GB2172598A - Compositions comprising polymer and remaining flexible when cured - Google Patents

Abstract

The invention concerns compositions which remain flexible when cured comprising (i) low Tg polymer containing pendant unsaturation; (ii) polyfunctional mercaptan; and (iii) vanadium compound. Optionally, a beta-diketone compound may also be included. The compositions, which can be cured by exposure to air and become tack-free rapidly, are especially suitable for roof mastics, coatings, and caulks.

Description

SPECIFICATION Compositions comprising polymer and remaining flexible when cured This invention concerns compositions which remain flexible when cured and which are suitable for use as mastic, coating, and caulk compositions.

Mastics, coatings, and caulk compositions which are designed to remain flexible when cured usually require long periods of time to achieve tack-free properties. This is a problem in many applications; for example, with roof mastics which coat a roof which has previously been coated with a foam, the workers cannot walk on the roof until it becomes tack-free. Although non-flexible, quick tack-free compositions have been provided by others, no one has provided a flexible composition of low Tg which becomes tack-free upon exposure to air as is provided by the present invention. More specifically, others have provided flexible low Tg early tack-free compositions based either on aqueous emulsions, solvent solutions of cured polymers, moisture-cure systems, or reactive systems. The aqueous systems are disadvantageous in that they will not cure well under low temperatures or high humidity.Solvent solutions of cured polymers are disadvantageous in that a large quantity of solvent is used and all of it must evaporate for the system to function. The loss of the solvent is expensive and causes pollution. Moisture-cure systems are disadvantageous in that they are slow and do not cure well under dry conditions. Reactive systems which are two-part compositions are disadvantageous in that they must be mixed and applied shortly after mixing, and that they cannot be stored for a long time after mixing.

German Offenlegungsschrift No. 2,025410, published December 9, 1971, shows compositions comprising unsaturated polyesters which are crosslinked with monounsaturated monomer such as styrene in the presence of an accelerator system comprised of a vanadium compound and thioglycolic ester of at least trihydryic polyols. The composition is said to cure and dry more rapidly than with the use of monohydric thioglycolates, giving tack-free surfaces after complete hardening. At least 20 parts monomer per 80 parts unsaturated polyester is required, and no low Tg polymers which are flexible on cure are taught.

Hofer et al U.S.-A-3,516,976 shows vinyl monomers which are acrylic acid esters or methacrylic acid esters, for example, methyl acrylate or methylmethacrylate, polymerized by a redox system comprised of an organic vanadium compound and a linear aliphatic primary mercaptan.

Kehr U.S.-A-3,662.023 and 3,697 show liquid polyenes having at least two terminal unsaturated groups and a polythiol having multiple pendant or terminal SH groups which crosslinks or cures the polyenes to solid resins or elastomers.

Other prior art which has been considered but is thought to be less relevant are GER DT 1,912,426 (Rohm GmbH); U.S.-A-3,333,021 (Electrochemische Werke); Japanese 71/38710 (Johoku); DL 121,524 (Waibunger University); EP34,118 (Ceiba Geigy); and U.S.-A-4,120,721 (W. R. Grace).

By practice of the present invention there may be provided one or more of the following: (i) soft flexible polymer compositions which become substantially tack-free within a short time at ambient conditions; (ii) elastomeric coatings, caulks, and sealant compositions which are soft, have a low Tg, and cure under a,bient conditions to obtain a flexible film substantially free from tackiness; and (iii) stable one package compositions which form flexible films which cure upon exposure to ambient air and become tack-free quickly.

According to the present invention there is provided a composition which remains flexible when cured comprising: (i) polymer having a backbone formed from one or more monomers selected from: acrylic and methacrylic esters, acids and nitriles; styrenes; vinyl halides; vinyl acetate; and butadienes; said polymer containing pendant unsaturation and having a Tg belowO C.; (ii) at least 0.3, e.g. from 0.3 to 5, equivalents of polyfunctional mercaptan per equivalent of unsaturation in said composition; and (iii) vanadium compound providing 0.001 to 0.15% by weight vanadium.

The present invention also provides a coating, mastic or caulk having low tack, comprising a composition according to the invention which has been cured by exposure to air and which has a Tg below 000.

The compositions of the invention may be used as elastomeric coatings, for example, roof coatings, caulks, sealants, and mastics as well as in other areas where a soft, low Tg polymer which remains flexible on cure and cures relatively quickly to become free from tackiness upon exposure to ambient conditions is required.

The low Tg polymers should have molecular weights, Mn, of about 10,000 to 100,000.

The polymers used in the composition contain pendant unsaturation and have a Tg below 000., preferably about -80"C to about -20 C. The pendant uhsaturation can be provided either by copolymerization of suitable monomers that result in pendant unsaturated groups, or by post reaction of copolymers with suitable compounds to achieve the pendant unsaturation.

Suitable pendant unsaturated groups include acrylates, methacrylates, allylethers, allylesters, vinyl ketones, styrenes, or unsaturated fatty acid derivatives. Especially suitable pendant unsaturated groups are fatty acid drying oils or derivatives thereof, allylethers, allylesters, or (meth)acrylates.

Suitable unsaturated fatty acid derivatives include, but are not limited to, derivatives of natural fats or oils such as soybean oil, sunflower oil, hemp oil, linseed oil, tung oil, corn oil, cottonseed oil, safflower oil, and oiticica oil. Linseed and tung oil derivatives are most preferred.

Suitable monomers used to form the backbone of the low Tg polymer are acrylic or methacrylic esters, acids or nitriles; styrenes; vinyl halides or acetate; and butadienes. The most preferred backbone monomers are butyl acrylate, acrylonitrile, acrylic acid, 2-ethyl-hexyl acrylate, isobutyl acrylate, isodecyl methacrylate, lauryl methacrylate, tridecyl methacrylate, hydroxyethyl methacrylate, and hydroxyethyl acrylate.

In one embodiment of the invention the low Tg polymer is a copolymer, a major portion of which is formed from butyl acrylate, and wherein said copolymer contains pendant fatty acid groups.

The low polymer should have about 1 to 20 weight percent pendant unsaturation. Preferably such polymers do not have unsaturation in the backbones.

Based on equivalents of unsaturation in the composition, at least 0.3 equivalents of polyfunctional mercaptan are present in the composition of the invention. Preferably, 0.3 to 5 equivalents, and more preferably up to about 3 equivalents, are present since large excesses of mercaptan above 3 equivalents do not add to, and sometimes reduce, properties.Suitable polyfunctional mercaptans are trimethylolethane tri(3-mercaptopropionate); trimethylolpropane tri(3-mercaptopropionate); pentaerythritol tetra(3mercaptoproprionate); dipentaerythritol hexa(3-mercaptopropionate); glycol di(3-mercaptopropionates); trimethylolethane trimercaptoacetate; trimethylolpropane trimercaptoacetate; pentaerythritol tetramercaptoacetate; dipentaerythritol hexamercaptoacetate; glycol dimercaptopropionates; 2,2'-dimercaptodiethyl ether; trivinylcyclohexyl polymercaptan; and 2,5-dimercapto-1 ,3,4-thiadiazole.

Based on the weight of the total composition, 0.001 to 0.15 percent by weight vanadium is provided by the presence of vanadium compound, which is preferably one or more of vanadyl acetylacetonate, vanadium trisacetylacetonate, vanadium chlorides, vanadium sulfates, vanadium alcoholates, and vanadium complexes of organic acids.

The compositions of the invention may be rendered more stable by the presence of about 2 to 10 equivalents of beta-diketone-containing compound per equivalent of vanadium. Suitable beta-diketones include 2,4-pentanedione; 1,1 ,1-trifluoro-2,4-pentanedione; 1,1,1 -5,5,5-hexafluoro-2,-4- pentanedione; 2,4hexanedione; 2,4-heptanedione; 5-methyl-2,4-hexanedione; 2,4-octanedione; 5,5-dimethyl-2, 4hexanedione; 3-ethyl-2,4pentanedione; 2,4-decanedione; 2,2-dimethyl-3, 5-nonanedione; 3-methyl-2,4pentanedione; 2,4-tridecanedione; 1 -cyclohexyl-1 ,3-butanedione; 5,5-dimethyl-1 ,3-cyclohexanedione; 1,3cyclohexanedione; 1-phenyl-1 ,3-butanedione;I (4-biphenyl)-1,3-butanedione; 1 -phenyl-1 ,3-pentanedione; 3-benzyl-2,4-pentanedione; 1 -phenyl-5,5-dimethyl-2, 4hexanedione; 1-phenyl-2-butyl-1, 3-butanedione); 1 -phenyl-3-(2-methoxyphenyl)-1 ,3-propanedione; 1 -(4-nitrophenyl)-1 ,3-butanedione; 1 -(2-fu ryl)-1 3- butanedione; 1 -(tetrahydro-24uryl)-1 3-butanedione; and dibenzoylmethane. The presence of a betadiketone-containing compound is especialiy useful for preserving the shelf life.

It has been found that, by packaging the composition in an air-free container, long shelf life can be achieved and the composition can be ready for application as a coating, mastic, sealant, etc. by merely applying it, usually outdoors, under ambient conditions. Upon exposure to air, even cold air, the compositions cure to flexible materials which become tack-free within a relatively short period of time, usually in 18 to 48 hours. In prior known systems, tack-free times of weeks to months were usually required.

Small amounts of unsaturated monomers and oligomers (low molecular weight polymers) can be included in the compositions without detrimental effect, although the use thereof is not preferred. For example, less than 20% by weight of unsaturated monomer and/or up to 20% by weight of oligomer having a molecular weight, Mw, of less than 5000 may be included in the compositions of the invention.

Other preferred optional additives include pigments, solvents, rheology modifiers, mildewcides, and adhesion promoters, e.g. as are normaily used in flexible coatings, mastics, or caulks. When the composition of the invention is used in the form of a roof mastic, it may, for example, include one or more of organic solvent, pigment and rheology modifier.

The present invention will now be further illustrated by way of the following examples which are presented solely to illustrate the invention, and should not be considered to constitute limitations on the scope of the invention. In the examples all parts and percentages are by weight unless otherwise specified and the abbreviation "RSH" is used as a general designation to represent the mercaptan.

EXAMPLES Examples A-D The following unsaturated polymer solutions were prepared for use in Examples 1-40.

A) A copolymer of composition 96% butyl acrylate (BA)/2.5% acrylonitrile (AN)/1.5% acrylic acid (AA) esterified with 4.7% (based on polymer weight) of the methylhydroxyethylamide of linseed oil fatty acid (MHELA) in xylene to produce an 83% (solids content) polymer solution with pendant unsaturated fatty acid drying oil functionality.

B) A copolymer of composition 91% BA/9.0% hydroxyethyl methacrylate reacted with 2.3% (based on polymer weight) isocyanatoethyl methacrylate in xylene to produce an 83% (solids content) polymer solution with pendant methacrylate functionality.

C) A copolymer of composition 92.5% BA/2.5% AN/5.0% AA reacted with 1.7% (based on polymer weight) allyl glycidyl ether in xylene to produce a 53% (solids content) polymer solution with pendant allyl functionality.

D. A copolymer composition like that of polymer solution A except reacted wth 2.0% MHELA instead of 4.7% MHELA.

Example 1 About 100 g of polymer solution A and 7.0 g of trimethylolpropane tris(3-mercaptopropionate) (TM PTM P), mixed with 2.4 g of a 10 wt% solution of vanadyl triisopropylate in butyl cellosolve, is applied to an aluminum substrate as an 0.2 cm (0.08 inch) thick wet film. After 20 hours, the film shows reduced tack and does not crack when bent 180 degrees at -35 C.

Example 2 Example 1 is repeated except that polymer solution B is used in place of polymer solution A. The resultant film shows reduced tack after 44 hours and does not crack when bent 180 degrees at -30 C.

Example 3 Example 1 is repeated except that polymer solution C is used in place of polymer solution A. The resultant film shows reduced tack after 20 hours and does not crack when bent 180 degrees at -30 C.

Example 4 Example 1 is repeated except that polymer solution D as used in place of polymer solution A. The resultant film shows reduced tack and is flexible at low temperatures.

Examples S12 Table 1 shows the tack and flexibility of films prepared by the procedure in Example 1. The amounts of TMPTMP and the vanadium source vary as indicated. The vanadium level is approximately 0.05 wt% (vanadium metal based on polymer weight). These examples show the effect of varying the RSH:double bond ratio.

TABLE 1 RSH: Tack Vanadian double bond After Flexibility Ex. TMPTMP Source Ratio 20hrs at -300C 5 7.0g VO(C3H7)3 2.5 fair+ pass 1800 bend 6 3.5g Vo(C3Fi7)3 1.3 fair pass 1800 bend 7 2.0g VO(C3147)3 0.71 fair- pass 1800 bend 8 2.lg VO(acac)2 0.76 poor+ pass 1800 bend 9 2.0g VO(acac)2 0.75 fair- pass 1800 bend 10 3.09 VO(acac)2 1.2 fair pass 1800 bend 11 4.0g VO(acac)2 1.5 fair pass 1800 bend 12 5.0g VO(acac)2 1.9 fair+ pass 1800 bend Examples 73-19 Table 2 shows the tack and flexibility of films prepared as in Example 1 except substituting pentaerythritol tetra(3-mercaptopropionate) (PETMP) for TMPTMP. These examples show that addition of small amounts of monomers (such as trimethylolpropane trimethacrylate (TMPTM) and methyl methacrylate (MMA)) do not affect the resultant films as long as the mercaptan ievel is increased to maintain the RSH:double bond ratio close to 1. Approximately 0.06 wt% vanadium is used (added as V(acac)3).

TABLE 2 RSH: Tack double bond After Flexibility Ex. Monomer PETMP Ratio 20hrs at -300C 13 - 2.6g 1.0 fair pass 1800 bend 14 2.7g TMPTM 2.8g 0.50 poor+ pass 1800 bend 15 3.2g MMA 3.2g 0A9 poor+ pass 1800 bend 16 - 4.9g 1.9 fair+ pass 1800 bend 17 1.0gMMA 4.9g 1.3 fair+ pass 1800 bend 18 3.4g TMPTM 4.9g 0.78 fair- pass 1800 bend Comparative Examples 1821 Table 3 shows the tack and flexibility of films prepared with compositions containing known free radical initiating agents such as cumene hydroperoxide (CHP), cobalt naphthenate-6% cobalt (CoNap), and dimethylaminobenzaldehyde (DMABA).The films were prepared by the procedure of Example 1 using 100 g of polymer solution A but without TMPTMP or vanadyl triisopropylate.

TABLE 3 Tack After Flexibility Ex. CHP CoNap DMABA PETMP 20 hrs at -35 C 19 1.6g 1.0g - 4.0g poor pass 1800 bend 20 1.69 1.0g 1.0g 4.0g poor pass 1800 bend 21 1.6g 1.0g - - poor pass 1800 bend Comparative Example 22 About 1 00g of polymer solution A was mixed with 4.0 grams of PETMP. The resultant film, prepared by the procedure of Example 1, is flexible at -35 C, but without vanadium present, the cured film remains tacky.

Examples 23-24 and Comparative Example 25 Approximately 80g of polymer solution A, 3.5g of TMPTMP and a weight of a vanadium compound adjusted to give about 0.08 wt% vanadium was mixed with 10g of butyl cellosolve. Table 4 indicates the tack and flexibility of the resultant films prepared by the procedure of Example 1, as well as the stability (as demonstrated by viscosity change) of the compositions during 4 weeks in an air-tight container at 500C.

TABLE 4 Tack Vanadian After Flexibility Viscosity (a) Ex. Source 20 Hrs. at -300C Initial 2Wks 4Wks 23 VO(acac)2 fair pass 180 bend 18. 19. 19.(ls) 24 V(acac)3 fair pass 180 bend 16. 16. 17.(ls) Comp. Ex.

25 VO(C3H7)3 fair pass 180 bend 19.(s) 22.(s) 23.(s) (a) Viscosity in centipoise X 0.001 (=Pa s).

(s) means a skin formed on the surface.

(1 s) means a light skin formed on the surface.

Example 26 A formulated elastomeric coating was prepared as follows: 120 g polymer solution A 124 g xylene 1009 silica pigment 3.0 g rheological additive (based on castor oil) 27 g TiO2 pigment 0.4 g V(acac)3 3.0g PETMP Films of this composition, prepared by the procedure of Example 1, show reduced tack after 20 hours and can be bent 180 degrees at -35"C without cracking. See Table 5.

Comparative Examples 27-31 Table 5 shows the results of films prepared using the procedure of Example 1 prepared from compositions similar to the composition of Example 26 but without PETMP and V(acac)3. Common oxidative cure catalysts, such as cobalt naphthenate-6% cobalt (CoNap), and zinc naphthenate-8% zinc (ZnNap), as well as PETMP or V(acac)3 have been added separately as indicated. Without vanadium, whether or not mercaptan or oxidative cure catalysts or both are present, the films are tacky even after exposure to ambient extrior ultraviolet radiation.

TABLE 5 WEIGHT OF ADDITIVES (g) Tack After 20 Hrs Flexibility Ex. PETMP V(acac)3 CoNap ZnNap INTERIOR EXTERIOR at -350C 26 3.0 0.4 - - good- good pass 1800 bend Comp Ex 27 - - - - vpoor vpoor pass 1800 bend 28 - - 0.15 0.74 poor poor pass 1800 bend 29 - 0.4 - - vpoor vpoor pass 1800 bend 30 3.0 - - - vpoor vpoor pass 1800 bend 31 3.0 - 0.15 0.74 poor poor pass 1800 bend Examples 32-35 Various amounts of 2,4-pentanedione (Acac) are added to the composition of Example 26. Table 6 shows the tack and flexibility of the films as well as the stability (as demonstrated by viscosity change) of the compositions placed in an air-tight container for 4 weeks at 50"C.

TABLE 6 Tack Added After Flexibility Viscosity (a) Ex. Acac 24 Hrs at -35 C Initial 2 wks 4 wks 32 0 vgood pass 1800 bend 117 133(s) 135(s) 33 0.45g v good pass 1800 bend 114 129 130(s) 34 0.88g vgood pass 180" bend 110 121 122 35 1.78g vgood- pass 1800 bend 102 120 120 (a) Viscosity in Krebb units measured on a Stormerviscometer.

(s) means a skin formed on the surface.

Example 36- Comparative A sealant formulation containing 2349.1 grams of calcium carbonate, 206.1 grams of rheological modifier (based on caster oil); 102.0 grams of TiO2; 2459.1 grams of Polymer Solution A, and 5.6 grams of methacryloxypropyl trimethoxysilane were tested for relative surface tack after 18 hours at 24"C (indoors).

Example 37- Comparative Example 36 was repeated except with the addition of 0.10 grams of Co Naphthenate (6% Co) and 0.5 grams of Zn Naphthenate (8% Zn).

Example 33- Comparative Example 36 was repeated except 4.2 grams of TMPTMP were added.

Example 39- Comparative Example 36 was repeated except 0.2 grams of V(acac)3 were added.

Example 40 Example 36 was repeated except, in accordance with the invention, 0.21 grams (V(acac)3 and 4.2 grams TMPTMP were added. The relative surface tack for Example 40 was very good whereas for each of the comparative sealants 36 through 39 the relative surface tack was poor.

The V(acac)3 was added as a 2% solution in Xylene.

Claims (14)

1. A composition which remains flexible when cured comprising: (i) polymer having a backbone formed from one or more monomers selected from: acrylic and methacrylic esters, acids and nitriles; styrenes; vinyl halides; vinyl acetate; and butadienes; said polymer containing pendant unsaturation and having a Tg below O"C; (ii) at least 0.3 equivalents of polyfunctional mercaptan per equivalent of unsaturation in said composition; and (iii) vanadium compound providing 0.001 to 0.15% by weight vanadium.

2. A composition as claimed in claim 1 wherein said pendant unsaturation is provided by groups formed from one or more of acrylates, methacrylates, allylethers, allyesters, vinyl ketones, styrenes, unsaturated fatty acid derivatives and fatty acid drying oils and derivatives thereof.

3. A composition as claimed in claim 1 wherein said polymer is a copolymer, a major portion of which is formed from butyl acrylate, and wherein said copolymer contains pendant fatty acid groups.

4. A composition as claimed in any of claims 1 to 3 wherein said polymer has a Tg of from -80"C to -20"C.

5. A composition as claimed in any of claims 1 to 4wherein said composition comprises up to 5 equivalents of polyfunctional mercaptan per equivalent of unsaturation.

6. A composition as claimed in any of claims 1 to 5 wherein said mercaptan is one or more of trimethylolethane tri(3-mercaptopropionate); trimethylolpropane tri(3-mercaptopropionate); pentaerythritol tetra-(3-mercaptoproprionate); dipentaerythritol hexa-(3-mercaptopropionate); glycol di (3mercaptopropionates); trimethylolethane trimercaptoacetate; trimethylolpropane trimercaptoacetate; pentaerythritol tetramercaptoacetate; dipentaerythritol hexamercaptoacetate; glycol dimercaptopropionates; 2,2'-dimercaptodiethyl ether; trivinylcyclohexyl polymercaptan; and 2,5-dimercapto-1,3,4-thiadiazole.

7. A composition as claimed in any of claims 1 to 6 wherein said vanadium compound is one or more of vanadyl acetylacetonate, vanadium trisacetylactonate, vanadium chlorides, vanadium sulfates, vanadium alcoholates, and vanadium complexes of organic acids.

8. A composition as claimed in any of claims 1 to 7,further including 2 to 10 equivalents of beta-diketone-containing compound per equivalent or vanadium.

9. A composition as claimed in any of claims 1 to 8 further including up to 20% by weight oligomer having a molecular weight, Mw, of less than 5000.

10. A composition as claimed in any of claims 1 to 9 wherein the composition contains less than 20% by weight of unsaturated monomer.

11. A composition as claimed in any of claims 1 to 10 which is in the form of a roof mastic and further includes one or more of organic solvent, pigment, and rheology modifier.

12. A composition as claimed in any of claims 1 to 11 which is contained in an air-free container and thereby has a long shelf-life.

13. A coating, mastic, or caulk having low tack comprising a composition as claimed in any of claims 1 to 10 which has been cured by exposure to air and which has a Tg below 0 C.

14. A composition as claimed in claim 1 substantially as described in any of the foregoing examples.