Polymer mixture for flexible sheets

Polymer mixtures of a special graft polymer based on acrylate rubber, a special rubbery acrylate copolymer, resin-type vinyl polymers and polyesters containing carbonate groups and their use in manufacturing flexible (leather-type) sheets.

The invention relates to polymer mixtures of a special graft rubber based 
on acrylate, a special acrylate copolymer, certain resin-type vinyl 
polymers and certain polyesters containing carbonate groups which are 
suitable for manufacturing flexible sheets which are resistant to aging 
and have leather-type appearance, and which can be processed by 
calendering and deep-drawing. 
Plastic sheets having leather-type appearance are used, for example, for 
the interior covering of vehicles. For the most part, they are 
manufactured by calendering a crude sheet and subsequently deep-drawing. 
Mixtures of polyvinylchloride (PVC) with various vinyl polymers and 
plasticisers, are most often used as the plastic. These sheets are not 
completely resistant to aging at high temperatures, they contain volatile 
components which trend to migrate, as well as halogen. These disadvantages 
can be attributed predominantly to the polyvinylchloride. There is 
therefore a need for a plastic material which contains no 
polyvinylchloride and yet is suitable for manufacturing leather-type 
sheets. 
A polymer mixture of a special graft rubber based on acrylate, a special 
acrylate copolymer, certain resin-type vinyl polymers and certain 
polyesters containing carbonate groups has been found which has excellent 
suitability for manufacturing soft sheets--also having leather 
embossing--by deep-drawing processes. 
The sheets obtained are resistant to aging, even at high temperatures. Only 
a few auxiliaries (stabilisers, lubricants, mould release agents etc.) are 
required in small amounts for technical processing. The sheets made from 
the polymer mixtures of the invention adhere particularly well to other 
technical polymers, for example to polyurethane. 
The object of the invention is thus a polymer mixture of 
a) 10 to 60, in particular 20 to 50 parts by weight of a graft polymer 
having a rubber content of 20 to 80 weight %, preferably 40 to 65 weight % 
and most preferably 50 to 60 weight % of 
a.1) mixtures of 20 to 40 weight % of acrylonitrile and 80 to 60 weight % 
of styrenes and/or alkylmethacrylates or 
a.2) methylmethacrylate, optionally mixed with up to 30, preferably 2 to 20 
weight % of styrenes and/or up to 30, preferably 2 to 20 weight % of 
alkylacrylates and/or up to 19, preferably 2 to 25 weight % of 
acrylonitrile, onto 
a.3) a particle-type highly crosslinked alkylacrylate rubber which may 
contain copolymerised up to 30, preferably 0.5 to 10 weight %, of dienes, 
having an average particle diameter (d.sub.50) of 80 to 1,000 nm, 
b) 10 to 50, in particular 10 to 40 parts by weight of a partially 
crosslinking rubber-type copolymer made from 5 to 40, preferably 10 to 35 
weight %, of acrylonitrile, styrene, alkylmethacrylate or mixtures thereof 
and 95 to 60, preferably 90 to 65 weight %, of alkylacrylate having a gel 
content of 20 to 99 weight %, a swelling index greater than 10, measured 
in dimethylformamide at 23.degree. C., and an average particle diameter 
(d.sub.50) of 100 to 600 nm, in particular 100 to 300 nm, 
c) 5 to 40, preferably 10 to 30 parts by weight of a non-crosslinked 
polymer of styrenes, acrylonitrile, methacrylonitrile, esters of 
(meth)acrylic acid, vinyl-C.sub.1 -C.sub.4 -carboxylic acids or mixtures 
of these monomers having Staudinger indices [.eta.] (measured in 
dimethylformamide at 23.degree. C.) of 0.3 to 1.5 dl/g, and 
d) 1 to 40, in particular 5 to 30 parts by weight of a polyester containing 
carbonate groups and having recurring structural units of the formula 
##STR1## 
in which X is the radical of a reaction product of a multivalent alcohol 
and a multivalent aliphatic carboxylic acid having a molecular weight of 
800 to 5,000, 
X'=X or is the radical of an aliphatic polyether of molecular weight 800 to 
5,000. 
n=0 or is 1 to 20, and 
m denotes a number greater than 20, preferably 22 to 100. 
Graft polymers a) according to the invention are generally emulsion 
polymers having particulate structure. They consist of particulate 
alkylacrylate rubbers having a gel content of greater than 50, preferably 
70 to 99 weight %, and average particle diameters (d.sub.50) of 80 to 
1,000 nm, as the graft base, and attached to it graft-polymerised 
monomers, such as alkyl(meth)acrylates, styrenes, such as styrene, 
.alpha.-methylstyrene, p-methylstyrene, acrylonitrile or mixtures thereof. 
The alkylacrylate rubbers a.3) can be manufactured by crosslinking 
copolymerisation of preferably C.sub.2 -C.sub.8 -alkylacrylates and 
optionally up to 20 weight % of comonomers, such as styrene, 
methylmethacrylate, vinylmethylether and/or acrylonitrile, and up to 4 
weight % of polyfunctional vinyl monomers and/or allyl monomers, such as 
divinylbenzene, glycol-bis-acrylate, bisacrylamide, triallyl phosphates, 
triallyl citrates, triallylcyanurate, triallylisocyanurate, allyl esters 
of acrylic acid or methacrylic acid, allyl maleats, in particular 
triallylcyanurate or triallylisocyanurate. The acrylate rubbers preferably 
used as graft bases have a bimodal distribution of the average particle 
diameter. Therefore they are preferably mixtures of two particle-type 
rubbers, wherein one has an average particle diameter (d.sub.50) of 150 to 
250 nm and the other has an average particle diameter (d.sub.50) of 400 to 
600 nm. The weight ratio of fine-particle rubber to coarse-particle rubber 
is 1:2 to 2:1. There are therefore two maxima in the distribution curve of 
the average particle diameter of a mixture of the two rubbers which may 
have the same or different chemical composition. 
Particularly suitable coarse-particle rubbers have a core/shell structure 
(see German Offenlegungsschrift 3 006 804). 
Particularly preferred rubbers a.3), i.e. graft bases according to the 
invention for the preparation of component a) are therefore mixtures of 
larger rubber particles having core/shell structure and smaller rubber 
particles without core/shell structure. The rubbers used for graft 
polymerisation are crosslinked and have gel contents of 50 to 99, 
preferably 70 to 99 weight %. To prepare a), the vinyl monomers are graft 
polymerised onto the acrylate rubbers present in emulsion whilst 
maintaining the emulsion. Styrene and acrylonitrile are preferably 
employed as vinyl monomers. 
The vinyl monomers are preferably polymerised at a graft yield of more than 
40 weight %, that is a greater part of the vinyl monomers is chemically 
bonded to the rubber (via covalent bonds). Such high graft yields are 
obtained by working in a manner known per se using redox initiators, 
preferably using combinations of hydrogen peroxide and ascorbic acid, 
optionally adding suitable heavy metal cations. 
Copolymers b) according to the invention are partially crosslinked 
rubber-type copolymers of acrylonitrile, styrene, C.sub.1 -C.sub.6 
-alkylmethacrylate, in particular C.sub.1 -C.sub.3 -alkylmethacrylate, or 
mixtures thereof, preferably of acrylonitrile and/or methylmethacrylate 
and an alkylacrylate, in particular C.sub.3 -C.sub.8 -alkylacrylate, and 
of 0.05 to 5 weight %, relative to the monomers contained in the 
copolymer, of a polyfunctional, copolymerisable polyvinyl or allyl 
compound, preferably triallylcyanurate, triallylisocyanurate, vinylethers 
of polyols, vinyl esters or allyl esters of polyfunctional carboxylic 
acids and bisacrylamides of diamines. The copolymers b) have gel contents 
of 20 to 99 weight %, in particular 40 to 99 weight %, a swelling index 
greater than 10, preferably 10 to 100, measured in dimethylformamide at 
23.degree. C. and average particle diameter (d.sub.50) of 100 to 600 nm, 
in particular 100 to 300 nm. 
The polymers b) can be prepared in known manner by radical, aqueous 
emulsion polymerisation in the presence of anionic, surface-active 
materials in the temperature range from 40.degree. to 95.degree. C., in 
particular 55.degree. to 80.degree. C. 
Vinyl polymers c) in the sense of the invention are resin-type polymers or 
copolymers made from styrenes, such as styrene, .alpha.-methylstyrene, 
p-methylstyrene, acrylonitrile, methacrylonitrile, esters of (meth)acrylic 
acid, vinyl-C.sub.1 -C.sub.4 -carboxylic acids or mixtures of the monomers 
mentioned having Staudinger indices [.eta.] of 0.3 to 1.5 dl/g (measured 
in dimethylformamide at 23.degree. C.) as a measure of the molecular 
weight. Preferred copolymers made from styrene or .alpha.-methylstyrene 
and acrylonitrile are those which contain optionally up to 40 weight % of 
acrylic or methacrylic acid esters, in particular methylmethacrylate or 
butylacrylate. 
The vinyl polymers c) are obtained according to conventional processes, for 
example bulk, solution, suspension or emulsion free-radial polymerisation, 
preferably by free-radical emulsion polymerisation in water. 
Polyesters d) according to the invention are polyesters containing 
carbonate groups having recurring structural units of the formula 
##STR2## 
having the abovementioned meaning for X, X', n and m. 
Reaction products of multivalent alcohols and multivalent aliphatic 
carboxylic acids are preferably those of divalent and optionally 
additionally trivalent alcohols and preferably divalent aliphatic 
carboxylic acids. (Their radicals correspond to X in formula I.) Instead 
of the free carboxylic acids, anhydrides or esters thereof may also be 
used with low alcohols or mixtures thereof. The multivalent carboxylic 
acids are preferably acyclic. Examples which may be mentioned are oxalic 
acid, malonic acid, succinic acid, adipic acid, suberic acid, azelaic 
acid, sebacic acid, hexahydrophthalic acid anhydride, glutaric acid 
anhydride, preferably adipic acid. 
Multivalent alcohols which may be used, optionally in the presence of one 
another, are, for example, ethylene glycol, 1,2-propylene glycol and 
1,3-propylene glycol, 1,4-butylene glycol and 2,3-butylene glycol, 
1,6-hexanediol, 1,8-octanediol, neopentyl glycol, cyclohexanedimethanol, 
1,4-bis-(hydroxymethylcyclohexane), 2-methyl-1,3-propanediol, diethylene 
glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol and 
dibutylene glycol. 1,6-Hexanediol and neopentyl glycol are preferably 
used. 
The reaction products obtained from carboxylic acids and alcohols are 
polyesters having terminal hydroxyl groups. They have molecular weights of 
800 to 5,000; they can be represented by the formula HO--X--OH, wherein X 
has the abovementioned meaning. 
The polyesters containing carbonate groups result from said polyesters 
having terminal hydroxyl groups, by reacting with bifunctional aryl 
carbonates. 
Bifunctional aryl carbonates are in particular those of the formula 
##STR3## 
wherein Ar is a substituted or unsubstituted aryl radical having 6 to 18 
carbon atoms, preferably having 6 carbon atoms, 
n=0 or is 1 to 20, and 
X' is the bivalent radical of a polyester of polyether as defined above. 
Diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene 
glycol and dibutylene glycol may be mentioned as diols containing ether 
groups. 
Polyesters containing carbonate groups are preferably prepared by 
polycondensation in high-viscosity reactors, such as kneaders or extruders 
(c.f. U.S. Pat. No. 4,192,940). 
The polymer mixture of the invention of a) to d) can be prepared, for 
example as follows: 
If a), b) and c) are in aqueous dispersion, the dispersions can be mixed in 
the ratio of the required solids, and can be worked-up together. The 
powder formed primarily can optionally be fabricated to granule form and 
conventionally auxiliaries can be added. 
d) is mixed with a), b) and c in known devices, such as extruders, rollers, 
kneaders or powder mixers. 
Components a), b) and c) can also be processed separately and then mixed 
with d). 
Unless otherwise stated, gel contents and swelling indices were determined 
in dimethylformamide at 23.degree. C. (see M. Hoffmann et al., 
Polymeranalytik (Polymer analysis) II, Georg-Thieme-Verlag, Stuttgart, 
1977). The particle diameters are average particle diameters d.sub.50 (see 
also "Ultrazentrifugenmessungen" (Ultracentrifuge measurements), W. 
Scholtan et al., Kolloidz. 
Graft yield is the weight ratio of graft-polymerised, resin-forming 
monomers to the total amount of resin-forming monomers used.

EXAMPLES 
Graft Polymer a) 
Preparation of the acrylate rubber (graft base) 
The following are placed in a reactor: 
17,232 parts by weight of water and 588 parts by weight of a polybutadiene 
rubber latex having a polymer solids content of 42 weight % and an average 
particle diameter (d.sub.50) of 140 nm. After heating the mixture to 
63.degree. C., a solution of 49.2 parts by weight of potassium 
peroxodisulphate and 1,152 parts by weight of water is added. The 
following mixtures are then fed into the reactor simultaneously in the 
course of 5 hours at 63.degree. C. 
Solution 1: 
36,000 parts by weight of n-butylacrylate 
81,0 parts by weight of triallylcyanurate 
Solution 2: 
40,800 parts by weight of water 
384 parts by weight of sodium C.sub.14 -C.sub.18 -alkylsulphonate. 
The mixture is then allowed to polymerise to completion for 4 hours at 
63.degree. C. An emulsion having a polymer solids content of 37 weight % 
is obtained. The average latex particle diameter (d.sub.50) is 480 nm. The 
polymer has a gel content of 93 weight %. 
Preparation of the graft polymer 
734 parts by weight of water, 4,784 parts by weight of latex of the 
acrylate rubber graft base are placed in a reactor. The reactor is flushed 
with nitrogen for 30 minutes and the mixture is heated to 70.degree. C. 
The following solution 1 is added with stirring: 
Solution 1: 
190 parts by weight of water 
6 parts by weight of potassium peroxodisulphate 
3 parts by weight of sodium C.sub.14 -C.sub.18 -alkylsulphonate. 
The solutions 2 and 3 are then fed into the reactor at 70.degree. C. 
simultaneously in the course of 5 hours. 
Solution 2: 
850 parts by weight of styrene 
330 parts by weight of acrylonitrile 
Solution 3: 
1,500 parts by weight of water 
20 parts by weight of sodium C.sub.14 -C.sub.18 -alkyl sulphonate. 
The mixture is allowed to polymerise to completion for 4 hours at 
70.degree. C. An emulsion having a polymer solids content of 35 weight % 
is obtained. The rubber content of the polymer is 60 weight %. 
Copolymer b) 
Preparation of the acrylonitrile/n-butylacrylate copolymer 
A solution of 2.5 parts by weight of sodium salt of C.sub.14 -C.sub.18 
-alkylsulphonic acids and 750 parts by weight of water are placed in a 
reactor with stirring. After heating to 70.degree. C., 70 parts by weight 
of solution A) is added and the polymerisation is initiated by adding a 
solution of 3.5 parts by weight of potassium peroxodisulphate in 50 parts 
by weight of water. At 70.degree. C. the remainder of solution A) and 
solution B) are added to the reactor simultaneously in the course of 6 
hours and the mixture is polymerised to completion in the course of 4 
hours. A latex having a polymer solids content of 38 weight %, having an 
average particle diameter (d.sub.50) of 180 nm and a gel content (in 
dimethylformamide at 23.degree. C.) of 98 weight % is obtained. 
Solution A: 
1,105 parts by weight of n-butylacrylate 
7 parts by weight of triallylcyanurate 
474 parts by weight of acrylonitrile 
Solution B: 
30 parts by weight of sodium salt of C.sub.14 -C.sub.18 -alkylsulphonic 
acids 
1,790 parts by weight of water. 
Polymer c) 
Preparation of the styrene-acrylonitrile copolymer 
A solution of 6 parts by weight of disproportionated abietic acid, 4 parts 
by weight of 1 normal caustic soda in 3,080 parts by weight of water are 
placed in a reactor, flushed with nitrogen and heated to 70.degree. C. 200 
parts by weight of solution A) are added with stirring and the 
polymerisation is initiated by adding a solution of 8 parts by weight of 
potassium peroxodisulphate in 200 parts by weight of water. The remainder 
of solution A) and solution B) are added to the reactor simultaneously in 
the course of 5 hours at 70.degree. C. 
The mixture is allowed to polymerise to completion for 4 hours at 
70.degree. C. An emulsion having a polymer solids content of 33 weight % 
is obtained. The polymer isolated has a Staudinger index [.eta.] of 0.7 
dl/g (in dimethylformamide at 23.degree. C.). 
Solution A: 
1,994 parts by weight of styrene 
756 parts by weight of acrylonitrile 
2,6 parts by weight of tert.-dodecylmercaptan 
Solution B: 
54 parts by weight of disproportionated abietic acid 
40 parts by weight of normal caustic soda 
2,050 parts by weight of water. 
Polyester d) 
Polyester d.1) 
Preparation of a polyester carbonate rubber 
1,000 parts by weight of a polyester diol made from adipic acid and a 
mixture of n-hexane-1,6-diol and neopentyl glycol in a weight ratio of 
65:35 having a number average molecular weight Mw=2,000 g.mole.sup.-1 
(determined via OH number), 107 parts by weight of diphenylcarbonate and 
0.12 part by weight of sodium phenolate are stirred in a tank for 2 hours 
at 130.degree. C. and then stirred for 1 hour at 160.degree. C. under a 
vacuum of 0.5 torr. Excess phenol is initially distilled off during 
stirring, and to remove the residual phenol the remaining high viscosity 
solid is pumped into a screw-extruder (Werner & Pfleiderer ZSK 32) using a 
geared pump to increase the molar mass (phenol content&lt;10 ppm, residence 
time: .tau..ltoreq.5', temperatures in the extruder: Ti=180.degree. C.). 
Colourless, high molecular granules are obtained having [.eta.] 2.3 dl/g 
(in tetrahydrofurane) 
Polyester d.2) 
Preparation of a polyester ether carbonate rubber 
2,000 parts by weight of a polyester diol made from adipic acid and a 
mixture of n-hexane-1,6-diol and neopentyl glycol in a weight ratio of 
65:35 and a number average molecular weight M.sub.w =2,000 g.mole.sup.-1 
(determined by OH number), 24 parts of diphenylcarbonate and 0.12 part of 
sodium phenolate, are stirred for 2 hours at 130.degree. C. and for 1 hour 
at 150.degree. C. under a vacuum of 1.0 torr. Excess phenol is distilled 
off; during the distillation the temperature is kept at 180.degree. C. for 
4 hours and 20 parts by weight of polytetrahydrofuran-diol (M.sub.w =2,000 
g.mole.sup.-1) having terminal phenylcarbonate groups are added 
continuously. The reaction temperature increases to 190.degree. C. The 
mixture is stirred for approximately a further 5 hours. To remove the 
residual phenol, the remaining high viscosity solid is pumped using a 
geared pump into a screw extruder (Werner & Pfleiderer ZKS 32) to increase 
the molar mass (phenol content &lt;10 ppm, .tau..ltoreq.4', temperature in 
extruder: Ti=200.degree. C.). Colourless, high-molecular granules having 
[.eta.]=1.4 dl/g (THF) are obtained. 
Preparation and properties of the polymer mixtures 
To prepare the polymer mixtures, the latices of components a), b) and c) 
are mixed in such a way that the solid portions result in the compositions 
of the polymer mixtures given in Table 1. 1 weight % (relative to solids) 
of a phenolic stabiliser is added to the latex mixtures and the mixture is 
coagulated using aqueous magnesium sulphate solution. The powders obtained 
primarily are filtered off, washed and dried at 60.degree. C. The powders 
are homogenised with component d) in accordance with Table 1 and 0.4 
weight % of ester wax on a mixing roller apparatus for 10 minutes at 
190.degree. C., and compressed at 200.degree. C. to give test bodies. The 
properties of the test bodies are shown in Table 2. 
Test methods 
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Tensile strength DIN 53 455 
Extension DIN 53 455 
Tear strength DIN 53 515 
Shore hardness DIN 53 505/type D 
Cold strength DIN 53 372 
(Drop hammer method) 
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Deep-drawing test 
A sheet manufactured on a roller (length 300 mm, width 300 mm, thickness 1 
mm) is attached to a deep-drawing mould and heated at 160.degree. C. or 
175.degree. C. surface temperature (determination of the surface 
temperature by means of fusible salt). A frustum according to FIG. 1 is 
pressed to a depth of 21 cm into the sheet while applying a vacuum. 
Assessment 
+ A hollow body corresponding to the frustum and having even wall thickness 
is obtained at 160.degree. C. and at 175.degree. C. surface temperature. 
comparison of aging resistance of the polymer mixtures 1 and 2 of the 
invention with known deep-drawing compounds containing polyvinylchloride 
Sheets made from the materials are stored at 130.degree. C. and 150.degree. 
C. for 21 days. Whereas the sheets containing polyvinylchloride discolour 
to dark brown or black, the colour of the sheets of the invention hardly 
changes. 
TABLE 1 
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Composition of the polymer mixtures 
Test Components 
No. a b c d.sub.1 
d.sub.2 
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1 36 36 18 10 -- 
2 36 36 18 -- 10 
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TABLE 2 
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Properties of the mixtures of Table 1 
Shore Deep 
Tensile Exten- Tear hard- Cold draw 
Test strength sion strength 
ness strength 
behav- 
No. [MPa] [%] [N/mm] [15"] [.degree.C.] 
iour 
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1 15.4 265 50 30 -19 + 
2 14.8 253 52 30 -21 + 
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