Parts based on polyphenylene ethers and rubbers as well as methods for their production

Composite parts of firmly bonded molding materials, comprising a thermoplastic material containing polyphenylene ether, a layer of SBR or SBS rubber or a mixture thereof surrounding the thermoplastic material, if necessary, an intermediate layer comprising a powdered SBR rubber which may contain a filler, and a rubber containing carbon-carbon double bonds covulcanized with the layer of SBR or SBS rubber. The invention also provides a method for producing the composite part comprising treating the thermoplastic material with a solution of a SBR or SBS rubber in an organic solvent or with an aqueous latex of the rubber, if necessary, completely or partially removing the organic solvent or water, if necessary, treating the dried mass with a powdered SBR rubber which may contain a filler, and covulcanizing with a rubber containing carbon-carbon double bonds.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention concerns parts made from thermoplastics which contain 
polyphenylene ether (PPE) and from rubber, as well as methods for their 
production. 
2. Discussion of the Background 
It is known from DE-OS No. 36 02 705 that parts which are supposed to 
demonstrate both high strength and rubber elasticity can be produced by 
covulcanization of thermoplastics which contain PPE and rubbers which 
contain double bonds. The method has the great advantage that a strong 
bond is created between the thermoplastic and the rubber within a very 
short period of time. In this regard, it represents a significant 
improvement as compared with previous methods, which either do not make a 
sufficiently strong bond possible or were significantly more complicated. 
However, the use of this method is limited in view of the rubbers. While an 
SBR rubber, for example, can be covulcanized with the thermoplastic which 
contains PPE without restriction, there are problems with NR rubber, for 
example. According to the theory of DE-OS No. 36 02 705, a bond with an NR 
rubber can only be achieved if a mixture of NR rubber and at least 5% SBR 
rubber is used. This restriction is considered undesirable in practical 
situations. There is also an interest in achieving a bond between 
thermoplastics which contain PPE and pure NR rubber. But even if a mixture 
of 5% SBR rubber and 95% NR rubber is used, the bonding values are clearly 
lower than those of pure SBR rubber. Similar methods are carried out with 
other types of rubber. DE-OS No. 36 02 705 does not offer any indication 
of how one could achieve a strong bond in these problematical cases. In 
general, there is a need for an alternative method, in order to produce 
parts with a strong bond between a thermoplastic which contains PPE and 
any desired rubber. 
SUMMARY OF THE INVENTION 
Accordingly, one object of the present invention is to provide a composite 
part which has both high strength and rubber elasticity. 
Another object of the invention is to provide a composite part containing 
PPE and rubber which can be produced from any rubber having carbon-carbon 
double bonds. 
A further object of the invention is to provide a composite part in which 
the PPE and rubber are held together by a strong bond. 
These and other objects which will become apparent from the following 
specification have been achieved by the composite part of the present 
invention which comprises: 
(A) a thermoplastic material comprising polyphenylene ether, 
(B) a layer of SBR or SBS rubber or a mixture thereof surrounding the 
thermoplastic material; and 
(D) a rubber containing carbon-carbon double bonds, wherein the rubber is 
covulcanized with the layer of SBR or SBS rubber. 
The invention also provides a method of producing the composite parts noted 
above. 
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Surprisingly, parts have now been found which allow a strong bond between a 
thermoplastic which contains PPE and any desired rubber which contains 
double bonds. 
These parts consist of the following components: 
A. a thermoplastic which contains PPE 
B. a layer of an SBR and/or SBS rubber which surrounds the thermoplastic 
C. if necessary, an intermediate layer based on a powdered SBR rubber which 
contains filler, and 
D. any desired rubber which contains double bonds. 
The invention also includes a method for the production of these parts. 
This method consists of treating component A with the solution of 
Component B in an organic solvent or with the aqueous dispersion of 
component B (rubber latex), then completely or partially removing the 
solvent or water, if necessary, and covulcanizing the mass obtained with 
component D, in the presence of a vulcanizer. Preferred rubber solvents 
are aliphatic and cycloaliphatic hydrocarbons, as well as unsaturated, 
non-aromatic and cyclic unsaturated but non-aromatic hydrocarbons. The 
rubber solution can also contain a vulcanizer. It is also possible to 
treat the mass obtained after treatment with the rubber solution with a 
powdered SBR rubber which contains filler, and to covulcanize it with 
component D only after this step. 
The components according to the invention are characterized by the 
following advantages: 
1. As the rubber component, any desired rubber which contains double bonds 
and can be covulcanized with other rubbers can be used. The invention 
therefore has a very broad application. In particular, even those rubbers 
which would not be suitable according to DE-OS No. 36 02 705 are suitable 
for use in the present invention. 
2. The components can be produced in only a few minutes. 
3. Outstanding adhesion between the thermoplastic which contains PPE and 
the rubber is achieved. 
The thermoplastic which contains PPE is either pure PPE itself or a mixture 
of PPE with polyalkylenes, styrene polymerizates, and/or other known 
additives and/or reinforcers. The proportion of PPE in the thermoplastic 
should be at least 50 percent by weight. 
Polyphenylene ethers which can be used are polymers based on substituted 
phenols with the general formula 
##STR1## 
in which R.sub.1 and R.sub.2 are, independently, a methyl group or 
preferably hydrogen. R.sub.3 is either hydrogen and R.sub.4 is a tertiary 
alkyl group with up to 6 carbon atoms, such as a tert-butyl group, for 
example, or R.sub.3 and R.sub.4 each stand for an n-alkyl group with up to 
6 carbon atoms, independent of one another. Preferably, 2,6-dimethylphenol 
is used. Of course, mixtures of the monomeric phenols listed here can also 
be used. Poly(2,6-dimethyl-1,4-phenylene ethers) with a limit viscosity 
between 0.4 and 0.7 ml/g (measured in chloroform at 25.degree. C.) are 
very especially preferred. 
The polyphenylene ethers can be produced, for example, in the presence of 
complex-forming agents, such as copper bromide and morpholine, from 
2,6-dimethylphenol (see DE-OS No. 32 24 692 and OS No. 32 24 691). They 
are usually used in the form of a powder or granulate. 
The polyalkenylenes are produced by ring-opening or ring-expanding 
polymerization of cycloalkenes (see K. J. Ivin, T. Saegusa, "Ring-opening 
Polymerisation, Vol. 1, Elsevier Appl. Sci. Publishers, London, 
particularly pages 121 to 183 (1984)). 
Polyoctenylenes are preferred (See A. Draxler, Kautschuk+Gummi, Kunststoff, 
1981, pages 185 to 190). Polyoctenylenes with different proportions of cis 
and trans double bonds as well as different J values and accordingly 
different molecular weights can be obtained according to methods known 
from the literature. Polyoctenylenes with a viscosity number from 50 to 
350 ml/g, preferably 80 to 160 ml/g, determined in an 0.1% solution in 
toluene, are preferred. 55 to 95%, preferably 75 to 85% of its double 
bonds are present in the trans form. 
Molding materials based on polyphenylene ethers and polyoctenylenes are 
described in the German patent applications Nos. P 34 36 780.2 and P 34 42 
273.0. 
Styrene homopolymerizates and/or impact-resistant styrene polymerizates can 
be used as component (C). The styrene homopolymerizates are produced from 
styrene by radical mass or suspension polymerization, in a known manner. 
Their molecular weights are between 150,000 and 300,000 (see 
Kunststoff-Handbuch, Vol. V, Carl Hanser Verlag Munich, 1969, and Ullmanns 
Encyklopadie der technischen Chemie, 4th ed., Vol. 19, Verlag Chemie, 
Weinheim 1980). 
The impact-resistant styrene polymerizates are obtained in a known manner, 
by polymerizing styrene solutions of poly-cis-butadiene in mass, in 
solution or in aqueous dispersion. With the so-called mixed methods, the 
styrene rubber solution is prepolymerized in mass and polymerization is 
finished in aqueous dispersion (see, for example, U.S. Pat. No. 2,694,692 
and U.S. Pat. No. 2,862,906). 
Adjustment of the particle size of the plastic phase takes place in a known 
manner, in the stage of prepolymerization, before the so-called phase 
reversal. If necessary, the adjustment can also be carried out in the 
presence of the known chain regulators and/or radical initiators. Details, 
such as the connection between the stirring velocity and the size and 
distribution of rubber particles in the resulting impact-resistant 
polymerizate, for example, are known to persons skilled in the art (see 
e.g. Freeguard, Brit. Polym. J., 6, 203 to 228, (1974)). 
The diameter of the particles in the elastomer gel phase is usually below 
10 .mu.m, preferably below 3.5 .mu.m. The average diameter (volume 
average) is in a range between 1 and 5 .mu.m. However, this does not take 
the particles whose diameter is either below 0.5 .mu.m or above 10 .mu.m 
into consideration. 
The average particle size (volume proportion) is determined by measuring 
and averaging the diameters of circles with the same area (equivalent 
diameter) of the particles on thin-layer electron microscopy photographs. 
The distribution curve and from it, the volume average are calculated using 
the volumes of the particles (3rd power of the equivalent diameter). For 
an evaluation, at least 2,000 particles should be used. 
The thermoplastic also contains additional additives, if necessary, such as 
stabilizers, processing agents, reinforcers, foaming agents, metal fibers, 
carbon black, graphite and metal flakes, titanium oxide and zinc sulfide. 
Suitable reinforcers are, for example, carbon fibers, aramide fibers and 
mineral substrates. The proportion of reinforcers in the PPE material can 
be up to 50%, that of flame-proofing agents up to 15% and that of all 
other additives in total up to 5%, relative to the thermoplastic in each 
case. 
Particularly suitable flame-proofing agents are phosphorus compounds, such 
as triphenylphosphine oxide and triphenylphosphate. Also, a conventional 
flame-proofing agent which contains a halogen can be used. Organic 
compounds containing halogen, such as those described in the monography by 
H. Vogel "Flammenfestmachen von Kunststoff", Huthig-Verlag, 1966, on pages 
94 and 106, are possible agents. But the flame-proofing agents can also be 
halogenated polymers, such as halogenated polyphenylene ethers (see DE-OS 
No. 33 34 068) or brominated oligostyrenes or polystyrenes, for example. 
The compounds should contain more than 30 percent by weight halogen. 
In cases where flame-proofing agents containing halogen are used, it is 
recommended that a synergist be used. Compounds of anitmony, boron and tin 
are suitable. These are generally used in amounts of 0.5 to 10 percent by 
weight, with reference to the thermoplastic. 
Suitable stabilizers include organic phosphites, such as didecylphenyl 
phosphite and trilauryl phosphite, sterically hindered phenols as well as 
derivates of tetramethyl piperidine, benzophenone and triazole, for 
example. 
Preferably, the thermoplastic which contains PPE is produced by mixing the 
components in the melted state. At least one component is melted and the 
melt obtained is mixed with the remaining components. Another possibility 
is to melt all the components at the same time and to mix them. 
Preferably, melting temperatures of 250.degree. to 350.degree. C., 
particularly 260.degree. to 300.degree. C., and melting times of 0.3 to 10 
minutes, particularly 0.5 to 3 minutes, are used. 
For melting and mixing, conventional equipment for handling highly viscous 
melts, both in batch and continuous operation, are suitable. Twin-screw 
extruders and coextruders are particularly suitable. 
However, it is also possible to produce the thermoplastic which contains 
PPE in a different manner, e.g. by precipitation from the solution mixture 
of the components, instead of by compounding. Toluene, for example, is a 
suitable common solvent, methanol, for example is a suitable common 
precipitant. The polymer mixture can also be obtained by evaporation of 
the solvent, for example according to the German patent application No. P 
33 37 629.8. 
Component B, which surrounds the thermoplastic A in the form of a thin 
layer, is an SBR or SBS rubber. Here it makes no difference in what way 
the rubber was obtained, i.e. whether it was produced by polymerization in 
emulsion or solution. The SBR rubber is preferably a styrene-butadiene 
copolymer with a statistical structure. The SBS rubber is preferably a 
styrene-butadiene-styrene block copolymer. 
Component C of the component is produced by covulcanization of a powdered 
SBR rubber which contains filler with components B and D. The grain size 
of the powdered rubber is preferably below 1 mm and this rubber can 
therefore be designated as a powder. 
A powdered E-SBR rubber which contains filler is particularly preferred. 
There are a number of different methods for producing powdered rubbers 
which contain filler. Many processes are so time-consuming and 
complicated, however, that they have not gained any practical 
significance. Recently, a method which is described in DE-OS No. 28 22 148 
was used for practical purposes in the industry for the first time. This 
method is characterized by the fact that the rubber component is combined 
with an aqueous filler suspension which contains a water-soluble aluminum 
salt and water glass. The deciding factor is that not only does the 
aqueous filler dispersion have to have a pH value of 3.0 to 3.7, but that 
when this dispersion is combined with the rubber component, an amount of 
mineral acid is added so that the mixture obtained also stays within this 
pH range. 
Component D is any desired rubber which contains double bonds, as long as 
it can be covulcanized with the rubber components B, or, if applicable, C. 
Preferably, such rubbers which cannot be vulcanized alone with a 
thermoplastic which contains PPE, such as NBR rubber or in particular, NR 
rubber are used. 
The rubbers of component D may contain fillers such as carbon black or 
silica gel, for example, stretching agents such as mineral oils, 
vulcanizers such as sulfur, vulcanization accelerators and protectants 
against aging. A particularly suitable processing agent is polyoctenylene 
(A. Draxler, Kautschuk+Gummi, Kunststoffe 1983, p. 1037 to 1043). The 
mineral oils added can be paraffin oils, naphthene oils or aromatic oils. 
The component parts can be extremely varied with regard to their structure: 
examples include rubber nubs on PPE plates, PPE grains in a rubber matrix, 
sandwich structures made of rubber and PPE, PPE fibers in rubber.

In the following, the method according to the invention is described. The 
solvent in which the rubber is dissolved and which is not supposed to 
dissolve the PPE or the thermoplastic which contains PPE, if possible, is 
of particular significance here. One embodiment consists of using a 
solvent in which PPE if very insoluble. Another embodiment consists of 
using a solvent which causes solvent welding of the thermoplastic at its 
surface. In this case, the action time of the solvent on the thermoplastic 
must also be taken into consideration. Because of these requirements, the 
following solvents are particularly suitable. 
aliphatic hydrocarbons with 5 to 15 carbon atoms, such as hexane or 
heptane, for example, 
cycloaliphatic hydrocarbons with 5 to 12 carbon atoms, such as cyclohexane 
or cyclooctane, for example, 
monounsaturated or polyunsaturated, non-aromatic hydrocarbons which can be 
cyclic or acylic and have 5 to 15 carbon atoms, such as 1,3-hexadiene, 
dipentene, limonene, 1,5-cyclooctadiene and 1,3,5-cyclododecatriene. 
In addition, mixtures of the hydrocarbons just mentioned with aromatics 
having 6 to 15 carbon atoms, such as toluene or xylene, for example, as 
well as with aliphatic ethers with up to 10 carbon atoms, such as methyl 
ethers or tert.-butyl ethers, are also suitable. 
The thermoplastic which contains PPE, which can be present in granulate 
form, as a molded part or as a semi-finished product, is first treated 
with a solution of an SBR and/or SBS rubber in the solvents just listed. 
The concentration of the solution is not critical. Usually, it is between 
5 and 20 percent by volume; the concentration of the solution can also be 
so great that it has the consistency of a paste. 
After treatment of the thermoplastic with the rubber solution, the greater 
part of the solvent is usually removed, for example, by evaporation. The 
mass obtained in this way can, if necessary, be treated once more or 
several times more with the rubber solution. Alternatively, the 
thermoplastic can also be treated with an aqueous latex of an SBR and/or 
SBS rubber, and the water can subsequently be removed. 
The mass obtained has a very sticky surface in many cases, after treatment 
with the rubber solution of the latex. It can therefore be advantageous to 
treat the mass with a powdered SBR rubber which contains filler, i.e. to 
powder it, in order to simplify processing. 
Finally, the powdered or unpowdered mass is covulcanized with component D. 
For covulcanization, the usual vulcanizers, which are well known, 
particularly sulfur, should be present. It is preferable if the rubber D 
already contains these agents. 
The optimum covulcanization conditions depend on the rubber mixture 
selected, in particular on its vulcanization system, and the shape of the 
molded part. For details, we refer to the book by W. Hofmann, op. cit., 
page 255 ff. In this book, the mixtures of diene rubbers with stearic 
acid, zinc oxide, fillers (e.g. carbon black), plasticizer oils as well as 
vulcanization activators which are preferred for use are also indicated. 
In particular, vulcanization activators which contain sulfur are used. 
Other features of the invention will become apparent in the course of the 
following descriptions of exemplary embodiments which are given for 
illustration of the invention and are not intended to be limiting thereof. 
EXAMPLES 
Components used: 
1. PPE Material (Component A)--Poly(2,6-dimethyl-1,4-phenylene ether) with 
a J value of 68 ml/g. 
The polyphenylene ether is obtained by oxidative coupling of 
2,6-dimethylphenol, stopping of the reaction and subsequent reaction 
extraction according to DE-OS No. 33 13 864 and OS No. 33 23 777. The 
solvent is removed by evaporation and the melt is extruded in a 
degasification extruder and subsequently granulated. 
2. Natural Rubber (Component D) 
A natural rubber as described in the handbook Encyclopedia of Polymer 
Science and Technology, Interscience Publishers New York, 1970, in Volume 
12, page 191, Table 5, column 1, is used. 
3. Adhesion Agent (Components B and C) 
(3.1) A solution of 10 g of the E-SBR rubber BUNA EM 1502 in 100 cm.sup.3 
hexane. The properties of this type of rubber can be found in the company 
brochure of Chemische Werke Huls, No. 5214, dated October 1983, "BUNA EM 
Rubber Powder with Filler". 
(3.2) A solution or suspension which is obtained by boiling 10 g of a 
dryblend of the following constituents in 100 cm.sup.3 hexane for one 
hour: 
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Parts by 
Weight Material 
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160 rubber powder, consisting of 100 parts 
E-SBR rubber and 60 parts carbon black 
(company brochure of Chemische Werke Huls, 
No. 5214 dated October 1983 "BUNA EM 
Rubber Powder with Filler" 
1 stearic acid 
4 zinc oxide 
1 N--isopropyl-N'--phenyl-p-phenylene diamine 
1 N--(1,3-dimethylbutyl)-N'--phenyl- 
p-phenylene diamine 
2.5 a commercially available protectant 
against aging caused by light and ozone 
(Antilux .RTM. 111). This is a paraffin wax 
with a broad molecular weight distribution 
and a high molecular weight average. 
(Manufacturer: Dahleke, D-2070 Arensburg) 
1.8 sulfur 
1.3 N--cyclohexyl-1-benzothiazole sulfenamide- 
0.8 tetramethyl thiuramide sulfide 
0.5 diphenyl guanidine 
0.3 zinc diethyl dithiocarbamate 
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(3.3) A solution of 10 g Cariflex TR 1102 in 100 cm.sup.3 
cyclododecatriene. This is a styrene-butadienestyrene block copolymer with 
a 30% styrene proportion from Shell AG. 
4. Powder 
A dryblend as in 3.2. 
Production of the Test Samples 
Plates produced by injection molding from the PPE material according to 1. 
are coated with the rubber solution, subjected to a temperature of 
60.degree. C. with fresh air circulation for 15 minutes, if necessary, 
dusted with as much powder as adheres to them, covered with a rubber plate 
and vulcanized under pressure at 141.degree. C. for 30 minutes. In order 
to allow separate attachment of the rubber layer and the PPE layer in the 
jaws of the tension device, a thin aluminum foil was placed between the 
rubber layer and the PPE layer at one end of the plate, before 
vulcanization. 
Determination of Adhesion Strength 
The determination is carried out based on DIN 53 531 and 53 539, with the 
difference that the width of the sample strip is 30 instead of 25 mm and 
that a pulling velocity of 100 instead of 50 mm/min is used. 
Results 
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Adhesion 
Example Adhesion Agent Powder Force (N) 
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A -- -- 12 
1 3.1 -- 133 
2 3.2 -- 165 
3 3.1 4 122 
4 3.2 4 225 
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Obviously, numerous modifications and variations of the present invention 
are possible in light of the above teachings. It is therefore to be 
understood that within the scope of the appended claims, the invention may 
be practiced otherwise than as specifically described herein.