GB1595603A

GB1595603A - Thermoplastic compositions based on polyolefin rubbers and containing carbon black

Info

Publication number: GB1595603A
Application number: GB52196/77A
Authority: GB
Original assignee: Chemische Werke Huels AG
Current assignee: Huels AG
Priority date: 1976-12-17
Filing date: 1977-12-15
Publication date: 1981-08-12
Also published as: CA1090934A; JPS5375251A; BE861954A; NL7713991A; DE2657274A1; FR2374359A1

Description

(54) THERMOPLASTIC COMPOSITIONS BASED ON POLYOLEFIN RUBBERS AND CONTAINING CARBON BLACK (71) We, CHEMISCHE WERKE HURLS AKTIENGESELLSCHAFT, a German Company, of 4370 Marl, 1 Federal Republic of Germany, do hereby declare the invention, for which we pray that a Patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following Statement: This invention relates to thermoplastic composition based on polyolefin rubbers and containing carbon black and to their use for the production of mouldings, particularly web and sheeting, having low water vapour permeability and at the same time low water absorption.

It is known that thermoplastic materials may be used, for example in the form of web or sheeting, for sealing against moisture. They may be united either by heat sealing or by a swelling agent or special adhesive to form larger sealing surfaces and either laid loosely on the substructure of, for example, concrete, wood, bitumen or air-containing thermal insulating material or stuck all over or at isolated places by special sheet adhesives to the said substructure.

To provide a seal against flowing or static water a thickness of the material of from 1 to 2 mm and the presence of a closed surface are sufficient. Particularly in building construction, for example in sealing flat roofs, there are used for keeping the necessary layers of thermal insulation dry so-called vapour-lock sheeting which has to have a specific minimal resistance to the diffusion of water vapour. It is important that the sheeting which insulates the thermal insulating layer from the moisture of the building has a lower water vapour diffusion than the sealing membrane situated above the thermal insulation for protection against rain. This precludes accumulation of moisture in or on the thermal insulation layer and consequent loss or diminution of its function.

It is however often required of sheeting or web used for insulating purposes that it should have -in addition to low water vapour permeabilitya low water absorption because the durability behaviour and the life in relation to the corrosive aqueous liquids encountered in some regions of use, for example in the region of structural work below ground, is considerably better in the case of low water absorption.

The present invention therefore seeks to develop a thermoplastic material which, particularly in the form of web or sheeting, has a low water vapour permeability and at the same time a low water absorption. Moreover it should naturally have the properties which are essential in any case for the use of such material for the production of insulating web or sheeting, namely favourable rheological behaviour, good heat-sealing properties, adequate mechanical properties and also resistance to the effects of weather and aggressive media and thermo-mechanical influences at high and low temperatures.

According to the invention there is provided a thermoplastic composition which is free from crosslinking and vulcanising agents and comprises: (a) 100 parts by weight of a polyolefin rubber; (b) from 15 to 50 parts by weight of an at least partially crystalline polyolefin; (c) from 30 to 140 parts by weight of a carbon black, and optionally (d) up to 150 parts by weight of a bitumen and/or a mineral oil, and/or (e) up to 360 parts by weight of calcium carbonate or siliceous chalk (as hereinafter defined).

Our copending GB patent application No. 52198/77 (Serial No. 1595604) describes and claims similar compositions distinguished by a higher proportion of the at least partially crystalline polyolefin.

The polyolefin rubber which forms the basis of the thermoplastic compositions according to the invention is suitably a polymer prepared from ethylene and one or more a-olefins of three to eight carbon atoms, particularly propylene, with or without one or more multi-enes, by means of a Ziegler-Natta catalyst which may additionally contain an activator and a modifier, in solution or dispersion, at a temperature of from -30"C to +1000C, for example by the method of DT-OS 1,570,352, 1,595,442 or 1,720,450 and also DT-OS 2,427,343.

Preferred polyolefin rubbers are either saturated materials consisting of 15 to 90% by weight, preferably 30 to 75% by weight, of ethylene units and 85 to 10% by weight, preferably 70 to 25% by weight, of propylene and/or butene-(l) units or unsaturated materials consisting of ethylene units and propylene or butene-( 1) units in the above amounts and additionally of multi-ene units in such an amount that 0.5 to 30 double bonds are contained per 1000 carbon atoms in the rubber. Particularly preferred multi-enes include cis - hexadiene - (1,4), dicyclopentadiene, 5 methylene - 2 - norbornene, 5 - ethylidene - 2 - norbornene and 5 isopropylidene - 2 - norbornene.

The at least partially crystalline polyolefins which are incorporated in the compositions according to the invention in an amount of from 15 to 50 parts by weight, preferably from 20 to 40 parts by weight, per 100 parts by weight of polyolefin rubber may for example be a crystalline or partly crystalline polyethylene having a density of from 0.910 to 0.975 g/cm3, an RSV value (measured at 135do in decalin (decahydronaphthalene)) of from 0.5 to 3.3 dl/g and a melt index of from 0.2 to 50 g/10 min. It is also possible to use partly crystalline copolymers of ethylene with another a-olefin.Also suitable are crystalline and partly crystalline homopolymers and copolymers (with other a-olefins and preferably with ethylene) of propylene or butene-(l), namely homopolymers and copolymers of propylene having densities of from 0.90 to 0.910 g/cm3 RSV values (measured at 135"C in decalin) of 1.0 and 10 dl/g and melt indices of 0.1 to 50 g/10 min, and homopolymers and copolymers of butene-(l) having densities of from 0.910 to 0.925 g/cm3, RSV values (measured at 1350C in decalin) of 1.0 to 10 dl/g and melt indices of 0.1 to 100 g/10 min.

To improve the heat-sealing properties of mouldings prepared from the compositions according to the invention it is also possible to use - in addition to the at least partially crystalline polyolefina small amount (up to about one-third of the weight of the at least partially crystalline polyolefin) of atactic polypropylene and/or polybutene-l having a density of 0.86 g/cm3 and RSV values (measured at 135"C in decalin) of 0.1 to 3.0 dl/g.

The carbon black may be a material prepared by the furnace method, especially of the types FEF (fast extruding furnace black), GPF (general purpose furnace black), HMF (high modulus furnace black) APF (all purpose furnace black), HAF (high abrasion furnace black), FT (fine thermal black), MT (medium thermal black) and SRF (semi-reinforcing furnace black). The carbon black is incorporated in the compositions according to the invention in an amount of from 30 to 140 parts by weight, preferably from 40 to 120 parts by weight, per 100 parts by weight of polyolefin rubber. The compositions may also contain as further fillers up to 360 parts by weight, generally from 3 to 350 parts by weight and preferably from 30 to 300 parts by weight, per 100 parts by weight of polyolefin rubber of calcium carbonate and/or siliceous chalk.The calcium carbonate may be a natural, ground chalk pigment, for example, or it may be a precipitated calcium carbonate.

Siliceous chalk is a natural inorganic material composed principally of silica, with a smaller amount of kaolinite. It occurs in the Neuburg area of Germany and is sometimes known as Neuberg chalk. It is sold in Germany under the trade marks Kieselkreide, Silitin and Silikolloid (see Kautschuk und Gummi, 10/1953, pages WT 205-WT 210). Both the calcium carbonate and the siliceous chalk may have been coated for example with a fatty acid derivative, and may be in the form customarily used in processing rubber.

Finally the compositions according to the invention may have incorporated in them up to 150 parts by weight, generally from 5 to 120 parts by weight and preferably from 25 to 100 parts by weight, of a bitumen or mineral oil, per 100 parts by weight of polyolefin rubber. Suitable bitumens include liquid to solid distillation residues from petroleum refining consisting mainly of highly condensed hydrocarbons; their structure may be partially changed for example by oxidation (blown bitumens).

Suitable mineral oils are those having viscosities of from 50 to 5000 centistokes at 20"C and preferably of from 200 to 3000 centistokes at 200C and a density of 0.84 to 0.98 g/cm3. The oils may contain paraffinic carbon atoms and also naphthenic or aromatic carbon atoms.

Production of the thermoplastic compositions according to the invention may be carried out for example in a commercial internal mixer with floating weight, with or without heating. The period required for homogenisation depends on the make-up of the composition, the constructional features of the mixing plant and of the further processing units and the process conditions chosen, e.g. the temperature of the material (generally from SOC to 2200C and preferably from 80 to 1500C), the extent to which the internal mixer is filled (generally from 1.0 to 1.8 and preferably from 1.2 to 1.5 based on its effective volume) and the speed of the rotor (generally up to 100 and preferably from 10 to 40 rpm), and is generally from I to 100 minutes and preferably 35 minutes.After adequate homogenisation the material, usually having a temperature of from 50 to 2200 C, is discharged. When the mixture contains a high concentration of bitumen it may be necessary to cool it prior to discharge in order to prevent considerable adhesion to casing and rotors (which may prevent substantially the discharge of the material). A suitable cooling period in such cases is from I to 30 minutes and preferably from 3 to 15 minutes.

The material discharged from the internal mixer may then be converted into strips or strings, for example through a pair of rollers or a unit driven by a screw, and either granulated or transferred immediately to a further processing unit. This further processing unit which serves particularly for the production of the web or sheeting may be for example a calender, an extruder with a flat sheeting die or a socalled roller-head plant. It may be provided with means for applying or introducing carrier materials, as for example fleece of synthetic fibres and glass cloth.

The composition according to the invention are distinguished by good water vapour permeability and at the same time low water absorption and which is also distinguished by good strength at elevated temperatures may be used, especially in the form of web or sheeting, both in superstructures (for example for sealing buildings having flat roofs) and in substructures (for example for linings for collecting basins, holding tanks, settling tanks, storage basins and for laying out pools, canals and artificial lakes). Other applications are as a sealing sheeting for breaches, tunnels, subways and underpasses and for bridge building and skyscraper sealing in areas of subsoil water.

The following Examples serve to illustrate the present invention.

Example 1 In a laboratory kneader of the Werner & Pfleiderer GK2 type having an effective volume of 2 litres with a ram an ethylene-propylene-diene rubber identified as EPDM I (diene=ethylidene norbornene; 30% by weight of propylene; 8 double bonds per 1000 carbon atoms; My 1+4 (at 1000C)=87; polymer crude strength=130 kp/cm2) is mixed with the following products according to the stated mixing periods, using a temperature of 90"C at the outlet from the kneader and a rotor speed of 50 rpm.

Time Mixing procedure (minutes) introduction of 703 g of EPDMI I 0 introduction of 703 g of bitumen B 85/25 introduction of 633 g of FEF carbon black introduction of 1407 g of chalk introduction of 211 g of polyethylene (density 0.945 g/cm3, RSV 1.45 dl/g, melt index 7 g/10 min) 3 ram cleaned 4 discharge 9 The homogeneous material is discharged with a material temperature of 1 500C and then converted on a laboratory roll mill having a surface temperature of 50 C into a rough sheet which is cut into strips or granulated.

The strips or granules are converted into web of a thickness of 1 mm in a Kleinwefer laboratory extruder with a flat die 300 mm in width arranged in front and a two-roll smoothing calender arranged behind. Portions taken from this web are investigated according to DIN 52122 for water vapour permeability and according to DIN 53495, method A, for water absorption. The water absorption after a storage period of 24 hours is 0.15% and after 200 hours is 0.25% by weight.

The water vapour permeability resistance factor, calcu!ated according to DIN 52615 is y=145,000.

Example 2 Example 1 is repeated with the difference that 1407 g of siliceous chalk is used instead of chalk and the material is discharged at a material temperature of 160"C.

Strips also prepared as described in Example 1 are shaped into web on a 4-roll laboratory calender. Test boards prepared therefrom are measured according to the DIN test methods given in Example 1. Water absorption after 24 hours: 0.3% by weight. Water absorption after 200 hours: 0.6% by weight. Water vapour permeability resistance factor: 105,000y.

Example 3 Thermoplastic material is prepared under the conditions specified in Example 1 from the ingredients set out below and prepared within the times specified:

Time Mixing procedure (minutes) introduction of 964 g of EPDM I 0 introduction of 1284 g of SRF black introduction of 268 g of naphth. mineral oil introduction of 428 g of polyethylene (density 0.923 g/cm3, melt index 8 g/l0min) 3 ram cleaned 4 discharge 9 The discharge temperature of the material is 155"C. Production and testing of the strips is carried out under the conditions specified in Example 1. The water absorption of the test specimens prepared according to the Example is 0.25 ó by weight after 24 hours and 0.6% by weight after 200 hours. The water vapour permeability resistance factor is ,u=100,000.

Example 4 Under the same conditions as in Example 1 the following ingredients are mixed in the specified times in the specified proportions to form a thermoplastic material.

Time Mixing procedure (minutes) introduction of 1096 g of EPDM I 1 0 introduction of 261 g of bitumen B 80 introduction of 1253 g of SRF black introduction of 417 g of chalk introduction 209 g of polyethylene (density 0.935 g/cm3, melt index 0.5 g/10 min) 3 ram cleaned 4 discharge 9 The discharge temperature of the material is 160"C. The test values for water absorption ascertained under the same conditions as in the previous Examples are 0.3%/0.8% by weight after 24/200 hours. The value 120,000 is determined for the water vapour permeability resistance factor y.

Example 5 The following ingredients are mixed together under the conditions specified for Example 3: Time Mixing procedure (minutes) introduction of 1000 g of EPDM II 0 introduction of 1000 g of SRF black introduction of 450 g of polyethylene (density 0.923 g/cm3, melt index 8 g/10 min) 3 ram cleaned 4 discharge 9 The EPDM II used here differs from EPDM I in its ML,+4 value, which is 45, and its polymer crude strength which is 50 kp/cm2. The discharge temperature of the material is 158"C. Water absorption and water vapour permeability are determined analogously to Example 3. Water absorption after 24 hours is 0.28% by weight and after 200 hours is 0.7% by weight. The water vapour permeability resistance factor is y= 114,000.

WHAT WE CLAIM IS: 1. A thermoplastic composition free from crosslinking and vulcanising agents and comprising: (a) 100 parts by weight of a polyolefin rubber, (b) from 15 to 50 parts by weight of an at least partially crystalline polyolefin, and (c) from 30 to 140 parts by weight of a carbon black.

2. A thermoplastic composition according to claim 1, which also contains (d) up to 150 parts by weight of a bitumen or mineral oil per 100 parts by weight of polyolefin rubber.

3. A thermoplastic composition according to claim 1 or 2, which also contains (e) up to 360 parts by weight of calcium carbonate or siliceous chalk (as hereinbefore defined) per 100 parts by weight of polyolefin rubber.

4. A thermoplastic composition according to any of claims 1 to 3, wherein the polyolefin rubber is a polymer of from 15 to 90% by weight of ethylene, from 85 to 10% by weight of propylene and/or butene-(l), and optionally sufficient of a multiene to provide from 0.5 to 30 double bonds per 1000 carbon atoms in the rubber.

5. A thermoplastic composition according to any of claims 1 to 4, wherein the at least partially crystalline polyolefin is a polyethylene having a density of from 0.910 to 0.975 g/cm3, and RSV value (measured at 1350C in decahydronaphthalene) of from 0.5 to 3.3 dl/g and a melt index of from 0.2 to 50 g/10 min.

6. A thermoplastic composition according to any of claims 1 to 5, which also contains up to one third of the weight of the at least partially crystalline polyolefin of atactic polypropylene and/or polybutene-(l) having a density of 0.86 g/cm3 and or RSV value (measured at 1350C in decahydronaphthalene) of from 0.1 to 3.0 dl/g.

7. A thermoplastic composition according to any of claims I to 6, containing 100 parts by weight of component (a), from 20 to 40 parts by weight of component (b), from 40 to 120 parts by weight of component (c), from 25 to 100 parts by weight of component (d) (if present) and from 30 to 300 parts by weight of component (e) (if present).

8. A thermoplastic composition according to claim 1 and substantially as described in any of the foregoing Examples 1 to 5.

9. Mouldings made from a thermoplastic composition according to any of

Claims

claims 1 to 8.

10. Web or sheeting having low water vapour permeability and low water absorption when made from a thermoplastic composition according to any of claims 1 to 8.