Note: Descriptions are shown in the official language in which they were submitted.
WO93/13161 PCT/NO92/00194 .. ~
2126~~7~. ` `: `
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Method for productional thermostable chemical resistant Dlastics
The invention concerns a procedure for the production of
thermostable chemical-resistant plastic. Extremely high .`.
resistance to chemicals can be achie~ed if a strong, homogenous
~ross-linked network is introduced inta the polymer. Thi.s type of
polymer will be particularly suitable for applications where oil~
resistance is important, fo~ example in oil booms. It is also .
suitable for foils, tarpaulins, membranes and as a hard-wearing ~:
top layer for floor coverings. Cables, pipes and rainwear ~an ~- `
also be mentioned as potential application areas.
In the case of PVC in particular, cross-linking has long been
considered a good method of improving t~e me~hanical properties
of this plastic at high temperatures. ~any attempts havé .
therefore been made to find technical solution~ to t~is pro~lem.
The in~roduction of cross-linking with the aid of so-called
reactive plasticizers, such as difunctional and trifunctional
acrylates or methacrylatesl has had some commercial success.
These reagents are added in quantities of 20-50 pph (pph = p~rts ~`
per hundred parts of polymer), and they are cross-~inked by
exposure to radiation or free radicals. The network that is
formed is strong and heterogeneous, which leads to a considerably ;:
more brittle finished product. At the same ~ime this ~echnique
can easily reduce the thermostability of the product because of `~-
the degrading effect of the radiation or the free radicals (see ~;
for example W. A. Salmon ~ L. D~ Loan; J. Appl. Polym. Sci., 16.,
67l, (1972)).
A homopolymer of polyvinyl chloride (PVC) has a certain content
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WO93/13161 ~ PCT/NO92/00194
of reactive groups, inasmuch as the carbon-chlorine bond is polar
i" ,,
and may be attacked by nucleophilic compounds. In particular,
thiolate ions have proved to be good nucleophiles (see for
example. K. Mori & Y. Nakamura; J. Macromol. Sci. Chem. Al2, (2),
209, (1978)).
In a number of articles and patents, Mori and Nakamura have
described cross-linking of PVC with various types of dithiol
triazines.
There are several reasons why the above method has not been a
commercial success, despite its many attractive aspects. Since
the cross-linking in thîs case is triggered by heat, the
reactivity of the system must be so good that the cro~;s-linking
can be done without breaking down the polymer. At the same time
there are many processing techniques which require that the
cross-lin~ing is only done after the actual processing of the
material is concluded. All this means that a very difficult
balancing act is necessary to create a functional system. A
further complicating factor is that the triazines which have the
~ighest reactivity at the same time have a degrading ~ffect on
PVC. The method is therefore hardly suitable for producinq
thermostable chemical-resistant products.
Cross-linking of PVC with organic alkoxysilanes has been the
object of great inkerest in recent years. Several patent
applicati~ns describe this technique - examples that can be
mentioned are DE 3719151, JP 55151019 and N0 890543. The methods
described using alkoxysilanes have the disadvantage that the
cross-linkin~ requires the addition of water or water vapour. Two
separate processes thus become necessary to obtain the desired
product.
The object of the invention is therefore to produce a
thermostable chemical-resistant halogenous plastic, specifically
a polyvinyl chloride. To achieve greatly enhanced chemical-
resistance in the case of P~C, it is necessary to introduce a
cross-linked network into the product. To retain a
WO 93tl3161 PCI/N092/00194
32 1 ~ fi ~' 7 ~
thermostability comparable to that of a standard! PvC it is
necessary that the cross-linking reaction can be carried out ;~ -
concurrently with the working of the material without requiring
very much extra heat. -~
These and other objects of the invention are achieved by the ~
procedure described below, and the invention is characterized and `~ -
defined by the accompanying patent claims. ^
', ~.,.'.
The present invention concerns a procedure for producing a
chemical-resistant halogenous plastic. Reactive ~roups are added
to a halogenous polymer and cross-linked by reaction with a ~ r',`r
multifunctional organic com~ound under the influence of heat `~
during or after the processing. ~'.,.;' ,,",.~ !,
PVC is a preferred polymer, but the method is applicable to the
production of cross-linked products from other~ halogenous `
polymers too. The invention also concerns a chemical-resistant `~
cross-linked plastic which consists of 20-98% of copolym~r of ~`
vinyl chloride and a glycidylic monomer, 0-80% of plasticizer,
0~05-10% of a multifunctional organic cross-linker, 0.1-10% of `~
stabilizer and 0-3S of lubricant. The application of this ~Z -
plastic in oil and chemical-resistant products, especially foils,
is also covered by the invention. -~
PVC is one of the great thermoplastics and is regarded as a
"mature" product. All the same, there is a steady increase in the
consumption of PVC, and new areas of application are still being
developed. PVC is ~ainly produced by means of suspen~ion, ~-
emulsion, microsuspension or mass polymerization. The bulk of the ~;~
PVC produced is homopol~meric. The unique feature of PVC is that ~ ~-
it can be mixed with a great number of organic solvents, and this
means that products at all grades of plasticity can be
manufactured. ~
The qenerally poor thermal stability of PVC is due to defect ~`;
structures which arise in the polymer chain during
polymerization. These defect structures can be allylic and
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W093/13161 ,~j PCT/N092/00194
tertiary chlorine groups as illustrated below.
: '
Cl H Cl
C - C - C ~ normal structure
n
H H H .
H H H H ~ :
-C =C -C -C- allylic chlorine
Cl
Cl H Cl H -~
I
-C - C -C - C tertiary chlorine
H H C2Hs H
.~ .;
One advantage of these defect sites is that the chlorine groups
here are far more reactive than normal. This allows reactions
with cross-linkers which are nucleophiles. Unfortunately, thoush,
the number of possible reaction sites is far too small to achieve
sufficient cross-linking.
It is therPfore an essential part of the invention that a
halogenous polymer is used which has had extra reactive groups
added, which in reaction with suitable cross linkers can produce
a strong, homogenous network. It is an advantage if the extra
reactive groups are already added during polymerization. The
polymer can then in itself be regarded as reactive.
There are a nu~ber of relevant comonomers of vinyl chloride in
this respect, and the choice of reactive group in the monomer can
be made from, for example, epoxy ~glycidyl), carboxylic acids,
acid anhydrides, hydroxyl, amines, amides, isocyanates and
silanes. Glycidylic acrylates or methacrylates have proved
particularly favourable. This is because they are easily
copolymerized with vinyl chloride in emulsion or suspension
polymerization, and they are quickly used up so that t~ere is no
~093/13161 212 ~ ~ 7 ~` PCT/N092/00194
enrichment of them in the monomer phase. In addition, the epoxy
groups have a suitable reactivity in the conditions in which the
cross-linking has to be done. `
:: ;...;
Copolymerization of vinyl chloride and a glycidylic acrylate or ~
methacrylate (GA), e.g. glycidyl methacrylate, is as mentioned ~ ;
above an example of the way epoxy groups can be introduced into
a halogenous polymer. Of the total monomer amount, GA should make
up 0.05-lO weight %, preferably 05.-5 weight ~. The comonomer can
be added in a freely-selected way, but it is an advantage if an
even distribution of reactive groups in the polymer can be ;; `
achieved. The polymer can also be produced as a standard PVC with `;~
the above~mentioned techniques. Glycidyl acrylate and butyl ;
glycidyl acrylate are also suitable monomers. ; ;
; .. . .
In princip~e the cross-linker can be any multifunctional compound
which is coreactive with the polymer's reactive groups - for
example acid anhydrides, carboxylic acids, amines, amides, ~`.
mercaptans, thiol triazines, amidazoles. Special preferences are ` - -
phthalic anhydride, maleic anhydride, succinic anhydride, `~
succinic acid, malonic acid, oxalic acid, adipic acid, 2- ;
dibutylamino-4,6-dithiol triazine, 2,4,6-trithiol triazine and ```~
l,6-hexane diamine. ~
To increase or adapt the reactivity of the system, catalycts,~;
e.g. of the tertiary amine or Lewis acid types, can be used. The ~ -
cross-linker may also be another reactive polymer containing the --
above-mentioned groups. The type of cross-linker which will give ~;~
the desired result will depend on the total reaction system and
reaction conditions. The cross-linker may be added at an
arbitrarîly chosen point in time, also before the actual
polymerizate dries.
The cross-linking take place when the copolymer produced i5 mixed
with the cross-linker, and there is a direct reaction between
these while the product is being processed. If the cross-linker
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WO93/13161 PCT~NO92/00194
~ ~?i'~ 6
is 2 difunc,ional 2mine the rezcticns czn be illus~-2ted 25
follows:
tl3C - C - C - - Cl'2 - CH - C~'2 H2C - CH - C~!z - O C - C CIJ.3
1~,2N ( C~2 ) 6 NY2
o OH OH o
H3C - C - C - O - CH2 - CH - Clt2 - NH ( C~.2)6 - Nii - C~i2 - CH - CH2 0 - C -C - C~3
)=po~merc~ain
In this procedu-e, ,he ~isad~2~t~ge c~ ~ocr ~.e~os~a~ whe~
usins ~he 2~0Ve-~e-.~ i~nes .-~ 2- ' nzs C2~ 5~ _e o~_r-~C ~ec2~se
the sys,em is so ~ezc.ive .nz. socd results C2~. -e ac;~ie~e 2_ Z
lower working temperatu~e and without the addition of 2ctiv2tin~
metallic sa~ts. The pol~e- is thus expose~ to less hea. s~ress
and retains its thermostability.
One can study the cnemical-resistance by exposing the finishe~
pr~ducts to attacks by ~2_-ious t~pes of solvents. Fo- P~C,
cyclohexanone and tet~zhvdro~ran ~TH-) z-e good sslvents ~hich
wi-~l completely dissolve the procucts. Acetone and ciesel a~e
other relevant sol~ents which wi}l a~ack and swell PVC to a
certain extent. For products which are to be use~ in contact with
chemicals and solvents, the time aspec~ is also im~or_2n~. The
produc_ m;st retain its s~ructur2 ~nd its mecnan~cal pro~erties
during storage. T~is means that additives 2nd adàed pl s.icizers
must not be allowed t~ mi~ra~e from ~he procurt to the amDient
medium. Its has eme~ged that these pr~duct reoui-emen~s can be
me~ if cross-1inkin~ is introauced.
WO g3/13161 2 1 2 ~ ~ 7 1. PCT/~092/00194
The invention is described in more detail in ~he following
examples. Foils of varying composition are produced from both
paste PVC and S-PVC. Different types of cross-linkers were used.
The production method for the foils and methods of testing them
are descri~ed below. If not otherwise stated, quantities are
given in pph (weight parts per hundred parts of polymer).
PRODUCTION OF FOIL.
1~ Paste PVC
The paste is mixed in a Hobart mixer in accorda~ce with the
ingredients given in Tables 1-3. The paste is stroked on to
release paper immediately after mixing and gelatinized/rolled and
if necessary pressed as described in Tables 1-3.
2. S-PVC ~
The mixing is done in a small Papenmeier mixer. All solids are
mixed together from the start at "low" agitation. The plasticizer
~DOP) is added when the temperature has reached 65CC. The mixing
then continues at "high" speed until the temperature reaches
110C. The powder is then cooled down to 40C.
These mixtures (225 g) are rolled into a foil 1 mm thick on the
same day - the rolling specifications are given in Table 4. The
foils are then aged with heat treatment as described in Ta~le 4.
TESTING T~E FOILS
1. Gel in THF.
Jeton~ of foil are punched out and transferred to tetrahydrofuran
(THF). After about 24 hours the gel jeton is evaluated (gel
(Yes)/non-gel(No)/partial).
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WO~3/13161 ~ PCT/NO92/0~194
~ 8
The quantity of gel (%) is determined by a simplified method
where the jeton is weighed before and after storage in THF (24
hours). The percentage of cross-linked gel is determined by the
foxmula:
~ Gel = Weight~ f t e r/Weigh~b e f o r ~ X 100%
Weighta f t e r ~ weight of gel after drying (50C, 5 hours)
Weightb e f ~ r e ~ weight of jeton.
2. Stress relaxation
The degree of cross-linkin~ in the foils is also assessed by
. ~ .
stress relaxation tests in a dynamic spectrometer ~heometrics
RDS 7700~. The conditions are given in Tables l-2. The values
given as percentages are the ratio between the stress re`laxation
module initially and after lO0 seconds measured at 8~ constant
deformation.
3. Storage stability in diesel.
The foils are stored in diesel for seven full days. Before and
after storage in diesel the foils are analysed for tensile
strength, elongation before breakage, cold-flex temperature and
weight changes.
Maximum tensile strength and elongation before breakage are
measured with a UTS lO universal ~esting machine at a stretching
speed of 50/min. The specimens conform to the specifications of
IS0 R 527 (Test Type 2.).
Weight change after storage in diesel was calculated on the basis
of the weight of the foil before and after storage. Before the
foil was weighed after storage, it was dried with absorbent paper
. : .
W093/13161 PCT/N092/00194
!
9212 ~ 3 r7 ~;
and only weighed 24 hours later.
Cold-flex was done in accordance with ISo 458, Parts l and 2.
'.' '' ',
Test l
Six mixtures of paste PVC with different compositions were made
as shown in Table l. One of the tests (Al) was done with PVC
homopolymer, while in the others (A2-6) a copolymer of PVC and
glycidyl methacrylate (GMA) was used. The percentage of GMA is
based on the added quantity of VCM. Equal amounts of plasticizer,
stabilizer and epoxidized soya oil were added to th~ six
mixtures. Different quantities of cross-linker were added to
three of the mixtures. The samples Al-4 were rolled for 3 mins.
at 175~C and then pressed at the same temperature for 3ll mins.
Testing of these foils showed that the foils without added cross-
linker tAl-A3) were fully dissolved in tetrahydrofuran. The foil
with least cross-linker (A-4) and 1% of GMA was partially
dissolved. Samples A5-6 both had 2% of GMA but different
. . :, .
quantities of cross-linker, and were treated in the same`way with ~`
gelatinization and pressing. It can be seen from the test results
~hat these were resistant in tetrahydrofuran. Cross-linking was ~`
formed. However, the double quantity of cross-linker in A6 had
little extra effect compared with A5. 1` ``
~; .
The introduction of reactive groups into the PVC chains leads to
a slight reduction in thermostability. The use of different
cross-linkers also leads to great differences, but t~e
homopolymer will always b~ rather better than the reactive
samples. It is nevertheless possible to optimize the recipes with
respect to thermostability, for example by the choi~e of cross~
linker. The product is manufactured in process conditions which
do not require extra heat, so the thermostability of the product
is maintained.
' ': :`~,
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WO 93/13161 PCI`/NO92/00194
TABLE 1. Test with Zisnet DB as cross-linker ;~
. .
Recipe A-l A-2 A-3 A-4 A-5 A-6
Homopolymer lOo
Copolymer (1%) 100 100
Copolymer (2%) 100 100 100
DINP1 60 60 60 60 60 60 ~;
Lankromark LZ6162 2 2 2 2 2 2
ESo3 3 .3 3 3 3 3 ~.. .
Zisnet DB4 1.2 2.5 5.0 ~::
Gel time (mins.) 3 3
Gel temp. ~C) 175 170
Rolling time (mins.)3 3 3 3
Rolling temp. (C) 175 17~ 175 175 ~ .
Pressing time (mins.) 3+1 3l1 3+1 3+1 3 + 1 .-~:
3~1
Pressing temp. (~C)175 175 175 175 175 17
Gel in THF (Y/N) N N ~partial Y
Y
Gel in THF (%) 0 0 0 - 54~5 56.0
Rheometrics (96) 37.2 34.1 25.7 37.0 70.0 64.3
.
1) DINP = di-isononyl phthalate ~ -
2) Lankromark LZ616 = Ca/Zn stabilizer from Lankro.
3) ES0 - Epoxidized soya oil
4) 2isnet DB = 2-dibutylamino-4,6-dithiol triazine from Sankyo ..
Kasei.
~j, . .
Test 2
Seven different mixtures were produced from paste PVC. These are -`;~..
shown in Table 2~ Homopolymer was used in Test B-1, while in the ;~
WO93/13161 PCT/NO92/00194
2;12~7~ -
1 1
others a copolymer of PVC and 2% of glycidyl met~acrylate was
used. The same amount of additives was used in all mixtures. ~he
quantity of cross-linker was varied. All samples except B-6 were
gelatinized for 7 minutes, while the gelatinizing temperature was
varied from 170 to 190C. The results show that the two samples
Bl-2 without cross-linker were both dissolved in tetrahydrofuran.
No major effect can be observe from doubling the amount of cross-
linker (see B-3 and B-6). The gelatinizing temperature has a
positive effect on the result, as gelatinization at 190C
produces better cross-linkin~ than treatment at 170C. A longer
gelatinizing time also affects the result, as can be seen by
comparing the mixtures B-6 and B-7.
,,; ,.,~.'"~,
TABLE 2. Test with Zisnet F as cross-linker . ~;
Recipe B-1 B-2 B-3 B4 B 5 B-6 B-7
Homopolymer 1 00
Copolymer (29~) 100 100 100 100 100 ~ 100 ,.,.,,~!~,.
DINP 60 60 60 60 60 60 60 ` `.. '~;`
Lankromark L~616 2 2 2 2 2 2 2
ESO 3 3 3 3 3 3 3 ~A~',''",
Zisnet F~ 2.8 2.8 2.8 æ8
__~ ~____~__~ __ ~_ _ __ _ ~ ~ ____~_ _ _ ___ ,
Gel time (mins) 7 7 7 7 7 3 7 :.;
Gel temp.~C) 190 190 190 170 180 190 190
Gel inTHF (YIN) N N Y Y Y Y Y
Gel inTHF (%) 0 0 27.2 28.0 30.9 28.3 33.8
Rheometrics (%) - 38.4 49.9 46.7 50.1 51.5 54.5
t1 50C/8%)
:, - .' `
1) Zisnet F = 2,4,~trithiol triazine from Sankyo Kasei. . ` ~
~, ~ ....
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WO93/13161 PCT/NO92/0~194
~ 6~ 12 ~
Test 3 ~-
Three mixtures were made ~C1-3) with a copolymer of PVC and 2% of `
glycidyl methacrylate. The mixtures C4-6 had a content of 3% of
glycidyl methacrylate. The same quantities of additives were used
in all mixtures while the quantity of cross-linker (phthalic ~-
anhydride) was varied from 1.7 to 4.4. A gelatinizing time of 15
minutes at l90~C was used for all samples. The results show that
only the samples with the highest content of GMA produced good
cross-linking, and that the best result was achieved with t~e
highest content of cross-linker. ~`
,
TABLE 3. Test with phthalic anhydride as cross-linker
Recipe C-1 C-2 C-3 C4 C-5 C-6 ;~ ~
, , ~ ~,
Copolymer (2%) 100 100 100
Co~mer (39~) 100 tO0 100
DINP 60 60 60 60 60 60
Lankromark ~616 2 2 2 2 2 2 ~
ESO 3 3 3 3 3 3
Phthalic anhydride 1.7 2.3 2.9 æ6 3.5 4.4
Gel time (mins.~ 15 t5 1~ ~5 15 15 ~ .-
Gel temp. tC) 190 190 190 190 190 190 . ~
.
Gel inTHF (YIN) ~ panial partial partial Y Y Y
Rhsometrics t%) 43.1 43.9 42.9 45.B 48.1 49.3 . :~
(1~0C/8%) . ~
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W O 93/13161 PC~r/N 092/00194
2 1 ~ 6 ~ 7 ~
Test 4 '
Five mixtures were made from S-PVC with 1% of glycidyl
methacrylate. All mixtures had the same quantity of additives,
while the quantity of cross-linker varied~ The mixtures were
rolled for five minutes at 160C and three of the samples were
additionally heat-treated for 24 hours at 120C. The results show
that a higher degree of cross-linking was achieved in the samples
D-3 and D-S, which contained different quantities of cross-
linker, but which were both heat-treated. It is also notable that
it is possible to carry out rolling of the product without any
great degree of cross-linking arising. ThiC means that cross-
linking can be done on the finished, formed product.
: ~ .
TABLE 4. S-PVC cross-linked with Zisnet F ~ .
Reci,oe ~ D-1 D-2 D-3 D4 D-5
Copo~rner (1%) 100 100 100 100 100
DOP1 50 50 50 50 50
LF36552 5 5 5 5 5
AC31 6A3 0.2 0.2 0.2 0.2 0.2
Zisnet F 1 1 2 2 ~"
. .
Rollingtime ~mins.) ~ 5 5 5 5
~olling temp. (~C) 160 160 160 160 160
Heat treatment
time (hours) 24 24 24
temp. (C) 120 - 120 - 120 ~"
Gel in THF (YIN) N N Y partial Y ` `~
Gel inTHF (%) 0 0 77 - 76
. ;~
1) DOP = dioctyl phthalate ` `
2) LF3655 = Pb stabilizer from Akzo
3) AC316A = polyethylene wax from Allied Chemical Corp.
~ '
WO93/13161 PCT/NO92/0~194
~ arl~) 14
Test 5
Five different mixtures, El-5, were made, one with PVC
homopolymer and four mixtures of PVC and 2 and 3% of glycidyl
methacrylate respectively and with different cross-linkers (see
Table 5). Specimens of the foils were tested before and after
seven days' storage in diesel. The results show that the tensile
strength is more or less unchanged in all samples, as expected at
room temperature. Measurement of elongation before breakage shows
that the samples with m~st gel (good cross-linking) r-tain their
properties, while those without and with little gel are reduced ;
in elongation before breakage. The cold-flex temperature is an
expression of brittleness. The tabie shows that Sample E-1, which
is not cross-linked, has been attacked by the solvent and has -
become brittler. The other samples have retained their
flexibility. A weight reduction in the samples after storage in
diesel may for example be due to loss of plastici~er. Samples E-4
and E-5, which have a high degree of cross-linking, exhibit no -~
weight changes after storage in diesel.
.
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WO 93~13161 212 ~ ~ 7 ~ PCI`/NO92/00194 ` ~
~:
TABLE 5. Test of cross-linked toil ~etore and atter storage in diesel
Recipe E-1 E-2 E-3 E4 E-5 ~ ~:
Homopo~mer 100 ~ ~.
Copo~mer (2%) 100 100 '
Copolymer (3%) 100 100 ~ ~:
, ~ '~` '
DINP 60 60 60 60 60
Lankromark LZ616 2 2 2 2 2 ~ - ;
ESO
Phthalic anhydride 4 4 4
Zisne~ DB 5 ~ ~ r
Gel time (mins.) 10 10 10 3 3
Gel temp. (oCj 190 190 190 180~ 180
Tensile strength ~ `
before (mPa) 17.2 17.8 1~.1 15.1 .12.0
after (Mpa) 20.3 18.8 17.1 17.1 12.7
Elongation ` -
before (%) 356 350 2g5 232 ~56 ,~alter (%) 317 313 ~81 236 154
Cold-flex temp.
before (C) -34.0 -32.0 -30.4 -31.0 -29.7
atter (C) -24.1 -34.~ -36.3 ~1.0 ~9.7
Weight ehange
,reduction (%) 10.0 4.7 3.1 0.08
increase (%) 0.2
Gel in THF (Y/N) N Y(-) Y Y Y
Gel inTHF (%) 0 23 ` 35 53 53
1) Foils with~Zisnet DB were gelatinized at a lowertemperature and for shorter periods to avoid burning
the foils. ~Good results were still achieved. - ~;
`` .:
WO93/13161 ~-3 ~ PCT/NO92/00194
16
As shown in the examples, with this method one can achieve cross-
linked products with good resistance to solvents, and production ^
takes place in conditions which do not require extra heat. The
thermostability of the product is therefore maintained.
In selecting process conditions/chemicals one can customize the
process and one can choose to carry out the cross-linking either
during or after working the material. The type of cross-linker
chosen will be crucial for the degree of cross-linking in the
product.
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