GB1575157A - Flame retardant polycondensation products derived from phosphorus-containing dicarboxylic acids - Google Patents

Abstract

Flame retardant, of high molecular weight, comprising phosphorous-containing products of polycondensation of a dicarboxylic acid which has the formula: <IMAGE> in which each of R1, R2 and R3 denotes a hydrogen, a halogen or an alkyl, cycloalkyl, aryl or aralkyl group, with a polyalcohol.

Description

(54) FLAME RETARDANT POLYCONDENSATION PRODUCTS DERIVED FROM PHOSPHORUS -CONTAINING DICARBOXYLIC ACIDS (71) We, SANKO KAIHATSU KAGAKU KENKYUSHO, a Japanese Cor poration, of 40, 3-chome, Andojibashi-dori, Minami-ku, Osaka-shi, Japan, do hereby de clare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be par ticularly described in and by the following statement:- This invention relates to flame retardants comprising phosphorus-containing polycon densation products having a high molecular weight.

Organophosphorus or organohalogen compounds have been used as flame retardnts for thermoplastic resins, as disclosed in, for example, U.S. Patent Specifications Nos.

3,247,135; 3,262,894; 3,278,464; 3,359,220; 3,368,916 and 3,372,141; British Patent Specifications Nos. 1,015,212; 1,094,723 and 1,108,064; and Belgian Patent Specification No. 709,417. On the one hand, when known organophosphorus compounds are added to thermoplastic resins in an amount sufficient to impart flame retardancy, disadvantages are observed in that the softening point of the resin is lowered and its heat resistance is reduced. On the other hand, conventional flame retardants containing halogen atoms such as bromine or chlorine have low thermal stability. For example, tetrabromobisphenol A decomposes at 220"C., generating bromine.

According to a first aspect of the present invention, a polycondensation product which can be used as a flame retardant is of a dicarboxylic acid represented by Formula I

wherein R1, R2 and R, are the same or different and are each hydrogen, halogen, alkyl, cycloalkyl, aryl or aralkyl, with a polyhydric alcohol and, if desired, a monocarboxylic acid or a monohydric alcohol.

In accordance with a second aspect of this invention, a flame retardant resin compoosition comprises a normally inflammable thermoplastic resin and a suitable amount of a phosphorus-containing polycondensation product as defined above.

The phosphorus-containing polycondensation products wherein any one or more of R1, R2 and R3 of Formula I are halogen, preferably bromine, exhibit excellent flameretardancy and have thermal stability good enough not to generate halogen even at temperatures above 300"C.

Dicarboxylic acids of Formula I may be prepared by heating a compound represented by Formula II,

wherein Rl, R2 and R3 are as defined above, with itaconic acid.

Generally, this reaction may be effected at temperatures of 100"C to 2500C without any catalysts. The reaction is effected quantitatively and no by-products are formed. Therefore, using the stoichiometric amounts, the pure dicarboxylic acid of Formula I can be obtained. This can be normally confirmed by paper chromatography, thin layer chromatography or liquid chromatography. From an infrared absorption spectrum, end products can be easily identified to be compounds of Formula I from the disappearance of the P-H bond (wave number 2340) and double bond (wave number 1630) and the formation of CH2 and CH groups and the P-C bond (wave number about 718).

Compounds of Formula II are known and may be prepared by the method disclosed in U.S. Patent Specification No. 3,702,878 or Japanese Patent Publication No. 17979/75, or methods similar thereto.

For example, compounds of Formula III,

wherein R1, R2 and Ra are as defined above, are obtained by reaction of 1 mol of a substituted o-phenylphenol compound of Formula IV,

wherein Rl, R2 and R3 are as defined above, with 1.3 mols of phosphorus trichloride in the presence of 0.003 mols of zinc chloride at temperatures of 1300C to 2000C for about 20 hours. The compound of Formula III thus obtained is purified by distillation and hydrolyzed by adding an excess of water. The remaining water is then removed under reduced pressure (about 10 mm Hg), to form a compound of Formula II.

R1, R2 and Ra are preferably hydrogen, chlorine, bromine, methyl, tert-butyl, cyclohexyl, phenyl or benzyl. More preferably, R1 and R3 are each hydrogen, chlorine or bromine and R2 is chlorine or bromine.

Examples of compounds of Formula II include 9,10 - dihydro - 9 - oxa - 10 - phosphaphenanthrene - 10 - oxide; 6 - bromo9,10 - dihydro - 9 - oxa - 10 - phosphaphenanthrene - 10 - oxide; 6,8 - dibromo9,10 - dihydro - 9 - oxa - 10 - phosphaphenanthrene - 10 - oxide; 8 - tert - butvl9,10 - dihydro - 9 - oxa - 10 - phosphaphenanthrene - 10 - oxide; 2,6,8 - trichloro9,10 - dihydro - 9 - oxa - 10 - phospnaphenanthrene - 10 - oxide; and 6 - phenyl9,10 - dihydro - 9 - oxa - 10 - phosphaphenanthrene - 10 - oxide.

Dicarboxylic acids of Formula I can be condensed with alcohols to form esters in the same manner as other carboxylic acids.

Polyhydric alcohols which may be used in this invention are, for example, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, 1,3propanediol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, 1,10 - decanediol, 1,4 - di hydroxymethylcyclohexane, hydrogenated bisphenol A, ethylene oxide adducts of bisphenol A, ethylene oxide adducts of tetrabromobisphenol S, 2,2-dibromomethyl-1,3-propanediol, glycerine, trimethylol ethane, trimethylol propane or pentaerythritol.

In the polycondensation reaction according to this invention, monocarboxylic acids or monohydric alcohols may also be used, if desired, to obtain polycondensation products having further improved compatibility with thermoplastic resins. Polycondensation products having hydroxyl or carboxyl groups at the molecular chain terminals generally exhibit less compatibility with resins.

Monocarboxylic acids or monohydric alcohols can act to improve the compatibility through reaction with such terminal groups.

Examples of suitable monocarboxylic acids are acetic acid, propionic acid, benzoic acid, naphthoic acid, palmitic acid and (meth)acrylic acid adducts of compounds of Formula II. Examples of suitable monohydric alcohols are methanol ethanol, propanol, butanol, ethylene glycol monomethylether, ethylene glycol monobutylether, ethylene glycol monophenylether, ethylene oxide adducts of tribromophenol, 2,2,2 - tribromomethylethanol, palmityl alcohol and stearyl alcohol.

The polycondensation reaction may be carried out in the presence of or in the absence of catalysts. The catalysts which may be used are, for example, acidic catalysts such as sulfuric acid, paratoluenesulfonic acid or phosphoric acid, or metal compounds such as zinc acetate, lead acetate, germanium oxide, antimony trioxide, sodium alcoholates or potassium phenylphosphonate.

The polycondensation products of this invention may also be prepared by effecting alcoholysis between polyhydric alcohols and dicarboxylic acids of Formula I (and, if desired, monocarboxylic acids) which have previously been esterified with volatile lower alcohols.

The dehydration- or dealcoholization condensation may be carried out at temperatures of 1500 to 290"C. When dihydric alcohols are used as the polyhydric alcohol, linear polycondensation products are obtained. When polyhydric alcohols having three or more hydroxy groups are used, it results in the formation of polycondensation products with branched chains.

The molecular weight of the polycondensation products is an important factor for their utility, because it has a great influence on their softening point and their compatibility with thermoplastic resins. The average molecular weight depends on the degree to which polycondensation is allowed to advance and the molar ratio of the phosphorus-containing dicarboxylic acid, monocarboxylic acid, polyhydric alcohol and monohydric alcohol. The lower the molecular weight, the better is the compatibility with thermoplastic resins, but the heat resistance of the resins is apt to be reduced. The molecular weight of the polycondensation products of this invention is preferably from 1,000 to 20,000, and more preferably from 2,000 to 13,000. Within the preferred range good compatibility with various types of thermoplastic resins can be achieved without any appreciable reduction in heat resistance. The compatibility may vary depending on the nature of R1, R2 and/or R3 in Formula I and the type of polyhydric alcohols, monocarboxylic acids and/or monohydric alcohols, both of which may be varied as appropriate to prepare polycondensation products having good compatibility with any given resin.

Alternatively, the polycondensation products of this invention may be prepared by effecting the polycondensation reaction with polyhydric alcohols simultaneously with the formation of the compounds of Formula I by the reaction. of compounds of Formula II with itaconic acid.

The polycondensation products of this invention which have a phosphorus content of 3.5% to 8.5% by weight usually have a high softening point and good compatibility with various thermoplastic resins, so that a flame retardant resin composition can be obtained without lowering its heat resistance.

Examples of the thermoplastic resins include polystyrenes, acrylonitrile-styrene copolymers, polycarbonates, polytetraphthalate resins (e.g.

polyethylene terephthalate, polybutylene terephthalate and polyarylene terephthalates), ABS resins, polyphenylene oxide resins, polymethcarylate resins (e.g. polymethylmethacrylate) and polyvinyl chloride.

In accordance with this invention, a flame retardant resin composition is obtained by compounding the phosphorus-containing polycondensation product with the thermoplastic resin so as to give a phosphorus content of 0.15% to 2.5% by weight based on the weight of the resin. This phosphorus content normally corresponds to adding 2 to 30 parts of the polycondensation product to 100 parts by weight of the thermoplastic resin.

This invention will be illustrated by the following examples. Softening points are measured by a capillary tube method.

Example 1.

432 g (2 mols) of 3,10 - dihydro - 9 - oxa10 - phosphaphenanthrene - 10 - oxide (hereinafter referred to as HCA), 260 g (2 mols) of itaconic acid and 1,300 g of dimethyl sulfoxide are fed into a four-necked flask of 2,000 ml capacity provided with a thermometer, a gas inlet, a stirrer and a reflux condenser.

While slowly introducing nitrogen gas through the gas inlet, the flask is heated until the dimethyl sulfoxide slowly refluxes. Reaction is effected at 1900C for about 2 hours.

After cooling the reaction mixture, white crystals are deposited, which are then filtered and washed with 700 ml of dioxane. After drying, about 620 g of white crystals are obtained.

M.P.: 2030C Acid Value: 325 (Calculated, 323.7) Saponification Value: 488 (Calculated, 485.5) Elementary Analysis: Found: C 60.2%, H 4.5% Calculated: C 59.0%, H 4.3% The foregoing shows that the end product is a compound of Formula I wherein R,, R2 and Ra are each hydrogen.

588 g (1.7 mols) of the above compound and 210 g of ethylene glycol are charged into a 1000 ml three-necked flask provided with a thermometer, a stirrer and a packed column type rectifier, 3 cm in diameter and 20 cm in filler height. On heating the flask, a polycondensation reaction occurs and water from the top of the rectifier is distilled out.

While slowly removing water, the temperature of the contents is elevated to 200"C and this temperature is maintained for about 3 hours.

Thereafter, 0.2 g of zinc acetate and 0.1 g of germanium oxide are added. The rectifier is then removed and a vacuum distillation port provided with a cold trap is connected thereto.

While slowly distilling out ethylene glycol, the inside of the flask is put under reduced pressure of 1 mm Hg. Reaction is carried out at 230"C for 2 hours.

The reaction products are poured into a stainless vat and cooled to solidify them. A colorless, transparent glassy solid is thus ob tained.

Content of Phosphorus: 8.2% by weight Softening Point: ca. 600C Approximate Molecular Weight: 4,500 (According to a terminal group determi nation).

The linear polycondensate above obtained has a good compatibility with acrylonitrilestyrene copolymers, polymethacrylate resins, polyterephthalate resins, polyvinyl chloride resins and ABS resins.

Next, 10 parts by weight of the above polycondensate are added to 100 parts by weight of each of bisphenol A/terephthalic acid polycondensate (PAT) and polyvinyl chloride (PVC), and blended in a Brabender mill at an appropriate blending temperature for the respective resin. Samples for burning test, 3.2 mm thick, 12.2 mm wide and 152.4 mm long, are obtained by subjecting the compounds to compression moulding. A flame retardancy rating is obtained by measuring the burning time of a test sample according to the standard of Underwriters Laboratories Inc., Subject 94.

As a result of the burning test, both samples of the flame-retarded PAT and PVC are rated V-O.

Example 2.

864 g (4 mols) of HCA, 520 g (4 mols) of itaconic acid and 520 g (4 X 1.25 mols) of neopentyl glycol are charged into a fournecked 200 ml flask provided with a thermometer, a gas inlet, a stirrer and a water outlet.

The flask is heated while slowly introducing nitrogen gas through the gas inlet. When the temperature of the contents reaches 120"C, the reactants melt and water is formed.

The temperature is then slowly elevated while stirring and maintained at 2000C for an hour. The water outlet is connected to a vacuum distillation port equipped with a cold trap and the inside of the flask is put under reduced pressure of 18 mm Hg. This pressure is maintained for an hour to distill out water and neopentyl glycol. Thereafter, the reaction is continued under reduced pressure (1 mm Hg) at 2200C for a further two hours.

The reaction products are poured into a stainless vat and cooled to solidify them. A light yellow, transparent glassy solid is thus obtained.

Content of Phosphorus: 7.2% Softening Point: 960C Approximate Molecular Weight: 3,800 The linear polycondensate above obtained has good compatibility with polystyrene, polycarbonates, polyphenylene oxides and polyvinyl chloride.

Further, the above polycondensate is saponified and decomposed by a methanol solution of potassium hydroxide and then rendered acidic by hydrochloric acid.

After evaporation of methanol, precipitates appear which are then recrystallized from dimethyl sulfoxide simultaneously with dehydration. The product thus obtained, according to the melting point and liquid chromatography, is identical with the compound of Formula I obtained in Example 1.

The foregoing shows that the polycondensation reaction can be effected simultaneously with the formation of compounds of Formula I through the reaction of compounds of Formula II with itaconic acid.

Next, the burning test and flame retardancy rating are effected in the same manner as in Example 1.

Amounts of Poly Resins condensate Added* Rating Polycarbonate (PC) 8 V-2 PAT 10 V-0 Polyphenylene Oxide 7 V--O (PPO) PVC 10 V--O 8) Parts per 100 parts by weight of resins.

Example 3.

180 g (4 mols) of 6 - bromo - 9,10dihydro - 9 - oxa - 10 - phosphaphenanthrene - 10 - oxide (MP 1970C, hereinafter referred to as 6-bromo-HCA), 520 g (4 mols) of itaconic acid and 520 g (4 X 1.25 mols) of neopentyl glycol are charged into the same four-necked flask as in Example 2 and, similarly, a light yellow, transparent glassy solid is obtained.

Content of Phosphorus: 6.2% Softening Point: 1190C Approximate Molecular Weight: 4,200 The linear polycondensate above obtained has a good compatibility with polystyrenes, polycarbonates, polytetraphthalate resins, polyphenylene oxides and polyvinyl chloride.

Example 4.

A light yellow, transparent glassy solid is obtained by the same procedure as Example 2 except using 1,176 g (3 mols) of monohydrate of 6,8-dibromo-HCA (MP 210"C), 390 g (3 mols) of itaconic acid and 390 g (3 X 1.25 mols) of neopentyl glycol.

Content of Phosphorus: 5.3% Softening Point: 1260C Approximate Molecular Weight: 5,500 The linear polycondensate above obtained has a good compatibility with polystyrenes, pofyterephthalate resins, polycarbonates, polyphenylene oxides, polymethacrylate resins and polyvinyl chloride.

Example 5.

1,294 g (3 X 1.1 mols) of monohydrate of 6,8-dibromo-HCA, 390 g (3 mols) of itaconic acid, 21.6 (3 X 0.1 mols) of acrylic acid, 312 g (3 mols) of neopentyl glycol and 75 g (3 X 0.4 mols) of ethylene glycol are charged into the same flask as in Example 2.

While slowly blowing in nitrogen gas, the flask is heated.

When the temperature of the contents reaches 1200C, they melt and water formation starts. The temperature is then slowly elevated while stirring and reaction is effected at 200"C for 2 hours. Thereafter 0.02 g of sodium methoxide are added. The water outlet is connected to a vacuum distillation port equipped with a cold trap and the flask is put under reduced pressure of 18 mm Hg.

This pressure is maintained for 2 hours ro distill out water, ethylene glycol and neopentyl glycol. Thereafter, the reaction is continued under reduced pressure of 1 mm Hg at 240"C for further two hours. The reaction products are poured into a stainless vat and cooled to solidify them. A slightly yellowish, glassy solid is thus obtained.

Content of Phosphorus: 5 5:5% Softening Point: 1210C Approximate Molecular Weight: 5,400 (According to a viscosity method) The linear polycondensate above obtained has a good compatibility with polystyrenes, polycarbonates, polyphenylene oxides, polymethacrylate resins, poly ( terephthalate 'type) resins, ABS resins and polyvinyl chloride.

Moreover, the above polycondensate is saponified and decomposed by a methanol solution of lithium hydroxide and then rendered acidic by hydrochloric acid. According to liquid chromatography, the presence of a compound of Formula I wherein R1 and R2 are bromine, the acrylic acid adduct of the compound of Formula II wherein R, and R.

are bromine, neopentyl glycol and ethylene glycol are confirmed.

Example 6.

816 g (3 mols) of 8-tert-butyl-HCA, 558 g (3 mols) of diethyl itaconate, 629 g (3 X 0.8 mols) of 2,2-dibromomethyl-1,3-propane- diol, 29 g (3 X 0.07 mols) of trimethylolpropane and 0.1 g of lead acetate are charged into the same flask as in Example 2. The flask is heated while slowly blowing in nitrogen gas. When the temperature of the contents reaches 120"C, stirring is effected and ethanol is distilled out while elevating the temperature. After reaching 1500 C, the contents are maintained at this temperature for an hour.

The water outlet is connected to a vacuum distillation port and reaction is effected under reduced pressure of 18 mm Hg for 6 hours.

The reaction products are poured into a stainless vat and cooled until solid. The yellow glassy product thus obtained is a slightly branched polycondensate.

Content of Phosphorus: 5.0 /O Softening Point: 115"C The above polycondensate has a good com patibility with polystyrene (PS) polycarbon ates (PC) and polyphenylene oxides (PPO) Moreover, the burning test and rating on the flame retardancy are effected in the same manner as in Example 1.

Amounts of Poly Resins condensate Added Rating PS 15 V-2 PS 15 V-2 PC 7 V-O PPO 5 Example 7.

958.5 g (3 mols) of 2,6,8-trichloro-HCA, 390 g (3 molt) of itaconic acid and 390 g (3 X 1.25 mols) of neopentyl glycol are charged into the same flask as in Example 2.

A light yellow, glassy product is obtained in the same manner as Example 2 except that polycondensation is effected finally at 2500C under reduced pressure of 1 mm Hg for 3 hours.

Content of Phosphorus: 6.0% Softening Molecular Point: l120C Approximate Molecular Weight: 12,000 (According to a terminal group determi- nation) The linear polycondensate above obtained has a good compatibility with polystyrene, polycarbonates, polyphenylene oxides, poly terephthalate resins, polymethacrylate resins, ABS resins, acrylonitrile-styrene copolymers and polyvinyl chloride.

Example 8.

Using rhe polycondensates of Examples 3 to 5 and 7, burning tests and flame retardancy ratings are effected in the same manner as in Example 1, using inter alia 100 parts by weight of each of acrylonitrile-styrene (AS) copolymer, polymethylmethacrylate (PMM) and ABS resin as the thermoplastic resin.

The results are given in Table 1, where in each instance the upper figure of a pair shows the amount of the polycondensate which was added (in parts by weight) and the lower symbol is the flame retardancy rating. TABLE 1

Example Resin 3 4 5 7 10 10 10 10 PS V-2 V-i. V-i V-2 10 10 10 15 AS V-I V-0 V-10 V-I 8 4 4 5 PC V-0 V-0 V-0 V-1 8 4 4 5 PAT V-0 V-0 V-0 V-0 6 3 3 5 PPO V-0 V-0 V-0 V-0 15 10 10 10 PMM V-1 V-1 V-1 V-2 7 5 5 10 PVC V-0 V-0 V-0 V-0 15 15 15 20 ABS V-1 V-0 V-0 V-0 Example 9.

To each of polystyrene (PS), acrylonitrilestyrene copolymer (AS), polycarbonate (PC) and ABS resin (ABS) are added varying amounts of various flame retardants such that the average burning times are of the same order.

Average Burning Resin Time (sec.) PS 20 PS 20 PC 10 ABS 20 As the flame retardants, the polycondensates of Examples 3 to 7 and, for comparison, tris (2,3-dibromopropyl) phosphate (TBP) and a composite flame retardant of antimony trioxide and tetrabromobisphenol A (Sb-TBA) are used.

The flame retardant resin compositions thus obtained are tested for three criteria. These are set out in each case in order in Table 2 beneath the amount (in parts by weight per 100 parts by weight of resin) of flame retardant and are, respectively: the reduction (in C. degrees) in thermal deformation temperature, the transparency of the composition to the naked eye, and the formation of hydrogen halide at a moulding temperature (2000 2800 C) suitable for each composition. The degree of hydrogen halide release is characterised as zero, slight (indicating a response to a pH test paper after a long period), fair (indicating a response to a pH test paper after a short period), or great (indicating both quick reesponse to a pH test paper and a strong odour of hydrogen halide). TABLE 2

Resin Flame PS AS | PC ABS Retardants (760C) (820C) (1350C) (820C) Example 3 15.0 16.0 4.0 16.0 .16 17 8 17 Transparent Transparent Transparent Transparent zero zero zero zero Example 4 8.0 7.5 1.8 8.0 9 6.5 3.5 9 Transparent Transparent Transparent Transparent zero zero zero zero Example 5 7.5 8.0 1.8 8.5 7 8 3.5 9 Transparent Transparent Transparent Semi-trans. zero zero zero zero Example 6 9.0 9.0 2.0 10.0 10 8.5 5 10.5 Transparent Transparent Transparent Transparent Slight Slight Slight Slight Example 7 12.0 11.0 3.5 12.0 12 10 6 13 Transparent Transparent Trans parent Transparent zero zero zero zero TBP 7.0 7.5 2.5 9.0 21 20 18 25 Transparent Transparent Transparent Semi-trans.

great great great great Sb-TBA 10.5 12.0 6.0 10.5 19 20 23 17 Opaque Opaque Opaque Opaque Slight Slight Fair Fair

Claims (7)

WHAT WE CLAIM IS:

1. A polycondensation product of a dicarboxylic acid of Formula I

wherein Rl, R2 and Ra are the same or different and are each hydrogen, halogen, alkyl, cycloalkyl, aryl or aralkyl, with a polyhydric alcohol and, if desired, a monocarboxylic acid or a monohydric alcohol.

2. A product as claimed in claim 1 wherein at least one of R1, Ra and Ra is halogen.

3. A product as claimed in claim 2 wherein R1 and Ra are each bromine and Ra is hydrogen.

4. A flame retardant composition comprising 100 parts by weight of a thermoplastic resin and 2 to 30 parts by weight of a polycondensation product as claimed in any preceding claim.

5. A composition according to claim 4 in which the thermoplastic resin is selected from polystyrene, acrylonitrile-styrene copolymers, polycarbonates, polyterephthalate resins, polyphenylene oxides, polymethacrylate resins, polyvinyl chloride and ABS resins.

6. A product as claimed in claim 1 substantially as described in any of Examples 1 to 7.

7. A composition according to claim 4 substantially as described in Example 8 or Example 9.