Flame retardant polyester moulding compositions

The invention relates to flame-retardant polyester molding compositions which contain calcium or aluminum phosphinates.

Polymers are often made flame-resistant by adding phosphorus-containing or halogen-containing compounds or mixtures thereof. Some polymers are processed at high temperatures, for example at 250 ° C or higher temperatures. For this reason, many known flame retardants are not suitable for such applications because they are too volatile or are not sufficiently heat-resistant.

Alkali salts of phosphinic acids are thermally stable and have already been proposed as flame-retardant additives for polyester (DE-A1-2 252 258). They have to be introduced in quantities of up to 30% by weight and in some cases have an unfavorable corrosion-promoting influence on the processing machines.

Furthermore, the salts of phosphinic acids with an alkali metal or a metal from the second or third main or subgroup of the periodic table have been used for the production of flame-retardant polyamide molding compositions, in particular the zinc salts (DE-A1-2 447 727). Flame-retardant thermoplastics can also be produced by using the above-mentioned phosphinic acid salts in combination with nitrogen bases such as melamine, dicyandiamide or guanidine (DE-A1-28 27 867).

Another large class of phosphinic acid salts are the polymeric metal phosphinates. These are non-ionic coordination complexes and are soluble in organic solvents. They are suitable as flame retardant components for halogenated aromatic polymers and for polyesters (US 40 78 016; US 4180495), polyamides (US 42 08 321) and polyesters / polyamides (US 42 08 322). The generally difficult technical production of these metal phosphinate polymers is disadvantageous.

It has now surprisingly been found that calcium and aluminum salts of phosphinic or diphosphinic acids show an excellent flame-retardant effect in polyester plastics, while other metal salts of the same phosphinic or diphosphinic acids give a significantly poorer flame-retardant effect.

The invention thus relates to a polyester molding composition which comprises a phosphinic acid salt of the formula (I) and / or a diphosphinic acid salt of the formula (II) and / or the polymers thereof<chemistry id="chem0001" num="0001"><img file="EP0699708B1_D0001.tif" /></chemistry><chemistry id="chem0002" num="0002"><img file="EP0699708B1_D0002.tif" /></chemistry> contains what<dl id="dl0001" compact="compact"><dt>R¹, R²</dt><dd>C.₁-C₆-Alkyl, preferably C₁-C₄-Alkyl, linear or branched, for example methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, n-pentyl; Phenyl;</dd><dt>R³</dt><dd><ul id="ul0001" list-style="none" compact="compact"><li>C.₁-C₁₀Alkylene, linear or branched, for example methylene, ethylene, n-propylene, isopropylene, n-butylene, tert-butylene, n-pentylene, n-octylene, n-dodecylene;</li><li>Arylene, for example phenylene, naphthylene;</li><li>Alkylarylene, for example methyl-phenylene, ethyl-phenylene, tert-butyl-phenylene, methyl-naphthylene, ethyl-naphthylene, tert-butyl-naphthylene;</li><li>Arylalkylene, for example phenylmethylene, phenylethylene, phenylpropylene, phenylbutylene;</li></ul></dd><dt>M</dt><dd>Calcium, aluminum ions;</dd><dt>m</dt><dd>2nd Or 3;</dd><dt>n</dt><dd>1 Or 3;</dd><dt>x</dt><dd>1 or 2</dd></dl> mean.

Polyesters are polymers that contain repeating units connected via an ester group in the polymer chain. Polyesters which can be used according to the invention are described, for example, in "Ullmann's encyclopedia of industrial chemistry, ed. Barbara Elvers, Vol. 21A, chapter 'Polyesters' (pp. 227-251), VCH, Weinheim-Basel-Cambridge-New York 1992 ", to which express reference is made.

In the following, the term “phosphinic acid salt” denotes salts of phosphinic and diphosphinic acids and their polymers.

The phosphinic acid salts according to the invention, which are produced in an aqueous medium, are essentially monomeric compounds. Depending on the reaction conditions, polymeric phosphinic acid salts can also arise under certain circumstances.

Suitable phosphinic acids as part of the phosphinic acid salts according to the invention are, for example: Dimethylphosphinic acid, ethyl methylphosphinic acid, diethylphosphinic acid, methyl n-propylphosphinic acid, methane-di (methylphosphinic acid), ethane-1,2- (dimethylphosphinic acid), hexane-1,6-di (dimethylphosphinic acid), benzene-1,4- (dimethylphosphinic acid), methylphenylphosphinic acid, diphenylphosphinic acid.

The salts of the phosphinic acids according to the invention can be prepared by known methods. The phosphinic acids are reacted in aqueous solution with metal carbonates, metal hydroxides or metal oxides.

The amount of the phosphinic acid salt of the general formula I or the diphosphinic acid salt of the formula II to be added to the polymers can vary within wide limits. In general, 5 to 30% by weight, based on the polymer, is used. The optimal amount depends on the nature of the polymer and the type of phosphinic acid salt used and can easily be determined by experiment.

The phosphinic acid salts according to the invention can be used in various physical forms depending on the type of polymer used and the desired properties. For example, the phosphinic acid salts can be ground to a finely divided form in order to achieve better dispersion in the polymer. If desired, mixtures of different phosphinic acid salts can also be used.

The phosphinic acid salts according to the invention are thermally stable, neither decompose the polymers during processing nor do they influence the manufacturing process of the polyester molding composition. The phosphinic acid salts are not volatile under manufacturing and processing conditions for polymers.

The phosphinic acid salt can be incorporated into the polymer by mixing the two and then melting the polymer in a compounding unit (eg twin-screw extruder) and homogenizing the phosphinic acid salt in the polymer melt. The melt can be drawn off as a strand, cooled and granulated. The phosphinic acid salt can also be metered directly into the compounding unit.

It is also possible to mix the flame-retardant additives into finished polyester granules and to process them directly on an injection molding machine or to melt them beforehand in an extruder, to granulate them and to process them after a drying process.

The flame retardant additive can also be added during the polycondensation.

In addition to the phosphinic acid salts according to the invention, fillers and reinforcing materials such as glass fibers, glass balls or minerals such as chalk can also be added to the settings. In addition, the products can contain other additives such as stabilizers, lubricants, colorants, nucleating agents or antistatic agents.

The flame-retardant polyesters according to the invention are suitable for the production of moldings, films, threads and fibers, for example by injection molding, extrusion or compression.

Examples

1. Production of phosphinic acid salts

<ul id="ul0002" list-style="none"><li>1.1 Preparation of the calcium salt of ethyl methylphosphinic acid 1630 g (15.1 mol) of ethyl-methylphosphinic acid are dissolved in 3 l of water and 422.8 g (7.55 mol) of calcium oxide (undeleted lime) are added in portions with vigorous stirring in 1.5 hours, the temperature rises to 75 ° C. Calcium oxide is then introduced further until a pH electrode introduced into the solution indicates pH = 7. Now a little activated carbon is added and the mixture is stirred under reflux for 1.5 hours and then filtered. The filtrate is evaporated to dryness and dried at 120 ° C. to constant weight in a vacuum drying cabinet. 1920 g of a white powder which does not melt up to 300 ° C. are obtained. Yield 100% of theory.</li><li>1.2 Production of the aluminum salt of ethyl methylphosphinic acid 2106 g (19.5 mol) of ethyl methylphosphinic acid are dissolved in 6.5 l of water and 507 g (6.5 mol) of aluminum hydroxide are added with vigorous stirring, during which the temperature is raised to 85.degree. The mixture is stirred at 80-90 ° C. for a total of 65 hours, then cooled to 60 ° C. and suction filtered. After drying in a vacuum drying cabinet at 120 ° C. to constant weight, 2140 g of a fine-grain powder which does not melt up to 300 ° C. are obtained. Yield: 95% of theory.</li><li>1.3 Preparation of the calcium salt of ethane-1,2-bismethylphosphinic acid 325.5 g (1.75 mol) of ethane-1,2-bismethylphosphinic acid are dissolved in 500 ml of water and 129.5 g (1.75 mol) of calcium hydroxide are added a little at a time with vigorous stirring. Then it is stirred for a few hours at 90-95 ° C., cooled and suction filtered. 335 g are obtained after drying in a vacuum drying cabinet at 150 ° C. The product does not melt up to 380 ° C. Yield: 85% of theory.</li><li>1.4 Production of the aluminum salt of ethane-1,2-bismethylphosphinic acid 334.8 g (1.8 mol) of ethane-1,2-bismethylphosphinic acid are dissolved in 600 ml of water and 93.6 g (1.2 mol) of aluminum hydroxide are added in portions with vigorous stirring in one hour. The mixture is then refluxed for 24 hours and then suction filtered while hot and washed with water. After drying, 364 g of a white powder which does not melt up to 380 ° C. are obtained. Yield: 100% of theory.</li><li>1.5 Preparation of the calcium salt of methyl propylphosphinic acid 366 g (3.0 mol) of methyl propylphosphinic acid are dissolved in 600 ml of water and 84 g (1.5 mol) of calcium oxide are added in portions with vigorous stirring, during which the temperature rises to 65 ° C. Now keep at this temperature until a clear solution is obtained. Now it is evaporated to dryness in vacuo. After drying the residue at 120 ° C. in a vacuum drying cabinet, 364 g are obtained. Yield: approx. 85% of theory.</li></ul>

2nd Manufacture and testing of flame retardant polyester

The phosphorus-containing compounds were mixed with the polymer and incorporated on a commercially available two-shaft compounder. In the case of glass fiber reinforced settings, commercially available glass fibers were metered into the melt for polyester.

The melt temperatures during compounding were approx. 250 ° C for polybutylene terephthalate (PBT) and approx. 270 ° C for polyethylene terephthalate (PET).

The test specimens were produced on an injection molding machine according to ISO 7792-2.

The fire class UL 94 (Underwriter Laboratories) was determined on test specimens from each mixture on test specimens with a thickness of 1.2 mm and tear strength and elongation at break according to ISO 527 were determined.

The following fire classes result according to UL 94:<dl id="dl0002"><dt>V-0</dt><dd>no afterburning longer than 10 sec, sum of the afterburning times with 10 flame treatments not longer than 50 seconds, no burning dripping, no complete burning of the sample, no afterglowing of the samples longer than 30 seconds after the flame treatment</dd><dt>V-1</dt><dd>no afterburning longer than 30 sec after the end of flame treatment, the sum of the afterburning times with 10 flame treatments not greater than 250 sec, no afterglow of the samples longer than 60 seconds after the end of flame treatment, other criteria as for V-0</dd><dt>V-2</dt><dd>Ignition of the cotton wool by burning dripping, other criteria as for V-1</dd></dl> &lt;V-2 does not meet fire class V-2. 2.1.1 Compounds reinforced with 30% glass fibers were produced from PBT and the calcium salt of ethylmethylphosphinic acid in various concentrations without further additives, test specimens were injected and tested with the following result: <tables id="tabl0001" num="0001"><table frame="all"><tgroup cols="4" colsep="1" rowsep="1"><colspec colnum="1" colname="col1" colwidth="39.37mm" /><colspec colnum="2" colname="col2" colwidth="39.37mm" /><colspec colnum="3" colname="col3" colwidth="39.37mm" /><colspec colnum="4" colname="col4" colwidth="39.37mm" /><thead valign="top"><row><entry namest="col1" nameend="col1" align="center">Ca salt concentration /%</entry><entry namest="col2" nameend="col2" align="center">Fire class UL 94</entry><entry namest="col3" nameend="col3" align="center">Tensile strength / Nmm^-2</entry><entry namest="col4" nameend="col4" align="center">Elongation at break /%</entry></row></thead><tbody valign="top"><row><entry namest="col1" nameend="col1" align="center">20</entry><entry namest="col2" nameend="col2" align="center">V-0</entry><entry namest="col3" nameend="col3" align="right">130</entry><entry namest="col4" nameend="col4" align="char" char=",">2,4</entry></row><row><entry namest="col1" nameend="col1" align="center">17,5</entry><entry namest="col2" nameend="col2" align="center">V-0</entry><entry namest="col3" nameend="col3" align="right">134</entry><entry namest="col4" nameend="col4" align="char" char=",">2,7</entry></row><row><entry namest="col1" nameend="col1" align="center">15</entry><entry namest="col2" nameend="col2" align="center">V-2</entry><entry namest="col3" nameend="col3" align="right">139</entry><entry namest="col4" nameend="col4" align="char" char=",">3,0</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="center">12,5</entry><entry namest="col2" nameend="col2" align="center">&lt;V-2</entry><entry namest="col3" nameend="col3" align="right">140</entry><entry namest="col4" nameend="col4" align="char" char=",">3,1</entry></row></tbody></tgroup></table></tables>2.1.2 Correspondingly with the calcium salt of propylmethylphosphinic acid (polymer: PBT): <tables id="tabl0002" num="0002"><table frame="all"><tgroup cols="4" colsep="1" rowsep="1"><colspec colnum="1" colname="col1" colwidth="39.37mm" /><colspec colnum="2" colname="col2" colwidth="39.37mm" /><colspec colnum="3" colname="col3" colwidth="39.37mm" /><colspec colnum="4" colname="col4" colwidth="39.37mm" /><thead valign="top"><row><entry namest="col1" nameend="col1" align="center">Ca salt concentration%</entry><entry namest="col2" nameend="col2" align="center">Fire class UL 94 V-0</entry><entry namest="col3" nameend="col3" align="center">Tear resistance N / mm²</entry><entry namest="col4" nameend="col4" align="center">Elongation at break%</entry></row></thead><tbody valign="top"><row rowsep="1"><entry namest="col1" nameend="col1" align="right">20</entry><entry namest="col2" nameend="col2" align="left">V-0</entry><entry namest="col3" nameend="col3" align="right">133</entry><entry namest="col4" nameend="col4" align="char" char=",">2,2</entry></row></tbody></tgroup></table></tables>2.2 As in Example 2.1.1, the procedure was carried out with the aluminum salt of ethylmethylphosphinic acid (polymer: PBT). <tables id="tabl0003" num="0003"><table frame="all"><tgroup cols="4" colsep="1" rowsep="1"><colspec colnum="1" colname="col1" colwidth="39.37mm" /><colspec colnum="2" colname="col2" colwidth="39.37mm" /><colspec colnum="3" colname="col3" colwidth="39.37mm" /><colspec colnum="4" colname="col4" colwidth="39.37mm" /><thead valign="top"><row><entry namest="col1" nameend="col1" align="center">Al salt concentration%</entry><entry namest="col2" nameend="col2" align="center">Fire class UL 94</entry><entry namest="col3" nameend="col3" align="center">Tear resistance N / mm²</entry><entry namest="col4" nameend="col4" align="center">Elongation at break%</entry></row></thead><tbody valign="top"><row><entry namest="col1" nameend="col1" align="center">20</entry><entry namest="col2" nameend="col2" align="left">V-0</entry><entry namest="col3" nameend="col3" align="right">115</entry><entry namest="col4" nameend="col4" align="char" char=",">2,0</entry></row><row><entry namest="col1" nameend="col1" align="center">17,5</entry><entry namest="col2" nameend="col2" align="left">V-1</entry><entry namest="col3" nameend="col3" align="right">120</entry><entry namest="col4" nameend="col4" align="char" char=",">1,9</entry></row><row><entry namest="col1" nameend="col1" align="center">15</entry><entry namest="col2" nameend="col2" align="left">V-2</entry><entry namest="col3" nameend="col3" align="right">130</entry><entry namest="col4" nameend="col4" align="char" char=",">2,1</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="center">12,5</entry><entry namest="col2" nameend="col2" align="left">V-2</entry><entry namest="col3" nameend="col3" align="right">135</entry><entry namest="col4" nameend="col4" align="char" char=",">2,5</entry></row></tbody></tgroup></table></tables> When 20% of the phosphorus-containing compound is added, the fire class UL 94 V-0 is set, with 17.5% only UL 94 V-1 is achieved. 2.3 (comparative example) The influence of the sodium salt of ethylmethylphosphinic acid mentioned in German application DE-A1-2 252 258 on the flame resistance of PBT is shown: <tables id="tabl0004" num="0004"><table frame="all"><tgroup cols="4" colsep="1" rowsep="1"><colspec colnum="1" colname="col1" colwidth="39.37mm" /><colspec colnum="2" colname="col2" colwidth="39.37mm" /><colspec colnum="3" colname="col3" colwidth="39.37mm" /><colspec colnum="4" colname="col4" colwidth="39.37mm" /><thead valign="top"><row><entry namest="col1" nameend="col1" align="center">Na salt concentration%</entry><entry namest="col2" nameend="col2" align="center">Fire class UL 94</entry><entry namest="col3" nameend="col3" align="center">Tear resistance N / mm²</entry><entry namest="col4" nameend="col4" align="center">Elongation at break%</entry></row></thead><tbody valign="top"><row><entry namest="col1" nameend="col1" align="right">30</entry><entry namest="col2" nameend="col2" align="center">V-0</entry><entry namest="col3" nameend="col3" align="center">40</entry><entry namest="col4" nameend="col4" align="char" char=",">0,4</entry></row><row><entry namest="col1" nameend="col1" align="right">20</entry><entry namest="col2" nameend="col2" align="center">&lt;V-2</entry><entry namest="col3" nameend="col3" align="center">70</entry><entry namest="col4" nameend="col4" align="char" char=",">1,0</entry></row><row><entry namest="col1" nameend="col1" align="right">15</entry><entry namest="col2" nameend="col2" align="center">&lt;V-2</entry><entry namest="col3" nameend="col3" align="center">93</entry><entry namest="col4" nameend="col4" align="char" char=",">1,5</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="right">10</entry><entry namest="col2" nameend="col2" align="center">&lt;V-2</entry><entry namest="col3" nameend="col3" align="center">116</entry><entry namest="col4" nameend="col4" align="char" char=",">1,7</entry></row></tbody></tgroup></table></tables> 30% of this connection is required to achieve UL 94 V-0; at a concentration of 20%, the fire class UL 94 V-2 is no longer met. The flame-retardant effect of this compound is considerably less than that of the compounds according to the invention mentioned in Examples 1 and 2. In addition, compared to the settings with the compounds according to the invention, there are very low tensile strengths and elongations at break of the sprayed test specimens, which are not acceptable in practice. 2.4 So far, examples with glass fiber reinforced PBT have been given. Example 2.4 shows the activity of the claimed compounds using the example of the calcium salt of ethylmethylphosphinic acid in unreinforced PBT.<tables id="tabl0005" num="0005"><table frame="all"><tgroup cols="3" colsep="1" rowsep="1"><colspec colnum="1" colname="col1" colwidth="52.50mm" /><colspec colnum="2" colname="col2" colwidth="52.50mm" /><colspec colnum="3" colname="col3" colwidth="52.50mm" /><thead valign="top"><row><entry namest="col1" nameend="col1" /><entry namest="col2" nameend="col2" align="center">Ca salt concentration /%</entry><entry namest="col3" nameend="col3" align="center">Fire class UL 94</entry></row></thead><tbody valign="top"><row><entry namest="col1" nameend="col1" align="left">Unreinforced</entry><entry namest="col2" nameend="col2" align="right">25</entry><entry namest="col3" nameend="col3" align="left">V-0</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="left">Unreinforced</entry><entry namest="col2" nameend="col2" align="right">20</entry><entry namest="col3" nameend="col3" align="left">V-1</entry></row></tbody></tgroup></table></tables> Unreinforced products require a higher amount to be used compared to glass fiber reinforced settings where the polymer content is lower. 2.5 Example 2.5 shows the activity of the claimed compounds in unreinforced and reinforced PET using the example of the calcium salt of ethylmethylphosphinic acid. <tables id="tabl0006" num="0006"><table frame="all"><tgroup cols="3" colsep="1" rowsep="1"><colspec colnum="1" colname="col1" colwidth="52.50mm" /><colspec colnum="2" colname="col2" colwidth="52.50mm" /><colspec colnum="3" colname="col3" colwidth="52.50mm" /><thead valign="top"><row><entry namest="col1" nameend="col1" /><entry namest="col2" nameend="col2" align="center">Ca salt concentration%</entry><entry namest="col3" nameend="col3" align="center">Fire class UL 94</entry></row></thead><tbody valign="top"><row><entry namest="col1" nameend="col1" align="left">unreinforced</entry><entry namest="col2" nameend="col2" align="right">25</entry><entry namest="col3" nameend="col3" align="left">V-0</entry></row><row><entry namest="col1" nameend="col1" align="left">30th % Glass fibers</entry><entry namest="col2" nameend="col2" align="right">30</entry><entry namest="col3" nameend="col3" align="left">V-0</entry></row><row><entry namest="col1" nameend="col1" align="left">30th % Glass fibers</entry><entry namest="col2" nameend="col2" align="right">25</entry><entry namest="col3" nameend="col3" align="left">V-0</entry></row><row rowsep="1"><entry namest="col1" nameend="col1" align="left">30th % Glass fibers</entry><entry namest="col2" nameend="col2" align="right">20</entry><entry namest="col3" nameend="col3" align="left">V-0</entry></row></tbody></tgroup></table></tables>