CA2204398A1 - Epoxy ester vesicles and paints - Google Patents

Abstract

A new type of paucilamellar lipid vesicle having an epoxy ester as the primary wall material has been developed. This lipid vesicle can be used to encapsulate epoxides without leakage. These epoxide-containing vesicles are particularly useful in forming epoxy-latex polymer paints which are shelf stable and polymerize upon drying.

Description

CA 02204398 1997-0~-02 W O 96/14360 PCTnUS95/13877 EPOXY ESTER VESICLES AND PAlNTS

Background of the Invention The present invention concerns a new type of vesicles having an epoxy ester as the major wall component. These vesicles can be used in a variety of products but have particular usefulness in paints, coatings and adhesives. Using the vesicles of the invention, it is possible to have a water-based latex paint which hardens into a polymer when drying rather than merely an aggregated film. This latex paint is shelf stable in a single container and only polymerizes upon application and drying.

Epoxies have been used for many years in the adhesive and paint fields. Epoxies are all based on the epoxide ring, which has the following structure:
--c--c--This epoxide ring has bond angles which average sixty degrees (60~), considerably less than normal tetrahedral carbon angle of 109.5~, or the divalent oxygen angle of 1 10~.
This three membered ring is highly strained so the bonds open easily, causing the epoxide to have high reactivity. Epoxides can under go acid catalyzed reactions, base catalyzed cleavage, and a variety of other reactions. When an epoxide such as a bis-phenol epoxide is reacted with an acid bearing material such as carboxylic acid, it can polymerize and crosslink to form polymers. A f~mili~r form of epoxides is the two-part epoxy resin often used as an adhesive. In this two-part resin, the epoxide and hardener are both stable when kept separate but upon mixing, the polymerization reaction takes place and the epoxy readily hardens into a solid. Those who have worked with epoxies know the rapid speed and hard bond that can be formed with this process.

Latex paints have some advantageous properties as co...paled with the alkyd or oil based paints, particularly in terms of their water solubility and ease of clean up. However, this same water solubility can be a problem. For many intlll~tri~l applications, the fact that 30 the latex is water soluble is detriment~l since weathering or water under high force under ~ water can cause the latex to deteriorate. This is particularly important in covering metallic, as compared to wooden, structures since the latex can not form as strong a bond with the metal surface as it can with wood. In practice, the latex is painted or coated on to the surface and then allowed to dry, forming a film on the surface.
In order to ameliorate some of these latex problems, alle...~l~ have been made to create both water-based alkyd paints and epoxy-latex paints. The basic rationale of an epoxy-latex paint is to have the epoxy (or epoxide) act as a polym~ri7~tion agent, cross-linking the CA 02204398 1997 - 0~ - 02 P~T/JS 95/1 3877 -~- IPEA/IJS 3 1 MaY 19~6 acid functional groups in the late~ so that it forms a polymer coating as compared with a mere film. However. the mi.~;ture of the epo~ide polymerization agent and the late~ starts reacting almost immediately, so both phases cannot be stored in the same container. For certain applications, high-pressure spray mi~ers having mixing chambers are used to mix the 5 epoxide and latex and spray the combination product on the surface. The problem with these mi~ers is that there is always some reaction in the spray head so they clog over time. While the advantages of having a polymerized late~ are known, this product has not been easy to achieve.

Accordingly, an object of the invention is to provide a unitary product having both a latex paint and a hardener or polymerization agent which will form a latex polymer.

Another object of the invention is to provide vesicles having an epoxide delivery system.
A further object of the invention is to provide a method of forming a unitary product containing both latex and a polymerization agent.

These and other objects and features of the invention will be apparent from the 20 following description and the claims.

Summary of the Invention The present invention features lipid vesicles having an epoxy as the primary wall 25 material, preferably encapsulating an epoxide which can act as an hardener or polymerization agent. These vesicles have primary use in the paint field but also are advantageous in the manufacture and use of other polymers such as polyurethane, polyacrylics, and different types of coatings_ In its simplest form. the lipid vesicles of the invention have an epoxy ester as the primary lipid of the bilayer. For paint and other similar applications. the vesicles have an epo~ide enc~psulated therem. The epo~y ester wall is not reactive with the epo~ide and acts as a barrier against the release of the epo~ide. The preferred vesicles are paucilamellar vesicles which have an amorphous central cavity surrounded by ~-10 lipid bilayers. so that 3~ substantially all of the epo~cide (which is water immicible) is segreaated in that amorphous central cavity. The pret'erred epo~y esters are esters of C I ~-C~o fatty acids~ and mi~;tures thereof. Preferred epo~ides include those with a phenol derivative~ pret'erably his-phenol epo:~ide compounds. A secondary surfactant such as sodium lauryl sultate or ammonium lauryl sulfate helps to provide stability to the vesicles.

EN~E~ SH~

' CA 02204398 1997-0~-02 PCT/~S 9 5 / 1 3 8 ~ 7 ~ 3 ~ IPEAIIJS 3 1 MAY 1996 In another embodiment~ the epoxide containing lipid vesicles are used as a "hardener"
in a paint having a hardener and a paint base. Preferably, a lateY~ most preferably a lateY
being substantially free of ammonium ions~ is used as the paint. The use of ammonium ions 5 to neutralize the acid in the latex appears counterproductive because ammonia (in equilibrium with ammonium ions) can penetrate the vesicle membrane, allowing ammonium ions to react with the epoxide and inactivating the system during storage. Similarly~ although in some circumstances an ammonium lauryl sulfate could be used as the secondary surfactant in the vesicle, its use is contraindicated with a latex paint in the present system. The paint is shelf 10 stable~ and can be spread on a wall or other area, whereby the lateY and the hardener will combine, and react only upon drying. ~t is believed that the vesicles desiccate and fracture upon drying, thereby releasing the epoxide, which then reacts with the latex to form the latex polymer.

The same type of vesicle could be used in an adhesive system whereby the fracture of the vesicle allows one part of a two-part epoxide adhesive to mix with the other while segregating the components before mechanical stress or drying frees the reactants. This technique can also be with other polymerizable materials such as urethane monomers.

Detailed Description of the Invention The present invention provides both epoxy ester lipid vesicles as well as a paint or coating made therefrom. These epoxy ester lipid vesicles allow the formation of a unitary latex-epoxy paint, a paint which can be kept in a single container until use. It is only upon drying of the preparation and fracture of the vesicles that the polymerization reaction occur.

In the preferred embodiment of the invention, the vesicles are made of an epoxy ester resin solution, an epoxide, a secondary surfactant, a neutralizing agent (if necessary)~ an anti-foaming agent (if necessary), and deionized water. These vesicles are made using procedures similar to those described in United States Patent No. 4,911~928 and United States Patent No.
5.160~669, the disclosures of which are incorporated herein by reference. Briefly, the epoxy ester and the epoxide are heated together to flowability. e.g.. a temperature of appro~cimately 75~C. The aqueous phase, which contains water soluble materials such as the secondary surfactant~ e.g., sodium lauryl sulfate~ a neutralizing agent if needed such as ammonium 35 hydroxide or sodium hydroxide, and any anti-foaming agent~ all dissolved in deionized water~
is then heated to the temperature slightly below that of the epo~;y ester/epoxide phase. The phases are blended using a shear mixing device such as the NovaMi.YTM lipid vesicle maker from IGI, Inc. or a homogenizer until a vesicular product with a thin~ lotion-like consistency AMENDED S~!EE~

CA 02204398 1997-0~-02 -~- lP~Al~JS 311~rlAY1996 is achieved. The vesicular product can then be stored as is or mixed with a paint or other material.

The following reaction sequence is believed to generate the polymer. Specifically~ the 5 bis-phenol epoxide. formed by the reaction of a bis-phenol with epoxides: reacts with the carboxylic acid of the latex, releasing a phenol epoxide, and form.mg the polymer. This polymer hardens rapidly, forming an exceptionally hard coating on the surface.

HO~C~Oi l + ~ ( H~C-CH-CH

H~ C- CH-CH ~ ~ C~ O- C H ~CH - CH ~
o R--C--OH

8 OH ~ f ,~, , ~ ( 3 ) R--C--O~ C-CHCH--O~C~O-CH~CH-CH~

The following examples will more clearly illustrate the eff~cacy and advantageous properties of the invention and its various embodiments.

Example I

In this example, epoxy ester vesicles were made and then mixed with an off-the-shelf latex paint to see whether it is possible to make the paint combination of the present invention. The la~x has carboxylic acid functional groups and is neutralized with ammonium hydroxide. Ammonium lauryl sulfate was used as the secondary surfactant in ~0 making the vesicles. Table I shows the formulation used in manufacture of the vesicles.

~P~EN~)~D SH~F. ~

IPEA~JS 3 1 MAY 199~

Epoxy Ester Resin Solution 10.0 (0~7-1250 Cargill~ Inc.) Epoxide ~2.0 (Araldite GY6010, Ciba-Geigy Corp.) Ammonium Lauryl Sulfate, 30% 3.3 (ALS Carsonol, Lonza) Ammonium Hydroxide 0.3 Deionized Water 34.4 The epoxy ester and epoxide were blended together and heated to approximately 20 75~C. forming the lipophilic phase. The epoxide used has the following general formulation:

CH2--CHCH20~ O--OcH2cHcH2o--O--C~--OCH2CH--CH2 (A) The ammonium lauryl sulfate, ammonium hydroxide and water were heated to 70~C, forming 25 the aqueous phas~ A laboratory size homogenizer was lowered into the aqueous phase and while homogenizing, the lipid phase was added to the aqueous phase. The combination was mixed for ten minutes. yielding a product with a temperature of about 69~C~ having a thin, lotion-like consistency and a pH of 8.0-8.~. Microscopic examination showed heterogeneous size vesicles with no unblended epoxy-ester lipid phase. No separation of phases occurred 30 upon centrifugation at 3500 RPM for ten minutes.

The epoxy vesicles were then blended with Maincote AE-~8 (Rohm and Hass)~ a commercial late~ paint. The proportions were one part vesicles to two. three or tour parts latex paint. The mixtures were placed in closed containers and kept at ~0~C for observation.
3~

~MENDED SHEET

On the tenth day, all three lllixluleS began to solidify. The mix~u~es were heated in a water bath to 90~C, which caused the latex and epoxide to react, yielding a solid within five mimltes. The 90~C bath reliquifies the epoxy ester of the vesicle walls, releasing all the epoxide.

lt was hypothesi7~d that the ammonium ion reacted with the epoxide (a classic epoxide base reaction), causing the solidification process. Since the Maincote AE-58 is an ammonium hydroxide neutralized latex and ammonium lauryl sulfate was used in thevesicles, additional ~xll~filllents using a ammonium-free ~r~p~alion were conducted.
Fx~n~le 2 This example illustrates an early ~ fill,ent using an ammonium-free plepaldlion.Table 2 shows the formulation used in making the vesicles.

% wlw Epoxy Ester Resin Solution 10.0 (057-1250 Cargill, Inc.) Epoxide 52.0 (Araldite GY6010, Ciba-Geigy Corp.) Sodium Lauryl Sulfate 1.0 Deionized Water 37.0 This same procedure was used as in Example 1 to make the vesicles except that, because after five minlltes of homogenization a great deal of foam resulted, 2 ml of Silicone Medical Anti-Foam (Dow Corning) was added. The solution was then homogenized an additional five minutes.

The te~ ,ldLu~e after homogenization was a~lo~il.lately 60~C and microscopic tion again showed heterogeneous vesicles. Centrifugation showed no separation offree epoxy.

CA 02204398 1997-0~-02 PGTNS 9 5 1 1 3 ~ 7 7 - 7 - IPEWS 3 1 MAY 19~6 The vesicles were then blended with one-four parts of an acid functional latex, not neutralized~ ~vith a pH of 6.2 (obtained from the Sherwin-Williams Company). Thecombined product was stored in closed containers and kept at 50~C. Solidification did not commence occurring until 16 days after formation, showing that the ammonium ion was a S contributory factor in solidification.

Example 3 In this example, the vesicles described in Example 2 were used except they were 10 checked for pH and adjusted prior to addition to the latex. When the vesicular pH was found to be 7.1, IN NaOH was added until a pH of 7.8 was achieved.

The same latex was used as in Example 2, except it also was neutralized with I NNaOH to reach a pH of 7Ø Table 3 shows the proportions of epoxy vesicles and sodium 15 neutralized latex used in this experiment, as well as the resulting pH of each preparation.

Epoxy Vesicles Latex pH
I part 0.5 part 7.4 I part I part 7.2 I part 2 part 7.2 I part 3 part 7.2 I part 4 part 7.2 The mixtures were placed in closed containers and kept at 50~C as described in the previous two examples. At the end of four weeks (28 days). none of the samples had solidified in the containers. When painted onto a test wall~ the combination dried properly, yielding a hard paint coating which contrasted favorably with not just the standard latex but 35 also latex epoxy blends.

Similar uses of the epoxy vesicles could be made with other materials such adhesives, polyurethanes. and other coating materials. For example. urethane monomers or styrene monomers can react with the epoxide to form a hard epoxide co-polymer.

AMENDED SHE~T

-W Og6/14360 PCTrUS95/13877 Those skilled in the arts may d ~ --;--e other uses for the vesicles. Such other uses are deemed to be encomr~s~ed in the following claims.

5 What is claimed is:

Claims (19)

1. A paucilamellar lipid vesicle having 2-10 bilayers surrounding an amorphous central cavity comprising an epoxy ester as the primary wall material.

2. The lipid vesicle of claim 1 with an epoxide encapsulated therein.

3. The lipid vesicle of claim 2 wherein said epoxy ester is selected from the group consisting of C12-C20 fatty acid esters, and mixtures thereof, containing an epoxide group.

4. The lipid vesicle of claim 2 wherein said epoxide comprises a phenol derivative.

5. The lipid vesicle of claim 1 wherein said lipid vesicle further comprises a secondary surfactant.

6. The lipid vesicle of claim 5 wherein said secondary surfactant is selected from the group consisting of sodium lauryl sulfate and ammonium lauryl sulfate.

7. The lipid vesicle of claim 2 wherein substantially all of said epoxide is segregated in said amorphous central cavity.

8. A paint containing a hardener and a latex paint base, said hardener including a lipid vesicle encapsulating an epoxide and comprising a C12-C20 epoxy ester as a primary wall material of said vesicle, and said latex paint base contains free carboxylic acid functional groups; wherein said epoxide can react with said latex paint base to form a polymer.

9. The paint of claim 8 wherein said epoxy ester is selected from the group consisting of C12-C20 fatty acid esters, and mixtures thereof, containing an epoxide group.

10. The paint of claim 8 wherein said epoxide comprises a phenol derivative.

11. The paint of claim 8 wherein said lipid vesicle further comprises a surfactant.

12. The paint of claim 11 wherein said secondary surfactant is selected from the group consisting of sodium lauryl sulfate, other non-ammonium lauryl sulfates, and mixtures thereof.

13. The paint of claim 8 wherein said lipid vesicle comprises a paucilamellar lipid vesicle having 2-10 bilayers surrounding an amorphous central cavity.

14. The lipid vesicle of claim 13 wherein substantially all of said epoxide is segregated in said amorphous central cavity.

15. The paint of claim 8 wherein said paint base comprises a latex paint.

16. The paint of claim 15 wherein said paint is substantially free of ammonium ions.

17. The paint of claim 15 wherein said latex and said hardener are shelf-stable when combined and only react upon drying.

18. The paint of claim 15 wherein said latex and said hardener polymerize upon reaction.

19. The paint of claim 8, wherein said epoxide comprises a bisphenol epoxide.