Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
10~7~9.~1
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This invention relates tv the graft copolymerisation
of thermoplastics with silane.
In the past polyolefines have been grafted with ole-
finically unsaturated silanes to give a graft copolyr.ler
capable of being extruded and shaped using normal plastics
processing apparatus but which by suitable treatment may be
subsequently crosslinked to give a rigid polymer oE high
softening point.
The polyolefines have hitherto been grafted by re-
action of molten polyolefine or polyolefine in solution withthe ol0finically unsaturated silane in the presence of
peroxides. This known process has the grave disadvantage
that the polyolefine must be molten or in solution in suit-
able solvent such as xylene during the reaction and hence
the resultant grafted copolymer must be subsequently converted
to granules at extra cost or be used immediately in a forming
operation. We have now found a process whereby granules or
o~her shaped articles of polyolefines may be grafted with
silane in the solid phase ko give a graft copolymer.
Accordingly we provide a process of manufacturing
a silane-grafted thermoplastic copolymer which process com-
prises treating in the solid form a thermoplastic shaped
polymeric article having a thickness up to 5 millimetres
and containing a radiation sensitizer as hereinafter defined
and a mono-olefinically unsaturated silane said silane con-
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`-` 10'7~991
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taining at least two hydrolyzable organic radicals with an
amount of electromagnetic radiation of wavelength in the
range of 180 to 800 nanometres (nm) sufficient to form the
said graft copolymer.
In a preferred embodiment of this invention the said
thermoplastic shaped article is in particulate form.
In a further preferred embodiment of this invention
the said article is in a sheet-like form.
The nature of the polymer from which the thermoplastic
shaped article is derived is not narrowly critical. Satis-
factory results have been obtained with both high and low
density polyethylene, and polypropylene. Polybutene-l,
poly(4-methylpentene-l), chlorinated polyethylene~ and chloro-
sulphonated polyethylene may be used. Blends of different
polyolefines may also be used.
The article may also be prepared from copolymers.
Typical examples of such copolymers include those derived from
ethylene and monomers such as vinyl acetate~ ethyl acrylate,
ethyl methacrylate, or acrylic acid partially or completely
neutralized.
The process of our invention may also be used for
other polymers such as for example nylon, polyethylene tere-
phthalate and polyvinyl chloride.
The silane is selected from the group having the
general formula
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R SiY
n (4-n)
wherein each R which may be the same or different is selected
from the group comprising monovalent olefinically-unsaturated
hydrocarbyl, alkoxyalkyl~ acyloxyalkyl, and acyloxyalkoxyalkyl,
each Y which may be the same or di.fferent is hydrolyzable organic
radical, and n is 1 or 2.
. Examples of R are vinyl, allyl, butenyl, cyclohexenyl,
cyclopentadienyl, cyclohexadienyl, (CH2=C~CH3)COOtCH2)3-,
CH2=C(CH3)COOCH2CH2CH20(CH2)3- and
: OH
~H2=C(CH3)COOCH2CH20CH2CHCH20(CH2)3-, the vinyl radical being
preferred. The Y substituents are selected from alkoxy or
alkoxyalkoxy radicals having less than 6 carbon atoms for ex-
ample the methoxy, ethoxy and butoxy radicals, acyloxy radicals
having less than 6 carbon atoms for example the formyloxy,
acetoxy and propionoxy radicals, and oximo radicals having less
. lS than 14 carbon atoms for example -ON=C(CH3)2, -ON=C(CH3)C2H5 and
-ON=C(C6H5)2.
Preferably the silane will have the formula RSiY3 and
contain three hydrolyzable organic radicals, the most preferred
silanes being vinyltriethoxysilane and vinyltrimethoxysilane.
Silanes having only two hydrolyzable groups for example vinyl-
~-`'' ' .
methyldiethoxysilane and vinylphenyldimethoxysilane, are
however also operative.
.
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_ 5 _ ,
The amount of the silane used is not narrowly critical.
Obviously the higher the amounts of silane the greater will be
the amount of grafting. However, amounts of silane in the
range from 0.1 to ?Q% w/w of the thermoplastic article~
preferably from 0.5 to 5% w/w give commercially effective
graft copolymers.
The proportion of silane employed will depend in part
upon the reaction conditions and in part on the degree of
modi*ication required.
By radiation sensitizer is meant a compound capable
of absorbing the electromagnetic radiation and promoting the
reaction of the silane with the said thermoplastic article.
Suitable radiation sensitizers for electromagnetic radiation
of any given wavelength are known to those skilled in the art.
Thus for example it is well known to those skilled in the art
that ketones such as for example acetone are suitable sensi-
- tizers for electromagnetic radiation of waveLength in the
region from 200 to 300 nm, and that certain natural products
such as for example riboflavin are suitable radiation sensitizers
. 20 for sunlight. Aromatic ketones such as benzophenone and aceto-
phenone are active for radiation with wavelength from 200 to
360 nm.
Sensitizers normally used by those skilled in the art
- include azo-bis-isobutyronitrile~ peroxides such as di-cumyl
peroxide, di-tert-butyl peroxide, benzil, and benzoin and
.
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benzoin derivatives such as benzoin methyl ether, allyl
benzoin methyl ether, benzoin isopropyl ether and methyl
benzoin methyl ether. Benzil, benzoin and benzoin derivatives
are actlve sensitizers for radiation of wavelength from 300 to
400 nm.
A suitable sensitizer for any particular wavelength
of electromagnetic radiation may be found by simple experi-
mentation.
The sensitizer may be added to the thermoplastic article
by any suitable method known to those skilled in the art for
the incorporation of additives into thermoplastic articles.
Suitable methods include melt mixing or compounding. Altern~-
tively in certain cases the sensitizer has a sufficiently high
vapour pressure for the sensitizer to permeate into a solid
thermoplastic article merely by keeping the solid thermoplastic
article in the presence of the vapour of the sensitizer.
The sensitizer may also be incorporated into the thermo-
plastic article by soaking the article in a liquid sensitizer
or in a solution of the sensitizer in a solvent. Preferably
the solvent is able to swell the thermoplastic article and thus
facilitate the penetration of the sensitizer.
The anlOUnt of the sensitizer and the d~ration and
intensity of exposure to the electromagnetic radiation are
preferably such that crosslinking of the polymer of the said
` 25 article is minimized during the process of the invention. When
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benzophenone an~ acetophenone are used as sensitizers in
the graft polymcrization of thermoplastic articles derived
from polyolefines~ amounts of the said sensitizers in the
range from 0.01 to 10% w/w of the polyolefine preferably
0.05 to 1% w/w of the polyolefine and using low powered
(15 to 30 watts) lamps with radiation in the range from 200
to 400 nm, particularly 254 nm, for from 5 minutes to 10
hours give good yields of graft copolymer. With higher powered
(2000 to 3000 watts) lamps the irradiati~n time is reduced and
irradiation times from 15 to 60 seconds give excellent yields.
~ lthough the thermoplastic may be irradiated prior to
addition of the silane we prefer that the thermoplastic is
irradiated in the presence of both sensitizer and silane.
The process of the invention may be used at all
temperatures up to the melting point of the polymeric component
of the said thermoplastic article. Preferably the temperature
is between 0C and a temperature about 20C below that of the
softening point of the said thermoplastic article.
The thermoplastic articles may optionally be subjected
to successive treatments with radiation by the process of
this invention to produce high levels of grafting.
The resultant graft copolymers of this invention are
not crosslinked and can be moulded and caused to flow in a
manner acceptable for processing with conventional moulding
.5 and extrusion equipment. When the graft copolymer is exposed
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to water, most usually in the presence of a condensation
catalyst such as dibutyltin dilaurate, then the graft co~
polymer may be converted to a crosslinked form. Suitable
methods of inducing crosslinking and of working silane poly-
olefine graft copolymers are known to those skilled in theart.
The polymeric materials from which the thermoplastic
shaped articles of this invention are derived include not
only polymeric materials in their natural state but also
include polymeric compositions comprising one or more con- ,
ventional additives such as for example stabilizers, fillers,
lubricants~ slip additives, antioxidants, antistats and the
like. Since the process o f this invention is conveniently
performed at temperatures below the temperatures normally used
in conventional plastics compounding processes, it is parti- -
cularly suited for plastics compositions containing materials
whicll are prone to degrade in conventional processes. Other
additives which could prevent transmission of the electro-
magnetic radiation may be incorporated into the grafted product
made by the process of the invention before any crosslinking
step is performed. Such additional additives include dyes,
pigments, mineral fillers, non-conductive carbon black and
conductive carbon black.
1~'7~g~ ~
_ 9 _
The invention will now be illustrated by, but
by no means limited to~ the following examples. All per-
centages are on a weight basis.
Example 1
Low density polyethylene was melt mixed with a solu-
tion of benzophenone in vinyltriethoxysilane and extruded to
give cylindrical granules of diamcter 4 mm and 2-3 mm thick.
The granules were then irradiat~d under a 15 watt
germicidal lamp emitting a major proportion of light at 254 nm.
The proportion of reagents and results are shown in Table 1.
; TABLE 1
. . _ _ _ .
Rxperi- % ~ ation Gel content (~)
ment benzo- silane time ,_
No phenone
~hrJ After After
, _ irrad3ation crosslinking
1 0.025 2 1 0 2
2 0.1 2 1 1 29
3 0.1 2 2 2 42
0.1 3 1 0 39
0.25 2 1 8 _ 30
The gel content is the insoluble content after 16 hours ex-
tracting with boiling xylene.
The gel content after irradiation is a measure of the
;~.~ . .
amount of crosslinking occurring during irradiation.
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Thc gel content after crosslinking the graft copolymer
with water in the presence of dibutyltin dilaurate is a
measure of the grafting efficiency.
Example 2
Mixtures of melt mixed low density polyet.hylene
prepared by the method of Example 1 were pressed into a film.
The film was irradiated as in Example 1. The results are
shown in Table 2.
TABLE 2
. ~ _ _
Film Irradi- Gel content (%)
Experi- % % thick- ation _
ment benzo- silane ness time irradi- cArOters_
ation linkin~
l 0.025 2 500 1 0 2
2 0.1 2 125 1 5 39
3 0.1 2 500 1 2 42
4 0.1 .2 500 2 5 48
0.1 3 500 1 1 so
6 0.25 2 500 l6 44
ExamPles .s to 36 inclusive
For these examples a Philips TUV 30 watt lamp was used
except where indicated.
Examples ~I to 8 inclusive
These examples illustrate the effect of variation in
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10'7~99~
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irradiation time on the gel content after grafting and after
crosslinking. The polyethylene was a commercial sample
designated XJG143 and having a density of 0.922, and a melt
flow index of 2.5, and in granular form of 5 mm thickness.
Benzophenone (0.1% based on the polyethylene to be
grafted) was dissolved in vinyltriethoxysilane (2% based on
polyethylene) and compounded into the polyethylene granules.
The granules were then exposed to radiation from the lamp for
various times and the gel content after grafting and after
crosslinking measured as described in Example 1. The lamp
surface was placed in contact with the granules to provide the
maximum intensity of radiation. The temperature rise in the
granules with this procedure was low, and no cooling was re-
quired. The results are shown in Table 3. The granules were
irradiated from both sides and the two figures in the
~irradiation time" column refer to these two treatments.
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_ I d at on Gel content (%)
Example time (minutes) After After
. grafting crosslinking
3 2.5/2.5 o 18 -
4 8/8 1 46
15/15 2 52
622.5/22.5 3 61 .
7 30/30 5 62
8 60/60 __ 15 65
Examples 9 to 11 inclusive
: These examples illustrate the effect of variation in
the distance between the source of irradiation and the polymer
5 on the gel content after grafting and after crosslinking.
The conditions of Example S were used~ except that the
distance between the surface of the lamp and the surface of
the granules was varied between 2.5 cm and 10 cm. The re-
duction in gel content after crosslinking as the distance from
.~ 10 the lamp increased is shown by the results in Table 4.
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TABLE 4
_ .... ........ _ _ Gel content (%)
Distance from
Example , ~ .
lamp ~cmJ After After
grafting crosslinking
, _ _ _ . ~ .
9 2.5 1 33
2 24
11 I~l 2 ~6
ExamPles 12 and 13
These examples illustrate the effect of variation in
silane content on the gel content before and after cross-
linking.
For Example 12 and 13 conditions of Example 5 and 6
respectively were used~ except that the concentration of
vinyltriethoxy-silane was 3% (based on polyethylene).
The results are shown in Table 5.
.10 . TABLE 5
. .
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Gel content (%)
: Example .. _... ....
: After After
grafting crosslinking
. 12 - _
13 1 4 1 61
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These examples show the effect of variation in ¦ -
sensitizer concentration of the gel content after grafting
and aftcr crosslinking.
For Examples 14 to 17 inclusive the conditions of
Example 7 were used except that the lamp of that example was
replaced by a Philips TL 20 watt lamp and the concentration
of benzophenone (based on pol~ethylene) was varied as shown. The
results are shown in Table 6.
TABLE 6
,' , _ . ~.
Gel content (%)
Example Benzophenone (%) .
After After
grafting crosslinking
_ _
14 0.1 48
0.15 1 60
16 0.2 2 61
~ 17 0.3 6 _ 7
,:
Examples 18 to 20 inclusive
These examples show the effect of addition of anti-
oxidants. The conditions of Example 6 were used~ except
that 0.05% (based on polyethylene) of antioxidant was added.
~Flectol" H is 2~2~4-trimethyl-1-hydroquinoline ~"Flectol~ is
a registered trade mark). ~Santanox~l R is 4,4t-thiobis(6-
tert-butyl-m-cresol) (IlSantanox'l is a registered trade mark).
l~ ade~.
107~
- 15
t~Topanol~ OC is 2j6-ditert-butyl-p-cresol and ~Nonox" WSP
is 2,2t-methylene-bis-/~-(1-methylcyclohex~l)-p~cresol)7.
(I~Topanol'l and ~Nonox~ are registered trade marks of Imperial
Chemical Industries Limited).
The results are sho~n in Table 7.
TABL 7
. ~
Example Antioxidant After After ~
grafting crosslinking
, -- r -- _ _ , _ .
18 ~'Flectol" H 7 37
19 "Santanox~ R 6 5o
IlTopanol~ OC 3 6l
ExamPles 21 to 25 inclusive
These examples illustrate the effect of variation in
type of polymer. The conditions of Example 5 were used except
that the XJG143 granules of that example were replaced by
granules of
equal weights of/the following polymers derived from ethylene.
Dasignation , Density Melt flow
. . , .
1503~ 0.915 60
XRM21 0.921 20
WJG117- 0.918 1.8
EVA 28-os _ 5
Wl~760 _ 1.2
,
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EVA 28-05 is copolymer derived from ethylene and vinyl
acetate
acetate and wherein the vinyl/units constitute about 28% of
the copolymer. The results are shown in Table 8.
TABLE 8
. . . _
Gel content (%)
Example Polymer _
After After
grafting crosslinking
__ _ _ r
21 1503I, 14~ 53
22 XRM21 O 39
2 3 WJG117 21 63
24 EVA28-05 40
GDVP4760 11 32
Examples 26 to 36 inclusive
These examples illustrate the effect of variation in the
quantity and nature of the sensitizer on the gel content after
grafting and after crosslinking. For Examples 26 to 35
inclusive the conditions of Example 5 were used except that the
benzophenone of that example was replaced by the sensitizers
shown in Table 9. For Example 36 the conditions of Example
6 were used except that halP of the benæophenone of that
example was replaced by an equal weight of acetophenone. The
results are shown in Table 9.
:~ 107~9~
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TABLE 9
,.' . . . , , . . ~ .
Sensitizer (% based Gel content
Example on polymer) ~
After After
.. grafting crosslinki.ng
., , . . . _ . ~ __
.: 26 0.1% acetophenone 0 55-
2y 0.2% t 2 66
. 28 ~3% tt 13 72
:~. 29 0.1% benzaldehyde 0 41 . .
. 3 0.3% '' 2 61
.. 31 -3% p-tolualdehyde 2 55 .
32 0.2% dicumyl peroxide 0 45
33 0.1% 2-methylanthraquinone 5 25
34 0.1% anthrone 4 18
0.1% benzil 14
36 (-$% benzophenone 2 60
. . (0.05% acetophenone
.' . ~ . ................. ,
Exam~les 37 to_ ~ inclusive
In these Examples a 4Ormulation was prepared by
- dissolving the sensitizer and anyadditional agents in the
- 5 silane and compounding - . into the polethylene granules
, at 60 C. The grafting was carried out by exposure of the
.
granules to the radiation from a Philips HPM 15 2000 watt
lamp which is a high-pressure mercury-vapour lamp emitting
.. multiple bands of radiation in the region of 2~0 to 365 nm.
The temperature at the surface of the lamp was above the
,. ........... . . .
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-- 18
.
melting point of the granules and the granules were there-
for placed 120 5 cm from the surface of the lamp to allow air
cooling of thc granules.
The granules used were commercial polyethylene designated
S XJG 143 except where indicated. ET 3042, ET 901, and XNM 158
are designations of commercial polyethylene. ET 3042 has a
density of 0.922 and a melt flow index of 7. ET 901 has a
density of 0.926 and a melt flow index of 2.5. XNM 158 has
a density of 0.926 and a melt flow index of 1.8.
HM 61 is the designation of a commercial grade of
polypropylene. The silanes of thesè examples are as follows:
Silane A = vinyltriethoxysilane
Silane B = t~-methacryloxypropyltrimethoxysilane
Silane C = vinyltrimethoxysilane
In the irradiation-time column of Table 10 a single
figure for the time of irradiation indicates that a single
exposure was made from one side of the layer of granules.
Two figures indicate that two exposures were given. Where
the figures are separated by a stroke the exposures were given
on opposite sides of the layer of granules. The "+" signifies
that the granules were tumble mixed after the flrst exposure~
and the second exposure was then applied without moving the
lamp.
After irradiation the grafted polymer was crosslinkèd
by boiling with an emulsion of 0.1~ dibutyltin dilaurate in
7~99~
-- 19 --
water for 17 hours. The gel content after graf~ing and
after crosslinking was measured as desc~ibed in Example 1.
The results obtained are shown in Table 10.
TA~LE 10
_ -- .
. Gel content (%)
Irradiation
Example Formulabiontime After After
(seconds) graft- cross-
ing linking
. . ~. _ , _
.: 372% silane A 30 ' o 52.8
0.1% benzophenone
0.1% dimethylaminoethanol
38 2% silane A 30/30 o.6 74.5
o .4% benzophenone
39 2% silane A 30/30 4.8 78.4
o.5% benzophenone
2% silane A 30+30 1.2 71.8
0.4% benzophenone
41 2% silane A 30/30 0.2. 74.3
0.7% acetophenone .
. 42 2% silane A 30/30 o.3 52.6
: . . o.5% dicumyl peroxide
43 2% silane B 30/30 1.2 72.9
~ o.35% benzophenone
: 44 2% silane C 30/30 o.3 77. o
. o .35% benzophenone
;~ 45 2% silane C 30/30 O.5 68.7
o.35% benzophenone
o . o5% dibutyltin dilaurate
46 1. 5% silane C 30/301. 2 72.9
o.35% benzophenone
. 47 2% silane A 30~30 o 51.4
. 0.3% benzaldehyde
48 2% silane A 30+30o. l 58. o
.3% tolualdehyde ~ _ _
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- 10~9~
- 20 -
TABLE 10 Continued
_ , , ,__
,. l Gel content (%)
Irradiation _. .
Example Formulation time Af~er After .
(seconds) graft- cross-
ing linking
. .-_ _ __ . . _ =_
49 2% silane A 30~30 0.1 62.9
0.5% tolualdehyde
5o2% silane A 30+30 4 . o 55 . 7
0.1% 2-methylanthraquinone
5~2% silane A 30 1. 5 56. 8
. 0.1% benzophenone
WJG 117 granules
522% silane A 30/30 0.8 65 . 8
0.4% benzophenone
XRM21 granules
532% silane A 30/30 o.6 68.7
0.4% benzophenone
ET3042 granules
542% silane A 30/30 l. 6 69 . 8
0.35% benzophenone
ET901 granules
. 552% silane A 30/30 0. 8 61. 2
0.35% benzophenone
XNM158 granules
562% silane A 30/30 1. 4 70. 6
0.35% benzophenone
: EVA28-05 granules
. 572% silane C 1 30/30 0 55.8
0.35% benzophenone
. polypropylene granules _ .
E ~
Granules of low density polyethylene (XJG 143) were com-
pounded with a solution of benzophenone (0.35% based on
j polyethylene) in vinyltriethoxysilane (2% b-sed on poly-
; ' ,
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1(~'7~991
_ 21 -
ethylene). The granules were pressed at 140C to give
plaque,s of 1.3 mm thickness.
The p]aques were grafted by irradiating them with a
Phillips HPM-15 lamp for 30 seconds from each side and then
the graft polymer crosslinked by boiling with an aqueous
emulsion of 0.1% d;butyltin dilaurate. The gel content measured
as described in Example 1 was o.6% after grafting and 73.6
after crosslinking.
ExamPle 59
Example 58 was repeated except that the vinyltrieth
oxysilane was replaced by vinyltrimethoxysilane. The gel
conte,nt was o.6% after grafting and 75 . 4% after crosslinking.
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