkyl acrylate rubbers of one or more Cj.g alkyl acrylates, preferably C. ₄ ₈ -alkyl acrylates, preferably at least partially butyl, hexyl, octyl or 2-ethylhexyl acrylate, in particular n-butyl and 2-ethylhexyl acrylate. These alkyl acrylate rubbers can contain up to 30 wt .-% hard polymer-forming monomers, such as vinyl acetate, (meth) acrylonitrile, styrene, substituted styrene, methyl methacrylate or vinyl ether, copolymerized.

According to one embodiment of the invention, the acrylate rubbers further contain 0.01-20% by weight, preferably 0.1-5% by weight, of cross-linking polyfunctional monomers (cross-linking monomers). Examples of these are monomers which contain 2 or more double bonds capable of copolymerization, which are preferably not conjugated in the 1,3 positions.

Suitable crosslinking monomers are, for example, divinylbenzene, diallyl maleate, diallyl fumarate, diallyl phthalate, diethyl phthalate, triallyl cyanurate, triallyl isocyanurate, tricyclodecenyl acrylate, dihydrodicyclopentadienyl acrylate, triallyl phosphate, allyl methacrylate. Dicyclopentadienyl acrylate (DCPA) has proven to be a particularly favorable crosslinking monomer (cf. DE-C-12 60 135).

Suitable silicone rubbers can be, for example, crosslinked silicone rubbers from units of the general formulas I ^ SiO, RSiO _{3 2} , R ₃ SiO _{1 2} and SiO _{2 /} , where the radical R represents a monovalent radical. The amount of the individual siloxane units is such that for 100 units of the formula R ₂ SiO 0 to 10 mol units of the formula RSiO _3/2 , 0 to 1.5 mol units R ₃ SiO _{1 2} and 0 to 3 mol Units of SiO _{2 4} are present. R can either be a monovalent saturated hydrocarbon radical with 1 to 18 C Atoms, the phenyl radical or the alkoxy radical or a group which can be attacked by free radicals such as the vinyl or the mercaptopropyl radical. It is preferred that at least 80% of all R groups are methyl groups; combinations of methyl and ethyl or phenyl radicals are particularly preferred.

Preferred silicone rubbers contain built-in units of groups which can be attacked by free radicals, in particular vinyl, allyl, halogen, mercapto groups, preferably in amounts of 2-10 mol%, based on all radicals R. They can be prepared, for example, as in EP-A-0 260 558 described.

In some cases it may be appropriate to use an emulsion polymer A made from uncrosslinked polymer. All of the monomers mentioned above can be used as monomers for the production of these polymers. Preferred uncrosslinked emulsion polymers A are e.g. Homopolymers and copolymers of acrylic acid esters, especially n-butyl and ethyl hexyl acrylate, and homopolymers and copolymers of ethylene, propylene, butylene, isobutylene and poly (organosiloxanes), all with the proviso that they are linear or may be branched.

Core / shell - emulsion polymer A

The emulsion polymer A can also be a multi-stage polymer (so-called "core / shell structure", "core-shell morphology"). For example, a rubber-elastic core (T. <0 ° C) can be encased by a "hard" shell (polymers with T _g > 0 ° C) or vice versa.

In a particularly preferred embodiment of the invention, component A is a graft copolymer. The graft copolymers A of the molding compositions according to the invention have an average particle size d ₅₀ of 50-1000 nm, preferably 50-600 nm and particularly preferably 50-400 nm. These particle sizes can be achieved if, as the graft base AI of this component A, particle sizes of 50- 350 nm, preferably from 50 to 300 nm and particularly preferably from 50 to 250 nm used.

The graft copolymer A is generally one or more stages, i.e. a polymer composed of a core and one or more shells. The polymer consists of a basic stage (graft core) Al and one or - preferably - several stages A2 grafted thereon, the so-called graft stages or graft shells.

One or more graft shells can be applied to the rubber particles by simple grafting or multiple step-wise grafting, each graft sheath having a different composition. In addition to the grafting monomers, polyfunctional crosslinking or reactive group-containing monomers can also be grafted on (see e.g. EP-A-0 230 282, DE-A-36 01 419, EP-A-0 269 861).

In a preferred embodiment, component A consists of a multi-stage graft copolymer, the graft stages being generally made from resin-forming monomers and having a glass transition temperature T_ above 30 ° C., preferably above 50 ° C. The multi-stage structure serves among other things to achieve a (partial) compatibility of the rubber particles A with the thermoplastic B.

Graft copolymers A are prepared, for example, by grafting at least one of the monomers A2 listed below onto at least one of the graft bases or graft bases listed above. core materials AI. All polymers described above under emulsion polymers A are suitable as graft bases AI of the molding compositions according to the invention.

According to one embodiment of the invention, the graft base AI is composed of 15-99% by weight of acrylate rubber, 0.1-5% by weight of crosslinking agent and 0-49.9% by weight of one of the further monomers or rubbers indicated.

Suitable monomers for forming the graft A2 can be selected, for example, from the monomers listed below and their mixtures:

Vinylaromatic monomers, such as styrene and its substituted derivatives, such as α-methylstyrene, p-methylstyrene, 3,4-dimethylstyrene, p-tert-butylstyrene, o- and p-divinylbenzene and p-methyl-α-methylstyrene or C _j - Cg-alkyl (me_h) acrylates such as methyl methacrylate, ethyl methacrylate, methyl acrylate, ethyl acrylate, n-butyl acrylate, s-butyl acrylate; styrene, α-methylstyrene, methyl methacrylate, in particular styrene and / or α-methylstyrene, and ethylenically unsaturated monomers, such as acrylic and methacrylic compounds, such as, for example, acrylonitrile, methacrylonitrile, acrylic and methacrylic acid, methyl acrylate, ethyl acrylate, n- and isopropyl acrylate, are preferred, n- and isobutyl, tert-butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n- and isopropyl, n- and isobutyl, tert-butyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, maleic anhydride and its derivatives, such as maleic acid esters, maleic acid diesters, and maleimides, for example, Al yl and aryl maleimides, such as methyl or phenyl maleimide. Acrylonitrile and methacrylonitrile, in particular acrylonitrile, are preferred.

Furthermore, as (co) monomers styrene, vinyl, acrylic or meth acrylic compounds (eg, styrene optionally substituted with C _j ^ alkyl, halo, halomethyl _radicals;. vinylnaphthalene, vinyl carbazole, vinyl ethers with

Vinylimidazole, 3- (4-) vinylpyridine, dimethylaminoethyl (meth) acrylate, p-dimethylaminostyrene, acrylonitrile, methacrylonitrile, acrylic acid, methacrylic acid, butyl acrylate, ethylhexyl acrylate and methyl methacrylate as well as fumaric acid, maleic acid, itaconic acid or their anhydrides or amides, nitrides, amides with 1 to 22 carbon atoms, preferably alcohols containing 1 to 10 carbon atoms) can be used.

According to one embodiment of the invention, component A comprises 50-90% by weight of the above-described graft base AI and 10-50% by weight of the above-described graft base A2, based on the total weight of component A.

According to one embodiment of the invention, crosslinked acrylic acid ester polymers with a glass transition temperature below 0 ° C. serve as the graft base. The crosslinked acrylic ester polymers should preferably have a glass transition temperature below -20 ° C., in particular below -30 ° C.

In a preferred embodiment, the graft A2 consists of at least one graft shell and the outermost graft shell thereof has a glass transition temperature of more than 30 ° C, a polymer formed from the monomers of the graft A2 would have a glass transition temperature of more than 80 ° C.

With regard to the measurement of the glass transition temperature and the average particle size and the Q values, what has been said for the emulsion polymers A applies to the graft copolymers A. The graft copolymers A can also be prepared by grafting pre-formed polymers onto suitable graft homopolymers. Examples of this are the reaction products of copolymers containing maleic anhydride or acid groups with base-containing rubbers.

Suitable production processes for graft copolymers A are emulsion, solution, bulk or suspension polymerization. The graft copolymers A are preferably prepared by radical emulsion polymerization, in particular in the presence of latices of component AI at temperatures from 20 ° C. to 90 ° C. using water-soluble or oil-soluble initiators such as peroxodisulfate or benzyl peroxide, or with the aid of redox mitiators. Redox mitiators are also suitable for polymerization below 20 ° C.

Suitable emulsion polymerization processes are described in DE-A-28 26 925, 31 49 358 and in DE-C-12 60 135.

The graft casings are preferably constructed in the emulsion polymerization process, as described in DE-A-32 27 555, 31 49 357, 31 49 358, 34 14 118. The defined particle sizes of 50-1000 nm according to the invention are preferably carried out after the processes that are described in DE-C-12 60 135 and DE-A-28 26 925, or Applied Polymer Science, Volume 9 (1965), page 2929. The use of polymers with different particle sizes is known, for example, from DE-A-28 26 925 and US 5,196,480.

According to the process described in DE-C-12 60 135, the graft base A1 is first prepared by adding the acrylic acid ester (s) used according to one embodiment of the invention and the multifunctional crosslinking monomers, optionally together with the further comonomers, in aqueous emulsion in a manner known per se, at temperatures between 20 and 100 ° C., preferably between 50 and 80 ° C. The usual emulsifiers, such as alkali salts of alkyl or alkylarylsulfonic acids, alkyl sulfates, fatty alcohol sulfonates, salts of higher fatty acids with 10 to 30 carbon atoms or resin soaps can be used. The sodium salts of alkyl sulfonates or fatty acids having 10 to 18 carbon atoms are preferably used. According to one embodiment, the emulsifiers are used in amounts of 0.5-5% by weight, in particular 1-2% by weight, based on the monomers used in the preparation of the graft base AI. In general, the weight ratio of water to monomers is from 2: 1 to 0.7: 1. The usual persulfates, such as potassium persulfate, are used in particular as polymerization initiators. However, redox systems can also be used. The initiators are generally used in amounts of 0.1-1% by weight, based on the monomers used in the preparation of the graft base AI. The usual buffer substances, by means of which pH values of preferably 6-9 are set, such as sodium bicarbonate and sodium pyrophosphate, and 0-3% by weight of a molecular weight regulator, such as mercaptans, terpinols or dimeric α-methylstyrene, can be used as further polymerization auxiliaries , are used in the polymerization.

The precise polymerization conditions, in particular the type, dosage, and amount of the emulsifier, be determined within the above ranges in detail so that the resulting latex of the crosslinked Acrylsäuree- obtained sterpolymerisats a d ₅ o value in the range of about 50 - nm 1000, preferably 50 - 150 nm, particularly preferably in the range of 80 - 100 nm. The particle size distribution of the latex should preferably be narrow. The quotient

should be <0.5, preferably <0.35.

To produce the graft polymer A, a monomer mixture of styrene and acrylonitrile is then polymerized in a next step in the presence of the latex of the crosslinked acrylic ester polymer thus obtained, the weight ratio of styrene to acrylonitrile in the monomer mixture according to one embodiment of the invention in the range from 100: 0 to 40:60, preferably in the range from 65: 35 to 85: 15. It is advantageous to carry out this graft copolymerization of styrene and acrylonitrile on the crosslinked polyacrylic ester polymer used as the graft base again in an aqueous emulsion under the customary conditions described above. The graft copolymerization can expediently take place in the same system as the emulsion polymerization for the preparation of the graft base A1, it being possible, if necessary, to add further emulsifier and initiator. The monomer mixture of styrene and acrylonitrile to be grafted on according to one embodiment of the invention can be added to the reaction mixture all at once, batchwise in several stages or preferably continuously during the polymerization. The graft copolymerization of the mixture of styrene and acrylonitrile in the presence of the crosslinking acrylic ester polymer is carried out in such a way that a degree of grafting of 1-99% by weight, preferably 20-45% by weight, in particular 35-45% by weight, based on the Total weight of component A, resulting in graft copolymer A. Since the graft yield in the graft copolymerization is not 100%, a somewhat larger amount of the monomer mixture of styrene and acrylonitrile must be used in the graft copolymerization than corresponds to the desired degree of grafting. The control of the graft yield at The person skilled in the art is familiar with graft copolymerization and thus the degree of grafting of the finished graft copolymer A and can be carried out, for example, by the metering rate of the monomers or by adding a regulator (Chauvel, Daniel, ACS Polymer Preprints 15 (1974), page 329 ff.). The emulsion graft copolymerization generally gives rise to about 5 to 15% by weight, based on the graft copolymer, of free, non-grafted styrene / acrylonitrile copolymer. The proportion of the graft copolymer A in the polymerization product obtained in the graft copolymerization is determined by the method given above.

In the production of the graft copolymers A by the emulsion process, in addition to the given process engineering advantages, reproducible particle size changes are also possible, for example by at least partially agglomeration of the particles into larger particles. This means that polymers with different particle sizes can also be present in the graft copolymers A.

Component A, in particular, consisting of the graft base and graft shell (s) can be optimally adapted for the particular application, in particular with regard to the particle size.

The graft copolymers A generally contain 1-99% by weight, preferably 55-80 and particularly preferably 55-65% by weight of graft base AI and 1-99% by weight, preferably 20-45, particularly preferably 35-45% by weight .-% of the graft A2, each based on the entire graft copolymer. COMPONENT B

Component B is an amorphous or partially crystalline polymer.

Component B is preferably a copolymer of

bl: 40-100% by weight, preferably 60-70% by weight, units of a vinylaromatic monomer, preferably styrene, a substituted styrene or a (meth) acrylic acid ester or mixtures thereof, in particular styrene and / or α-methylstyrene as component Bl,

b2: up to 60% by weight, preferably 30-40% by weight, of units of an ethylenically unsaturated monomer, preferably acrylonitrile or methacrylonitrile, in particular acrylonitrile as component B2.

According to a preferred embodiment of the invention, the viscosity number of component B is 50-90, preferably 60-80.

The amorphous or partially crystalline polymers of component B of the molding composition used according to the invention for producing the housing according to the invention are preferably composed of at least one polymer from partially crystalline polyamides, partially aromatic copolyamides, polyolefins, ionomers, polyesters, polyether ketones, polyoxyalkylenes, polyarylene sulfides and polymers from vinyl aromatic monomers and / or selected ethylenically unsaturated monomers. Polymer mixtures can also be used.

As component B of the molding composition used according to the invention for producing the housing according to the invention are partially crystalline, preferably linear polyamides such as polyamide-6, polyamide-6,6, polyamide-4,6, polyamide-6,12 and Semi-crystalline copolyamides based on these components are suitable. Furthermore, partially crystalline polyamides can be used, the acid component of which consists wholly or partly of adipic acid and / or terephthalic acid and / or isophthalic acid and / or suberic acid and / or sebacic acid and / or acetic acid and / or dodecanedicarboxylic acid and / or a cyclohexanedicarboxylic acid, and their Diamine component wholly or partly in particular consists of m- and / or p-xylylenediamine and / or hexamethylenediamine and / or 2,2,4- and / or 2,4,4-trimethylhexamethylenediamine and / or isophoronediamine, and their compositions in principle from State of the art are known (cf. Encyclopedia of Polymers, Vol. 11, p. 315 ff.).

Examples of polymers which are furthermore suitable as component B of the molding compositions used according to the invention for producing the housings according to the invention are partially crystalline polyolefins, preferably homo- and copolymers of olefins such as ethylene, propylene, butene-1, pentene-1, hexene-1 and heptene-1 , 3-methylbutene-1, 4-methylbutene-1, 4-methylpentene-1 and octene-1. Suitable polyolefins are polyethylene, polypropylene, polybutene-1 or poly-4-methylpentene-1. In general, a distinction is made between polyethylene (PE) and high-density PE (HDPE), low-density PE (LDPE) and linear-low-density PE (LLDPE).

In another embodiment of the invention, component B is an ionomer. These are generally polyolefins as described above, in particular polyethylene, which contain monomers co-condensed with acid groups, for example acrylic acid, methacrylic acid and optionally other copolymerizable monomers. The acid groups are generally converted into ionic, optionally ionically crosslinked polyolefins with the aid of metal ions such as Na ⁺ , Ca ²⁺ , Mg ²⁺ and Al ³⁺ , but these can still be processed thermoplastically (see, for example, US Pat. No. 3,264,272; 3,404,134; 3,355,319 ; 4,321,337). However, it is not absolutely necessary to convert polyolefins containing groups by means of metal ions. Component B according to the invention is also suitable for polyolefins containing free acid groups, which then generally have a rubber-like character and in some cases also contain further copolymerizable monomers, for example (meth) acrylates.

In addition, component B can also be polyester, preferably aromatic-aliphatic polyester. Examples are polyalkylene terephthalate, e.g. based on ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol and 1,4-bis-hydroxymethyl-cyclohexane, as well as polyalkylene naphthalates.

Aromatic polyether ketones, such as those e.g. are described in GB 1 078 234, US 4,010,147, EP-A-0 135 938, EP-A-0 292 211, EP-A-0 275 035, EP-A-0 270 998, EP-A-0 165 406, and in the publication by CK Sham et. al., Polymer 29/6, 1016-1020 (1988).

Furthermore, component B of the molding compositions used according to the invention for producing the housing according to the invention can be polyoxyalkylenes, e.g. Polyoxymethylene, and Oxymethylenpoiymerisate are used.

Other suitable components B are the polyarylene sulfides, in particular the polyphenylene sulfide.

According to one embodiment of the invention, it is composed of 50-99% by weight of vinyl aromatic monomers and 1-50% by weight of at least one of the other specified monomers. Component B is preferably an amorphous polymer, as described above as graft A2. According to one embodiment of the invention, a copolymer of styrene and / or α-methylstyrene with acrylonitrile is used as component B. The acrylonitrile content in these copolymers of component B is 0-60% by weight, preferably 30-40% by weight, based on the total weight of component B. Component B also includes those formed in the graft copolymerization to produce component A. free, non-grafted styrene / acrylonitrile copolymers. Depending on the conditions chosen for the production of the graft copolymer A in the graft copolymerization, it may be possible that a sufficient proportion of component B has already been formed in the graft copolymerization. In general, however, it will be necessary to mix the products obtained in the graft copolymerization with additional, separately prepared component B.

This additional, separately produced component B can preferably be a styrene / acrylonitrile copolymer, an α-methylstyrene / acrylonitrile copolymer or an α-methylstyrene / styrene / acrylonitrile terpolymer. These copolymers can be used individually or as a mixture for component B, so that the additional, separately produced component B of the molding compositions used according to the invention is, for example, a mixture of a styrene / acrylonitrile copolymer and an α-methylstyrene / Acrylonitrile copolymer can act. In the event that component B of the molding compositions used according to the invention consists of a mixture of a styrene / acrylonitrile copolymer and an α-methylstyrene / acrylonitrile copolymer, the acrylonitrile content of the two copolymers should preferably not be more than 10% by weight. %, preferably not more than 5% by weight, based on the total weight of the copolymer, differ from one another. Component B of the molding compositions used according to the invention can, however, only consist of consist of a single styrene / acrylonitrile copolymer if the same monomer mixture of styrene and acrylonitrile is used in the graft copolymerizations for the production of component A and in the production of the additional, separately produced component B.

The additional, separately manufactured component B can be obtained by the conventional methods. Thus, according to one embodiment of the invention, the copolymerization of the styrene and / or α-methylstyrene with the acrylonitrile can be carried out in bulk, solution, suspension or aqueous emulsion. Component B preferably has a viscosity number of 40 to 100, preferably 50 to 90, in particular 60 to 80. The viscosity number is determined in accordance with DIN 53 726, 0.5 g of material being dissolved in 100 ml of dimethylformamide.

COMPONENT C

Suitable polycarbonates C are known per se. They preferably have a molecular weight (weight average M _w , determined by means of gel permeation chromatography in tetrahydrofuran against polystyrene standards) in the range from 10,000 to 60,000 g / mol. They can be obtained, for example, in accordance with the processes of DE-B-1 300 266 by interfacial polycondensation or in accordance with the process of DE-A-1 495 730 by reacting diphenyl carbonate with bisphenols. Preferred bisphenol is 2,2-di (4-hydroxypheny propane, generally - as also hereinafter - referred to as bisphenol A.

Instead of bisphenol A, other aromatic dihydroxy compounds can also be used, in particular 2,2-di (4-hydroxyphenyl) pentane, 2,6-dihydroxynaphthalene, 4,4'-dilydydroxydiphenylsulfane, 4,4'-dilrydroxydiphenyl ether, 4,4'-dihydroxydiphenyl sulfite, 4,4'-D_hydroxydiphenylme_han, l, l-di- (4-hydroxyphenyl) ethane, 4,4-dihydroxydiphenyl or dihydroxydiphenylcycloalkanes, preferably dihydroxydiphenylcyclohexanes or dihydroxylcyclopentanes, in particular 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane and mixtures of the aforementioned dihydroxy compounds.

Particularly preferred polycarbonates are those based on bisphenol A or bisphenol A together with up to 80 mol% of the aromatic dihydroxy compounds mentioned above.

Copolycarbonates according to US Pat. No. 3,737,409 can also be used; Of particular interest are copolycarbonates based on bisphenol A and di (3,5-dimethyl-dihydroxyphenyl) sulfone, which are characterized by high heat resistance. It is also possible to use mixtures of different polycarbonates.

According to the invention, the average molecular weights (weight average M _w , determined by means of gel permeation chromatography in tetrahydrofuran against polystyrene standards) of the polycarbonates C are in the range from 10,000 to 64,000 g / mol. They are preferably in the range from 15,000 to 63,000, in particular in the range from 15,000 to 60,000 g / mol. This means that the polycarbonates C have relative solution viscosities in the range from 1.1 to 1.3, measured in 0.5% strength by weight solution in dichloromethane at 25 ° C., preferably from 1.15 to 1.33. The relative solution viscosities of the polycarbonates used preferably differ by no more than 0.05, in particular no more than 0.04.

The polycarbonates C can be used both as regrind and in granular form. As component C, they are in amounts of 1 - 98% by weight, preferably from 50 to 95% by weight, in particular from 60 to 90% by weight, in each case based on the total molding composition.

The addition of polycarbonates leads, inter alia, to higher thermal stability and improved crack resistance of the molding compositions used for producing the housing according to the invention.

Components A, B, C and optionally D can be mixed in any desired manner by all known methods. If components A and B have been prepared, for example, by emulsion polymerization, it is possible to mix the polymer dispersions obtained with one another, to precipitate the polymers together thereupon and to work up the polymer mixture. However, components A, B and C are preferably mixed by extruding, kneading or rolling the components together, the components having, if necessary, been isolated beforehand from the solution or aqueous dispersion obtained in the polymerization. The products of the graft copolymerization (component A) obtained in aqueous dispersion can also only be partially dewatered and mixed as a moist crumb with component B, the graft copolymers then being completely dried during the mixing.

In a preferred embodiment, the molding compositions used according to the invention for producing the housings according to the invention contain, in addition to components A, B and C, the additional component D and, if appropriate, further additives, as described below. COMPONENT D

As component D, the preferred thermoplastic molding compositions used according to the invention for producing the housings according to the invention contain 0 to 50% by weight, preferably 0 to 40% by weight, in particular 0 to 30% by weight of fibrous or particulate fillers or mixtures thereof , each based on the entire molding compound. These are preferably commercially available products.

Reinforcing agents such as carbon fibers and glass fibers are usually used in amounts of 5-50% by weight, based on the total molding composition.

The glass fibers used can be made of E, A or C glass and are preferably equipped with a size and an adhesion promoter. Their diameter is generally between 6 and 20 μm. Both continuous fibers (rovings) and chopped glass fibers (staples) with a length of 1-10 μm, preferably 3-6 μm, can be used.

Furthermore, fillers or reinforcing materials such as glass balls, mineral fibers, whiskers, aluminum oxide fibers, mica, quartz powder and wollastonite can be added.

In addition, metal flakes (for example aluminum flakes from Transmet Corp.), metal powder, metal fibers, metal-coated fillers, for example nickel-coated glass fibers and other additives which shield electromagnetic waves, can be admixed with the molding compositions used according to the invention for producing the housing according to the invention. Aluminum flakes (K 102 from Transmet) are particularly suitable for EMI purposes (glectro-biagnetic interference). The masses can also use additional carbon fibers, carbon black, in particular conductivity carbon black, or nickel-coated carbon fibers can be mixed.

The molding compositions used according to the invention for the production of the housings according to the invention can furthermore contain further additives which are typical and customary for polycarbonates, SAN polymers and graft copolymers or mixtures thereof. Examples of such additives are: dyes, pigments, colorants, antistatic agents, antioxidants, stabilizers for improving the thermostability, for increasing the light stability, for increasing the hydrolysis resistance and the chemical resistance, agents against heat decomposition and in particular the lubricants / lubricants, which are useful for the production of moldings or moldings. These additional additives can be metered in at any stage of the production process, but preferably at an early point in time, in order to take advantage of the stabilizing effects (or other special effects) of the additive at an early stage. Heat stabilizers or oxidation retardants are usually metal halides (chlorides, bromides, iodides) which are derived from metals of group I of the periodic table of the elements (such as Li, Na, K, Cu).

Suitable stabilizers are the usual hindered phenols, but also vitamin E or compounds with an analog structure. HALS stabilizers (hindered amine light stabilizers), benzophenones, resorcinols, salicylates, benzotriazoles and other compounds are also suitable (for example Irganox *, Tinuvin *, such as Tinuvin * 770 (HALS absorber, bis (2,2,6, 6-tetrameU_yl- 4-piperidyl) sebazate) or Tinuvin * P (UV absorber - (2H-benzotriazol-2-yl) -4-methylphenol), topanol). These are usually used in amounts of up to 2% by weight (based on the total mixture). Suitable lubricants and mold release agents are stearic acids, stearyl alcohol, stearic acid esters or generally higher fatty acids, their derivatives and corresponding fatty acid mixtures with 12-30 carbon atoms. The amounts of these additives are in the range of 0.05-1% by weight.

Silicone oils, oligomeric isobutylene or similar substances are also suitable as additives, the usual amounts being 0.05-5% by weight. Pigments, dyes, color brighteners such as ultramarine blue, phthalocyanines, titanium dioxide, cadmium sulfides, derivatives of perylene tetracarboxylic acid can also be used.

Processing aids and stabilizers such as UV stabilizers, lubricants and antistatic agents are usually used in amounts of 0.01 - 5% by weight, based on the total molding compound.

The thermoplastic molding compositions used for producing the housings according to the invention can be produced by methods known per se by mixing the components. It can be advantageous to premix individual components. Mixing the components in solution and removing the solvents is also possible.

Suitable organic solvents are, for example, chlorobenzene, mixtures of chlorobenzene and methylene chloride or mixtures of chlorobenzene or aromatic hydrocarbons, e.g. Toluene.

The solvent mixtures can be evaporated, for example, in evaporation extruders.

The dry components, for example, can be mixed by all known methods. However, the mixing is preferably carried out by extruding, kneading or rolling the components together, preferably at temperatures of 180-400 ° C., the components having, if necessary, been isolated beforehand from the solution obtained in the polymerization or from the aqueous dispersion.

The components can be metered in together or separately one after the other.

According to one embodiment of the invention, the housing and fastening parts according to the invention can be produced from the thermoplastic molding compositions used according to the known methods of thermoplastic processing. In particular, production can be carried out by thermoforming, extrusion, injection molding, calendering, blow molding, pressing, pressing sintering, deep drawing or sintering, preferably by injection molding.

The molding compositions used according to the invention are used for the production of housings for electrical transformers containing small transformers.

Such electrical devices can be devices, for example, in which other electrical assemblies or mechanical assemblies are accommodated in addition to small transformers. Examples are computers and consumer electronics from the audio or video sector. According to one embodiment of the invention, the housing for power supplies or chargers for battery imitators are used. According to one embodiment of the invention, the housings essentially contain only one or more small transformers. Otherwise, the housings only contain smaller electronic assemblies, for example diodes or rectifiers. According to one embodiment of the invention, small transformers are transformers which serve for low-voltage power supply and which are the usual mains voltage Reduce voltage to low voltage. Small transformers of this type are used, for example, for lighting (halogen spotlights), as well as for electrically operated toys, for example model trains or car racing tracks. Power supplies that are used separately from electrical devices and consist of a plug-in transformer that is plugged directly into a conventional socket and a connecting cable for the electrical device are widespread.

The housings of the electrical devices containing small transformers or these devices can be used indoors inside as well as outdoors outside of buildings.

The housings can be installed in a stationary manner or can belong to a mobile (portable) device. In addition, the housings can be part of a group of several housings.

In particular, the housings according to the invention are used where they are exposed to moist or warm surroundings or UV light. Due to the heat development in transformers, these are usually exposed to permanent thermal stress.

The housings can have any shape, provided that this allows the inclusion of small transformers. Usually, the housings, especially on power supplies or chargers for accumulators, have only small gaps between the wall and the small transformer, so that they are in close thermal contact with the small transformer. Suitable designs are known to the person skilled in the art.

In addition to the use of the thermoplastic molding compositions according to the invention for producing the housing, the invention also relates to the housing itself and power supplies, which consist essentially of a housing and at least one small transformer.

The molding compositions according to the invention have high color stability and aging resistance, in particular with continued thermal stress.

The housings are very heat-resistant and resistant to sustained heat. By adding the polycarbonate as component C, the heat resistance and impact resistance of the housing is very good. These housings also have a balanced ratio of toughness and rigidity and good dimensional stability, as well as excellent resistance to heat aging and high resistance to yellowing under thermal stress and exposure to UV radiation.

In addition, the housings according to the invention meet the fire protection regulation according to UL94 in the corresponding wall thicknesses. A UL-VO rating of 1.6 mm and 0.8 mm wall thickness is achieved.

Housings made of molding compounds containing components A and B have excellent surface properties that can be obtained without further surface treatment. The appearance of the finished surface of the housing can be modified by suitable modification of the rubber morphology, for example in order to achieve glossy or matt surface designs. When exposed to weather and UV radiation, the housings show a very slight graying or yellowing effect, so that the surface properties are retained. Further advantageous properties of the housing are the high weather stability, good thermal resistance, high yellowing resistance under UV radiation and thermal stress, good stress crack resistance, especially when exposed to chemicals, and good anti-electrostatic behavior. In addition, they have high color stability, for example due to their excellent resistance to yellowing and embrittlement. The housings according to the invention made of the thermoplastic molding compositions used according to the invention do not show any significant loss of toughness or impact strength at low temperatures or after prolonged exposure to heat, which loss is retained even when exposed to UV rays. The tensile strength is also retained. They also show a balanced relationship between rigidity and toughness.

It is possible to recycle thermoplastic molding compositions already used to manufacture the housings according to the present invention. Due to the high color stability, weather resistance and aging resistance, the molding compositions used according to the invention are very suitable for reuse. The proportion of reused (recycled) molding compound can be high. When using, for example, 30% by weight of molding compound already used, which was mixed in the ground form with the molding compounds used according to the invention, the relevant material properties such as flowability, Vicat softening temperature and impact resistance of the molding compounds and the housing according to the invention produced therefrom did not change significantly. Similar results were obtained when the weather resistance was examined. The impact strength was constant for a long time even when using recycled thermoplastic molding compositions, see Lindenschmidt, Rupp-mich, Hoven-Nievelstein, International Body Engineering Conference, September 21-23, 1993, Detroit, Michigan, USA, Interior and Exterior Systems, Pages 61 to 64. The yellowing resistance was also retained.

The invention is illustrated by the following examples. EXAMPLES

example 1

Production of small-part graft copolymer (A)

(al) 16 parts of butyl acrylate and 0.4 part of tricyclodecenyl acrylate were in 150 parts of water with the addition of part of the sodium salt of a C ₁₂ - to C _lg -lr ^ raffinsulfonic acid, 0.3 part of potassium persulfate, 0.3 part of sodium hydrogen carbonate and 0.15 part of sodium pyrophosphate heated to 60 ° C with stirring. A mixture of 82 parts of butyl acrylate and 1.6 parts of tricyclodecenyl acrylate was added within 3 hours 10 minutes after the start of the polymerization reaction. After the monomer had been added, the mixture was left to react for an hour. The latex of the crosslinked butyl acrylate polymer obtained had a solids content of 40% by weight. The mean particle size (weight average) was found to be 76 nm. The particle size distribution was narrow (quotient Q = 0.29).

(a2) 150 parts of the polybutyl acrylate latex obtained according to (a1) were mixed with 40 parts of a mixture of styrene and acrylonitrile (weight ratio 75:25) and 60 parts of water and with stirring after the addition of a further 0.03 part of potassium persulfate and 0. 05 parts of lauroyl peroxide heated to 65 ° C for 4 hours. After the end of the graft copolymerization, the polymerization product was precipitated from the dispersion using calcium chloride solution at 95 ° C., washed with water and dried in a warm air stream. The degree of grafting of the graft copolymer was 35%. Example 2

Production of large-scale graft copolymer (A)

(al) On the one hand, after adding 50 parts of water and 0.1 part of potassium persulfate, a mixture of 49 parts of butyl acrylate and 1 Part of tricyclodecenyl acrylate and on the other hand a solution of 0.5 part of the sodium salt of a C ₁₂ - to C ₁ -parafransulfonic acid in 25 parts

Let water run in at 60 ° C. After the end of the feed, polymerization was continued for 2 hours. The latex of the crosslinked butyl acrylate polymer obtained had a solids content of 40%. The average particle size (weight average of the latex) was found to be 288 nm. The particle size distribution was narrow (Q = 0.1).

(a2) 150 parts of this latex were mixed with 40 parts of a mixture

Styrene and acrylonitrile (ratio 75:25) and 110 parts of water mixed and stirring for 4 hours after adding a further 0.03 parts of potassium persulfate and 0.05 parts of lauroyl peroxide

Heated to 65 ° C. The polymerization product obtained in the graft copolymerization was then precipitated from the dispersion using a calcium chloride solution at 95 ° C., separated off, washed with water and dried in a warm air stream. The degree of grafting of the graft copolymer was determined to be 27%. Example 3

Production of large-scale graft copolymer (A)

(al) 16 parts of butyl acrylate and 0.4 part of tricyclodecenyl acrylate were in 150 parts of water with the addition of 0.5 part of the sodium salt of a C ₁₂ - to C _j g paraffin sulfonic acid, 0.3 part of potassium persulfate, 0.3 part of sodium hydrogen carbonate and 0 , 15 parts of sodium pyrophosphate are heated to 60 ° C. with stirring. A mixture of 82 parts of butyl acrylate and 1.6 parts of tricyclodecenyl acrylate was added within 3 hours 10 minutes after the start of the polymerization reaction. After the monomer addition had ended, the mixture was left to react for an hour. The latex of the crosslinked butyl acrylate polymer obtained had a solids content of 40% by weight. The average particle size (weight average) was found to be 216 nm. The particle size distribution was narrow (Q = 0.29).

(a2) 150 parts of the polybutyl acrylate latex obtained according to (a1) were mixed with 20 parts of styrene and 60 parts of water and heated with stirring after the addition of a further 0.03 part of potassium persulfate and 0.05 part of lauroyl peroxide to 65 ° C. for 3 hours. After the first stage of the graft copolymerization had ended, the graft copolymer had a degree of grafting of 17%. This graft copolymer dispersion was polymerized without further additives with 20 parts of a mixture of styrene and acrylonitrile (ratio 75:25) for a further 3 hours. After the end of the graft copolymerization, the product was precipitated from the dispersion using calcium chloride solution at 95 ° C., washed with water and dried in a warm air stream. The degree of grafting of the graft copolymer was 35%, and the average particle size of the latex particles was found to be 238 nm.

Example 4

Production of large-scale graft copolymer (A)

(al) On the one hand, a mixture of 49 parts of butyl acrylate and 1 part of tricyclodecenyl acrylate were added to a template from 2.5 parts of the latex produced in Example 3 (component A) after the addition of 50 parts of water and 0.1 part of potassium persulfate over the course of 3 hours and on the other hand, a solution of 0.5 part of the sodium salt of a C - to C ₁₈ -parasulfonic acid in 25 parts of water was run in at 60.degree. After the end of the inflow, 2

Postpolymerized for hours. The latex of the crosslinked butyl acrylate polymer obtained had a solids content of 40%. The mean particle size (weight average) of the latex was found to be 410 nm. The particle size distribution was narrow (Q = 0.1).

(a2) 150 parts of the polybutyl acrylate latex obtained according to (a1) were mixed with 20 parts of styrene and 60 parts of water and heated with stirring after the addition of a further 0.03 part of potassium persulfate and 0.05 part of lauroyl peroxide to 65 ° C. for 3 hours. The dispersion obtained in this graft copolymerization was then polymerized with 20 parts of a mixture of styrene and acrylonitrile in a ratio of 75:25 for a further 4 hours. The reaction product was then precipitated from the dispersion using a calcium chloride solution at 95 ° C., separated off, washed with water and dried in a warm air stream. The degree of grafting of the graft Copolymers were found to be 35%, the average particle size of the latex particles was 490 nm.

Example 5

Production of large-scale graft copolymer (A)

(al) 98 parts of butyl acrylate and 2 parts of tricyclodecenyl acrylate were polymerized in 154 parts of water with the addition of 2 parts of dioctylsulfosuccinate sodium (70%) as emulsifier and 0.5 parts of potassium persulfate with stirring at 65 ° C. for 3 hours. An approximately 40% dispersion was obtained. The average particle size of the latex was approximately 100 nm.

A mixture of 49 parts of butyl acrylate, 1 part of tricyclodecenyl acrylate and 0.38 part of the emulsifier was added at 65 ° C. to an initial charge of 2.5 parts of this latex, 400 parts of water and 0.5 part of potassium persulfate within 1 hour. In the course of a further hour, a mixture of 49 parts of butyl acrylate, 1 part of tricyclodecenyl acrylate and 0.76 was added

Allocate emulsifier. After adding 1 part of potassium persulfate in 40 parts of water, a mixture of 196 parts of butyl acrylate, 4 parts of tricyclodecenyl acrylate and 1.52 parts of the emulsifier was finally added dropwise over the course of 2 hours. The polymer mixture was then polymerized at 65 ° C. for a further 2 hours. An approximately 40% dispersion with an average particle diameter of approximately 500 nm was obtained. If only 100 parts were added instead of a total of 300 parts of monomers, a latex with an average particle diameter of about 300 nm was obtained.

(a2) 465 parts of styrene and 200 parts of acrylonitrile were in the presence of 2500 parts of the polymer latex according to (al) with the mean particle size 0.1 or 0.3 or 0.5 μm, 2 parts of potassium sulfate, 1.33 parts of lauryl peroxide and 1005 parts of water polymerized with stirring at 60 ° C. A 40% dispersion was obtained, from which the solid product was precipitated by adding a 0.5% calcium chloride solution, washed with water and dried.

Example 6

Production of copolymer (B)

A monomer mixture of styrene and acrylonitrile was polymerized in solution under customary conditions. The styrene / acrylonitrile copolymer obtained had an acrylonitrile content of 35% by weight, based on the copolymer, and a viscosity number of 80 ml / g.

Example 7

Manufacture of copolymer ß)

A monomer mixture of styrene and acrylonitrile was polymerized in solution under customary conditions. The styrene / acrylonitrile copolymer obtained had an acrylonitrile content of 35% by weight, based on the copolymer, and a viscosity number of 60 ml / g. Example 8

Production of copolymer (B)

A monomer mixture of styrene and acrylonitrile was polymerized in solution under customary conditions. The styrene / acrylonitrile copolymer obtained had an acrylonitrile content of 19% by weight, based on the copolymer, and a viscosity number of 90 ml / g.

Example 9

Production of copolymer (B)

A monomer mixture of styrene and acrylonitrile was polymerized in solution under customary conditions. The styrene / acrylonitrile copolymer obtained had an acrylonitrile content of 19% by weight, based on the copolymer, and a viscosity number of 100 ml / g.

Example 10

Component C

A conventional polycarbonate (PC) was used as component C, which had a viscosity number of 61.5 ml / g, determined in the solvent methylene chloride. For example, Lexan ^R 116 from General Electric Plastics can be used. Comparative Example 1

PPE / HIPS polymer

A polyphenylene ether / high impact polystyrene blend was used as the comparative polymer. For example, it is sold by General Electric under the trade name NoryI ^R SEI.

Comparative Example 2

ABS / PC blend

A polymer blend based on a polybutadiene rubber which was grafted with a styrene-acrylonitrile copolymer was used as the comparative polymer. The rubber was in a styrene-acrylonitrile copolymer matrix. The polycarbonate content was 60% by weight. For example, Bayblen ^® FR 90 from Bayer can be used.

Comparative Example 3

ABS polymer

A polybutadiene rubber which was grafted with a styrene-acrylonitrile copolymer as component (A), which was present in a styrene-acrylonitrile copolymer matrix as component (B), was used as the comparative polymer. The graft rubber content was 29% by weight, based on the total weight of the finished polymer. Comparative Example 2

PVC polymer

A vinyl chloride polymer which had been polymerized in suspension and had a k value of 61 was used as a further molding compound for comparison purposes. The k value was determined as described in DIN 53 726.

Example 11

According to the information in Table 1 below, the stated amounts of the corresponding polymers (A), (B) and (C) or the comparative compositions are mixed in a screw extruder at a temperature of 200 ° C. to 230 ° C. Test specimens were produced from the molding compositions formed in accordance with the conditions specified in DIN standard 16777. All test specimens were colored with 2.0% by weight of TiO ₂ . The UV yellowing was investigated on the molding compositions given in the table below, assessed visually after irradiation with Xenotest 450 behind window glass for a period of 1000 hours.

The modulus of elasticity was determined in accordance with DIN 53 457.

The VST / B (Vicat temperature) was determined according to ISO 306.

The Izod impact strength was determined at 23 ° C according to ISO 180 / 1A.

In addition, the fire behavior was classified according to UL 94 with thicknesses of 1.6 mm and 0.8 mm. Classification VI means a burning time of a maximum of 30 s, total burning time of a maximum of 250 s, no burning drip, the VO classification a burning time of max. 10 s, total burning time of max. 50 s, no burning dripping.

The results are summarized in the table below.

TabeUe 1

The results given in the table show that the molding compositions according to the invention are considerably more resistant than the comparative molding compositions both in the case of UV yellowing and in the case of heat yellowing. With the same modulus of elasticity and VST value and similar notched impact strength, better resistance to fire was found.

This shows that the housings of small transformers according to the invention have high color stability and aging resistance and meet the fire protection regulation according to UL 94. In addition, they do not have the disadvantages of the known housing.

Claims

claims

1. Use of a thermoplastic molding composition other than ABS, comprising, based on the sum of the amounts of components A, B, C and, if appropriate, D, which gives a total of 100% by weight,

c: 1-98% by weight of polycarbonates as component C, and

d: 0 - 50% by weight of fibrous or particulate fillers or mixtures thereof as component D.

for the manufacture of housings for small transformers containing electrical devices.

2. Use according to claim 1, characterized in that component A is a graft copolymer from

al: 1-99% by weight of a particulate graft base AI with a glass transition temperature below 0 ° C,

a2: 1-99% by weight of a graft A2 from the monomers, based on A2, a21: 40-100% by weight of units of a vinyl aromatic monomer as component A21 and

a22: up to 60% by weight of units of an ethylenically unsaturated monomer as component A22,

wherein the graft A2 consists of at least one graft shell and the graft copolymer A has an average particle size of 50-1000 nm.

3. Use according to claim 1, characterized in that the molding composition contains, as a particulate microemulsion polymer A, an acrylate, EP, EPDM or silicone rubber.

4. Use according to claim 2, characterized in that the molding composition contains as a particulate graft base AI an acrylate, EP, EPDM or silicone rubber.

5. Use according to claim 4, characterized in that component AI consists of the monomers

all: 80-99.99% by weight of a C 1-6 alkyl ester of acrylic acid as component All,

al2: 0.01-20% by weight of at least one polyfunctional crosslinking monomer as component A12.

6. Use according to one of claims 1 to 5, characterized in that the particle size distribution of component A is bimodal, 60-90% by weight having an average particle size of 50-200 nm and 10-40% by weight have an average particle size of 50-400 nm, based on the total weight of component A.

7. Use according to one of claims 1 to 6, characterized in that the housing contains essentially only one or more small transformers.

8. Use according to one of claims 1 to 7, characterized in that the electrical devices are power supplies or chargers for accumulators.

9. Housing of small transformers-containing electrical devices made of a thermoplastic molding composition, as defined in one of claims 1 to 6.

10. Power supply, consisting essentially of one or more small transformers and a housing made of a thermoplastic molding material, as defined in one of claims 1 to 6.