GB1592813A

GB1592813A - Stabilised flameproofed thermoplastic moulding compositions

Info

Publication number: GB1592813A
Application number: GB2958/78A
Authority: GB
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 1977-01-26
Filing date: 1978-01-25
Publication date: 1981-07-08
Also published as: DE2703052A1; IT1103259B; IT7847693A0; DE2703052C2; FR2378817A1; FR2378817B3

Description

(54) STABILIZED, FLAMEPROOFED THERMOPLASTIC 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 thermoplastic molding compositions, flameproofed with red phosphorus.

German Published Application DAS 1,931,387 discloses that the addition of red phosphorus to thermoplastics, above all to reinforced or filled nylons, gives effective fire protection. However, under adverse conditions, e.g. elevated temperature, high humidity or the presence of alkali or oxygen, red phosphorus tends to form decomposition products, e.g. phosphine and acids of phosphorus.

Even small amounts or traces of heavy metals catalyze the formation of these decomposition products. It is true that red phosphorus incorporated into a thermoplastic, e.g. nylon, is substantially protected against thermo-oxidation as a result of being embedded in the polymer, but even in this case decomposition products may form in the longer term. This is a disadvantage since, for example, phosphine formed when granules are injection molded may lead to odor nuisance and is, furthermore, toxic; the acids of phosphorus, formed at the same time, may separate out on the surface of injection moldings, which, above all, lowers the cracking resistance of the moldings.

There has therefore been no lack of attempts to improve the stability of the red phosphorus employed as a flameproofing agent for plastics. For example, some stabilizing action is achievable by adding oxides or hydoxides of zinc, magnesium or aluminum. U.S. Patent 3,806,488 discloses the stabilizing action of complexing agents, e.g. ethylenediaminetetraacetic acid and its esters or alkali metal salts.

However, the stabilizing action of these complexing agents is not satisfactory in every case, and strongly alkaline salts of the complexing agents may also damage the red phosphorus.

The present invention seeks to provide for the effective stabilization of red phosphorus by means of a stabilizer which if possible is very stable at the processing temperatures of the molding compositions and can be homogeneously dispersed in the plastic melt.

According to the present invention there is provided a molding composition of a thermoplastics material which contains red phosphorus as a flameproofing agent together with from 0.1 to 20 /n by weight, based on the red phosphorus, of a metal salt of a chelate-forming aminoacetic acid as a stabilizer, wherein the stabilizer is a magnesium or aluminum salt.

The thermoplastics materials to be flameproofed are preferably polycondensates or poly addition products. Specific examples of suitable thermoplastics materials are: 1. Nylons, preferably saturated linear nylon homopolymers, e.g.

polycaprolactam (nylon 6), polyhexamethylene adipamide (nylon 6,6), polyhexamethylene sebacamide, polylauryl-lactam and polyundecanamide, as well as nylon homopolymers and copolymers obtained by using adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid and terephthalic acid, on the one hand, and hexamethylenediamine, trimethylhexamethylenediamine, bis - (4 aminocyclohexyl) - methane or 2,2 - bis - (4' - aminocyclohexyl) - propane on the other hand, and also nylon copolymers which are obtained by polycondensation of lactams together with the above dicarboxylic acids and diamines.

2. Polyesters, especially linear thermoplastic polyesters obtained from aromatic or aliphatic carboxylic acids, e.g. terephthalic acid, isophthalic acid, phthalic acid or adipic acid, on the one hand, and glycols, e.g. ethylene glycol, propylene glycol, butylene glycol or neopentylglycol, on the other hand, polybutylene terephthalate and polyethylene terephthalate being preferred.

3. Polyurethanes, especially linear thermoplastic polyurethanes obtained from aromatic or aliphatic diisocyanates, e.g. diphenylmethane diisocyanate or hexamethylene diisocyanate and hydroxylic polyesters or polyethers, with or without diols, e.g. butanediol, as chain extenders.

4. Polycarbonates obtained from phosgene and dihydroxydiphenylalkanes, preferably dihydroxydiphenylpropane.

Examples of the stabilizers used according to the invention are salts of: (1) 1 mole of Mg2+ and I mole of ethanolaminediacetic acid (2) 2 moles of Mg2+ and 1 mole of ethylenediaminetetraacetic acid (3) 3 moles of Mg2+ and 2 moles of nitrilotriacetic acid (4) 1 mole of Al3+ and 1 mole of ethanolaminediacetic acid (5) 2 moles of Al3+ and I mole of ethylenediaminetetraacetic acid (6)1 mole of Awl3+ and I mole of NH4+ with 1 mole of nitrilotriacetic acid.

A stabilizer which is obtained by reacting nitriloacetic acid with aluminum copounds, e.g. aluminum chloride or aluminum sulfate, in the presence of ammonia, is particularly preferred.

The amounts of stabilizer employed, based on red phosphorus, are from 0.1 to 20% by weight, preferably from 1 to 5% by weight. The stabilizer can either be mixed mechanically with the red phosphorus or be precipitated onto the phosphorus particles by manufacturing it in the presence of a phosphorus slurry. Of course it is also possible to add the stabilizers directly to the melt whilst working the phosphorus into the plastic.

For fireproofing, the red phosphorus is preferably employed in amounts of from 1 to 12% by weight, especially from 3 to 7% by weight, based on the total molding composition. The red phosphorus can be a commercial grade or a grade which has already been pre-stabilized with another stabilizer; however, phosphorus concentrates, e.g. in caprolactam, paraffin oil, dioctyl phthalate or nylon, containing from 20 to 90 /n of red phosphorus, may also be employed. The mean size of the phosphorus particles dispersed in the plastic should preferably be from 0.0001 to 0.5 mm, especially from 0.001 to 0.2 mm in diameter.

Suitable fillers are glass fibers, preferably of E-glass, which may be provided with a size and an adhesion promoter and are employed in amounts of from 10 to 60 /" by weight, based on the total molding composition. The fibers may have a diameter of from 8 to 20 um whilst the mean glass fiber length in the iniection molding is preferably from 0.1 to 0.5 mm. Further suitable fillers are laminar silicates, e.g. talc and mica, where the mean flake diameter may be from 5 to 200 m and the mean flake thickness from 0.01 to 10 ,um. Other suitable fillers are glass beads, wollastonite, asbestos, kaolin, quartz and chalk.

The molding compositions according to the invention may also contain conventional additives, e.g. dyes, stabilizers, lubricants and processing assistants.

To manufacture the mixtures according to the invention, the red phosphorus, with or without any fillers, is worked into the plastic melt by conventional methods on extruders or other suitable kneaders or mixers, for example by the method described in U.S. Patent 3,304,282. The phosphorus stabilizers can in such cases be added directly to the melt or can beforehand be mixed with, or precipitated on, the red phosphorus, but can also be applied to the plastic granules before working in.

To test the effectiveness of the phosphorus stabilizers, moldings of a defined surface area were injection molded from the granules obtained and the evolution of phosphine from these was measured over a prolonged period.

EXAMPLES Nylon 6,6 having a K value of 72 was fused on a twin-screw extruder at 2800C.

Glass fibers in the form of 6 mm long chopped strands, the phosphorus stabilizer and the red phosphorus in the form of a 20% strength by weight concentrate in nylon 6,6 were added through a downstream orifice. The amount of glass fibers worked in was 35 /n by weight and the amount of red phosphorus employed was 6% by weight, in each case based on the total mixture. The stabilizers listed in Table I were added in such amount that the concentration in the end product was 0.2% by weight, based on the end product. The mixture was extruded through dies, drawn off as strands, cooled and granulated.

Standard bars of size 4x6x50 mm were injection-molded from the granules.

Batches of 100 of these bars, freshly injection molded, were placed in a gas-tight glass flask, 5% by weight of distiiled water, based on the total amount of the moldings, were added, the flask was flushed with oxygen and the pressure was then reduced to 0.6 bar. The amount of phosphine which formed in the flask was determined after 20, 40 and 60 days by means of Trtger tubes (phosphine type 50/a from Trigerwerk AG, Lübeck). After each measurement, the flask was flushed first with nitrogen and then with oxygen and the pressure was then again reduced to 0.6 bar. The sum of the phosphine contents measured after 20,40 and 60 days served as a guideline value for assessing the effectiveness of the phosphorus stabilizer used (Table 2).

TABLE 1 Stabilizers used 1. None (comparative experiment) 2. Magnesium oxide 3. Aluminum oxide 4. Na nitrilotriacetate 5. Na ethylenediaminetetraacetate 6. Compound from 1 mole of Mg2+ and 1 mole of ethanolaminediacetic acid.

7. Compound from 2 moles of Mg2+ and 1 mole of ethylenediaminetetraacetic acid.

8. Compound from 3 moles of Mg2+ and 2 moles of nitrilotriacetic acid.

9. Compound from I mole of Al3+ and one mole of ethanolaminediacetic acid.

10. Compound from 2 moles of Al3+ and one mole of ethylenediaminetetraacetic acid.

I I. Compound from 1 mole of A13+ and 1 mole of NH4+ and one mole of nitriloacetic acid.

TABLE 2 Amounts of Phosphine measured Amount of phosphine produced in ppm after Ex. Stabilizer 20 days 40 days 6U days 1 1 200 450 700 2 2 180 400 600 3 3 200 380 520 4 4 210 390 650 5 5 200 420 730 6 6 150 300 500 7 7 150 270 420 8 8 130 270 400 9 9 100 200 310 10 10 80 150 200 11 11 100 160 180 As may be seen from Table 2, on comparing Examples 6-11 with Comparative Examples 1--5, the amount of phosphine measured is substantially less in the presence of the phosphorus stabilizers according to the invention.

WHAT WE CLAIM IS: 1. A molding composition of a thermoplastics material, which contains red phosphorus as a flameproofing agent and from 0.1 to 20% by weight, based on the red phosphorus, of a magnesium or aluminum salt of a chelate-forming aminoacetic acid as a stabilizer.

2. A molding composition as claimed in claim 1, wherein the thermoplastics material is a polycondensate or polyaddition product.

3. A molding composition as claimed in claim I or 2, wherein the thermoplastics material is nylon 6 or nylon 6,6.

4. A molding composition as claimed in any of claims 1 to 3, wherein the

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. worked in was 35 /n by weight and the amount of red phosphorus employed was 6% by weight, in each case based on the total mixture. The stabilizers listed in Table I were added in such amount that the concentration in the end product was 0.2% by weight, based on the end product. The mixture was extruded through dies, drawn off as strands, cooled and granulated. Standard bars of size 4x6x50 mm were injection-molded from the granules. Batches of 100 of these bars, freshly injection molded, were placed in a gas-tight glass flask, 5% by weight of distiiled water, based on the total amount of the moldings, were added, the flask was flushed with oxygen and the pressure was then reduced to 0.6 bar. The amount of phosphine which formed in the flask was determined after 20, 40 and 60 days by means of Trtger tubes (phosphine type 50/a from Trigerwerk AG, Lübeck). After each measurement, the flask was flushed first with nitrogen and then with oxygen and the pressure was then again reduced to 0.6 bar. The sum of the phosphine contents measured after 20,40 and 60 days served as a guideline value for assessing the effectiveness of the phosphorus stabilizer used (Table 2). TABLE 1 Stabilizers used

1. None (comparative experiment)

2. Magnesium oxide

3. Aluminum oxide

4. Na nitrilotriacetate

5. Na ethylenediaminetetraacetate

6. Compound from 1 mole of Mg2+ and 1 mole of ethanolaminediacetic acid.

7. Compound from 2 moles of Mg2+ and 1 mole of ethylenediaminetetraacetic acid.

8. Compound from 3 moles of Mg2+ and 2 moles of nitrilotriacetic acid.

9. Compound from I mole of Al3+ and one mole of ethanolaminediacetic acid.

10. A molding composition substantially as described in any of the foregoing Examples 6 to

11.

II. Moldings made from molding compositions claimed in any of claims 1 to 10.

WHAT WE CLAIM IS:

1. A molding composition of a thermoplastics material, which contains red phosphorus as a flameproofing agent and from 0.1 to 20% by weight, based on the red phosphorus, of a magnesium or aluminum salt of a chelate-forming aminoacetic acid as a stabilizer.

4. A molding composition as claimed in any of claims 1 to 3, wherein the

amount of red phosphorus is from I to 12% by weight, based on the molding composition.

5. A molding composition as claimed in any of claims I to 4, wherein the aminoacetic acid is ethanolaminediacetic acid, ethylenediaminetetraacetic acid or nitrilotriacetic acid.

6. A molding composition as claimed in any of claims I to 5, wherein the stabilizer used is manufactured by reacting nitrilotriacetic acid with an aluminum compound in the presence of ammonia.

7. A molding composition as claimed in any of claims I to 6, wherein from 10 to 60% by weight, based on the total molding composition, of filler is also present.

8. A molding coposition as claimed in claim 7, wherein the filler is glass fibers.

9. A molding composition as claimed in claim 7, wherein the filler is talc, mica or kaolin.