Rubber dispersions II

Stable, free-flowing dispersions in organic liquids of rubbers in the form of discrete particles having an average diameter of from 100 to 3000 nm which contains: PA1 A--as rubber, from 1 to 20% by weight, based on the total dispersion, of a crosslinked diene rubber; B--from 0 to 20% by weight, based on the total dispersion, of water in the form of a water-in-oil emulsion; C--as the continuous organic phase, from 99 to 66% by weight, based on the total dispersion, of (a) C.sub.1 -C.sub.10 alkyl acrylates or alkyl methacrylates, methyl methacrylate, ethyl acrylate or n-hexyl acrylate; or (b) a mixture of from 85 to 50% by weight of styrene or .alpha.-methyl styrene and from 15 to 50% by weight of acrylonitrile, methacrylonitrile or C.sub.1 -C.sub.6 alkyl acrylates or alkyl methacrylates, methyl methacrylate, ethyl acrylate, n-hexyl acrylate; or (c) a mixture of from 85 to 50% by weight of a C.sub.1 -C.sub.10 alkyl acrylate or alkyl methacrylate and from 15 to 50% by weight of acrylonitrile, methacrylonitrile or styrene; up to 60% by weight of a liquid hydrocarbon can be added to and mixed with (a), (b) and (c), and a process for producing said dispersions.

This invention relates to stable, free-flowing dispersions of cross-linked, 
rubbery acrylate polymers in organic liquids and to a process for their 
production. 
Aqueous dispersions (latices) of cross-linked and uncross-linked acrylate 
polymers are known and are generally obtained by emulsion polymerisation. 
However, there are some applications which require stable dispersions of 
discrete microgel particles of rubber in organic liquids. Such stable 
organic rubber dispersions cannot be produced directly by the radical 
polymerisation of appropriate monomers in organic liquids as a continuous 
rubber network or macrogel, rather than discrete rubber particles, 
so-called microgel particles, is formed during polymerisation. 
The present invention is based on the discovery that aqueous emulsions of 
cross-linked, rubber-like diene polymers can be dispersed in certain 
organic liquids so that the diene polymers are dispersed in the form of 
swollen particles and the water of the original emulsion is also dispersed 
in the organic liquid (water-in-oil emulsion). If necessary, the water can 
be removed by selectively breaking the water-in-oil emulsion and 
subsequently separating off the water mechanically, physically or 
chemically. For most applications of the organic rubber dispersions 
according to the present invention, there is no need to remove the water, 
provided it is present in stable dispersion and should not settle out as a 
separate phase. 
The present invention relates to stable, free-flowing dispersions in 
organic liquids of rubbers in the form of discrete particles having an 
average diameter of from 100 to 3000 nm which contain: 
(A)--as rubber, from 1 to 20% by weight, based on the total dispersion, of 
a cross-linked diene rubber; 
(B)--from 0 to 20% by weight, based on the total dispersion, of water in 
the form of a water-in-oil emulsion; 
(C)--as the continuous organic phase, from 99 to 60% by weight, based on 
the total dispersion, of: 
(a) C.sub.1 -C.sub.10 alkylacrylates or alkyl methacrylates, preferably 
methyl methacrylate, ethyl acrylate or n-hexylacrylate; or 
(b) a mixture of from 85 to 50%, by weight, of styrene or .alpha.-methyl 
styrene and from 15 to 50%, by weight, of acrylonitrile, 
methacrylonitrile, or C.sub.1 -C.sub.6 alkyl acrylates or alkyl 
methacrylates, for example methyl methacrylate, ethyl acrylate or n-hexyl 
acrylate; or 
(c) a mixture of from 85 to 50%, by weight, of C.sub.1 -C.sub.10 alkyl 
acrylate or alkyl methacrylate and from 15 to 50%, by weight, of 
acrylonitrile, methacrylonitrile or styrene; 
up to 60%, by weight, of a liquid hydrocarbon may be added to and mixed 
with (a), (b) and (c). 
The present invention also relates to a process for the production of the 
stable, free-flowing rubber dispersion wherein an aqueous emulsion of a 
cross-linked diene rubber having an average rubber particle diameter of 
from 100 to 800 nm (as determined by light scattering) is dispersed with 
stirring in an organic liquid as the dispersion medium of: 
(a) a C.sub.1 -C.sub.10 alkyl acrylate or alkyl methacrylate; or 
(b) a mixture of from 85 to 50%, by weight, of styrene or .alpha.-methyl 
styrene and from 15 to 50%, by weight, of acrylonitrile or 
methacrylonitrile or C.sub.1 -C.sub.6 alkyl acrylate or alkyl 
methacrylate; or 
(c) a mixture of from 85 to 50%, by weight, of a C.sub.1 -C.sub.10 alkyl 
acrylate or alkyl methacrylate and from 15 to 50% by weight, of 
acrylonitrile, methacrylonitrile and/or styrene; 
up to 60% by weight, of a liquid hydrocarbon optionally being added to and 
mixed with (a), (b) and (c), in the presence of from 0.005 to 4% by 
weight, of a dispersant, and wherein a coagulation agent for the latex is 
added with continued stirring in a quantity sufficient to break the 
aqueous latex. 
The diene rubbers are in general highly cross-linked. They contain at least 
50% by weight, preferably more than 70% by weight, of gel. The rubbers are 
generally present in the form of aqueous dispersions obtained by emulsion 
polymerisation, i.e. in the form of latices. They preferably contain as 
rubbers homopolymers of conjugated dienes containing from 4 to 8 carbon 
atoms, such as butadiene, isoprene and chloroprene, butadiene being 
particularly preferred, or copolymers thereof with up to 40% by weight, 
preferably up to 10% by weight of a vinyl compound, such as acrylonitrile, 
methacrylonitrile, styrene, .alpha.-methyl styrene, halogen substituted 
styrenes, C.sub.1 -C.sub.4 alkyl styrenes, C.sub.1 -C.sub.6 alkyl 
acrylates and methacrylates, acrylic acid, methacrylic acid, vinyl 
sulphonic acid, allyl sulphonic acid, alkylene glycol diacrylates and 
methacrylates or divinyl benzene. 
Liquid hydrocarbons which may be added to the dispersion media (C) are, in 
particular, aliphatic or aromatic, optionally halogenated, hydrocarbons, 
for example pentane, hexane, cyclohexane, heptane, low molecular weight 
paraffin mixtures, benzene, toluene and xylene, or halogen derivatives 
thereof, for example chloroform, methylene chloride, chlorobenzene, 
dichlorobenzene and dichloroethylene. 
To carry out the process for producing the dispersions, a latex of an 
acrylate homo- or co-polymer is suspended in one of the above mentioned 
dispersion media. To this end, generally, from 0.005 to 4=by weight of a 
dispersant is added to the dispersion medium. Known conventional 
dispersants can be used, although it is particularly preferred to use 
acrylic acid esters or methacrylic acid esters, aliphatic (C.sub.4 
-C.sub.22) alcohols, partial reaction products of maleic 
acid/.alpha.-olefin copolymers and long-chain alkanols, long-chain 
aliphatic carboxylic acids, resinic acid, high molecular weight alcohols, 
esters, ethers and/or polyolefins, e.g., dispersion medium soluble 
polybutadienes. Suspension of the latices in the organic liquids requires 
vigorous agitation. In general, from 3 to 50 parts, by weight, of latex 
can be suspended in 100 parts by weight of organic liquid. As the latices 
generally contain from 30 to 60% by weight, of solids, this means a rubber 
content of from 1 to 20% by weight in the organic dispersion. 
A coagulation agent is then added with stirring to the rubber emulsion 
suspension in the organic liquid in a quantity which is sufficient to 
break the aqueous emulsion of the rubber. The coagulation agent is 
normally used in a quantity of from 2 to 20% by weight, based on the 
solids content of the aqueous emulsion to be dispersed. The dispersion 
according to the present invention which, in addition to the dispersed 
rubber, contains water in the form of a water-in-oil emulsion is, 
generally, formed either immediately or at the latest after 1 hour at a 
temperature of from 0.degree. to 100.degree. C., preferably from 
20.degree. to 50.degree. C. 
If desired, this water may be removed either by selectively breaking the 
water-in-oil emulsion (e.g., by adding electrolytes, such as acids or 
bases) and separating off the water as a separate phase or by 
azetropically distilling off the water immediately without coagulation. 
The water-containing rubber dispersions according to the present invention 
have a more or less milky appearance, whilst the water-free rubber 
dispersions are opaque. The intrinsic viscosity therof may be influenced 
by acids or bases. 
The organic dispersions are largely unaffected by electrolytes, acids or 
bases. They may be precipitated using large quantities of certain 
solvents, for example aliphatic alcohols, ketones (for example acetone), 
acetonitrile and dimethyl formamide. 
The dispersions according to the present invention may be polymerised, for 
example by means of radical initiators or redox initiators, and hardened 
at room temperatures of from 0.degree. to 150.degree. C. Where the 
dispersions additionally contain reinforcing fillers, pigments and the 
like, they may be used for the production of impact-resistant coatings or, 
for example, as cast resins having specialised properties, such as high 
resistance to ageing.

EXAMPLES 
Production of the aqueous rubber emulsions: 
The production of 1,3-diolefin (co)polymer latices by emulsion 
polymerisation is known. 
The following emulsions are used for the dispersion tests (Table 1). 
TABLE 1 
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No.Example 
Type of rubber 
##STR1## Latex particle size(*) (nm) 
pH 
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1 polybutadiene (BR) 
##STR2## 400 nm alkaline 
2 polybutadiene (BR) 
##STR3## 100 nm alkaline 
3 polybutadiene (BR) 
##STR4## 800 nm alkaline 
4 acrylonitrile/ butadiene (NBR) 
##STR5## 350 nm neutral 
5 butadiene/ styrene (SBR) 
##STR6## 300 nm alkaline 
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(*)as measured by light scattering; cf. "Polymeranalytik", M. Hoffmann et 
al, Georg Thieme Verlag, Stuttgart (1977); 
(**)based on the total weight of the emulsion; 
(***)based on 100 parts, by weight, of the rubber present in emulsion. 
Production of the rubber dispersions according to the present invention: 
General procedure: 
800 parts, by weight, of an organic medium are stirred with X parts, by 
weight, of a dispersant. 200 parts, by weight, of the aqueous rubber 
emulsions (Example 1 to 5) are then added with stirring. Y parts, by 
weight, of a coagulation agent are then added to the suspension, followed 
by stirring for Z minutes at room temperature, resulting in formation of 
the rubber dispersions in organic media (Table 2) 
TABLE 2 
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Type of 
coagulation Rubber particle 
agent in Y 
Type of dispersant in 
Stirring 
size (*) in the 
Example 
Rubber 
Type of organic medium 
parts, by 
X parts, by weight, 
time in 
organic medium 
No. emulsion 
(**) weight (***) Z mins. 
(nm) 
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6 1 72%, by weight styrene 
1 acetic acid 
0.2 dispersant A 
10 740 
28%, by weight acrylonitrile 
7 2 72%, by weight styrene 
" " 10 200 
28%, by weight acrylonitrile 
8 3 72%, by weight styrene 
" " 10 1450 
28%, by weight acrylonitrile 
9 4 72%, by weight styrene 
" " 10 560 
28%, by weight acrylonitrile 
10 5 72%, by weight styrene 
" " 10 490 
28%, by weight acrylonitrile 
11 1 72%, by weight styrene 
" 0.3 dispersant B 
10 745 
28%, by weight acrylonitrile 
12 1 72%, by weight styrene 
" 0.3 dispersant C 
10 735 
28%, by weight acrylonitrile 
13 1 100%, by weight, methyl meth- 
" 0.2 dispersant A 
30 690 
acrylate 
14 1 100%, by weight, methyl meth- 
2 MgSO.sub.4 
" 30 650 
acrylate 
15 1 100%, by weight, n-butyl 
1 acetic acid 
" 20 730 
acrylate 
16 1 80%, by weight, styrene 
2 MgSO.sub.4 
0.1 dispersant A 
30 690 
20%, by weight, t-butyl acrylate 
17 1 61%, by weight, c-hexane 
2 acetic acid 
4 dispersant A 
10 780 
28%, by weight, styrene 
10%, by weight, acrylonitrile 
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(*) determined by light scattering in the case of relatively small 
particles and by optical microscope in the case of relatively large 
particles 
(**) percentages based on 800 parts, by weight, in the general procedure; 
(***) for an explanation of the dispersants, see Table 3. 
TABLE 3 
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Dispersants used in Table 2 
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Type 
A = Reaction products of maleic acid anhydride-1-olefin 
copolymers with higher alkanols (cf. G. Sackmann 
et al, Angew.Makromol.Chemie 69 (l978), No. 1041, 
pages 141-156); 
B = polydecyl methacrylate; 
C = disproportionated abietic acid 
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