GB1558775A - Non-flammable moulding compositions - Google Patents

Description

(54) NON-FLAMMABLE MOLDING COMPOSITIONS (71) We, BASF AKTIENGESELLSCHAFT, A German Joint Stock Company of 6700 Ludwigshafen, Federal Republic of Germany, do hereby declare 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 particularly described in and by the following Statement:- The present invention relates to non-flammable molding comositions of linear polyesters based on terephthalic acid and aliphatic saturated diols.

Methods of rendering linear polyesters flame-resistant are well known. One such method consists in manufacturing a polyester containing a flame retardant as an integral part of its chemical structure. An example of such an agent is 2,5dibromoterephthalic acid, which may be built into the molecular structure of the polyester to render the latter flame-resistant. However, this suffers from the drawback that a relatively large amount of halogen is necessary to render the polyester adquately flame-resistant. This is undesirable for physiological reasons.

Furthermore, high halogen contents lead to strong discoloration of the products at the high manufacturing temperatures normally used. Another method of increasing the flame resistance of polyesters is to incorporate into the polyester compounds such as halogen, phosphorus or metal compounds, e.g. by physical mixing or fixing methods. Thus it is known to blend linear polyesters with aromatic polyphosphates.

However, relatively high phosphorus contents are necessary to effect satisfactory flame retardance for most applications. When such high contents of phosphorus compounds are used, it is difficult to avoid impairment of the physical and chemical properties and the processability of the polyesters.

The present invention seeks to provide novel flame-retardant thermoplastic polyester molding compositions of improved properties over the prior art.

According to the present invention there is provided a non-flammable molding composition prepared by blending (a) an ingredient A consisting of a copolyester or a mixture of polyesters, the acid component of the copolyester or the mixture consisting of from I to 99% molar of halogenated terephthalic acid units and from 99 to 1% molar of unsubstituted terephthalic acid units and the alcohol component of the copolyester or the mixture consisting of an aliphatic saturated diol or a mixture of aliphatic saturated diols; and (b) from 0.1 to 10% by weight, based on ingredient A, of an ingredient B consisting of one or more polyphosphonates having a degree of polymerization of at least 6 and derived from at least one dihydric phenol or naphthol of the formula

where Y denotes alkyl or halogen, n is zero or an integer, the symbols Y being identical or different when n is more than 1, and X denotes SO2, SO, SO2NH, O, S, CO, CONH or branched or unbranched alkyl of the formula

in which R and R' are the same or different and denote hydrogen or alkyl of from 1 to 6 carbon atoms, as diol component, and from at least one phosphonic acid derivative of the general formula

where R denotes alkyl, phenyl, or a heterocyclic radical which may or may not contain halogen, V denotes halogen, an ester group or hydroxyalkyl, and W denotes halogen, an ester group or hydroxyalkyl, as acid component.

Preferably, sufficient of the ingredient B is used that the composition contains 0.1 to 4 2n by weight of phosphorus.

According to a preferred process, the molding compositions of the invention are prepared by adding ingredient B to ingredient A only after polycondensation of the latter is complete. Ingredient B may thus be added to the melt after the polycondensation reaction by means of suitable equipment, the sucess of the process being independent of whether the said polycondensation of ingredient A is carried out by a continuous or batchwise process.

The ingredient A may be obtained by various methods. It may be prepared by forming a random copolyester by cocondensation of all the monomeric starting materials. This may be effected in known manner by reacting, say, bis(2hydroxyethyl)terephthalate or a polyester prepolymer thereof with 2,5dibromoterephthalic acid. Alternatively, a mixture of dimethyl terephthalate and 2,5-dibromodimethyl terephthalate may be transesterified- with an alkanediol, whereupon the transesterification product is subjected to condensation polymerization. The ingredient A may also be obtained by direct esterification between terephthalic acid, 2,5-dihaloterephthalic acid and diol. The reaction polyester formation may be assisted by the use of conventional catalyst systems, preferably tetraalkyl titanate esters.Another method of preparing ingredient A is to use a homopolyester based on unsubstituted terephthalic acid together with a homopolyester based on halo-substituted terephthalic acid. In a preferred process, the two polyesters are blended, after completion of their polycondensation, in the molten state at temperatures of from 250"C to 3000C in vacuo.

In a special embodiment of the invention, which is particularly preferred, conventional PVC-stabilizers are used in the preparation of ingredient A. The use of such stabilizers improves the manufacture of copolyesters based on, say, dimethyl terephthalate and nuclear-halogenated dimethyl terephthalate and also the manufacture of a homopolyester based on nuclear-halogenated dimethyl terephthalate alone, since the presence of these stabilizers substantially prevents damage to the product by free hydrogen halide or free halogen liberated during the end phase of the condensation under the influence of the temperatures used at that stage. Thus it is possible to produce polyesters of type A having high bromine contents and nevertheless high molecular weight.

The ingredient B may be a single polyphosphonate or a mixture of polyphosphonates. The polyphosphonates may be homopolymers or copolymers of a plurality of diols and/or a plurality of phosphonic acids. Where at least two diols are present a variety of preparative methods may be used. One such method comprises copolycondensation of all the various monomers to form a random copolyester having a degree of polymerization of at least 6. Another process involves formation of the ingredient B by blending two or more individual polyesters in the molten state.

Where only one diol is used, any of the well-known methods of preparing polyesters may be employed.

In a special embodiment the blending of the ingredients A and B is carried out in the presence of a PVC stabilizer. Conventional stabilizers may be used. This largely prevents damage to the material or destruction thereof.

The molding compositions of the invention may be converted to, say, fibers and films. Such processing operations are also advantageously carried out in the presence of PVC stabilizers. It is also possible, if desired, to add conventional additives such as delustrants or dyes or further flame retardants.

A particular advantage of the invention is that the halogen-containing ingredient A and the phosphorus-containing ingredient B have a synergistic effect on each other in achieving flame retardance. In order to obtain a given degree of flame retardance, it is sufficient to tise relatively low concentrations of the two flameproofing ingredients, i.e. the halogen-containing terephthalic units in A together with phosphorus-containing units B, whereas if only one such flameproofing ingredient is used, a much higher concentration is required in order to achieve the same results.

Shaped articles prepared from the molding compositions of the invention are distinguished by extremely good flame-retardant properties, the physical and chemical properties of the polyester being unimpaired or only insignificantly impaired.

The following Examples illustrate the invention.

The relative viscosities viral of the polyesters given in the Examples below are those determined on a 3:2 mixture of phenol and o-di-chlorobenzene. The melting points were determined using a heated microscope, but can also be determined by the DSC method.

The criterion used in the Examples for assessing the flame retardance of the molding compositions of the invention and of the substances used for comparison was the test method UL 94 proposed by Underwriters' Laboratories, In this test, a flat test specimen is suspended vertically at its top end, whilst its bottom end is flamed twice for periods of ten seconds. The results of the burning tests are listed in Table 1 below.

Percentage compositions in the Examples are by weight.

EXAMPLE 1 (a) Preparation of Ingredient A: A mixture of 1843 parts of dimethyl terephthalate, 175.9 parts of 2,5dibromodimethyl terephthalate, 1240 parts of ethylene glycol, 0.4 part of Mn(OAc)2, 1.2 parts of Sb(OAc)3 and 20 parts of lead stearate is heated at 2200C over a period of two hours, during which period methanol is distilled off.

This prepolymer is then polycondensed, the pressure Reing gradually reduced from atmospheric to less than 1 mm of Hg, whilst a condensation temperature of 260"C is reached.

There is obtained a polyester having a relative viscosity of 1.402 and a melting point of 246"C. The bromine content is 3.1%.

(b) Preparation of Ingredient B: A mixture of 195 parts of phenyldichlorophosphine oxide, 97 parts of dihydroxydiphenyl ether, 120 parts of bis(4-hldroxyphenyl)sulfone and 2.0 parts of Cadiz is heated at 1 800C under a stream of nitrogen over a period of 1.5 hours.

The mixture is then heated up to 2200C and further condensed under reduced pressure (1 mm Hg) while the temperature is raised to 2600C.

There is obtained a solid brown substance having a molecular weight of 10,800 and a relative viscosity of 1,140. Its melting point is l700-1800C and its phosphorus content is 8.2%.

(c) Blending of Ingredients A and B: 50 parts of the pulverized ingredient B and 1.1 parts of lead stearate are added, under nitrogen, to the fully polycondensed, molten ingredient A (1000 parts) and are stirred into the melt for 5 minutes at atmospheric pressure and then for 5 minutes at a reduced pressure of less than 1 mm of Hg, the mixture being finally cooled. There is obtained a flame-retardant polyethylene terephthalate having a relative viscosity of 1.384 and a melting point of 241"C. The bromine content is 2.9 /n and the phosphorus content is 0.39%.

COMPARATIVE EXAMPLE IA A mixture of 1,745 parts of dimethyl terephthalate, 351.8 parts of 2,5 dibromodimethyl terephthalate, 1,240 parts of ethylene glycol, 0.4 part of Mn(OAc)z, 1.2 parts of Sb(OAc)3 is heated at 2200C over a period of 2 hours, during which period methanol is distilled off.

This prepolymer is then polycondensed, the pressure being gradually reduced from atmospheric to less than 1 mm of Hg, while the condensation temperature reaches a final value of 260 C. There is obtained a polyester having a relative viscosity of 1.363 and a melting point of 231"C. The bromine content is 6.3S.

COMPARATIVE EXAMPLE 1B 100 parts of the ingredient B described under Example lb are added, in pulverized form, to 1000 parts of molten polyethylene terephthalate under nitrogen and are stirred into the melt for 5 minutes at atmospheric pressure and then for 5 minutes under a reduced pressure of less than 1 mm of Hg, the mixture being finally cooled. There is obtained a product having a relative viscosity of 1,372, a melting point of 245"C and phosphorus content of 0.74 zÓ.

EXAMPLE 2 (a) Preparation of Ingredient A: 585 parts of 2,5-dibromodimethyl terephthalate, 225 parts of ethylene glycol, 0.5 part of tetrabutyl ortho-titanate and 5.8 parts of lead stearate are heated at 220"C over 2 hours, during which period methanol is distilled off.

This prepolymer is then polycondensed, the pressure being gradually reduced from atmospheric to less than 1 mm of Hg. The final condensation temperature achieved is 225"C. There is obtained a polyester having a relative viscosity of 1.323 and a melting point of 200"C. The bromine content is 41.7 / 50 parts of the resulting polyester are added to 1000 parts of molten polyethylene terephthalate under nitrogen and are stirred into the melt for 5 minutes at atmospheric pressure and then for 5 minutes under a reduced pressure of less than 1 mm of Hg. The resulting ingredient A has a relative viscosity of 1.390 and a bromine content of 2%.

(b) Preparation of Ingredient B A mixture of 195 parts of phenylphosphonic acid dichloride, 532 parts of 2,2bis(3,5-dibromo-4-hydroxyphenyl)propane and 1.0 part of CaCI2 in 0.5 1 of 1,1,2,2tetrachloroethane is heated over 4 hours to the boiling temperature of tetrachloroethane. The mixture is then heated under reflux for 15 hours, and after cooling added dropwise to about 4 1 methanol. The precipitate thus formed is filtered off and dried. The white powder obtained in this manner has a molecular weight of 6,400 and a melting point of 175"C. Its phosphorus content is 4.7% and its bromine content is 46.6%.

(c) Blending of Ingredients A and B: 50 parts of the pulverized ingredient B and 1.1 part of lead stearate are added to the fully polycondensed molten ingredient A (1000 parts) under nitrogen and are stirred into the melt for 5 minutes at atmospheric pressure and then for 5 minutes at a reduced pressure of less than 1 mm of Hg, the mixture being finally cooled. There is obtained a flame-retardant polyethylene terephthalate having a relative viscosity of 1.384. Its melting point is 241"C, its bromine content 2.9"' and its phosphorus content 0.39%.

TABLE 1 Result of burning test UL 94 (Underwriters' Laboratories) Burning time Ex. No. of specimen Remarks 1 0 Non-flammable, melts away from flame IA 8 releases burning drops I B 2 readily releases drops which burn for a brief period 2 0 non-flammable, melts away from flame WHAT WE CLAIM IS: 1. Non-flammable molding compositions prepared by blending (a) an ingredient A, consisting of a copolyester or a mixture of polyesters, the acid component of the copolyester or the mixture consisting of from 1 to 99% molar of halogenated terephthalic acid units and from 99 to 1% molar of unsubstituted terephthalic acid units and the alcohol component of the copolyester or the mixture consisting of an aliphatic saturated diol or a mixture of aliphatic saturated diols; and (b) from 0.1 to 10% by weight, based on ingredient A, or an ingredient B, consisting of one or more polyphosphonates having a degree of polymerization of at least 6 and derived from at least one dihydric phenol or naphthol of the formula

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (9)

**WARNING** start of CLMS field may overlap end of DESC **. COMPARATIVE EXAMPLE 1B 100 parts of the ingredient B described under Example lb are added, in pulverized form, to 1000 parts of molten polyethylene terephthalate under nitrogen and are stirred into the melt for 5 minutes at atmospheric pressure and then for 5 minutes under a reduced pressure of less than 1 mm of Hg, the mixture being finally cooled. There is obtained a product having a relative viscosity of 1,372, a melting point of 245"C and phosphorus content of 0.74 zÓ. EXAMPLE 2 (a) Preparation of Ingredient A: 585 parts of 2,5-dibromodimethyl terephthalate, 225 parts of ethylene glycol, 0.5 part of tetrabutyl ortho-titanate and 5.8 parts of lead stearate are heated at 220"C over 2 hours, during which period methanol is distilled off. This prepolymer is then polycondensed, the pressure being gradually reduced from atmospheric to less than 1 mm of Hg. The final condensation temperature achieved is 225"C. There is obtained a polyester having a relative viscosity of 1.323 and a melting point of 200"C. The bromine content is 41.7 / 50 parts of the resulting polyester are added to 1000 parts of molten polyethylene terephthalate under nitrogen and are stirred into the melt for 5 minutes at atmospheric pressure and then for 5 minutes under a reduced pressure of less than 1 mm of Hg. The resulting ingredient A has a relative viscosity of 1.390 and a bromine content of 2%. (b) Preparation of Ingredient B A mixture of 195 parts of phenylphosphonic acid dichloride, 532 parts of 2,2bis(3,5-dibromo-4-hydroxyphenyl)propane and 1.0 part of CaCI2 in 0.5 1 of 1,1,2,2tetrachloroethane is heated over 4 hours to the boiling temperature of tetrachloroethane. The mixture is then heated under reflux for 15 hours, and after cooling added dropwise to about 4 1 methanol. The precipitate thus formed is filtered off and dried. The white powder obtained in this manner has a molecular weight of 6,400 and a melting point of 175"C. Its phosphorus content is 4.7% and its bromine content is 46.6%. (c) Blending of Ingredients A and B: 50 parts of the pulverized ingredient B and 1.1 part of lead stearate are added to the fully polycondensed molten ingredient A (1000 parts) under nitrogen and are stirred into the melt for 5 minutes at atmospheric pressure and then for 5 minutes at a reduced pressure of less than 1 mm of Hg, the mixture being finally cooled. There is obtained a flame-retardant polyethylene terephthalate having a relative viscosity of 1.384. Its melting point is 241"C, its bromine content 2.9"' and its phosphorus content 0.39%. TABLE 1 Result of burning test UL 94 (Underwriters' Laboratories) Burning time Ex. No. of specimen Remarks

1 0 Non-flammable, melts away from flame IA 8 releases burning drops I B 2 readily releases drops which burn for a brief period

2 0 non-flammable, melts away from flame WHAT WE CLAIM IS: 1.Non-flammable molding compositions prepared by blending (a) an ingredient A, consisting of a copolyester or a mixture of polyesters, the acid component of the copolyester or the mixture consisting of from 1 to 99% molar of halogenated terephthalic acid units and from 99 to 1% molar of unsubstituted terephthalic acid units and the alcohol component of the copolyester or the mixture consisting of an aliphatic saturated diol or a mixture of aliphatic saturated diols; and (b) from 0.1 to 10% by weight, based on ingredient A, or an ingredient B, consisting of one or more polyphosphonates having a degree of polymerization of at least 6 and derived from at least one dihydric phenol or naphthol of the formula

where Y denotes alkyl or halogen, n is zero or an integer, the symbols Y being identical or different when n is more than 1, and X denotes SO2, SO, SO2NH, O, S, CO, CONH, or branched or unbranched alkyl of the formula

in which R and R' are the same or different and denote hydrogen or alkyl of from I to 6 carbon atoms, as diol component, and from at least one phosphonic acid derivative of the general formula

where R denotes alkyl, phenyl, or a heterocyclic radical, V denotes halogen, an ester group or hydroxyalkyl, W denotes halogen, an ester group or hydroxyalkyl, as the acid component.

2. Non-flammable molding compositions as claimed in claim 1, wherein ingredients A and B are prepared by cocondensation of the monomers to form the random copolyester or by preparing the copolyester by blending the homopolyesters in the molten state.

3. Non-flammable molding compositions as claimed in claim 1 or 2 which contain a stabilizer for polyvinyl chloride.

4. Non-flammable molding compositions as claimed in claim 3, wherein the ingredient A is prepared in the presence of a stabilizer for polyvinyl chloride.

5. Non-flammable molding compositions as claimed in claims 3 or 4, wherein a stabilizer for polyvinyl chloride is present during blending of ingredients A and B.

6. Non-flammable molding compositions as claimed in any of claims I to 5 which additionally contain a delustrant, a dye and/or a further flame retardant with or without other additives.

7. Non-flammable molding compositions as claimed in any of claims 1 to 6, wherein the amount of ingredient B present is sufficient to provide a phosphorus content of 0.1 to 4% by weight.

8. Non-flammable molding compositions as claimed in claim 1 and substantially as described in either of the foregoing Examples I and 2.

9. Non-flammable moldings made from molding compositions as claimed in any of claims 1 to 8.