Hydrophobic polyamides.

0001The invention relates to thermoplastically processable polyamides which contain special aromatic amines, optionally in combination with selected phenolic compounds.

0002The well-known high level of properties of the thermoplastically processable polyamides essentially depends on the hydrogen bonds that are active between different carbonamide groups. The hydrophilicity caused by the polarity of the carbonamide groups also has a major influence on this, since it has a clearly measurable water absorption both when stored in water and in a standard climate (see eg Plastics Handbook Volume VI, Polyamides, Carl-Hanser-Verlag, Munich 1966, p. 458 ff) caused.

0003For example, the impact strength of moldings made of polyamides depends significantly on the water content of the moldings. In the water-free state, for example after the molded articles have been produced by injection molding, the molded articles made from easy-flowing and therefore easy-to-process polyamides with medium molecular weights are particularly sensitive to impact stress. This applies in particular to moldings made from partially crystalline polyamides.

0004The toughness of these moldings can be significantly improved by conditioning with water. At the same time, however, the products are softened, which can be observed particularly clearly by a drastic reduction in the rigidity, measured by the modulus of elasticity.

0005However, for many areas of application, in particular for functional and body parts in the automotive sector, high rigidity and sufficient toughness of the molded parts is necessary.

0006Since the water absorption of polyamides also depends on their crystallinity, this can be influenced to a small extent by additives that promote crystallization and by suitable post-treatment (eg tempering). A decisive change in water absorption can result in partially crystalline polyamides such as. eg PA-6.6 but cannot be reached.

0007A number of procedures have become known for improving the toughness of polyamides even in the freshly sprayed state, ie without improving the toughness-promoting influence of the water. This can be achieved, for example, by admixing certain elastomeric polymers. For example, polyethylenes, copolymers of ethylene with polar comonomers such as vinyl acetate, (meth) acrylic acid (ester) have been proposed as toughness-improving additives or suitable modified rubbers such as Copolymers of butadiene and acrylonitrile.

0008In all of these cases, the toughness of the products is improved. However, since the tendency of the polyamide, which is usually the main component, to retain water up to 10% remains unchanged, the unavoidable, very high water absorption also worsens the stiffness already reduced by the polymeric toughness modifier so much that the products for technical parts with high demands on rigidity, toughness and dimensional stability are completely unsuitable.

0009In the case of polyamides made from long-chain amide-building blocks, ie in the case of products with lower concentrations of CONH groups in the polymer chains, significantly less water is absorbed and the corresponding influence on the mechanical properties is less, but the products have insufficient heat resistance and rigidity for many applications on; they are also expensive because of the high price of the raw materials.

0010There is therefore a need for polyamides which, even after conditioning, have a high heat resistance, high rigidity, satisfactory toughness and improved dimensional stability compared to PA-6 or PA-6,6.

0011Surprisingly, it has now been found that the water absorption of polyamides, preferably of partially crystalline polyamides, can be reduced and polyamides with the stated combination of properties can be achieved if the polyamides are modified with selected, higher molecular weight amomatic (poly) amines, optionally in combination with selected phenolic compounds.

0012The use of a large number of aromatic amines and diamines as heat stabilizers for polyamides has already been described repeatedly. These compounds are said to be sufficiently effective even in amounts of 0.5% by weight. The use of a large number of sterically hindered, preferably o, o'-disubstituted, sterically hindered, phenolic compounds as heat stabilizers for polyamides has also been repeatedly proposed, quantities of 0.5% by weight also being regarded as sufficiently effective here. There is no indication that special (poly) amines in higher concentrations, possibly in combination with suitable phenols, lead to a reduction in water absorption and thus enable a higher rigidity.

0013The invention therefore relates to thermoplastic, optionally reinforced polyamide molding compositions, which are characterized in that they<ul id="ul0001" list-style="none"><li>1) 1.5 to 10 wt .-%, preferably 2 to 8 wt .-%, based on the polyamide, of at least one aromatic amine of the general formula I or II<chemistry id="chem0001" num="0001"><img file="EP0166321A2_D0001.tif" /></chemistry>and if necessary</li><li>2) up to 8% by weight, based on the polyamide, preferably up to 5% by weight of a phenol of the general formula III<chemistry id="chem0002" num="0002"><img file="EP0166321A2_D0002.tif" /></chemistry>where in the formulas I-III the radicals R¹ to R⁷ and Ar are defined below and the sum of components 1) and 2) may always be at most 10% by weight, preferably 8% by weight, based on polyamide.</li></ul>

0014The aromatic amines of the general formula I contain at least 10, preferably 10 to 36 C atoms, particularly preferably 10 to 24 C atoms, in the general formula I<chemistry id="chem0003" num="0003"><img file="EP0166321A2_D0003.tif" /></chemistry><ul id="ul0002" list-style="none"><li>_R¹ and _R², independently of one another, a hydrogen atom, a C₁-C₂₄- preferably C₄-C₁₈-Alkyl-, a ^C.₆-^C.₁₈- preferably C₆-C₁₂-Aryl- or a C₇-C₂₀- preferably C₇-C₁₅Aralkyl radical, each of the radicals having at least one C₁-C₁₂-, preferably C₁-C₈-Alkylgruppe or a halogen atom (preferably Cl or Br) may be substituted and the aryl radicals via -O-, C₁-C₃-Alkylene or -SO₂-Bridges can be connected, or R1 and _R² together members of an aromatic or cycloaliphatic ring with C₅-C₁₂ can be and</li><li>R³ a hydrogen atom or a C₁-C₂₄-, preferably C₁-C₁₈-Alkyl-, C₆-C₁₀-, preferably C₆-Aryl-, C₇-C₁₅-, preferably C₇-C₁₂Aralkyl or C₇-C₁₅-, preferably C₇-C₁₂-Alkaryl radical can be.</li></ul>

0015Higher molecular or long-chain primary or secondary aromatic amines with C are preferred₁₀-C₂₄, like one or more times with a C_l-C₁₂-Alkyl and / or C₇-C₁₅Aralkyl radical substituted aromatic amines or optionally with at least one C.₁-C₆-Alkyl group substituted amino-di- or triphenyls, the rings of which are optionally via -O-, C₁-C₃-Alkylene, or -SO₂- Bridge links can be connected.

0016The aromatic polyamines of the general formula II contain at most 40 C atoms, preferably at most 30 C atoms. In general formula II,<chemistry id="chem0004" num="0004"><img file="EP0166321A2_D0004.tif" /></chemistry>Ar mean one with R⁴ and R⁵ substituted phenylene or naphthylene radical or a directly or via -0-, C₁-C₃-Alkylene- or -SO₂-Bridges connected, possibly one or more times with a C₁-C₄Alkyl group substituted C₁₂-C₃₆, preferably C₁₂-C₂₀-Diarylene radical and R and R are the same or different, a hydrogen atom or a C₁-C₂₄-, preferably C₁-C₁₈-Alkyl radical.

0017The amines can also be used in combination with non-sterically hindered monophenolic compounds with at least 10 C atoms, which may be substituted at most in an o-position to the phenolic OH group and correspond to the general formula III: in the<chemistry id="chem0005" num="0005"><img file="EP0166321A2_D0005.tif" /></chemistry><ul id="ul0003" list-style="none"><li>R⁶and R⁷, independently of one another, a hydrogen atom, a C₁-C₁₆-, preferably C₄-C₁₂-Alkyl-, a C₆-C₁₈-, preferably C₆-C₁₂-Aryl- or a C₇-C₂₀-, preferably C₇-C₁₅-Aralkyl radical, where each of the radicals can be substituted with at least one C1-C12-alkyl group or a halogen atom (preferably Cl or Br) and the aryl radicals via -O-, C₁-C₃-Alkylene or -SO₂-Bridges can be connected, or</li><li>_R⁶and R⁷ Members of an aromatic or cycloaliphatic ring with C₅-C₁₂ could be.</li></ul>

0018One or more C are preferred_i-C₁₂-Alkyl and / or C₇-C₁₅Aralkyl substituted monophenolic compounds with C₁₀-C₂₂which may be substituted at most in an o-position to the OH group, or optionally with at least one C.₁-C₆-Alkyl group substituted monohydroxy-di- or triphenyls, the rings of which may be via -O-, Cl-C3-alkylene or -S0₂- Bridge members can be connected and which may be substituted at most in an o-position to the OH group.

0019The following aromatic amines, diamines and phenols can be mentioned by way of example:<ul id="ul0004" list-style="none"><li>a) Aromatic monoamines tetrahydronaphthylamine, 2-butyl-aniline (secondary and tertiary), 4-tert-butyl-aniline, 4-tert.-pentyl-aniline, octylaniline (mixtures), nonylaniline (mixtures), dodecylaniline (mixtures), 4-aminodiphenyl, 2-aminodiphenyl, alkyl-substituted aminodiphenyls, 1-aminonaphthalene, 2-aminonaphthalene, benzylaniline (s), benzyl-toluidine (s), 2-phenyl-2- (4-aminophenyl) propane, 4-aminodiphenylsulfone, 4-amino-diphenyl ether, 2- or 4-cyclohexylaniline, N, N-diphenylamine, N-benzylaniline or mixtures of the compounds mentioned.</li><li>b) Aromatic diamines bis- (4-aminophenyl) methane, 3-methylbenzidine, 2,2- bis (4-aminophenyl) propane, 1,1-bis- (4-aminophenyl) cyclohexane, 1, 2-diaminobenzene, 1,4-diaminobenzene, 1,4-diaminonaphthalene, 1,5-diaminonaphthalene, 1,3-diaminotoluene (s), N, N'-dimethyl-4,4'-biphenyl-diamine, bis- ( 4-methylaminophenyl) methane, 2,2-bis (4-methylaminophenyl) propane or mixtures of the compounds mentioned.</li><li>c) Phenolic compounds tetrahydronaphthol, 2-butylphenol (secondary and tertiary), 4-t-butylphenol, thymol, 4-tert.-pentylphenol, octylphenol (mixtures), nonylphenol (mixtures), dodecylphenol (mixtures) , 4-hydroxydiphenyl, 2-hydroxydiphenyl, with hydroxyl-substituted hydroxydiphenyls, such as, for example described in DOS 19 43230, 1-naphthol, 2-naphthol, benzylphenol (s), benzyl cresol (s), 2-phenyl-2- (4-hydroxyphenyl) propane, 4-hydroxydiphenylsulfone, 4-hydroxydiphenyl ether, 2- or 4-cyclohexylphenols or mixtures of the compounds mentioned.</li></ul>

0020The following are particularly advantageous:<ul id="ul0005" list-style="none"><li>Nonylaniline, dodecylaniline, 2-amino-biphenyl, 4-amino-diphenyl ether, 2- and 4-cyclohexylaniline, N, N-diphenylamine and N-benzylaniline, optionally in combination with alkyl group-substituted hydroxydiphenylene, nonylphenol, dodecylphenol, 2- Hydroxybiphenyl and 2-phenyl-2- (4-hydroxyphenyl) propane.</li></ul>

0021The amine is incorporated in amounts of 1.5 to 10, particularly preferably 2 to 8,% by weight, based on polyamide, optionally in combination with phenols of the general formula III, the amount of phenol up to 8% by weight, preferably up to 5 wt .-%, based on polyamide, and the sum of the two components max. 10% by weight, preferably max. 8 wt .-%, based on polyamide, should be.

0022Linear polycondensates of lactams with at least 5 ring members, such as, for example, can be used as polyamides -Caprolactam or laurolactam, or from corresponding -aminocarboxylic acids, or from diamines and dicarboxylic acids such as 6,6-, 6,7-, 6,8-, 6,9-, 6,10-, 6,12-, 8,8 -, 12,12-polyamide, or polycondensates of aromatic dicarboxylic acids such as isophthalic acid, terephthalic acid with diamines such as hexamethylene diamines, octamethylene diamine, of araliphatic starting materials such as m- or p-xylylenediamines and adipic acid, suberic acid, sebacic acid, Polycondensates based on alicyclic starting materials such as cyclohexanedicarboxylic acid, cyclohexanediacetic acid, diaminodicyclohexylmethanes, isophoronediamine can be used.

0023Semi-crystalline polyamides are preferably used, particularly preferably PA-6 and PA-6,6.

0024Instead of polyamides, polymer alloys can also be used, consisting predominantly, preferably to at least 60% by weight, of polyamide and known elasticizing polymers such as polyolefins, olefinic copolymers, preferably those with proportions of built-in polar groups or corresponding graft (co) polymers .

0025To produce the modified polyamides according to the invention, the polyamide component and the modifiers can be mixed with one another above the melting point of the polyamide. This can be done, for example, immediately after the polyamide has been produced by mixing the modifier with the melt to be spun as a strand. The polyamides modified according to the invention are preferably produced by mixing the starting components in conventional screw machines. The components can be mixed before they are dosed together or can be fed into the extruder by two dosing systems. In the case of liquid additives, the parallel addition is advantageous.

0026This method is chosen in particular if, in addition to polyamides, other polymers are used to produce appropriately modified polymer alloys or other additives such as stabilizers, mold release agents, lubricants, crystallization accelerators, plasticizers, pigments, colorants, reinforcing agents and / or fillers, such as glass fibers or asbestos, are incorporated become.

0027Commonly known apparatuses are suitable for compounding. Twin screw extruders are preferred.

0028The polyamide molding compositions according to the invention are distinguished by a substantially improved dimensional stability and a higher rigidity with an otherwise essentially constant property profile compared to the unmodified polyamides. The polyamide molding compositions are particularly suitable for the production of shaped articles reinforced with glass fiber or mixed with fillers, since the stiffening and hardening effect of the additions, which are preferably added in amounts of 10 to 60% by weight, is compensated far less than previously by water absorption. These glass fiber reinforced products are characterized by improved elongation at break and toughness.

0029The new polyamide molding compositions are particularly suitable for the production of moldings by the injection molding process and preferably for applications in which a combination of high rigidity, high heat resistance and satisfactory toughness is important. The glass fiber reinforced products are particularly suitable for molded parts in the automotive industry such as cooler boxes or oil pans and for applications in the underwater area.

example 1

003095 % By weight of a 6-polyamide with a rel. Viscosity of 3.1, measured in 1% solution in m-cresol at 25 ° C and 5% by weight p-cyclohexylaniline, are mixed by means of a drum mixer and conveyed through a metering scale into a ZSK 53 twin-screw extruder and at 260 ° C extruded at 90 rpm. The homogeneous melt is spun as a strand in a water bath, granulated and dried at 80 to 100 ° C to a water content of 0.1%. The product has a rel. Viscosity of 2.9.

0031Shaped bodies made from the product are stored together with unmodified comparative samples over long periods in a standard climate and in water. The polyamide modified according to the invention absorbs significantly less water under all conditions. Measurement data are summarized in Table 1.

0032To determine the modulus of elasticity after water absorption, unreinforced products were conditioned uniformly to 2.5% by weight water content, reinforced to 1.5% water content by water storage.

Example 2-8

0033Analogously to Example 1, various hydrophobizing additives are incorporated into various polyamides and the products obtained are examined as described in Example 1. The composition of the modified polyamides and their properties are listed in Table 1.

Example 9-11

0034Analogously to Example 1, glass fiber reinforced polyamides are produced and the products obtained are processed into shaped articles. The composition of the modified glass fiber reinforced polyamides and their properties are summarized in Table 2.<tables id="tabl0001" num="0001"><img file="EP0166321A2_D0006.tif" /></tables><tables id="tabl0002" num="0002"><img file="EP0166321A2_D0007.tif" /></tables>