GB2097401A

GB2097401A - Rapid cure adhesive sealant

Info

Publication number: GB2097401A
Application number: GB8208441A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-03-24
Filing date: 1982-03-23
Publication date: 1982-11-03
Also published as: JPS57202367A; GB2097401B; CA1229696A; JPH0257592B2; DE3210608A1

Abstract

A putty-like adhesive sealant composition comprises a first band of an uncured reactive polymer or resin adhesive sealant composition and a second band comprising a composition capable of curing the uncured reactive polymer or resin composition within about ten minutes from the time when the first band and the second band are combined to form a substantially uniform mixture. Preferably, the second band comprises an inner core of a fast curing agent enveloped by an outer surrounding wrap of a curing agent composition capable of protecting said fast curing agent from premature reaction with said uncured reactive polymer or resin, and from reaction with the atmosphere where the curing agent becomes oxidized and prematurely hard. It is particularly preferred for the uncured reactive polymer or resin to be an epoxy resin.

Description

SPECIFICATION Rapid-cure adhesive sealant The present invention relates to adhesive sealants, especially in tape form, in which a first band contains an uncured reactive polymer or resin and a second band contains a curing agent therefore.

U.S. Patents Nos. 3,708,379 and 3,837,981 describe elastomeric tape and exoxy tape, respectively. The epoxy tape described particularly in the latter patent specification is marketed commercially as an adhesive sealant for a wide variety of applications.

A commercial form of epoxy tape made in accord with U.S. Patent No. 3,837,981 has a band of uncured epoxy ribbon which is brilliant blue in close side-by-side relation with a band of a curing composition which is yellow. When substantially equal portions of the two bands of material are mixed to form a uniform mixture, an adhesive sealant is formed which may be applied or used for any purpose. The adhesive sealant formed on uniform mixing of substantially equal portions of the epoxy resin and curing agent compositions has a putty-like consistency, and when used to adhere or seal has inherent ability to stay where it is applied even without support or clamping means to hold the objects being adhered together during the time required for the curing of the epoxy resin.

Epoxy resin products made in accord with U.S.

Patent No. 3,837,981 may be formulated so as to fully cure to a solid epoxy adhesive in approximately four to twenty-four hours. For general applications the time required for curing of the adhesive sealant is practical and not objectionable.

However, there are instances when it is desirable to have an extremely fast curing epoxy adhesive sealant, i.e. one which may be applied and cured in a matter of a few minutes rather than hours. Although fast curing epoxy adhesive sealants are known, such products have not heretofore been known in a form similar to that illustrated in U.S. Patent No. 3,837,981. Typically, fast curing epoxy adhesive sealants exist in liquid form and it is necessary to combine a portion of a liquid epoxy resin with a portion of a liquid curing agent. The disadvantages of such products are obvious, and include the problem of cross contamination of the epoxy resin and curing agent, which could result in loss of the supply of each component, and the necessity for packaging each component separately, with the expense inherent in this procedure.A further drawback has been that, typically, such fast cure agents are extremely air sensitive, being rendered unsuitable for use by oxygen, humidity or other components of the atmosphere. Thus, it has not been possible to make use of fast curing agents unless they have been packaged in containers which are impervious to the atmosphere.

According to this invention, a putty-like room temperature, fast-cure, adhesive sealant comprising a first band of an uncured reactive polymer or resin adhesive sealant composition and a second band comprising a composition capable of polymerizing or curing the uncured reactive polymer or resin composition when the first and second bands are combined to form a substantially uniform mixture, is improved in that the second band comprises an agent capable of polymerizing or curing the uncured reactive polymer or resin to a hard adhesive sealant within about ten minutes from the time when the uncured reactive polymer or resin composition and the curing composition are combined to form a substantially uniform mixture.

Suitably, the second band and/or the sealant as a whole is enveloped in an outer surrounding wrap of a composition which is capable of protecting the fast-cure curing agent from premature reaction with the uncured reactive polymer or resin, and in the latter event the atmosphere as well, but which preferably is capable of curing the reactive polymer or resin itself.

In a particularly preferred embodiment of this invention a formulation of an uncured epoxy resin and fast-cure curing agent, particularly one capable of forming a useful adhesive sealing having a Shore A hardness of 30 or more within about five minutes after mixing, is provided.

Thus, the present invention provides an improved epoxy adhesive sealant which is in putty form and is useful by simple, particularly manual, mixing and molding techniques. In its preferred forms the sealant is protected from adverse effects of the atmosphere. It is not necessary that the product of this invention be in any particular configuration illustrated in U.S. Patent No.

3,837,981, although the product may exist in the side-by-side configuration depicted in that patent, or in any form in which the respective bands are in reasonably continuous form even through there is no actual touching of the bands in side-by-side relationship.

In the accompanying drawing, Figure 1 is a pian view illustrating an embodiment of the fast-cure adhesive sealant of this invention, Figures 2, 4 and 5 are cross-sectional views of different embodiments of the invention, while Figure 3 is a cross-sectional view taken along the line 3-3 of Figure 1.

The room temperature, fast cure adhesive sealant of this invention has two principal components. First, it includes an uncured reactive polymer or resin, and second, a curing system for the reactive polymer or resin.

In preferred embodiments, epoxy resin, which are complex polymeric reaction products of polyhydric phenols with polyfunctional halohydrins, are used. Useful epoxy resins are described more completely in U.S. Patent No.

3,837,981. Useful reactive polymers include styrene resins which are cured by free radical polymerization with organo peroxide curing agents. Also silicone adhesive sealants, where the silicone polymer would be cured by moisture sensitive organo tin crosslinking agents, are encompassed by this invention. However, whilst this invention encompasses room temperature, fast-cure adhesive sealants containing polyester and silicone resins, it will be described in detail only with respect to epoxy resin adhesive sealant compositions.

The curing system for the uncured epoxy resin compositions useful in this invention suitably comprises two components, each being a curing agent for epoxy resins. Polyamide compositions are typically used as curing agents for epoxy resins.

As is known, specific epoxy resins react differently with specific curing agents. One can vary the time required for complete curing of an epoxy resin by varying the specific polyamide curing agents and/or varying the amount of polyamide curing agent. Curing agents which can be expected to provide a fast cure of an epoxy resin, i.e. a cure which is complete within about 10 minutes from the time when the epoxy resin composition and curing composition are combined to form a substantially uniform mixture, are generally recognized as being relatively airsensitive. Air-sensitive epoxy resin curing systems generally comprise liquid polymercaptan polymers and accelerators such as an aminophenol, which undergo such degradation as to lose their ability to cause curing of an epoxy resin as the result of interaction with the atmosphere.It has been found that a roomtemperature fast-cure epoxy resin adhesive sealant may be formulated using only a polymercaptan curing agent, and curing will be effected within about 5 to 10 minutes. It has also been found that adhesive sealants in which curing occurs in 5 minutes or less may be formulated if the curing agent includes accelerators as well as the polymercaptan polymer.

The fast-cure curing agent, i.e. a curing agent effective to cause curing of the epoxy resin used in this invention within about ten minutes, may comprise a liquid polymercaptan polymer and/or an aminophenol. Epoxy resins have been cured with polymercaptan-aminophenol curing agent systems in the past. The air-sensitive nature of such curing systems, and their liquid form, has heretofore made it impossible to use such curing systems in epoxy tape products of the type described in U.S. Patent No.3,837,981. Liquid polymercaptan polymers useful as the fast-cure curing agent in this invention include those having a mercaptan value (milliequivalents per gram), of 1 to 20, preferably 3 to 4. Such polymers are available commercially under the trademark Capcure from Diamond Shamrock, Inc.

In embodiments where extremely rapid cure (less than five minutes) is desired the liquid polymercaptan polymer is used in conjunction with an aminophenol. Useful amines are available commercially under the tradenames DMP 30 and DMP 10 from Rohm and Haas Company. The polymercaptan polymer and aminophenol may be combined in a weight ratio of from about 20:1 to about 5:1, preferably about 6 :1, to form the fastcure curing agent for use in this invention. It is possible that either the polymercaptan or the aminophenol components could be used alone to effect cure of the epoxy resin present in the compositions of the invention. However, a significant attribute of the invention lies in the fact that the adhesive sealant may be mixed and applied by hand.It is known that the aminophenol curing agents may cause skin irritation, this it is desired to minimize contact of these agents with the skin. Accordingly, the aminophenol curing agents are desirably used only in those levels sufficient to effect room-temperature fast-cure within the desired 10 minute period. This may be accomplished when the curing agent contains 5% by weight or less of the aminophenol component.

The polymercaptan polymer and aminophenol fast-cure curing agents are rather low viscosity liquids, and they are air-sensitive compounds as stated above. These components are made useful in an epoxy tape product of the type described in U.S. Patent No. 3,837,981 by combining them with components to provide compositions having physical properties required for forming a puttylike product. Thus, the fast-cure curing agents may be combined with various fillers, plasticizers, colorants and other special purpose ingredients. In preferred embodiments, the low-viscosity liquid fast-cure curing agent is combined with a highviscosity polyamide resin or blend of polyamide resin in a weight ratio of about 1:1 to 2 :1, and with an inert carrier such as talc, to form a puttylike composition which may be extruded in tape form.

While the blend of room-temperature fast-cure curing agent and polyamide resin described above may have a putty-like consistency so as to be amenable to extrusion in tape form, it is airsensitive, and thus is not amenable to use a curing agent for an epoxy resin in the embodiments depicted and described in U.S. Patent No.

3,837,981. Such a product is unlike that depicted in Figure 4 of U.S. Patent No. 3,837,981 comprising epoxy resin base and curing agent. The amount of polyamide curing agent required for this purpose is not critical so long as the roomtemperature fast-cure curing agent is protected from exposure to the atmosphere. This is generally accomplished by enveloping the putty-like roomtemperature fast-cure curing agent with a layer of polyamide curing agent from about 0.5 to 2 mm in thickness. Any inert putty-like material which is compatibie with the epoxy resin may be useful in forming the protective envelope. The envelope can be applied by mutual extrusion of the roomtemperature, fast-cure curing agent and polyamide or the curing agent could be placed in a molten polyamide resin bath from which a coating of the polyamide would adhere to the curing agent.

Figure 2 of the accompanying drawing illustrates an epoxy tape in which Band B contains the epoxy resin composition, band A contains the fast-cure curing agent and band C contains the polyamide resin curing composition which serves to protect the fast-cure curing agent from atmospheric degradation. Alternative embodiments of the invention are depicted in Figures 3, 4 and 5 of the drawing. Figure 4 depicts an alternative embodiment in which one strip (B) comprises the epoxy resin, while the other comprises the room-temperature, fast-cure curing agent (A) and the polyamide resin curing composition (C) which serves to protect the roomtemperature, fast-cure curing agent from atmospheric degradation. In such form, the separate strips are carried on release paper or other carrier and packaged as a single unit.

Figure 5 of the drawing illustrates an embodiment in which curing agent A and epoxy resin B are each wrapped or enveloped by the polyamide curing composition C. This may be accomplished by extrusion of the materials, or, alternatively, bands A and B could be placed in a bath of molten polyamide curing composition from which the curing composition C will adhere to bands A and B in the form depicted in Figure 5. In this embodiment as well as those illustrated in the other Figures, it will be appreciated that the curing composition C functions in a manner analogous to a container, and is unique in this role, since it becomes part of and is consumed with use of the adhesive sealant, and yet does not have to be removed or segregated from the adhesive-seaiant prior to use.

Figures 1 and 3 of the drawings illustrate a method of sealing ends of the epoxy tape before and after removal of portions of the tape for use as an epoxy adhesive sealant so as to maintain the protective shield about the air-sensitive, room temperature, fast-cure curing agent.

The room-temperature curing agent, whether in the form of polyamide, polymercaptan and/or aminophenol should be present in an amount sufficient to crosslink from about 80 to about 120%, preferably about 100%, of the available cross-linking sites of the epoxy resin in the tape.

As mentioned, the epoxy resin and the curing agent therefore are admixed with various fillers, plasticizers, and colorants to form the putty-like compositions which are extruded into separate shapes or into an epoxy tape of the type described in U.S. Patent No. 3,837,981. Useful fillers for this purpose include talc, powdered alumina and asbestos fiber. Fillers such as these provide the epoxy resin and the curing agent compositions with physical properties and the putty-like consistency necessary for extrusion into tape form. The fillers are incorporated into the epoxy resin and the curing agent compositions in amounts sufficient to produce a putty-like mass which can be easily extruded into the desired epoxy tape.Powdered talc such as Mistron Vapor, available commercially from United Sierra Division of Cypress Mines Corporation, is an especially preferred filler, since it yields a handleable putty like mass with both epoxy resins and the curing agent compositions. Putty-like products prepared with this filler show less tendency to stick to the hands than do compositions prepared with other fillers. Useful plasticizers include resinous polyols and other agents which serve to yield a more flexible cured product.

A variety of coloring agents may be included in the epoxy or the curing agent compositions as desired. Useful coloring agents include pigments like titanium dioxide which provides a white color; carbon black for black color and various organic and inorganic pigments for other colors. It is desirable that the respective bands of epoxy resin and curing agent composition be of contrasting color to serve as an indicator of complete and thorough mixing.

To use the room-temperature, fast-cure products of this invention, a portion of the tape comprising substantially equal lengths of the epoxy resin band and the curing agent band is selected and the compositions are mixed together. The mixing may be accomplished by hand or with the aid of mechanical assistance. Mixing permits the components, i.e. the epoxy resin and the roomtemperature fast-cure curing agent, to react and effect curing, in situ. When the epoxy resin and the room-temperature fast-cure curing agent bands of the tape are of contrasting color, it is easy to determine when a uniform mixture has been obtained simply by continuing mixing until the mixture has a uniform color. It will be appreciated that pigment may be included in one or both bands of the composition.

The overall extrusion process for preparing the products of this invention may be carried out in a manner analogous to that described in U.S. Patent No. 3,837,981. In this process, the respective putty-like compositions may be extruded from three extruders which lay down the respective bands illustrated in Figures 2 and 4. After extrusion, any desired length of the tape may be simply roiled up and packaged in any desired manner. There is no need for special packaging requirements to give a useful shelf life to the tape.

When the epoxy tape of this invention is used to an adhesive sealant, any desired quantity of the epoxy tape made of approximately equal length of.

each band in the tape is selected and kneaded together under ambient conditions forming a uniform mixture. The resulting putty-like or doughlike epoxy adhesive sealant has a relatively short pot life and must be applied rather promptly as substantial curing is effected at ambient temperatures within about ten minutes from the time when the epoxy resin composition and the room-temperature fast-cure curing composition are combined to form a substantially uniform mixture. There must be some time after mixing by hand in which the product remains workable for each application. Accordingly, the product is preferably formulated so that substantial curing to the point of unworkability by hand occurs within about 5 minutes from the time of mixing. This point can be characterized by a Durometer hardness (Shore A) of 30.The product reaches a Shoro A of 60 within 10 minutes from time of mixing, and thus is an extremely rapid, room temperature curing adhesive sealant.

Mixtures formed from epoxy tape according to this invention substantially cure within ten minutes or less from the time of initial mixing to a useful, tough, solid, epoxy adhesive. The epoxy adhesive formed from the epoxy tape has excellent adhesive-sealant properties, and may be utilized to adhere ceramic, wood and metal and like materials to aluminum, concrete, steel, ceramic and like substances. The epoxy composition will cure under water making it useful in many marine environments.

The invention is illustrated in the following Examples, in which parts are by weight.

EXAMPLE 471 parts of an epoxy resin (Epon 828) having an epoxy equivalent weight of 185 to 192 are mixed with 525 parts of powdered talc (Mistron Vapour by United Sierra Division of Cypress Mines Coporation) forming a highly viscous, smooth material.

A curing agent composition is prepared by mixing 17 parts of a semi-solid polyamide resin having a amine value of 90 and a viscosity of 10 poises at 1 500 C. (Versamid 100 of General Mills) with 30 parts of a liquid polyamide resin having an amine value of 200 to 300 (Azamic;e 21 5 of AZ Chemicals, Inc.) and with 60 parts of powdered talc (Mistron Vapor) in a sigma blade mixer maintained at a temperature not exceeding 500C until a uniform mixture is formed.A third mixture is prepared by mixing 30 parts of a semi-solid polyamide resin having an amine value of 90 and a viscosity of 10 poises at 1 500C (Versamid 100), with 48 parts of liquid polymercaptan polymer having a mercaptan value of 3.6 milli-equivalents per gram (Capcure of Diamond Shamrock), 8 parts of aminophenol (DMP 10 of Rohm 8 Haas) and 100-parts of powdered talc (Mistron Vapor) in a double arm putty mixer maintained at a temperature not exceeding 500C until a uniform mixture is formed. Substantially equal portions, by weight, of each of the three mixtures are formed into slugs and fed separately into extruders which simultaneously lay down bands of each mixture in an appropriate form, e.g. in a form similar to that depicted in any of Figures 2 to 5 of the accompanying drawing. A room temperature fast curing epoxy adhesive is formed which substantially cures to Shore A hardness of about 30 within 5 minutes after initial mixing.

Claims

1. A putty-like, room-temperature, fast-cure adhesive sealant comprising a first band of an uncured reactive polymer or resin adhesive sealant composition and a second band comprising a composition capable of polymerizing or curing the uncured reactive polymer or resin composition when the first and second bands are combined to form a substantially uniform mixture, wherein the second band comprises an agent capable of polymerizing or curing the uncured reactive polymer or resin to a hard adhesive sealant within about ten minutes from the time when the uncured reactive polymer or resin composition and the curing composition are combined to form a substantially uniform mixture.

2. An adhesive sealant as claimed in claim 1 wherein the polymerizing or curing agent is capable of polymerizing or curing the uncured reactive polymer or resin to an adhesive sealant having a Shore A hardness of about 30 or more within five minutes.

3. An adhesive sealant as claimed in claim 1 wherein the polymerizing or curing agent is capable of polymerizing or curing the uncured reactive polymer or resin to an adhesive sealant having a Shore A hardness of about 60 or more within ten minutes.

4. An adhesive sealant as claimed in any of claims 1 to 3 wherein the second band and/or the sealant as a whole is enveloped in an outer surrounding wrap of a composition capable of protecting the fast-cure curing agent from premature reaction with the uncured reactive polymer or resin.

5. An adhesive sealant as claimed in any of claims 1 to 4, wherein the uncured reactive polymer or resin is an uncured epoxy resin.

6. A putty-like epoxy adhesive sealant comprising a first band of an uncured epoxy resin composition and a second band comprising a composition capable of curing the uncured epoxy resin when the first and second bands are combined to form a substantially uniform mixture, wherein the second band comprises a fast-cure curing agent capable of curing the uncured epoxy resin to a hard, adhesive sealant within about ten minutes from the time when the uncured epoxy resin composition and the curing composition are combined to form a substantially uniform mixture, enveloped by an outer surrounding wrap of a composition capable of protecting the fast-cure curing agent from premature reaction with the uncured epoxy resin.

7. An epoxy adhesive sealant as claimed in claim 6 wherein the fast-cure curing agent is capable of curing the uncured epoxy resin to an adhesive sealant having a Shore A hardness of at least about 30 within five minutes.

8. An epoxy adhesive sealant as claimed in claim 6 wherein the fast-cure curing agent is capable of curing the uncured epoxy resin to an adhesive sealant having a Shore A hardness of at least about 60 within ten minutes.

9. An epoxy adhesive sealant as claimed in any of claims 6 to 8 wherein the composition forming the outer surrounding wrap enveloping the fastcure curing agent is capable of curing the epoxy resin when it and the fast-cure curing agent are combined with the uncured epoxy resin to form a substantially uniform mixture.

10. An epoxy adhesive sealant as claimed in any of claims 6 to 9 wherein the composition forming the second band is capable of curing the uncured epoxy resin to a hard, adhesive sealant within from 5 to 10 minutes from the time when the uncured epoxy resin composition and the second band are combined to form a substantially uniform mixture.

11. An epoxy adhesive sealant as claimed in any of claims 6 to 10 wherein the fast-cure curing agent and the uncured epoxy resin are enveloped by an outer surrounding wrap of a composition capable of protecting the fast-cure curing agent and the uncured epoxy resin from premature reaction with the atmosphere and one another.

12. An epoxy adhesive sealant as claimed in any of claims 6 to 11 wherein the fast-cure curing agent comprises a polymercaptan having a mercaptan value of 1 to 20.

13. An epoxy adhesive sealant as claimed in claim 12 wherein the fast-cure curing agent includes an aminophenol in a weight ratio to the polymercaptan of from 1:5 to 1:20.

1 4. An epoxy adhesive sealant as claimed in any of claims 6 to 1 3 wherein the fast-cure curing agent is used in conjunction with one or more polyamide resins in a weight ratio of from 1:1 to 2:1.

1 5. An epoxy adhesive sealant as claimed in any of claims 6 to 14 wherein the outer surrounding wrap comprises a polyamide curing agent for the epoxy resin and has a thickness of from 0.5 to 2 mm.

1 6. An epoxy adhesive sealant substantially as hereinbefore described or illustrated with reference to any of Figures 1 to 5 of the accompanying drawings or exemplified in the foregoing Example.

1 7. A process for the manufacture of a puttylike epoxy adhesive sealant comprising forming a first putty-like composition comprising an uncured epoxy resin, forming a second putty-like composition comprising a fast-cure curing agent capable of curing the uncured epoxy resin to a hard adhesive sealant within about ten minutes from the time when the uncured epoxy resin is combined with the fast-cure curing agent to form a substantially uniform mixture, forming a third putty-like composition comprising a curing agent for the uncured epoxy resin but free from fast-cure curing agents therefor, and coextruding the first, second and third putty-like compositions to form a tape product in which the first composition constitutes a first band, the second composition constitutes a second band and the third composition constitutes an outer surrounding wrap for at least the second band.