High-stiffness polyamide with reduced water sorption

Abstract

The invention relates mainly to a composition comprising: 20 to 70% by weight of a polyamide component comprising a semi-crystalline aliphatic polyamide having on average at least 7 carbon atoms per nitrogen atom; 30 to 80% by weight of glass fibers; and 0 to 10% by weight of additives, the total of components (a), (b) and (c) adding up to 100%, characterized in that the semi-crystalline aliphatic polyamide has a total acidity, as measured by potentiometric titration, of 70 to 180, and preferably of 100 to 150 µeq / g.

Description

Title of the invention: High-stiffness polyamide with reduced water sorption technical field

[0001] The present patent application relates to a reinforced semi-crystalline aliphatic polyamide composition exhibiting improved dimensional stability and robust mechanical properties in the presence of moisture.

[0002] It also relates to its manufacturing process, articles obtained from it and the use of a semi-crystalline aliphatic polyamide for the manufacture of articles exhibiting improved dimensional stability and mechanical properties, particularly in terms of modulus. Previous technique

[0003] Polyamide formulations with very high stiffness are sought, for example, in the electrical and electronics fields for the manufacture of telephone casings or computer chassis. Such formulations can also be advantageous for reducing the weight of electronic equipment by allowing a reduction in the thickness of the components. A common method for obtaining high-stiffness polyamides is to formulate semi-crystalline aliphatic polyamides by adding reinforcements such as glass fibers.

[0004] The mechanical properties of such formulations depend on the properties of the polymer and the glass fibers, and on the polymer's ability to transfer stresses at the fiber-polymer interface. Humidity is one of the main external factors that can impact this interface and thus affect the mechanical properties, particularly the modulus.

[0005] Given their affinity for water, polyamides, particularly semi-crystalline aliphatic polyamides, are especially sensitive to water sorption. Absorbed water has a plasticizing effect on the polyamide and has several consequences on its properties, including: - cause swelling that affects the dimensional stability of the parts; and - decrease the modulus of the material, particularly at room temperature.

[0006] One way to improve the characteristics of polyamide formulations, in particular dimensional stability, and to have more robust mechanical properties, particularly in terms of modulus, is therefore to reduce their water sorption.

[0007] French patent FR 3 043 681 B1 describes the addition of semi-crystalline polyamide comprising 8 or more carbon atoms per nitrogen atom in formulations amorphous polyamide allows to improve their dimensional stability by reducing water absorption at 23°C at 50% RH compared to the expected value calculated from the weighted absorption of their components.

[0008] In the case of polyamide formulations reinforced with fillers, such as glass fibers, the absorbed water can also modify the interactions between the polyamide and the fillers.

[0009] US patent application 2017 / 0029621 A1 states that the use of a polyamide with specific end-chain groups limits the increase in molecular weight during high-temperature injection. The document is silent on the problems related to water sorption of polyamides and does not address polyamides reinforced with fillers. Summary of the invention

[0010] The invention therefore aims to provide a semi-crystalline aliphatic polyamide composition reinforced by fillers such as glass fibers exhibiting improved dimensional stability as well as robust mechanical properties, particularly in terms of modulus, with respect to humidity.

[0011] Indeed, the present invention is based primarily on the surprising observation that the water sorption of a semi-crystalline aliphatic polyamide composition can be limited by adjusting the nature and content of the amine and carboxylic groups at the end of the chain. Lower water sorption allows for better dimensional stability and, moreover, better stability of mechanical properties in humid environments.

[0012] Also, according to a first aspect, the invention relates to a composition comprising: a. 20 to 70% by weight of a polyamide component comprising a semi-crystalline aliphatic polyamide having on average at least 7 carbon atoms per nitrogen atom; b. 30 to 80% by weight of glass fibers; and c. 0 to 10% by weight of additives,

[0013] the total of components (a), (b) and (c) adding up to 100%,

[0014] characterized in that the semi-crystalline aliphatic polyamide has a total acidity, as measured by potentiometric titration, of 70 to 180, and preferably of 100 to 150 peq / g.

[0015] Advantageously, the semi-crystalline aliphatic polyamide has a total basicity, as measured by potentiometric titration, of between 10 and 100 peq / g.

[0016] Preferably, the aliphatic semi-crystalline polyamide is an XY-type polyamide, obtained by polycondensation of at least one diamine, in particular a diamine aliphatic with a straight or branched chain comprising 5 to 12 carbon atoms, and at least one dicarboxylic acid, in particular an aliphatic dicarboxylic acid with a straight or branched chain comprising 9 to 18 carbon atoms.

[0017] Alternatively, the aliphatic semi-crystalline polyamide can be a Z-type polyamide, obtained by polycondensation of at least one aminocarboxylic acid and / or at least one lactam, which may advantageously comprise 11 or 12 carbon atoms.

[0018] The aliphatic semi-crystalline polyamide may in particular be selected from the group consisting of PA 59, PA 510, PA 69, PA 512, PA 612, PA 109, PA 610, PA 1010, PA 1012, PA 11, PA 12 and PA 1212.

[0019] Glass fibers may include glass fibers with circular or non-circular cross-section.

[0020] According to one embodiment, the composition comprises 30 to 65% by weight of glass fibers.

[0021] Advantageously, the semi-crystalline polyamide has an inherent viscosity, as measured according to ISO 307:2007, but in a solution in m-cresol at 0.5% by weight at 20°C, ranging from 0.85 to 1.30 dl / g.

[0022] According to a second aspect, the invention relates to an article obtained from said composition, in particular by injection.

[0023] According to a third aspect, the invention relates to a method for manufacturing said composition, comprising the steps of: (i) preparing a mixture comprising: a) 20 to 70% by weight of a polyamide component comprising a semi-crystalline aliphatic polyamide having on average at least 7 carbon atoms per nitrogen atom and having a total acidity, as measured by potentiometric titration, of between 70 and 180 peq / g, b) 30 to 80% by weight of glass fibers; and c) 0 to 10% by weight of additives, the total of components (a), (b) and (c) adding up to 100%, and (ii) possible shaping of the mixture obtained in step (i).

[0024] According to a fourth aspect, the invention relates to the use of a semi-crystalline aliphatic polyamide comprising on average at least 7 carbon atoms per nitrogen atom and having a total acidity, as measured by potentiometric titration, of between 70 and 180 peq / g, for the manufacture of a low water sorption composition, and in particular as a matrix in the composition defined above. Description of embodiments Definition of terms

[0025] The term "polyamide" means a compound comprising at least two identical or distinct repeating units formed by polycondensation of a dicarboxylic acid and a diamine, a diisocyanate and a dicarboxylic acid, an amino acid, a lactam or a mixture thereof.

[0026] The nomenclature used to define polyamides is described in ISO 16396-1:2015 "Plastics — Polyamide (PA) materials for molding and extrusion — Part 1: Designation system, product marking and specification basis". When the polyamide is produced by the polycondensation of a dicarboxylic acid and a diamine, it is designated by (diamine in Ca).(diacid in Cb), where a represents the number of carbon atoms in the diamine and b represents the number of carbon atoms in the diacid. Polyamides produced by the condensation of two distinct monomers are called XY-type polyamides, and polyamides produced by the condensation of a single monomer, such as a lactam or an aminocarboxylic acid, are called Z-type polyamides.

[0027] The polyamide can be a homopolyamide, in which case it is composed of identical repeating units, or a copolyamide, in which case it comprises several distinct repeating units. Advantageously, when the polyamide is a copolyamide, it is derived from a mixture of monomers composed of a main monomer and no more than 10% by weight, and advantageously no more than 5% by weight, of an additional monomer.

[0028] The term "semi-crystalline polyamide" means a polyamide having a melting temperature (Tf) in DSC, as measured according to ISO 11357-3 of 2011, and an enthalpy of crystallization during the cooling step at a rate of 20K / min in DSC, measured according to ISO 11357-3 of 2013, greater than 30 J / g, preferably greater than 40 J / g.

[0029] The term "aliphatic polyamide" is meant to designate a polyamide resulting from the polycondensation of aliphatic monomers, preferably acyclic, and particularly with a linear chain.

[0030] The term "viscosity" refers to the inherent viscosity, which is measured according to ISO 307:2007, but in a 0.5% wt% m-cresol solution at 20°C, using a viscometer equipped with a Micro-Ubbelohde viscometric tube. The inherent viscosity is calculated using the following formula: l / c*ln (ts / t0), in which

[0031] c: the concentration of the solution

[0032] ts: the flow time of the solution

[0033] tO: the flow time of the solvent alone

[0034] The term "melting temperature" refers to the temperature at which a polymer, at least partially crystalline, transitions to a viscous liquid state, such that measured by differential scanning calorimetry (DSC) according to standard NF EN ISO 11 357-3 with a heating rate of 20°C / min.

[0035] The term "total acidity" of a polyamide means the total content of acidic functions, in particular acidic chain ends, especially of formula -COOH, as measured by potentiometric titration according to the protocol explained later.

[0036] The term "total basicity" of a polyamide means the total content of basic functions, in particular basic chain ends, especially of formula -NH2, as measured by potentiometric titration according to the protocol explained later.

[0037] According to the invention, the composition referred to in this application comprises: a. 20 to 70% by weight of a polyamide component comprising a semi-crystalline aliphatic polyamide having on average at least 7 carbon atoms per nitrogen atom; b. 30 to 80% by weight of glass fibers; and c. 0 to 10% by weight of additives,

[0038] the sum of components (a), (b) and (c) making 100%,

[0039] characterized in that the semi-crystalline aliphatic polyamide has a total acidity, as measured by potentiometric titration, of 70 to 180, and preferably of 100 to 150 peq / g.

[0040] Indeed, the present invention is based primarily on the surprising observation that the water sorption of a semi-crystalline aliphatic polyamide composition can be limited by adjusting the acidity of the polyamide, and in particular the nature and content of functional groups at the end of the chain. Lower water sorption allows for better dimensional stability and, moreover, better stability of mechanical properties in humid environments.

[0041] Furthermore, it has been found that for such compositions, loaded with glass fibers, the mechanical properties are more advantageous when the semi-crystalline aliphatic polyamide has a limited phosphoric acid content. Without wishing to be bound by this assumption, it is considered at this stage that this effect results from the unfavorable interaction with the glass fibers. Semi-crystalline polyamide

[0042] Component (a) of the composition of the invention, the semi-crystalline aliphatic polyamide, is characterized first of all in that it comprises on average at least 7 carbon atoms per nitrogen atom.

[0043] As mentioned previously, this polyamide can be obtained from the polycondensation of a dicarboxylic acid and a diamine, an amino acid, a lactam or mixtures thereof.

[0044] When the semi-crystalline aliphatic polyamide is a homopolyamide:

[0045] - obtained by polymerization of an amino acid or a lactam, the number of atoms the number of carbon atoms in this amino acid or lactam is at least 7, advantageously at least 8, preferably greater than or equal to 9, in particular greater than or equal to 10; or

[0046] - obtained by polymerization of a diacid with a diamine and comprises a motif amide corresponding to the formula (diamine in Ca).(diacid in Cb), the sum (a + b) / 2 being greater than or equal to 7, advantageously greater than or equal to 8, preferably greater than or equal to 9, and in particular greater than or equal to 10.

[0047] Thus, PA 6.12 is a polyamide comprising 9 carbon atoms per nitrogen atom and PA 613 is a polyamide comprising 9.5 carbon atoms.

[0048] The semi-crystalline aliphatic polyamide can be obtained from linear monomers and / or from branched monomers. Preferably, it is a polyamide obtained, partially or entirely, from linear monomers.

[0049] According to a first embodiment, the semi-crystalline aliphatic polyamide is a Z-type polyamide, obtained by polycondensation of at least one aminocarboxylic acid or at least one lactam.

[0050] The semi-crystalline aliphatic polyamide may thus comprise at least one motif obtained from an amino acid selected from 9-aminononanoic acid, 10-aminodecanoic acid, 11-aminoundecanoic acid, and 12-aminododecanoic acid. Advantageously, the polyamide comprises at least one motif obtained from 11-aminoundecanoic acid or 12-aminododecanoic acid.

[0051] Alternatively, the semi-crystalline aliphatic polyamide may comprise at least one motif obtained from a lactam selected from pyrrolidinone, piperidinone, caprolactam, enantholactam, caprylolactam, pelargolactam, decanolactam, undecanolactam, and laurolactam.

[0052] If the semi-crystalline aliphatic polyamide is a homopolyamide comprising a motif obtained from a lactam, this lactam contains at least 7 carbon atoms and is therefore particularly chosen from enantholactam, caprylolactam, pelargolactam, decanolactam, undecanolactam, and laurolactam. Advantageously, the polyamide comprises at least one motif obtained from undecanolactam or laurolactam.

[0053] Preferably, the semi-crystalline aliphatic polyamide is obtained from the polycondensation of monomers comprising at least one aminocarboxylic acid and / or at least one lactam comprising 11 or 12 carbon atoms.

[0054] Advantageously, the polyamide comprises less than 10% by weight, in particular less than 5% by weight, and especially less than 0.1% by weight or none at all of a motif derived from caprolactam.

[0055] According to another embodiment, the semi-crystalline aliphatic polyamide is an XY type polyamide and comprises at least one motif corresponding to the formula (diamine in Ca).(diacid in Cb).

[0056] The Ca diamine may, in particular, be a linear aliphatic diamine. Similarly, the Cb diacid may, in particular, be a linear aliphatic diacid.

[0057] Preferably, when the Ca aliphatic diamine is linear, it is chosen from butanediamine (a=4), pentanediamine (a=5), hexanediamine (a=6), heptanediamine (a=7), octanediamine (a=8), nonanediamine (a=9), decanediamine 20 (a=10), undecanediamine (a=11), dodecanediamine (a=12), tridecanediamine (a=13), tetradecanediamine (a=14), hexadecanediamine (a=16), octadecanediamine (a=18), octadecanediamine (a=18), eicosanediamine (a=20), docosanediamine (a=22) and diamines obtained from fatty acids.

[0058] Preferably, when the aliphatic diacid is linear, it is chosen from succinic acid (b=4), pentanedioic acid (b=5), adipic acid (b=6), heptanedioic acid (b=7), octanedioic acid (b=8), azelaic acid (b=9), sebacic acid (b=10), undecanedioic acid (b=11), dodecanedioic acid (b=12), brassylic acid (b=13), tetradecanedioic acid (b=14), hexadecanedioic acid (b=16), octadecanoic acid (b=18), octadecenedioic acid (b=18), eicosanedioic acid (b=20), docosanedioic acid (b=22) and the fatty acid dimers, especially those containing 36 carbons.

[0059] The fatty acid dimers mentioned above can be obtained by oligomerization or polymerization of long-chain unsaturated monobasic fatty acids (such as linoleic acid and oleic acid), as described in particular in document EP 0 471 566.

[0060] However, the monomers used for the preparation of the semi-crystalline aliphatic polyamide (amino acids, diamines, diacids) may also be some or all branched. Thus, 2-methyl-1,5-diaminopentane can be used as a branched diamine.

[0061] Advantageously, the XY type aliphatic polyamide is obtained by polycondensation of at least one straight-chain or branched aliphatic diamine comprising 5 to 12 carbon atoms and at least one straight-chain or branched aliphatic dicarboxylic acid comprising 9 to 18 carbon atoms.

[0062] Preferably, the monomers used for the preparation of the semi-crystalline aliphatic polyamide are saturated compounds.

[0063] Some of the monomers listed above may be replaced by other monomers. Thus, some of the aliphatic dicarboxylic acids may be replaced by one or more aromatic or cycloaliphatic dicarboxylic acids. Similarly, some of the aliphatic diamines may be replaced by cycloaliphatic and / or aromatic or araliphatic diamines. Preferably, this replacement is carried out in very limited quantities, up to 10%, in particular up to 5% and especially up to 2.5% by weight of all monomers.

[0064] The aliphatic semi-crystalline polyamide useful in the composition of polyamide can be chosen in particular from the group consisting of: PA 410, PA59, PA 510, PA 69, PA 610, PA512, PA 612, PA 613, PA 614, PA 615, PA 616, PA 618, PA 910, PA 912, PA 913, PA 914, PA 915, PA 916, PA 918, PA 936, PA 109, PA 1010, PA 1012, PA 1013, PA 1014, PA 11, PA 12, PA 1210, PA 1212, PA 1213, PA 1214, as well as from their copolymers and mixtures.

[0065] Particularly preferred are the aliphatic semi-crystalline polyamides PA59, PA 510, PA 69, PA 610, PA512, PA 612, PA 109, PA 1010, PA 1012, PA 11, PA 12 and PA 1212 as well as their copolymers and mixtures.

[0066] Advantageously, the polyamide composition does not include short-chain semi-crystalline polyamides such as PA 6 and PA 66. Indeed, these polyamides have very high water absorption rates and therefore do not allow the dimensional stability required for the intended applications to be achieved.

[0067] The composition according to the invention may comprise one, two or more distinct semi-crystalline polyamides. Preferably, the composition comprises one or two distinct semi-crystalline polyamides.

[0068] Component (a), the semi-crystalline aliphatic polyamide, is further characterized in that it has a total acidity, as measured by potentiometric titration, of between 70 and 180, and preferably between 100 and 150 peq / g.

[0069] According to certain embodiments, the total acidity of the aliphatic semi-crystalline polyamide in the composition can vary from 70 to 75 peq / g; or from 75 to 80 peq / g, or from 80 to 85 peq / g; or from 85 to 90 peq / g; or from 90 to 95 peq / g; or from 95 to 100 peq / g; or from 100 to 105 peq / g, or from 105 to 110 pg; or from 110 to 115 peq / g; or from 115 to 120 peq / g; or from 120 to 125 peq / g; or from 125 to 130 peq / g; or from 130 to 135 peq / g; or from 135 to 140 peq / g, or from 145 to 150 peq / g; or from 150 to 155 peq / g; or from 155 to 160 peq / g; or from 160 to 165 peq / g; or from 165 to 170 peq / g; or from 170 to 175 peq / g; or 175 to 180 peq / g.

[0070] The total acidity of the semi-crystalline polyamide reflects in particular the content of carboxylic groups at the end of the chain.

[0071] The polyamide may contain residues of mineral acids used as catalysts during its synthesis, particularly phosphoric acid. These catalysts may contribute to the acidity of the polyamide. However, they do not produce the favorable effects reported in this application.

[0072] Also, the aliphatic semi-crystalline polyamide advantageously has a phosphoric acid content, as measured by P31 NMR according to the protocol described above far, which does not exceed 8000 ppm, advantageously 7000 ppm, in particular 6000 ppm and especially 5000 ppm.

[0073] Advantageously, the aliphatic semi-crystalline polyamide also has a total basicity, as measured by potentiometric titration, of less than 100, in particular from 10 to 100 peq / g and preferably less than 80, in particular less than 60 peq / g and in particular less than 40 peq / g and especially from 10 to 30 peq / g.

[0074] According to certain embodiments, the basicity of the aliphatic semi-crystalline polyamide can vary from 10 to 15 peq / g; or from 15 to 20 peq / g; or from 20 to 25 peq / g; or from 25 to 30 peq / g; or from 30 to 35 peq / g; or from 35 to 40 peq / g; or from 40 to 45 peq / g; or from 45 to 50 peq / g; or from 50 to 55 peq / g; or from 55 to 60 peq / g; or from 60 to 65 peq / g; or from 65 to 70 peq / g; or from 70 to 75 peq / g; or from 75 to peq / g; or from 85 to 90 peq / g; or from 90 to 95 peq / g; or 95 to 100 peq / g.

[0075] The total basicity of the semi-crystalline polyamide reflects in particular the content of amine groups, and the carboxylic groups neutralized by strong bases such as KOH at the end of the chain.

[0076] The total basicity and total acidity of the polyamide can be adjusted by adding chain limiter during synthesis.

[0077] Advantageously, the polyamide according to the invention is limited by a linear aliphatic monocarboxylic acid in C2-C18, a linear aliphatic monoamine in C4-C18, a linear aliphatic dicarboxylic acid in C3-C36 and / or a linear aliphatic diamine in C4-C18.

[0078] The acid used as a chain limiter can be selected from acetic acid, propionic acid, lactic acid, valeric acid, caproic acid, capric acid, lauric acid, tridecylic acid, myristic acid, palmitic acid, stearic acid, pivalic acid, isobutyric acid, succinic acid, pentanedioic acid, adipic acid, heptanedioic acid, octanedioic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid, tetradecanedioic acid, hexadecanedioic acid, octadecanedioic acid, octadecenedioic acid eicosanedioic and docosanedioic acid.

[0079] Preferably, the polyamide is limited by a linear aliphatic C6-C12 monocarboxylic acid and / or a linear aliphatic C6-C12 dicarboxylic acid, and particularly preferably by a linear aliphatic C6-C12 dicarboxylic acid. The preferred acids are adipic acid, sebacic acid and lauric acid.

[0080] The amine used as a chain limiter can be chosen from butylamine, hexylamine, octylamine, decylamine, laurylamine, stearylamine, the diethylamine, dipropylamine, dibutylamine, hexanediamine, heptanediamine, octanediamine, nonanediamine, decanediamine, rundecanediamine, dodecanediamine.

[0081] Preferably, the polyamide according to the invention is limited by a C6-C12 monoamine and / or a C6-C12 diamine. Preferably, decanediamine and laurylamine are used.

[0082] As mentioned above, the total basicity of the polyamide can also be increased by neutralizing the carboxylic groups at the ends of the chain with strong bases, such as KOH.

[0083] Advantageously, the semi-crystalline polyamide also has an inherent viscosity as measured according to ISO 307:2007 of 0.85 to 1.30 dl / g, preferably of 0.90 to 1.1 dl / g.

[0084] According to certain embodiments, the inherent viscosity of the aliphatic semi-crystalline polyamide in the composition can vary from 0.85 to 0.90 dl / g; or from 0.90 to 0.95 dl / g, or from 0.95 to 1.0 dl / g; or from 1.1 to 1.15 dl / g; or from 1.15 to 1.2 dl / g; or from 1.15 to 1.2 dl / g; or from 1.2 to 1.25 dl / g, or from 1.25 to 1.3 dl / g.

[0085] According to the invention, the aliphatic semi-crystalline polyamide represents from 20% to 70% by weight of the composition.

[0086] According to certain embodiments, the content of aliphatic semi-crystalline polyamide in the composition can vary from 20 to 25% by weight; or from 25 to 30% by weight, or from 30 to 35% by weight; or from 35 to 40% by weight; or from 45 to 50% by weight; or from 50 to 55% by weight; or from 55 to 60% by weight, or from 60 to 65% by weight; or from 65 to 70% by weight. Fiberglass

[0087] The composition according to the invention also comprises glass fibers as reinforcement.

[0088] For the purposes of this invention, glass fiber means any glass fiber, in particular as described by Frederick T. Wallenberger, James C. Watson and Hong Li, PPG industries Inc. (ASM Handbook, Vol 21: composites (#0678IG), 2001 ASM International).

[0089] Preferably, the glass fibers are short and have an average length of between 2 and 13 mm, preferably from 3 to 8 mm before introduction into the composition. Once introduced into the composition, they preferably have an average length, as measured by optical microscopy (for example after dissolution or calcination of the matrix), ranging from 50 to 300 pm, and in particular from 100 to 250 pm.

[0090] The nature of the glass used for the glass fibers is in principle of little importance in the implementation of the invention. Thus, the glass fibers can be made of any type of glass, such as type E, R, S2, NE or T glass.

[0091] Glass fibers can be solid and / or hollow, advantageously they are solid.

[0092] Glass fibers can be:

[0093] - either with a circular cross-section, preferably with a diameter between 4 pm and 25 pm, in particular from 4 to 15 pm.

[0094] - either with a non-circular cross-section, in particular elliptical, oval or flat, with preferably an L / D ratio (L representing the largest dimension of the cross-section of the fiber and D the smallest dimension of the cross-section of said fiber) of 2 to 8, in particular 2 to 4. L and D can be measured by scanning electron microscopy (SEM).

[0095] Furthermore, the fibers can have a non-circular cross-section of different shapes, for example star-shaped, flake-shaped, flat, cruciform, polygonal or ring-shaped.

[0096] The composition of the invention comprises 30 to 80%, in particular 30 to 65% by weight, of glass fibers. It may comprise different types of glass fibers, and optionally, in addition to glass fibers, other reinforcements such as solid and / or hollow glass beads.

[0097] According to certain embodiments, the glass fiber content in the composition can vary from 30 to 35% by weight; or from 35 to 40% by weight, or from 40 to 45% by weight; or from 45 to 50% by weight; or from 50 to 55% by weight; or from 55 to 60% by weight; or from 60 to 65% by weight, or from 65 to 70% by weight; or from 70 to 75% by weight; or from 75 to 80% by weight. Additives

[0098] The composition of the invention may also include one or more additives. The additives may in particular be chosen from among the usual additives, such as colorants, stabilizers, surfactants, nucleating agents, brighteners, antioxidants, lubricants, waxes and mixtures thereof.

[0099] Stabilizers can be organic or mineral. Common stabilizers used with polymers include, for example, phenols, phosphites, UV absorbers, HALS (Hindered Amine Light Stabilizer) type stabilizers, and metal iodides. Examples include Irganox® 1010, 245, 1098 from BASF, Irgafos® 168, 126 from BASF, Tinuvin® 312, 770 from BASF, Iodide P201 from Ciba, and Nylostab® S-EED from Clariant.

[0100] Lubricants may include, in particular, a stearate or a wax binder.

[0101] Waxes may in particular be an amorphous wax such as beeswax, silicone wax, polyethylene wax, oxidized polyethylene wax, ethylene copolymer wax, montane wax and polyether wax.

[0102] The content of additives is from 0 to 10% by weight relative to the total weight of the composition.

[0103] According to certain embodiments, the content of additives in the composition may vary from 0 to 0.5% by weight; or from 0.1 to 0.5% by weight, or from 0.5 to 1.0% by weight; or from 1 to 1.5% by weight; or from 1.5 to 2.0% by weight; or from 2.0 to 2.5% by weight; or from 2.5 to 3.0% by weight, or from 3.5 to 4.0% by weight; or from 4.0 to 4.5% by weight; or from 4.5 to 5.0% by weight; or from 5.0 to 5.5% by weight; or from 5.5 to 6.0% by weight, or from 6.5 to 7.0% by weight; or from 7.0 to 7.5% by weight; or from 7.5 to 8.0% by weight; from 8.0 to 8.5% by weight; or from 8.5 to 9.0% by weight, or from 9.0 to 9.5% by weight; or from 9.5 to 10.0% by weight.

[0104] The compositions described exhibit excellent dimensional stability and, moreover, very good stability of mechanical properties, in particular of the modulus, in humid environments. Manufacturing process of the composition

[0105] According to a second object, the invention relates to a method for preparing the composition as defined above.

[0106] This process comprises the steps of: (i) Preparation of a mixture comprising: a) a polyamide component comprising 20 to 70% by weight of semi-crystalline aliphatic polyamide having on average at least 7 carbon atoms per nitrogen atom and having a total acidity, as measured by potentiometric titration, of between 70 and 180 peq / g, b) 30 to 80% by weight of glass fibers; and c) 0 to 10% by weight of additives, the total of components (a), (b) and (c) adding up to 100%, and (ii) Possible shaping of the mixture obtained in step (i).

[0107] Step (i) can be carried out by any method which makes it possible to obtain a homogeneous mixture containing the composition according to the invention, and possibly other additives, such as molten extrusion, compaction, or even a roller mixer.

[0108] More particularly, step (i) can be carried out by mixing all the ingredients in a molten state in a so-called direct process. The composition according to the invention can also be prepared by dry blending. Advantageously, the composition can be obtained in the form of granules, generally by compounding on a tool known to the person skilled in the art such as a twin-screw extruder, a co-mixer or an internal mixer.

[0109] The composition according to the invention obtained by the preparation process described above can then be processed for a further use or transformation known to those skilled in the art, in particular by injection molding, calendering, extrusion, preferably by injection molding. The processing can be carried out directly from the mixture in the molten state or from the dry mixture mentioned above (step ii).

[0110] The method for preparing the composition according to the invention can also use a twin-screw extruder feeding, without intermediate granulation, an injection molding machine or an extruder according to an implementation device known to those skilled in the art. Articles obtained from the composition

[0111] The composition according to the invention is useful for the preparation of articles, in particular intended to be assembled, whose mechanical properties such as the modulus vary little when exposed to humid conditions.

[0112] According to a third object, the invention therefore relates to an article obtained from the composition as defined above.

[0113] This may include, in particular, a shaped article, a fibre, a fabric, a film, a sheet, a rush or a tube.

[0114] In particular, this may include manufactured articles, such as parts intended for sporting goods. Examples of sporting goods include sports shoes, sports equipment such as ice skates or other winter sports and mountaineering equipment, ski bindings, snowshoes, sports bats, boards, horseshoes, flippers, golf balls, and recreational vehicles. More generally, it may also include leisure and DIY items, tools and road maintenance equipment subject to climatic and mechanical stresses, and protective items such as helmet visors, goggles, and goggle temples.

[0115] We can also mention automotive parts, such as headlight protectors, rearview mirrors, small parts for off-road vehicles, tanks, in particular, for mopeds, motorcycles, scooters, subject to mechanical and chemical aggressions, screws, cosmetic articles subject to mechanical and chemical aggressions, lipstick tubes, pressure gauges, aesthetic protective elements such as gas cylinders.

[0116] We can finally and in particular mention parts for electronic articles for which lightness is sought and which require compliance with dimensions, for example parts for mobile phones, computers, tablets, televisions, digital cameras, digital game consoles, drones or printers. Use

[0117] According to a fourth object, the invention relates to the use of a semi-crystalline aliphatic polyamide as described above for the manufacture of articles exhibiting improved modulus stability in humid environments.

[0118] According to one embodiment, semi-crystalline aliphatic polyamide is used as a matrix in a polyamide composition as defined above.

[0119] The invention also relates to a method for increasing the stability of the modulus of a composition comprising a semi-crystalline polyamide as defined above. This application is particularly advantageous for very rigid compositions, exhibiting a tensile modulus greater than 7000 MPa, and especially those between 10000 and 25000 MPa.

[0120] The invention will be explained in more detail in the following examples. Examples

[0121] The materials used in the exemplified compositions are detailed below. Polyamides:

[0122] PA 610: PA 610 A is obtained by polycondensation of hexanediamine and sebacic acid with an excess of 1.03% by weight relative to the total quantity of monomers in stoichiometric proportions, according to the following process. All the monomers are loaded into a reactor equipped with a stirrer. To improve heat exchange and facilitate monomer melting, 15% by weight of water is added relative to the total quantity of monomers. The reactor is then inerted by vacuum / nitrogen cycles to remove residual oxygen, and then heated to a first plateau of 160-170°C under 8 bar. After one hour, the temperature of the mixture is increased to 240°C at a pressure of 17 bar. The pressure is then reduced to atmospheric pressure while the temperature is gradually increased to 255°C. At this temperature, the polycondensation reaction is carried out under nitrogen purging. The reaction is complete when the target viscosity is reached.The polyamide is then extruded and granulated.

[0123] The polymer obtained, free of phosphoric acid, has the inherent viscosity indicated in Table 1 below.

[0124] PA 610 B obtained by polycondensation of hexanediamine and sebacic acid charged in excess of 1.24% by weight with 3600 ppm KOH relative to the total quantity of monomers in stoichiometric proportions according to the process described above.

[0125] The polymer obtained, free of phosphoric acid, has the inherent viscosity indicated in Table 1 below.

[0126] PA 610 C obtained by polycondensation of hexanediamine and sebacic acid in stoichiometric proportions with 3600 ppm of KOH according to the process described above. The resulting polyamide, free of phosphoric acid, has the inherent viscosity indicated in Table 1.

[0127] PA 11: PA 11 A obtained by polycondensation as follows. 11-Aminoundecanoic acid, 15 wt% water, and 0.67 wt% adipic acid, both quantities being calculated relative to the amount of 11-Aminoundecanoic acid, are loaded into a reactor and then placed under an inert atmosphere. The reaction mixture is then heated to 235°C while maintaining stirring. The reaction mixture is maintained at 235°C under a pressure of 20 bar for 1.5 hours. Then, the pressure is reduced to 12 bar while maintaining the temperature at 235°C. The material is then transferred to a polymerizer under nitrogen purging at 235°C. The temperature is maintained under nitrogen purging for 1.5 hours. The material is then extruded into granules.

[0128] The polyamide obtained, free of phosphoric acid, has the inherent viscosity indicated in Table 1.

[0129] PA 11 B obtained by polycondensation as described for PA 11 A, except that adipic acid is replaced by 0.47% by weight of decanediamine relative to the amount of 11-aminoundecanoic acid. The polyamide obtained, devoid of phosphoric acid, has the inherent viscosity indicated in Table 1.

[0130] PA 11C obtained by polycondensation as described for PA 11 A, except that adipic acid is replaced by 0.25% by weight of KOH relative to the amount of 11-aminoundecanoic acid. The resulting polyamide, free of phosphoric acid, has the inherent viscosity shown in Table 1. Reinforcements

[0131] FV 1: flat glass fibers, the cross-section of which is defined by a major axis of 28 pm and a minor axis of 7 pm and an average length of 3 mm, -Marketed under the name CSG3PA-820S by Nitto Boseki Co., Ltd;

[0132] FV 2: glass fibers with a circular cross-section, a diameter of 10 µm and an average length of 3 mm, -Marketed under the name CSX3J 451 by Nitto Boseki Co., Ltd.

[0133] The properties of the polyamides and the compositions obtained are measured according to the following protocols. Inherent viscosity

[0134] The inherent viscosity is measured according to ISO 307:2007 except when using a 0.5% by weight m-cresol solution and performing the measurement at 20°C. Phosphoric acid content

[0135] The phosphoric acid content of the polyamide was determined by P31 NMR on an Avance 400 NEO instrument marketed by BRUKER. 400 mg of polyamide was solubilized overnight at room temperature in 3 mL of a 2:1 volume ratio of HFIP / CD2C12. The analysis was performed using the internal standard method (Irgafos 168). 20 mg of Irgafos was added to the previous solution, allowing the relationship between the amount of phosphorus and the mass of phosphorus required to calculate the phosphoric acid content to be determined. Total acidity

[0136] Acidity is measured according to the following method. 1 g of polyamide is dissolved in 80 mL of hot benzyl alcohol at 130°C. The sample is then cooled to 80°C. It is then titrated by potentiometric titration using a Metrohm titrator (model 888) with a combined pH electrode, with a 0.02 N tetrabutylammonium hydroxide solution. The volume of titration solution added at the inflection point of the solution's potential corresponds to the equivalent volume Veq, from which the total acidity is calculated using the following formula:

[0137] [Math.l] Veq X [TBAOH] Total acidity (meq / g) = -------------- ïïl

[0138] in which Veq denotes the equivalent volume, [TBAOH] denotes the concentration of the tetrabutylammonium hydroxide solution (0.02 N), m denotes the mass of the sample (1g). Total basicity

[0139] Basicity is measured according to the following method. 1 g of polyamide is dissolved in 80 mL of hot meta-cresol at 130°C. The sample is then cooled to 80°C. It is then titrated by potentiometric titration using a Metrohm titrator (model 888) with a combined pH electrode, with a 0.02 N perchloric acid solution in acetic acid. The volume of titration solution added at the inflection point of the solution's potential corresponds to the equivalent volume Veq, from which the total basicity is calculated using the following formula:

[0140] [Math.2] Total basicity (meq / g) Veq X [HC1O4]

[0141] in which Veq denotes the equivalent volume. [HC1O4] denotes the concentration of the perchloric acid solution (0.02 N), m denotes the mass of the sample (1g). Humidity level

[0142] From the composition obtained, plates of dimensions 100x100x1 mm3 were produced by injection molding in an ENGEL VICTORY 500, 160T hydraulic press using the following parameters:

[0143] - Injection temperature (feed / nozzle): 265°C / 280°C

[0144] - Mold temperature: 100°C

[0145] - Holding time: 10s

[0146] - Material holding pressure: 700 bars

[0147] - Cooling time: 35s

[0148] These plates are then dried in an oven at 80°C until a water content of 0.02% by weight is reached. The plates are then weighed before being placed either in water at a temperature of 23°C or in a climate-controlled environment at 23°C and 50% relative humidity.

[0149] Monitoring the weight of the plates as a function of the time spent in the respective environment by weighing allows the water absorption of the material to be determined. Weighing is carried out until 3 identical measurements are obtained, indicating the end of water absorption.

[0150] At the end of the experiment, the water content is checked on a piece of approximately 1g of plate, by desorption of the water in an oven at 170°C for 20 min and then titration of the water thus desorbed according to the Karl Fischer method in a titrator (Metrohm Titrino 795 KFT volumetric model), using the reagent "Hydranal titrant 2e with solvent E". Module (E)

[0151] Dumbbells according to ISO 527-2 IA were produced by injection molding in an ENGEL VICTORY 500, 160T hydraulic press, using the following parameters:

[0152] - Injection temperature (feed / nozzle): 285°C / 295°C

[0153] - Mold temperature: 100°C

[0154] - Holding time: 10s

[0155] - Material holding pressure: 700 bars

[0156] - Cooling time: 15s

[0157] The tensile strength was measured in the dry state (Esec) and then after being saturated with water (Esat), i.e., after 1096 h in water at 70°C and 1272 h in water at 23°C, respectively. The tensile test was performed on an MTS 810 machine from MTS Systems equipped with hydraulic jaws. The tensile test was carried out at 23°C. at a speed of 1 mm / min for the module and 5 mm / min for the determination of the stress.

[0158] The module is calculated according to ISO 527-1 (2012).

[0159] Tensile strength (oR)

[0160] The breaking stress was determined to be the maximum stress observed on the stress-strain curve from a tensile test carried out according to ISO 527-1 (2012). EXAMPLES 1 to 3

[0161] Compositions comprising a polyamide and glass fibers were prepared according to the indications in Table 1 on a Coperion ZSK 26 MC twin-screw extruder with a lateral feed channel for the introduction of the glass fibers, using the following parameters:

[0162] Machine temperature: 270°C Screw speed: 250 rpm Extruder output: 16 kg / h

[0163] The polyamide is introduced into the main well.

[0164] The results obtained with the compositions of the invention are shown in the following table 1.

[0165] [Tables 1] Compositions and Moisture Contents Example Polyamide Glass Fibers [% by weight] Polyamide Properties Composition Moisture Content [%] Inherent Viscosity [dl / g] Total Acidity (peq / g) Total Basicity (peq / g) Weighing Titration 1 PA 610 A 50 (FV1) 1.11 137 22 1.62a 1.54a 2 PA 610 B 50 (FV1) 0.89 116 92 2.10a 2.32a 3 PA 11 A 50 (FV2) 0.98 103 18 ND 0.79b Cl PA 610 C 50 (FV1) 0.96 47 153 2.61a 2.69a C2 PA 11 B 50 (FV2) 1.35 17 55 ND 0.86b C3 PA 11 C 50 (FV2) 1.00 46 118 ND 1.09ba after saturation in water at 70°C - 1096 hb after saturation in water at 23°C - 1272 h

[0166] [Tables2] Mechanical Properties Examples E Sec (MPa) E sat (MPa) AEb (%) o R sec (MPa) o R sat (MPa) AoRc (%) 1 15350 12050 -21% 224 152 -32% 2 15420 11760 -24% 231 152 -34% Cl 15390 9020 -41% 225 83 -63% bAE = [(Esat - Esec) / Esec]*100 cAor = [(oRsat - oRsec) / oRsec]*100 COMPARATIVE EXAMPLES Cl to C3

[0167] Examples 1 to 3 are repeated except that the polyamide in the composition is replaced with that indicated in Table 1 above.

[0168] The compositions obtained were analyzed in terms of water absorption and mechanical properties, in particular in terms of modulus and breaking stress, according to the protocols indicated in detail above.

[0169] The results together, gathered in Tables 1 and 2, highlight that for each polyamide studied, the water reabsorption is lower for the compositions according to the invention.

[0170] The study of mechanical properties such as the tensile modulus E and the tensile strength oR before and after water sorption reveals that these properties change significantly less in the compositions according to the invention. Indeed, the loss of modulus due to water reabsorption AE is significantly lower (21% and 24%) for the compositions according to the invention than for the comparison composition (41%). Similarly, the loss of tensile strength AoR is more limited (32% and 34%) for the compositions according to the invention compared to the comparison composition (63%).

[0171] Thus, the examples highlight that the semi-crystalline aliphatic polyamide compositions according to the invention exhibit improved dimensional stability as well as robust mechanical properties, particularly in terms of modulus, with respect to humidity.

[0172] It is therefore possible to limit the water sorption of a semi-crystalline aliphatic polyamide composition by adjusting the nature and content of amine and carboxylic groups at the end of the chain, which allows for better dimensional stability and also better stability of mechanical properties in humid environments. List of cited documents

[0173] US 2014 / 0342145 Al

[0174] US 2017 / 0029621 Al

[0175] JP 2017 / 155157

Claims

Claims

1. Use of an aliphatic semi-crystalline polyamide having on average at least 7 carbon atoms per nitrogen and having a total acidity, as measured by potentiometric titration of 100 to 150 peq / g, for the manufacture of a low water sorption composition having improved tensile modulus stability.

2. Use according to the preceding claim, wherein the aliphatic semi-crystalline polyamide is used as a matrix in a composition comprising: a. 20 to 70% by weight of a polyamide component comprising an aliphatic semi-crystalline polyamide having on average at least 7 carbon atoms per nitrogen atom; b. 30 to 80% by weight of glass fibers; and c. 0 to 10% by weight of additives, the total of components (a), (b) and (c) adding up to 100%.

3. Use according to claim 1 or 2, wherein the semi-crystalline aliphatic polyamide has a total basicity, as measured by potentiometric titration, of between 10 and 100 peq /

4. ë- Use according to one of claims 1 to 3, in which the aliphatic semi-crystalline polyamide is a polyamide of type XY, obtained by polycondensation of at least one diamine and at least one dicarboxylic acid.

5. Use according to claim 4, wherein the XY-type aliphatic semi-crystalline polyamide is obtained by polycondensation of at least one straight or branched chain aliphatic diamine having 5 to 12 carbon atoms and at least one straight or branched chain aliphatic dicarboxylic acid having 9 to 18 carbon atoms.

6. Use according to claim 1 to 3, wherein the aliphatic semi-crystalline polyamide is a Z-type polyamide, obtained by polycondensation of at least one aminocarboxylic acid and / or at least one lactam.

7. Use according to claim 6, wherein the at least one aminocarboxylic acid and / or at least one lactam has 11 or 12 carbon atoms.

8. Use according to one of claims 1 to 7, wherein the aliphatic semi-crystalline polyamide is selected from the group consisting of PA59, PA 510, PA 69, PA512, PA 612, PA 109, PA 610, PA 1010, PA 1012, PA 11, PA 12 and PA 1212.

9. Use according to claim 2 to 8, wherein the glass fibers are glass fibers with circular or non-circular section.

10. Use according to one of claims 2 to 9, in which the composition comprises 30 to 65% by weight of glass fibers.

11. Use according to one of claims 1 to 10, wherein the semi-crystalline polyamide has an inherent viscosity, as measured according to ISO 307:2007, but in a solution in m-cresol at 0.5% by weight at 20°C, ranging from 0.85 to 1.30 dl / g.