Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/04—Oxygen-containing compounds
  • C08K5/09—Carboxylic acids; Metal salts thereof; Anhydrides thereof
  • C08K5/098—Metal salts of carboxylic acids
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/02—Halogenated hydrocarbons
  • C08K5/03—Halogenated hydrocarbons aromatic, e.g. C6H5-CH2-Cl
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/49—Phosphorus-containing compounds
  • C08K5/51—Phosphorus bound to oxygen
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L77/00—Compositions of polyamides obtained by reactions forming a carboxylic amide link in the main chain; Compositions of derivatives of such polymers
  • C08L77/06—Polyamides derived from polyamines and polycarboxylic acids

Definitions

• the present invention relates to stabilized polyamide compositions.
• Polymers are easily broken down in the heat by oxidation, which leads to embrittlement of the material and mechanical failure of the products made from it. Certain chemical compounds are therefore added, which can postpone the embrittlement time with different effectiveness. These so-called antioxidants are mostly based on phenol, amine or phosphorus derivatives. Special variants are also used for polyamides. However, there is a particularly effective class of substances that have no effectiveness with other polymers. These are the so-called copper stabilizers. Such stabilization systems have been known for a long time and are widely used in the production of polyamides, e.g. for polyamide fibers from which tire cord is made, and for polyamide injection molded parts for technical applications, especially in mechanical engineering (cars) and the electrical industry (switches, circuit boards).
• copper stabilizers usually consist of two components.
• a copper compound such as a copper halide or other copper salts, is used as the first component.
• a large excess of a halogen compound must be added as the second component.
• potassium iodide but also potassium bromide are used as the second component.
• the molar ratio copper: halogen is usually 1: 5-15.
• the recommended addition is usually 30 to 200 ppm copper, ie 150 to 3000 ppm of a halogen are used at the same time.
• Polyamides absorb approx. 3% water when in use (conditioned). As a result, water-soluble components are extracted from the polyamide to the surface when the temperature changes, which leads to the formation of deposits. If copper, potassium or other soluble halides are used, they come to the surface and form a hygroscopic, usually acid-reacting coating. This affects the tracking resistance; this can lead to failure of electrical components. On contact with metals there is increased corrosion at these points. It is difficult to meet the requirements of the automotive and electronics industries.
• these stabilizers are very difficult to incorporate homogeneously in polyamide. Care must be taken to ensure that the salts used are very finely divided and are incorporated very evenly into the polyamide melt.
• a problem here is the tendency of the substances described to agglomerate. The starting raw materials must therefore be finely ground and protected against reagglomeration. The addition itself is difficult to control directly. Therefore, a pre-concentrate (masterbatch) is usually produced, which is then added. Even then, such a heterogeneous mixing of solid particles in a melt is not as optimal as if the stabilizer melted even under the processing conditions and was homogeneously compatible, as it is e.g. is the case with phenolic, amine and other antioxidants.
• the crystalline particles of the stabilizer salts negatively influence the physical characteristics of the polyamides even if they are very finely divided. This is based not only on possible inhomogeneities in the distribution, but also on the fact that fine particles in polyamides act as nuclei and so on cause increased crystallinity in polymers. This can sometimes lead to undesirable side effects.
• the impact strength can drop by 20 to 30% compared to the initial value.
• EP-A-390277 discloses a stabilized polyamide 4.6 composition.
• This special, very high-melting polyamide can therefore be stabilized by adding an insoluble copper salt and a halogen-substituted organic compound.
• This composition is said to be particularly suitable for electrical or electronic applications.
• GB-A-1131933 and GB-A-1143826 disclose stabilized linear polyamides containing a mixture of a copper compound soluble in the polyamide and special halogen-containing organic aliphatic compound maximum? Carbon atoms are stabilized.
• these organic compounds have a comparatively high volatility. This can lead to undesirable embrittlement of the material due to the leakage of the organic compound.
• a stabilized polyamide composition which is characterized in that at least one copper salt and at least one halogen-containing organic compound are present as stabilizer, the halogen-containing organic compound being selected from the group consisting of:
• the polyamide is not a polyamide 4.6.
• the present invention provides a method for producing a stabilized polyamide composition, which is characterized in that is that at least one polyamide, a copper salt and at least one halogen-containing organic compound selected from the group consisting of:
• the polyamide is not a polyamide 4.6,
• the present invention provides the use of at least one copper salt and at least one halogen-containing organic compound, which are defined as indicated above, for the stabilization of polyamides.
• Components (a) and / or (b) are preferred in each case.
• the at least one polyamide in accordance with the present invention can be any polyamide.
• Polyamides are polymers with recurring carbonamide groups -CO-NH- in the main chain. You are training
• aminocarboxylic acids or their functional derivatives e.g. Lactams; or off
• polyamides A wide variety of polyamides is accessible through variations of the monomer building blocks. According to the invention, both homopolyamides and copolyamides are used. Block copolymers of polyamides with polyethers and other polymer-modified polyamides can also be used.
• the main representatives of the polyamides are polyamide 6.6 (from hexamethylenediamine-alipic acid) and polyamide 6 (from ⁇ -caprolactam).
• Other important polyamides are polyamide 11, polyamide 12, polyamide 610, PACM, MPB-I, PPD-T and the aramids.
• Blends of polyamide with other polymers can also be used. However, the stabilizer components may have a disadvantageous effect on the blend components. They must therefore be chosen carefully.
• the copper salt used according to the invention can be any copper salt.
• Salts of monovalent or divalent copper with inorganic or organic acids are preferred.
• suitable copper salts are the copper (I) salts, such as CuJ, CuBr, CuCI or CuCN, copper (II) salts, such as CuCI 2 , CuBr 2 , CuJ 2 , copper acetate, copper sulfate, copper stearate, copper propionate, copper butyrate, copper octate, or copper benzoate Copper nitrate and the ammonium complexes of the salts mentioned above.
• copper (I) salts such as CuJ, CuBr, CuCI or CuCN
• copper (II) salts such as CuCI 2 , CuBr 2 , CuJ 2 , copper acetate, copper sulfate, copper stearate, copper propionate, copper butyrate, copper octate, or copper benzoate Copper nitrate and the ammonium complexes of the salts mentioned above.
• Compounds such as copper acetylacetonate or copper EDTA can also be used. It is also possible to use mixtures of different copper salts. If necessary, copper powder can also be used. This reacts in the polyamide melt to form copper compounds.
• the copper (I) halides and the copper salts of organic acids are preferred. Copper (I) iodide and copper acetate are particularly preferred.
• the amount of copper used in the stabilized polyamide compositions is not limited as long as the mechanical properties of the polyamide are not be adversely affected. It is usually between 10 and 1000 ppm copper, based on the total composition. Preferably 20 to 700, particularly preferably 50 to 150 ppm copper are used.
• any halogen-containing organic compound used can be any aromatic compound and / or any aliphatic phosphate and / or any paraffin.
• Aromatic bromine compounds, brominated aliphatic phosphates and chlorinated or brominated paraffins are preferred.
• the molecular weight of the halogen-containing organic compound used according to the invention is not subject to any restrictions. It should generally be chosen so that the compound is only slightly volatile, can be mixed easily and homogeneously with the polyamide and shows little tendency to migrate in the finished composition.
• Brominated aromatic oligomeric epoxy resins are also preferred, in particular those based on tetrabromobisphenol-A.
• paraffins which can be used according to the invention are halogenated, in particular fluorinated, chlorinated or brominated, paraffins. Both soft and hard paraffins can be used. Compounds such as chlorinated paraffins (for example with an average formula C 20 H 24 Cl ⁇ 8 ), Teflon waxes (for example with an average formula C 20 H 22 F 20 ) and Viton copolymers (copolymers of hexafluoropropylene and vinylidene fluoride) are preferred.
• Tris (dibromoneopentyi) phosphate and decabromophenyl and polydibromostyrene are preferred. It is also possible to use mixtures of halogen-containing organic compounds.
• the addition amount for the halogen-containing organic compound is usually less than 10% by weight. Amounts are usually added such that 50 to 30,000 ppm of halogen, based on the total composition, are used. 100 to 10,000 ppm, particularly preferably 500 to 1,500 ppm halogen are preferably used.
• the ratio of copper to halogen in the stabilized polyamide compositions is from 1: 1 to 1: 3000; the range from 1: 2 to 1: 100 is preferred, particularly preferably from 1: 5 to 1:15 (in each case Moi ratio).
• halogenated organic compounds have a significantly poorer stability. They show increased cleavage of polymer chains, which leads to premature embrittlement of the components and severe discoloration.
• the content of halogenated organic compounds is preferably less than 3% by weight, particularly preferably less than 1% by weight.
• the copper salts or the halogen-containing organic compounds defined above are simply called stabilizer components below.
• the polyamide compositions according to the invention are distinguished by an increased long-term use temperature, improved tracking resistance and less tendency to discolour. These advantages of the stabilized polyamide compositions according to the invention are believed to be based on the synergistic effect of the halogen-containing organic compound, which only has to be added in very small amounts.
• the tracking resistance which is determined as the CTI value, is greatly improved by the use of organic compounds.
• the field of use of the polyamide compositions according to the invention is expanded to components which are used in the electrical or electronics industry.
• Polyamides for electrical components should have a CTI value of 600, but at least 550. This value is achieved by pure polyamide.
• the CTI value is determined in accordance with DIN-IEC 112.
• the polyamide compositions according to the invention also have better dielectric strength compared to the polyamides provided with conventional copper / halogen salt stabilizers.
• the organic compounds used according to the invention show improved dispersibility in the polymer melt in comparison with halogen salts. This eliminates the need for extensive homogenization. If a copper salt, such as copper stearate, is used at the same time, the total amount of stabilizer is meltable and therefore very readily dispersible in the polyamide.
• the stabilizer components used according to the invention show very good compatibility with all polyamides, which means that there is no efflorescence on the plastic processing machines (nozzles, screws, molds) and on the finished plastic parts or fibers.
• the polyamide compositions according to the invention show only a very low tendency to discoloration.
• discolorations were usually so severe that these compositions could only be used in black. It is therefore surprising that this does not occur or only occurs slightly in the polyamide compositions according to the invention.
• This makes it possible to obtain polyamides colored with pigments without causing color shifts. Even parts colored with TiO 2 pigments retain their brilliant white. This opens up an additional field of application for colored polyamides where increased long-term heat stability is required, which was previously only possible with conventional stabilizer systems, which, however, could not be used due to their discolouring properties.
• the polyamide compositions according to the invention thus have the advantage that they bring higher long-term stability and at the same time can be colored with pigments are without the otherwise occurring self-discoloration undesirably changing the coloring with pigments.
• All conventional pigments such as titanium dioxide, lead white, zinc white, litopone, antimony white, carbon black, iron oxide black, manganese black, cobalt black, antimony black, lead chromate, red lead, zinc yellow, zinc green, cadmium red, cobalt blue, Berlin blue, ultramarine, are suitable for coloring the polyamide compositions according to the invention.
• the polyamide compositions according to the invention are also excellent in terms of hydrolysis stability. They show improved long-term stability under acidic and alkaline conditions, compared to salt solutions, glycol-water mixtures as well as against hot fats and oils and organic solvents. This means that the loss of mechanical strength (impact strength, tensile strength) that usually occurs quickly under these conditions, as well as the tendency of the polyamides to become brittle, is drastically reduced and the long-term usability is significantly improved. Compared to other stabilizers used for this purpose, such as phenolic, amine or conventional copper-halogen salt stabilizers, a significantly better effect is obtained.
• polyamide compositions according to the invention can be combined with other additives without restriction, such as, for example, lubricants, plasticizers, crystallization accelerators, without impairing the desired stabilizing effect.
• additives used are also stabilized against thermal degradation and discoloration in polyamides, ie polyamides treated with plasticizers, such as BBS or waxes, such as montanates, show less yellowing.
• Polyamide compositions according to the invention which are equipped with glass fibers, glass balls, minerals or other reinforcing agents, become quite significant in their long-term heat aging stability improved compared to types stabilized with conventional copper / halogen salt stabilizers.
• the polyamide compositions according to the invention can furthermore be provided with the customary fillers or reinforcing materials.
• suitable fillers or reinforcing materials are glass materials in the form of fibers, yarns, rovings, spheres or powders, oxidic materials such as silica, alumina or aluminosilicates, and graphite or plastic fibers or whiskers.
• the stabilized polyamide compositions according to the invention were evaluated as to whether a further improvement in the tendency to discoloration could not be achieved. Surprisingly, it was found that a further reduction in the tendency to discoloration can be achieved by adding organic phosphites or inorganic phosphonates or inorganic hypophosphites. These substances are known as color stabilizers in polyamides. However, it was also known that these color stabilizers often lead to the formation of copper oxides with copper salts, which causes gray or brown-black discoloration.
• the organic phosphites which can be used according to the invention are esters of phosphorous acid. Aliphatic as well as aromatic or mixed esters can be used. Typical examples of these are e.g. Dimethyl and diethyl phosphite, trimethyl and triethyl phosphite and the organic phosphites known as additives in plastics processing.
• Typical examples of these are tris (2,4-di-t-butylphenyl) phosphite (phosphite 20), bis (2,4-di-t-butylphenyl) pentaerythritol diphosphite (phosphite 21), tetrakis (2,4-di-t- butylphenyl) 4,4'-biphenylenediphosphonite (phosphite 23), distearylpentaerythritol diphosphite, diisooctylphosphite, distearylphosphite, triisodecylphosphite, triisooctylphosphite, trilaurylphosphite, tristearylphosphite, tris (dipropylene glycol) phosphitylphosphite, tritylphenylphosphite, Such compounds are available under the trade
• Inorganic phosphonates which can be used according to the invention are salts of phosphonic acid.
• the alkali metals, the alkaline earth metals and other customary metals are suitable as salt formers. Lithium, potassium, sodium, magnesium, calcium, strontium, barium and aluminum are particularly preferred. Sodium, potassium, magnesium and calcium are particularly preferred.
• a particularly preferred phosphonate is disodium hydrogenphosphonate.
• the inorganic hypophosphites which can be used according to the invention are salts of hypophosphorous acid. With regard to the metals that can be used for salt formation, the same applies as stated above for the phosphonates.
• the sodium salt of hypophosphorous acid is a particularly preferred example of the hypophosphites which can be used according to the invention.
• the amount of the further additives listed above is between 0.005 and 1.0% (50 to 10,000 ppm), preferably in the range from 0.05 to 0.2% (500 to 2,000 ppm) and particularly preferably in the range from 0.075 to 0, 15% (750 to 1,500 ppm). This amount relates to the total composition.
• the organic phosphites to be used are preferably meltable, stable in processing and resistant to extraction. This prevents the release of phosphorous acid, which has an adverse effect on the overall composition.
• the organic phosphite, inorganic phosphonate or inorganic hypophosphite is preferably added only after the preparation of the composition stabilized with the stabilizer components. If a polyamide composition stabilized according to the invention is first prepared and the organic phosphite, the inorganic phosphonate or the inorganic hypophosphite is added only in a further processing step, no discoloration is obtained. In the case of inorganic phosphonates in particular, the process described above clearly shows this effect.
• the organic phosphite, the inorganic phosphonate or the inorganic hypophosphite can be introduced as such in pure form or in the form of a premix (masterbatch).
• the polyamide compositions according to the invention are generally prepared by mixing at least one polyamide with at least one copper bond and at least one halogen-containing organic compound, which are defined as specified in claim 1. It is possible to mix the components directly with one another in conventional mixing devices, ie polyamide and stabilizer components are melted and mixed together. However, the polyamide is preferably first melted and then the stabilizer components are mixed in. It is particularly preferred to add the stabilizer components in the form of a premix (masterbatch) to the melted polyamide. This particularly simplifies the metering of the stabilizing components.
• Suitable mixing devices are known to the person skilled in the art and include mixing rolling mills, discontinuously working internal mixers and kneaders, continuously working extruders and kneaders and static mixers.
• continuously operating extruders both single-screw and twin-screw extruders, which enable good mixing, is preferred.
• the polyamide is usually first melted in the extruder; the stabilizing components can then be metered in through suitable openings.
• a preconcentrate of the stabilizing components is used in the production of the polyamide compositions according to the invention, this preconcentrate can be produced in batch mixers which enable very good, homogeneous distribution.
• An example of a mixer that is preferably used is a Buss kneader. Usually, however, continuous mixers such as twin-screw extruders or twin-screw kneading extruders are used here.
• the same polyamide that is then mixed with the preconcentrate is usually used as the matrix material. However, it is also possible to choose a different polyamide or a different polymer.
• the concentration of stabilizing components in the pre-concentrate depends on the tolerance in the matrix material and according to the desired final concentration in the finished compound and good meterability. Pre-concentrates up to a concentration of 50% by weight can be produced, for example from a mixture of CuJ and polydibromostyrene (1:10).
• the EP oligomers are characterized in particular by their excellent temperature stability. In addition, their combinations with copper connections are very inexpensive. Polydibromostyrene and EP oligomer 1 are also particularly suitable for the production of highly concentrated preconcentrates, since they are very well tolerated with polyamides. Pre-concentrates can be produced with up to 50% by weight of these compounds.
• EP oligomer 2 on the other hand, can only be incorporated up to about 10% by weight.
• the reaction of the EP end group with the amino groups in the PA leads to a sharp increase in the viscosity of the melt.
• this chemical reaction also has the advantage that the integration into the finished compound is improved.
• test specimens tested in the following examples were produced and tested as follows:
• the stabilizer mixtures and Ca stearate as a lubricant were premixed with polyamide granules and melted using an extruder, homogenized, continuously drawn off and pelletized as a strand.
• the Cu concentration was always 100 ppm
• the halogen concentration was approximately 1000 ppm (0.1%)
• the Ca stearate concentration was 0.3%.
• the test granules were produced from the granules on an injection molding machine to determine the impact strength (DIN 53453) and the bending strength (DIN 53452).
• Test platelets of 3x5 cm and 3 mm thickness were produced from the granules described above on the injection molding machine and tested in accordance with the DIN standard IEC-112.
• the discoloration of the test platelets was assessed optically, and the color intensity was also determined by measuring the brightness value (DIN 6174; DIN 5033, part 1-7).
• the samples according to the invention show CTI values which enable their use in the electronics field.

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