Cross-linkable polymer composition containing a carboxylic acid precursor as a catalyst

A cross-linkable polymer composition containing a cross-linkable polymer having at least one hydrolysable silane group and at least one lactone or anhydride silanol condensation catalyst for example, lactide and 2-dodecen-1-yl succinic anhydride. The catalyst is not conducive to causing premature cross-linking. The composition provides a cross-linked polymer having good anti-scorch properties. Compositions containing lactones as the silanol condensation catalyst also provide cross-linked polymers having improved adhesion properties.

FIELD OF THE INVENTION 
This invention relates to a cross-linkable polymer composition comprising a 
cross-linkable polymer having hydrolysable silane groups and a silanol 
condensation catalyst, processes for cross-linking said polymer, 
cross-linked polymers produced thereby and substrates coated with said 
cross-linked polymers. 
BACKGROUND TO THE INVENTION 
Polyolefins containing silane groups on the polymer backbone are well 
known, for example, U.S. Pat. No. 4,689,369, issued Aug. 25, 1987, to 
Mitsubishi Petrochemical Co. Ltd. Such silane cross-linked polymer 
products are of industrial and commercial value in being extensively used 
in various fields, such as electric power cables, pipes, tubes, films, 
sheets, hollow moldings and foamed moldings. 
These polymers crosslink upon exposure to moisture in the presence of 
silanol condensation catalysts. Desired levels of crosslinking, as 
measured by % Gel (ASTM D2765) typically have % Gel &gt;50 w/w %, preferably 
&gt;65% w/w. Typical silanol condensation catalysts known in the prior art 
include organometallic basic compounds, particularly solids such as 
oligomeric dialkyltin maleate and liquids such as dibutyltin dilaurate; 
and acidic compounds such as carboxylic acids. 
However, in processing a mixture of silane condensation catalyst and the 
ethylene copolymer obtained by radical polymerization of ethylene and 
unsaturated silane compounds, premature state condensation reaction may 
occur, for example, at the initial stage in an extruder during extrusion 
processing and unevenness tends to occur on the surface of an extrudate. 
This defect is termed "scorching" and deteriorates the commercial value of 
the product and improvement thereof is highly sought. The premature 
cross-linking scorch problem is a widely recognized one of these moisture 
cross-linkable compositions due to premature cross-linking as witnessed by 
the number of patents claiming to reduce it. One way to minimize "scorch" 
is to use retarders as is described in, for example EP 0,193,317, which 
scavenge water and minimize the chances of premature cross-linking during 
processing. EP Application 0,401,540 to Union Carbide Chemicals & Plastics 
Company, Inc. published Dec. 12, 1990, describes a process of minimizing 
scorch by mixing in the processing zone at least one hydrolysable silane 
moiety, a dihydrocarbyltin oxide and a carboxylic acid or species capable 
of forming a carboxylic acid when subjected to heat or moisture. 
International Patent Application WO 91/09075 to Neste Oy, published Jun. 
27, 1991, describes a composition consisting of silane polymer and a 
silanol condensation catalyst consisting of an acid anhydride in order to 
minimize premature cross-linking. 
However, industry is constantly searching for compositions which minimize 
premature cross-linking and provide improved properties to the finished 
article. 
Polymeric coatings are often applied to metallic substrates, such as the 
surface of steel storage tanks to minimize oxidation. It is generally 
further desired to cross-link the lining to extend its lifetime to reduce 
stress crack failure and increase the time to embrittlement. One process 
used to line metallic tanks is rotomolding whereby the tank containing 
powdered polymer is rotated around a variety of axes in a heated zone to 
melt the powder and line the metal tank. It is desirable that the lining 
maintain good adhesion to the metal. If "disbonding" occurs, that is, the 
cross-linked polymer plastic separates from the metal and is no longer 
held in intimate contact, then air or water may permeate through the 
polymer and increase and fill the "gap" between substrate and polymer 
lining to, thus, increase the chances of corrosion and reduce the 
effectiveness of the lining. For cross-linked linings, which are 
susceptible to "scorch" during processing, it is desirable that there be 
no gels which could act as "stress raisors" leading to stress cracking. 
SUMMARY OF THE INVENTION 
Surprisingly, I have discovered a composition which does not undergo 
unwanted premature cross-linking, but which also possesses good adhesion 
to a substrate. 
It is an object of the present invention to provide a cross-linkable silane 
polymer composition having improved premature cross-linking properties. 
It is a further object of the invention to provide a cross-linked silane 
polymer composition having improved adhesion properties. 
It is a yet further object of the invention to provide a process of 
manufacturing a cross-linked silane polymer composition having improved 
properties. 
Accordingly, the invention provides in its broadest aspect a cross-linkable 
polymer composition containing a cross-linkable polymer having at least 
one hydrolysable silane group and at least one silanol condensation 
catalyst wherein said silanol condensation catalyst is a compound having a 
lactone moiety or an anhydride moiety. 
The term "polymer" in this specification and claims includes copolymers. By 
the term "lactone moiety" is meant a compound having at least one lactone 
group. By the term "anhydride moiety" is meant a compound having at least 
one anhydride group. Although in this specification and claims the lactone 
or anhydride moiety containing compound is referred to as the silanol 
condensation catalyst it would be well recognized that these compounds, in 
fact, are precursors to the actual carboxylic acid catalytic agents 
produced therefrom when desired by hydrolysis of the lactone or anhydride 
in situ in the composition. 
Preferably, the lactone is part of a five (gamma-) or six-(delta) membered 
cyclic group constituting a monolactone or, more preferably, a dilactone 
six-membered ring. Most preferred catalyst compounds of use in the 
practice of the invention are dilactones of the general 
1,4-dioxane-2,5-dione formula: 
##STR1## 
wherein R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are selected from hydrogen 
and C.sub.1 -C.sub.4 alkyl groups, particularly CH.sub.3 groups. Specific 
compounds of value in the invention are R.sup.1 .dbd.R.sup.3 .dbd.H and 
R.sup.2 .dbd.R.sup.4 .dbd.CH.sub.3 (the lactide 
3,6-dimethyl-1,4-dioxane-2,5-dione) and R.sup.1 .dbd.R.sup.2 .dbd.R.sup.3 
.dbd.R.sup.4 .dbd.H (the glycolide 1,4-dioxane-2,5-dione). 
The lactone catalyst may further comprise at least one hydroxyl group such 
as a glyconolactone, for example, delta-gluconolactone and the hydroxyl 
enol lactone-ascorbic acid. 
The lactone and anhydride moiety catalysts of use in the invention have 
found particular use in the coating of metal electrical conductor wire and 
metal storage vessels, such as steel tanks made by known rotomolding 
processes to form a plastic lining thereon. 
Surprisingly, I have found that rotomolding tank linings with silane 
polymer containing the anhydride and/or lactone moiety compounds as 
silanol condensation catalysts yields a lining with improved properties 
over the prior art catalysts. The linings containing these catalysts are 
smooth and gel free. Linings containing the prior art catalysts were very 
rough due to "scorch" and the production of gels. 
Surprisingly, I have also found that rotomolding tank linings with silane 
polymer containing the lactone moiety compounds as silanol condensation 
catalysts yields a lining with improved properties over the prior art 
catalysts. The linings containing these lactone catalysts remain adhered 
to a steel tank in a manner favourably comparable to silane polymer 
without catalyst, while linings containing the prior art catalysts 
"disbonded" from the metal in a matter of minutes after rotomolding. 
While not being bound by theory, I believe that the lactone-type catalysts 
of use in this invention not only cause less "scorch" than the prior art 
catalysts but also less viscosity hardening as a precursor to "scorch". 
This allows the silane polymer to "wet out" the metal substrate in a 
manner most resembling the uncatalyzed polymer. 
The use of these carboxylic acid precursor catalysts is particularly useful 
when the tanks are intended for storage of water, particularly hot water, 
which will ensure crosslinking. 
Another advantage of the lactone moiety containing catalysts is that they 
are generally derived from naturally occurring substances and produce 
acids which are non-toxic and in some cases are part of the human 
metabolic cycle. Also, unlike most acid anhydrides, these catalysts do not 
have sharp, disagreeable odors. 
Thus, the invention provides in a further aspect, a process for producing a 
cross-linked polymer said process comprising treating a composition as 
hereinabove defined under cross-linking conditions in a cross-linking zone 
to produce said cross-linked polymer, which process is enhanced by the 
application of an effective amount of heat and/or moisture. 
The processes of the invention may be carried out using well-known prior 
art methods for the coating of wire and rotomolding of containers. The 
processing zone can be a conventional extruder, e.g. a single screw type. 
A typical extruder has a hopper at its upstream end and a die at its 
downstream end. The hopper feeds into a barrel, which contains a screw. At 
the downstream end between the end of the screw and the die, is a screen 
pack and a breaker plate. The screw portion of the extruder is considered 
to be divided up into three sections, the feed section, the compression 
section, and the metering section, and two zones, the back heat zone and 
the front heat zone, the sections and zones running from upstream to 
downstream. If it has more than one barrel, the barrels are connected in 
series. The length to diameter ratio of each barrel is in the range of 
about 16:1 to about 30:1. 
The processing zone can also be a conventional injection molding apparatus 
or a rotomolding apparatus. 
The conditions in the cross-linking zone are such that the lactone moiety 
forms a free carboxylic acid. As noted, this is accomplished through the 
application of heat and/or moisture. The temperature in the cross-linking 
zone will generally be in the range of about 20.degree. C. to about 
150.degree. C. and is preferably in the range of about 50.degree. C. to 
about 100.degree. C. With respect to those compounds which need moisture 
to form the carboxylic acid, the formation is generally facilitated by the 
presence of heat in the ranges mentioned above. However, care must be 
taken that the conditions are such that the lactone moiety compound is not 
decomposed or otherwise destroyed. 
The residence time of the mixture in the processing zone is, for example, 
of sufficient length to complete all or part of the extrusion, injection 
molding, or roto molding. This time is in the range of about 20 to about 
2000 seconds and is preferably about 60 to about 1000 seconds. 
The cross-linking zone is usually a water bath through which the extruded 
molded resin, i.e. the processed resin, is passed. The residence time in 
this zone can be in the range of about 0.01 to about 240 hours and is 
preferably about 8 to about 72 hours. As an alternative to the water bath, 
the zone can be humidified at a relative humidity of at least about 50 
percent. 
Conventional additives can be added to the mixture introduced into the 
processing zone. The amount of additive is usually in the range of about 
0.01% w/w to about 50% w/w based on the weight of the resin. Useful 
additives are antioxidants, ultraviolet absorbers, antistatic agents, 
pigments, dyes, fillers, slip agents, fire retardants, plasticizers, 
processing aids, lubricants, stabilizers, and smoke inhibitors. Blends of 
the hydrolyzable polymer and other polymers can be prepared in the 
processing zone provided that the resins to be blended with the 
hydrolyzable copolymer will not cross-link. Examples of these resins are 
low density polyethylene, high density polyethylene, polypropylene, linear 
low density polyethylene, and very low density polyethylene (equal to or 
less than 0.915 grams per cubic centimeter). 
In a yet further aspect, the invention provides a substrate such as an 
electrical conductor wire or container having a surface coated with a 
cross-linked polymer according to the invention. 
Preferred cross-linkable polymers of use in the invention are previously 
known and described and prepared for example, in aforesaid USP 
4689369--which is incorporated herein by reference. Thus, the preferred 
cross-linkable polymers having a hydrolysable silane group of use in the 
invention are silane grafted homopolymers or copolymers or copolymers of 
olefins and a silane. Preferred compositions comprise 100 parts by weight 
of a copolymer prepared by radically polymerizing a polymerizable 
monomeric mixture consisting essentially of ethylene and at least one 
ethylenically unsaturated silane compound selected from the group 
consisting of vinyltrimethoxysilane, vinyltriethoxysilane and 
methacryloxypropyltrimethoxysilane under a pressure ranging from 1000 to 
4000 kg/cm.sup.2, and containing said silane compound in an amount of from 
0.5 to 2 wt. %; from 0,001 to 10 parts by weight of said silanol 
condensation catalyst; and most preferably when said ethylenically 
unsaturated silane compound is vinyltrimethoxysilane. 
The cross-linkable polymers of the present invention may, optionally, but 
not preferably further contain compounds which have been conventionally 
used as a catalyst for accelerating dehydration condensation between 
silanol groups. 
Examples of such silanol condensation catalysts are carboxylic acid salts 
of metal such as tin, zinc, iron, lead and cobalt, organic bases, 
inorganic acids, and organic acids. Representative examples of these 
silanol condensation catalysts are (1) carboxylic acids of metals such as 
dibutyltin dilaurate, dibutyltin diacetate, dibutyltin dioctoate, stannous 
acetate, stannous caprylate; (2) organic bases such as ethylamine, 
dibutylamine, hexylamine and pyridine; (3) inorganic acids such as 
sulfuric acid and hydrochloric acid; and (4) organic acids such as 
toluenesulfonic acid, acetic acid, stearic acid and maleic acid. 
The silanol condensation lactone or anhydride moiety catalyst is used in an 
amount of 0,001 to 10 parts, preferably 0.01 to 5 parts, and more 
preferably 0.1 to 3 parts, by weight per 100 parts by weight of the 
silane-crosslinkable ethylene copolymer. If the amount of the silanol 
condensation catalyst is less than 0.001 part by weight per 100 parts by 
weight of ethylene copolymer, the cross-linking reaction does not proceed 
sufficiently. If, on the other hand, the amount of the silanol 
condensation catalyst is more than 10 parts by weight per 100 parts by 
weight of copolymer, it may compromise physical properties. 
It will be appreciated that the effective amount of lactone or anhydride 
catalyst depends on its molecular weight of the lactone, more precisely 
the number of lactone or anhydride groups per mole. Thus, a smaller amount 
is required of a catalyst having many lactone or anhydride groups and a 
low molecular weight, than of a catalyst having but few lactone or 
anhydride groups and a high molecular weight. 
The ingredients of the invention as hereinabove defined may be prepared 
into the desired composition in a mixer conducted by conventional methods. 
The processed product is then silane-cross-linked with water for use, for 
example, as electric cable insulation or rotomold lining. 
The inventive lactone or anhydride catalyst is preferably added to the 
cross-linkable polymer in the form of a master batch, i.e. mixed with a 
polymer, such as polyethylene. The master-batch contains a minor amount of 
the lactone or anhydride catalyst, generally about 1-25% by weight, 
preferably about 1-10% by weight. 
The lactone or anhydride catalysts according to the invention are 
especially advantageous, since the catalysts may be added directly to the 
cross-linkable polymer, there being no need to first produce a master 
batch. 
Fillers such as silicates, e.g. kaolin, talc, montmorillonite, zeolite, 
mica, silica, calcium silicate, asbestos, powdered glass, glass fibre, 
calcium carbonate, gypsum, magnesiumcarbonate, magnesiumhydroxide, carbon 
black and titanium oxide may be present in the composition of the 
invention without detracting from the efficacy thereof. The content of the 
inorganic filler may be up to 60% by weight, as based on the sum of the 
weights of the filler and the silane-containing polymer.

DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION 
In order that the invention may be better understood, preferred embodiments 
will now be described by way of example only. 
Example 1 
The following formulations were prepared on a Brabender Sigma Blade Mixer 
with 500 g capacity bowl by blending at 150.degree. C. @ 20 rpm for 10 
minutes. A 4 MI EVS copolymer was used which contained suitable 
antioxidants. The EVS Copolymer had approximately 2 wt % 
vinyltrimethoxysilane content. The EVS Copolymer is a commercially 
produced under high pressure, free radical copolymer of ethylene and vinyl 
trimethoxysilane in pellet form, maintained dry in water impermeables 
packaging and sold under the trademark AQUA-LINK.RTM. (AT PLASTICS INC., 
BRAMPTON, ONTARIO) Canada. 
Lactide is 3,6-dimethyl-1,4-dioxane-2,5-dione, and glycolide is 
1,4-dioxane-2,5 dione. 
______________________________________ 
Sample Formulation 
______________________________________ 
1A 100% EVS Polymer 
1B 95% EVS Polymer 
5% Catalyst Masterbatch (1% 
Dibutyltindilaurate in LDPE) 
1C 99% EVS Polymer 
1% Succinic Anhydride 
1D 99% EVS Polymer 
1% 2-Dodeceny-1ylsuccinic 
anhydride 
1E 99% EVS Polymer 
1% Lactide 
1F 99% EVS Polymer 
1% Glycolide 
______________________________________ 
The compounds were pressed into 15 cm.times.15 cm.times.0.3 cm plaques 
using a picture frame mold in a heated press at 150.degree. C. 5 tons 
pressure, for 2 minutes. 
Example 2 
The plaques from Example 1 were suspended in a humidity chamber at 
70.degree. C. and 95% R.H. and the % Gel formation measured over time 
using ASTM D2765. The results are given in Table 1. 
TABLE 1 
______________________________________ 
% Gel % Gel % Gel % Gel % Gel % Gel 
Days in Sauna 
1A 1B 1C 1D 1E 1F 
______________________________________ 
0 3.3% 15.2% 10.5% 15.5% 1.6% 2.4% 
1 1.2% 69.2% 68.4% 67.9% 1.2% 1.1% 
7 1.8% 76.9% 72.6% 79.3% 66.8% 77.0% 
14 19.0% 81.2% 79.1% 85.3% 74.5% 69.9% 
______________________________________ 
The lactones and anhydrides effectively crosslink the silane polymer but 
the lactones do so at a slower rate than the prior art catalysts. 
Example 3 
The formulations shown in Table 2 were rotomolded in new, unused 4 liter 
paint cans by first tumble blending catalyst with the 4 MI EVS polymer 
used in Example 1 ground to less than 35 mesh, as is typical for 
rotomolding grades of polymer resins. Most catalysts consisted either of 
powdered (&lt;35 mesh) 4 MI LDPE mixed with 20 wt % solid anhydride/lactone 
crystals/flakes or, in the case of the liquid anhydride, 20 wt % of liquid 
dispersed and coated onto the 4 MI LDPE powder. The dibutyltindilaurate 
was compounded into 4 MI LDPE at 1 wt % and then ground to &lt;35 mesh. The 
EVS Polymer/Catalyst mixture in the paint can was loaded onto a chuck 
attached to an electric motor and rotomolded around one axis parallel to 
the sides of the can in an oven at 10 rpm, 265.degree. C. for 10 minutes. 
The results of this rotomolding are given in Table 2. 
TABLE 2 
______________________________________ 
Overall Molding 
Catalyst Surface 
ID Sample Level Finish Comments 
______________________________________ 
2A 100% EVS Polymer 
0% smooth good 
adhesion 
2B 95% EVS Polymer 
500 ppm rough, disbonded 
5% LDPE containing 
DBTDL many gels 
dibutyl- 
tindilaurate 
2C 95% EVS Polymer 
1 wt % Succinic 
smooth disbonded, 
5% LDPE containing 
Anhydride sharp odor 
succinic 
anhydride 
2D 95% EVS Polymer 
1 wt % 2-dodecen- 
smooth disbonded, 
5% LDPE containing 
1ylsuccinic oily 
2-dodecen- anhydride bloom 
1ylsuccinic 
anhydride 
2E 95% EVS Polymer 
1 wt % Benzoic 
smooth disbonded, 
5% LDPE containing 
anhydride strong 
benzoic odor 
anhydride 
2F 95% EVS Polymer 
1 wt % stearic 
smooth disbonded, 
5% LDPE containing 
anhydride waxy 
stearic bloom 
anhydride 
2G 95% EVS Polymer 
1 wt % lactide 
smooth good 
5% LDPE containing adhesion 
lactide 
2H 95% EVS Polymer 
1 wt % glycolide 
smooth good 
5% LDPE containing adhesion 
glycolide 
______________________________________ 
In this table "disbonded" means that the polymer lining the sides of the 
can separated from the metal surface so that an air space was evident 
within minutes to several hours after the molding had cooled to room 
temperature. Good adhesion means that the lining and metal remained in 
intimate contact indefinitely. 
Example 4 
The rotomolded paint cans with polymeric linings were filled with water and 
stored in a 70.degree. C. oven to simulate, for example, a hot water 
heater tank, and the % Gels measured over time. The results are given in 
Table 3. 
TABLE 3 
______________________________________ 
Paint Can Full of H.sub.2 O 
Sample Days in 70.degree. C. Oven 
% Gel 
______________________________________ 
2A 7 Days 20% 
14 days 26% 
2B 7 Days 81.2% 
2C 7 Days 79.2% 
2D 7 Days 76.5% 
2E 7 Days 81.7% 
2F 7 Days 79.2% 
2G 7 Days 67% 
14 days 70.8% 
2H 7 days 65% 
14 days 67.3% 
______________________________________ 
The rotomolded linings containing catalyst are crosslinked. 
Example 5 
15 gallon tanks were rotomolded on a commercial rotomolder. The tanks were 
cylinders with rounded ends approximately 1 foot in diameter and 4 feet in 
length. The tanks were loaded with 2500 g of powdered (&lt;35 mesh) 4 MI EVS 
Copolymer used in Example 3 and either 125 g or 65 g or the powdered (&lt;35 
mesh) catalysts used in Example 3. The tanks were rotated around 3 axes at 
450.degree. F. for 12 minutes followed by 5 minutes of air cooling and 1 
minute of water spray cooling. After cooling the tanks were cut open 
around the middle and the lining examined. Some of the lining was removed 
from the tank and stored overnight in 190.degree. F. water and the % Gel 
measured according to ASTM D2765. The results are given in Table 4. 
TABLE 4 
______________________________________ 
Overall Molding 
Catalyst Surface % 
ID Sample Level Finish Comments 
Gel 
______________________________________ 
4A 100% EVS 0 smooth good 0% 
Polymer adhesion 
4B 95% EVS 500 ppm rough disbonded 
74.5% 
Polymer DBTDL 
5% LDPE 
containing 
dibutyl- 
tindilaurate 
4C 95% EVS 0.375 wt % 
smooth disbonded, 
70% 
Polymer stearic waxy bloom 
5% LDPE anhydride 
containing 
stearic 
anhydride 
4D 95% EVS 1 wt % smooth disbonded, 
65% 
Polymer benzoic strong 
5% LDPE anhydride odor 
containing 
benzoic 
anhydride 
4E 95% EVS 0.5 wt % smooth disbonded, 
62% 
Polymer benzoic strong 
5% LDPE anhydride odor 
containing 
benzoic 
anhydride 
4F 95% EVS 1 wt % smooth good 50% 
Polymer lactide adhesion 
5% LDPE 
containing 
lactide 
______________________________________ 
Rotomolded linings 4A and 4F exhibited excellent adhesion to the metal even 
after cutting the tanks open no disbonding occurred along the cut edge. 
The other linings all started to disbond from the metal within minutes of 
cooling and before cutting the tanks open. Lining 4B was very rough with 
many large gels. 
Example 6 
The following formulations were prepared on a Brabender Sigma Blade Mixer 
with a 500 g capacity bowl by blending at 130.degree. C. @ 20 rpm for 5 
minutes. The 4 MI EVS copolymer described in Example 1 was used. 
______________________________________ 
Sample Formulation 
______________________________________ 
6A 100% EVS Polymer 
6B 99% EVS Polymer 
1% Ascorbic Acid 
6C 99% EVS Polymer 
1% O-gluconolactone 
6D 99% EVS Polymer 
1% Lactide 
______________________________________ 
The compounds were pressed into 15 cm.times.15 cm.times.0.3 cm plaques 
using a picture frame mold in a heated press at 150.degree. C. 5 tons 
pressure, for 2 minutes. 
Example 7 
The plaques from Example 6 were suspended in a humidity chamber at 
70.degree. C. and 95% R.H. and the % Gel formation measured over time 
using ASTM D2756. The results are given in Table 5. 
TABLE 5 
______________________________________ 
% Gel % Gel % Gel % Gel 
Days in Sauna 
6A 6B 6C 6D 
______________________________________ 
18 days 1% 48% 4% 73% 
45 days 4% 67% 8% 80% 
______________________________________ 
Example 8 
The formulations shown below in Table 6 were rotomolded in new, unused 4 
liter paint cans by first tumble blending catalsyt with the 4 MI EVS 
polymer used in Example 1 ground to less than 35 mesh, s is typical for 
rotomolding grades of polymer resins. The catalyst powders were mixed 
directly with the EVS polymer powder. The EVS Polymer/Catalyst mixture in 
the paint can was loaded onto a chuck attached to an electric motor and 
rotomolded around one axis parallel to the sides of the can in an oven at 
10 rpm, 265.degree. C. for 10 minutes. The results of this rotomolding are 
given in Table 6. 
TABLE 6 
______________________________________ 
Surface 
ID Sample Finish Comments 
______________________________________ 
8A 99% EVS Polymer very rough 
disbonded 
1% anhydrous 
citric acid 
8B 99% EVS Polymer smooth disbonded 
1% cyclohexyl 
dicarboxylic 
anhydride 
8C 99% EVS Polymer smooth disbonded, 
1% succinic strong odor 
anhydride 
8D 99% EVS Polymer smooth good adhesion 
1% D,L-lactide 
8E 99% EVS Polymer brown, decomposed, 
1% ascorbic acid 
cellular good adhesion 
8F 99% EVS Polymer brown, decomposed, 
1% O-gluconolactone 
cellular good adhesion 
8G 99% EVS Polymer smooth disbonded 
1% hydrophthalic 
anhydride 
lactide 
8H 100% EVS Polymer 
smooth good adhesion 
______________________________________ 
In this table "disbonded" means that the polymer lining the sides of the 
can separated from the metal surface so that an air space was evident 
within minutes to several hours after the molding had cooled to room 
temperature. Good adhesion means that the lining and metal remained in 
intimate contact indefinitely. The cellular nature of samples 8E and 8F 
were due to gas evolution due to catalyst decomposition. 
Example 9 
The rotomolded paint cans with polymeric linings were filled with water and 
stored in a 70.degree. C. oven to simulate, for example, a hot water tank 
heater tank, and the % Gels measured over time. The results are given in 
Table 7. 
TABLE 7 
______________________________________ 
Paint Can Full of H.sub.2 O 
Sample Days in 70.degree. C. Oven 
% Gel 
______________________________________ 
8B 7 Days 75% 
8C 7 Days 70% 
8D 7 Days 69% 
8E 7 Days 67% 
8F 7 Days 70% 
8G 7 Days 74% 
8H 7 days 30% 
______________________________________ 
The rotomolded linings containing catalyst are crosslinked. 
While the invention has been described in detail and with reference to 
specific embodiments thereof, it will be apparent to one skilled in the 
art that various changes and modifications can be made therein without 
departing from the spirit and scope thereof.