Epoxide and rubber based curable compositions having good adhesion direct to metal

Description of the object of the invention which

PPG INDUSTRIES, INC., North American, (State of Pennsylvania), industrial, established in One PPG Place, Pittsburgh 22, 15272, State of Pennsylvania, United States of America, wishes to obtain in Portugal for COMPOSITION PREPARATION PROCESS RUBBER AND EPOXIDE WITH GOOD DIRECT ADHESION TO METAL.

The present invention relates to a process for preparing curable compositions suitable for use as adhesives and sealants.

In car construction and assembly, adhesives and seals are used for a wide variety of different purposes. As a result, and depending on the use, each adhesive or sealant has different requirements for physical properties, such as a certain shear stress limit at a given temperature, a large latitude of cure temperatures with the ability to cure both. very high temperatures such as very low temperatures, elasticity, good elongation and good adhesion and different substrates.

For this reason, and due to the diversity and disparity of requirements, a different adhesive or sealant has been required for each of the different automotive construction applications. For example, different materials have been used as structural adhesives, filler seals or anti-vibration adhesives.

There is therefore a need for a unique curable composition that can be used for a variety of different purposes and which has the ability to adapt to all the different physical properties required.

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In accordance with the present invention there is provided a unique, stable and curable composition comprising:

(a) a polydiene;

(b) a polyepoxide;

(c) a sulfur and zinc-containing vulcanization system adapted to cure polydiene and epoxide; and (d) an anhydride-containing material adapted to promote adherence of the curable composition to the metal.

Also provided is a method for preparing an adhesive bond between two surfaces to form a bonded structure.

The curable composition according to the present invention comprises, as one of its main constituents, a polydiene.

Polydien polymers include 1,3-diene polymers containing from 4 to 12 and preferably from 4 to 6 carbon atoms. Typical dienes include 1,3-butadiene which is preferably 2,3-dimethyl-1,3-butadiene, isoprene, chloroprene and piperylene. 1,3-Butadiene copolymers and a 1,3-butadiene copolymerizable monomer such as isoprene, acrylonitrile and piperylene may also be used. Other polymerizable monomers may also be used, such as methyl metharylate, acrylic acid and styrene. Preferably, the polydiene polymer is a mixture of 1,4-polybutadiene and a 1,4-polybutadiene acrylonitrile copolymer.

If desired, a variety of synthetic rubbers, whether or not vulcanizable, may be used as inert filler material together with the polydiene. Examples of such synthetic rubbers include butyl rubber, ethylene propoliene terpolymer, silicone rubbers, polysulfides, polyacrylate rubbers and chlorinated polyethylene rubbers. Copolymers of the above synthetic rubbers may also be used.

It is to be understood that the polydiene polymer according to the present invention may be either functional or non-functional. In preferred embodiments, the polydiene polymer is non-functional, or

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that is, they do not contain functional groups such as, for example, hydroxyl, amino, carboxyl or mercapto.

Another major constituent of the claimed curable compositions is a polyepoxide.

Polyepoxides are materials that have a 1,2 epoxide group present in the molecule. Hydroxyl groups may be present which often happens. A polyepoxide for the purposes of the present invention contains at least two 1,2-epoxide groups per molecule. Generally, the equivalent weight of epoxide ranges from about 289 to 4,000. These polyepoxides are saturated or unsaturated, cyclic or acyclic, aliphatic, alicyclic, aromatic or heterocyclic. They may contain substituents such as halogen, hydroxyl or ether groups.

A useful category of polyepoxides comprises epoxide polyesters obtained by reacting an epihalohydrin (such as epichlorohydrin or epibromohydrin) with a polyphenol in the presence of an alkaline element. Suitable polyphenols include resorcinol, catechol, hydroquinone, bis (4-hydroxy-phenyl) -2,2-propone, ie, bisphenol A; bis (4-hydroxyphenyl) -1,1-isobutane; 4,4-dihydroxybenzophenone; bis (4-hydroxyphenyl) -1,1-ethane; bis (2-hydroxyphenyl) methane; and 1,5-hydroxynaphthalene. A very common polypeptide is a polyphenidyl ether of a polyphenol, such as bisphenol A. More preferably the polyepoxide is a bisphenol A diglycidyl ether.

Another category of polyepoxides are polyglycidyl ethers of polyhydric alcohols. These compounds may be derived from polyhydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,4-butylene glycol, 1,5-pentanediol, 1,2,6-hexanetriol, glycerol, trimethylopropane and bis (4-hydroxycyclohexyl-2,2-propane.

Another category of polyepoxides are polyglycidyl esters of polycarboxylic acids. These compounds are produced by reacting epichlorohydrin or a similar epoxy compound with an aliphatic or aromatic polycarboxylic acid such as oxalic acid, succinic acid, glutaric acid, terephthalic acid, 2,6-naphthalene dicarboxylic acid or linoleic acid. dimerized.

Yet another category of polyepoxide is derived from epoxy-360174

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an olefinically unsaturated alicyclic compound. These polyepoxides are non-phenolic and are obtained by epoxidation of alicyclic olifines, for example by means of oxygen and selected metal catalysts, perbenzoic acid, acid aldehyde monoperacetate or peracetic acid. Among such polyepoxides are the epoxy alicyclic esters and ethers well known in the art.

Useful polyepoxides also include those containing oxyalkylene groups in the epoxy molecule. Another category of polyepoxides is novolac epoxy resins. These resins are obtained by reacting an epihalohydrin with the aldehyde monohydrate condensation product or epichlorohydrin with a phenol formaldehyde condensate.

Another group of epoxide-containing materials includes acrylic copolymers containing copolymerized glycidyl acrylate or copolymerized glycidyl methacrylate. These acyclic copolymers may be prepared by sectioning alkyl esters of alpha, beta unsaturated mono- or di-carboxylic acid with glycidyl acrylate or methacrylate. Or other glycidyl-containing copolymerizable monomers such as diglycidyl itaconate and diglycidyl maleate may also be used. These monomers may optionally be copolymerized in the presence of other copolymerizable monomers such as vinyl aromatic compounds such as styrene or vinyl toluene, as well as acrylonitrile or methacrylonitrile.

Preferably the polyepoxide is a diepoxide. Preferably bisphenol A polyglycidyl ether, more preferably a diglycidyl ether is used. Examples of suitable materials are EPON epoxy resins marketed by Shell Chemical, such as EPON 828.

It should be understood that mixtures of the above described polyepoxides may be used herein.

In preferred embodiments of the present invention an epoxy rubber supplement is used as a supplementary additive in order to achieve optimal adherence of the curable composition to the oily metal. A preferred supplement is that which is prepared from an excess of bisphenol A diglycidyl ether, for example EPON 828 from Shell Chemical and a carboxyl-terminated acrylonitrile polybutadiene copolymer, for example.

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for example, BFGoodrich CTBN. The resulting epoxy functional supplement is free of carboxyl functionality.

Another major constituent of the claimed curable compositions is a sulfur and zinc-containing vulcanization system which is adapted to cure the polydiene and polyepoxide components.

As used herein, vulcanization means the physicochemical modification that results from the chaining of polydiene with sulfur, generally after heat is applied. It is not yet fully known exactly what mechanism produces the lattice structure during curing of the claimed compositions. However, it is theorized that epoxide may be incorporated into the polyidiene rubber lattice. 0 The vulcanization system comprises a material or mixture of materials which are adapted to effect curing of polydene and polyepoxide. Preferably the vulcanization system comprises a lower alkyl dithiocarbamate and a disulfide. A large number of lower alkyl dithiocarbamates are useful herein, particularly those having from 1 to 10, preferably from 1 to 5, carbon atoms in the alkyl moiety. Examples of suitable dithiocarbamates include methyl, ethyl, propyl, butyl and amyl dithiocarbamates. Dibutyl dithiocarbamate is preferably used herein. These materials are commercially available in combination with salts as zinc, namely zinc dibutyl dithiocarbamate, dimethyl zinc dithiocarbamate, diethyl zinc dithiocarbamate and zinc diamyl dithiocarbamate. These materials are marketed by Vanderbilt Chemical Company under the registered trademark ZIMATE.

Zinc that is part of the vulcanization system can be produced in different ways. Above an example has been provided in connection with the vulcanization system; that is, zinc may be associated with lower alkyl dithiocarbamate in salt form. Zinc may also be introduced as zinc oxide. It will be appreciated that a wide variety of zinc oxide grades are available which can be used for this purpose.

The amount of zinc present in the vulcanization system can vary widely, usually from about 0.1 weight percent to about 10 weight percent, based on the total weight of the curable composition. It is not known

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precise mechanism; However, zinc is believed to function as an accelerator for sulfur vulcanization.

The disulfide component of the vulcanization system can also be chosen from a wide variety of materials. Examples of suitable disulfides include 4-molfolinyl-2-benzothiazole disulfide; 4,4'-dithiobismorpholine and benzothiazyl disulfide. Preferably the disulfide is benzothiazyl disulfide. The di-thiocarbamate and disulfide components of the vulcanization system are believed to function as primary and secondary accelerators, respectively, for the vulcanization reaction. Furthermore, in preferred embodiments of the present invention, the disulfide form is believed to function as a retarder for premature vulcanization. Thiocarbamate is believed to act in conjunction with sulfur to effect the cured, cross-linked system. It is also believed that thiocarbamate not only assists in vulcanizing the rubber component but also acts to incorporate the epoxide component into the crosslinked chain. As mentioned above, the precise mechanism of this reaction is not known.

Another constituent principle of the claimed curable compositions is an anhydride-containing material that is adapted to promote adherence of the curable composition to the metal. A wide variety of carboxylic acid anhydrides are considered within the scope of the present invention as long as they have the ability to promote adherence of the curable composition directly to the metal. Preferably the anhydride-containing material is a carboxylic acid anhydride selected from the group consisting of maleic anhydride, itaconic anhydride and phthalic anhydride. Preferably, when a carboxylic acid anhydride is used, maleic anhydride is used. If desired, mixtures of the aforementioned carboxylic anhydrides may be used. The anhydride-containing material may also be an anhydride supplement. That is, a supplement comprising the reaction product of a carboxylic acid anhydride which is adapted to promote adherence of the metal curable composition with an olefinically saturated material. Preferably the carboxylic anhydride which is admixed with the olefinically unsaturated material is one of the anhydrides listed above. More preferably it is maleic anhydride.

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Examples of olefinically unsaturated material supplements include compounds formed from an appropriate anhydride as defined above in, for example, ene-type reactions and free radical initiated polymerizations. Examples thereof include compounds formed from a free radical initiated polymerization of two moles of 1-octene or 1-diene with one mole of maleic anhydride; and compounds not formed by heating a polydiene such as polybutadiene with maleic anhydride.

Preferably, the claimed curable compositions are prepared in the form of a moisture free system. The presence of water is not preferred because it opens the anhydride ring structure and interferes with the desired cure. Therefore, typically, desiccant materials are added to remove water from the system.

In addition, the carboxylic acid anhydride is preferably pretreated by heating in the presence of a diepoxide for a period of at least about five minutes at a temperature ranging from about 60 ° C to 150 ° C. It has been observed that when this pretreatment is carried out, the carboxylic acid anhydride remains substantially unreacted. Pretreatment is an apparent dissolution of the anhydride into epoxide. This result was confirmed by infrared spectroscopy, numerical acid determinations and gel permeation chromatography. Carbocylic acid anhydride has been found to provide optimum stability and also good performance in promoting adhesion to the metal when treated in this manner.

In preferred embodiments of the present invention, the claimed curable composition is essentially free of amino group-containing materials. The presence of amine is not preferred because it decreases the elasticity of the resulting cured composition.

The amounts of each of the constituents of the claimed curable composition may vary widely, depending upon the particular use and properties desired for the curable composition. For example, by varying the amount of polyepoxide and dithiocarbamate that is used in the curable composition, the hardness of the final cured composition can be varied at will. The more polyepoxide and dithiocarbamate is used, the harder and stronger the polyepo polyidiene cured material will become.

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SnJS88_; oxide. Generally, the amount of polydiene that is used in the claimed curable composition may vary within the range of from 2 weight percent to about 80 weight percent. Preferably, the amount of polydiene used ranges from about 5 weight percent to about 50 weight percent, and more preferably from about 10 to 15 weight percent. The amount of polyepoxide may generally vary: within the range of from about 1 to 75 weight percent, preferably from about 5 to 40 weight percent, and most preferably from about 10 to 20 weight percent. the percentages being all based on the total weight of the curable composition. The sulfur-containing vulcanization system is used in amounts ranging from about 0.5 to 25 weight percent, based on the total weight of the curable composition.

In preferred embodiments the dithiocarbamate primary accelerator may be present in an amount ranging from about 0.1 to 7 weight percent, preferably from about 0.5 to 3 weight percent, and more preferably from about 1 to about 5 weight percent. 2 percent by weight. 0 secondary disulfide accelerator may be present in an amount ranging from about 0.2 to 14 weight percent, preferably from about 1 to 6 weight percent, and more preferably from about 2 to 4 weight percent. All percentages are based on the total weight of the curable composition.

The amount of sulfur that is part of the vulcanization system can also be very variable. Generally, the amount of sulfur ranges from about 0.1 to 15 weight percent, preferably from about 0.2 to 5 weight percent, and more preferably from about 0.5 to 1.5 weight percent. weight, the percentages being based on the total weight of the curable composition. 0 Sulfur may be used in a wide variety of forms but is typically elemental sulfur and is presented as an oil-treated solid powder. Suitable sources of sulfur are, for example, for the vulcanization system, the CRYSTEX brand sulfur which is marketed by the Stauffer Chemical Company.

It should be understood that the accelerator materials discussed above may contribute a lower amount of sulfur to the sulfur content required by the vulcanization system.

The amount of anhydride-containing material may also vary.

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a lot, depending on the particular choice of material that has been made.

Where the anhydride-containing material is an unreacted carboxylic acid anhydride, the amount may generally range from about 0.1 to 10 weight percent, preferably from about 0.2 to 5 weight percent, and more. preferably between about 0.3 and 1.5 weight percent. When the anhydride-containing material is a supplemental compound of an appropriate anhydride and an olefinically unsaturated material, the amount of the compound may range from about 0.1 to 20 weight percent, preferably from about 0.5 to 10 weight percent. percent by weight and more preferably from about 4 to 8 percent by weight. All the above percentages are based on the total weight of the curable composition.

The claimed curable compositions may comprise a wide variety of other optional additives in addition to the major constituents which have been detailed above. Examples of such additives include fillers such as calcium carbonate, stearic acid treated calcium carbonate, polybutadiene treated calcium carbonate, barium sulfate, calcium and magnesium oxide, carbon black, hydrocarbon binders and various plasticizers and phthalate and adipate antioxidants. Examples of suitable antioxidants are butylated hydroxytoluene, butylated and styrenated phenols and cresols, alkylated quinones and hydroquinones and butylated hydroxy benzyl isocyanates.

The claimed stable and curable unit compositions have a very wide latitude of curing temperatures. The claimed curable compositions may be cured by baking at a temperature of about 220 ° F to 5502 ° F (1042 ° C and 2882 ° C) for a period of time ranging from about 10 to 60 minutes. Preferably, the claimed curable compositions are cured by baking at a temperature between about 3252F and 4002F (1632C to 2042C) for a period of time ranging from about 15 to 30 minutes. A very unexpected advantage of the claimed curable compositions is their ability to cure at both very high and very low temperatures, while achieving comparable physical properties at both ends. This ability reduces the problems associated with undercooking or undercoating and allows manipulation of the compositions to suit a wide variety of application conditions.

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Furthermore, the claimed curable compositions have astonishing direct adherence to metal, particularly to oily metal. In addition, the claimed curable compositions can adhere to a wide variety of other substrates such as aluminum, compressed metal, plastic, wood and other substrates. The anhydride-containing material is believed to be very important in achieving adherence of the claimed curable compositions directly to the metal.

The claimed curable compositions may be applied by any conventional means, although typically they are applied by extrusion.

The stable, curable unit compositions also demonstrate a wide variety of other advantageous properties such as solvent resistance, heat resistance, good elongation, elasticity, good crack resistance due to high temperature shear and furthermore exhibit a Good overall resistance at room temperature. The claimed curable compositions also exhibit good cohesiveness. They also have excellent stability when packaged for extended periods of up to three months.

The following examples are intended to be illustrative of the present invention and are not intended to be limiting.

EXAMPLE I

This example illustrates the preparation of a curable composition according to the claimed invention.

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(D (2) (3) (4) (5) (6) (7) (8) (9)

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Ingredients * 1

HYCAR 1312 LV¹EPON 828²MULTIFLEX SC³Butylated Hydroxytoluene Butyl Zimate

ALTAX ⁵POLYOL 130⁶Calcium Carbonate Calcium Oxide Sulfur

Carbon Black EPOXY-CTBN Composite Plasticizer⁹IDMA / STEREON 840 A¹⁰Maleic anhydride

Parts by weight (grams)

12.85 13.22 23.10

1.92

0.86

1.72

11.26

17.75

5.17 ..

1.72

1.25

0.96

5.75

1.00

0.50

This unsaturated resin is a butadiene acrylonitrile copolymer which is marketed by BFGoodrich.

This epoxy resin is bisphenol A diglycidyl ether which is marketed by Shell Chemical Company. It has an epoxy weight equivalent to 185 to 192.

It is a stearic acid treated calcium carbonate which is marketed by Pfizer.

It is a zinc dibutidithiocarbamate marketed by RTVanderbilt Chemical Co.

It is benzothiazyl disulfide marketed by RTVanderbilt Chemical Co.

This unsaturated resin is the polymerization product of 1,3-butadiene which is marketed by Huls. The molecular weight is approximately 3,000.

It is Stauffer Chemical's CRYSTEX OT-90 which is an oil-treated powder with a sulfur content of 9 percent.

Diisododecyl phthalate plasticizer.

This epoxy resin is the reaction product of a copolymer.

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of carboxy-terminated acetonitrile butadiene (available from BFGoodrich) and excess EPON 828.

(10) It is a 30 weight percent dissolution product of STEREON 840A, a styrene-butadiene copolymer marketed by Firestone, in 70 percent isodecyl methacrylate. It was used as a flux additive.

(11) The maleic anhydride was heated for approximately one hour at 120 ° C with EPON 828. It is shown by IR, CPG and acid content that the maleic anhydride in this solution is essentially unreacted.

The adhesive composition was prepared by combining the ingredients under gentle agitation. The composition was tested for physical properties as follows.

Shear Strength: Bonds for the overlapping shear strength test were prepared using two 1 inch x 4 inch x 0.062 inch (2.54cm x 10.16 cm x 0.158) cold rolled steel strips cm). An 118 mil (2.95 mm) film thickness of a composition was applied to one of the metal strips and then a second strip was placed over the first strip so that only half a square inch (3.16 square centimeters) of strip would overlap. The composition was cured at 160 ° C for 30 minutes, 19 ° C for 30 minutes and at 2052 ° C for 120 minutes (three different bonds were prepared, one for each temperature). The shear strength of the attached overlap flaps, in pounds per square inch (psi) (newtons per square millimeter), was determined according to ASTM D-1002-65. Data presented for each temperature were an average of three separate determinations. (The ends of the strips were pulled by an INSTRON TESTER device and the shear strength of the overlapping flaps was measured).

Tensile Strength: A 0.100 inch (0.254 cm) layer of a composition was applied onto a treated TEFLON glass panel measuring 12 inches x 12 inches x 0.100 inches (30 cm x 30 cm x 0.254 cm). The composition was cured by baking at 190 ° C for 30 minutes and then the panel was cooled to room temperature. The free films were prepared and evaluated for strength.

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tensile strength according to ASTM D 638. Each of the values ​​in psi (newtons per square millimeter) is an average of three separate determinations. Percent elongation was also determined according to this ASTM test.

Ghore Hardness A: A 0.100 inch (0.254 cm) thick layer of a composition was applied to a metal panel. The composition was cured by baking at 190 ° C for 30 minutes and then cooled to room temperature. Shore A hardness was determined using a Shore Durometer Hardness Type A-2 instrument in accordance with ASTM D676.

T-Peel Resistance: The composition was evaluated for T-peel resistance according to ASTM D1876. Bonds for the evaluation of peel strength T were prepared as follows. Two cold-rolled metal strips measuring 1 inch x 6 inches x 0.031 inch (2.54 centimeters x 15.24 centimeters x 0.079 centimeters) were used. A 118 mil (2.95 mm) thick film of adhesive composition was applied over one of the metal strips and then a second metal strip placed over the first strip so that a 4 square inch (25.81 cm) section squares) was on. After two ends of the unbound panels were bent to form a T. The charge for determining the T-shell was applied at 5.0 inches (12.7 centimeters) per minute. Peel strength T is measured in pounds per linear inch (lbs / in) (kilinewtons per meter). The results are presented below:

Shear strength at 1902C / 30 min:

410 psi (2.8 newtons / mm ^)

Shear strength at 1102C / 30 min:

280 psi (1.9 newtons / mm ^)

Shear strength at 2052C / 120 min:

360 psi (2.5 newtons / mn /)

Peel Strength T: 38 psi (2.6 kilinewtons / meter)

Tensile strength: 508 psi (3.5 newtons / mm ^)

Elongation: 180 percent

Shore A hardness: 68

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EXAMPLES II TO V

<td rowspan="2">Ingredients</td><td>(parts II</td><td>by weight III</td><td>in grams) IV *</td><td>V</td><td>SAW</td>

<td></td><td> -</td><td></td><td> —</td><td></td>

<td>HYCAR 1312 LV</td><td> 16.60</td><td> 12.85</td><td> ’ .12.85</td><td> 12.85</td><td> 12.85</td>

<td>EPON 828</td><td> 15.22</td><td> 13.22</td><td> 13.22</td><td> 13.22</td><td> 13.22</td>

<td>MULTIFLEX SC</td><td> 23.10</td><td> 23.10</td><td> 23.10</td><td> 23.10</td><td> 23.10</td>

<td>Butylated Hydroxytoluene</td><td> 1.92</td><td> 1.92</td><td> 1.92</td><td> 1.92</td><td> 1.92</td>

<td>Butyl Zimate</td><td> 0.86</td><td> 0.86</td><td> 0.86</td><td> 0.86</td><td> 0.86</td>

<td>ALTAX</td><td> 1.72</td><td> 1.72</td><td> 1.72</td><td> 1.72</td><td> 1.72</td>

<td>POLYOL 130</td><td> 11.26</td><td> 11.26</td><td> 11.26</td><td> 11.26</td><td> 11.26</td>

<td>Calcium carbonate</td><td> 17.25</td><td> 17.25</td><td> 17.25</td><td> 17.25</td><td> 17.25</td>

<td>Calcium oxide</td><td> 5.17</td><td> 5.17</td><td> 5.17</td><td> 5.17</td><td> 5.17</td>

<td>Note Sulfur (7)</td><td> 1.72</td><td> 1.72</td><td> 1.72</td><td> 1.72</td><td> 1.72</td>

<td>Black coal</td><td> 1,25</td><td> 1.25</td><td> 1.25</td><td> 1.25</td><td> 1.25</td>

<td>Note Plasticizer (8)</td><td> 0.96</td><td> 0.96</td><td> 0.96</td><td> 0.96</td><td> 0.96</td>

<td>Epoxy-CTBN composed of</td><td> 0.00</td><td> 5.75</td><td> 5.75</td><td> 0.00</td><td> 5.75</td>

<td>grade (9) IPDA / STEREON 840A</td><td> 1.00</td><td> 1.00</td><td> 1.00</td><td> 1.00</td><td> 1.00</td>

<td>Maleic anhydride</td><td> 0.50</td><td> 0.00</td><td> 0.00</td><td> 0.50</td><td> 0.00</td>

<td>Phthalic anhydride</td><td> 0.00</td><td> 0.00</td><td> 4.00</td><td> 0.00</td><td> 0.00</td>

<td>Itonic anhydride</td><td> 0.00</td><td> 1.50</td><td> 0.00</td><td> 0.00</td><td> 0.00</td>

<td>Acid Compound</td><td> 0.00</td><td> 0.00</td><td> 0.00</td><td> 5.75</td><td> 0.00</td>

<td>dimeric epoxy 12 Resin composite</td><td> 0.00</td><td> 0.00</td><td> 0.00</td><td> 0.00</td><td> 2.00</td>

maleic anhydride 13 (12) This epoxy resin is the reaction product of rosin dimeric acid and EPON 828 in excess of EPON 828.

(13) This Diels-Alder compound was prepared by reacting 0.9 moles maleic anhydride with 1 mole rosin at 180 ° C for 4 hours.

* It had less than two weeks of packaging stability at room temperature.

Each of the adhesive compositions was prepared and evaluated as described in Example I above. Evaluations were performed by shear strength of overlapping flaps, elongation

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<td>and hardness</td><td>Shore A.</td><td colspan="3">The results appear below. The curing temperature</td>

<td>from 1902C</td><td>during</td><td>30 minutes in</td><td>Examples II to V.</td><td></td>

<td>Example</td><td colspan="2">Shear strength (osi) (newtons / mm ^)</td><td>Stretching. (percentage)</td><td>Shore A hardness</td>

<td>II</td><td> 366</td><td> 2.54</td><td> 60</td><td> 64</td>

<td>III</td><td> 210</td><td> 1.46</td><td> 180</td><td> 65</td>

<td>IV</td><td> 140</td><td> 0.97</td><td> 120</td><td> 90</td>

<td>V</td><td> 180</td><td> 1.25</td><td> 90 .</td><td> 38</td>

<td>SAW</td><td> 215</td><td> 1.49</td><td> 100</td><td> 70</td>

The first application for the invention described above was filed in the United States on September 28, 1987, under No. 211 700.