ACTIVE ESTER CURING AGENT COMPOUND FOR THERMOSETTING RESINS, FLAME RETARDANT COMPOSITION COMPRISING SAME, AND ARTICLES MADE THEREFROM

Abstract

There is provided herein a composition containing (A) a phosphorus-containing aromatic polyester of the general formula (I) described herein which has a weight average molecular weight of from 1,000 to 20,000 and which is concurrently a flame retardant O and an active ester curing agent, and, (B) a solvent, such as a solvent commonly used in thermosetting resin formulations and copper-cias laminate preparation.

Claims

1. A composition comprising: (A) a phosphorus-containing aromatic polyester of formula (I) having a weight average molecular weight of from 1,000 to 20,000 which is concurrently a flame retardant and an active ester curing agent wherein the formula (I) is: ##STR00005## where X is a bivalent aromatic hydrocarbon group containing from 6 to about 12 carbon atoms, which may be optionally substituted, or X is a bivalent linear or branched alkylene group of from 1 to 8 carbon atoms, or a bivalent linear or branched alkenylene group of from 2 to about 8 carbon atoms, Y is ##STR00006## where Z is selected from the group consisting of a covalent bond, SO.sub.2, C(CH.sub.3).sub.2, CH(CH.sub.3), and CH.sub.2; a=0-2; b=0-2, and wherein a and b are not both zero, wherein the wavy lines of each structure of Y indicate the bonds to the O atoms which Y bridges in the general formula (I); R.sup.1 is selected from H, an alkyl group of from 1 to about 4 carbon atoms, phenyl, naphthyl, ##STR00007## where R.sup.2 is H or C(O)R.sup.3 and where R.sup.3 is selected from an alkyl group of from 1 to 4 carbon atoms, a phenyl group, a napthyl group and an aromatic phenol group which is selected from one of a phenol group, o-cresol group, m-cresol group, p-cresol group, -naphthol group, and a -naphthol group, and when R.sup.2 is H, R.sup.1 cannot be phenyl or naphthyl, and n is from 1 to about 40; and, (B) a solvent.

2. The composition of claim 1 wherein the solvent (B) is a solvent used in copper clad laminate preparation.

3. The composition of claim 1 wherein R.sup.1 is ##STR00008## and where X is a bivalent aromatic hydrocarbon group of from 6 to 12 carbon atoms which is optionally substituted with an alkyl or alkoxy group of up to 6 carbon atoms.

4. The composition of claim 1 wherein R.sup.1 is an alkyl of from 1 to about 4 carbon atoms and where X is a bivalent aromatic hydrocarbon group of from 6 to 12 carbon atoms which is optionally substituted with an alkyl or alkoxy group of up to 6 carbon atoms.

5. The composition of claim 1 wherein R.sup.1 is ##STR00009## and where X is a bivalent linear or branched alkylene group of from 1 to 8 carbon atoms, or a bivalent linear or branched alkenylene group of from 2 to about 8 carbon atoms.

6. The composition of claim 1 wherein R.sup.1 is H or an alkyl of from 1 to about 4 carbon atoms and where X is a bivalent linear or branched alkylene group of from 1 to 8 carbon atoms, or a divalent linear or branched alkenylene group of from 2 to about 8 carbon atoms.

7. The composition of claim 1 wherein X is a bivalent aromatic hydrocarbon group of from 6 to 12 carbon atoms which is optionally substituted with an alkyl or alkoxy group of up to 6 carbon atoms.

8. The composition of claim 1 wherein X is a divalent linear or branched alkylene group of from 1 to 8 carbon atoms, or a divalent linear or branched alkenylene group of from 2 to about 8 carbon atoms.

9. The composition of claim 1 wherein n is from 1 to about 40.

10. The composition of claim 1 wherein n is from 2 to about 40.

11. The composition of claim 1 wherein n is from 2 to about 20.

12. The composition of claim 1 wherein n is from 3 to about 20.

13. The composition of claim 1 wherein the solvent (B) is selected from the group consisting of methyl ethyl ketone, acetone, 1-methoxy-2-propanol, tetrahydrofuran, methyl cellosolve, toluene, xylene, propylene glycol methyl ether and acetate thereof, and combinations thereof.

14. A flame retardant composition comprising a phosphorus-containing aromatic polyester of formula (I) having a weight average molecular weight of from 1,000 to 20,000 which is concurrently a flame retardant and an active ester curing agent, wherein formula (I) is: ##STR00010## where X is a bivalent aromatic hydrocarbon group containing from 6 to about 12 carbon atoms, which may be optionally substituted, or X is a bivalent linear or branched alkylene group of from 1 to 8 carbon atoms, or a bivalent linear or branched alkenylene group of from 2 to about 8 carbon atoms, Y is ##STR00011## where Z is selected from the group consisting of a covalent bond, SO.sub.2, C(CH.sub.3).sub.2, CH(CH.sub.3), and CH.sub.2; a=0-2; b=0-2, and wherein a and b are not both zero, wherein the wavy lines of each structure of Y indicate the bonds to the O atoms which Y bridges in the general formula (I); R.sup.1 is selected from H, an alkyl group of from 1 to about 4 carbon atoms, phenyl, naphthyl, ##STR00012## where R.sup.2 is H or C(O)R.sup.3 and where R.sup.3 is selected from an alkyl group of from 1 to 4 carbon atoms, a phenyl group, a napthyl group and an aromatic phenol group which is selected from one of a phenol group, o-cresol group, m-cresol group, p-cresol group, -naphthol group, and a -naphthol group, and when R.sup.2 is H, RI cannot be phenyl or naphthyl, and n is from 1 to about 40.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0022] There is provided in one embodiment herein a compound having the general formula (I):

##STR00001##

having a weight average molecular weight of from 1,000 to 20,000, where X is a bivalent aromatic hydrocarbon group containing from 6 to about 12 carbon atoms, and which includes the non-limiting examples of phenylene groups, naphthalene groups, biphenylene groups, etc., which groups may optionally include a substituent bonded to the aromatic ring, such as an alkyl group or alkoxyl group containing up to 6 carbon atoms, or
X is a bivalent linear or branched alkylene group of from 1 to 8 carbon atoms, or a bivalent linear or branched alkenylene group of from 2 to about 8 carbon atoms,

[0023] Y is

##STR00002##

where Z is selected from the group consisting of a covalent bond, SO.sub.2, C(CH.sub.3).sub.2, CH(CH.sub.3), and CH.sub.2; a=0-2; b=0-2
wherein the wavy lines of each structure of Y indicate the bonds to the O atoms which Y bridges in the general formula (I);
R.sup.1 is H, an alkyl group of from 1 to about 4 carbon atoms, phenyl, naphthyl,

##STR00003##

where R.sup.2 is H or C(O)R.sup.3 and where R.sup.3 is selected from an alkyl group of from 1 to 4 carbon atoms, a phenyl group, a napthyl group and an aromatic phenol group which is selected from one of a phenol group, o-cresol group, m-cresol group, p-cresol group, -naphthol group, and a -naphthol group,
and when R.sup.2 is H, R.sup.1 cannot be phenyl or naphtyl,
and n is from 1 to about 40.

[0024] In one non-limiting embodiment herein, the phosphorus-containing flame-retardant polyfunctional curing agent can comprise a mixture of different structures of the general formula (I), e.g., the mixture can comprise wherein at least 50 wt % of the general formula (I) structures, and preferably more than 70 wt % of the general formula (I) structures are such that Y is chosen from moieties (i) and (ii) as noted above, with the remaining different structures of the general formula (I) being such that Y is chosen from the (iii) moiety noted above.

[0025] It is preferable that the weight-average molecular weight Mw of the phosphorus-containing aromatic polyester of the invention be within a range of 1,000 to about 20,000. For this range of molecular weight, the solubility in MEK and other suitable organic solvents is good without any partial precipitation of polymer particles. In addition, this range of molecular weight can provide viscosities of MEK solutions which are suitable for epoxy laminate preparation. The inherent viscosity of the phosphorus-containing aromatic polyester of the invention is preferably not smaller than 0.02 dl/g and not greater than 0.25 dl/g, and more preferably not smaller than 0.05 dl/g and not greater than 0.20 dl/g. The excessively low inherent viscosity resulting from too low a molecular weight would cause a decrease in thermal properties of the cured product. On the other hand, an excessively high inherent viscosity results in deficient flowability and reduces formability of cured product due to high viscosity.

[0026] The polymeric polyfunctional curing agent of the invention having the inherent viscosity within this range can be dissolved up to 70 wt % in MEK. These 70 wt % solutions are homogeneous, transparent, and stable at room temperature, without any precipitation of solids over a period of 1 month.

EXAMPLES

[0027] Solubility in MEK of the phosphorus-containing aromatic polyester of the invention was evaluated by the following procedure. Mixtures of the polymers in MEK with concentrations of 50 and 70% were prepared in screw bottles and kept in a shaker at 60 C. over a period of 4 h. When the full dissolution was attained the transparent mixture was cooled down to room temperature and stored over a period of 1 month. During this period no precipitation was observed. The inherent viscosity of the polymers were determined with a Cannon-Fenske viscometer, by using polymer solutions in N,N-dimethylformamide (DMF) at 25 C., at a concentration of 20 g/dL. The measurement of the molten viscosity of the polymers was described in Analytical Example 1.

[0028] The polymeric polyfunctional curing agents of the invention have an advantage of thermal processing since they melt and soften below 200 C. without any solvent.

[0029] The phosphorus-containing aromatic polyesters are generally prepared from polyhydric phenol and polyvalent carboxylic acid. The phosphorus-containing aromatic polyesters of the invention may be prepared by ester exchange reaction. An example of an ester exchange reaction is one in which the aromatic polyester is obtained by the step of acetylation of polyhydric phenol by acetic anhydride, followed by acydolysis of the acetylated phenol with polyvalent carboxylic acid. Another way of preparation of the polymers of the invention is by reacting chloranhydrides of the polyvalent acids with polyhydric alcohol followed by acetylation of the hydroxyl end-groups. It will be understood by those skilled in the art that other common methods for making polyesters may be applied for the preparation of the polymers of the invention.

[0030] In one non-limiting embodiment herein, the method of making the active ester curing agent of the compound(s) of the general formula (I) described herein can comprise the following general reaction mechanism:

##STR00004##

where Ac=acetyl moiety

[0031] This reaction does not require the use of any additional solvents. Acetic anhydride is both solvent and reagent. It is used between 1 to 10 molar excess and most preferably 2 to 5 molar excess with respect to DOPO-HQ. The reaction is carried out at 170 C.-260 C. and most preferably 190 C.240 C. for a period of 1-16 hours and most preferably 5-8 hours.

GPCInstrument and Running Conditions

[0032] Pumping system: HP model 1100 [0033] Detector: RI: Knauer 2300/2400 [0034] UV: HP model 1100 [0035] Columns: PLgel, Agilent, 300*8.0 mm, 50 A+100 A+500 A (PLgel 300*7.5)+1000 A [0036] Column Temp.: 60 C. [0037] Solvent: THF for Preparation Example 1, and DMF for Preparation Example 2-4 and Comparative Example 1 [0038] Flow: 0.8 ml/min. [0039] Injection amount: 30 l

Preparation Example 1

[0040] A 1 L 4-necked flask, equipped with a mechanical stirrer, a thermometer and a nitrogen inlet, was charged with DOPO-HQ (293.9 g, 0.9 mol) and acetic anhydride (367.2 g, 3.6 mol). The initial slurry became clear after 30 min at 140 C. and the solution was further heated at reflux for an additional 2 h. Isophthalic acid (100 g, 0.6 mol) and 0.04 g potassium acetate were then added and the reaction mixture was heated to 220 C. At this point, vacuum was applied to remove more efficiently both the excess acetic anhydride and the formed acetic acid from the reaction zone, thus accelerating the polycondensation. The temperature was increased to 230 C. During this period, the vacuum was 30 mbar. The resulting, very viscous, liquid product was poured onto an aluminum plate. The final solid product, obtained in a quantitative yield, had a light-brown color and contained 4% DOPO-HQ-monoacetate and DOPO-HQ-acetate-isophthalate, 10% unreacted DOPO-HQ-Diacetate and 86% oligomers (HPLC area %). The phosphorus content in the product was 6.8%. GPC analysis in THF showed the weight average Mw of 1250 g/mol and number average Mn of 750 g/mol (FIG. 1). Inherent viscosity of the product in DMF was 0.17 dL/g. The product had excellent solubility in MEK. Up to 70% of the polymeric DOPO-HQ isophthalate so prepared was dissolved in MEK at 55 C. to afford a clear solution. No precipitation was observed upon cooling to room temperature over a period of 1 month.

Preparation Example 2

[0041] A 0.25 L 4-necked flask, equipped with a mechanical stirrer, a thermometer and a nitrogen inlet, was charged with DOPO (21.6 g, 0.1 mol), benzoquinone (10.3 g, 0.095 mol) and acetic acid (50 ml). The flask was heated to reflux and maintained at that temperature for 3 h to afford a slurry of DOPO-HQ in the solvent. Subsequently, acetic anhydride (30.6 g, 0.3 mol) was introduced, followed by heating to 140 C. Part of the acetic acid was distilled off during the heating. The initial slurry became clear after 30 min at 140 C. and the solution was further heated at reflux for an additional 2 h. Isophthalic acid (10 g, 0.06 mol) and 0.01 g potassium acetate were then added and the reaction mixture was heated to 220 C. At this point, vacuum of 30 mbar was applied to remove more efficiently both the excess acetic anhydride and the formed acetic acid from the reaction zone. The resulting, very viscous, liquid product was poured onto an aluminum plate. The final solid product, obtained in a quantitative yield, had a brown color and contained 3% DOPO-HQ-monoacetate and DOPO-HQ-acetate-isophthalate, 6% unreacted DOPO-HQ-Diacetate and 91% oligomers (HPLC area %). The phosphorus content in the product was 6.7%. GPC analysis of the product in DMF showed the Mw of 12760 g/mol and Mn of 5207 g/mol (FIG. 2). The product had excellent solubility in MEK. Up to 70% of the polymeric DOPO-HQ isophthalate so prepared was dissolved in MEK at 55 C. to afford a clear solution. No precipitation was observed upon cooling to room temperature over a period of 1 month.

Preparation Example 3

[0042] A 0.25 L 4-necked flask, equipped with a mechanical stirrer, a thermometer and a nitrogen inlet, was charged with DOPO-HQ-Diacetate (122 g, 0.3 mol) and heated to 170 C. to full melting. Isophthalic acid (33 g, 0.2 mol) and potassium acetate 0.2 g were added and the reaction mixture was heated for 2 h at 280 C. without vacuum and 1 h with vacuum of 30 mbar. During that time the formed acetic acid was removed, thus accelerating the polycondensation.

[0043] The resulting, very viscous, liquid product was poured onto an aluminum plate. The final solid product, obtained in a quantitative yield, had brown color and contained 4% DOPO-HQ-monoacetate and DOPO-HQ-acetate-isophthalate, 5% unreacted DOPO-HQ-Diacetate and 91% oligomers (HPLC area %). GPC analysis of the product in DMF showed the Mw of 14201 g/mol and Mn 5028 g/mol (FIG. 3). The product had excellent solubility in MEK. Up to 60/o of the polymeric DOPO-HQ isophthalate so prepared was dissolved in MEK at 55 C. to afford a clear solution. No precipitation was observed upon cooling to room temperature over a period of 1 month.

Preparation Example 4

[0044] A 0.25 L 4-necked flask, equipped with a mechanical stirrer, a thermometer and a nitrogen inlet, was charged with DOPO-HQ-Diacetate (49 g, 0.12 mol) and heated to 170 C. to full melting. Isophthalic acid (19.2 g, 0.116 mol) and potassium acetate 0.1 g were added and the reaction mixture was heated for 1 h at 230 C. without vacuum and 1 h with vacuum of 30 mbar. During that time the formed acetic acid was removed. The resulting, very viscous, liquid product was poured onto an aluminum plate. The final solid product, obtained in a quantitative yield, had light-brown color and contained 9% DOPO-HQ-monoacetate and DOPO-HQ-acetate-isophthalate, 3.7% unreacted DOPO-HQ-Diacetate and 87.3% oligomers (HPLC area %). GPC analysis of the product in DMF showed the Mw of 19880 g/mol and Mn 6700 g/mol. Up to 600/o of the polymeric DOPO-HQ isophthalate so prepared was dissolved in MEK at 55 C. to afford a clear solution.

Comparative Example 1

[0045] A 0.25 L 4-necked flask, equipped with a mechanical stirrer, a thermometer and a nitrogen inlet, was charged with DOPO-HQ-Diacetate (106 g, 0.26 mol) and heated to 170 C. to full melting. Isophthalic acid (43 g, 0.26 mol) and potassium acetate 0.3 g were added and the reaction mixture was heated at 280 C. for 2 h without vacuum and 1 h with vacuum of 30 mbar. As the reaction continued, the mixture became more viscous. During the entire reaction the acetic acid formed was distilled out of the reaction zone to accelerate the polycondensation. The resulting, very viscous, hot liquid product was quickly poured onto an aluminum plate to avoid solidification in the flask. The final solid light-brown product was obtained in a quantitative yield. The product contained 2.8% DOPO-HQ-monoacetate and DOPO-HQ-acetate-isophthalate, 2.2% unreacted DOPO-HQ-Diacetate and 95% higher molecular weight oligomers (HPLC area %). The phosphorus content in the product was 5.4%. GPC analysis in DMF showed the Mw of 32610 g/mol and Mn of 13360 g/mol (FIG. 4). The product did not dissolve in MEK at 60 C. over a period of 3 h. Inherent viscosity of the product in DMF was 0.32 dL/g.

Analytical Example 1

[0046] A Brookfield DV-II+ Pro Viscometer equipped with SS spindle #31 was used to measure the molten viscosity of polymeric DOPO-HQ isophthalates. About 15 grams of polymeric DOPO-HQ isophthalate was melted in a disposable chamber and allowed to equilibrate at measuring temperatures. The viscosity readings were taken from 200 to 225 C. The speed was kept between 2 to 30 RPM to obtain a torque above 10%. Polymeric DOPO-HQ isophthalates, soluble in MEK (such as samples made from Preparation Example 1-4), have molten viscosity of 25000-625000 cP at 200 C. Polymeric DOPO-HQ isophthalates, insoluble in MEK (such as sample made from Comparative Example 1), have softening points above 200 C., and their molten viscosities are not measured.

Laminate Examples 5-6

[0047] The polyester synthesized in Example 1 and low molecular weight DOPO-HQ-diacetate were explored as co-curing agents for the epoxy laminate application. The above compound together with phenolic Novolac was used to cure multi-functional epoxy resins DEN 438 and EPON 164. All the materials information is listed in Table 1. The solids content was maintained at 66.67% with the addition of MEK/Dowanol (80/20) solvent mixture. A varnish formulation was prepared therefrom which had a phosphorous content of 2.4-2.7% and the composition contents are shown in Table 2.

TABLE-US-00001 TABLE 1 Materials Trade Name (Producer) General Information Function SD-1708 (ex Momentive) Phenolic novolac Curing agent DEN 438 (ex Dow Chemicals) Phenol novolac epoxy Epoxy resin EPON 164 (ex Momentive) Cresol novolac epoxy Epoxy resin Methyl ethyl ketone (ex Fluka) Butan-2-one Solvent Dowanol (ex Fluka) 1-methoxy 2-propanol Solvent Dimethylformamide (ex Fluka) N,N-Dimethylformamide Solvent 2-MI (ex Air Products) 2-methyl imidazole Catalyst Glass Cloth (ex BGF Industries) E-Glass Reinforcing agent Copper foil (ex Gould Electronics) JTC, 1.0 oz./ft.sup.2 Resistance to oxidation in warm and humid environments and for precise etching behavior and others

TABLE-US-00002 TABLE 2 Varnish Formulation for Example 5 and 6 DEN EPON Formulation 438 164 Co-Curing Agent SD-1708 2-mI Exp 5 24.3 29.7 35.8.sup.1 10 0.065 Exp 6 24.0 29.4 35.3.sup.2 11.3 0.02 .sup.1DOPO-HQ-diacetate for Experiment 5 .sup.2Sample made from Preparation Example 1 for Experiment 6

TABLE-US-00003 TABLE 3 Laminate Properties with formulation as shown in Table 2 Exp 5 (DOPO-HQ- Exp 6 (Sample from Laminate Properties diacetate; Mw <500) Preparation Example 1) Glass Transition 150 194 Temperature (DMA - 3 C./min) Flammability (UL-94) V-0 V-0 Pressure Cooker Test Pass 30 min Pass 90 min