Norbornene derivatives of phenols

Novel phenols substituted by at least one 5-norbornen-2-ylmethoxymethyl group and optionally, by methyl or t-butyl groups are used as nondiscoloring antiozonants and antioxidants in chloroprene polymers.

BACKGROUND OF THE INVENTION 
The present invention concerns novel norbornene derivatives of phenols and 
their use in polymeric compositions having improved ozone resistance. 
Elastomeric vulcanizates are known to develop surface cracks when exposed 
to atmospheric influences and certain mechanical conditions. Such crack 
formation is caused by the presence of ozone. Elastomeric polychoroprene 
vulcanizates are particularly susceptible to ozone attack if subjected to 
mechanical stress and flex. Cracks are formed more readily at elevated 
temperatures. 
To prevent crack formation, it is necessary to incorporate an antiozonant 
into the polymer composition. 
It is known that polychloroprene vulcanizates may be protected against 
ozone-cracking by norbornene-type antiozonants. U.S. Pat. No. 3,563,947 
discloses dinorbornene derivatives of alkyl-substituted benzenes and of 
other divalent organic radicals. Enol ethers of norbornene are described 
in U.S. Pat. No. 3,814,727 and acetals or ketals in U.S. Pat. No. 
4,427,817. 
However, various functionally active antiozonants often display adverse 
effects on the compounded or cured elastomeric article. A particularly 
undesirable effect is the tendency of polychloroprene compositions to 
develop undesirable color or staining. Only a few nondiscoloring 
antiozonants are commercially available. Now certain novel norbornene 
derivatives have been discovered that possess antiozonant and antioxidant 
activity as well as nondiscoloring properties in polychloroprene. 
SUMMARY OF THE INVENTION 
According to the present invention there are provided novel compounds of 
the formula 
##STR1## 
wherein the substitutents R.sub.1, R.sub.2 and R.sub.3 represent H, 
methyl, t-butyl and 5-norbornen-2-ylmethoxymethyl group represented by the 
formula 
##STR2## 
provided that at least one of the sustituents is the 
5-norbornen-2-ylmethoxymethyl group. 
The invention further provides neoprene compositions having improved ozone 
and oxygen resistance. 
DETAILED DESCRIPTION OF THE INVENTION 
The novel compounds of the invention may be prepared by reacting about 
equimolar amounts of 5-norbornene-2-methanol, formaldehyde and a phenol in 
the presence of an acid catalyst. The reaction may be represented by the 
following reaction scheme. 
##STR3## 
The acid catalyst may be selected from strong acids such as 
p-toluenesulfonic acid, sulfuric acid, hydrochloric acid and phosphoric 
acid. 
The reaction may be conducted in the presence of an inert solvent. The 
solvent may be selected from aromatic or aliphatic hydrocarbons as for 
example toluene, xylene and hexane. The reaction temperature will depend 
upon the solvent used, that is, upon the azeotropic reaction mixture 
formed. 
The norbornene derivatives of the invention are effective antiozonants. 
When incorporated into elastomeric polychloroprene (neoprene), the 
vulcanizates display good resistance to ozone cracking without 
discoloration. In addition the alkyl substituted derivatives display 
antioxidant properties. 
The homopolymers and copolymers of chloroprene are well known in the art 
and are commercially available. Representive monomers which can be 
copolymerized with chloroprene include aliphatic conjugated diolefins and 
other compounds having a double bond such as vinyl acetate, acrylonitrile, 
acrylic and methacrylic acid and their esters. 
The novel compounds may be added to the polymers in sufficient quantity to 
protect against ozone degradation, for example, between 0.1 and 6.0 
percent by weight and preferably between 0.3 and 3.0 percent by weight 
based on hundred parts by weight of polymer. 
The polychloroprene compositions may contain compounding additives 
necessary for curing, namely metal oxides and accelerators. The metal 
oxides may be selected from zinc oxide, magnesium oxide, lead oxide and 
mixtures thereof. Accelerators may include, among others, N, 
N-di-o-tolylguanidine, alkyl-substituted thioureas, tetramethylthiuram 
disulfide, N-t-butyl-2-benzothiazolesulfenamide and binary systems 
consisting of thiadiazine and metal dithiocarbamate secondary 
accelerators. Other ingredients may be compounded with polychloroprene to 
improve its processing properties and physical characteristics. Among 
others, the following are applicable: antioxidants, plasticizers, 
peptizers, fillers, extenders, reinforcing fillers, and lubricants. 
Any suitable curing procedure and conditions may be employed in the 
invention. Two methods, among others, are to press-cure at a temperature 
of about 138.degree. to 182.degree. C. for about 10 to 120 minutes and to 
vulcanize continuously at a temperature of about 182.degree. to 
204.degree. for about 5 to 150 seconds.

The following examples are submitted to illustrate, but not to limit the 
scope of the invention. Unless otherwise indicated, all parts and 
percentages in the specification and claims are based upon weight. 
EXAMPLE I 
A reactor was charged with 32.8 g (0.20 moles) 2-t-butyl-4-methylphenol, 
6.0 g (0.20 moles) formaldehyde, 24.8 g (0.20 moles) 5 
norbornene-2-methanol, 110 ml toluene and 0.5 g p-toluenesulfonic acid 
catalyst. The reaction mixture was refluxed for 11/2 hours. About 13.8 ml 
water was collected by azeotropic distillation. After cooling the reaction 
mixture, 5 ml of 20% sodium carbonate solution was added to neutralize the 
catalyst. After stripping, hexane was added and the reaction mixture was 
filtered. 
The yield of the product, 
2-(5-norbornen-2-ylmethoxymethyl)-4-methyl-6-t-butylphenol, was 60.6 g. 
EXAMPLE II 
Rubber specimens were prepared according to the formulations given in Table 
I. 
The antiozonant effect of the compounds of the invention was measured by 
two tests: the ozone resistance test according to the ASTM Method 
D-1149-86 and the bent loop ozone cracking test by the ASTM Method 
D-518-86. 
In the ozone resistance method, test specimens measuring 
0.4.times.4.5.times.4.5 cm press cured at 160.degree. C. for 30 minutes 
were clamped in a frame in such a way that elongations of 10 to 100 
percent were obtained at their surfaces. The stretched specimens were 
exposed to 100 parts ozone per hundred million parts air. After 14 days 
stress was measured. 
In the bent loop test the difference in stress was measured at 22% 
elongation after 14 days. 
To determine discoloration tendency by the antiozonants, the specimens were 
exposed to ultraviolet light according to the ASTM Method D-1148-77. 
Brightness was measured before exposure and after exposure for 25 hours. 
To determine antioxidant properties of the compounds, the specimens were 
aged in test tubes (Al blocks) for 70 hours at 121.degree. C. The physical 
properties were determined according to ASTM D-865-81 Test Method. 
The results compiled in Table I show that the compounds of the invention 
have good antiozonant properties. Moreover, the compounds do not discolor 
the cured neoprene specimens. 
Specimens containing the norbornene derivatives of the invention also 
display antioxidant properties in addition to the antiozonant properties 
discussed above. 
The above embodiments and illustrations have shown various aspects of the 
present invention. Other variations will be evident to those skilled in 
the art and such modifications are intended to be within the scope of the 
invention as defined by the appended claims. 
TABLE I 
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1 2 3 4 5 6 
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Formulation, in parts by weight 
Neoprene W 100.0 
100.0 
100.0 
100.0 
100.0 
100.0 
Magnesium oxide 4.0 4.0 4.0 4.0 4.0 4.0 
Zinc oxide 5.0 5.0 5.0 5.0 5.0 5.0 
Stearic acid 0.5 0.5 0.5 0.5 0.5 0.5 
Titanium dioxide 10.0 10.0 10.0 10.0 10.0 10.0 
Kaolin clay 90.0 90.0 90.0 90.0 90.0 90.0 
Plastogen.sup.1 5.0 5.0 5.0 5.0 5.0 5.0 
VANAX CPA.sup.2 1.5 1.5 1.5 1.5 1.5 1.5 
4-(5-Norbornen-2-ylmethoxymethyl)- 
-- 2.0 -- -- -- -- 
2,6-di-t-butylphenol 
2-(5-Norbornen-2-ylmethoxymethyl)-4- 
-- -- 2.0 -- -- -- 
methyl-6-t-butylphenol 
2,4,6-Tris(5-norbornen-2-ylmethoxy- 
-- -- -- 2.0 -- -- 
methyl)phenol 
2,4-Di(5-norbornen-2-ylmethoxymethyl)- 
-- -- -- -- 2.0 -- 
6-methylphenol 
2-(5-Norbornen-2-ylmethoxymethyl)-4,6- 
-- -- -- -- -- 2.0 
di(t-butyl)phenol 
Ozone Resistance 
10% Elongation 0 0 0 0 0 0 
15% Elongation 10 0 0 0 0 0 
20% Elongation 10 0 0 0 0 0 
50% Elongation 10 0 0 0 0 0 
75% Elongation 10 0 0 0 0 0 
100% Elongation 10 0 0 0 0 0 
Bent Loop Ozone Resistance 
22% Elongation 9 0 0 0 0 0 
Brightness 
Before exposure 52.1 51.6 52.1 50.9 50.8 52.1 
After exposure for 24 hours 
10.7 12.2 18.2 11.4 11.6 14.6 
Properties after aging for 70 hours 
at 121.degree. C. 
Tensile 1520 1400 1430 1490 1570 1540 
Elongation, Percent 50 80 260 100 100 140 
Hardness 85 82 79 84 83 81 
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.sup.1 Plastogen .RTM., sulfonic acid type plasticizer, manufactured by 
King Industries 
.sup.2 VANAX .RTM. CPA, dimethylammonium hydrogen isophthalate, 
manufactured by R. T. Vanderbilt Co.