GB1565556A

GB1565556A - Oligomeric esters

Info

Publication number: GB1565556A
Application number: GB52218/76A
Authority: GB
Original assignee: Dynamit Nobel AG
Current assignee: Dynamit Nobel AG
Priority date: 1975-12-18
Filing date: 1976-12-14
Publication date: 1980-04-23
Also published as: SE7614158L; ES454345A1; DK519676A; IT1074223B; JPS5276352A; FR2335577A1; BE849468A; NO764292L; NL7614046A; DE2557089A1

Description

(54) IMPROVEMENTS IN OR RELATING TO OLIGOMERIC ESTERS (71) We, DYNAMIT NOBEL AKTIENGESELLSCHAFT, a German Company of 521 Troisdorf, bez Koln, Postfach 1209, 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:- This invention relates to oligomeric esters, and is particularly, but not exclusively, concerned with oligomeric esters which are suitable for incorporation with certain plastics materials as flameproofing agents.

The ready inflammability of numerous thermoplasts prevents them from being widely used, with the result that there has been no shortage of attempts to provide thermoplasts with a flameproof finish. Numerous substances have been recommended for this purpose; such substances are intended to be mixed with the thermoplasts in order to obtain the required flameproofing effect either on their own or in conjunction with other synergistically active substances.

The majority of these so-called flameproofing agents contain bound halogen, for example chlorine or bromine, especially bromine, in their molecules. Among the synergistically active substances which have been recommended, compounds of group Vb of the Periodic Classification of the Elements (such as may be found in Cotton & Wilkinson "Advanced Inorganic Chemistry", Interscience), above all Sb2O3, are preferred.

The flameproofing agents or flameproofing agent combinations used hitherto are not free from disadvantages. In many cases, they are incompatible with the thermoplasts, and adversely affect the surface finish of the articles produced therefrom or gradually diffuse out of the thermoplast, generally leaving a chalky deposit behind on the surface. This so-called chalking occurs more quickly at elevated temperature and is not only an external deficiency, but is also a serious danger since the flameproofing agent is gradually lost and articles originally classified as non-inflammable gradually lose this important property.

It is also known that some substances, in particular those with high bromine contents, such as are desirable for obtaining a useful flameproofing effect, cannot be arbitrarily exposed to high temperatures during processing because, under these conditions, they often begin to decompose and deprive the processed mixtures ol their flameproofing characteristics.

There is thus a need to provide flameproofing agents which do not show any signs of decomposition during compounding with plastics to form flameproof compositions or during further processing of such compositions into shaped articles, for example by injection moulding or extrusion, at temperatures of up to 300"C, which are simultaneously compatible with the plastics material and which, in addition, have a good flameproofing effect.

Accordingly, the present invention provides an oligomer corresponding to the general formula

where the radicals R, which may be the sarge or different represent

and n is a number from 3 to 22.

It is preferred that the number n is from 7 to 15, and in a particularly preferred embodiment the radicals R represent the isophthalic and/or terephthalic acid nucleus.

Another aspect of the present invention provides a composition comprising a plastics material other than polybutylene terephthalate and, as flameproofing agent, an oligomer as hereinbefore defined.

Certain of the oligomers according to the invention are particularly suitable for the flameproofing of moulding compositions which contain as their basic constituent a high molecular weight non-crosslinking polycondensate such as, for example, a high molecular weight linear polyester based on isophthalic and/or terephthalic acid or esterifiable derivatives thereof and diprimary glycols or glycol mixtures preferably containing from 2 to 10 carbon atoms, for example 1,3-propane diol, or a polycarbonate or a polyamide. For example the polyester used as plastics material in the compositions may be polypropylene terephthalate, and also the corresponding copolyester in which part of the terephthalic acid (TPS) is replaced by isophthalic acid (IPS), for example in a molar ratio of TPS:IPS of 70:30 to 60:40.

In one preferred embodiment, an oligomer of the invention is used as flameproofing agent in the production of transparent moulding compositions from transparent plastics materials.

Transparent plastics materials are, for example, amorphous polycarbonates or amorphous polyamides.

Preferred transparent polyamides are obtained from terephthalic acid and/or isophthalic acid or their polyester-forming derivatives, preferably their mono- or di-alkyl esters, preferably dimethyl terephthalate (DMT) and carbon-alkylsubstituted hexamethylene diamines, preferably 2,2,4- and/or 2,4,4-trimethyl hexamethylene diamine. The production of polyamides such as these is described, for example, in United States Patent Specification No. 3,150,117 and in UK Patent Specification No. 1,049,987.

In cases where it is intended to produce transparent mouldings, no other additives capable of adversely affecting transparency should be used apart from an oligomer according to the invention. However, it is possible to introduce auxiliaries which do not adversely affect transparency such as, for example, mould-release agents, for example lactones, such as ppropiolactone, and y-butyrolactone, or other standard additives, which improve the processing properties of the moulding compositions without affecting their transparency.

The flameproofing property of certain of the oligomers of the invention is surprisingly so good that, in cases where transparent amorphous polyamides and polycarbonates are used, there is no need to add a synergistically active flameproofing agent, such as for example compounds of elements of the Group Vb of the Periodic Classification of the Elements, for example antimony oxides or antimonates, or even boron compounds, zinc oxide and phosphorus-containing substances. Such agents may, of course, be used where transparency is not important.

Favourable flameproofing results are obtained with oligomers according to the invention in which the radical R consists of the isophthalic acid nucleus and the terephthalic acid nucleus. For example, it is sufficient in the case of an amorphous polyamide of DMT and 2,2,4-/2,4,4-trimethyl hexamethylene diamine (1:1), viscosity number 125 (DIN 53727, 0.5% by weight solution in m-cresol at 250C), to add only 5% by weight, based on the mixture as a whole, of an oligomeric aryl ester according to the invention having, as radicals R, nuclei of TPS and IPS in a 50::50 ratio in order to attain the highest classification of test 94 of the Underwriters Laboratories, namely VO/VO (the first measurement is made on freshly produced moulding composition, the second measurement is made after storage for 7 days at 70"C) in the absence of synergistically acting additives. Compatibility with the polyamide is so good that the original transparency is left fully intact.

Amorphous polycarbonates show similar behaviour.

The oligomeric esters of the invention may be obtained, for example, by interfacial polycondensation from tetrabromobisphenol A and the dichloride of isophthalic and/or terephthalic acid. The terminal groups of the ester obtained may be closed by the addition of suitable mono-functional substances to the suspension, such as tribromophenol for example. Polycondensation is preferably carried out in such a way that oligomers with a melting range above 250"C, preferably above 300"C, corresponding to a molecular weight of from 4000 to 15,000, preferably from 5000 to 10,000, as measured by gel chromatography, are obtained.

Oligomers according to the invention have been found to be particularly suitable flameproofing agents for thermoplasts which require high processing temperatures during the production of plastics compositions and during further processing into mouldings. By virtue of their high thermal stability, oligomers according to the invention may be used in particular for the production of flameproofed moulding compositions which are intended to be processed, into mouldings that are exposed to comparatively high thermal stressing during use, for example during their use in electrical engineering.

In order to obtain a measure of the compatibility of the oligomers according to the invention with the plastics materials used as thermoplasts, it has been found that injected strips of an oligomer/thermoplast composition measuring 127x 12.7x 1.6 mm may be heated for example in air for 7 days to 700C or 150"C without even the slightest trace of chalking being observed. Even after storage for 28 days at 1500C, the test specimens had lost none of their flameproof finish and still attained the classification VO in UL test 94. Weighing of the test specimens before and after storage for 28 days at 1500C showed reductions in weight of only 0.2 to 0.40/,, which indicates that the oligomer remained in the thermoplast even under extreme conditions.

The compositions according to the invention, which preferably contain from 3 to 20'to by weight, more preferably from 5 to 15% by weight, of bligomer, may also be modified by additives. In particular, reinforcing agents or fillers, such as glass fibres, whiskers, asbestos, talcum or chalk which improve certain properties of the thermoplasts in known manner, may be added in the usual concentrations.

The oligomers according to the invention have been found to be particularly suitable for flameproofing polytrimethylene terephthalates filled with glass fibres.

In the case of moulding compositions such as these, it is preferred to use a synergistically active agent, for example antimony trioxide, preferably in a quantity of from 2 to 6% by weight, based on the mixture as a whole. The oligomer may be added to the basic plastics component separately from the other additives or even together with them.

The oligomer and plastics material and, optionally, other additives may be compounded, for example, by means of a double screw extruder (Werner und Pfleiderer ZDSK 28) with a kneading and mixing zone. For example, they may be compounded in the above-mentioned extruder at the following temperatures: Zone 1 (feed zone) 220"C, Zone 22400 C, Zone 3 250"C, Zone 4 250"C, Zone 5 250"C, Zone 6 (nozzle) 230"C.

Depending upon the softening ranges of the plastics material used in the compositions of the invention, the temperatures in the mixers used may be below 220"C or even above 250"C, for example 280"C, according to requirements.

The following Examples illustrate the invention. UL Test 94 (Underwriters Laboratories USA) mentioned therein is carried as follows: A test specimen (5 inches long, 1/2 inch wide, 1/8 to 1/!6 inch thick) arranged vertically in a protective box, is exposed from below to a defined burner flame for 10 seconds. The fire classes VO, VI and VII are defined as follows: VO: No afterburning beyond 10 seconds; means afterburning time no more than 5 seconds; afterglow no more than 30 seconds.

VI: No afterburning beyond 30 seconds, means afterburning time no more than 25 seconds; afterglow no more than 60 seconds.

VII: When under the above conditions burning droplets set fire to lint.

Failed: Afterburning time beyond 30 seconds, mean value beyond 25 seconds.

The extinguished end is exposed once more to the burner flame.

The test is carried out on specimens which have been stored for 48 hours at 230C/5000 humidity and is repeated on test specimens which have been stored for 168 hours at 700 C.

Reduced viscosity referred to in the Examples is calculated in accordance with the following formula: 77,,d'(11oi)X l/C, where rj is the viscosity of the solvent (60 parts by weight of phenol+40 parts by weight of I,1,2,2-tetrachloroethane), 77o=viscosity of the solution and c=concentration of the solution (1 g/100 cc), measured at 250C.

EXAMPLE 1 Production of the bromine-containing polyaryl ester based on tetrabromobisphenol A and iso-/terephthalic acid dichloride.

54.4 g (0.1 mole) of tetrabromobisphenol A and 8 g (0.2 mole) of sodium hydroxide were dissolved in 120 ml of water with salt formation. A solution of 10.15 g (0.05 mole) of isophthalic acid dichloride and 10.15 g (0.05 mole) ot terephthalic acid dichloride in 15 ml of chloroform was added all at once with vigorous stirring.

A stirrable polyaryl ester suspension was formed, its formation being accompanied by spontaneous heating of the reaction mixture. After the reaction had abated, the reaction mixture was stirred for 3 hours at room temperature, filtered under suction and washed first with methanol and then with water until free from chloride.

After drying at up to 1500C, 65.3 g of powder-form colourless polyaryl ester were obtained, corresponding to a yield of 97%. The product dissolved in chlorinated aliphatic hydrocarbons to form clear solutions without any residue.

The reduced specific viscosity was 0.13.

The reduced specific viscosity 17 spec.

c was calculated in accordance with the following formula: t-to 11 spec.= to where t=throughflow time of the solution, tO=throughflow time of the solvent; c=concentration of the solution (1 g/100 cc), as measured at 250C in chloroform.

EXAMPLE 2 95 parts of amorphous polyamide, commercially available under the name Trogamid T, viscosity number (DIN 53727)=125, and 5 parts of oligomeric tetrabromobisphenol A-terephthalic acid ester of molecular weight 7000, produced with tribromophenol to close the terminal groups, were mixed together. The resulting mixture was extruded into a 3 mm diameter strand in a double screw extruder with a mixing zone and kneading block at temperatures in the range from 260 to 280"C. The strand was chopped into granulate and the granulate thus obtained was injection moulded into test specimens measuring 127x12.7x1.6 mm.

The test specimens had the same high transparency as the pure Trogamid T.

EXAMPLE 3 92 parts of polycarbonate, commercially available under the name Macrolon 3000, and 8 parts of oligomeric ester of tetrabromobisphenol A and a mixture of 50 mole % of isophthalic acid and 50 mole % of terephthalic acid, molecular weight 8200 were processed into test specimens at 25O2700C in the same transparency as the pure polycarbonate.

The test specimens obtained in accordance with Examples 2 and 3 were subjected to UL Test 94 both before and after storage for 7 days at 700 C. In each case, for each specimen, a test rating of VO was obtained. The surface condition of the test specimens was found to be unchanged after 7 days at 70"C.

WHAT WE CLAIM IS: 1. An oligomer corresponding to the general formula

where the radicals R, which may be the same or different, represent

and n is a riumber from 3 to 22.

2. An oligomer according to Claim 1, wherein n is a number from 7 to 15.

3. An oligomer according to Claim 1 or 2, wherein R represents the terephthalic acid nucleus

4. An oligomer according to Claim 1, 2 or 3, wherein the radical R represents the isophthalic acid nucleus

5. An oligomer according to any one of the preceding claims which has a melting point greater than 250"C.

6. An oligomer according to any one of the preceding claims which has a melting point greater than 350"C.

7. An oligomer according to any one of the preceding claims which has a molecular weight of from 4000 to 15000.

8. An oligomer according to Claim 7 which has a molecular weight of from 5000 to 10000.

9. An oligomer according to any one of the preceding claims and having tribromophenolate terminal groups.

10. An oligomer according to any one of the preceding claims when produced by interfacial polycondensation.

11. An oligomer according to Claim 1 substantially as described in any one of the Examples.

12. A composition comprising a plastics material and other than polybutylene terephthalate, as flameproofing agent, an oligomer according to any one of the preceding claims.

13. A composition according to Claim 12 which contains from 3 to 20% by weight of the olig6mer.

14. A composition according to Claim 13 which contains from 5 to 15% by weight of the oligomer.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. case, for each specimen, a test rating of VO was obtained. The surface condition of the test specimens was found to be unchanged after 7 days at 70"C. WHAT WE CLAIM IS:

1. An oligomer corresponding to the general formula

where the radicals R, which may be the same or different, represent

and n is a riumber from 3 to 22.

2. An oligomer according to Claim 1, wherein n is a number from 7 to 15.

15. A composition according to Claim 12, 13 or 14, wherein the plastics

material is a thermoplastic linear polyester.

16. A composition according to Claim 15, wherein the polyester is polypropylene terephthalate.

17. A composition according to Claim 12, 13 or 14, wherein the plastics material is a transparent polyamide.

18. A composition according to Claim 17, wherein the polyamide comprises structural units based on terephthalic acid and carbon-alkyl substituted hexamethylene diamine.

19. A composition according to Claim 12, 13 or 14, wherein the plastics material is a transparent polycarbonate.

20. A composition according to any one of Claims 12 to 19 which additionally includes a synergistically active agent.

21. A composition according to Claim 20, wherein the synergistically active agent is antimony trioxide.

22. A composition according to Claim 12 substantially as described in Example 2 or 3.

23. An article whenever formed from a composition according to any one of Claims 12 to 22.