CA1039023A - Process of preparing shaped elastomeric articles - Google Patents
Process of preparing shaped elastomeric articlesInfo
- Publication number
- CA1039023A CA1039023A CA204,694A CA204694A CA1039023A CA 1039023 A CA1039023 A CA 1039023A CA 204694 A CA204694 A CA 204694A CA 1039023 A CA1039023 A CA 1039023A
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- CA
- Canada
- Prior art keywords
- blend
- cured
- thermoplastic resin
- process according
- heated
- 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
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- B29K2021/00—Use of unspecified rubbers as moulding material
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- B29K2995/00—Properties of moulding materials, reinforcements, fillers, preformed parts or moulds
- B29K2995/0037—Other properties
- B29K2995/0049—Heat shrinkable
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
- C08J2321/00—Characterised by the use of unspecified rubbers
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Organic Chemistry (AREA)
- Compositions Of Macromolecular Compounds (AREA)
- Shaping By String And By Release Of Stress In Plastics And The Like (AREA)
- Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)
Abstract
ABSTRACT
Elastomeric articles, e.g. industrial tyres, insert mouldings, or industrial strappings, can be made by a process in which a blend of an EPOM elastomer and a termoplastic resin with an elastomer:resin weight ratio of between 90:10 and 50:50 is mixed and fluxed and compounded with a filler, a plasticizer and a curative, and the blend is shaped and cured, the cured blend is heated to a temperature above the melting point of the thermoplastic resin, the heated blend is deformed, and the blend is the deformed state is cooled to a temperature below the melting point of the thermoplastic resin.
Elastomeric articles, e.g. industrial tyres, insert mouldings, or industrial strappings, can be made by a process in which a blend of an EPOM elastomer and a termoplastic resin with an elastomer:resin weight ratio of between 90:10 and 50:50 is mixed and fluxed and compounded with a filler, a plasticizer and a curative, and the blend is shaped and cured, the cured blend is heated to a temperature above the melting point of the thermoplastic resin, the heated blend is deformed, and the blend is the deformed state is cooled to a temperature below the melting point of the thermoplastic resin.
Description
~{~39~23 This invention relates to a process o~ making heat ~hrinkable elastomeric articles.
It is known to cure blends of ethylene-propylene diene terpolymers (EPDM) and resins to produce an elastomeric blend which can be shaped into various articles. We have now discovered a process which results in elastomeric compositions which compared with the prior art, have greatly improved physical properties (e.g. moduli, tensile strength etc.) and heat shr;nk properties. Furthermore, these compositions are capable of being thermoformed, vacuum formed and cold forged.
According to this inventlon an elastomeric article is prepared by a p~ocess in which a blend of an EPDM elastomer and a thermoplastic resin with an elastomer:resin weight ratio of between 90:10 and 50:50 is mixed and fluxed and compounded with a filler, a plasticizer and a curative, and the blend (i) is either shaped and cured simultaneously or shaped and subsequently cured, (ii) the cured blend is heated to a temperature above the melting po;nt of the thermoplastic resin, (iii) the heated blend is deformed, and (iv) the blend in the deformed state is cooled to a temperature below the melting point of the thermoplastic resin.
Ethylene-propylene-diene terpolymers ~;
are usually prepared by contacting a feed stream contain;ng ethylene, propylene and polymerizable diolefin with a Ziegler catalyst in the presence of an inert saturated C5 to C8 hydrocarbon diluent, e.g. an alkane or cycloalkane, such as n-pentane, isopentane, n-hexane, isohexane or n-octane. The copolymerization is usually carried out at a pressure of 1 to 5 atmospheres. The third monomer iB usually a C6 to C16 non-conjugated diolefin, eOg. 1,5-hexadiene, 1,5-octadiene or a 2-alkyl norbornadiene, such as methylidene norbornene or ethylidene norbornene. The preferred EPDM elastomer has a high ethylene content of at least 55 wt~% in the copolymer.
~ - 2 .,................... : . : . . -.~ .
1~39023 Ths thermoplastic resin present in the blend can be a thermoplastic polyolefin, e.g. low density or high density polyethylene or polypropylene. The preferred polyolefin is low density polyethylene and this is usually made by polymerizing ethylene at high pressure, e.g. 30 to 2500 atmospheres, in the presence of a polymerization catalyst, e.g. an organic peroxide such as lauroyl peroxide.
. .: :: ~
1039C~23 Another suitable polyolefin is low pressure polyethylene which usually has a density of 0.94 to 0.96, and a Molecular weight of from 30,000 to 500,000 as determined by the intrinsic viscosity method. This low pressure polyethylene is made by well-known polymerization methods using a Ziegler catalyst (e.g. AlCl3 and TiC14). Another suitable polyolefin is low pressure isotactic polypropylene polymer which usually has a density of from 0.86 to 0.91, and a molecular weight of from 50,000 to 500,000 as determined by the intrinsic viscosity method. This low pressure polypropylene is made by similar methods as used for making low pressure polyethylene.
Another preferred thermoplastic resin is polyvinyl chloride.
P Other suitable thermoplastic resins are polystyrene, and polyethylene polyvinyl acetate copolymers.
The quantity of thermoplastic resin which is incorporated in the blend is from 10 to 50% of the total weight of elastomer and resin, preferably 15 to 35%, e.g. 20-30% of the total weight of elastomer and thermoplastic resin.
Incorporated in the blend (preferably simultaneously with the mixing of the elastomer and resin) are one or more fillers, p?asticizers and curatives.
Suitable fillers include a carbon black such as furnace or channel carbon black fillers such as silica, silicates, hard clay, soft clay or whiting. Suieable plasticizers include aromatic naphthenic or paraffinic mineral oils. Also if desired a pigment e.g. titanium dioxide, may be incorporated in the blend.
The mixing and fluxing of the blend can be carried out in conventional equipment.
In the first step of the procesæ of the invention the blend of elastomer and resin is either æhaped and cured simultaneously or shaped and thereafter cured. The blend is shaped in conventional equipment for example by extrueion, calendering or mouldlng, and is formed into a sheet~ strip, tube, section, rod or any other desired shape.
' ' .
1~3~(~23 The blend is cured either simultaneously with shaping or after shaping, and the curing can be conventional methods such as steam cure, press cure, liquid curing medium (LCM) ultra high frequency curing (UHF) etc.
The vulcanizing agents may be sulphur accelerator combinations, sulphur donor cure systems, peroxides or phenol-formaldehyde resins. Cross-linking may also be achieved by irradiation techniques.
In the second step of the process of this invention the c~red blend is heated to a temperature above the melting point of the thermoplastic res;n, and this usuall~ means to a temperature of above 100C, e g~ from 150C to 180C~
In the third step of the process of this invention the blend whilst it is hot, i.e. at a temperature above the melting point of the ther plastic resin, is deformed. Deforming, i.e. changing of shape, can be carried out in various ways, e.g. stretching, thermoforming or cold forging~ Such deforming techniques are well-known and are described in more detail later in this specification when describing specific applications of the process of the lnvention.
In the last step the blend in the deformed state is cooled to a temperature below the melting po;nt of the thermoplastic resin. This in practice usually means cooling to a temperature below 50 C, e.g~ ambient temperature. The cooling should preferably be carried out as quickly as is practicable. After cooling the blend is usually released from external stresses and at temperatures below the melting point of the thermoplastic re.8in it is found that blend retains its new shape and dimensions.
Furthermore, the shaped blend exhibits "frozen" elastic memory, which means that if it is heated to a temperature above the melting point of the thermoelastic resin it reverts to its original cured shape, i.e. the shape it had before being deformed. This phenomenon is reversible and so the blend after reverting to its original shape could be reheated and deformed to a new ahape by carrying out steps (ii), (iii) and (iv) of the process of thi~
invention. --....
,: : .- , ~. :.
.
1C13~023 By the process of thls lnvention artlcles can be produced which are elastomeric and which have substantially higher physifal properties such as toughness and tensile strength than the cured blend before it is subjected to steps (ill) and (iv) of the process of this invention.
The process of this invent~on has many commercial applications and various examples of such uses are given below Solid industrial tyres can be slmply produced~ Thus, using for example an EPDM/polyethylene blend this may be cured in a mould having a diameter less than that of the hub. After removing the cured blend from the mould the hot tyre is placed in a simple stretcher, stretched to a diameter greater than that of the hub, and cooled to ambient temperature. The oversized tyre is easily mounted on a variety of hubs with diameters between that of the original mould and that of the stretched tyre. The tyre assembled on the hub is then heated in a hot air oven when the tyre reverts to its original diameter, thus forming a perfect shrink on the hub.
Similar techniques may be used for a variety of insert mouldings and for producing shrinkable O-rings.
There is a large and growing demand for industrial strapping, and the process of this invention enables one to make tough elastomeric strapping from cured elastomer/thermoplastic resin blends. These strappings have elasticity and flexibility together with optional heat shrinkability.
The blend may be compounded, extruded and continuously vulcanized in for example, LCM with immediate, in line, stretching and cooling. The strapping has elastic characteristics combined with very high tensile and heat shrink properties. The strapping may be used with or without resorting to its heat shrink properties.
One important application is the production of shrink tubing~ The tubing is initially produced with a diameter greater than the final diameter requlred by subjectlng the blend to curing, heating, deforming and cooling ln ~he deformed state~ The tubing is then shrunk to ~he required diameter by heatlng. The major uses of shrink tubing are:
(a) the insulation of eLectric connections by sleeves produced from shrink tubing ('D) the repair and reclamation of rubber hoses having a damaged and leaking portion (c) producing external protective lining of buried steel and iron pipelines, and td) producing external protective llning of cylindrical shapes.
Another lmportant application is thermoforming whereby a variety of intricate and large surface area elastomeric art;cles, which otherwise would require very expensive moulding tools and presses, can be economically and simply produced. The raw material for the thermoforming is an elastomerîc sheet (in th;s case EPDM/polyethylene) produced ~o the desired thickness by extrusion or calendering and subsequent vulcani~ation. The cured sheet is then preheated, e.g. to above 120 C, preferably above 160 C, and then placed in a thermoformer or vacuum former, the moulds in both cases being cold. Positive pressure or vacuum respectively, is applied and the article is formed ant cooled at the same time. The economic advantage of the process is due to the fact that practically no blanks are wastedO A moulding reject is easily re-used by reheating the ar~icle to above 160 C wher~ it returns to its origînal shape, i.eO that of the blank. This blank can then be used agalnO
Thermoforming can be used for producing a great variety of products, such as bellows, cups, covers, floor mats, etc.
The cured elastomeric composition prepared by the process of the invention can be used for cold forging. Thus, a fluxed and compounded blend of EPDM and thermoplastic resin wlth suitable curatives is shaped into desired blanks. The shaping may be done using an extruder or a Barwell (TM) preformer. The blanks are .,.::. . :: ; . ~ ~-cured and are fed dlrectly, whilst hot, from the curing stage into the forging press.
During forging the hot, cured blank is subjected to high pressure and takes the form o~
the cold mould. During the forging cycle it is sufficient to cool the outer surface of the article to a degree that will safeguard the dimensional stability whilst the article is removed from the mould. A~ with the thermoforming process there are substantially no moulding rejects. -~
Example Various blends (A, B, C, D and E) were prepared from commercially available EPDM (Vistalo~) and either low-density polyethylene (Idpe) or high-density polyethylene (hdpe). Aiso various other ingred;énts (e.g.
clay, whiting etc) were included. The various components were mixed in an internal mixer and curing agents added in a second pass.
Each of the blends A. B and C were extruded into a tube and a strip and steam cured for 20 minutes at 170 C. Blends D and E were press cured for 20 minutes at 170C.
The composition of the blend~ and their physical proper~ies are g;ven below:
A B C D E
VISTALON 3708 (EPDM) 70 VISTALON 5600.(EPDM~ 70 20 VISTALON 4608 (EPDM) 70 70 70 ldpe 30 30 30 hdpe 30 30 Calcined Clay 100 100 100 Whiting 50 50 100 APF (carbon black) 100 lOO
Paraffinic Process Oil 50 50 30 50 50 Stearic Acid 1~5 Zinc Oxide 4 4 MBTS (benzothiazyl disulphide) 106 30 VU1CAdOn~ 3$~ ~a curative~ 3~0 * Trade Mark - 8 -: - . .. ..
"'` ~ , ' . ':
.. . .
~Q39~?23 Sulphur 0.8 Perkadox 1440 (peroxide cross-linking agent) 6 6 6 6 Activator OC ) co-agents 1.5 1.5 ~ ) for Sartomex 206 ) Perkadox 1440 2 2 Shore Hardness 70 76 70 82 80 Tensile kg/cm 68 70 42 13~ 87 100% Modulus kg/cm 30 59 50 300% Modulus kg/cm2 38 51 33 124 Elongation % 990 720 610 360 220 The cured strips were heated in hot air to 160 C and stretched to 100-250% elongation and cooled in the stretched form by immersion in cold water. The physical properties of the stretched samples were as follows:
Sample A B C D E
20 minutes at 170 C cure steam steam steam Press Press % stretch 200 220 110100 ; 130 110 Shore hardness 63 81 82 77 Tensile kg/cm 160 150 96 270 296 236 100% Modulus 137 80 211 276 Elongation at break % 120 180 180200 120 90 Sim;larly the cured tubes were heated to over 160C and stretched on a mandrel to about tw;ce the original diameter and cooled to room temperature.
The extended forms exhibit dimensional stability at room temperatures and had a characteristic elastomeric behaviour with enhanced toughness and tensile strength. The oriented strip and the stretched tube shrank to their original cured dimensions and shape upon heating to over 100-120 C.
The press-cured pads were heated to 170C and whilst still hot, thermoformed on a simple, cold mould. The cold thermoformed shape retained its dimensions at room temperature and exhib;ted typical elastomer properties.
Upon heating to 130 C the thermoformed part returned completely to its original cured shape.
~7~ad~7Q~ ~ 9 ~
'~`: . : , ' ' i ' ' : . . . ` '~ . . .' " ~ . -
It is known to cure blends of ethylene-propylene diene terpolymers (EPDM) and resins to produce an elastomeric blend which can be shaped into various articles. We have now discovered a process which results in elastomeric compositions which compared with the prior art, have greatly improved physical properties (e.g. moduli, tensile strength etc.) and heat shr;nk properties. Furthermore, these compositions are capable of being thermoformed, vacuum formed and cold forged.
According to this inventlon an elastomeric article is prepared by a p~ocess in which a blend of an EPDM elastomer and a thermoplastic resin with an elastomer:resin weight ratio of between 90:10 and 50:50 is mixed and fluxed and compounded with a filler, a plasticizer and a curative, and the blend (i) is either shaped and cured simultaneously or shaped and subsequently cured, (ii) the cured blend is heated to a temperature above the melting po;nt of the thermoplastic resin, (iii) the heated blend is deformed, and (iv) the blend in the deformed state is cooled to a temperature below the melting point of the thermoplastic resin.
Ethylene-propylene-diene terpolymers ~;
are usually prepared by contacting a feed stream contain;ng ethylene, propylene and polymerizable diolefin with a Ziegler catalyst in the presence of an inert saturated C5 to C8 hydrocarbon diluent, e.g. an alkane or cycloalkane, such as n-pentane, isopentane, n-hexane, isohexane or n-octane. The copolymerization is usually carried out at a pressure of 1 to 5 atmospheres. The third monomer iB usually a C6 to C16 non-conjugated diolefin, eOg. 1,5-hexadiene, 1,5-octadiene or a 2-alkyl norbornadiene, such as methylidene norbornene or ethylidene norbornene. The preferred EPDM elastomer has a high ethylene content of at least 55 wt~% in the copolymer.
~ - 2 .,................... : . : . . -.~ .
1~39023 Ths thermoplastic resin present in the blend can be a thermoplastic polyolefin, e.g. low density or high density polyethylene or polypropylene. The preferred polyolefin is low density polyethylene and this is usually made by polymerizing ethylene at high pressure, e.g. 30 to 2500 atmospheres, in the presence of a polymerization catalyst, e.g. an organic peroxide such as lauroyl peroxide.
. .: :: ~
1039C~23 Another suitable polyolefin is low pressure polyethylene which usually has a density of 0.94 to 0.96, and a Molecular weight of from 30,000 to 500,000 as determined by the intrinsic viscosity method. This low pressure polyethylene is made by well-known polymerization methods using a Ziegler catalyst (e.g. AlCl3 and TiC14). Another suitable polyolefin is low pressure isotactic polypropylene polymer which usually has a density of from 0.86 to 0.91, and a molecular weight of from 50,000 to 500,000 as determined by the intrinsic viscosity method. This low pressure polypropylene is made by similar methods as used for making low pressure polyethylene.
Another preferred thermoplastic resin is polyvinyl chloride.
P Other suitable thermoplastic resins are polystyrene, and polyethylene polyvinyl acetate copolymers.
The quantity of thermoplastic resin which is incorporated in the blend is from 10 to 50% of the total weight of elastomer and resin, preferably 15 to 35%, e.g. 20-30% of the total weight of elastomer and thermoplastic resin.
Incorporated in the blend (preferably simultaneously with the mixing of the elastomer and resin) are one or more fillers, p?asticizers and curatives.
Suitable fillers include a carbon black such as furnace or channel carbon black fillers such as silica, silicates, hard clay, soft clay or whiting. Suieable plasticizers include aromatic naphthenic or paraffinic mineral oils. Also if desired a pigment e.g. titanium dioxide, may be incorporated in the blend.
The mixing and fluxing of the blend can be carried out in conventional equipment.
In the first step of the procesæ of the invention the blend of elastomer and resin is either æhaped and cured simultaneously or shaped and thereafter cured. The blend is shaped in conventional equipment for example by extrueion, calendering or mouldlng, and is formed into a sheet~ strip, tube, section, rod or any other desired shape.
' ' .
1~3~(~23 The blend is cured either simultaneously with shaping or after shaping, and the curing can be conventional methods such as steam cure, press cure, liquid curing medium (LCM) ultra high frequency curing (UHF) etc.
The vulcanizing agents may be sulphur accelerator combinations, sulphur donor cure systems, peroxides or phenol-formaldehyde resins. Cross-linking may also be achieved by irradiation techniques.
In the second step of the process of this invention the c~red blend is heated to a temperature above the melting point of the thermoplastic res;n, and this usuall~ means to a temperature of above 100C, e g~ from 150C to 180C~
In the third step of the process of this invention the blend whilst it is hot, i.e. at a temperature above the melting point of the ther plastic resin, is deformed. Deforming, i.e. changing of shape, can be carried out in various ways, e.g. stretching, thermoforming or cold forging~ Such deforming techniques are well-known and are described in more detail later in this specification when describing specific applications of the process of the lnvention.
In the last step the blend in the deformed state is cooled to a temperature below the melting po;nt of the thermoplastic resin. This in practice usually means cooling to a temperature below 50 C, e.g~ ambient temperature. The cooling should preferably be carried out as quickly as is practicable. After cooling the blend is usually released from external stresses and at temperatures below the melting point of the thermoplastic re.8in it is found that blend retains its new shape and dimensions.
Furthermore, the shaped blend exhibits "frozen" elastic memory, which means that if it is heated to a temperature above the melting point of the thermoelastic resin it reverts to its original cured shape, i.e. the shape it had before being deformed. This phenomenon is reversible and so the blend after reverting to its original shape could be reheated and deformed to a new ahape by carrying out steps (ii), (iii) and (iv) of the process of thi~
invention. --....
,: : .- , ~. :.
.
1C13~023 By the process of thls lnvention artlcles can be produced which are elastomeric and which have substantially higher physifal properties such as toughness and tensile strength than the cured blend before it is subjected to steps (ill) and (iv) of the process of this invention.
The process of this invent~on has many commercial applications and various examples of such uses are given below Solid industrial tyres can be slmply produced~ Thus, using for example an EPDM/polyethylene blend this may be cured in a mould having a diameter less than that of the hub. After removing the cured blend from the mould the hot tyre is placed in a simple stretcher, stretched to a diameter greater than that of the hub, and cooled to ambient temperature. The oversized tyre is easily mounted on a variety of hubs with diameters between that of the original mould and that of the stretched tyre. The tyre assembled on the hub is then heated in a hot air oven when the tyre reverts to its original diameter, thus forming a perfect shrink on the hub.
Similar techniques may be used for a variety of insert mouldings and for producing shrinkable O-rings.
There is a large and growing demand for industrial strapping, and the process of this invention enables one to make tough elastomeric strapping from cured elastomer/thermoplastic resin blends. These strappings have elasticity and flexibility together with optional heat shrinkability.
The blend may be compounded, extruded and continuously vulcanized in for example, LCM with immediate, in line, stretching and cooling. The strapping has elastic characteristics combined with very high tensile and heat shrink properties. The strapping may be used with or without resorting to its heat shrink properties.
One important application is the production of shrink tubing~ The tubing is initially produced with a diameter greater than the final diameter requlred by subjectlng the blend to curing, heating, deforming and cooling ln ~he deformed state~ The tubing is then shrunk to ~he required diameter by heatlng. The major uses of shrink tubing are:
(a) the insulation of eLectric connections by sleeves produced from shrink tubing ('D) the repair and reclamation of rubber hoses having a damaged and leaking portion (c) producing external protective lining of buried steel and iron pipelines, and td) producing external protective llning of cylindrical shapes.
Another lmportant application is thermoforming whereby a variety of intricate and large surface area elastomeric art;cles, which otherwise would require very expensive moulding tools and presses, can be economically and simply produced. The raw material for the thermoforming is an elastomerîc sheet (in th;s case EPDM/polyethylene) produced ~o the desired thickness by extrusion or calendering and subsequent vulcani~ation. The cured sheet is then preheated, e.g. to above 120 C, preferably above 160 C, and then placed in a thermoformer or vacuum former, the moulds in both cases being cold. Positive pressure or vacuum respectively, is applied and the article is formed ant cooled at the same time. The economic advantage of the process is due to the fact that practically no blanks are wastedO A moulding reject is easily re-used by reheating the ar~icle to above 160 C wher~ it returns to its origînal shape, i.eO that of the blank. This blank can then be used agalnO
Thermoforming can be used for producing a great variety of products, such as bellows, cups, covers, floor mats, etc.
The cured elastomeric composition prepared by the process of the invention can be used for cold forging. Thus, a fluxed and compounded blend of EPDM and thermoplastic resin wlth suitable curatives is shaped into desired blanks. The shaping may be done using an extruder or a Barwell (TM) preformer. The blanks are .,.::. . :: ; . ~ ~-cured and are fed dlrectly, whilst hot, from the curing stage into the forging press.
During forging the hot, cured blank is subjected to high pressure and takes the form o~
the cold mould. During the forging cycle it is sufficient to cool the outer surface of the article to a degree that will safeguard the dimensional stability whilst the article is removed from the mould. A~ with the thermoforming process there are substantially no moulding rejects. -~
Example Various blends (A, B, C, D and E) were prepared from commercially available EPDM (Vistalo~) and either low-density polyethylene (Idpe) or high-density polyethylene (hdpe). Aiso various other ingred;énts (e.g.
clay, whiting etc) were included. The various components were mixed in an internal mixer and curing agents added in a second pass.
Each of the blends A. B and C were extruded into a tube and a strip and steam cured for 20 minutes at 170 C. Blends D and E were press cured for 20 minutes at 170C.
The composition of the blend~ and their physical proper~ies are g;ven below:
A B C D E
VISTALON 3708 (EPDM) 70 VISTALON 5600.(EPDM~ 70 20 VISTALON 4608 (EPDM) 70 70 70 ldpe 30 30 30 hdpe 30 30 Calcined Clay 100 100 100 Whiting 50 50 100 APF (carbon black) 100 lOO
Paraffinic Process Oil 50 50 30 50 50 Stearic Acid 1~5 Zinc Oxide 4 4 MBTS (benzothiazyl disulphide) 106 30 VU1CAdOn~ 3$~ ~a curative~ 3~0 * Trade Mark - 8 -: - . .. ..
"'` ~ , ' . ':
.. . .
~Q39~?23 Sulphur 0.8 Perkadox 1440 (peroxide cross-linking agent) 6 6 6 6 Activator OC ) co-agents 1.5 1.5 ~ ) for Sartomex 206 ) Perkadox 1440 2 2 Shore Hardness 70 76 70 82 80 Tensile kg/cm 68 70 42 13~ 87 100% Modulus kg/cm 30 59 50 300% Modulus kg/cm2 38 51 33 124 Elongation % 990 720 610 360 220 The cured strips were heated in hot air to 160 C and stretched to 100-250% elongation and cooled in the stretched form by immersion in cold water. The physical properties of the stretched samples were as follows:
Sample A B C D E
20 minutes at 170 C cure steam steam steam Press Press % stretch 200 220 110100 ; 130 110 Shore hardness 63 81 82 77 Tensile kg/cm 160 150 96 270 296 236 100% Modulus 137 80 211 276 Elongation at break % 120 180 180200 120 90 Sim;larly the cured tubes were heated to over 160C and stretched on a mandrel to about tw;ce the original diameter and cooled to room temperature.
The extended forms exhibit dimensional stability at room temperatures and had a characteristic elastomeric behaviour with enhanced toughness and tensile strength. The oriented strip and the stretched tube shrank to their original cured dimensions and shape upon heating to over 100-120 C.
The press-cured pads were heated to 170C and whilst still hot, thermoformed on a simple, cold mould. The cold thermoformed shape retained its dimensions at room temperature and exhib;ted typical elastomer properties.
Upon heating to 130 C the thermoformed part returned completely to its original cured shape.
~7~ad~7Q~ ~ 9 ~
'~`: . : , ' ' i ' ' : . . . ` '~ . . .' " ~ . -
Claims (9)
- THE Embodiments OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
l. A process for the preparation of an elastomeric article in which a blend of an EPDM elastomer and a thermoplastic resin with an elastomer:resin weight ratio of between 90:10 and 50:50 is mixed and fluxed and compounded with a filler, a plasticizer and a curative, and the blend (i) is either shaped and cured simultaneously or shaped and subsequently cured, (ii) the cured blend is heated to a temperature above the melting point of the thermoplastic resin, (iii) the heated blend is deformed, and (iv) the blend in the deformed state is cooled to a temperature below the melting point of the thermoplastic resin. - 2. A process according to claim 1 wherein the EPDM has an ethylene content of at least 55 wt. %.
- 3. A process according to claim 1 wherein the thermoplastic resin is low density polyethylene or polypropylene or high density polyethylene or polypropylene.
- 4. A process according to any one of claims 1 to 3 wherein the amount of thermoplastic resin is 15 to 35 wt. % based on the total weight of elastomer and thermoplastic resin.
- 5. A process according to any one of claims 1 to 3 wherein the cured blend is heated to a temperature of 150°C to 180°C before being deformed.
- 6. A process according to any one of claims 1 to 3 wherein the blend in the deformed state is cooled to a temperature of below 50°C.
- 7. A process according to claim 1 wherein the article is an in-dustrial tyre, the resin is polyethylene, the blend is cured in a mould having a diameter less than that of the tyre hub, the heated tyre is de-formed by stretching it to a diameter greater than that of the tyre hub and the deformed tyre is cooled to ambient temperature.
- 8. A process according to claim 1 wherein an intricate and large surface area elastomeric article is made by thermoforming, the blend being an EPDM/polyethylene sheet, the cured sheet being heated to above 120°C, the heated sheet is placed in a thermoformer or vacuum former in which it is deformed and the deformed sheet is cooled to a temperature below the melting point of the thermoplastic resin.
- 9. A process according to claim 1 wherein the article is produced by cold forging, the blend of EPDM and resin is shaped into blanks in a mould by an extruder or a Barwell (TM) preformer and the blanks are cured and fed directly whilst at a temperature above the melting point of the resin to a forging press in which the cured blank is subjected to high pressure, taking the form of the cold mould and the moulded article is cooled to a temperature below the melting point of the thermoplastic resin.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB3461173A GB1455421A (en) | 1973-07-20 | 1973-07-20 | Elastomer articles |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1039023A true CA1039023A (en) | 1978-09-26 |
Family
ID=10367817
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA204,694A Expired CA1039023A (en) | 1973-07-20 | 1974-07-12 | Process of preparing shaped elastomeric articles |
Country Status (5)
| Country | Link |
|---|---|
| CA (1) | CA1039023A (en) |
| DE (1) | DE2433005A1 (en) |
| FR (1) | FR2237755B3 (en) |
| GB (1) | GB1455421A (en) |
| IT (1) | IT1017084B (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2007685B (en) * | 1977-10-11 | 1982-05-12 | Asahi Dow Ltd | Composition for drawn film cold drawn film made of said composition and process for manufacture of said film |
| US4264490A (en) * | 1979-05-11 | 1981-04-28 | Radiation Dynamics, Inc. | Composition of a polyethylene and isobutylene copolymer |
| US5034078A (en) * | 1985-05-08 | 1991-07-23 | Exxon Chemical Patents Inc. | Method of making an elastomeric film |
| US5043115A (en) * | 1988-03-10 | 1991-08-27 | Sumitomo Chemical Company, Limited | Heat-shrinkable, tubular foam |
| US5071886A (en) * | 1988-03-10 | 1991-12-10 | Sumitomo Chemical Company, Limited | Heat-shrinkable, tubular foam |
| JPH0681793B2 (en) * | 1988-03-10 | 1994-10-19 | 住友化学工業株式会社 | Heat-shrinkable foam tube and manufacturing method thereof |
-
1973
- 1973-07-20 GB GB3461173A patent/GB1455421A/en not_active Expired
-
1974
- 1974-07-09 DE DE19742433005 patent/DE2433005A1/en active Pending
- 1974-07-11 IT IT2506474A patent/IT1017084B/en active
- 1974-07-12 CA CA204,694A patent/CA1039023A/en not_active Expired
- 1974-07-19 FR FR7425245A patent/FR2237755B3/fr not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| GB1455421A (en) | 1976-11-10 |
| FR2237755B3 (en) | 1977-05-20 |
| DE2433005A1 (en) | 1975-02-06 |
| IT1017084B (en) | 1977-07-20 |
| FR2237755A1 (en) | 1975-02-14 |
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