Modified polyamide composition

Abstract

A sulfonated aliphatic or aromatic compound for the production of a modified polyamide that can significantly increase the glass transition temperature of the polyamide is described. A polyamide composition including at least: one polyamide modified by a sulfonated compound, the compound being chemically bonded to the polymer chain of the polyamide; and reinforcing or filling agents is also described. The composition can be a composition to be molded, for example, in the form of granules or powder, to be used in the production of articles using an injection molding method.

Claims

1. A method of increasing glass transition temperature of a polyamide composition, the method comprising including an effective amount of a sulfonated aliphatic compound or a sulfonated aromatic compound as an agent to increase the glass transition temperature of the polyamide; wherein the polyamide composition comprises a polyamide modified by a sulfonated aliphatic compound or a sulfonated aromatic compound, said compound being chemically bonded to a polymer chain of the polyamide, wherein said modified polyamide is a polycondensate of at least a linear carboxylic diacid and a linear or cyclic diamine, and is present in an amount from 30% to 95% by weight relative to the total weight of the composition, wherein the polyamide is selected from the group consisting of polyamide 66, polyamide 610, polyamide 612, polyamide 1212, polyamide 46, polymethxylyene diamine (MXD6), polyamide 66/6T, mixtures thereof, and copolymers thereof; one or more fibrous reinforcing agent, wherein said reinforcing agent is present in an amount from 1% to 60% by weight relative to the total weight of the composition; and optionally an additive; wherein the sulfonated compound comprises at least one SO.sub.3X functional group, wherein SO.sub.3X represents SO.sub.3H or SO.sub.3M; and M is a group which replaces the proton H+ of SO.sub.3H to form an inactive salified group; and wherein the polyamide composition is moldable.

2. A polyamide composition comprising a mixture of: a polyamide modified by a sulfonated aliphatic compound or a sulfonated aromatic compound, said compound being chemically bonded to a polymer chain of the polyamide, wherein said modified polyamide is a polycondensate of at least a linear carboxylic diacid and a linear or cyclic diamine, and is present in an amount from 30% to 95% by weight relative to the total weight of the composition, wherein the polyamide is selected from the group consisting of polyamide 66, polyamide 610, polyamide 612, polyamide 1212, polyamide 46, polymethxylylene diamine (MXD6), polyamide 66/6T, mixtures thereof, and copolymers thereof; one or more fibrous reinforcing agent, wherein said reinforcing agent is present in an amount from 1% to 60% by weight relative to the total weight of the composition; and optionally an additive; wherein the sulfonated compound comprises at least one SO.sub.3X functional group, wherein SO.sub.3X represents SO.sub.3H or SO.sub.3M; and M is a group which replaces the proton H+ of SO.sub.3H to form an inactive salified group; and wherein the polyamide composition is moldable.

3. The composition as claimed in claim 2, wherein the sulfonated compound is a sulfonated aromatic compound.

4. The composition as claimed in claim 2, wherein the sulfonated compound is chemically bonded to the polyamide chain to form a covalent bond via at least one functional group capable of reacting with the amine functional group or carboxylic add functional group of at least one monomer of the polyamide.

5. The composition as claimed in claim 4, wherein the sulfonated compound is located in the polymer chain of the polyamide or at the chain end of the polyamide.

6. The composition as claimed in claim 2, wherein the sulfonated compound is represented by the general formula (I):
(Z).sub.n—Y—(SO.sub.3X).sub.m  (I) wherein SO.sub.3X represents SO.sub.3H or SO.sub.3M; M is a group which replaces the proton H+ of SO.sub.3H to form an inactive salified group; m is between 1 and 10; Y is a linear or cyclic, aromatic or aliphatic hydrocarbon radical containing from 2 to 100 carbon atoms, and capable of containing hetero atoms Z is a functional group capable of reacting with the amine or carboxylic acid functional groups of the monomers of the polyamide; and n lies between 1 and 10.

7. The composition as claimed in claim 2, wherein the sulfonated compound is selected from the group consisting of: sodium 5-sulfoisophthalic acid, lithium 5-sulfoisophthalic acid, sodium-4-carboxybenzene sulfonate, sodium-3-carboxybenzene sulfonate, sodium-2-carboxybenzene sulfonate, lithium-3-carboxybenzene sulfonate, potassium-3-carboxybenzene sulfonate, sodium-3-carbomethoxybenzene sulfonate, potassium-2-carbopropoxy-benzene sulfonate, sodium-2-carbomethoxyethylbenzene sulfonate, potassium-3-aminomethylbenzene sulfonate, sodium-2-aminoethylbenzene sulfonate and potassium-3-aminopropylbenzene sulfonate.

8. The composition as claimed in claim 2, wherein the modified polyamide comprises from 0.1% to 70 mol % of sulfonate unit relative to the total number of moles of units constituting the polymer chain.

9. The composition as claimed in claim 2, wherein the modified polyamide is obtained by addition of the sulfonated compound in polymerization of the polyamide in the melted state, in the presence of at least one monomers of the polyamide.

10. The composition as claimed in claim 2, wherein the modified polyamide is obtained by addition of the sulfonated compound hot-mixed with a formed polyamide or a partially formed polyamide.

11. The composition as claimed in claim 2, wherein the fibrous reinforcing agentis selected from the group consisting of: glass fibers, carbon fibers, natural fibers, aramid fibers, nanotubes, hemp, and flax.

12. The composition as claimed in claim 2, wherein the additives are selected from the group consisting of: lubricants, fire retardants, plasticizers, nucleating agents, impact modifiers, catalysts, light stabilizers, heat stabilizers, antioxidants, antistatic agents, colorants, matting agents, and molding aid additives.

13. An article obtained by shaping of a composition as claimed in claim 2 by a process of molding or extrusion.

14. The composition as claimed in claim 4, wherein the at least one functional group capable of reacting with the amine or carboxylic acid functional groups is selected from the group consisting of amine, carboxylic acid, aldehyde, anhydride, a hydroxyl, a ketone and derivatives thereof.

15. The composition as claimed in claim 8, wherein the modified polyamide comprises from 0.1 mol % to 70 mol % of sulfonate unit relative to the total number of moles of diacid or diamine and/or amino acid units in the polymer chain.

16. The composition as claimed in claim 2, wherein the polyamide obtained by polycondensation of at least one linear dicarboxylic acid with at least one linear or cyclic diamine is selected from the group consisting of polyamide 66, polyamide 610, polyamide 612, polyamide 1212, polyamide 46, and polymethxylylene diamine (MXD6).

17. The composition as claimed in claim 2, wherein the composition has an increased glass transition temperature relative to a comparable composition not containing the sulfonated aliphatic, compound or the sulfonated aromatic compound.

18. The composition as claimed in claim 2, wherein the composition has an increased elastic modulus relative to a comparable composition not containing the sulfonated aliphatic compound or the sulfonated aromatic compound.

19. The composition as claimed in claim 2, wherein the modified polyamide is present in an amount of from 40% to 80% by weight relative to the total weight of the composition.

Description

EXPERIMENTAL SECTION

Definitions

(1) Contents of terminal acid (GTC) and amine (GTA) groups: assayed by potentiometry, expressed in meq/kg.

(2) When the sulfonated compound is a monofunctional monosulfonate, the content of terminal sulfonate groups (GTS) can be calculated from the quantities of reagents introduced into the polymerization reactor.

(3) Number average molecular weight Mn determined by the formula Mn=2.10.sup.6/(GTA+GTC+GTS) and expressed in g/mol.

(4) When the sulfonated compound is a monofunctional monosulfonate, the chain end sulfonate number per chain can be calculated in the following manner: Nsulfonate/chain=GTS/((GTA+GTC+GTS)/2).

(5) Melting point (T.sub.f) and associated enthalpy (ΔHf), crystallization temperature on cooling (T.sub.c): determined by differential scanning calorimetry (DSC) by means of a Perkin Elmer Pyris 1 instrument, at a speed of 10° C./min. The degree of crystallinity is obtained by the calculation χc=ΔHf/ΔHf°, with ΔHf° the enthalpy of fusion of a pure crystal of polyamide (ΔHf°(PA66)=188 J/g). Glass transition temperature (T.sub.g) determined on the same instrument at a speed of 40° C./min.

Comparative Example 1

Non-modified PA 66

(6) Into a polymerization reactor are introduced 92.6 kg (353 mol) of N salt (1:1 salt of hexamethylene diamine and adipic acid), 84 kg of demineralized water and 6.4 g of Silcolapse 5020® antifoaming agent. The polyamide 66 is produced by a standard polymerization method of the polyamide 66 type, with 30 minutes of finishing. The polymer obtained is cast in rod form, cooled and made into granule form by chopping the rods.

(7) The polymer obtained displays the following characteristics: GTC=70.2 meq/kg, GTA=51.5 meq/kg, Mn=16430 g/mol.

(8) The polyamide 66 is semi-crystalline and has the following thermal characteristics: Tg=70.6° C., Tc=230.9° C., Tf=263.7° C., ΔHf=68.4 J/g thus χc=36.4%.

Comparative Example 2

Preparation of a PA 66/6I 80/20 Copolyamide

(9) Into a polymerization reactor are introduced 117.92 g (0.450 mol) of N salt (1:1 salt of hexamethylene diamine and adipic acid), 31.73 g of 61 salt (1:1 salt of hexamethylene diamine and isophthalic acid) (0.112 mol), 1.05 g of a solution of hexamethylene diamine (HMD) in 32.5% by weight solution in water (0.003 mol) and 135.74 g of demineralized water and 2 g of an aqueous solution of antifoaming agent. The polyamide 66/6I 80/20 is produced by a standard polymerization method of the polyamide 66 type, with 45 minutes of finishing at atmospheric pressure. The polymer obtained is cast in rod form, cooled and made into granule form by chopping the rods.

(10) The polymer obtained displays the following characteristics: GTC=86.1 meq/kg, GTA=59.1 meq/kg, Mn=13800 g/mol.

(11) The polyamide 66/6I 80/20 is semi-crystalline and has the following thermal characteristics: Tg=77.9° C., Tc=194.4° C., Tf=239.6° C., ΔHf=42.6 J/g thus χc=22.7%. The introduction of the aromatic ring of the isophthalic acid induces a slight increase in the Tg of PA 66 (+7° C.) for a decrease in the degree of crystallinity of 38% compared to the PA 66.

Example 3

Preparation of a Polyamide 66 Containing about 5 mol.-% of SBA

(12) Into a polymerization reactor are introduced 87.2 kg (332.5 mol) of N salt (1:1 salt of hexamethylene diamine and adipic acid), 4057 g of 96.7% sodium 3-carboxy-benzenesulfonate (SBA) (17.5 mol), 3398 g of a solution of hexamethylene diamine (HMD) in 32.48% by weight solution in water (9.5 mol) and 83 kg of demineralized water and 6.4 g of Silcolapse 5020® antifoaming agent. The molar content of sulfonate compound equals 17.5/(332.5+17.5+9.5)=4.9 mol.-%. The polyamide 66 containing 4.8 mol.-% of SBA is produced by a standard polymerization method of the polyamide 66 type, with 40 minutes of finishing under a vacuum of 70 mbar. The polymer obtained is cast in rod form, cooled and made into granule form by chopping the rods.

(13) The polymer obtained displays the following characteristics: GTC=51.1 meq/kg, GTA=44.1 meq/kg, GTS=219 meq/kg, Mn=2.10.sup.6/(GTA+GTC+GTS)=6,370 g/mol. There are on average 1.4 sulfonate ends per chain.

(14) The polyamide obtained is semi-crystalline and has the following thermal characteristics: Tg=86.5° C., Tc=228.2° C., Tf=259.5° C., ΔHf=71.2 J/g, χc=37.9%. The sulfonate-terminated polyamide, in spite of a lower molar mass, has a Tg considerably higher by about 16° C. compared to that of PA 66 and a comparable degree of crystallinity.

Example 4

Preparation of a Polyamide 66 Containing about 10 mol.-% of SBA

(15) Into a polymerization reactor are introduced 132.77 g (0.506 mol) of N salt (1:1 salt of hexamethylene diamine and adipic acid), 12.73 g of 99% sodium 3-carboxybenzenesulfonate (SBA) (0.056 mol), 12.20 g of a solution of hexamethylene diamine (HMD) in 32.25% by weight solution in water (0.034 mol) and 127 g of demineralized water and 2 g of antifoaming agent. The molar content of sulfonate compound equals 0.056/(0.506+0.056+0.034)=9.4 mol.-%. The polyamide 66 containing 9.3 mol.-% of SBA is produced by a standard polymerization method of the polyamide 66 type, with 30 minutes of finishing under a vacuum of about 10 mbar. The polymer obtained is cast on a tray.

(16) The polymer obtained displays the following characteristics: GTC=108.7 meq/kg, GTA=98.3 meq/kg, GTS=435 meq/kg, Mn=3120 g/mol. There are on average 1.36 sulfonate ends per chain.

(17) The polyamide obtained is semi-crystalline and has the following thermal characteristics: Tg=97.8° C., Tc=213.7° C., Tf=251.8° C., ΔHf=63 J/g. The sulfonate-terminated polyamide, in spite of a lower molar mass, has a Tg considerably higher by about 27° C. compared to that of PA 66, and a degree of crystallinity of 33.5%.

Example 5

Preparation of a Polyamide 66 Containing about 18 mol.-% of SBA

(18) Into a polymerization reactor are introduced 116.64 g (0.445 mol) of N salt (1:1 salt of hexamethylene diamine and adipic acid), 25.17 g of 99% sodium 3-carboxybenzene-sulfonate or (SBA) (0.111 mol), 20.81 g of a solution of hexamethylene diamine (HMD) in 32.25% by weight solution in water (0.058 mol) and 120.6 g of demineralized water and 2 g of antifoaming agent. The molar content of sulfonate compound equals 0.111/(0.445+0.111+0.058)=18.1 mol.-%. The sulfonate-terminated polyamide is produced by a standard polymerization method of the polyamide 66 type, with 30 minutes of finishing under a vacuum of about 30 mbar. The polymer obtained is cast on a tray.

(19) The polymer obtained displays the following characteristics: GTC=232.4 meq/kg, GTA=203.5 meq/kg, GTS=855 meq/kg, Mn=1550 g/mol. There is on average 1.32 sulfonate ends per chain.

(20) The sulfonate-terminated polyamide is semi-crystalline and has the following thermal characteristics: Tg=105.7° C., Tc=183.2° C., Tf=239.6° C., ΔHf=45 J/g. The sulfonate-terminated polyamide, in spite of a lower molar mass, has a Tg considerably higher by about 35° C. compared to that of PA 66.

Example 6

Preparation of a Polyamide 66 Sulfonate PA 66/6AISLi 95/5

(21) Into a polymerization reactor are introduced 85.9 kg (344.8 mol) of N salt (1:1 salt of hexamethylene diamine and adipic acid), 4657 g of 93.33% lithium salt of 5-sulfoisophthalic acid (AISLi) (17.24 mol), 6435 g of a solution of hexamethylene diamine (HMD) in 32.47% by weight solution in water (17.98 mol) and 81.2 kg of demineralized water and 6.4 g of Silcolapse 5020® antifoaming agent. The polyamide 66 sulfonate is produced by a standard polymerization method of the polyamide 66 type, with 30 minutes of finishing at atmospheric pressure. The polymer obtained is cast in rod form, cooled and made into granule form by chopping the rods.

(22) The polymer obtained displays the following characteristics: GTC=102.6 meq/kg, GTA=94.3 meq/kg, Mn=10160 g/mol.

(23) The polyamide 66 sulfonate PA 66/6AISLi 95/5 is semi-crystalline and has the following thermal characteristics: Tg=92.5° C., Tc=215.4° C., Tf=254.5° C., ΔHf=56.7 J/g thus χc=30.2%. The polyamide sulfonate, in spite of a lower molar mass, has a Tg considerably higher by about 22° C. compared to that of PA 66 while decreasing the degree of crystallinity by only 17%.

(24) Comparison of the experiment with comparative example 2 shows that the sulfonate borne by the aromatic ring is responsible for the large increase in the Tg.

Example 7

Preparation of a Polyamide 66 Sulfonate PA 66/6AISLi 90/10

(25) Into a polymerization reactor are introduced 128.98 g (0.492 mol) of N salt (1:1 salt of hexamethylene diamine and adipic acid), 14.77 g of 93.33% lithium salt of 5-sulfoisophthalic acid (AISLi) (0.0547 mol), 21.2 g of a solution of hexamethylene diamine (HMD) in 32.5% by weight solution in water (0.0593 mol) and 122.73 g of demineralized water and 2 g of an aqueous solution of antifoaming agent. The polyamide sulfonate 66/6AISLi 90/10 is produced by a standard polymerization method of the polyamide 66 type, with 45 minutes of finishing at atmospheric pressure. The polymer obtained is cast in rod form, cooled and made into granule form by chopping the rods.

(26) The polymer obtained displays the following characteristics: GTC=138.7 meq/kg, GTA=114.6 meq/kg, Mn=7900 g/mol.

(27) The polyamide sulfonate 66/6AISLi 90/10 is semi-crystalline and has the following thermal characteristics: Tg=99.5° C., Tc=175.4° C., Tf=242.3° C., ΔHf=41 J/g thus χc=21.8%. The polyamide sulfonate, in spite of a lower molar mass, has a Tg considerably higher by about 29° C. compared to that of PA 66 for a decrease in the degree of crystallinity of the PA 66 by 40%.

(28) Comparison of the experiment with comparative example 2 shows that for a similar reduction in the degree of crystallinity (obtained by taking two times less AISLi than isophthalic acid), the PA sulfonate displays a Tg increased by 29° C. against only 7° C. for the PA 66/6I.

Example 8

Preparation of PA 66/Glass Fiber 70/30 and PA 66 Containing 5 mol.-% of SBA/Glass Fibers 70/30 by Weight Formulations

(29) Formulations of polyamide/Vetrotex FV983 glass fibers in a 70/30 ratio by weight are produced in a Leistritz LSM30/34 twin screw extruder (diameter 34 mm, L/D ratio=35) at a screw speed of 250 rpm and with a flow rate of 10 kg/hr (7 kg/hr feed for the polyamide and 3 kg/hr for the glass fiber).

(30) A PA 66/glass fibers 70/30 formulation is produced with extruder heating temperatures lying between 250 and 285° C. A PA 66 5 mol.-% of SBA/glass fibers 70/30 formulation is produced with extruder heating temperatures lying between 220 and 265° C. The rods leaving the extruder are poured into a water cooling tank and then granulated. The granules are then dried under vacuum in a study at 90° C. for 14 hours.

Example 9

Dynamic Thermomechanical Analysis Against Temperature

(31) The batches of formulations produced in example 8 are injected in the form of test pieces of dimensions 80 mm×10 mm×4 mm on an Arburg Allrounder® 350 90, 220 D injection press. The temperature of the mold is regulated at 80° C. For the PA 66/glass fibers 70/30 by weight compound, the temperature of the injection nozzle is 290° C. For the PA 66 5 mol.-% SBA/glass fibers 70/30 compound, the temperature of the injection nozzle is 270° C.

(32) These test pieces are then cut up before being used to compare the thermomechanical properties of the formulations. A TA Instruments RSA3 instrument making it possible to carry out 3 point flexures on the test pieces is used: a sinusoidal stress (frequency 1 Hz and amplitude 0.05%) is applied to the sample and the values of the elastic modulus E′ and loss modulus E″ are recovered. The measurements are performed following a temperature gradient from −40° C. to 250° C. at a temperature increase speed of 2° C./min.

(33) The results are expressed in the following table 1:

(34) TABLE-US-00001 TABLE 1 E′ 80° C. ΔE′ Compound Tα (° C.) (GPa) 80° C. PA 66/glass fiber 70/30 by weight 74 3.08 — PA 66 5 mol.-% SBA/glass fiber 70/30 by 88 3.79 +23% weight

(35) It is observed that the modulus E′ of the formulation based on PA containing sulfonate units exhibits a higher modulus at 80° C. than that of the formulation based on PA 66.