Sulfonate-modified polyamide having improved barrier properties

Abstract

The use of a polyamide modified by sulfonate functions which has improved barrier properties is described. Further described is the use of a sulfonate, aliphatic or aromatic compound for manufacturing a modified polyamide having improved fluid-barrier properties. The composition as described includes a modified polyamide, which is optionally a composition in the form of granules or powder used in manufacturing articles by an injection or extrusion blow-molding method.

Claims

1. A method of improving fluid barrier properties of a fluid container, the method comprising reducing the fluid permeability of the fluid container by fabricating the fluid container from a polyamide composition comprising: a (co)polyamide comprising at least one aliphatic monomer and optionally at least one aromatic monomer in a polymer chain, and at least one novolac resin, wherein the reduced fluid permeability reduces permeability of a gasoline comprising 10 volume percent ethanol, 45% iso-octane, and 45% toluene, wherein the fluid container is a tube, pipe, or tank intended to contain or transport a fluid, wherein said (co)polyamide is modified by a sulfonate compound, in an amount of from 5 to 10 mol percent sulfonate unit relative to the total number of moles of units constituting the polymer chain, wherein the resulting fluid container has reduced fluid permeability to the gasoline when compared with a corresponding fluid container made with a (co)polyamide which is not modified with the sulfonate compound, wherein the (co)polyamide is a semi-crystalline (co)polyamide, wherein the modified (co)polyamide is in a composition comprising 30% to 95% by weight of said (co)polyamide, relative to the total weight of the composition, and wherein the modified (co)polyamide comprises a polyamide selected from the group consisting of a polyamide 6, a polyamide 66, a polyamide 10, a polyamide 11, a polyamide 610, a polyamide 1010, a polyamide 12, a polyamide 6I, a copolyamide 66/6T, a copolyamide 66/6I, a copolyamide 6T/MT, and a copolyamide 6T/6I.

2. The method as described in claim 1, wherein the sulfonate compound comprises as least one SO.sub.3X function, wherein SO.sub.3X represents SO.sub.3H or SO.sub.3M; M being a substituent that replaces the SO.sub.3H proton H.sup.+ to form an inactive salified group.

3. The method as described in claim 1, wherein the sulfonate compound is an aromatic sulfonate compound.

4. The method as described in claim 1, wherein the sulfonate compound is bound chemically to a polyamide chain to form a covalent bond through a function of said sulfonate compound that can react with the amine or carboxylic functions in the polyamide monomers, wherein the function of the sulfonate compound is selected from the group consisting of an amine, a carboxylic acid, an aldehyde, an anhydride, a hydroxyl, a ketone function and their derivatives.

5. The method as described in claim 1, wherein the sulfonate compound is placed in a polymer chain of the (co)polyamide or at the end of the polyamide chain.

6. The method as described in claim 1, wherein the sulfonate compound is represented by the general formula (I):
(Z).sub.nY(SO.sub.3X).sub.m (I) in which: SO.sub.3X represents SO.sub.3H or SO.sub.3M, M being a substituent that replaces the SO.sub.3H proton H.sup.+ to form an inactive salified group; m is from 1 to 10; Y is a hydrogen substituent comprising from 2 to 100 carbon atoms, linear or cyclic, aromatic or aliphatic and that can comprise heteroatoms; Z is a function that can react with amine or carboxylic acid functions in the polyamide monomers; and n is from 1 to 10.

7. The method as described in claim 1, wherein the sulfonate compound is selected from the group consisting of: a sodium 5-sulfoisophthalic acid, a lithium 5-sulfoisophthalic acid, a sodium-4-carboxybenzene sulfonate, a sodium-3-carboxybenzene sulfonate, a sodium-2-carboxybenzene sulfonate, a lithium-3-carboxybenzene sulfonate, a potassium-3-carboxybenzene sulfonate, a sodium-3-carbomethoxybenzene sulfonate, a potassium-2-carbopropoxybenezene sulfonate, a sodium-2-carbomethoxyethylbenzene sulfonate, a potassium-3-aminomethylbenzene sulfonate, a sodium-2-aminoethylbenzene sulfonate and a potassium-3-aminopropylbenzene sulfonate.

8. The method as described in claim 1, wherein the modified (co)polyamide is in a composition comprising 40% to 80% by weight of said (co)polyamide, relative to the total weight of the composition.

9. The method as described in claim 1, wherein the modified (co)polyamide is comprised of a composition comprising an agent modifying impact strength.

10. The method as described in claim 1, wherein the modified (co)polyamide is comprised of a deposited composition or is associated with another substrate.

11. The method as described in claim 1, wherein the fluid container having reduced fluid permeability is a multilayer article.

12. A method of improving gasoline barrier properties of a gasoline container, the method comprising reducing the gasoline permeability of the gasoline container by fabricating the gasoline container from a (co)polyamide comprising at least one aliphatic monomer and optionally at least one aromatic monomer in a polymer chain, and at least one novolac resin, wherein the reduced gasoline permeability reduces permeability of a gasoline comprising 10 volume percent ethanol, 45% iso-octane, and 45% toluene, wherein the gasoline container is a tube, pipe, or tank intended to contain or transport a gasoline intended to contain or transport a fluid, wherein the (co)polyamide is modified by a sulfonate compound, in an amount of from 5 to 10 mol percent sulfonate unit relative to the total number of moles of units constituting the polymer chain, wherein the (co)polyamide is semi-crystalline (co)polyamide, wherein the modified (co)polyamide is in a composition comprising 30% to 95% by weight of said (co)polyamide, relative to the total weight of the composition, wherein the modified (co)polyamide comprises a polyamide selected form the group consisting of a polyamide 6, a polyamide 66, a polyamide 10, a polyamide 11, a polyamide 610, a polyamide 1010, a polyamide 12, a polyamide 6I, a copolyamide 66/6T, a copolyamide 66/6I, a copolyamide 6T/MT, and a copolyamide 6T/6I, and wherein the resulting gasoline container has reduced gasoline permeability to wherein the gasoline when compared with a corresponding gasoline container made with a (co)polyamide which is not modified with the sulfonate compound.

13. A method of fabricating a gasoline container with improved gasoline barrier properties, the method comprising: modifying a (co)polyamide with a sulfonate compound; wherein the modified (co)polyamide is in a composition comprising 30% to 95% by weight of said (co)polyamide, relative to the total weight of the composition; wherein the modified (co)polyamide comprises a polyamide selected form the group consisting of a polyamide 6, a polyamide 66, a polyamide 10, a polyamide 11, a polyamide 610, a polyamide 1010, a polyamide 12, a polyamide 6I, a copolyamide 66/6T, a copolyamide 66/6I, a copolyamide 6T/MT, and a copolyamide 6T/6I, and molding the modified (co)polyamide into an article selected from the group consisting of a tube, a pipe, and a tank intended to contain or transport a fluid; wherein the container comprises at least one novolac resin; wherein the (co)polyamide is a semi-crystalline (co)polyamide; wherein the (co)polyamide comprises at least one aliphatic monomer and optionally at least one aromatic monomer in a polymer chain; wherein said (co) polyamide is modified by the sulfonate compound in an amount of from 5 to 10 mol percent sulfonate unit relative to the total number of moles of units constituting the polymer chain; wherein the improved gasoline barrier properties reduces permeability of a gasoline comprising 10 volume percent ethanol, 45% iso-octane, and 45% toluene; and wherein the resulting container has reduced fluid permeability to the gasoline when compared with a corresponding container made with a (co)polyamide which is not modified with the sulfonate compound.

Description

EXPERIMENTAL SECTION

(1) Characterizations

(2) Physicochemical Property Analysis

(3) Terminal acid group (TCG) and terminal amine group (TAG) content: assayed by potentiometry, expressed in meq/kg.

(4) When the sulfonate compound is a monofunctional monosulfonate, we can calculate the terminal sulfonate group content (TSG) from the quantities of reagents added to the polymerization reactor.

(5) Number-average molecular weight Mn determined by the formula Mn=2.106/(TAG+TCG+TSG) and expressed in g/mol.

(6) When the sulfonate compound is a monofunctional monosulfonate, we can calculate the number of sulfonate chain ends per chain as follows: Nsulfonate/chain=TSG/((TAG+TCG+TSG)/2).

(7) Heat Property Analysis

(8) For granules prepared by synthesis: the melting point (Tf) and associated enthalpies (Hf), and crystallization temperatures (Tc) are determined by Differential Scanning Calorimetry (DSC), using a Perkin Elmer Pyris 1 device, at a rate of 10 C./min. The crystallinity level is obtained by calculating c=Hf/Hf, where Hf is the enthalpy of fusion of a pure polyamide crystal (Hf(PA66)=188 J/g). Glass transition temperature (Tg) determined on the same device at a rate of 40 C./min. The values are given for dry products.

(9) For transformed objects (films, injected plates): the melting points (Tf), crystallization temperatures (Tc) and glass transition temperatures (Tg) of films obtained are determined by Differential Scanning Calorimetry (DSC), using a TA Instruments Q2000 device, at a rate of 10 C./min. The crystallinity level is obtained by calculating Xc=Hf/Hf, where Hf is the enthalpy of fusion of the polyamide sample tested and Hf is the enthalpy of fusion of a pure polyamide crystal (Hf(PA66)=188 J/g). The values are given for dry products.

(10) Permeability to Gasoline Analysis:

(11) Extruded films, injected or blow-molded parts are either dried at 110 C. under vacuum overnight or packaged at 23 C. at relative humidity of 50% (RH50) until their water uptake reaches equilibrium. Permeability to gasoline (for example gasoline E10 containing 10% by volume ethanol, 45% iso-octane and 45% toluene) is then evaluated: one of the faces of the film is placed in contact with the gasoline using aluminum permeation cups sealed tightly, and the mass of the ensemble (cup+film+gasoline) is measured over time. After a certain time called the induction time, a mass loss corresponding to gasoline permeation through the polymer film is measured, and a permeability value representing this mass loss related to time, at the film surface and multiplied by the film thickness can be established (Permeability P expressed in g.mm/m.sup.2.J).

(12) The permeability of films to gasoline is measurement at 28 C. and/or at 40 C. by placing the permeation cups in ventilated heat-controlled ovens at 28 C. or 40 C. The ventilated ovens are located in a room regulated at 23 C. at RH50, so the humidities in the oven are 40% and 20% at 28 C. and 40 C. respectively.

COMPARISON EXAMPLE 1

Synthesis of an Unmodified Pa 66

(13) To a polymerization reactor are added 92.6 kg (353 mol) of salt N (1:1 hexamethylene diamine and adipic acid salt), 84 kg of deionized water and 6.4 g antifoam agent Silcolapse 5020. The polyamide 66 is made according to a standard polyamide 66 polymerization process, with 30 minutes finishing. The polymer obtained is poured into rods, cooled, and shaped into granules by cutting the rods.

(14) The polymer obtained presents the following characteristics: TCG=70.2 meq/kg, TAG=51.5 meq/kg, Mn=16,430 g/mol.

(15) The polyamide 66 is semi-crystalline and has the following heat characteristics: Tg=70.6 C., Tc=230.9 C., Tf=263.7 C., Hf =68.4 J/g, i.e. c=36.4%.

EXAMPLE 1

Synthesis of a Polyamide 66 Sulfonate PA 66/6AlSLi 95/5

(16) To a polymerization reactor are added 85.9 kg (327.5 mol) of salt N (1:1 salt of hexamethylene diamine and adipic acid), 4,657 g of lithium 5-sulfoisophthalic acid salt at 93.33% (AlSLi) (17.24 mol), 6,435 g of a solution of hexamethylene diamine (HMD) in solution in water at 32.47% by weight (17.98 mol) and 81.2 kg of deionized water and 6.4 g of Silcolapse 5020 antifoaming agent. The polyamide 66 sulfonate is made according to a standard polyamide 66 polymerization process, with 30 minutes finishing at atmospheric pressure. The polymer obtained is poured into rods, cooled, and shaped into granules by cutting the rods.

(17) The polymer obtained presents the following characteristics: TCG=102.6 meq/kg, TAG=94.3 meq/kg, Mn=10,160 g/mol.

(18) The polyamide 66 sulfonate PA 66/6AlSLi 95/5 is semi-crystalline and has the following thermal characteristics: Tg=92.5 C., Tc=215.4 C., Tf=254.5 C., Hf =56.7 J/g i.e. c=30.2%. The sulfonate polyamide, in spite of a lower molar mass, has a much higher Tg, about 22 C. higher than that of PA 66 while reducing the crystallinity level by only 17%.

EXAMPLE 2

Synthesis of a Polyamide 66 Sulfonate PA 66/6AlSLi 90/10

(19) To a polymerization reactor are added 128.98 g (0.492 mol) of salt N (1:1 salt of hexamethylene diamine and adipic acid), 14.77 g of lithium 5-sulfoisophthalic acid salt at 93.33% (AlSLi) (0.0547 mol), 21.2 g of a solution of hexamethylene diamine (HMD) in solution in water at 32.5% by weight (0.0593 mol) and 122.73 g of deionized water and 2 g of an aqueous solution of antifoaming agent. The polyamide 66/6AlSLi 90/10 sulfonate is made according to a standard polyamide 66 polymerization process, with 45 minutes finishing at atmospheric pressure. The polymer obtained is poured into rods, cooled, and shaped into granules by cutting the rods.

(20) The polymer obtained presents the following characteristics: TCG=138.7 meq/kg, TAG=114.6 meq/kg, Mn=7,900 g/mol.

(21) The polyamide 66/6AlSLi 90/10 sulfonate is semi-crystalline and has the following thermal characteristics: Tg=99.5 C., Tc=175.4 C., Tf=242.3 C., Hf =41 J/g i.e. c=21.8%. The polyamide sulfonate, in spite of a lower molar mass, has a much higher Tg, about 29 C. higher relative to that of PA 66, to reduce the crystallinity level of PA 66 by 40%.

EXAMPLE 3

Preparation of Films of PA 66 and Functionalized PA 66 Sulfonate PA 66/6AlSLi 95/5 and Measuring E10 Gasoline Permeability

(22) The granules of PA 66 from comparison example 1 or PA 66/6AlSLi 95/5 from example 1 are added in a twin-screw co-rotating Leistritz extruder (D=34, L/D=35), with screw rate 255 rpm and temperature 280 C. An OCS wrapping machine with a flat sheet die (width 300, gap 500 m) delivers films 300-m thick, the film coming out of the die being stretched at a rate of 2 m/minute, the cooling roll temperature being 135 C.

(23) The films obtained have the following thermal characteristics:

(24) PA 66: Tg=56 C., Tf=260 C., Tc=231 C., c=37%

(25) PA 66/6AlSLi 95/5: Tg=78 C., Tf=251 C., Tc=221 C., c=34%,

(26) Before evaluating permeability, the films are adjusted to RH50 at 23 C. until their water uptake reaches equilibrium (water uptake 3.2% for PA6.6 and 3.8% for PA66/6AiSLi 95/5). At 28 C., the permeability of PA 66 to E10 gasoline is 1.56 g.mm/m.sup.2.J, while the permeability of PA66/6AlSLi 95/5 is 0.55 g.mm/m.sup.2.J (i.e. a reduction in permeability of 65%). At 40 C., the permeability of PA 66 to E10 gasoline is 1.92 g.mm/m.sup.2.J, while the permeability of PA66/6AlSLi 95/5 is 0.83 g.mm/m.sup.2.J (i.e. a reduction in permeability of 57%).

(27) Accordingly, the PA 66/6AlSLi 95/5, in spite of a lower crystallinity level than PA 66, has E10 gasoline permeability about 2.5 times lower than PA 66. At 40 C., the permeability of PA 66 to E100 gasoline (pure ethanol) is 5.44 g.mm/m.sup.2.J, while the permeability of PA66/6AlSLi 95/5 is 1.35 g.mm/m.sup.2.J (i.e. a reduction in permeability of 75%).

EXAMPLE 4

Formulations, Plate Injections, and Measuring Permeability to E10 Gasoline

(28) Before extrusion, the polyamides are dried at a water content below 1000 ppm. Formulations are made by mixing various molten components and additives in a twin-screw co-rotating WERNER & PLEIFEDER ZSK 40 extruder operating at 40 kg/h and at a rate of 270 rpm. The temperature settings in the 8 zones are respectively: 245, 255, 255, 255, 255, 260, 260, 270 C. All the components in the formulation are added at the start of the extruder.

(29) The additives used are as follows:

(30) ExxonMobil Chemical Elastomer called EXXELOR VA1801 Novolak S phenolic resin by Plastics Production Plant ZTS ERG in Pustkw S. A.

(31) The formulations comprise 4% of a mixture of colorant, stabilizer, and lubricant.

(32) To analyze permeability, plates 1001000.8 mm.sup.3 are injected on a DEMAG 80 T machine with screw diameter 25 mm (Tbarrel=270 C., Tmold=85 C., cycle time 24.6 s). Before evaluating permeability, the plates are dried at 110 C. under vacuum overnight.

(33) 4-mm-thick test pieces called multifunctions are injected to characterize the tensile and impact mechanical properties. The test pieces are tested quickly after injection and considered to be dry (Dry as molded).

(34) The formulations and properties are collected in the following table 1:

(35) TABLE-US-00001 CF1 CF2 F1 F2 F3 Rhodia 31A00 (IV = 170 mL/g) 71% 66% 33% type PA 66 PA 66/6AISLi 95/5 (ex. 1) 71% 66% 33% Exxelor VA1801 Elastomer 25% 25% 25% 25% 25% Novolac phenolic resin 5% 5% 5% E10 permeability at 40 C. 3.0 1.47 0.45 0* 0.51 (g .Math. mm/m.sup.2 .Math. J) Tensile stress at the break point 44 +/ 1.0 43 +/ 0.3 45 +/ 0.3 44 +/ 0.4 43 +/ 0.5 at 23 C. (MPa) - ISO 527/1A Tensile modulus 1560 +/ 130 1643 +/ 60 1552 +/ 63 1634 +/ 114 1568 +/ 44 at 23 C. (MPa) - ISO 527/1A Charpy notch impact 106.7 +/ 3 96 +/ 1.9 87 +/ 1.6 95 +/ 1.9 at 23 C. - ISO 179-1/1eA Charpy notch impact 29.2 +/ 2.5 26 +/ 1.5 24 +/ 2.8 23 +/ 2.6 25 +/ 2.3 at 40 C. - ISO 179-1/1eA The % are expressed as weight, relative to the total weight of the composition. 0*: no permeation after 50 days.