CA1275549C - Melt processable rubber/polyethylene compositions - Google Patents
Melt processable rubber/polyethylene compositionsInfo
- Publication number
- CA1275549C CA1275549C CA000513543A CA513543A CA1275549C CA 1275549 C CA1275549 C CA 1275549C CA 000513543 A CA000513543 A CA 000513543A CA 513543 A CA513543 A CA 513543A CA 1275549 C CA1275549 C CA 1275549C
- Authority
- CA
- Canada
- Prior art keywords
- rubber
- composition
- linking agent
- cross
- weight
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
- 239000000203 mixture Substances 0.000 title claims abstract description 57
- 239000004698 Polyethylene Substances 0.000 title claims abstract description 27
- 229920000573 polyethylene Polymers 0.000 title claims abstract description 27
- 229920006343 melt-processible rubber Polymers 0.000 title description 2
- 229920001971 elastomer Polymers 0.000 claims abstract description 54
- 239000005060 rubber Substances 0.000 claims abstract description 54
- 239000002245 particle Substances 0.000 claims abstract description 27
- 239000003431 cross linking reagent Substances 0.000 claims abstract description 25
- -1 polyethylene Polymers 0.000 claims abstract description 25
- 238000000034 method Methods 0.000 claims abstract description 24
- 150000001451 organic peroxides Chemical class 0.000 claims abstract description 14
- 238000001746 injection moulding Methods 0.000 claims abstract description 11
- 229920000092 linear low density polyethylene Polymers 0.000 claims abstract description 10
- 239000004707 linear low-density polyethylene Substances 0.000 claims abstract description 10
- 239000004636 vulcanized rubber Substances 0.000 claims abstract description 7
- 238000010128 melt processing Methods 0.000 claims abstract description 4
- UHOVQNZJYSORNB-UHFFFAOYSA-N Benzene Chemical compound C1=CC=CC=C1 UHOVQNZJYSORNB-UHFFFAOYSA-N 0.000 claims description 12
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 claims description 7
- 239000005977 Ethylene Substances 0.000 claims description 7
- 239000004711 α-olefin Substances 0.000 claims description 7
- 229920001577 copolymer Polymers 0.000 claims description 6
- 238000001125 extrusion Methods 0.000 claims description 6
- ODBCKCWTWALFKM-UHFFFAOYSA-N 2,5-bis(tert-butylperoxy)-2,5-dimethylhex-3-yne Chemical group CC(C)(C)OOC(C)(C)C#CC(C)(C)OOC(C)(C)C ODBCKCWTWALFKM-UHFFFAOYSA-N 0.000 claims description 3
- XMNIXWIUMCBBBL-UHFFFAOYSA-N 2-(2-phenylpropan-2-ylperoxy)propan-2-ylbenzene Chemical compound C=1C=CC=CC=1C(C)(C)OOC(C)(C)C1=CC=CC=C1 XMNIXWIUMCBBBL-UHFFFAOYSA-N 0.000 claims description 3
- 150000001875 compounds Chemical class 0.000 claims description 3
- ZCTAAWQWGMUQNB-UHFFFAOYSA-N 3,6-bis(2-tert-butylperoxypropan-2-yl)-3,6-dimethylcyclohexa-1,4-diene Chemical compound CC(C)(C)OOC(C)(C)C1(C)C=CC(C)(C(C)(C)OOC(C)(C)C)C=C1 ZCTAAWQWGMUQNB-UHFFFAOYSA-N 0.000 claims 2
- 125000000217 alkyl group Chemical group 0.000 claims 2
- 239000000155 melt Substances 0.000 abstract description 2
- 238000002156 mixing Methods 0.000 description 4
- 239000011248 coating agent Substances 0.000 description 3
- 238000000576 coating method Methods 0.000 description 3
- 238000002347 injection Methods 0.000 description 3
- 239000007924 injection Substances 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 239000003795 chemical substances by application Substances 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 238000009863 impact test Methods 0.000 description 2
- 239000008188 pellet Substances 0.000 description 2
- 150000002978 peroxides Chemical class 0.000 description 2
- 229920000642 polymer Polymers 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- KOMNUTZXSVSERR-UHFFFAOYSA-N 1,3,5-tris(prop-2-enyl)-1,3,5-triazinane-2,4,6-trione Chemical compound C=CCN1C(=O)N(CC=C)C(=O)N(CC=C)C1=O KOMNUTZXSVSERR-UHFFFAOYSA-N 0.000 description 1
- BJELTSYBAHKXRW-UHFFFAOYSA-N 2,4,6-triallyloxy-1,3,5-triazine Chemical compound C=CCOC1=NC(OCC=C)=NC(OCC=C)=N1 BJELTSYBAHKXRW-UHFFFAOYSA-N 0.000 description 1
- 101100072702 Drosophila melanogaster defl gene Proteins 0.000 description 1
- 239000004743 Polypropylene Substances 0.000 description 1
- 239000003963 antioxidant agent Substances 0.000 description 1
- IAQRGUVFOMOMEM-UHFFFAOYSA-N butene Natural products CC=CC IAQRGUVFOMOMEM-UHFFFAOYSA-N 0.000 description 1
- 238000013329 compounding Methods 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 239000012141 concentrate Substances 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 238000004132 cross linking Methods 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 239000012442 inert solvent Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 239000011499 joint compound Substances 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 239000000049 pigment Substances 0.000 description 1
- 229920002589 poly(vinylethylene) polymer Polymers 0.000 description 1
- 239000004800 polyvinyl chloride Substances 0.000 description 1
- 229920000915 polyvinyl chloride Polymers 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 239000004576 sand Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 239000003381 stabilizer Substances 0.000 description 1
- 239000004575 stone Substances 0.000 description 1
- 125000000999 tert-butyl group Chemical group [H]C([H])([H])C(*)(C([H])([H])[H])C([H])([H])[H] 0.000 description 1
- 229920001169 thermoplastic Polymers 0.000 description 1
- 239000000326 ultraviolet stabilizing agent Substances 0.000 description 1
- 238000004073 vulcanization Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L19/00—Compositions of rubbers not provided for in groups C08L7/00 - C08L17/00
- C08L19/003—Precrosslinked rubber; Scrap rubber; Used vulcanised rubber
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
- C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
- C08L23/04—Homopolymers or copolymers of ethene
- C08L23/08—Copolymers of ethene
- C08L23/0807—Copolymers of ethene with unsaturated hydrocarbons only containing four or more carbon atoms
- C08L23/0815—Copolymers of ethene with unsaturated hydrocarbons only containing four or more carbon atoms with aliphatic 1-olefins containing one carbon-to-carbon double bond
Landscapes
- Chemical & Material Sciences (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Compositions Of Macromolecular Compounds (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A melt processable composition comprising 30 to 90%
by weight of linear low density polyethylene and 10 to 70% by weight of ground vulcanized rubber is disclosed. The rubber has a particle size of less than about 1.5 mm and such particles are coated with an organic peroxide cross-linking agent. The polyethylene has a density of 0. 915 to 0. 925 g/cm3. The composition may be formed into articles using melt processing techniques e.g. injection moulding. The articles may, for example, be mud-flaps for vehicles.
A melt processable composition comprising 30 to 90%
by weight of linear low density polyethylene and 10 to 70% by weight of ground vulcanized rubber is disclosed. The rubber has a particle size of less than about 1.5 mm and such particles are coated with an organic peroxide cross-linking agent. The polyethylene has a density of 0. 915 to 0. 925 g/cm3. The composition may be formed into articles using melt processing techniques e.g. injection moulding. The articles may, for example, be mud-flaps for vehicles.
Description
MELT PROCESSABLE
RUBBER,/POLYETHYLENE COMPOSITIONS
_ _ _ _ .
The present invention relates ~o melt-processable compositions of rubber and polyethylene and especially to such compositions in which the rubber is ground scrap rubber obtained from, for instance~ used automobile tires~
Some motor vehicles, especially trucks and other large vehicles, have rubber mudflaps near the rear of the wheels of the vehicle. These mudflaps are intended to defl~ct downwards water, mud, sand, stones and the like that are thrown up by the wheels of the vehicle as the vehicle travels along a road, thereby reducing the safety hazards of flying objects and the annoyance to motorists of a spray of water, mud and the like.
Mud1aps are normally made from rubber compositions using compression vulcanization processes. While such processes have produced commercially-acceptable products, it is believed that other fabrication processes offer the potential of greater versatility, faster cycle times, bet~er economics and/or improved properties.
Mudflaps and similar products may be manufactured from thermoplastic polymers such as polyethylene, poly-propylene and polyvinyl chloride by melt-forming processes e.g. injection moulding and sheet extrusion. However, such products tend to lack the appearance and flexibility of rubber that is often expected by consumers~
Mudflaps and similar products may also be manufactured from blends of powdered rubber and polyethylene~
The resultant products have the appearance and feel of rubber but have lower resistance to flexural cracking than products made from polyethylene or rubber only.
It has now been found that rubber-like articles of improved physical properties may be manufactured by melt . . , - . .
~7554~
processing compositions of rubber and polyethylene in which the rubber has been coated with an organic peroxide.
Accordingly, the present invention provides a composition comprising:
(a) 30 to 90% by weight of a linear low density polyethylene, said polyethylene having a density in the range of 0.915 to 0.925 g/cm3, and (b) 10-70% by weight o ground vulcanized rubber, said ground rukber having a particle size of less than about 1.5 mm and being coated with 2000 to 10 000 ppm, based on the weight of rubber, of an organic cross-linking agent.
The present invention also provides a process for forming an article having the appearance of rubber, said process comprising ~i) feeding to melt processing apparatus a composition comprising (a) 30 to 90% by weight of a linear low density polyethylene, said polyethylene having a density o~
0.915 to 0.925 g/cm3, and;
(b) 10 to 70% by weight of ground vulcanized rubber, said ground rubber having a particle size of less than about 1.5 mm and being coated with 2000 to 10 000 ppm, based on the weight of rubber, of an organic cross-linking agent, (ii) admixing said composition within said apparatus under melt conditions, and (iii) forming the resultant admixed molten composition into an article.
In preferred embodiments of the composition and process of the present invention, the rubber is ground scrap rubber, especially ground scrap rubber obtained from automobile tires.
The composition of the present invention is comprised of polyethylene, rubber and a cross-linking agent.
The polyethylene is a linear low density polyethylene having a density in the range of 0.915 to 0.925 g/cm3 and is a .
'' ' ' ' ': ,- :, ~
. . - . .
., ' . : .
.. ,. , . ~ - ,- ! . ' : - ' 5~
copolymer of ethylene with at least one alpha-olefin homologue of ethylene, especially a C4 - Clo alpha-olefin.
Examples of such alpha-olefins are butene-l, hexene-l and octene-l. The molecular weight of the polyethylene may be varied over a wide range, depending in particular on the intended end-use of articles fabricated from the composition and the proportions of polyethylene, rubber and cross-linking agent in the composition.
The rubber of the composition is a ground vulcanized rubber. The rubber should be ground to a particle size that will facilitate adequate mixing of the polyethylene and rubber during processing of the composition.
Thus the particle sizes that may be used will depend for instance on the mixing capabilities of the melt processing apparatus, e.g. injection moulding apparatus or extrusion apparatus. The intended end-use of articles formed from the composition may also be a factor because the homogeneity of the composition as formed into an article may affect the properties of that article. The particle size of the rubber should be less than 1.5 mm, especially less than 1.0 mm and in particular less than 0.5 mm. The rubber should be classified so that all, or at least essentially all, of the rubber has a particle size of less than 1.5 mm; larger particles tend to have detrimental effects on properties of the resultant products.
In a preferred embodiment, the ground vulcanized rubber is obtained from autombile tires or the like, especially scrap automobile tires. Such tires may be ground to a suitable particle size for the compositions of the present invention. Techniques for grinding rubber are known in the art.
The compositions of the present invention also contain an organic cross-linking agent, especially an organic peroxide cross-linking agent. The cross-linking agent is coated onto the particles of the ground rubber prior to the ' , .
~ ~s~
admixing of rubber and polyethylene; addition of peroxide into the composition in the form of a concentrate or directly compounding peroxide into the polyethylene does not result in significant improvements in flex life of the product and/or results in processing difficulties e.g. due to cross-linking of the polymer. It is preferred that the coating of the particles be carried out in a uniform manner, to improve the uniformity of the resultant product. For instance t the coating may be applied using a solution of cross-linking agent and inert solvent by admixing the solution and rubber particles and subsequently removing the solvent. In a preferred method, the coating is applied using a Henschel* mixer.
The amount o the cross-linking agent may be about 2000 to lO 000 ppm, especially 2500 to 6000 ppm. The preferred cross-linking agents are organic peroxide cross-linking agents, especially a bis(tert. alkyl peroxy alkyl) benzene, dicumyl peroxide and/or an acetylenic diperoxy compound. For instance, the cross-linking agent may be 2,5-dimethyl-2,5-di(t-butylperoxy) hexyne-3 which is available commercially under the trade mark Lupersol 130 from Pennwalt Corp. of Buffalo, New York, U.S.A~ Alternatively, the cross-linking agent may be 2,5-dimethyl-2,5 bis ~tert-butyl peroxyisopropyl) benzene which is available commercially under the trade mark Vulcup from Hercules Incorporated. A co-curing agent may also be incorporated into the composition e.g~ in association with the cross-linking agent. Examples of co-curing agents include triallyl cyanurate, triallyl isocyanurate and 1,2-polybutadiene.
The compositions of the present invention may also contain stabilizers e.g. antioxidants and/or ultra violet stabilizers, pigments, fillers and the like, as is known for rubber compositions.
The compositions contain 30 to 90% by weight of the linear low density polyethylene and 10 to 70% by weight of * denotes trade mark - ' ,, ' ~ ~--.
. .
- . , : .
~.~75~4~
the rubber. In preferred embodiments the compositions contain 40 to 60% by weight of polyethylene and 40 to 60~ by weight of rubber. However, it is to be understood that the relative amounts of polyethylene and rubber, and the type of polyethylene, will depend in particular on the properties required in the articles fabricated from the compositions.
The compositions of the present invention are intended to be fabricated into articles using an injection moulding process, especially for the manufacture of articles that have the appearance of being fabricated from rubber.
Such articles include mudflaps and other protective devices for use on motor vehicles, especially trucks and other large vehicles.
In an injection moulding process, the compositions are admixed under melt conditions. Although the compositions could be so admixed prior to being fed to the injection moulding apparatus, it is preferred that the admixing occur in the injec~ion moulding apparatus immediately prior to injection of the admixed composition into the mould of the apparatus. The amount of admixing should be sufficient to provide a degree of homogeneity in the moulded article subsequently obtained that is commensurate with the intended end-use of the article; homogeneity is one factor that is pertinent to the properties of the moulded article. Thus~
apart from the mixing characteristics of the injection moulding apparatus, matters such as the particle size of the components of the composition, the relative particle sizes between different components and the uniformity of ~he particle sizes e.g. particle size distribution, of the components may be important with respect to the properties of the articles that are obtained. Such factors will be understood by those skilled in the art.
The compositions of the present invention are also intended for use in melt processes other than injection moulding. For instance, the compositions may be fed to extrusion apparatusl especially extrusion apparatus for the ~ . . ..
, .
~7~j5~s3 manufacture of sheet products. Mixing characteristics o~ the extrusion apparatus, particle sizes of the components of the composition, relative particle sizes between different components and the uniformity of the particle sizes, e.g.
particle size distribution, may be important with respect to the properties of the articles that are obtained.
Articles fabricated from the compositions of the present invention may be used in a variety of end uses. In particular, the articles may be in the form of mudElaps for vehicles.
The present invention is illustrated by the following examples.
Example I
A number of compositions of the present invention and comparative compositions were prepared. The polyethylene was in the form of pellets. The rubber was obtained from scrap automobile tires and had been ground to a particle size of lo O mm. Organic peroxide, if present, had been coated onto the rubber particles, prior to admixing of rubber and polyethylene, in a Henschel mixer.
To test the properties of the compositions, so~called "tensile bars" were prepared. These tensile bars had a length of 130 mm, a width of 13 mm and a thickness of 3mm, and were moulded on an ~ngel* injection moulding machine from a dry blend of polyethylene pellets and rubber powder. In preparing the sample tensile bars, the melt temperature used was 220C, which was selected so as to activate any organic peroxide present in the composition being moulded while maintaining decomposition of the rubber at an acceptable level. The screw speed and back pressure on the injection moulding apparatus were both set at the maximum for the apparatus to maximise the degree of polymer/rubber homogeneity. Mould closure time was kept to a minimum to reduce any tendency for the rubber to decompose.
The injection moulded tensile bars were subjected to the following tests:
* denotes trade mark .: : . .
.
~75~ 3 (a) Flex test O~ The bars were flexed to 90 degrees on each side of the axis of the bars, at ambient temperature and at a rate of 42 cycles/minute. The bars were considered to have failed when a crack of more than 3mm in length had appeared at the point of flexure of the bars.
(b) Notched Flex test .,. The procedure described above for the flex test was repeated except that a slit having a depth of 3 mm was cut into one side of the bars at the point of flexure. The bars were considered to have failed when this cut had grown by 3 mm in length.
(c) Tensile Impac~ test ... Type L tensile impa_t bars were cut from the injection moulded bars, according to the procedure of ASTM D-1822-68 . The tensile impact test was carried out at -40C.
The results obtained are given in Table I.
' . , ' ' .
., .
~755~
Table I
Run No. 1 2 3 4 5 6 7 Polyethylene* 100 50 50 50 50 50 50 (parts by weight) Rubber - 50 50 50 50 50 50 (parts by weight) Organic Peroxide** - - 500 800 60003300 3000 (ppm) Flex Test 3200 1000 750 1450 34003175 200 (cycles to failure) Notched Flex Test 900 300 - - 900 900 (cycles to failure) Tensile Impact test 14 20 NA NA 17 25 ( Joules/cm2 ) * SCLAIR 2107 ethylene/butene copolymer, density 0.924 g/cm3l melt index 5.1 dg/min.
** Lupersol 130 organic peroxide.
N~ = not available Note: Runs 1-4 are comparative examples.
In Run 7, the polyethylene and rubber were poorly mixed.
- ~, ' . --' , ~ ' ' ' - ~ . ..
- - ' : ' .
RUBBER,/POLYETHYLENE COMPOSITIONS
_ _ _ _ .
The present invention relates ~o melt-processable compositions of rubber and polyethylene and especially to such compositions in which the rubber is ground scrap rubber obtained from, for instance~ used automobile tires~
Some motor vehicles, especially trucks and other large vehicles, have rubber mudflaps near the rear of the wheels of the vehicle. These mudflaps are intended to defl~ct downwards water, mud, sand, stones and the like that are thrown up by the wheels of the vehicle as the vehicle travels along a road, thereby reducing the safety hazards of flying objects and the annoyance to motorists of a spray of water, mud and the like.
Mud1aps are normally made from rubber compositions using compression vulcanization processes. While such processes have produced commercially-acceptable products, it is believed that other fabrication processes offer the potential of greater versatility, faster cycle times, bet~er economics and/or improved properties.
Mudflaps and similar products may be manufactured from thermoplastic polymers such as polyethylene, poly-propylene and polyvinyl chloride by melt-forming processes e.g. injection moulding and sheet extrusion. However, such products tend to lack the appearance and flexibility of rubber that is often expected by consumers~
Mudflaps and similar products may also be manufactured from blends of powdered rubber and polyethylene~
The resultant products have the appearance and feel of rubber but have lower resistance to flexural cracking than products made from polyethylene or rubber only.
It has now been found that rubber-like articles of improved physical properties may be manufactured by melt . . , - . .
~7554~
processing compositions of rubber and polyethylene in which the rubber has been coated with an organic peroxide.
Accordingly, the present invention provides a composition comprising:
(a) 30 to 90% by weight of a linear low density polyethylene, said polyethylene having a density in the range of 0.915 to 0.925 g/cm3, and (b) 10-70% by weight o ground vulcanized rubber, said ground rukber having a particle size of less than about 1.5 mm and being coated with 2000 to 10 000 ppm, based on the weight of rubber, of an organic cross-linking agent.
The present invention also provides a process for forming an article having the appearance of rubber, said process comprising ~i) feeding to melt processing apparatus a composition comprising (a) 30 to 90% by weight of a linear low density polyethylene, said polyethylene having a density o~
0.915 to 0.925 g/cm3, and;
(b) 10 to 70% by weight of ground vulcanized rubber, said ground rubber having a particle size of less than about 1.5 mm and being coated with 2000 to 10 000 ppm, based on the weight of rubber, of an organic cross-linking agent, (ii) admixing said composition within said apparatus under melt conditions, and (iii) forming the resultant admixed molten composition into an article.
In preferred embodiments of the composition and process of the present invention, the rubber is ground scrap rubber, especially ground scrap rubber obtained from automobile tires.
The composition of the present invention is comprised of polyethylene, rubber and a cross-linking agent.
The polyethylene is a linear low density polyethylene having a density in the range of 0.915 to 0.925 g/cm3 and is a .
'' ' ' ' ': ,- :, ~
. . - . .
., ' . : .
.. ,. , . ~ - ,- ! . ' : - ' 5~
copolymer of ethylene with at least one alpha-olefin homologue of ethylene, especially a C4 - Clo alpha-olefin.
Examples of such alpha-olefins are butene-l, hexene-l and octene-l. The molecular weight of the polyethylene may be varied over a wide range, depending in particular on the intended end-use of articles fabricated from the composition and the proportions of polyethylene, rubber and cross-linking agent in the composition.
The rubber of the composition is a ground vulcanized rubber. The rubber should be ground to a particle size that will facilitate adequate mixing of the polyethylene and rubber during processing of the composition.
Thus the particle sizes that may be used will depend for instance on the mixing capabilities of the melt processing apparatus, e.g. injection moulding apparatus or extrusion apparatus. The intended end-use of articles formed from the composition may also be a factor because the homogeneity of the composition as formed into an article may affect the properties of that article. The particle size of the rubber should be less than 1.5 mm, especially less than 1.0 mm and in particular less than 0.5 mm. The rubber should be classified so that all, or at least essentially all, of the rubber has a particle size of less than 1.5 mm; larger particles tend to have detrimental effects on properties of the resultant products.
In a preferred embodiment, the ground vulcanized rubber is obtained from autombile tires or the like, especially scrap automobile tires. Such tires may be ground to a suitable particle size for the compositions of the present invention. Techniques for grinding rubber are known in the art.
The compositions of the present invention also contain an organic cross-linking agent, especially an organic peroxide cross-linking agent. The cross-linking agent is coated onto the particles of the ground rubber prior to the ' , .
~ ~s~
admixing of rubber and polyethylene; addition of peroxide into the composition in the form of a concentrate or directly compounding peroxide into the polyethylene does not result in significant improvements in flex life of the product and/or results in processing difficulties e.g. due to cross-linking of the polymer. It is preferred that the coating of the particles be carried out in a uniform manner, to improve the uniformity of the resultant product. For instance t the coating may be applied using a solution of cross-linking agent and inert solvent by admixing the solution and rubber particles and subsequently removing the solvent. In a preferred method, the coating is applied using a Henschel* mixer.
The amount o the cross-linking agent may be about 2000 to lO 000 ppm, especially 2500 to 6000 ppm. The preferred cross-linking agents are organic peroxide cross-linking agents, especially a bis(tert. alkyl peroxy alkyl) benzene, dicumyl peroxide and/or an acetylenic diperoxy compound. For instance, the cross-linking agent may be 2,5-dimethyl-2,5-di(t-butylperoxy) hexyne-3 which is available commercially under the trade mark Lupersol 130 from Pennwalt Corp. of Buffalo, New York, U.S.A~ Alternatively, the cross-linking agent may be 2,5-dimethyl-2,5 bis ~tert-butyl peroxyisopropyl) benzene which is available commercially under the trade mark Vulcup from Hercules Incorporated. A co-curing agent may also be incorporated into the composition e.g~ in association with the cross-linking agent. Examples of co-curing agents include triallyl cyanurate, triallyl isocyanurate and 1,2-polybutadiene.
The compositions of the present invention may also contain stabilizers e.g. antioxidants and/or ultra violet stabilizers, pigments, fillers and the like, as is known for rubber compositions.
The compositions contain 30 to 90% by weight of the linear low density polyethylene and 10 to 70% by weight of * denotes trade mark - ' ,, ' ~ ~--.
. .
- . , : .
~.~75~4~
the rubber. In preferred embodiments the compositions contain 40 to 60% by weight of polyethylene and 40 to 60~ by weight of rubber. However, it is to be understood that the relative amounts of polyethylene and rubber, and the type of polyethylene, will depend in particular on the properties required in the articles fabricated from the compositions.
The compositions of the present invention are intended to be fabricated into articles using an injection moulding process, especially for the manufacture of articles that have the appearance of being fabricated from rubber.
Such articles include mudflaps and other protective devices for use on motor vehicles, especially trucks and other large vehicles.
In an injection moulding process, the compositions are admixed under melt conditions. Although the compositions could be so admixed prior to being fed to the injection moulding apparatus, it is preferred that the admixing occur in the injec~ion moulding apparatus immediately prior to injection of the admixed composition into the mould of the apparatus. The amount of admixing should be sufficient to provide a degree of homogeneity in the moulded article subsequently obtained that is commensurate with the intended end-use of the article; homogeneity is one factor that is pertinent to the properties of the moulded article. Thus~
apart from the mixing characteristics of the injection moulding apparatus, matters such as the particle size of the components of the composition, the relative particle sizes between different components and the uniformity of ~he particle sizes e.g. particle size distribution, of the components may be important with respect to the properties of the articles that are obtained. Such factors will be understood by those skilled in the art.
The compositions of the present invention are also intended for use in melt processes other than injection moulding. For instance, the compositions may be fed to extrusion apparatusl especially extrusion apparatus for the ~ . . ..
, .
~7~j5~s3 manufacture of sheet products. Mixing characteristics o~ the extrusion apparatus, particle sizes of the components of the composition, relative particle sizes between different components and the uniformity of the particle sizes, e.g.
particle size distribution, may be important with respect to the properties of the articles that are obtained.
Articles fabricated from the compositions of the present invention may be used in a variety of end uses. In particular, the articles may be in the form of mudElaps for vehicles.
The present invention is illustrated by the following examples.
Example I
A number of compositions of the present invention and comparative compositions were prepared. The polyethylene was in the form of pellets. The rubber was obtained from scrap automobile tires and had been ground to a particle size of lo O mm. Organic peroxide, if present, had been coated onto the rubber particles, prior to admixing of rubber and polyethylene, in a Henschel mixer.
To test the properties of the compositions, so~called "tensile bars" were prepared. These tensile bars had a length of 130 mm, a width of 13 mm and a thickness of 3mm, and were moulded on an ~ngel* injection moulding machine from a dry blend of polyethylene pellets and rubber powder. In preparing the sample tensile bars, the melt temperature used was 220C, which was selected so as to activate any organic peroxide present in the composition being moulded while maintaining decomposition of the rubber at an acceptable level. The screw speed and back pressure on the injection moulding apparatus were both set at the maximum for the apparatus to maximise the degree of polymer/rubber homogeneity. Mould closure time was kept to a minimum to reduce any tendency for the rubber to decompose.
The injection moulded tensile bars were subjected to the following tests:
* denotes trade mark .: : . .
.
~75~ 3 (a) Flex test O~ The bars were flexed to 90 degrees on each side of the axis of the bars, at ambient temperature and at a rate of 42 cycles/minute. The bars were considered to have failed when a crack of more than 3mm in length had appeared at the point of flexure of the bars.
(b) Notched Flex test .,. The procedure described above for the flex test was repeated except that a slit having a depth of 3 mm was cut into one side of the bars at the point of flexure. The bars were considered to have failed when this cut had grown by 3 mm in length.
(c) Tensile Impac~ test ... Type L tensile impa_t bars were cut from the injection moulded bars, according to the procedure of ASTM D-1822-68 . The tensile impact test was carried out at -40C.
The results obtained are given in Table I.
' . , ' ' .
., .
~755~
Table I
Run No. 1 2 3 4 5 6 7 Polyethylene* 100 50 50 50 50 50 50 (parts by weight) Rubber - 50 50 50 50 50 50 (parts by weight) Organic Peroxide** - - 500 800 60003300 3000 (ppm) Flex Test 3200 1000 750 1450 34003175 200 (cycles to failure) Notched Flex Test 900 300 - - 900 900 (cycles to failure) Tensile Impact test 14 20 NA NA 17 25 ( Joules/cm2 ) * SCLAIR 2107 ethylene/butene copolymer, density 0.924 g/cm3l melt index 5.1 dg/min.
** Lupersol 130 organic peroxide.
N~ = not available Note: Runs 1-4 are comparative examples.
In Run 7, the polyethylene and rubber were poorly mixed.
- ~, ' . --' , ~ ' ' ' - ~ . ..
- - ' : ' .
Claims (18)
1. A composition comprising:
(a) 30 to 90% by weight of a linear low density polyethylene, said polyethylene having a density in the range of 0.915 to 0.925 g/cm3, and (b) 10 to 70% by weight of ground vulcanized rubber, said ground rubber being in the form of particles having a size of less than about 1.5 mm and coated with 2000 to 10 000 ppm, based on the weight of rubber, of an organic cross-linking agent.
(a) 30 to 90% by weight of a linear low density polyethylene, said polyethylene having a density in the range of 0.915 to 0.925 g/cm3, and (b) 10 to 70% by weight of ground vulcanized rubber, said ground rubber being in the form of particles having a size of less than about 1.5 mm and coated with 2000 to 10 000 ppm, based on the weight of rubber, of an organic cross-linking agent.
2. The composition of Claim 1 in which the cross-linking agent is an organic peroxide.
3. The composition of Claim 2 in which the rubber is coated with 2500 to 6000 ppm of organic peroxide cross-linking agent.
4. The composition of any one of Claim 1, Claim 2 and Claim 3 in which the particle size of the ground rubber is less than 1.0 mm.
5. The composition of any one of Claim 1, Claim 2 and Claim 3 in which the organic cross-linking agent is selected from the group consisting of a bis(tert. alkyl peroxyalkyl) benzene, dicumyl peroxide and an acetylenic diperoxy compound, and mixtures thereof.
6. The composition of any one of Claim 1, Claim 2 and Claim 3 in which the organic cross-linking agent is 2,5-dimethyl-2,5-di-(tert-butyl peroxy) hexyne-3 or 2,5-dimethyl-2,5 bis(tert-butyl peroxy isopropyl) benzene.
7. The composition of any one of Claim 1, Claim 2 and Claim 3 in which the linear low density polyethylene is a copolymer of ethylene and one C4-C10 alpha-olefin.
8. The composition of any one of Claim 1, Claim 2 and Claim 3 in which the linear low density polyethylene is a copolymer of ethylene and more than one C3-C10 alpha-olefin.
9. A process for forming an article having the appearance of rubber, said process comprising:
(a) feeding to melt processing apparatus a composition comprising (i) 30 to 90% by weight of a linear low density polyethylenet said polyethylene having a density in the range of 0.915 to 0.925 g/cm3, and (ii) 10 to 70% by weight of ground vulcanized rubber, said ground rubber being in the form of particles having a size of less than about 1.5 mm and coated with 2000 to 10 000 ppm, based on the weight of rubber, of an organic cross-linking agent,;
(b) admixing said composition within said apparatus under melt conditions, and (c) forming the resultant admixed composition into an article.
(a) feeding to melt processing apparatus a composition comprising (i) 30 to 90% by weight of a linear low density polyethylenet said polyethylene having a density in the range of 0.915 to 0.925 g/cm3, and (ii) 10 to 70% by weight of ground vulcanized rubber, said ground rubber being in the form of particles having a size of less than about 1.5 mm and coated with 2000 to 10 000 ppm, based on the weight of rubber, of an organic cross-linking agent,;
(b) admixing said composition within said apparatus under melt conditions, and (c) forming the resultant admixed composition into an article.
10. The process of Claim 9 in which the cross-linking agent is an organic peroxide.
11. The process of Claim 10 in which the rubber is coated with 2500 to 6000 ppm of organic peroxide cross-linking agent.
_ 10
_ 10
12. The process of any one of Claim 9, Claim 10 and Claim 11 in which the particle size of the ground rubber is less than 1.0 mm.
13. The process of any one of Claim 9, Claim 10 and Claim 11 in which the organic peroxide cross-linking agent is selected from the group consisting of a bis(tert. alkyl peroxyalkyl) benzene, dicumyl peroxide and an acetylenic diperoxy compound, and mixtures thereof.
14. The process of any one of Claim 9, Claim 10 and Claim 11 in which the organic peroxide cross-linking agent is 2,5-dimethyl-2,5-di-(tert-butyl peroxy) hexyne-3 or 2,5-dimethyl-2,5 bis(tert-butyl peroxy isopropyl) benzene.
15. The process of any one of Claim 9, Claim 10 and Claim 11 in which the linear low density polyethylene is a copolymer of ethylene and one C4-C10 alpha-olefin.
16. The process of any one of Claim 9, Claim 10 and Claim 11 in which the linear low density polyethylene is a copolymer of ethylene and more than one C3-C10 alpha-olefin.
17. The process of any one of Claim 9, Claim 10 and Claim 11 in the form of an injection moulding process.
18. The process of any one of Claim 9, Claim 10 and Claim 11 in the form of a sheet extrusion process.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8517936A GB2177704B (en) | 1985-07-16 | 1985-07-16 | Melt processable rubber/polyethylene compositions |
| GB85.017936 | 1985-07-16 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1275549C true CA1275549C (en) | 1990-10-23 |
Family
ID=10582367
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000513543A Expired - Fee Related CA1275549C (en) | 1985-07-16 | 1986-07-10 | Melt processable rubber/polyethylene compositions |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA1275549C (en) |
| GB (1) | GB2177704B (en) |
-
1985
- 1985-07-16 GB GB8517936A patent/GB2177704B/en not_active Expired
-
1986
- 1986-07-10 CA CA000513543A patent/CA1275549C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| GB8517936D0 (en) | 1985-08-21 |
| GB2177704A (en) | 1987-01-28 |
| GB2177704B (en) | 1989-07-12 |
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