CA1277798C - Process of crosslinking silicone rubber - Google Patents
Process of crosslinking silicone rubberInfo
- Publication number
- CA1277798C CA1277798C CA000526629A CA526629A CA1277798C CA 1277798 C CA1277798 C CA 1277798C CA 000526629 A CA000526629 A CA 000526629A CA 526629 A CA526629 A CA 526629A CA 1277798 C CA1277798 C CA 1277798C
- Authority
- CA
- Canada
- Prior art keywords
- peroxide
- silicone rubber
- peroxydicarbonate
- crosslinking
- aroyl
- 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
Landscapes
- Compositions Of Macromolecular Compounds (AREA)
Abstract
ABSTRACT
A process of crosslinking a silicone rubber using a combination of an aroyl peroxide and a solid peroxydicarbonate as crosslinking agent. The present process is attended with rapid crosslinking and results in products having favourable end properties, especially with regard to the absence of blooming.
A process of crosslinking a silicone rubber using a combination of an aroyl peroxide and a solid peroxydicarbonate as crosslinking agent. The present process is attended with rapid crosslinking and results in products having favourable end properties, especially with regard to the absence of blooming.
Description
~ ~777~
rhis invention relates to a process of crosslinking a silicone rubber com-pri~ing heating the rubbe~ in the presence of an aroyl peroxide.
Such a process is known from U~tedSt~Es ~fnt ~ifLr~icn No. 4,145,505, which describes the use of bis(o-chlorobenzoyl)peroxide as the crosslinking agent.
As i9 generally known, a process of this type involves compounding the rubber with the desired additives and heating the resulting compound.
Heating may be done in one of various ways, for example using heated moulds or using hot air vulcanization, the latter lnvolving passing an extruded compound through a hot air furnace.
The use of aroyl peroxides has, up to the present tlme, not been fully ~atisfactory, especlally with regard to hot air vulcanization. The main dis-advantage resides in that the cro~slinked products obtained display the ~o-called bloomlng effect, neces01tatlng a po~t-cure treatment. Another disad-vantage i8 found ln the relatively long times required to attain the desired degreeP of crosslinking. Both aspects render the prior art processes econo-mically unattractive.
The present invention has for its object to meet these drawbacks. According-ly, the process to which the invention relates is characterized in that in said rubber there i8 also present a peroxydicarbonate which is a solid at room temperature.
It should be noted that United States Patent Specification No. 4 ~60 536 discloses the use of a combination of peroxides in the hot air vulcanization of extruded sil~cone rubber compo~ltions. The peroxide~ involved are aromatic acylorganic peroxides, such as di(2,4-dichlorobenzoyl)peroxide, and alkylorganic peroxides, such as di-tert.butyl peroxide. The latter group of peroxides i5, of course, totally different from the peroxydicarbonates u~ed in the present invention. Moreover, the rubber composltion~ descrlbed in this rsference mu~t meet specific other requlrements, such as the pre~ence of an organohydrogenpolysiloxane, and, as iB apparent from the di~closure, ln most cases there is need for a po~t-vulcanization treatment. This reference, therefore, neither discloses the present invention nor renders it obvious.
'~7773~
Silicone rubbers useful in the process of the present in~ention are those generally known in the art. Examples thereof are dimethyl silicone rubber, methyl vinyl silicone rubber, methyl phenyl silicone rubber, chloro silicone rubber and fluoro silicone rubber.
Aroyl peroxides and peroxydicarbonates useful in the present process are also generally known in the art. Preferred aroyl pero.Yides are those satis-fying the general formula O O
<~C-O-O-C-~
Rn Rn wherein n = O, 1, 2 or 3 and R = CH3 or Cl.
Typical aroyl peroxides and peroxydicarbonates to be used are mentioned in the Example below.
The pçroxides may be incorporated into thQ rubb~r in accordance with known procedures. To this end the peroxites may be used separately or in premixed form. In a preferred embodiment the peroxides, prior to addition to the rubber, are formulated as pa~tes by employing silicone oil or phthalic esters, although use of the peroxides in their technically pure state is also feasible.
The amounts of the peroxides to be added preferably range from about 1 to about 10 mmoles of the aroyl peroxide and from about 0,5 to about ~ rnmoles of the peroxydicarbonate per 100 grams of silicone rubber.
Of course, also other constituents, such as fillers (for e~ample sili~a), plastici~ers (for example silicone oil) and antidegradants, may be included in the rubber prior to the crosslinking reaction.
The temperature of the rubber during crosslinking i5 generally in the ran8e of from about 90C to about 200C.
The present invention is further de~cribed in the following Example, inwhich the following abbreviations are used.
OMBPO - di(o-methylbenzoyl)peroxide BPO - dibenzoyl peroxide ~77 7~3~3 ACD ~021 MMBPO = di(m-methylbenzoyl)pero~ide 23DMBPo - di(2,3-dimethylbenzoyl)peroxide 24DMBPo = di(2,4-dimethylbenzoyl)peroxide 25D2~0 ~ di(2,5-dimethylbenzoyl)peroxide 26DMBPO ~ dl(2,6-dimethylbenzoyl)peroxide 234TMBPo - di(2,3,4-trimethylbenzoyl)peroxide 245TMBPo = di(2,4,5-trimethylbenzoyl)peroxide 235TMBPO ~ di(2,3,5-trimethylbenzoyl)peroxide OCBPO = di(o-chlorobenzoyl)peroxide PCBPO = di(p-chlorobenzoyl)peroxide 24DCBPO - di(2,4-dichlorobenzoyl)peroxide TCPD = di(4-tert.butylcyclohexyl)peroxydicarbonate PEPD = di(2-phenoxyethyl)peroxydicarbonate DCPD ~ dicetyl peroxydicarbonate DMPD - dimyristyl peroxydicarbonate DBPD ~ dibenzyl peroxyticarbonate ,, The Example describes the crosslinking of methyl vinyl silicone rubber using various combinations of an aroyl peroxide and a peroxydicarbonate. The combinations used are given in the Table below. All the tests were carried out as follows.
Two pastes, one consisting of 50 wt.% of an aroyl peroxide and 50 ut.% of a dimethyl silicone oil, the other consisting of 50 wt.% of a pero~ydicarbo-nate and 50 wt.% of a dimethyl silicone oil, were each prepared by milling the components in the appropriate amounts on a three-roll mill. Subsequent-ly, 1 part by weight of the paste containing the aroyl peroxide and 0,5 parts by weight of the paste containing the peroxydicarbonate were mixed with 100 parts by weight of methyl vinyl silicone rubber on a two-roll mill.
The ~esulting compound was used for carrying out three types of cro~slinklng experiments A, B and C (see below).
Comparative e~periments were performed in which a$ crosslinking agent there were used 1,5 parts by weight of pastes consisting of 50 wt.~/o of an aroyl peroxide (OCBPO, 234TMBPo or 245TMBPo) and 50 wt.% of a dlmethyl silicone oil.
A) Part of the compound wa~ rolled into a sheet having a thickness of 2 mm.
A sample of this sheet was placed ln a heated mould and crosslinked for 10 min. at 120C. Of the crosslinked sheet the tensile strength and the $~777~a~
~CD 2021 elongation were measured in accordance with JIS-~-63Q1. Blooming was judged by visual inspection of the surfaces one day and seven days after crosslinking, respectively.
The results are summarized in the Table, wherein "-" means no blooming and "+" means that some blooming was observed.
B) Another part of the compound was also rolled into a sheet 2 mm thick. The sheet was subsequently hot-air vulcanized in a Geer-oven for 30 min. at 180C (air temperature 300-400C). Blooming of the crosslinked sheet was assessed by visual inspection.
The resul~s are summarized in the Table.
The sheets were also assessed for their hardness by means of a Type A
Hardness ~eter in accordance with JIS-R-6301 and their surface tackiness.
In addition, cross sections of the sheets were analyzed for foaming during the vulcanization. No significant differences were found between the products obtained using the process of the invention and those ob-tained in accordance with the prior art teachings, viz. all the products had about the same hardness, none of the products was tacky and there had been no foaming in any of the vulcanizations.
C~ Still another part of the compound was analyzed for its crosslinking behaviour in term5 of t1o (induction period), tgo (period to reach optimum crosslinking) and ~torque by means of a JSR Curelastometer Model II at 120C.
The results are given in the Table.
From the data in the Table it is readily apparent that 1) the crosslinking reactions according to the invention are faster than those according to prior teachings, 2) the products obtained according to the invention process show favourable end properties as compared with the products obtained employing prior art crosslinking agents, especially in that blooming is virtually absent.
~777~
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rhis invention relates to a process of crosslinking a silicone rubber com-pri~ing heating the rubbe~ in the presence of an aroyl peroxide.
Such a process is known from U~tedSt~Es ~fnt ~ifLr~icn No. 4,145,505, which describes the use of bis(o-chlorobenzoyl)peroxide as the crosslinking agent.
As i9 generally known, a process of this type involves compounding the rubber with the desired additives and heating the resulting compound.
Heating may be done in one of various ways, for example using heated moulds or using hot air vulcanization, the latter lnvolving passing an extruded compound through a hot air furnace.
The use of aroyl peroxides has, up to the present tlme, not been fully ~atisfactory, especlally with regard to hot air vulcanization. The main dis-advantage resides in that the cro~slinked products obtained display the ~o-called bloomlng effect, neces01tatlng a po~t-cure treatment. Another disad-vantage i8 found ln the relatively long times required to attain the desired degreeP of crosslinking. Both aspects render the prior art processes econo-mically unattractive.
The present invention has for its object to meet these drawbacks. According-ly, the process to which the invention relates is characterized in that in said rubber there i8 also present a peroxydicarbonate which is a solid at room temperature.
It should be noted that United States Patent Specification No. 4 ~60 536 discloses the use of a combination of peroxides in the hot air vulcanization of extruded sil~cone rubber compo~ltions. The peroxide~ involved are aromatic acylorganic peroxides, such as di(2,4-dichlorobenzoyl)peroxide, and alkylorganic peroxides, such as di-tert.butyl peroxide. The latter group of peroxides i5, of course, totally different from the peroxydicarbonates u~ed in the present invention. Moreover, the rubber composltion~ descrlbed in this rsference mu~t meet specific other requlrements, such as the pre~ence of an organohydrogenpolysiloxane, and, as iB apparent from the di~closure, ln most cases there is need for a po~t-vulcanization treatment. This reference, therefore, neither discloses the present invention nor renders it obvious.
'~7773~
Silicone rubbers useful in the process of the present in~ention are those generally known in the art. Examples thereof are dimethyl silicone rubber, methyl vinyl silicone rubber, methyl phenyl silicone rubber, chloro silicone rubber and fluoro silicone rubber.
Aroyl peroxides and peroxydicarbonates useful in the present process are also generally known in the art. Preferred aroyl pero.Yides are those satis-fying the general formula O O
<~C-O-O-C-~
Rn Rn wherein n = O, 1, 2 or 3 and R = CH3 or Cl.
Typical aroyl peroxides and peroxydicarbonates to be used are mentioned in the Example below.
The pçroxides may be incorporated into thQ rubb~r in accordance with known procedures. To this end the peroxites may be used separately or in premixed form. In a preferred embodiment the peroxides, prior to addition to the rubber, are formulated as pa~tes by employing silicone oil or phthalic esters, although use of the peroxides in their technically pure state is also feasible.
The amounts of the peroxides to be added preferably range from about 1 to about 10 mmoles of the aroyl peroxide and from about 0,5 to about ~ rnmoles of the peroxydicarbonate per 100 grams of silicone rubber.
Of course, also other constituents, such as fillers (for e~ample sili~a), plastici~ers (for example silicone oil) and antidegradants, may be included in the rubber prior to the crosslinking reaction.
The temperature of the rubber during crosslinking i5 generally in the ran8e of from about 90C to about 200C.
The present invention is further de~cribed in the following Example, inwhich the following abbreviations are used.
OMBPO - di(o-methylbenzoyl)peroxide BPO - dibenzoyl peroxide ~77 7~3~3 ACD ~021 MMBPO = di(m-methylbenzoyl)pero~ide 23DMBPo - di(2,3-dimethylbenzoyl)peroxide 24DMBPo = di(2,4-dimethylbenzoyl)peroxide 25D2~0 ~ di(2,5-dimethylbenzoyl)peroxide 26DMBPO ~ dl(2,6-dimethylbenzoyl)peroxide 234TMBPo - di(2,3,4-trimethylbenzoyl)peroxide 245TMBPo = di(2,4,5-trimethylbenzoyl)peroxide 235TMBPO ~ di(2,3,5-trimethylbenzoyl)peroxide OCBPO = di(o-chlorobenzoyl)peroxide PCBPO = di(p-chlorobenzoyl)peroxide 24DCBPO - di(2,4-dichlorobenzoyl)peroxide TCPD = di(4-tert.butylcyclohexyl)peroxydicarbonate PEPD = di(2-phenoxyethyl)peroxydicarbonate DCPD ~ dicetyl peroxydicarbonate DMPD - dimyristyl peroxydicarbonate DBPD ~ dibenzyl peroxyticarbonate ,, The Example describes the crosslinking of methyl vinyl silicone rubber using various combinations of an aroyl peroxide and a peroxydicarbonate. The combinations used are given in the Table below. All the tests were carried out as follows.
Two pastes, one consisting of 50 wt.% of an aroyl peroxide and 50 ut.% of a dimethyl silicone oil, the other consisting of 50 wt.% of a pero~ydicarbo-nate and 50 wt.% of a dimethyl silicone oil, were each prepared by milling the components in the appropriate amounts on a three-roll mill. Subsequent-ly, 1 part by weight of the paste containing the aroyl peroxide and 0,5 parts by weight of the paste containing the peroxydicarbonate were mixed with 100 parts by weight of methyl vinyl silicone rubber on a two-roll mill.
The ~esulting compound was used for carrying out three types of cro~slinklng experiments A, B and C (see below).
Comparative e~periments were performed in which a$ crosslinking agent there were used 1,5 parts by weight of pastes consisting of 50 wt.~/o of an aroyl peroxide (OCBPO, 234TMBPo or 245TMBPo) and 50 wt.% of a dlmethyl silicone oil.
A) Part of the compound wa~ rolled into a sheet having a thickness of 2 mm.
A sample of this sheet was placed ln a heated mould and crosslinked for 10 min. at 120C. Of the crosslinked sheet the tensile strength and the $~777~a~
~CD 2021 elongation were measured in accordance with JIS-~-63Q1. Blooming was judged by visual inspection of the surfaces one day and seven days after crosslinking, respectively.
The results are summarized in the Table, wherein "-" means no blooming and "+" means that some blooming was observed.
B) Another part of the compound was also rolled into a sheet 2 mm thick. The sheet was subsequently hot-air vulcanized in a Geer-oven for 30 min. at 180C (air temperature 300-400C). Blooming of the crosslinked sheet was assessed by visual inspection.
The resul~s are summarized in the Table.
The sheets were also assessed for their hardness by means of a Type A
Hardness ~eter in accordance with JIS-R-6301 and their surface tackiness.
In addition, cross sections of the sheets were analyzed for foaming during the vulcanization. No significant differences were found between the products obtained using the process of the invention and those ob-tained in accordance with the prior art teachings, viz. all the products had about the same hardness, none of the products was tacky and there had been no foaming in any of the vulcanizations.
C~ Still another part of the compound was analyzed for its crosslinking behaviour in term5 of t1o (induction period), tgo (period to reach optimum crosslinking) and ~torque by means of a JSR Curelastometer Model II at 120C.
The results are given in the Table.
From the data in the Table it is readily apparent that 1) the crosslinking reactions according to the invention are faster than those according to prior teachings, 2) the products obtained according to the invention process show favourable end properties as compared with the products obtained employing prior art crosslinking agents, especially in that blooming is virtually absent.
~777~
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:~ e t ~ ~ ~ ~ ~O ~t 1-1 ~ ~t ~ ~t t t t ~t ~ ~ ~ ~t ~ t t t t t I ~ t ~t ..
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1::1 ~ 11111111111111111~+11 ~1 _~
,a ~ II~III~IIIIIIII~II~
,~ ~
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Claims (5)
1. A process of crosslinking a silicone rubber comprising heating the rubber in the concurrent presence of both a crosslinking agent effective amount of an aroyl peroxide and a crosslinking agent effective amount of a peroxydicarbonate which is a solid at room temperature.
2. A process according to claim 1, wherein said aroyl peroxide is present in an amount of from about 1 to about 10 mmoles, and said peroxydicarbonate is present in an amount of from about 0.5 to about 5 mmoles, per 100 grams of the silicone rubber.
3. A process according to claim 1, wherein said silicone rubber is selected from the group consisting of dimethyl silicone rubber, methyl vinyl silicone rubber, methyl phenyl silicone rubber, chloro silicone rubber and fluoro silicone rubber.
4. A process according to claim 1, wherein said aroyl peroxide is selected from the group consisting of di(o-methylbenzoyl)peroxide, dibenzoyl peroxide, di(m-methylbenzoyl)peroxide, di(2,3-dimethylbenzoyl)-peroxide, di(2,4-dimethylbenzoyl)peroxide, di(2,5-dimethylbenzoyl)peroxide, di(2,6-dimethylbenzoyl)-peroxide, di(2,3,4-trimethylbenzoyl)peroxide, di(2,4,5-trimethylbenzoyl)peroxide, di(2,3,5-trimethylbenzoyl)-peroxide, di(o-chlorobenzoyl)peroxide, di(p-chloro-benzoyl)peroxide and di(2,4-dichlorobenzoyl)peroxide.
5. A process according to claim 1, wherein said peroxydicarbonate is selected from the group consisting of di(4-tert.butylcyclohexyl)peroxydicarbonate, di(2-phenoxyethyl)peroxydicarbonate, dicetyl peroxydi-carbonate, dimyristyl peroxydicarbonate and dibenzyl peroxydicarbonate.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000526629A CA1277798C (en) | 1987-01-05 | 1987-01-05 | Process of crosslinking silicone rubber |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000526629A CA1277798C (en) | 1987-01-05 | 1987-01-05 | Process of crosslinking silicone rubber |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1277798C true CA1277798C (en) | 1990-12-11 |
Family
ID=4134677
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000526629A Expired - Fee Related CA1277798C (en) | 1987-01-05 | 1987-01-05 | Process of crosslinking silicone rubber |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1277798C (en) |
-
1987
- 1987-01-05 CA CA000526629A patent/CA1277798C/en not_active Expired - Fee Related
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