CA1095213A - Stabilization of cross-linked polyolefins - Google Patents
Stabilization of cross-linked polyolefinsInfo
- Publication number
- CA1095213A CA1095213A CA277,272A CA277272A CA1095213A CA 1095213 A CA1095213 A CA 1095213A CA 277272 A CA277272 A CA 277272A CA 1095213 A CA1095213 A CA 1095213A
- Authority
- CA
- Canada
- Prior art keywords
- additive
- article
- sheet
- cross
- low friction
- 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
Links
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
- C08J7/00—Chemical treatment or coating of shaped articles made of macromolecular substances
- C08J7/04—Coating
- C08J7/046—Forming abrasion-resistant coatings; Forming surface-hardening coatings
-
- 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
- C08J7/00—Chemical treatment or coating of shaped articles made of macromolecular substances
- C08J7/04—Coating
- C08J7/06—Coating with compositions not containing macromolecular substances
- C08J7/065—Low-molecular-weight organic substances, e.g. absorption of additives in the surface of the article
-
- 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
- C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
- C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
Abstract
ABSTRACT OF THE DISCLOSURE
A method of incorporating additives into cross-linked poly-olefins is provided herein. A shaped article formed of the cross-linked polyolefins is heated to an elevated temperature above its crystalline melting point. That article at that elevated temperature is then con-tacted with the additive for a period sufficient to obtain the desired take up of additive per unit area of the surface contacted therewith.
The article is removed from contact with the additive while maintaining the article at the elevated temperature. Thereafter the article is cooled to below the crystalline melting point. The article so formed does not suffer the disadvantage of blister formation. Moreover, the additive can supply surface friction reducing properties to make the material suitable for uses as ski soles and boat hulls.
A method of incorporating additives into cross-linked poly-olefins is provided herein. A shaped article formed of the cross-linked polyolefins is heated to an elevated temperature above its crystalline melting point. That article at that elevated temperature is then con-tacted with the additive for a period sufficient to obtain the desired take up of additive per unit area of the surface contacted therewith.
The article is removed from contact with the additive while maintaining the article at the elevated temperature. Thereafter the article is cooled to below the crystalline melting point. The article so formed does not suffer the disadvantage of blister formation. Moreover, the additive can supply surface friction reducing properties to make the material suitable for uses as ski soles and boat hulls.
Description
~S2~
The present invention relates to the incorporatiGn of additives into cross-linked polyolefins and has particular re~erence to the ~ inclusion of stabilizers, surface fricti.on reductants and the like.Many dlfferent types of heat stabilizers and additives in general for polyolefinic materials, e.g., polyethylene, can be emp].oyedO
Some of these are employed to stabilize the material during processing while others are added to the polymer mostly to ensure long life of the finished products and also to enhance surEace and other properties of the materlal. Where manufactured cross-linked polyolefins, e.g. cross-linked polyethylene, are involved, the mixing of many additives with a cross-linking initiator or cross-linking agent, e.g. a peroxide cross-linking agent, has the effect of (a~ diminishing the effectiveness of the additive, and (b) makes it necessary to use more peroxide to obtain the same degree of cross-linking.
Furthermore, some reaction can occur between the pero~ide cross-linking agent and the additive which can, in extrem~ circumstances, cause the generation of gases during the cross-linking reaction thus resulting, during formation and during the cross-linking process, in the formation of small blisters in the final product.
In consequence, it has been necessary, hitherto, to use at the most 0.15% to 0.2% by weight of additive for inclusion in the cross-linkable material prior to the cross-linking and forming since amounts in excess of this are liable to result in one or more of the disadvan-tages referred to above.
Where the additive is a stabiliæer for imparting heat stability to the cross-linked material, it is necessary to include, in general, a greater proportion than 0.2% by weight oE stabilizer within the cross-linked material in order to impart satisfactory heat stabilization.
Furthermore, with the advent of polyethylene pipes as described ~ ~
in British Patent Specification No. 1,158,011 and the use of such pipes ~ .
for hot water systems and the like, the inclusion of a sufficient quan-tity of stabilizer for the solution of this particular problem of high S~ L3 temperature stability has become Inore urgent. ~hi:Le pipes of unstabilized cross-linked'polyethylene have extremely good properties, there is a certain limit above which it is necessary to stabilize the material of the pipe and this, to some extent, limits the use and areas of use of the material. It has been'found, however, that if adequate stabilizer can be introduced into the cross-linked material without other side effects, then it is possible to use cross-linked polyolefinic materials for fluid temperatures between the range 100C. to 120C.
Furthermore the ability to include in an article additives : 10 which reduce surface Eriction property thereof makes such material parti-cularly useful for such diverse uses as ski soles and'boat hulls.
According to an aspect of the present invention, therefore, a method is provided for incorporating additives into a cross-linked poly- ' olefinic material which method comprises heating a shaped article formed of cross linked polyolefinic material to an elevated temperature above its crystalline melting point, contacting the article at that elevated temperature with a bath of additive ~or a period sufficient to obtain the desired take-up of additive per'unit area of the article surface contacted therewith, removing the'article from contact with the additive, maintaining the article at the elevated temperature and thereafter cool ing the article to below the crystalline melting point to assit diffusion of the additive within the material of the article.
The additive may be selected from one or more of antioxidants, ageing agents, stabllizers and/or materials wh:Lch effect the surface properties such as, for example, low friction agents.
The cross-linked polyolefin may typically be polyethylene and the additive may be an ageing agent, an antioxidizing agent, stabilizer and/or a low friction agent for the cross-linkecl polyethylene.
It will be appreciated that since the additive is introduced into the material after forming has taken place the tendency for forma-tion of blisters and the like due to gasification is very much reduced or is substantially eliminated.
In one aspect of t~e invention, the article to be treated is a cross-linked pipe or tube formed of polyolefin, partlcularly polyethy-1 ene. The temperature of the polyolefin during contact with the additive should be above the crystalline melting temperature of the cross-linked polyolefin. The typical temperature range for polyolefin is 115C. to 180C., preferably 140C. to 160C. The article may be passed through a bath of molten agent and the contact period with the agent may depend on the wall thickness of the article. The fîrst stabilizing agent employed may be one or more of the anti-oxldant commercially available under the Trade Mark "Irganox" and the pick up of the agent is typically within the range of 0.2% to 0.8% by weight based on the weight of cross-linked polyole~in.
~y a variant of this aspect of the invention, the additive is k' t ~ crc~
a low friction add:itive selected from one or more ~i~E-crystalline waxes and clear petroleum waxes and the article is passed at elevated tempera-ture through a bath of these materîals.
As mentioned above, typical stabilizing agents are those commercially available under the Trade Mark "Irganox" supplied by CIBA- GEIGY
AG. One of the stabilizing agents preferred in the method of an aspect of the .
20 present invention is octadecyl 3-~3-S-ditertiary-butyl-4-hydroxyphenoI) proprionate which is commercially available under the Trade Mark "Irganox 1076". ~nother stabilizing agent which has been successfully used in the course of methocl o;E an aspect of the present invention is tetrakis tmeth-ylene 3-3,5 ditertiarybutyl-4-hydroxyphenyl proprionate~ methane. This is a very heavy molecule including four sterically hindered phenolic .,;.
hydroxyl groups which provide high antioxidant activity. The large molecular weight of the compound contributes to low volatility and high extraction resistance when compounded with polymers. The material is commercially available under the registered Trade ~lark "Irganox 1010".
In use, the oxidizing agent or mixture of oxidizing agents are simply melted and put into a bath at the temperature of treatment. The ~;
article is then immersed for a period determined by the average wall ~
,. . . . . .
- , ~ ,~ . .. . .
0~2~3 tilickness until the pick up of material ls greater than O.~ b~ weight based on the total weight'of the'polyolefin process. The'article is ~ then removed from the bath and is the~ maintained at the treatment temperature for a further period of time to assist in the diffusion of the stabili~ing agent through the'material of the article itself. For a cross-linked polyolefin, e.g. polyethylene, the crystalline melting point is of the order of 130C. Below 130C. the crystallites in the cross-linked material make the diffusion or migration process of the stabilizing agent very slow but above the crystalline melting point the diffusion is very much faster. By introducing to the exposed outer surface of the article a predetermined proportion of antioxldant or other stabilizing agent and thereafter maintaining the article for a short period of time at its contacting temperature, the material is maintained above the crystalline melting point and fiffusion proceeds fairly rapidly.
On cooling of the article, if cooling takes place from the contacting surface inwardly, then the distribution of the stabilizing agents through the wall of the article is assisted. The cooling article may be affected by rapid chilling of the external surface.
Thus, by an aspect of this invention, an article is provided comprising a sheet of cross~linked polyolefillic material having a low '~
friction surface obtained by contacting the surface with a low friction additive.
The invention in another aspect also includes the method of forming a sheet of low friction material which comprises forming a tube -~
of cross~linked polyolefin materia], slitting the tube to form a longitu-dinal sheet, passing the sheet through a bath of low friction additive while the sheet is maintained at an elevated temperature above its crystalline melting point, removing the sheet from the bath while main-taining the sheet at the elevated temperature and thereafter cooling to ' below the crystalline melting point to assist diffusion of the additive within the material of the'article.
By one variant, the additive is one or more of micro-crystalline .
' :
wax an~/or clear petroleum wax wlle~ein one surface on]y o~ the sheet is treated.
By another variant, the wax take up is 1.4% to 2.2% by weight.
The invention in yet'a further aspect includes a ki or a boat hull including a surface layer of low friction sheet or sheets in accor-~ance wiLh the method as described above.
Thus~ by one variant, the sole i5 bonded is the ski using an epoxy resin adhesive.
By another variant, the boat hull has a layer of polyolefinic : 10 material having a low friction surface, the hull layer being formed, at least below the water line, by one or more sheets having a low friction surface in accordance with the method as described above '~.
A modification of the'method of an aspect of the invention is effected by treating the tube first with the low friction additive together with any other additives that may be necessary or desirable and thereafter slitting the tube longitudinally to form the sheet and opening out the tube to form a sheet material.
bC, J, rn ~, ht In a typical em~o~i~m~t of the present invention, the tube of diameter such that the circumference is equivalent to the desired width ~;
of a ski sole :is extruded in the'usual way and the manner described i.n British Patent Specification No. 1,15~,011. AEter extrusion prior to completion of cross-linking t'he tube is slit immediately after the die.
Just before or immediately after the cross-linking of the material is completely, the hot material is passed through a bath of molten waxes constituting the low friction additive. The waxes are typically micro-crystalline waxes and clear petroleum ~axes commercially available under the Trade Mark "l~ER~". The sheet so formed is maintained in contact with the low friction additive until the desired ta~e up of 1.2% to 2.2%
by weight of wax material has been effected. Thereafter, the cross-linked pol~olefinic material is removed rom the contact ~ith the low friction additive and is passed through a die or calibration tool which ~ 52~.3 . ~
permanently flattens the material to render it suitable for application ~' to a ski sole. The materîal is then'cooled'faîrly rapidly by passage through a water bath thereby allowing the difEusion of the low friction additive to the material to proceed to completion.
The sheet thus formed is then attached to the sole of the ski concerned. 'rhe surface to be secured to the ski is first ground to increase the surface area and surface energy and is then flame treated to oxidize the polyolefinic layer using, for instance~ propyne which is sometimes known as "Mapgas". The'exposed layer is further treated with a corona discharge further to oxidize the layer and then the material, with the low friction outermost is then stuck to the ski using an epoxy adhesive such as that commercially available under the Trade Mark "Araldite" from Ciba-Geigy.
It has been found that skis so produced have much lower coefficient of friction and maintain a low efficient fric~ion more or less permanently and thus substantially avoid the need for continual waxing of the skis for optimum performance.
The additive should be soluble in the polyolefinic material in order to enable adequate and sufficien~ diffusion into the material ~
se to take place. - ' Following is a description by way of example on~y of methods of carrying aspects of the invention into eEfect.
A bath was made up of 7 parts of Irganox 1076 and 25 parts of ~' Irganox l010, the parts being by weight. A tube of 30 -mm outside diameter and wall thickness 2.5 mm was formed of cross~linked polyethylene and was fed direct from its extruder into a bath of material heated to 150C.
The tube was passed through the bath so as to maintain contact therewith for a period of the order of 6 scconds. At the end of this time, the ~ take up of antioxidants into the'cross-linked polyethylene is oE the order of 0.3% by weight based'on the weight of the polye~hylene. The tube is then removed from the bath and passed through a heating chamber whereby the temperature of the'tube is maintained'at or above the temperature of contact with the antioxidants for 15 seconds. Thereafter the tube is passed into a water bath to chill tlle tube and allow crystallization of the material to occur.
Samples of the tube so produced were heated in an oven to 150~C. together with samples of similar tubes containing stabilizers incorporated in the conventional manner, i~e. prior to cross-linking.
The tubes produced in accordance with the example described were with-drawn after six weeks and did not appear to have suffered any visible degradation. Untreated tubes lasted for one day. Tubes with conven tional stabilization lasted five days, and up to three weeks if the proportion of antioxidant was so high that blisters appeared in the material of the tube.
~0
The present invention relates to the incorporatiGn of additives into cross-linked polyolefins and has particular re~erence to the ~ inclusion of stabilizers, surface fricti.on reductants and the like.Many dlfferent types of heat stabilizers and additives in general for polyolefinic materials, e.g., polyethylene, can be emp].oyedO
Some of these are employed to stabilize the material during processing while others are added to the polymer mostly to ensure long life of the finished products and also to enhance surEace and other properties of the materlal. Where manufactured cross-linked polyolefins, e.g. cross-linked polyethylene, are involved, the mixing of many additives with a cross-linking initiator or cross-linking agent, e.g. a peroxide cross-linking agent, has the effect of (a~ diminishing the effectiveness of the additive, and (b) makes it necessary to use more peroxide to obtain the same degree of cross-linking.
Furthermore, some reaction can occur between the pero~ide cross-linking agent and the additive which can, in extrem~ circumstances, cause the generation of gases during the cross-linking reaction thus resulting, during formation and during the cross-linking process, in the formation of small blisters in the final product.
In consequence, it has been necessary, hitherto, to use at the most 0.15% to 0.2% by weight of additive for inclusion in the cross-linkable material prior to the cross-linking and forming since amounts in excess of this are liable to result in one or more of the disadvan-tages referred to above.
Where the additive is a stabiliæer for imparting heat stability to the cross-linked material, it is necessary to include, in general, a greater proportion than 0.2% by weight oE stabilizer within the cross-linked material in order to impart satisfactory heat stabilization.
Furthermore, with the advent of polyethylene pipes as described ~ ~
in British Patent Specification No. 1,158,011 and the use of such pipes ~ .
for hot water systems and the like, the inclusion of a sufficient quan-tity of stabilizer for the solution of this particular problem of high S~ L3 temperature stability has become Inore urgent. ~hi:Le pipes of unstabilized cross-linked'polyethylene have extremely good properties, there is a certain limit above which it is necessary to stabilize the material of the pipe and this, to some extent, limits the use and areas of use of the material. It has been'found, however, that if adequate stabilizer can be introduced into the cross-linked material without other side effects, then it is possible to use cross-linked polyolefinic materials for fluid temperatures between the range 100C. to 120C.
Furthermore the ability to include in an article additives : 10 which reduce surface Eriction property thereof makes such material parti-cularly useful for such diverse uses as ski soles and'boat hulls.
According to an aspect of the present invention, therefore, a method is provided for incorporating additives into a cross-linked poly- ' olefinic material which method comprises heating a shaped article formed of cross linked polyolefinic material to an elevated temperature above its crystalline melting point, contacting the article at that elevated temperature with a bath of additive ~or a period sufficient to obtain the desired take-up of additive per'unit area of the article surface contacted therewith, removing the'article from contact with the additive, maintaining the article at the elevated temperature and thereafter cool ing the article to below the crystalline melting point to assit diffusion of the additive within the material of the article.
The additive may be selected from one or more of antioxidants, ageing agents, stabllizers and/or materials wh:Lch effect the surface properties such as, for example, low friction agents.
The cross-linked polyolefin may typically be polyethylene and the additive may be an ageing agent, an antioxidizing agent, stabilizer and/or a low friction agent for the cross-linkecl polyethylene.
It will be appreciated that since the additive is introduced into the material after forming has taken place the tendency for forma-tion of blisters and the like due to gasification is very much reduced or is substantially eliminated.
In one aspect of t~e invention, the article to be treated is a cross-linked pipe or tube formed of polyolefin, partlcularly polyethy-1 ene. The temperature of the polyolefin during contact with the additive should be above the crystalline melting temperature of the cross-linked polyolefin. The typical temperature range for polyolefin is 115C. to 180C., preferably 140C. to 160C. The article may be passed through a bath of molten agent and the contact period with the agent may depend on the wall thickness of the article. The fîrst stabilizing agent employed may be one or more of the anti-oxldant commercially available under the Trade Mark "Irganox" and the pick up of the agent is typically within the range of 0.2% to 0.8% by weight based on the weight of cross-linked polyole~in.
~y a variant of this aspect of the invention, the additive is k' t ~ crc~
a low friction add:itive selected from one or more ~i~E-crystalline waxes and clear petroleum waxes and the article is passed at elevated tempera-ture through a bath of these materîals.
As mentioned above, typical stabilizing agents are those commercially available under the Trade Mark "Irganox" supplied by CIBA- GEIGY
AG. One of the stabilizing agents preferred in the method of an aspect of the .
20 present invention is octadecyl 3-~3-S-ditertiary-butyl-4-hydroxyphenoI) proprionate which is commercially available under the Trade Mark "Irganox 1076". ~nother stabilizing agent which has been successfully used in the course of methocl o;E an aspect of the present invention is tetrakis tmeth-ylene 3-3,5 ditertiarybutyl-4-hydroxyphenyl proprionate~ methane. This is a very heavy molecule including four sterically hindered phenolic .,;.
hydroxyl groups which provide high antioxidant activity. The large molecular weight of the compound contributes to low volatility and high extraction resistance when compounded with polymers. The material is commercially available under the registered Trade ~lark "Irganox 1010".
In use, the oxidizing agent or mixture of oxidizing agents are simply melted and put into a bath at the temperature of treatment. The ~;
article is then immersed for a period determined by the average wall ~
,. . . . . .
- , ~ ,~ . .. . .
0~2~3 tilickness until the pick up of material ls greater than O.~ b~ weight based on the total weight'of the'polyolefin process. The'article is ~ then removed from the bath and is the~ maintained at the treatment temperature for a further period of time to assist in the diffusion of the stabili~ing agent through the'material of the article itself. For a cross-linked polyolefin, e.g. polyethylene, the crystalline melting point is of the order of 130C. Below 130C. the crystallites in the cross-linked material make the diffusion or migration process of the stabilizing agent very slow but above the crystalline melting point the diffusion is very much faster. By introducing to the exposed outer surface of the article a predetermined proportion of antioxldant or other stabilizing agent and thereafter maintaining the article for a short period of time at its contacting temperature, the material is maintained above the crystalline melting point and fiffusion proceeds fairly rapidly.
On cooling of the article, if cooling takes place from the contacting surface inwardly, then the distribution of the stabilizing agents through the wall of the article is assisted. The cooling article may be affected by rapid chilling of the external surface.
Thus, by an aspect of this invention, an article is provided comprising a sheet of cross~linked polyolefillic material having a low '~
friction surface obtained by contacting the surface with a low friction additive.
The invention in another aspect also includes the method of forming a sheet of low friction material which comprises forming a tube -~
of cross~linked polyolefin materia], slitting the tube to form a longitu-dinal sheet, passing the sheet through a bath of low friction additive while the sheet is maintained at an elevated temperature above its crystalline melting point, removing the sheet from the bath while main-taining the sheet at the elevated temperature and thereafter cooling to ' below the crystalline melting point to assist diffusion of the additive within the material of the'article.
By one variant, the additive is one or more of micro-crystalline .
' :
wax an~/or clear petroleum wax wlle~ein one surface on]y o~ the sheet is treated.
By another variant, the wax take up is 1.4% to 2.2% by weight.
The invention in yet'a further aspect includes a ki or a boat hull including a surface layer of low friction sheet or sheets in accor-~ance wiLh the method as described above.
Thus~ by one variant, the sole i5 bonded is the ski using an epoxy resin adhesive.
By another variant, the boat hull has a layer of polyolefinic : 10 material having a low friction surface, the hull layer being formed, at least below the water line, by one or more sheets having a low friction surface in accordance with the method as described above '~.
A modification of the'method of an aspect of the invention is effected by treating the tube first with the low friction additive together with any other additives that may be necessary or desirable and thereafter slitting the tube longitudinally to form the sheet and opening out the tube to form a sheet material.
bC, J, rn ~, ht In a typical em~o~i~m~t of the present invention, the tube of diameter such that the circumference is equivalent to the desired width ~;
of a ski sole :is extruded in the'usual way and the manner described i.n British Patent Specification No. 1,15~,011. AEter extrusion prior to completion of cross-linking t'he tube is slit immediately after the die.
Just before or immediately after the cross-linking of the material is completely, the hot material is passed through a bath of molten waxes constituting the low friction additive. The waxes are typically micro-crystalline waxes and clear petroleum ~axes commercially available under the Trade Mark "l~ER~". The sheet so formed is maintained in contact with the low friction additive until the desired ta~e up of 1.2% to 2.2%
by weight of wax material has been effected. Thereafter, the cross-linked pol~olefinic material is removed rom the contact ~ith the low friction additive and is passed through a die or calibration tool which ~ 52~.3 . ~
permanently flattens the material to render it suitable for application ~' to a ski sole. The materîal is then'cooled'faîrly rapidly by passage through a water bath thereby allowing the difEusion of the low friction additive to the material to proceed to completion.
The sheet thus formed is then attached to the sole of the ski concerned. 'rhe surface to be secured to the ski is first ground to increase the surface area and surface energy and is then flame treated to oxidize the polyolefinic layer using, for instance~ propyne which is sometimes known as "Mapgas". The'exposed layer is further treated with a corona discharge further to oxidize the layer and then the material, with the low friction outermost is then stuck to the ski using an epoxy adhesive such as that commercially available under the Trade Mark "Araldite" from Ciba-Geigy.
It has been found that skis so produced have much lower coefficient of friction and maintain a low efficient fric~ion more or less permanently and thus substantially avoid the need for continual waxing of the skis for optimum performance.
The additive should be soluble in the polyolefinic material in order to enable adequate and sufficien~ diffusion into the material ~
se to take place. - ' Following is a description by way of example on~y of methods of carrying aspects of the invention into eEfect.
A bath was made up of 7 parts of Irganox 1076 and 25 parts of ~' Irganox l010, the parts being by weight. A tube of 30 -mm outside diameter and wall thickness 2.5 mm was formed of cross~linked polyethylene and was fed direct from its extruder into a bath of material heated to 150C.
The tube was passed through the bath so as to maintain contact therewith for a period of the order of 6 scconds. At the end of this time, the ~ take up of antioxidants into the'cross-linked polyethylene is oE the order of 0.3% by weight based'on the weight of the polye~hylene. The tube is then removed from the bath and passed through a heating chamber whereby the temperature of the'tube is maintained'at or above the temperature of contact with the antioxidants for 15 seconds. Thereafter the tube is passed into a water bath to chill tlle tube and allow crystallization of the material to occur.
Samples of the tube so produced were heated in an oven to 150~C. together with samples of similar tubes containing stabilizers incorporated in the conventional manner, i~e. prior to cross-linking.
The tubes produced in accordance with the example described were with-drawn after six weeks and did not appear to have suffered any visible degradation. Untreated tubes lasted for one day. Tubes with conven tional stabilization lasted five days, and up to three weeks if the proportion of antioxidant was so high that blisters appeared in the material of the tube.
~0
Claims (15)
1. A method of incorporating additives into crosslinked polyolefins which method comprises: heating an article formed of said crosslinked polyolefins to an elevated temperature above its crystalline melting point; contacting said article at said elevated temperature with said additive for a period of time sufficient to obtain the desired take up of additive per unit area of the surface contacted therewith; removing the article from contact with said additive while maintaining the article at said elevated temperature; and thereafter cooling the article to below the crystalline melting temperature.
2. A method as claimed in claim 1, wherein the cross-linked polyolefin is polyethylene.
3. A method as claimed in claim 1, wherein the additive is selected from stabilizing agents, antioxidizing agents and a low friction additive.
4. A method as claimed in claims 1, 2 or 3, wherein the article is a tube of crosslinked material.
5. A method as claimed in claims 1, 2 or 3, wherein the polyolefin is polyethylene and the temperature of contact with the additive is within the range of 115°C to 180 C.
6. A method as claimed in claims 1, 2 or 3, wherein the additive is in the form of a bath and the period of contact is dependent on the desired take up of additive into the polyolefinic material of the article.
7. A method as claimed in claims 1, 2 or 3, wherein the take up of additive by the article is within the range of 0.2% to 2.5% by weight based on the weight of the crosslinked polyolefin.
8. A method as claimed in claim 1, wherein the additive is a low friction additive selected from one or more micro-crystal-line waxes and clear petroleum waxes and wherein the article is passed at elevated temperature through a bath of these materials.
9. A method as claimed in claims 1, 2 or 3, wherein the additive is a low friction additive selected from one or more micro-crystalline waxes and clear petroleum waxes and wherein the article is in the form of a sheet obtained by slitting a tube longitudinally.
10. An article of manufacture having a low friction surface comprising an article of cross-linked polyolefinic material having a low friction surface obtained by contacting said surface with a low friction additive as claimed in claim 8.
11. A method of forming a sheet with a low friction which method comprises: forming a tube of crosslinked polyole-finic material; slitting the tube longitudinally to form a longitudinal sheet; heating said sheet to a temperature above the crystalline melting temperature of the polyolefinic material;
passing said sheet through a bath of low friction additive while the sheet is maintained at said elevated temperature; removing the sheet from said bath while maintaining said sheet at said elevated temperature; and thereafter cooling the sheet to below the crystalline melting point.
passing said sheet through a bath of low friction additive while the sheet is maintained at said elevated temperature; removing the sheet from said bath while maintaining said sheet at said elevated temperature; and thereafter cooling the sheet to below the crystalline melting point.
12. A method as claimed in claim 11, wherein the additive is at least one of micro-crystalline wax and clear petroleum wax, and one surface only of the sheet is treated.
13. A method as claimed in claim 12 or 13, wherein the tube of crosslinked polyolefinic material is first contacted with the additive and thereafter slit longitudinally to form the sheet.
14. An article of manufacture comprising an article formed of cross-linked polyolefins with an additive incorporated therein when prepared by the method of claim 1, 2 or 3.
15. An article of manufacture comprising a sheet of cross-linked polyolefinic material with an additive incorporated therein when prepared by the method of claim 11, 12 or 14.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB11874/76 | 1976-04-29 | ||
| GB11874/76A GB1532857A (en) | 1976-04-29 | 1976-04-29 | Incorporating additives into cross-linked polyolefin articles |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1095213A true CA1095213A (en) | 1981-02-10 |
Family
ID=9994264
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA277,272A Expired CA1095213A (en) | 1976-04-29 | 1977-04-28 | Stabilization of cross-linked polyolefins |
Country Status (14)
| Country | Link |
|---|---|
| AT (1) | AT350799B (en) |
| BE (1) | BE854146A (en) |
| CA (1) | CA1095213A (en) |
| DD (1) | DD129796A5 (en) |
| DE (1) | DE2718695A1 (en) |
| DK (1) | DK185877A (en) |
| FI (1) | FI771363A (en) |
| FR (1) | FR2349614A1 (en) |
| GB (1) | GB1532857A (en) |
| IT (1) | IT1116298B (en) |
| NL (1) | NL7704752A (en) |
| NO (1) | NO771462L (en) |
| PL (1) | PL108675B1 (en) |
| SE (1) | SE424643B (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2650765B1 (en) * | 1989-08-11 | 1993-07-30 | Henkel France | PROCESS FOR THE CONTINUOUS NON-ADHERENT TREATMENT OF A CORD OF PERMANENT ADHESIVE MATERIAL, IN PARTICULAR OF A THERMO FUSABLE ADHESIVE AT THE EXIT OF AN EXTRUDER MIXER AND DEVICE FOR CARRYING OUT THIS PROCESS AND PRODUCT THUS OBTAINED |
| US5238635A (en) * | 1992-04-16 | 1993-08-24 | Himont Incorporated | Process for treatment of particulate olefin polymer, resulting treated particles and method for using treating particles |
| EP1739119A1 (en) * | 2005-06-29 | 2007-01-03 | Bayer MaterialScience AG | Process for the treatment of plastic profiles |
-
1976
- 1976-04-29 GB GB11874/76A patent/GB1532857A/en not_active Expired
-
1977
- 1977-04-27 DE DE19772718695 patent/DE2718695A1/en not_active Withdrawn
- 1977-04-27 AT AT293277A patent/AT350799B/en not_active IP Right Cessation
- 1977-04-27 NO NO771462A patent/NO771462L/en unknown
- 1977-04-28 CA CA277,272A patent/CA1095213A/en not_active Expired
- 1977-04-28 SE SE7704896A patent/SE424643B/en not_active IP Right Cessation
- 1977-04-28 DK DK185877A patent/DK185877A/en not_active Application Discontinuation
- 1977-04-28 FI FI771363A patent/FI771363A/fi not_active Application Discontinuation
- 1977-04-29 PL PL1977197747A patent/PL108675B1/en unknown
- 1977-04-29 IT IT67963/77A patent/IT1116298B/en active
- 1977-04-29 DD DD7700198678A patent/DD129796A5/en unknown
- 1977-04-29 BE BE177171A patent/BE854146A/en unknown
- 1977-04-29 FR FR7712988A patent/FR2349614A1/en active Pending
- 1977-04-29 NL NL7704752A patent/NL7704752A/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| NO771462L (en) | 1977-11-01 |
| SE424643B (en) | 1982-08-02 |
| GB1532857A (en) | 1978-11-22 |
| DD129796A5 (en) | 1978-02-08 |
| NL7704752A (en) | 1977-11-01 |
| BE854146A (en) | 1977-08-16 |
| FI771363A (en) | 1977-10-30 |
| DE2718695A1 (en) | 1977-11-10 |
| DK185877A (en) | 1977-10-30 |
| IT1116298B (en) | 1986-02-10 |
| AT350799B (en) | 1979-06-25 |
| PL108675B1 (en) | 1980-04-30 |
| FR2349614A1 (en) | 1977-11-25 |
| ATA293277A (en) | 1978-11-15 |
| SE7704896L (en) | 1977-10-30 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |