MXPA98003903A - Monomers of current epoxides cationically initiated thermally or by radiation of the reagent and compositions manufactured from these monome - Google Patents

Abstract

Styrene oxides curable cationically initiated thermally or by radiation from the structure. They are suitable for use in cationically curable coating compositions and adhesives

Description

CURED CAOONICALLY INITIATED CURRENT EPOXIDE MONOMERS THERMALLY OR BY RADIATION OF THE REAGENT AND COMPOSITIONS ELABORATED OF THESE MONOMEROS DESCRIPTION OF THE INVENTION This invention relates to cationically curable, radiation initiated or thermally curable epoxies and adhesives or coating compositions comprising these epoxides. UV-curing or electron-beam adhesives are currently the fastest growing segments on the market of radiation-cured polymers. Of particular commercial importance are UV-curable epoxide adhesive formulations, which typically consist of three major components: i) cationic photoinitiators, ii) alcohols or polyols, and iii) epoxide monomers. Photoinitiators are chemically inert compounds that release acidic species after exposure to actinic radiation. These acid species then catalyze the cross-linking of the epoxide monomers. Typical photoinitiators include diaryliodonium, triarylsulfonium and ferrocenium salts. Alternatively, it is possible to thermally initiate the cure through the use of those onium and pyridinium salts which are known to produce cationic species capable of initiating cationic cure after heating. By For example, it is known that N-benzylpyridinium and related quaternary ammonium salts produce acid species under thermolysis conditions (Lee, S.B., Takata, T., Endo, T., Macromolecules, 1991, 24, 2689-2693). It is also known that diaryliodonium salts are thermally decomposed in the presence of catalytic amounts of copper compounds (Crivello, J.V.; Lockhart, R.T.P .; Lee, J.L. J. Polym, Sci., Polym. Chem. Ed. 1983, 21, 97), and that these salts of Jjkt diaryliodonium can be converted to acid species via decomposition of benzpinacol (Abdul-Rasoul, F.A.M .; Ledwith, TO.; Yagci, Y. Polymer, 1978, 19, 12 | 9-1223), or peroxides (Crivello, J.V., Lam, J.H.W. Polym, Photom, 1982, 2, 219). A recent report indicates that N-allyloxypyridinium barns can be thermally converted to acidic species in the presence of 2, 2"-azobutyronitrile or benzoyl peroxide (Reetz, I, Bacak, V., Yagci, Y. Macromol, Chem. Phys. 1997, ^ 98, 19-28). Any of these routes will liberate cationic species capable of effecting ring-opening polymerization of the styrene oxides. The alcohols or polyols act as a source of active protons, whereby the conversion of the photoinitiator to cationic species is facilitated, which activates the cationic polymerization. They also provide flexibility and impact resistance to the formulation through the copolymerization with the epoxides.

# The epoxide monomers used in these formulations are mainly cycloaliphatic epoxides, although glycidyl esters, glycidyl ethers and epoxidized alpha olefins have also been used. Cycloaliphatic epoxides are the preferred compounds since they are more reactive than the linear chain aliphatic epoxides. It has been assumed that this increased reactivity is the result of two structural features: cleavage of either C-O bonds leading to the formation of a secondary carbocation relatively stable; and the cleavage of a C-O bond also liberates the ring chain associated with the fusion of the bicyclic ring. The most common epoxy resin in UV curable formulations is a bis-cyclohexene oxide (available from Union Carbide, product ERL-4221) linked by an ester group. This bis-cyclohexene oxide possesses sufficient reactivity to provide good cross-linking at room temperature. On the other hand, the ester group is the only other functionality present and is transparent to UV radiation. However, there are disadvantages for this monomer. The bis-epoxide is an inherently non-flexible material and consequently produces a weak cross-linked network. Such brittle materials are susceptible to mechanical pressures in manufacturing operations or end-use applications. To counteract this, the epoxide can be belt-tensioned with one or more flexible diols with the order to provide the necessary flexibility. However, cycloaliphatic epoxides are not compatible with a particularly large range of diols, which consequently limits the range of properties that can ultimately be achieved. Although Crivello, et al. (Radiation Curing in Polym Science and Technology, Vol.2, J.P. Fouassier and J.F. Rab (Eds), Elsevier Applied Science, New York, 1993, pp. 435-472 Macromolecules, 1996, 29, 433-438 and 439-445, J. Polym. Sci. Polym. Chem. 1995, 33, 1881-1890) has reported several epoxide structures (eg, epoxynorbornene and d-limonene oxide) that are said to solve some of the disadvantages of traditional cyclohexene oxides, there is a need for new monomers that are curable cationically and that avoid the problems of cycloaliphatic epoxide monomers. * Figure 1 is a trace of the DSC curves for tre Heloxi; and composition C contains divinylbenzene dioxide. This invention comprises the compounds cationically curable by radiation or thermally containing a portion of styrene oxide of the structure: wherein R1 independently represents hydrogen, or aliphatic, alicyclic or aromatic groups, which may contain heteroatoms, characterized in that they do not hinder the cationic polymerization of the epoxy functionality either through steric interaction or through the action of a base of Lewis; and is an integer from 1 to 6, w is an integer from 0 to 5, with the proviso that y + w =. 6. - Examples of representative styrene oxides, but not proposed as limitation, are those derived from styrene, isoeugenol, or cinnamyl alcohol, such as those having structures such as: In which n is the integer from 0 to 5 wherein R 'is -H, -OCH3, -0-C (0) CH3; III V E n which R is -OCH3, or -OC (O) CH3 The epoxidation can be carried out on the starting olefinic compound by any suitable method known in the art, but is preferably conducted through oxidation with potassium / acetone monopersulfate of the olefinic portion of the corresponding styrene. The styrene compound is suspended in a mixture of acetone and water, and buffered with sodium bicarbonate, which serves to prevent the decomposition of the resulting oxides. This suspension is then treated with an excess of the oxidant, provided as an ous solution of the monopersulfate compound (2KHS05KHS04K2 S04) (Oxone®, a product of Dupont). The recovered solution is fractionated with ethyl acetate, toluene, methylene chloride, or other suitable solvent. The development consists of washing the organic phase with water followed by drying with a non-acid drying agent (for example, anhydrous sodium bicarbonate). Filtering this mixture, ^ followed by removal of the organic solvent in vacuo, produces the desired epoxide in high yield without further purification. The resulting epoxides are stable indefinitely at room temperature, provided that no acid components are present. There are a number of advantages for this procedure. The process is not expensive and is suitable for large-scale operations. The reagents involved (ie Oxone® monopersulfate, acetone, sodium bicarbonate and acetate) Ethyl) are relatively harmless, and all these materials are not halogenated. No significant exothermic reactions (changes in temperature <10 ° C) are noted during the epoxidations, and it is believed that the reaction mixture is not inherently flammable. The process produces the product desired in high performance without a purification step; and the product obtained is of high purity (> 95% by XH NMR). The products obtained by this procedure demonstrate a low total chlorine content (<30 ppm), which makes them probably candidates for electronic applications.

Finally, the pH of the reaction and the development is essentially neutral, so premature promotion of the epoxide by adventitious acid is pre-included. This is a distinctive advantage over per acid epoxidations described in the literature, which generates by-products that cause degradation of styrene oxide products.

These styrene oxides are eminently suitable for use in cationically curable compositions initiated by radiation or thermally for various reasons. They are extremely reactive crosslinking agents, curing at room temperature, and polymerize more rapidly than analogous compositions containing cycloaliphatic epoxides. This faster curing speed implies faster processing speeds for end users, and the greater reactivity results in formulations that require decreased amounts of the monomer while providing identical proportions of supply and degrees of cure. For cycloaliphatic epoxides, such as those derived from cyclohexene oxide, and typical photoinitiators, it has been assumed that moisture may decrease the rate of cure by reacting with super-initiated starter species (e.g., HSbFs, which may be derived from Ar3S + SbF6, a typical photoinitiator) to form a hydronium and a counter ion. The hydronium ion is not acidic enough to react with the cycloaliphatic epoxide and continue crosslinking. In contrast, the epoxy functionality of the styrene oxide monomers is more readily ring opened to form the benzylic carbocation in the presence of either a super acid or a hydronium ion, and consequently the polymerization is continued and not terminated by the reaction of the species started with humidity. Additionally, life Prolonged useful benzyl carbocation allows curing to continue even after the actinic exposure has ended, and may allow curing in regions that are not directly exposed to actinic radiation, so-called dark curing. In addition, these monomers contain an aromatic chromophore that absorbs actinic energy at wavelengths other than the wavelengths that activate photoinitiators. This absorption promotes the monomers are in an excited state and result in increased reactivity. This aromatic benefit is not possible in cycloaliphatic epoxides, which do not possess chromophoric substituents. The improved reactivity of these monomers allows the formulation with a wide variety of alcohols or polyols, which may also contain other functionalities, leading to differentiated products and formulations. In addition to act as a source of active protons and therefore facilitate the conversion of the photoinitiator to acidic species, Alcohols and polyols provide flexibility and impact resistance to the formulation through copolymerization with the epoxides. Thus, in another embodiment, this invention is an adhesive or coating composition containing one or more styrene oxide monomers as described in Xfi present, a thermal initiator or photoinitiator, and optionally, one or more alcohols or polyols. Suitable photoinitiators include those diaryliodonium, triarylsulfonium and ferrocenium salts that are known to initiate cationic cure. Suitable thermal initiators are those onium and pyridinium salts which are known to produce cationic species capable of initiating cationic cure after heating. By ^ sp example, N-benzylpyridinium and quaternary ammonium salts Related, diaryliodonium salts that thermally decompose in the presence of catalytic amounts of copper compounds, N-allylpyridinium salts that can be thermally converted to acid species in the presence of 2,2,2-azobutyronitrile or benzoyl peroxide. The initiators will be present in any effective amount to initiate the cationic cure process, and will usually be present # in quantities of 0.1 to 10% by weight of the composition. Preferred hydroxyl-containing compounds are diols, such as polycaprolactone diols (e.g. diol sold under the trademark Tone 0201, a product of Union Carbide); polyester diols (for example the diol sold under the trademark Rucoflex S-107-210, a product of Ruco Plymer Corporation); polyether diols based on bisphenol A (for example the diol sold under the trade name Syn Fac 8031, a product of Milliken Chemicals); aliphatic diols (for example the diol sold under the brand MP-diol, a product of Arco Chemical Company); aromatic polyester diols (for example, the diol sold under the brand Stepanpol, a product of Stepan Company). When used, the alcohol or polyol will commonly be present in a molar ratio of the hydroxyl functionality to the epoxide functionality in a range of 1:10 to 10: 1, although any effective ratio to obtain the desired end-use properties can be used. . In some applications of coatings or end-use adhesives, the compositions may contain electrical or thermally conductive fillers. The percentages by weight and the choice of filler for various end-use applications will be known to those skilled in the art. Examples of such fillers are carbon, silica, alumina, silver, copper, gold, nickel, nickel nitride, boron nitride and silicon carbide. Typically, such fillers will be present in amounts in the range of up to about 95% by weight of the composition. EXAMPLES EXAMPLE 1 Preparation of 1,3-diisopropenylbenzene dioxide. A solution A of 1 equivalent of 1,3-diisopropenylbenzene (5 ml, 0.925 g / ml), 29.2 mmol) and 6 equivalents of sodium bicarbonate (15.9 g, 190 mmol) in a 2: 1 mixture (volume: volume) of acetone: water (total 450 ml) is ~ f treated with an aqueous solution containing two equivalents of potassium persulfate (Oxone®) (36.5 g, 59.3 mmol). The suspension is stirred at room temperature for 3 hours. The pH is monitored during this period and remains neutral. The mixture is then filtered by vacuum with a Buechner funnel and the solid residues are washed with methylene chloride (150 ml). The biphasic filtrates are fractionated, and the aqueous phase is extracted with methylene chloride (2 × 200 ml). The organic phases are combined, washed with deionized water (200 ml), and dried with NaHCO3 anhydrous. The solvents are removed in vacuo at 35 ° C. A total of 4.83 g of the clear oil is obtained as the product, confirmed by XH NMR. IR indicates that there is no hydrolysis. After 13 days at room temperature, no aging of the epoxide is observed. EXAMPLE 2: Preparation of divinylbenzene dioxide. 4.92 g of the product is obtained as a mixture of isomers, * confirmed by ^? NMR, using divinylbenzene as the starting material and the same procedure as in Example 1. After one year at room temperature, it is not observed aging. EXAMPLE 3: UV formulations. In order to demonstrate the suitability for curing by IV, the epoxide monomer of Example 1 is formulated in adhesive compositions with several diols and, as the photoinitiator, 1% by weight of a 50% strength solution. weight of an arylsulfonium salt in propylene carbonate, sold under the brand UVI-6974 by Union Carbide. These compositions are compared to control formulations containing a cycloaliphatic epoxide obtained from Union Carbide, such as the product ERL-4221, which has the structure: A sample in the range of 1.5 to 3.0 mg for each composition is exposed to UV radiation and the cure rate is followed by a photodynamic scanning calorimeter DPA-7 Perkin-Elmer (P-DSC). Each sample is equilibrated at a constant temperature (25 ° C) on the calorimeter for one minute and then is exposed to irradiation for a total of four minutes using a 100 Watt Mercury short arc lamp. The resulting traces show an exotherm represented as a sharp or broad peak. The diol used in the compositions, the molar ratio of epoxy to diol, and the DSC results are indicate in Table 1 for inventive styrene epoxy, and in Table 2 for cycloaliphatic epoxy. In the table, Tmax is the time it takes to reach the maximum exothermic peak in seconds, and? H is the exotherm in kJoules per mole of epoxy, measured as the area on the curve from the back of the baseline of four minutes at the start of the exotherm. The time that the reaction takes to reach the Traax is a direct indication of the speed of the reaction; this the shorter the time (ie sharper the peak) the faster the cure reaction for the epoxy, which is a desirable property for these adhesive compositions. In the following tables, the peaks are designated either sharp or broad; for purposes of the present, if more than half of the exotherm has occurred in the first 30 seconds, the peak is defined as sharp, and conversely, if less than half of the exotherm has occurred in the first 30 seconds, the peak It is defined as broad.

The values? H are a direct indication of the degree of opening of the epoxy ring with the negative numbers that reflect the highest degree of conversion of the epoxy. The results indicate that styrene compositions cure more rapidly and more completely than cycloaliphatics, and that they are more compatible with a wider range of diols and in varying molar proportions than cycloaliphatics. With reference to the data in Tables 1 and 2, it can be seen that the cure rates (Tmax) extend from 2.94 seconds to 6.12 seconds for the styrene epoxy, and from 4.62 seconds to 42.66 seconds for the cycloaliphatic epoxy, and that the curing degrees are in the range of -79.1 kJ to -56.4 kJ for the styrene epoxy, and from -79.4 to -10.0 kJ for the cycloaliphatic epoxy. These ranges show that the cure rates and cure rates for formulations containing styrene epoxy are less affected by the choice of diol and the ratio of epoxide to diol than formulations containing cycloaliphatic epoxy. The diols that are used in the formulations are designated in the Tables by their marks. The diol sold under the trademark Tone 0201 is a product of Union Carbide and is a polycaprolactone diol. The diol sold under the trademark Rucoflex S-107-210 is a product of Ruco Polymer Corporation and is a polyester diol. The diol sold under the trademark Syn Fac 8031 is a product of Milliken Chemicals and is a bisphenol A based polyol diol. The diol sold under the trademark MP-diol is a product of Arco Chemical Company and is an aliphatic diol. The diol sold under the Stepanpol brand is a product of Stepan Company and is an aromatic polyester diol. Table 1: DSC data for the inventive epoxy of Example 1 Notes in Table 1: * insoluble in the formulation; ** all spikes are sharp ' EXAMPLE 4: Accelerators for UV curable compositions. This example illustrates that small amounts of a styrene oxide can accelerate the curing rates of epoxides that exhibit moderate rates of UV curing, for example, glycidyl epoxides. A composition designated A is prepared to contain: 1) an equivalent of the epoxide functionality from glycidyl trisperoxide sold under the trademark Heloxy 44 ® by Shell Chemical, Houston, Texas; 2) an equivalent of the hydroxyl functionality of 2-methyl-1,3-propanediol, sold under the brand name MP diol from Arco; Y; 3) 2% by weight of the arylsulfonium salt, sold under the trademark UVI-6974 by Union Carbide. The cure rate of this composition is analyzed by P-15 DSC. To this composition A is added 25% by weight of the divinylbenzene dioxide (prepared from example 2); this composition is designated composition B. The proportion is analyzed ^ HT and degree of cure by P-DSC and show significant increases over the proportion and degree of cure of composition A. The curves in the DSC of compositions A and B, and that of the comparative composition containing divinylbenzene dioxide, designated composition C, are shown in Figure 1. As a person skilled in the art will understand, the peak on a curve of the DSC represents the exotherm á; The sharper the peak, the more quickly the exothermic reaction. Figure 1 shows that composition C exhibits the sharpest peak. Composition A, which contains only the Heloxy epoxide, exhibits a very thin peak which is interpreted as having almost no reactivity, and healing very slowly. The composition B, which contains 25% by weight of divinylbenzene dioxide in combination with 75% by weight of the epoxide - Heloxy exhibits a faster exotherm (although broader than that of composition C), followed by a rapid return to a constant baseline. This is interpreted as to show a simultaneous reaction between the epoxide Heloxy and the divinylbenzene dioxide, in contrast to the long, broad exotherm, which may be indicative of a sum of the epoxide Heloxy and the divinylbenzene reacting independently. EXAMPLE 5: Preparation of additional styrene oxides. Using the same procedure as in the Example 1, the following epoxides are prepared from the materials of corresponding item as listed in Table 3. The products are confirmed by XH NMR. Table 3. Additional styrene oxides EPOXIDE STARTING MATERIAL J j Beta-methyl styrene Betamethylstyrene mono-epoxide j 1 Cinnamyl Acetate Cinnamyl Acetate Epoxide J 1 Cinnamylmethyl ether Cinamylmethyl ether epoxide 1 I Mix of isoeugenol isomers Mix of isomers of epoxides of i - I methyl ether isoeugenol methyl ether 1 J Isoeugenol acetate Isoeugenol acetate epoxide 1 EXAMPLE 6: Analysis of the photodifferential scanning calorimeter of various styrene oxides is carried out by formulating the epoxides with a photoinitiator and a diol. The specific formulation of styrene oxide, diol, molar ratio of epoxide to hydroxyl functionality, Tmax, and kJ per mole of epoxy are indicated in the following Table 4: Table 4 F < * Insoluble in formulation. The P-DSC data gives information that is useful in understanding the capabilities of these monomers in the formulation of cationically curable adhesives: The reactivity (by epoxide ring) for alphamethylstyrene bisepoxide and monofunctional alphamethylstyrene epoxide are comparable ( compare + entries 1 and 2, and 5 and 6); The epoxide substitution pattern has an impact about its reactivity. the comparison of T (max) for the a- and β-methylstyrene oxide formulations indicates that the a-isomer reacts more rapidly than the β-isomer under similar conditions (compare articles 2 and 8; 3 and 9; 4 and 10).; 6 and 11; 7 and 12). This can be attributed to the fact that the a-isomer can open the ring to a more stable carbocation, , Tertiary, benzyl, while the β-isomer produces a less stable, benzylic secondary carbocation, Comparison of the enthalpies of the polymerization (? H) indicates that the β-isomer seems to react as much or more completely (compare articles 2 and 8; 3 and 9; 4 and 10; 6 and 11; 7 and 12). With respect to cinnamyl derivatives, Article 13 demonstrates that in the absence of an alcohol, the ester group to mitigate the reactivity of the epoxide, and the Epoxide of cinnamyl acetate does not polymerize. The comparison of cinnamyl acetate epoxide formulations (articles 13-17) with the corresponding cinnamyl ether epoxide formulations (articles 23-27) shows that there is more rapid and complete reaction for the cinnamyl ether formulations. During curing, the ester carbonyl presumably interacts with the proximal cationic center formed from the ring opening, whereby the propagation reaction is inhibited.

In contrast to the epoxide of cinnamyl acetate, the epoxide of isoeugenol acetate cures in the absence of a mixed alochol (compare articles 13 and 18). This effect can be attributed to two structural characteristics of the epoxide. First, the ester carbonyl is further removed from the nascent carbocationic site in the benzylic position. Second, the aromatic ring is not flexible enough to allow interaction between these sites. These two characteristics serve to mitigate the "communication" between the carbonyl and the epoxide. On the other hand, the epoxide of isoeugenol acetate is relatively reactive in the presence of alcohols (articles 19-22). These results indicate that an ester functionality can be tolerated in these styrene oxide systems.

Claims (2)

1. CLAIMS 1.. A curable compound cationically initiated by radiation or thermally characterized because it contains the structure independently it is hydrogen, or aliphatic, alicyclic or aromatic groups, which may contain heteroatoms, characterized in that they do not hinder the cationic polymerization of the epoxy functionality either through the spherical interaction or through 10 the action of a Lewis base; and is an integer from 1 to 6, w is an integer from 0 to 5, with the proviso that y + w < .
2. 2. A cationically curable adhesive or coating composition characterized in that it comprises: (a) a cationically curable compound initiated thermally or by radiation of the structure: wherein R1 to R4 independently represents hydrogen, or aliphatic, alicyclic or aromatic groups, which may contain heteroatoms, characterized in that they do not impede the cationic polymerization of the epoxy functionality either through the spherical interaction or through the action of a Lewis base; and is an integer from 1 to 6, w is an integer from 0 to 5, with the proviso that y + w =. 6. b) a thermal initiator or cationic photoinitiator; Y c) one or more alcohols or polyols.