CA1069243A

CA1069243A - Composition with selected vinyl compounds and process for avoiding scorching of ethylene polymer composition

Info

Publication number: CA1069243A
Application number: CA239,200A
Authority: CA
Inventors: Donald L. Schober
Original assignee: Union Carbide Corp
Current assignee: Union Carbide Corp
Priority date: 1974-11-27
Filing date: 1975-11-03
Publication date: 1980-01-01
Also published as: BR7507823A; FR2292739B1; GB1529844A; SE7513321L; DE2553066A1; NL7513807A; FR2292739A1; DE2553066C3; JPS548500B2; IT1049814B; DE2553066B2; SE413900B; BE835966A; JPS5177647A; AU8695075A; IN144419B; US3954907A

Abstract

ABSTRACT OF THE DISCLOSURE
Vulcanizable ethylene polymer based compositions which are susceptible to scorching when processed at elevated temperatures, prior to vulcanization, in the presence of certain organic peroxide compounds, are protected against such scorching by the incorporation therein of monomeric vinyl compounds having the structure A-?=CH2 wherein R"' is C1-C3 hydrocarbon and A is phenyl, C1-C6 hydrocarbon substituted phenyl, or R°-O-?- wherein R° is a C4 to C20 hydrocarbon radical. The hydrocarbon radicals are devoid of allyl or vinyl unsaturation.

1.

Description

( 975 ~ Z ~ 3 BAClCGROUND 0~ THE_INVENTION
ield of the Invention The invention relates to the prevention of scorching, prior to vulcanization, of peroxide curable ethylene polymer based compositions.
Description of the Prior Art Insulation compositions which are employed on electrical wire and cable are, in many cases, pre-pared from compositions which are based on vulcanizable, - 10 or cross-linkable, ethylene polymers. These ethylene - polymer based compositions may be vulcanized, or cured, or crosslinked, with various organic peroxide compounds, as disclosed for example in United States Patents,

2,826,570; 2,888,424; 2,916,481; 3,079,370 and

3,296,189.
In the organic peroxide compounds which have - been used to date for commercial purposès in these F~
vulcanizable ethylene polymer based compositions, each vxygell atom in the peroxide group, i.e., -0-0-, o~
.
such compounds is directly attached to a carbon atom o~ an organic radical. The commercially useful com-positions do not employ hydroperoxide compounds therein as curing agents because they have relatively high decomposition temperatures, and the free radicals ~
p-:ovided by the decomposed hydroperoxides are not -effective for cross-linking ethylene po~mers.

20 ~ -'' ~ `'` ' ' ' ~$ ' L, . . '' t 9752 r ~ ~06~3 In order to process the orgar,ic peroxide con~aining compositions so as to adapt them to be placed, as insulation, on the electrical conductor components of the wire and cable it is usually neces-sary to admix the components o~ the compositions at high temperatures, and to extrude them, again at high ; temperatures, onto the electrical conductor. These processing activities occur prior to the intended vulcanization of the peroxide containing compositions, - 10 which is usually accomplished after such compositions ~ ;~
.. . . . ~ ~
are extruded onto the electrical conductor.
It has been found, however, that when certain - of the organic peroxide compounds, such as dicumyl peroxide, are usèd in combination with certain types o~ ethylene polymers or in certain types of ethylene polymer based compositions, that the entire curable composition is susceptible to scorching during the high temperature processing thereof prior to the vul~
canization of the composition on the electrical -. . - . , . : .
-20 conductor. Scorching is, in effect, the premature vulcanization of the insulation composition. This premature vulcanization usually occurs, when it occurs, in the barrel or die head of the extruder in which the . . . .
insulation composition is being processed, at elevated temperatures, prior to its being extruded onto an electrical conductor, and prior to its intended w 1- ;
canization. When an insulation composition is scorched ,, , , ' ' , ' i 3.

.

J69;~43 in thc ~tL~Ider, the extruded composition will have imper~ections in the form of discontinuity and rough-ness in the surface of the extrudate; and lumps or surface ripples caused by ge]L particles in the body of the extrudate. In addition, excessive scorching may cause enough of a pressure build-up in the extrusion device to require a cessation of the extrusion opera-tion entirely.
The tendency of a composition to experience -10 scorch is a relative matter, since any vulcanizable ethylene polymer based composition can be made to scorch i~ processed under conditions designed to pro-duce such result. IJnder a given set of conditions - some compositions are more prone to scorching than are others.
Compositions which have been found to be more susceptible to scorching under a given set of conditions a~e those in w~ich the ethylene polymer has a relatively low melt index and/or a relatively narrow ~0 molecular weight distribution.
The tendency of a composition to scorch under commercial operating conditions may be measured by means of the Monsanto Rheometer Test Procedure.
The Monsanto Rheometer Test Procedure is described in AST~I-D-2084-71T.
, Prior to the work of the present in~entor as disclosed in this patent application, and three others .,

4.

;' ~ ' ' ( filed on even date herewith, scorch prevention has been accomplished by the use of additives such as nitrites as disclosed in U.S. 3,~02,648, the specific antioxidants and vulcanization accelerators disclosed in U.S. 3,335,124; and the chain transfer agents dis-closed in U.S. 3,578,647. A mixture of two specific peroxides has also been used to provide a rate of cure - tha. is intermediate the rate of cure of either of such ;
peroxides, as disclosed in U.S. 3,661,877.
.
Sulmn-ary of the Invention `~
.
It has now been found that vulcanizable ethylene polymer based compositions which employ certain classes of organic peroxides therein as vulcanizing agents, and which compositions are susceptible to scorching under a given set of conditi~ns, can be protected against scorching under such conditions by incorporating in such compositions certain monomeric monof~r~ctional vinyl compounds. - .
An object of the present invention is to 20 provide slcorch resistant, vulcanizable, ethylene polymer based compositions.
- Another object of the present invention is to provide a process for protecting against scorching vulcanizable ethylene polymer based compositions which employ therein certain classes of organic peroxides as vulcanizing agents and which are susceptible to scorching.
A further object of the present invention is ;

:, -. . :
- - - - - ... . . ~ .
. . ~ .

to provi~lc scorch resistant insula~ion for electrical wire and cable.
A further object of the present invention is to provide a process whereby vuLcanizable ethylene polymer based compositions which employ therein certain classes of organic peroxide compounds as vulcanizing agents and which compositions are susceptible to scorch-ing, may be processed in mixing and extruding devices, ` prior to the vulcanization thereof, at fast throughput rates and at relatively high`processing`temperatures without experiencing scorching.
These and other objects of the present inven-tion are achieved by employing certain monomeric vinyl compounds as scorch preventing agents in the compositions of the present inventions.
: .
THE DR~UINGS
-; ` -Figures 1 and 2 of the drawings show, graphi-; cally, Monsanto Rheometer Test curves which were used to illustrate the derivation of an efficiency factor as ;~`
. . . .
described below. ` ~ `
. ~ . , .

DESCRIPTION OF THE PREFERRED EMBODIMENT
` The Scorch Kesistant Composition . Thl2 scorch resistant compositions of the present invention comprise, in weight ratio, 100 parts by weight of ethylene polymer, about 0,1 to 5.0, and preferably 0.2 to 2.0, 6.

~? ''i ' ' 97s~
692a~3 parts by weight of at least one peroxide c~mpound which has carbon atoms directly bonded to each oxygen atom of cach pero~ide group (-0-0-) therein, and which compounds, as a class~ are described below, and about 0.2 to 5.0, and preferably about 0.5 to 3 0 parts by weight of at least one vinyl compound of the class described below.
Ethylene Polymer - The ethylene polymers which are used in the ~`- 10 compositions of the present invention are solid (at ~ J
25C.) materials which may be homopolymers, or co- "
polymers of ethylene. The ethylene copolymers contain -- -at least 30 weight percent of ethylene and up to about 70 weight percent of propylene, and/or up to about 50 weight percent of one or more other organic compounds which are interpolymerizable with ethylene. These other compounds which are interpolymerizable with ethylene are preferably those which contain poly-merizable unsatura~ion, such as is present in compounds 1`
contain~ng an ethylene linkagej ~ C = C ~ . These other interpolymerizable compounds may be hydrocarbon compounds such as, butene-l, pentene-l, isoprene, butadiene, bicycloheptene, bicycloheptadiene, and styren~, as well as vinyl compounds such as vinyl acetate and ethyl acrylate.
These copolymers could thus include those containing ~ O to 70 weight percent of propylene and-. ,, . _ , .
., , . ~ , . . .
7- ; -~0~92~3 30 to ~ 100 wci~ht percent of ethylene; and ~ O to ~ 50 weight percent of butene-l or ethylene vinyl acetate and 50 to < 100 weight percent of ethylene; ;,,,~, and ~ O to ~ 30 weight percent of propylene, > O to 20 weight percent of butene-l and 50 to < 100 weight percent of ethylene.
The ethylene polymers may be used individual-ly, or in combinations thereof. The ethylene polymers ' have a density (ASTM 1505 test procedure with condit-ioning as in ASTM D-1248-72) of about 0.86 to 0.96 and a melt index (ASTM D-1238 at 44 psi test pressure) of '`' about 0.1 to 20 decigrams per minute. , - -PEROXIDE COMPOUND ''' .
The peroxide compound which is employe~ in the compositions of ,the present in~ention is employed ' therein as the primary w lcanizing agent for the ~-ethylene polymers. These compounds are organic per-' oxides which have a decomposition half-life of about 0.5 to 4.5 minutes, and preferably of about 1 to 2 ' minutes, at 160-200C., and preferably at 180-190C., and which'h~ve the structure ' `' CH3 ~ ~CH3 CH3 CH~ ~
R~ - C - O - O - C - R C - O - O - C- -R" , CH3 CH3 n CH3 CH3 , ,", wherein R is a C2 to Cl~ saturated or '' '"
: , .
l unsaturated divalent hydrocarbon radica~

~ , , . - .
8. ;
-, ~ ~9 ~ ~ 3 R' and R" are the same or different Cl to ~12 saturated or unsaturated monovalent nydrocarbon r~dicals, and n is a whole number of 0 or 1.
The R radicals would include aromatic hydro-carbon radicals such as phenylene, and saturated and u~saturated linear C2 to C4 hydrocarbon radicals such as ethylylene(C_C-) and ethylidene (-CH2-CH2-). The R, R' and R" radicals may be unsubstituted, preferably, or they may be substituted with inert inorganic radicals such as Cl.
` The preferred o~ ~he peroxide compounds are those wherein R' = R". -When n is 0 the peroxide compounds would include (with their decomposition half-life at 180C.) di -dC- cumyl peroxide. (0.8 to l.2 minutes), -- di -~ , p - cyml peroxide (0.6 to 1.0 minute) and - di-t-butyl peroxide (3.0 to 3.1 minutes).
Wnlen n is 1 t~le peroxide compounds would include (with their decomposition half-life at .
18~C.) : ` ~`
bis (t-butyl peroxy)di isopropyl benzene (1.0 ~o 1.3 minutes), - , ~ . .
2,5-dimethyl-2j5-di(t-butyl peroxy) hexane (1.2 to 1.4 minutesj and 2,5-dimethyl-2,5-di(t-butyl peroxy) hexyne-3, (4.2 to 4.4 minutes).

9, - - ' . -- : ~
,. . .

~0~9~43 9752 The peroxide compounds can be used individually or in combination with one another.
The peroxide compounds which may be used in the compositions of the present i~vention may also be generally classified as those in which each oxygen atom of each peroxide group is directly bonded to a tertiary carbon atom whose remaining valences are attached to hydrocarbon radicals selected from the group consisting of alkyl, cycloalkyl, alkyl cycloalkyl, aryl and aralkyl. Peroxides of this type are generally disclosed in U.S. 2,~88,424.
The peroxides are also generally used in cross-linking effective amounts.
Monomeric Monofunctional Vinyl Compounds The monomeric monofunctional vinyl compounds which can 4e used-in the compositions of the present invention have the structure A - C = CH2 in which R" ' is a Cl to C3 hydrocarbon radical, A is an unsubstituted phenyl~
radical, a phenyl radical substituted with one to five Cl to C6 hydrocarbon radicals, o~ R - 0 - C
in which R is a C4 to C20 hydrocarbon radical. The R~
and R hydrocarbon radicals, as well as the substituent . : :
hydrocarbon radicals for the phenyl radical may be~aliphatic or aromatic, and are devoid of allyl or vinyl unsaturation.
The monofunctional vinyl compounds would include `~:
-mèthyl styrene, lauryl methacrylate, n-butylmethacrylate, stearyl methacrylate, and p-methyl- ~ -m~ethy~ styrene. ~ i About 0.1 to 5, and preferably about 0.5 to-3.0 parts by weight of the monofunctional vinyl compound is used per part by weight of the peroxide compound.
t .' . `.
ln ~ .:

0~ 9 ~ ~ 3 The monofunctional vinyl com?ounds may be used individually or in combination with each other.
Adjuvants In addition to the ethylene polymer, the peroxide compound and the monomeric vinyl compounds, the compositions of the present invention also advantageously include about 0.01 to 3.0 and, preferably 0.05 to 1.0, parts by weight of one or more suitable high temperature antioxidants for the ethyIene polymers, per 100 parts by -10 weight of ethylene polymer in such compositions.
.
These antioxidants are preferably sterically hindered phenols. Such compounds would include 1,3,5-trimethyl-2,4,6-tris(3,5-ditertiary butyl-4-hydroxy benzyl)benzene; 1,3,5-tris(3,5-ditertiary butyl -4-hydroxy benzyl)-5-triazine-2,4,6~ ,3H,5H)trione;
tetrakis- [methylene-3-(3',5-di-t-butyl-4'-hydroxy ` phenyl)-propionate] methane; and di(2-methyl-4-hydroxy-

5-t-butyl phenyl)sulfide. Polymerized 2,2,4-trimethyl dihydroquinoline may also be used. ~ -Other adjuvants which may be employed in the compositions of the present invention would include ; adjuvants commonly employed in vulcanizable ethylene ; polymer based compositions inciuding fillers, such as carbon black, clay, talc and calcium carbonate; blowing i agents; nucleating agents for blown systems; lubricants;
.
UV stabilizers; dyes and colorants; voltage stabilizers; ~
.~ .
metal deactivators and coupling agents.
These adj w ants would be used in amounts ~

'. , ' ' ' ~':

975~
.

92~3 designed to provi~e the in~ended efect in the ~esulting composition.
The compositions of the present invention may also be e~tended, or filled, with polymers other than the ethyLene polymer which are compatible, i.e., can be physically blended or alloyed, with thP ethylene polymer. The resulting composit:ions should contain at least about 30 weight percent of interpolymerized ethylene in all the polymers that may be present in the composition, based on the total weight of the resulting composition. The other polymers which may be used would include polyvinyl chloride and poly-propylene.
The total amount of adjuvants used will range from 0 to about 60 weight percent based on the total weight of the composition.

.
Processing of the Compositions All of the components of the compositions of the present invention are usually blended or compounded together prior to their introduction into the extrusion device from which they are to be extruded onto an elec-trical conductor. The ethylene polymer and the~ other desired constituents may be blended together by any of ~` the techniques used in the art to blend and compound thermoplastics to homogeneous masses. For instance, the components may be fluxed on a variety of apparatus including m~Llti-rolL mills, screw mills, continuous - ~

. ~ , ' ',.

,, ' :

i~l692~3 mixers, compounding extruders and Banbury mixers, or dissolved in mutual or compatible solvents.
When all the solid components of the compo-sition ar~ available in the Eorm of a powder, or as small particles, the compositions are most conveniently prepared by first making a bLend of the components, say in a Banbury mixer or a continuous extruder, and then masticating this blend on a heated mill, for instance a two-roll mill, and ~he milling continued until an intimate mixture of the components is obtained. Alter-natively, a master batch containing ~he ethylene - -polymer(s) and the antioxidant(s) and,-if desired, ; some or all of the other components, may be added to the mass of polymer. Where the ethylene polymer is not available in powd~r form, the compositions may be made by introducing the polymer to the mill, masticating it until it forms a band around one roll, after which a blend of the remaining components is added and the milling continued until an intimate mixture is obtained.
The rolls are preferably maintained at a temperatur~
- which is within the range 80C. to 150C. and which is below the decomposition temperatures of the per -oxide compound(s). The composition, in the form of a sheet, is removed from the mill and then brought into a form, typically dice-like pieces, suitable for sub-sequent processing.
After the various components of the ' ~ ~4 13. `
. ~,. ....

~- ~L~9~9L3 : coml~ositions oi the present invention are ur.iformly admixed and blended together, they are further pro-cessed, in accordance wi~h the p~ocess of the present invention~ in conventional extrusion apparatus at about 120 to 160C.
After being extruded onto a wire or cable, or other substrate, the compositions of the present inven-tion are vulcanized at elevated temperatures of about 180C. and preferably at > 215-230C. ùsing con-ventional vulcanizing procedures.
` De~ivation of Curing System Efficiency Factor `~` `
In the Monsanto Rheometer Test Procedure a sample of the vulcaniæable composition is measured in a - rheometer before the composition is subjèct to high temperature mixing or extrusion conditions. The test . ' . .
results are plotted as functions of inch-pounds of torque versus time. Thë compositions which are less susceptible to scorching are those that experience, after the minimum torque value is achieved, a delay in the rise of the torque values followed by a fast rise in the torque values to the level required for the intended end use of the composition being evaluated. -~
The Monsanto Rheometer Test Procedure is, in effect, a means for comparatively evaluating, graphic-ally, the susceptibility o different vulcanizable compositions to scorch. In this way the use of differ-ent curing agents, or curing agent ~ompositions, in .~

14 .

' .

~/52 ~; ~06~:43 such vulcanizable compositions, can also be graphically comp ared, For the purposes of the present invention, a procedure has now been devised whereby, using the graphical results of Monsanto Rheometer Test procedures, the efficiency of different curable compositions, rela-tive to the susceptibility of such compositions to scorching, can also be numerically comparedO By using this new evaluation procedure, a separate and distinct numerical-eficiency factor (E) can be assigned to each curable composition. To make these efflciency factors `~
more meaningful, for comparison purposes, they should : -be based on rheometer curves which are all obtained when the curable compositions being compared are evalùated under the same test conditions. In aIl the :
experiments reported herein the test samples were evaluated in a Monsanto Rheometer at a cure temperature of 360F., using a rheometer oscillation of 110 CPM
. and an arc of +5 20 There is also provided here below, the derivation of a numerical efficiency factor (E) for .
vulcanizable compositions. The derivation employs typical rheometer curves that were arbitrarily .rawn, and which are not based on actual experiments.
A t:ypical Monsanto Rheometer curve, as shown -graphically in Figure 1, contains several parameters which are used in the derivation of the efficiency .:
.

15. ` '' ,~-,' ~, ^~ . ' . . .

71J~
~69Z~3 factor (~). The optimum cure level (highest cross-link density)is designated as H. H is measured in terms of inch-pounds of torque on the rheometer test equipment.
A higher value for H corresponds to a higher cross-link den~ity.
The time, in minutes, required to reach 90%
of the maximum cure (H) is designated as CT. Thus, in Figure 1, H is 50 inch-pounds and CT is 5.5 minutes, --which is the time required to reach a level of 45 (or 90% of 50~ inch-pounds of-torque during the test -procedure.
The scorch time, ST, is defined as the point , in time, in minutes, at which the curve reaches a rheometer level o~ 10 inch-pounds of torque on the -upswing of the curve. In Figure 1, ST is about 2.1 :
- minutes. ;~
- In general, one is interested in getting to the maximum cure (H) as soon as possible. At the same `~
time, one wouId like ST to be as long as possible since -20 a longer ST means the vulcanizable composition being evaluated can be processed at a higher speed or at a ` higher temperature. That is, it would be less scorchy.
Thus it is important to discuss the time intervals between CT .md ST, or CT - ST since CT is, arbitrarily~
always longer than ST.
en, too, it is of interest to compare ST
with CT - ST since the best vulcanizable system would - 16.
..

y/~

be one whose ST is relatively long, and whose difference bet~een CT alld ST~ (CT - ST), would be relatively short.
Thus, the ratio ST/CT -- ST is of importance. The larger is this ratio, the less susceptible is the w lcanizable composition to scorching.
~ inally3 the times (I~T and ST) are related to the maximum cure point, H. Thus, if one can maintain the same ST, and yet reach a higher H, one can thereby provide a ~ anizable composition that is less susceptible to scorch. When vulcanizable compositions are cured by peroxide curing agent systems, particularly those using individual peroxides such as dicumyl peroxide, as you increase the value of H by simply adding more of the peroxide curing agent, you decrease ST.
- The efflciency of a particular curing agent system therefore, when used with~a ~iven vulcanizable composition, and cured at a given temperature, can be determined by multiplying H by ST / CT - ST or, as shown in Equation I;
- 20 E = H x ST (I) T T
- . .
~`~ The numerical efficiency (E) of the curing agent system shown graphically in Figure 1 therefore, would, be -~
. .
E ~ H x Sr~ = (50) (2 1? e 30~9 ~ ~
`` CT ~ ST5.5 - 2.1 17.

.

: , ' ;', , ~ ;'~ ' ' ''' ' .. ' '-'... ' '. :, . - - - ... , ,, .. : " . -, , - :

~92~3 To further illustrate the utility of this method, for ~he purpo~es of comparatively evaluating different vulcanizable compositions, reference is made to Figure 2 of the drawings in which there is graphic-ally presented typical Monsanto Rheometer curves 1 and 2 that were also arbitrarily drawn and which are not based on actual experiments.
It should be noted from a review of Figure 2 that the cure times CT_l for composition 1 and CT 2 for composition 2, are the same for both compositions and each curve reaches a relatively high torque level with the value of Hl (for composition 1) which is 70, being-relatively close to the value of H2 (for composi-tion 2) which is 62. ST_2 (for composition 2), however, is more than a minute longer than ST 1 (for composition ` 1), 3;2 vs 2.0 minutes. Thus, it is quite obvious from a rèview of these two curves that curve 2 represents the better cure system. If one maintains the same CT, and reaches almost the same maximum cross-link density tH), tXen increasing ST must lead to a better curing system, in accordance with the above definition of E.
A calculation of the relative numerical efficiencies of the curable compositions shown graphic-~ ally in Figure 2 is shown below:

- Efficiency (El) of composition 1, based on curve 1:

El = Hl x 'Tl = (70) (2) = 140 = 35.0 Tl ~ STl (6 - 2) 4 ~-~
i..
,.,~. .. .
18, - ~
' -; ;~ -. ~ . . .
.:

9 ~ ~ 3 ~f~icicncy (E~) of composition 2, based on curve 2:

E~ - H2 ~ = (62~ (3.2) = '98.4 = 70.8 ~2 ST2 (6 - 3~2) 2.8 lhus, t~is efficiency factor, E, is a useful parnmeter ~d it can be shown that in fact a higher value for E represents a better system, as defined above, ~nd represents improved utility for such better ; system. The use of this efficiency factor, E, can also apply to comparisons of Rheometer test curves where the maximum cure (H) shown in each curve is vastly differ-~- ent, since the caLculation of E is, in effect, a ~ Q`~
normaLization procedure.
The COmpQSitiOnS of the present invention have -an ef~iciency factor (E), as determined above, which is at least about 3, and is prefera~ly more than L0 to 15, units of such efficiency factor above the efficiency factor of such compositions in the absence of the `
monomeric vinyl compounds.
The foliowing examples are merely illustrative of the present invention and are not intended as a limitation upon the scope thereof.
~eneral Ad~ixing Procedure .
.
The w lcanizable compositions used in Ex-amples 1-28 below were all prepared by the following procedure~
About 100 parts by weight of the ethylene polymer were fluxed in a Banbury mixer at approximately 120C.

, ~
:, - 9 `' -- ' . .
.. , . ... .. ... . . . . . - .. . . ~ . .. -. ,., . . ::... . . . . -Y / ~ ~!
~ ~ 9 ~ ~ 3 The ack;i~ives, i.e., anti-oxidant, and the peroxide(s) and, where used, othcr adju~an~s, were then added to the fluxed mixture. The resulting composition was then blended for 2-3 minutes and then transferred to a 2-roll mill for sheeting. The hot rolled sheet was then chopped on a hot granulator to yield a chipped product.
The chips were then compression molded into plaques for use in Monsanto Rheometer test procedures.
-10 All of the rheometer data which was then obtained on the samples, unless otherwise stipulated, was obtained at 360F. (182.2C.).
Exampies 1-12 A series of 12 vulcanizable compositions were prepared and evaluated for Efficiency Factors, as dis-disclosed above. m e compositions were prepared as disclosed in the General Admixing Procedure above.
Each-composition contained 97.84 parts by weight of an ethylene homopolymer ~'~
having a density of 0.92 and a melt index of 1.6-2.2 (lP, L90C.) 1.96 parts by weight of dicumyl peroxide" and ;
0.20 parts by weight of di(2-methyl-4-hydroxy-5-2-butyl phenyl) sulfide.
I The compositions of Examples 1-2 were i~ control experiments designed to show the reproducibil-ity of the E values for the test samples. The ~, , ~ . :: :
20.
.

, ` ' .. .

,~ . . . .

~7s~
, ~6~243 i compositions o~ Examples 1-2 contained n~) mono-meric unsa~urated compound.
The compositions of Examples 3-12 were used to evaluate various unsaturated monomeric compounds - as candidate scorch retarders. Table I presented below lists the candidate monomer, ~he parts by weight thereof that was employed 9 and the resulting H, CT, ST and E values.

TABLE I
Candidate Parts by wt. H, CT, ST, Cure of Candidate in- Min- Mln-Examlple Retarder Cure Retarder lbs. u~ utes E
., . ` . : ....
- None - 40.5 5.8 1,88 19.4 2 None ~ ~ ` 42~0 5.7 1.95 21.8 3 n-octyl 1.11 43.0 4.9 1.53 19.8 acrylate 4 vinyl neo- 1.19 - 40.0 4.8 1.63 20.6 decanoate l-dodecene 1.01 36.0 5.0 1.8 20.3

6 allyl 1.11 34.0 5.2 2.0 21.2

7: 2 -methyl- 1.01 32.5 5.5 2.1 20.1 1-undecene

8 allyl phenyl 0.81 28.0 5.6 2.2 18.1 vinyl hexa- 1.62 28.0 5.0 2.0 18,7 decyl ether lauryl meth- 1.53 41.5 5.9 2.4 28,5 acrylate 11 cC-methyl O.71 41.0 5.4 2.2 28.2 styrene 12 n-butyl 0.86 _ 40~5 S.9 2;4 28.0 methacrylate 21. , . ~ ~

.. ' -"

1~692~3 A review of the results of these experiments indicates that it is only the unsaturated additives of Examples 10 to 12, which are representative of the scorch retarders of the present invention, that pro-vide substantial improvements in the E values.
The addition of the other unsaturated com-~ounds, in Examples 3-9, produced little or no incr~ase, if not a decrease, in the value of E.
The candidatP cure retarders of Examples 3-12 ` 1~ were added in equimolar concentrations.
Examples 13-18 ;~
A series of six vulcanizable compositions were prepared and evaluated for Efficiency Factors, as disclosed - above. The compositions were prepared as disclosed in the General Admixing Procedure above. Each composition -contained ~- -100 parts by weight of an ethylene vinyl acetate copolymer which contained 10% by welght of vinyl acetate and which had~a density of 0.92 and a melt index of 2.0 I 2Q (lP, lgoc?, 35 parts by weight of carbon black, : i . . . .. .
1.6 parts by weight of dicumyl peroxide, and ().5 parts by weîght.of polymerized 2,2,4 trimethyl dihydroquinoline.
l'he composition of Example 13 was a control which contained no monofunctional vlnyl compound. The . , .
compositions of Examples 14-18-were'us~ed to evaluate 22.

~. ... .
; - ~ : - -~O~i9Z~3 9752 various unsaturated monomeric compounds as candidate scorch retarders in the composition of Example 13. Table II presented below lists the candidate monomer, the parts by weight thereof that was employed, and the resulting H, CT, ST and E values.

TABLE II

Candidate Parts by wt. of H, CT, ST, Cure Candidate Cure in- min- min- :' Example Retarder Retarderlbs utes utes E

13 None __ 78.0 4.9 1.15 23.9 ''~

- 14 acrylate 1.11 72.5,4.6 1.2 25.6 , vinyl neo- 1.19 70.0 4.61.1 22.0 decanoate , ,~

16 2-methyl-1- 1.01 59.0 5.01.1 16.6 undecene, ,' .:
` ' ' 17 vinyl hexa- 1.62 58.0 4.51.2 21.1 decyl ether ' ' '''' `'' . ... ..
', 18 , lauryl meth-1.53 67.05.4 2.25 47,9 acrylate A review o~ the results of Examples 13-18 indicat~
that it is only the unsaturated additive of Example 18, which is representative of the scorch retarders of the ,' ~

- present invention, that provides' a substantial improvement ' ' in the E value of the composition of Example 13. ' ', Examples 19-23 ,l A series of five (5) vulcanizable compositions were prepared and evaluated for E~ficiency Factors, as disclosed above. The compositions were prepared as :
, . -, disclosed in the General Admixin~ Proced~re above. ,, ' ,, Each composition contained f ~ ~06~43 9752 lQ0 parts by weight of an e~hylene-propylene-diene terpolymer (Nordell 1500 resin sold by duPont) that contained about 16 mole percent (22.4 weight %) of propylene, and 83 mole per cent (77.5 weight %) of ethylene and a small amount : (about l m~le %) of an unidentified (diene) monomer, and 1.5 parts by weight of dicumyl peroxide.
The composit~on of Example 19 was a control which contained no monofunctional vinyl compound. The compositions of Examples 20-23 were used to evaluate various unsaturated monomeric compounds as candidate scorc~
retarders in the composition of Example 19. Table III
- presented below lists the candidate monomer, the parts by weight thereof that was employed, and the resulting H, - . CT, STj and E values. :
.~ . .
. TABLE III

. Parts by Candidate wt of H, CT, ST, Cure Candidate . in- min- min- . . :
. Example Retarder Cure Retarder lbs utes utes E .

19 None -- 114.0 3.88 0.61 21.3 vinyl neo- .l.l9 105.0 4.2 0.67 l9.9 : . decanoate .
; 21 - n-octyl 1.11 108.0 3.8 0.48 15.6 acrylate 22 allyl phenyl 0.81 84.0 3.9 0.75 20.0 ether ~ .

23 lauryl meth- 1.53 - 106.0 4.3 0.93 29.3 :
`~ acrylate i~ .A review of the results of Examples 19-23 , indicates that it is only the unsatur~ted additive of :.

- 24.
O .'`,' ' ' -g752 Example 2~, which is representative ol the scorch retarders of the present invention, that provides a substantial improvement in the E value of the composition o~ Example 19.
Examples 24-28 -A series of five (5) vulcanizable compositions were prepared and evaluated for Efficiency Factors, as disclosed above. The compositions were prepared as disclosed in the General Admixing Procedure above. Each composition contained about 73.8 parts by weight of an ethylene-vinyl acetate copolymer which contained 10% vinyl acetate and - - which had a density of 0.92 and a melt index of 2.0 (lP, 190C), 25.8 parts by weight of carbon black, -I
0.4 part by weight of trimethyl dihydroquinoline, and l.0 part by weight of ~,~ ' bis(t-butyl peroxy di-isopropyl)benzene.
. ., - . ~ .
-~' 20 The composition of Example 24 was a control - . .
which contained no monofunctional vinyl compound. The -~ :
compositions of Examples 25-28 were used to evaluate various unsaturated monomeric compounds as candidate cure retarders in the composition of Example 24. Table IV
presented below lists the candidate monomer, the parts by weight thereof that was employed, and the resulting H, ~- CT, ST, and E values.

`~

~: 25.

` ~69Z~3 9752 TABLE IV

Candidate Parts by wt of H, CT, ST, Cure Candidate in- min- min-: Exalnple Retarder Cure Ret:arder lbs utes utes E
24 Nonc -- 76.0 6.6 1.3 18.6 n-oc~yl 1.11 44.0 6.5 1.7 15.6 acrylate 26 l-dodecene - 1.01 67.0 6.7 1.45 18.5 27 vinyl neo- 1.19 78.0 6.4 1.25 18.9 decanoate 28 lauryl meth- 1.53 66.0 7.8 2.94 39.9 acrylate - - A review of the results of Examples 24-28 indicates that it is only the unsaturated additive of . Example 28, which is representative of the scorch retarders of the.present invention, that provides a substantial improvement in the E value of the composition o~ Example 24.
The candidate cure retarders were used in all the ` examples ~n equimolar amounts.
'' . ' - .
'` ' ' ' ' ' ~'"- - -. .

' ' ._ ' , . ..
, , ~ :
26. . `' -.

,. : ' ,-- : .. - ; - . .. . .. . . .. .

Claims

WHAT IS CLAIMED IS:

1. A scorch resistant vulcanizable composition comprising, in weight ratio, 100 parts by weight of ethylene polymer containing at least 30 weight percent of ethylene, about 0.1 to 5.0 parts by weight of at least one peroxide compound which has a decomposition half-life of about 0.5 to 4.5 minutes at 160 to 200°C. and has the structure wherein R is a C2 to C12 divalent hydrocarbon radical, R' and R" are the same or different C1 to C12 monovalent hydrocarbon radicals, and n is a whole number of 0 or 1, and about 0.2 to 5 parts by weight of at least one vinyl compound which has the structure A - ? = CH2 wherein R"' is a C1 to C3 hydrocarbon radical, A is an unsubstituted phenyl radical, a phenyl radical substituted with 1 to 5 C1 to C6 hydro-carbon radicals, or R°-0-?-wherein R° is a C4 to C20 hydrocarbon radical, with the proviso that the R"' and R° radicals and the phenyl substituents may be aliphatic or arom-atic and are devoid of allyl or vinyl unsaturation.

27.

2. A composition as in Claim 1 in which n = O.

3. A composition as in Claim 2 in which R'=R".

4. A composition as in Claim 3 in which R' and R" are phenyl radicals.

5. A composition as in Claim 3 in which R' and R" are methyl radicals.

6. A composition as in Claim 1 in which n = 1.

7. A composition as in Claim 6 in which R' = R".

8. A composition as in Claim 7 in which R is an aromatic radical.

9. A composition as in Claim 8 in which R is phenylene.

10. A composition as in Claim 9 in which R' and R" are methyl radicals.

11. A composition as in Claim 7 in which R is a C2 to C4 linear hydrocarbon radical.

12. A composition as in Claim 11 in which R' and R" are methyl radicals.

13. A composition as in claim 1 in which A com-prises a phenyl radical.

14. A composition as in claim 13 in which said vinyl compound is ? -methyl styrene.

28.

15. A composition as in claim 1 in which A is R°-O-?-.

16. A composition as in claim 15 in which said vinyl compound is lauryl methacrylate.

17. A process for preventing the scorching of a vulcanizable composition which is susceptible to scorching during the processing thereof at temperatures of about 120 to 160°C.
prior to the intended vulcanization thereof.
said composition comprising, in weight ratio, 100 parts by weight of ethylene polymer containing at least 30 weight percent of ethylene, and about 0.1 to 5.0 parts by weight of at least one peroxide compound which has a decomposition half-life of about 0.5 to 4.5 minutes at 160 to 200°C. and has the structure wherein R is a C2 to C12 divalent hydro-carbon radical, R' and R" are the same or different C1 to C12 monovalent hydrocarbon radicals, and n is a whole number of 0 or 1, which 29.

comprises admixing into said composition, prior to said processing, about 0.2 to 5 parts by weight of at least one vinyl compound which has the structure A - ? = CH2 wherein R "' is a C1 to C3 hydrocarbon radical, A is an unsubstituted phenyl radical, a phenyl radical substituted with 1 to 5 C1-C6 hydrocarbon radicals, or R°-0-?-wherein R° is a C4 to C20 hydrocarbon radical, with the proviso that the R"' and R°
radicals and the phenyl substituents may be aliphatic or aromatic and are devoid of allyl or vinyl unsaturation, and then processing the resulting com-position at 120 to 160°C. so as to form said composition into a desired shaped article and then vulcanizing the thus shaped article at a temperature of at least 180°C.

18. A process as in claim 17 in which A com-prises a phenyl radical.

19. A process as in claim 18 in which said vinyl compound is ? -methyl styrene.

30.

20. A process as in claim 17 in which A is R°-0-?.

21. A process as in claim 20 in which said vinyl compound is lauryl methacrylate.

22. The composition of Claim 1 in vulcanized form.

23. Electric wire or cable insulated with the composition of Claim 1 in vulcanized form.

24. A scorch resistant vulcanizable composi-tion comprising ethylene polymer containing at least 30 weight percent of ethylene, crosslinking effective amounts for said ethylene polymer of at least one peroxide compound in which each oxygen atom of each peroxide group is directly bonded to a tertiary carbon atom whose remaining valences are attached to hydro-carbon radicals selected from the group consisting of alkyl, cycloalkyl, alkyl cycloalkyl, aryl 31.

and aralkyl, and 0.2 to 5 parts by weight, per 100 parts by weight of said ethylene polymer, of at least one vinyl compound which has the structure A - ? = CH2 wherein R "' is a C1 to C3 hydro-carbon radical, A is an unsubstituted phenyl radical, a phenyl radical substituted with 1 to 5 C1 to C6 hydrocarbon radicals, or R°-0-? wherein R° is a C4 to C20 hydro-carbon radical, with the proviso that the R "' and R°
radicals, and the phenyl substituents may be aliphatic or aromatic and are devoid of allyl or vinyl unsaturation.

25. A composition as in claim 24 in which said peroxide compound comprises dicumyl peroxide.

26. A composition as in claim 25 in which said vinyl compound comprises lauryl methacrylate.

32.

27. A composition as in claim 25 in which said vinyl compound comprises ?-methyl styrene.

28. A composition as in claim 25 in which said vinyl compound comprises n-butyl methacrylate.

29. A composition as in claim 24 in which said peroxide compound comprises ?,?'-bis (tertiary butyl peroxy di-isopropyl) benzene.

30. A composition as in claim 29 in which said vinyl compound comprises lauryl methacrylate.

31. A composition as in claim 1 in which said ethylene polymer is a homopolymer.

32. A composition as in claim 1 in which said ethylene polymer is a copolymer of at least 30 weight percent of ethylene and up to about 70 weight percent of propylene and/or up to about 50 weight percent of one or more organic compounds other than propylene which are interpolymerizable with ethylene.

33.

33. A process as in claim 17 in which said ethylene polymer is a homopolymer.

34. A process as in claim 17 in which said ethylene polymer is a copolymer of at least 30 weight percent of ethylene and up to about 70 weight percent of propylene and/or up to about 50 weight percent of one or more organic compounds other than propylene which are interpolymerizable with ethylene.

35. A composition as in claim 24 in which said ethylene polymer is a homopolymer.

36. A composition as in claim 24 in which said ethylene polymer is a copolymer of at least 30 weight percent of ethylene and up to about 70 weight percent of propylene and/or up to about 50 weight percent of one or more organic compounds other than propylene which are interpolymerizable with ethylene.

34.