CA2026353A1 - Process for the production of polychloroprene of moderate viscosity - Google Patents
Process for the production of polychloroprene of moderate viscosityInfo
- Publication number
- CA2026353A1 CA2026353A1 CA 2026353 CA2026353A CA2026353A1 CA 2026353 A1 CA2026353 A1 CA 2026353A1 CA 2026353 CA2026353 CA 2026353 CA 2026353 A CA2026353 A CA 2026353A CA 2026353 A1 CA2026353 A1 CA 2026353A1
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- Prior art keywords
- polychloroprene
- mooney viscosity
- viscosity
- zone
- product
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- 229920001084 poly(chloroprene) Polymers 0.000 title claims abstract description 29
- 238000000034 method Methods 0.000 title claims abstract description 18
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 8
- 238000010525 oxidative degradation reaction Methods 0.000 claims abstract description 8
- 238000010008 shearing Methods 0.000 claims abstract description 3
- YACLQRRMGMJLJV-UHFFFAOYSA-N chloroprene Chemical compound ClC(=C)C=C YACLQRRMGMJLJV-UHFFFAOYSA-N 0.000 claims description 5
- 239000000155 melt Substances 0.000 claims description 3
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical class CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 30
- 239000000047 product Substances 0.000 description 17
- 238000006243 chemical reaction Methods 0.000 description 13
- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 description 10
- 239000003795 chemical substances by application Substances 0.000 description 6
- 229920001971 elastomer Polymers 0.000 description 6
- 239000005060 rubber Substances 0.000 description 6
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 5
- 238000010438 heat treatment Methods 0.000 description 5
- 229920000642 polymer Polymers 0.000 description 5
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 description 5
- 238000013022 venting Methods 0.000 description 5
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 4
- 238000006731 degradation reaction Methods 0.000 description 4
- 229910052760 oxygen Inorganic materials 0.000 description 4
- 239000001301 oxygen Substances 0.000 description 4
- 229910052717 sulfur Inorganic materials 0.000 description 4
- 239000011593 sulfur Substances 0.000 description 4
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical class CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 3
- UHOVQNZJYSORNB-UHFFFAOYSA-N Benzene Chemical class C1=CC=CC=C1 UHOVQNZJYSORNB-UHFFFAOYSA-N 0.000 description 3
- -1 air for example Chemical compound 0.000 description 3
- 230000015556 catabolic process Effects 0.000 description 3
- 239000007795 chemical reaction product Substances 0.000 description 3
- 238000001125 extrusion Methods 0.000 description 3
- 239000000178 monomer Substances 0.000 description 3
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 description 2
- 238000005273 aeration Methods 0.000 description 2
- 230000032683 aging Effects 0.000 description 2
- 238000007605 air drying Methods 0.000 description 2
- 230000003750 conditioning effect Effects 0.000 description 2
- RWGFKTVRMDUZSP-UHFFFAOYSA-N cumene Chemical class CC(C)C1=CC=CC=C1 RWGFKTVRMDUZSP-UHFFFAOYSA-N 0.000 description 2
- NNBZCPXTIHJBJL-UHFFFAOYSA-N decalin Chemical compound C1CCCC2CCCCC21 NNBZCPXTIHJBJL-UHFFFAOYSA-N 0.000 description 2
- AUZONCFQVSMFAP-UHFFFAOYSA-N disulfiram Chemical compound CCN(CC)C(=S)SSC(=S)N(CC)CC AUZONCFQVSMFAP-UHFFFAOYSA-N 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000012634 fragment Substances 0.000 description 2
- OKJPEAGHQZHRQV-UHFFFAOYSA-N iodoform Chemical class IC(I)I OKJPEAGHQZHRQV-UHFFFAOYSA-N 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 238000004073 vulcanization Methods 0.000 description 2
- LLMLGZUZTFMXSA-UHFFFAOYSA-N 2,3,4,5,6-pentachlorobenzenethiol Chemical compound SC1=C(Cl)C(Cl)=C(Cl)C(Cl)=C1Cl LLMLGZUZTFMXSA-UHFFFAOYSA-N 0.000 description 1
- LIFLRQVHKGGNSG-UHFFFAOYSA-N 2,3-dichlorobuta-1,3-diene Chemical compound ClC(=C)C(Cl)=C LIFLRQVHKGGNSG-UHFFFAOYSA-N 0.000 description 1
- XTEGARKTQYYJKE-UHFFFAOYSA-M Chlorate Chemical class [O-]Cl(=O)=O XTEGARKTQYYJKE-UHFFFAOYSA-M 0.000 description 1
- BWGNESOTFCXPMA-UHFFFAOYSA-N Dihydrogen disulfide Chemical compound SS BWGNESOTFCXPMA-UHFFFAOYSA-N 0.000 description 1
- RWSOTUBLDIXVET-UHFFFAOYSA-N Dihydrogen sulfide Chemical class S RWSOTUBLDIXVET-UHFFFAOYSA-N 0.000 description 1
- 244000043261 Hevea brasiliensis Species 0.000 description 1
- 241001441571 Hiodontidae Species 0.000 description 1
- LSDPWZHWYPCBBB-UHFFFAOYSA-N Methanethiol Chemical compound SC LSDPWZHWYPCBBB-UHFFFAOYSA-N 0.000 description 1
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 238000012662 bulk polymerization Methods 0.000 description 1
- 229950005499 carbon tetrachloride Drugs 0.000 description 1
- 238000005119 centrifugation Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- HHEAADYXPMHMCT-UHFFFAOYSA-N dpph Chemical class [O-][N+](=O)C1=CC([N+](=O)[O-])=CC([N+]([O-])=O)=C1[N]N(C=1C=CC=CC=1)C1=CC=CC=C1 HHEAADYXPMHMCT-UHFFFAOYSA-N 0.000 description 1
- 239000000839 emulsion Substances 0.000 description 1
- 238000010528 free radical solution polymerization reaction Methods 0.000 description 1
- 125000000524 functional group Chemical group 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 239000000395 magnesium oxide Substances 0.000 description 1
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 1
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 229910044991 metal oxide Inorganic materials 0.000 description 1
- 150000004706 metal oxides Chemical class 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- BFILSCOSKRGQTH-UHFFFAOYSA-N n-(2-sulfanylphenyl)benzamide;zinc Chemical compound [Zn].SC1=CC=CC=C1NC(=O)C1=CC=CC=C1 BFILSCOSKRGQTH-UHFFFAOYSA-N 0.000 description 1
- ZHMIOPLMFZVSHY-UHFFFAOYSA-N n-[2-[(2-benzamidophenyl)disulfanyl]phenyl]benzamide Chemical class C=1C=CC=CC=1C(=O)NC1=CC=CC=C1SSC1=CC=CC=C1NC(=O)C1=CC=CC=C1 ZHMIOPLMFZVSHY-UHFFFAOYSA-N 0.000 description 1
- 229920003052 natural elastomer Polymers 0.000 description 1
- 229920001194 natural rubber Polymers 0.000 description 1
- 150000002823 nitrates Chemical class 0.000 description 1
- 238000001935 peptisation Methods 0.000 description 1
- 150000002978 peroxides Chemical class 0.000 description 1
- 238000006116 polymerization reaction Methods 0.000 description 1
- 230000003134 recirculating effect Effects 0.000 description 1
- 150000004671 saturated fatty acids Chemical class 0.000 description 1
- 235000003441 saturated fatty acids Nutrition 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 125000001424 substituent group Chemical group 0.000 description 1
- 229920003051 synthetic elastomer Polymers 0.000 description 1
- 239000005061 synthetic rubber Substances 0.000 description 1
- VZGDMQKNWNREIO-UHFFFAOYSA-N tetrachloromethane Chemical class ClC(Cl)(Cl)Cl VZGDMQKNWNREIO-UHFFFAOYSA-N 0.000 description 1
- PXXNTAGJWPJAGM-UHFFFAOYSA-N vertaline Natural products C1C2C=3C=C(OC)C(OC)=CC=3OC(C=C3)=CC=C3CCC(=O)OC1CC1N2CCCC1 PXXNTAGJWPJAGM-UHFFFAOYSA-N 0.000 description 1
- 150000003751 zinc Chemical class 0.000 description 1
- 239000011787 zinc oxide Substances 0.000 description 1
- ONSIBMFFLJKTPT-UHFFFAOYSA-L zinc;2,3,4,5,6-pentachlorobenzenethiolate Chemical compound [Zn+2].[S-]C1=C(Cl)C(Cl)=C(Cl)C(Cl)=C1Cl.[S-]C1=C(Cl)C(Cl)=C(Cl)C(Cl)=C1Cl ONSIBMFFLJKTPT-UHFFFAOYSA-L 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08C—TREATMENT OR CHEMICAL MODIFICATION OF RUBBERS
- C08C19/00—Chemical modification of rubber
- C08C19/08—Depolymerisation
Landscapes
- Chemical & Material Sciences (AREA)
- General Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
Abstract
A PROCESS FOR THE PRODUCTION OF POLYCHLOROPRENE OF MODERATE
VISCOSITY
A b s t r a c t Products of low viscosity and surprisingly low gel content can be obtained by thermo-oxidative degradation and shearing of polychloroprene.
VISCOSITY
A b s t r a c t Products of low viscosity and surprisingly low gel content can be obtained by thermo-oxidative degradation and shearing of polychloroprene.
Description
2 ~ 3 A PROCESS FOR THE PRODUCTION OF_POLYCHLOROPRENE OF MODERATE
VISCOSITY
This invention relates to a process for the production of polychloroprene (CR) of moderate viscosity and, hence, good processability by $hermo-oxidative degradation of CR
of relatively high viscosity.
By virtue of their balanced properties, particularly their temperature, ozone and oil resistance, CR vulcan-izates are outstanding rubbers which are superior to many other materials. They are widely used in the adhesives, cable and automotive industries. CR is available as a solid rubber with Mooney viscosities of from about 35 to about 120 (ML 1+4) 100~C.
Low-viscosity CR types are reguired as solid rubbers for certain applications. They may be produced using large quantities of regulators by bulk polymerization (JP-A
72/8608), by emulsion pol~merization with subsequent working up (GB-PSS 905,971 and 963,075) or by solution polymerization with subsequent removal of the solvent (DE-OSS 2 423 7~4 and 2 444 565). On account of their high content of chemically incorporated fragments emanating from the regulators, these low-viscosity CR types are not entirely satisfactory in their vulcanization activity.
It is known that synthetic rubbers are not as easy to masticate as natural rubber, particularly when the rubbers have electron-attracting substituents (such as CN, Cl); cf.
H. Fries and R.R. Pandit, Rubber Chem. Technol. 55, 309 et g. Whereas attempts to degrade CR in decalin solution at 150C led within a few hours to a CR having 1/20th of its original molecular weight, it was reported that a gel was formed in the attempted thermo-oxidative degradation of CR;
cf. K. Itoyama, 122nd Meeting of the Rubber Division of the Amer. Chem. Soc., Chicago/Ill., 04.07.10.1982.
A process has now been found in which a low-viscosity Le A 26 743 3 ~ 3 CR of low gel content is obtained by thermo-oxidative degradation of CR.
The present invention relates ~o a process for the production of polychloroprene having a Mooney viscosity of 5 to 30 and preferably 10 to 25 (ML 1+4) 100C by thermo-oxidative degradation of a polychloroprene having a Mooney viscosity of 35 to 120 and preferably 45 to 100 (ML 1+4) 100C at a melt temperature of 40C to 200C and prefer-ably 70C to 185C by shearing at a shear rate of 30 to 5000 sec~1 and preferably 50 to 1000 sec~l until the desired Mooney viscosity is reached.
Polychloroprenes suitable as starting products for the process according to the invention are chloroprene polymers which, in addition to polymerized 2-chloroprene units, may contain 0.05 to 30% by weight and preferably 0.1 to 20% by weight, based on chloroprene polymer of copolymerized units of other ethylenically unsaturated monomers or sulfur, i.e.
polychloroprenes of the type described, for example, in "Methoden der organischen Chemie" (Houben-Weyl), Vol.
E20/2, 842-859, Georg Thieme Verlag, Stuttgart - New York 1987.
Preferred ethylenically unsaturated "other monomers"
copolymerizable with chloroprene are, essentially, 2,3-dichlorobutadiene and l-chlorobutadiene. Sulfur-modified polychloroprenes are preferred.
The quantity of elemental sulfur used for the production of sulfur-modified polychloroprene is 0.05 to 1.5% by weight and preferably 0.1 to 1% by weight, based on the monomers used. Where sulfur donors are used, the quantity in which they are used should be gauged in such a way that the sulfur released corresponds to the quantities mentioned above.
The Mooney viscosity is determined in accordance with DIN 53 523.
Suitable machines for carrying out the process Le A 26 743 2 2~3~3 according to the invention include preferably heatable single-screw and multiple-screw extruders, more particular-ly twin-screw extruders, having length-to-diameter ratios of 10 to 100, aeration and vent openings and, optionally, other feed openings for masticating aids. The screw used for the following Examples was a twin-screw extruder with contra-rotating screws having a length of 120 cm, a cylind-er diameter of 3 cm and the following construction:
Feed zone 1 (length 10 cm) with feed opening, Heating zone 2 (length 10 cm), Metering zone 3 (length 10 cm) with aeration opening, Reaction zone 4 (length 60 cm~ with feed openings in the middle and at the end of the zone, Venting zone 5 (length 20 cm) with vent opening, Extrusion zone 6 (length 10 cm) with extrusion head.
The thermo-oxidative degradation reguires the presence of a medium which is capable of stabilizing the fragments terminated by free radicals which are formed under the effect of the chemical energy applied. Media such as these include oxygen itself, gas mixtures containing free oxygen, such as air for example, and oxygen donors which release chemically bound oxygen under reaction conditions, such as for example peroxides, nitrates and chlorates. For reasons of cost, air is the preferred medium.
The process ac¢ording to the invention is preferably carried out using radical transfer agents, agents having radical transfer constants of 50 104 to 20,000 104, preferably 80 104 to 180 104 and, more preferably 110 104 to 150 10~
being particularly effective. The above figures are based on the polymerization of ethy}ene at 130C as described in Polymer Handbook, Ed.: J. Brandrup, E.H. Immergut, 2nd Edition, Wiley, New York 1975. Chain transfer agents of the type in question include mercaptans, such as the iso-Le A 26 743 3 2~3~3 meric xylyl mercaptans, thiophenols and zinc salts thereof, such as pentachlorothiophenol, zinc pentachlorothiophenol, ~-thionaphthol and zinc-o-benzamidothiophenol; aromatic disulfides, such as o,o'-dibenzamidodiphenyl disulfide:
salts of saturated fatty acids, benzene, toluene, acetone, tetrachloromethane, iodoform and cumene.
The necessary quantites are mainly determined by the desired degree of degradation and may be reliably deter-mined by a few preliminary tests.
In the case of sulfur-modified polychloroprenes, the desired degradation may be accelerated by the use of typical peptizing agents of the type described, for ex-ample, in DE-OS 1 911 439, 2 018 736, 2 755 074 and 3 246 748, in DE-PS 2 645 920, in EP-A 21 212 and 200 857, in FR-PS 1 457 004 and in US-PSS 2,264,713, 3,378,538, 3,397,173 and 3,507,825.
By virtue of their functional groups which are formed by the degradation reaction, the low-viscosity polychloro-prenes produced in accordance with the invention may be vulcanized solely with metal oxides, such as magnesium oxide and/or zinc oxide, as vulcanizing agents. The quantities in which the vulcanizing agents are used are generally from 2 to 10% by weight, based on polychloro-prene.
The vulcanization may be carried out at temperatures of 100 to 200C and preferably at temperatures of 130 to 180C, optionally under a preissure of 10 to 200 bar.
The outstanding properties of the vulcanizates are generally obtained without conditioning, although they can often be improved by conditioning.
The polychloroprenes produced in accordance with the invention may be used with advantage for the production of drive belts, air springs, conveyor belts and other in-dustria} rubber articles.
The parts mentioned in the following Examples are Le A 26 743 4 .. . -,j .. ., ., . . . ...
i . . .
` 2~2~i3 parts by weight.
Examples General description of the process:
~he rotational speed of the screw varies between 40 and 60 min~l for a product throughput of 1.5 to 2.5 kg/h.
The product is heated in the heating zone (2) and mixed with 200 to 700 normal liters air under pressure (2 to 40 bar) in zone (3). The product is then transported through the reaction zone (4) at a predetermined melt temperature.
In the process according to the invention, other auxiliar-ies may be added to the polymer either in the middle or at the end of the reaction zone (4) (see individual Examples).
In the venting zone (5), unreacted air and unreacted volatile auxiliaries are removed from the product under a pressure of 10 to 500 mbar. The product is then discharged from the twin-screw extruder via an extrusion head.
The gel content of the polymers is determined by means of an ultracentrifuge (5% concentration in tetrahydrofuran, 60 minutes' centrifugation at 20,000 rpm).
Example 1 A mercaptan-regulated polychloroprene having a Mooney viscosity of 40 (ML 1~4) 100C is degraded to a polychloro-prene having a Mooney viscosity of 18 (ML 1+4) lOO-C. -~
To-this end, 2.3 kg/h polychloroprene are transported through the twin-screw extruder at a rotational speed of the screws of 40 min~l. The product is heated to 60C in the heating zone (2). Air (1500 l/h) is introduced in zone (3) and the product is transported into the reaction zone (4) at 80C. In the reaction zone (4) toluene is intro-duced in a quantity of 800 ml/h. Toluene and unreacted air are removed in the venting zone (5) under a pressure of 40 to 50 mbar, the polychloroprene being heated to 140C.
Le A 26 743 5 ~,~ "i.,~ ,.,. . " - . . . . . .. .
~2631~j~
After discharge from the twin-screw extruder, the product was soluble in tetrahydrofuran; the gel content was below 2% by weight.
Example 2 (Comparison) The polychloroprene having a Mooney viscosity of 40 (ML 1+4) 100C used as starting product for Example 1 is subjected to hot-air ageing at 70C in a recirculating air drying cabinet. Its Mooney viscosity increased and measur-ed 41 (ML 1+4) 100C after 3 days, 43 (ML 1+4) 100C after 5 days and 45 (ML 1+4) 100C after 7 days. The gel content after 7 days was 3.2% by weight.
Example 3 The procedure is as in Example 1, except that a solution of 20 g 2,2-diphenyl-1-picrylhydrazyl in 200 ml toluene was added at the end of reaction zone (4) in a quantity of 200 ml/h. The end product had a Mooney viscosity of 19 (ML 1+4) 100C and a gel content below 2 by weight.
,Example 4 A sulfur-modified polychloroprene having a sulfur content of 0.5% by weight and a Mooney viscosity of 4~ (ML
1+4) 100C is degraded to a polychloroprene having a Mooney viscosity of 19 (ML 1+4) lOO-C.
To this end, 2.45 kg/h polychloroprene are transported through the twin-screw extruder at a rotational speed of ,the screws of 60 min~1. The product is heated to 60C in the heating zone ~2). Air (1650 l/h) is introduced in zone (3) and the product is transported into the reaction zone (4) at 130C. In the reaction zone (4) toluene is intro-duced in a quantity of 900 ml/h. Toluene and unreacted air are removed in the venting zone (5) under a pressure of 10 to 50 mbar, the polychloroprene being heated to 140C.
Le A 26 743 ;.. , :
", , ,. ;~ , " .
After discharge from the twin-screw extruder, the product was soluble in tetrahydrofuran; the gel content was below 2% by weight.
Example 5 (Comparison) The polychloroprene having a Mooney viscosity of 48 used as starting product of Example 4 is subjected to hot-air ageing at 90C in a recirculating-air drying cabinet.
After 14 hours, the Mooney viscosity measures 26 (ML 1+4) 100C, passes through a minimum of 24 (ML 1+4) 100C after 16 hours and measures 27 (ML 1+4) 100C after 18 hours and 65 (ML 1+4) lOODC after 36 hours. The fall in viscosity initially observed is presumably attributable to post-peptization; the viscosity reachable through this degrad-ation is always higher than the viscosity reachable by thermo-oxidative degradation.
Example 6 The procedure is as in Example 4, except that a solution of 20 g tetraethyl thiuram disulfide in 200 ml ; toluene is added at the end of reaction zone (4) in a quantity of 180 ml per hour. The end product was soluble in tetrahydrofuran and had a Mooney viscosity of 16 (ML
1+4) 100C and a gel content below 2% by weight.
~; 25 Example 7 A xanthogen-disulfide-regulated polychloroprene having a Mooney viscosity of 58 (ML 1+4) 100C is degraded to a polychloroprene having a Mooney viscosity of 17 (ML 1+4) 100C.
To this end, 2.2 kg/h polychloroprene are transported through the twin-screw extruder at a rotational speed of the screws of 45 min~~. The product is heated to 60C in the heating zone (2). Air (1600 l/h) is introduced in zone (3) and the product is transported into the reaction zone Le A 26 743 7 3 ~ ~
(4) at 170C. In the reaction zone (4) toluene is intro-duced in a quantity of 1000 ml/h. Toluene and unreacted air are removed in the venting zone (5) under a pressure of 40 to 50 mbar, ~he polychloroprene being heated to 170C.
After discharge from the twin-screw extruder, the product was soluble in tetrahydrofuran: the gel content was below 2% by weight.
Example 8 The procedure is as in Example 7, except that a solution of 18 g xanthogen disulfide in 200 ml toluene is added at the end of reaction zone (4) in a quantity of 190 ml per hour. The end product had a Mooney viscosity of 16 (ML 1+4) 100C and a gel content below 2% by weight.
,~ j .
Le A 26 743 8
VISCOSITY
This invention relates to a process for the production of polychloroprene (CR) of moderate viscosity and, hence, good processability by $hermo-oxidative degradation of CR
of relatively high viscosity.
By virtue of their balanced properties, particularly their temperature, ozone and oil resistance, CR vulcan-izates are outstanding rubbers which are superior to many other materials. They are widely used in the adhesives, cable and automotive industries. CR is available as a solid rubber with Mooney viscosities of from about 35 to about 120 (ML 1+4) 100~C.
Low-viscosity CR types are reguired as solid rubbers for certain applications. They may be produced using large quantities of regulators by bulk polymerization (JP-A
72/8608), by emulsion pol~merization with subsequent working up (GB-PSS 905,971 and 963,075) or by solution polymerization with subsequent removal of the solvent (DE-OSS 2 423 7~4 and 2 444 565). On account of their high content of chemically incorporated fragments emanating from the regulators, these low-viscosity CR types are not entirely satisfactory in their vulcanization activity.
It is known that synthetic rubbers are not as easy to masticate as natural rubber, particularly when the rubbers have electron-attracting substituents (such as CN, Cl); cf.
H. Fries and R.R. Pandit, Rubber Chem. Technol. 55, 309 et g. Whereas attempts to degrade CR in decalin solution at 150C led within a few hours to a CR having 1/20th of its original molecular weight, it was reported that a gel was formed in the attempted thermo-oxidative degradation of CR;
cf. K. Itoyama, 122nd Meeting of the Rubber Division of the Amer. Chem. Soc., Chicago/Ill., 04.07.10.1982.
A process has now been found in which a low-viscosity Le A 26 743 3 ~ 3 CR of low gel content is obtained by thermo-oxidative degradation of CR.
The present invention relates ~o a process for the production of polychloroprene having a Mooney viscosity of 5 to 30 and preferably 10 to 25 (ML 1+4) 100C by thermo-oxidative degradation of a polychloroprene having a Mooney viscosity of 35 to 120 and preferably 45 to 100 (ML 1+4) 100C at a melt temperature of 40C to 200C and prefer-ably 70C to 185C by shearing at a shear rate of 30 to 5000 sec~1 and preferably 50 to 1000 sec~l until the desired Mooney viscosity is reached.
Polychloroprenes suitable as starting products for the process according to the invention are chloroprene polymers which, in addition to polymerized 2-chloroprene units, may contain 0.05 to 30% by weight and preferably 0.1 to 20% by weight, based on chloroprene polymer of copolymerized units of other ethylenically unsaturated monomers or sulfur, i.e.
polychloroprenes of the type described, for example, in "Methoden der organischen Chemie" (Houben-Weyl), Vol.
E20/2, 842-859, Georg Thieme Verlag, Stuttgart - New York 1987.
Preferred ethylenically unsaturated "other monomers"
copolymerizable with chloroprene are, essentially, 2,3-dichlorobutadiene and l-chlorobutadiene. Sulfur-modified polychloroprenes are preferred.
The quantity of elemental sulfur used for the production of sulfur-modified polychloroprene is 0.05 to 1.5% by weight and preferably 0.1 to 1% by weight, based on the monomers used. Where sulfur donors are used, the quantity in which they are used should be gauged in such a way that the sulfur released corresponds to the quantities mentioned above.
The Mooney viscosity is determined in accordance with DIN 53 523.
Suitable machines for carrying out the process Le A 26 743 2 2~3~3 according to the invention include preferably heatable single-screw and multiple-screw extruders, more particular-ly twin-screw extruders, having length-to-diameter ratios of 10 to 100, aeration and vent openings and, optionally, other feed openings for masticating aids. The screw used for the following Examples was a twin-screw extruder with contra-rotating screws having a length of 120 cm, a cylind-er diameter of 3 cm and the following construction:
Feed zone 1 (length 10 cm) with feed opening, Heating zone 2 (length 10 cm), Metering zone 3 (length 10 cm) with aeration opening, Reaction zone 4 (length 60 cm~ with feed openings in the middle and at the end of the zone, Venting zone 5 (length 20 cm) with vent opening, Extrusion zone 6 (length 10 cm) with extrusion head.
The thermo-oxidative degradation reguires the presence of a medium which is capable of stabilizing the fragments terminated by free radicals which are formed under the effect of the chemical energy applied. Media such as these include oxygen itself, gas mixtures containing free oxygen, such as air for example, and oxygen donors which release chemically bound oxygen under reaction conditions, such as for example peroxides, nitrates and chlorates. For reasons of cost, air is the preferred medium.
The process ac¢ording to the invention is preferably carried out using radical transfer agents, agents having radical transfer constants of 50 104 to 20,000 104, preferably 80 104 to 180 104 and, more preferably 110 104 to 150 10~
being particularly effective. The above figures are based on the polymerization of ethy}ene at 130C as described in Polymer Handbook, Ed.: J. Brandrup, E.H. Immergut, 2nd Edition, Wiley, New York 1975. Chain transfer agents of the type in question include mercaptans, such as the iso-Le A 26 743 3 2~3~3 meric xylyl mercaptans, thiophenols and zinc salts thereof, such as pentachlorothiophenol, zinc pentachlorothiophenol, ~-thionaphthol and zinc-o-benzamidothiophenol; aromatic disulfides, such as o,o'-dibenzamidodiphenyl disulfide:
salts of saturated fatty acids, benzene, toluene, acetone, tetrachloromethane, iodoform and cumene.
The necessary quantites are mainly determined by the desired degree of degradation and may be reliably deter-mined by a few preliminary tests.
In the case of sulfur-modified polychloroprenes, the desired degradation may be accelerated by the use of typical peptizing agents of the type described, for ex-ample, in DE-OS 1 911 439, 2 018 736, 2 755 074 and 3 246 748, in DE-PS 2 645 920, in EP-A 21 212 and 200 857, in FR-PS 1 457 004 and in US-PSS 2,264,713, 3,378,538, 3,397,173 and 3,507,825.
By virtue of their functional groups which are formed by the degradation reaction, the low-viscosity polychloro-prenes produced in accordance with the invention may be vulcanized solely with metal oxides, such as magnesium oxide and/or zinc oxide, as vulcanizing agents. The quantities in which the vulcanizing agents are used are generally from 2 to 10% by weight, based on polychloro-prene.
The vulcanization may be carried out at temperatures of 100 to 200C and preferably at temperatures of 130 to 180C, optionally under a preissure of 10 to 200 bar.
The outstanding properties of the vulcanizates are generally obtained without conditioning, although they can often be improved by conditioning.
The polychloroprenes produced in accordance with the invention may be used with advantage for the production of drive belts, air springs, conveyor belts and other in-dustria} rubber articles.
The parts mentioned in the following Examples are Le A 26 743 4 .. . -,j .. ., ., . . . ...
i . . .
` 2~2~i3 parts by weight.
Examples General description of the process:
~he rotational speed of the screw varies between 40 and 60 min~l for a product throughput of 1.5 to 2.5 kg/h.
The product is heated in the heating zone (2) and mixed with 200 to 700 normal liters air under pressure (2 to 40 bar) in zone (3). The product is then transported through the reaction zone (4) at a predetermined melt temperature.
In the process according to the invention, other auxiliar-ies may be added to the polymer either in the middle or at the end of the reaction zone (4) (see individual Examples).
In the venting zone (5), unreacted air and unreacted volatile auxiliaries are removed from the product under a pressure of 10 to 500 mbar. The product is then discharged from the twin-screw extruder via an extrusion head.
The gel content of the polymers is determined by means of an ultracentrifuge (5% concentration in tetrahydrofuran, 60 minutes' centrifugation at 20,000 rpm).
Example 1 A mercaptan-regulated polychloroprene having a Mooney viscosity of 40 (ML 1~4) 100C is degraded to a polychloro-prene having a Mooney viscosity of 18 (ML 1+4) lOO-C. -~
To-this end, 2.3 kg/h polychloroprene are transported through the twin-screw extruder at a rotational speed of the screws of 40 min~l. The product is heated to 60C in the heating zone (2). Air (1500 l/h) is introduced in zone (3) and the product is transported into the reaction zone (4) at 80C. In the reaction zone (4) toluene is intro-duced in a quantity of 800 ml/h. Toluene and unreacted air are removed in the venting zone (5) under a pressure of 40 to 50 mbar, the polychloroprene being heated to 140C.
Le A 26 743 5 ~,~ "i.,~ ,.,. . " - . . . . . .. .
~2631~j~
After discharge from the twin-screw extruder, the product was soluble in tetrahydrofuran; the gel content was below 2% by weight.
Example 2 (Comparison) The polychloroprene having a Mooney viscosity of 40 (ML 1+4) 100C used as starting product for Example 1 is subjected to hot-air ageing at 70C in a recirculating air drying cabinet. Its Mooney viscosity increased and measur-ed 41 (ML 1+4) 100C after 3 days, 43 (ML 1+4) 100C after 5 days and 45 (ML 1+4) 100C after 7 days. The gel content after 7 days was 3.2% by weight.
Example 3 The procedure is as in Example 1, except that a solution of 20 g 2,2-diphenyl-1-picrylhydrazyl in 200 ml toluene was added at the end of reaction zone (4) in a quantity of 200 ml/h. The end product had a Mooney viscosity of 19 (ML 1+4) 100C and a gel content below 2 by weight.
,Example 4 A sulfur-modified polychloroprene having a sulfur content of 0.5% by weight and a Mooney viscosity of 4~ (ML
1+4) 100C is degraded to a polychloroprene having a Mooney viscosity of 19 (ML 1+4) lOO-C.
To this end, 2.45 kg/h polychloroprene are transported through the twin-screw extruder at a rotational speed of ,the screws of 60 min~1. The product is heated to 60C in the heating zone ~2). Air (1650 l/h) is introduced in zone (3) and the product is transported into the reaction zone (4) at 130C. In the reaction zone (4) toluene is intro-duced in a quantity of 900 ml/h. Toluene and unreacted air are removed in the venting zone (5) under a pressure of 10 to 50 mbar, the polychloroprene being heated to 140C.
Le A 26 743 ;.. , :
", , ,. ;~ , " .
After discharge from the twin-screw extruder, the product was soluble in tetrahydrofuran; the gel content was below 2% by weight.
Example 5 (Comparison) The polychloroprene having a Mooney viscosity of 48 used as starting product of Example 4 is subjected to hot-air ageing at 90C in a recirculating-air drying cabinet.
After 14 hours, the Mooney viscosity measures 26 (ML 1+4) 100C, passes through a minimum of 24 (ML 1+4) 100C after 16 hours and measures 27 (ML 1+4) 100C after 18 hours and 65 (ML 1+4) lOODC after 36 hours. The fall in viscosity initially observed is presumably attributable to post-peptization; the viscosity reachable through this degrad-ation is always higher than the viscosity reachable by thermo-oxidative degradation.
Example 6 The procedure is as in Example 4, except that a solution of 20 g tetraethyl thiuram disulfide in 200 ml ; toluene is added at the end of reaction zone (4) in a quantity of 180 ml per hour. The end product was soluble in tetrahydrofuran and had a Mooney viscosity of 16 (ML
1+4) 100C and a gel content below 2% by weight.
~; 25 Example 7 A xanthogen-disulfide-regulated polychloroprene having a Mooney viscosity of 58 (ML 1+4) 100C is degraded to a polychloroprene having a Mooney viscosity of 17 (ML 1+4) 100C.
To this end, 2.2 kg/h polychloroprene are transported through the twin-screw extruder at a rotational speed of the screws of 45 min~~. The product is heated to 60C in the heating zone (2). Air (1600 l/h) is introduced in zone (3) and the product is transported into the reaction zone Le A 26 743 7 3 ~ ~
(4) at 170C. In the reaction zone (4) toluene is intro-duced in a quantity of 1000 ml/h. Toluene and unreacted air are removed in the venting zone (5) under a pressure of 40 to 50 mbar, ~he polychloroprene being heated to 170C.
After discharge from the twin-screw extruder, the product was soluble in tetrahydrofuran: the gel content was below 2% by weight.
Example 8 The procedure is as in Example 7, except that a solution of 18 g xanthogen disulfide in 200 ml toluene is added at the end of reaction zone (4) in a quantity of 190 ml per hour. The end product had a Mooney viscosity of 16 (ML 1+4) 100C and a gel content below 2% by weight.
,~ j .
Le A 26 743 8
Claims (4)
1. A process for the production of polychloroprene having a Mooney viscosity of 5 to 30 (ML 1+4) 100°C by thermo-oxidative degradation of a polychloroprene having a Mooney viscosity of 35 to 120 (ML 1+4) 100°C at a melt temperature of 40 to 200°C by shearing at a shear rate of 30 to 5000 sec-1 until the desired Mooney viscosity is reached.
2. A process as claimed in claim 1, in which a poly-chloroprene having a Mooney viscosity of 10 to 25 (ML 1+4) 100°C is used.
3. A process as claimed in claims 1 and 2, in which a polychloroprene having a Mooney viscosity of 45 to 100 (ML
1+4) 100°C is degraded.
1+4) 100°C is degraded.
4. A process as claimed in claims 1 to 3, in which the melt is sheared at a temperature of 70 to 185°C.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19893932533 DE3932533C1 (en) | 1989-09-29 | 1989-09-29 | |
| DEP3932533.4 | 1989-09-29 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2026353A1 true CA2026353A1 (en) | 1991-03-30 |
Family
ID=6390473
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2026353 Abandoned CA2026353A1 (en) | 1989-09-29 | 1990-09-27 | Process for the production of polychloroprene of moderate viscosity |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0420006A1 (en) |
| JP (1) | JPH03131601A (en) |
| CA (1) | CA2026353A1 (en) |
| DE (1) | DE3932533C1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102010052287A1 (en) * | 2010-03-25 | 2011-09-29 | Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. | Modified polyolefins |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2338286A (en) * | 1941-05-03 | 1944-01-04 | Us Rubber Co | Processing of elastic polychloroprene |
| DE3234318A1 (en) * | 1982-09-16 | 1984-03-22 | Bayer Ag, 5090 Leverkusen | POLYCHLOROPRENE MIXTURES AND THEIR USE |
| CA1221497A (en) * | 1982-11-10 | 1987-05-05 | Douglas C. Edwards | Process for polymer production |
| US4614772A (en) * | 1984-10-29 | 1986-09-30 | Polysar Limited | Low molecular weight polymer process |
-
1989
- 1989-09-29 DE DE19893932533 patent/DE3932533C1/de not_active Expired - Lifetime
-
1990
- 1990-09-18 EP EP90117922A patent/EP0420006A1/en not_active Withdrawn
- 1990-09-25 JP JP25205790A patent/JPH03131601A/en active Pending
- 1990-09-27 CA CA 2026353 patent/CA2026353A1/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| EP0420006A1 (en) | 1991-04-03 |
| JPH03131601A (en) | 1991-06-05 |
| DE3932533C1 (en) | 1991-05-08 |
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