Hot melt butyl sealant intermediate

Intermediate compositions useful for the preparation of improved hot melt butyl sealants are obtained by partially grafting a mixture of a butyl rubber, a different elastomer and/or a crystalline polymeric resin, and an elastomeric resin. Preferred compositions are (1) partially grafted mixtures of butyl rubber, epichlorohydrin rubber, and a block copolyester elastomeric resin, (2) partially grafted mixtures of butyl rubber, ethylene-vinyl acetate copolymer, and a block copolyester elastomeric resin, and (3) partially grafted mixtures of butyl rubber, styrene-ethylene-butylene-styrene block copolymer rubber, and a block copolyester elastomeric resin.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to sealant compositions and more particularly 
relates to intermediates for the preparation of improved hot melt butyl 
sealants. 
2. Description of the Prior Art 
It is known that sealants are useful in various applicance, automotive, and 
construction markets for sealing joints, such as masonry-metal, 
glass-metal, and glass-glass joints. Sealants such as asphalt, mastics, 
and putty have some utility in this regard, but they have the 
disadvantages of containing solvents, exhibiting creep and sag at various 
temperatures, shrinking with age, and having unacceptable moisture vapor 
transmission rates. Hot melt butyl sealants have been found preferable to 
other prior art sealants in many ways. However, even these hot melt butyl 
sealants, which are prepared by mixing the ingredients together in a 
low-shear open mixer (i.e., by "dry mixing"), have properties which could 
bear improvement. 
SUMMARY OF THE INVENTION 
An object of this invention is to provide improved hot melt butyl sealant 
compositions. 
Another object is to provide such compositions via novel intermediate 
compositions. 
These and other objects are attained by mixing and heating (A) a butyl 
rubber having a Mooney viscosity (ML 1+3 at 260.degree. F.) of about 
30-80, (B) about 25-150 phr of (1) a different elastomer selected from the 
group consisting of diene rubbers, polyisobutylene, styrene-olefin 
copolymer rubbers, epichlorohydrin rubber, ethylene-propylene-polyene 
terpolymers, and mixtures thereof and/or (2) a crystalline polymeric 
resin, and (C) about 25-150 phr of an elastomeric resin in an internal 
high-shear mixer at 300-400.degree. F. to effect partial grafting of the 
ingredients. 
The intermediate composition thus obtained may then be compounded with 
other conventional sealant ingredients, such as fillers, extenders, and 
tackifying resins, in a low-shear external mixer to form a hot melt 
sealant.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The butyl rubber of the invention can be any butyl rubber having a Mooney 
viscosity (ML 1+3 at 260.degree. F.) of about 30-80. Thus, it is a 
copolymer of isobutylene with a minor amount, e.g., about 1-5 mol percent, 
of a conjugated polyene, such as butadiene, isoprene, piperylene, 2,3 
-dimethylbutadiene, cyclooctadiene, cyclododecatriene, etc.; and it may be 
slightly crosslinked. It is preferably one of the slightly crosslinked 
butyl rubbers of U.S. Pat. No. 3,674,735. The most preferred butyl rubbers 
are those which have a Mooney viscosity (ML 1+3 at 260.degree. F.) of 
about 50-60. 
The additional elastomer that may be employed in the practice of the 
invention can be any thermosensitive polymer having an approximately 
straight-line relationship in a viscosity-temperature diagram and selected 
from the group consisting of diene rubbers, polyisobutylene, 
styrene-olefin copolymer rubbers, epichlorohydrin rubber, 
ethylene-propylene-polyene terpolymers, and mixtures thereof. Such 
elastomers, of course, are well known. Suitable diene rubbers (i.e., 
rubbery polymers containing at least 50% by weight of combined conjugated 
diene) include, e.g., natural rubber, polybutadiene, butadiene-styrene 
copolymers, isoprene-styrene copolymers, polychloroprene, etc.; suitable 
styrene-olefin copolymers include, e.g., styrene-ethylene-butylene-styrene 
block copolymers having styrene contents of about 25-35% by weight, etc.; 
suitable ethylene-propylene-polyene terpolymers include, e.g., terpolymers 
of ethylene and propylene with up to about 5%, usually about 3-5%, by 
weight of a combined polyene, such as cyclooctadiene, dicyclopentadiene, 
1,4-hexadiene, ethylidenenorbornene, methylenenorbornene, 
1,4,9-decatriene, etc. Particularly preferred are the epichlorohydrin 
rubbers and the styrene-ethylene-butylene-styrene block copolymers. 
The crystalline polymeric resin that is used instead of or in addition to 
the optional elastomer may be any of the crystalline or crystallizable 
polymeric resins conventionally employed in sealant compositions and 
capable of providing a crystalline resin in the processed compositions. 
Exemplary of such polymeric resins are polyethers, such as poly(alkylene 
oxides); polyesters, such as block polyester-polyether copolymers; 
polyamides, such as reaction products of dimer acids and linear diamines; 
polyolefins, such as polypropylene; ethylene-ethyl acrylate copolymers; 
ethylene-vinyl acetate copolymers, etc., and mixtures thereof. 
Particularly preferred are ethylene-vinyl acetate copolymers having 
combined vinyl acetate contents of about 5-35% by weight and 
ethylene-ethyl acrylate copolymers having combined ethyl acrylate contents 
of about 15-25% by weight. 
The amount of optional elastomer and/or crystalline polymeric resin 
employed in the practice of the invention is in the range of about 25-150 
phr, i.e., about 25-150 parts per 100 parts of the butyl rubber. 
The elastomeric resin of the invention, which is also employed at a 
concentration of about 25-150 phr, is a thermoplastic polymer having a 
noticeable deflection in its viscosity-temperature diagram and may be any 
such resin that is conventionally employed in sealant compositions. 
However, it is preferably a block copolyester or a polyamide resin. Most 
preferably, it is a thermoplastic segmented copolyester elastomer having a 
melt index of less than 30 and consisting essentially of about 15-30% by 
weight of ester units derived from butanediol and a phthalic acid and 
about 85-70% by weight of units derived from polytetramethylene ether 
glycol 1500-3500 (i.e., a polytetramethylene ether glycol having an 
average molecular weight of about 1500-3500) and a phthalic acid, about 
55-95% by weight of the phthalate units of the copolyester being 
terephthalate units. 
In the practice of the invention, the butyl rubber, the different elastomer 
and/or crystalline polymeric resin, and the elastomeric resin are mixed 
and heated together in an internal high-shear mixer, e.g., a Banbury 
mixer, to effect partial grafting of the ingredients. This process is 
usually conducted at about 300-400.degree. F., preferably about 
330-360.degree. F., for about 3-10 minutes to accomplish the formation of 
a composition containing at least about 1%, usually about 1-50%, and 
preferably about 1-10%, by weight of graft copolymers of the butyl rubber 
on the other components. When desired, the ingredients are subjected to 
the process in combination with about 25-50 phr of diatomaceous earth to 
facilitate removal of the partially grafted mixture from the mixer. 
The intermediate composition thus obtained may then be compounded with 
conventional sealant additives, e.g., fillers, extenders, tackifying 
resins, additional elastomeric resins, etc., in any suitable manner, e.g., 
in an external low-shear mixer (such as a sigma blade mixer), to form a 
hot melt sealant composition. An advantage of the invention is that hot 
melt sealants prepared from the intermediate compositions of the invention 
have adhesive properties superior to those of hot melt sealants prepared 
by the conventional dry mix method. 
The following examples are given to illustrate the invention and are not 
intended as a limitation thereof. Unless otherwise specified, quantities 
mentioned are quantities by weight. 
EXAMPLE I 
Prepare an intermediate composition from the following recipe: 
______________________________________ 
Ingredient Parts 
______________________________________ 
Butyl rubber having a Mooney viscosity 
(ML 1 + 3 at 260.degree. F.) of 50-60 and a mol 
percent unsaturation of 1.5-2.0 
100 
Styrene-ethylene-butylene-styrene block 
copolymer having a styrene content of 
about 30% and a Brookfield viscosity 
(20% in toluene) of 550 cps at 77.degree. F. 
50 
Thermoplastic segmented copolyester 
elastomer having a melt index of less than 
30 and consisting essentially of about 15- 
30% by weight of ester units derived from 
butanediol and a phthalic acid and about -85-70% by weight of units 
derived from poly- 
tetramethylene ether glycol 1500-3500 and a -phthalic acid, about 55-95% 
by weight of the 
phthalate units of the copolyester being tere- 
phthalate units 50 
Diatomaceous earth 30 
______________________________________ 
Mix the ingredients in a Banbury for 5 minutes and dump at 330.degree. F. 
to recover an intermediate composition, about 1-10% of which consists of 
graft copolymers of the butyl rubber on the block copolymers. Then blend 
this intermediate composition with the following ingredients at 
300.degree. F. for 60 minutes in a sigma blade mixer: 
______________________________________ 
Ingredient Parts 
______________________________________ 
Polyamide resin 100 
Terpene phenolic resin 50 
TiO.sub.2 5 
______________________________________ 
The hot melt sealant thus prepared has the following properties: 
______________________________________ 
Lap Shear to Steel at 75.degree. F. 
138 psi* 
Lap Shear to Steel at 150.degree. F. 
30 psi* 
Peel Strength to Aluminum at 75.degree. F. 
57 lbs./in.* 
Peel Strength to Glass at 75.degree. F. 
40 lbs./in.* 
______________________________________ 
*Cohesive failure? 
EXAMPLE II -- CONTROL 
Prepare a hot melt sealant composition by mixing the Example I ingredients 
entirely in a sigma blade mixer instead of first grafting some of the 
ingredients in a Banbury. The sealant has the following properties: 
______________________________________ 
Lap Shear to Steel at 75.degree. F. 
117 psi** 
Lap Shear to Steel at 150.degree. F. 
20 psi* 
Peel Strength to Aluminum at 75.degree. F. 
54 lbs./in.* 
Peel Strength to Glass at 75.degree. F. 
30 lbs./in.* 
______________________________________ 
*Cohesive failure 
**Adhesive failure 
EXAMPLE III 
Repeat Example I except for preparing the partially grafted intermediate 
from the following recipe: 
______________________________________ 
Ingredient Parts 
______________________________________ 
Butyl rubber of Example I 100 
Ethylene-vinyl acetate copolymer 
having a vinyl acetate content of 
28% and a melt index of 5 50 
Copolyester elastomer of Example I 
25 
______________________________________ 
As in Example I, the sealant has properties superior to the properties of a 
comparable sealant prepared by the dry mix method. 
EXAMPLE IV 
Repeat Example I except for preparing the partially grafted intermediate 
from the following recipe: 
______________________________________ 
Ingredient Parts 
______________________________________ 
Butyl rubber of Example I 100 
Epichlorohydrin rubber 100 
Copolyester elastomer of Example I 
100 
Diatomaceous earth 30 
______________________________________ 
As in Example I, the sealant has properties superior to the properties of a 
comparable sealant prepared by the dry mix method. 
Similar results are observed when the examples are repeated except that 
ingredients are replaced by ingredients taught to be their equivalents in 
the specification. 
It is obvious that many variations may be made in the products and 
processes set forth above without departing from the spirit and scope of 
this invention.