GB1558800A

GB1558800A - Polyaminde terpolymers

Info

Publication number: GB1558800A
Application number: GB4707076A
Authority: GB
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1975-11-13
Filing date: 1976-11-11
Publication date: 1980-01-09
Also published as: FR2331583A1; NL7612628A; FR2331583B1; CA1067647A; NL171278C; NL171278B; JPS551299B2; IT1063996B; JPS5262399A; DE2651741A1

Description

(54) POLYAMIDE TERPOLYMER (71) We, E. I. DU PONT DE NEMOURS & COMPANY a Corporation organised and existing under the laws of the State of Delaware, United States of America, of Wilmington, Delaware, 19898, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to terpolyamides and to a process for their preparation.

Many classes of polyamide resins, commonly referred to as nylon, are known.

One class of such polyamides is ordinarily obtained by a polycondensation reaction between a polybasic acid and a polyamine. For instance, the polycondensation reaction between adipic acid and hexamethylene diamine yields polyhexamethylene adipamide which is commonly referred to as nylon 66. Such polyamide resins in the form of shaped objects have been found to be useful in numerous applications, e.g. flexible tubing. A principal disadvantage and drawback of the polyamide resins is the lack of resistance to degradation occasioned by contact with zinc chloride. Specifically, exposure to zinc chloride will result in deterioration and degradation of shaped articles moulded from polyamide resins as evidenced by extensive cracks that appear and form throughout such shaped articles. It has been observed that resistance to zinc chloride appears to be related to the number of carbon atoms of the amide group in the polymer chain. That is, the resistance to zinc chloride increases as the number of carbon atoms between each pair of repeating amide groups of the polymer chain increases. To illustrate, nylon 6 and nylon 66 are more sensitive to zinc chloride than nylon 612 which is, in turn, more sensitive than nylon 11 and nylon 12. Attempts have been made to increase the zinc chloride resistance of polyamide resins. For example, British Patent Specification No. 1,367,840 describes a polyamide copolymer having increased zinc chloride resistance that is obtained by copolymerizing from 0.5 to 15% by weight of a dimerized salt of the formula HOOC-R-COOH H2N-R'-NH2 wherein R and R' are saturated hydrocarbon radicals having from 25 to 50 carbon atoms and a polyamide-forming monomer. Long carbon-chain salts such as the foregoing and long carbon-chain dicarboxylic acids and lactams used heretofore to provide zinc chloride-resistance polyamides are, however, quite expensive.

l he present invention provides specific polyamide resins that are zinc-chloride resistant and more economical. The polyamide resins of the present invention are terpolyamide resins having distributed therein the following repeating segments

wherein x is 8 or 10:

wherein R is an aliphatic hydrocarbon radical having 7, 8, 10 or 34 carbon atoms, the resin having an inherent viscosity of at least 1.0 and segments (1), (2) and (3) being present in amounts of (1) from 35% to 80% by weight, (2) between 15% and 25 fí by weight and (3) between 3% and 40% by weight, the amounts each being based upon the resin weight, with the proviso that segments (1) and (3) may not be identical.

The present invention also provides a process for the preparation of such terpolyamide resins, which process comprises polycondensing aqueous salt solutions of precursors of the polymer segments, evaporating the water from the reaction mixture and allowing the polycondensation reaction to continue to completion, the aqueous salt solutions containing sufficient amounts of the precursors of segments (1), (2) and (3) to provide the terpolyamide.

Segment (1) in the present terpolymers is commonly referred to as nylon 610 or 612 obtained by polycondensing hexamethylene diamine and sebacic acid, or dodecanedioic acid. Segment (2) is commonly referred to an nylon 61 or 6T and is obtained by polycondensing hexamethylene diamine with isophthalic acld, terephthalic acid or both. Segment (3) is commonly referred to as either nylon 69, nylon 610, nylon 612 or nylon 636 (depending upon the number of in-chain carbon atoms of each of the diamine moiety and the dicarboxylic acid moiety of the polymer segment) and can be obtained by polycondensing hexamethylene diamine and one or more of azelaic acid, sebacic acid, dodecanedioic acid and dimer acid.

Segment (1) of the terpolyamide constitutes from 35 /O to 80% by weight of the terpolyamide resin. In a preferred embodiment segment (1) constitutes between 75 and 80% by weight of the terpolyamide resin. Segment (2) constitutes between 150, and 25"/, by weight of the terpolyamide resin. Segment (3) constitutes between 3 /, and 40% by weight of the terpolyamide resin. Preferably, segment (3) constitutes between 3% and 10%, more preferably between 5% and 10% of the terpolyamide.

The terpolyamide resin of the present invention is obtained by polycondensing aqueous salt solutions of precursors of the above described polymer segments at a temperature usually below 300"C., e.g. 1950C to 2800C., and a pressure usually below 300 psig, e.g. 180 psig to 250 psig, for a suitable time usually less than two hours. When most of the water is evaporated, the pressure is gradually bled to atmospheric and the polycondensation reaction is allowed to continue to completion either under atmospheric conditions or under vacuum. The choice of conditions will depend on the desired molecular weight of the resin. For instance once the appropriate aqueous salt solutions of the precursors of segments (1), (2) and (3) have been introduced in an autoclave, the contents of the autoclave are heated to a temperature of 195"C and a pressure of 180 psig. The water is slowly bled off while maintaining the pressure at 180 psig until the nylon salts are concentrated and the temperature has reached 250"C. The pressure is then slowly reduced to atmospheric and the temperature is allowed to increase to 2800 C. The terpolyamide resin is held at atmospheric pressure until the desired molecular weight is attained.

By way of further illustration, a terpolyamide of 80 weight percent nylon 612 segments, 15 weight percent nylon 61 segments, and 5 weight percent nylon 69 segments can be prepared by introducing an aqueous solution containing 53.6 parts by weight of nylon 612 salt, an aqueous solution containing 10.3 parts by weight of nylon 61 salt and an aqueous solution containing 3.4 parts by weight of nylon 69 salt into an autoclave followed by heating the contents of the autoclave to 2000C and a pressure of 180 psig. The water is slowly bled off while maintaining the pressure at 180 psig until the salts are concentrated and the temperature has reached 246"C.

The pressure is then slowly reduced to atmospheric and 13.1 parts by weight of "Santicizer" 8 is then added ("Santicizer" is a Registered Trade Mark). The temperature of the polymer is then allowed to rise to 2700C and vacuum is applied on the polymer until the desired molecular weight is attained.

The salts of nylon 69, 610, 612, 61, 6T, or 636 can be obtained by known methods. For example, nylon 612 salt can be prepared by mixing 13.4 parts by weight of hexamethylene diamine with 60 parts by weight of water after which 26.6 parts by weight of dodecanedioic acid is added. The mixture is agitated and heated to about 70"C to maintain the nylon 612 salt in solution. The pH of the salt solution is measured and adjusted to between 7.3 and 8.6 by adding either dodecanedioic acid or hexamethylene diamine. The actual pH used will depend on the amount of hexamethylene diamine that is lost during the polymerization. The concentration of the nylon 612 salt in the resulting solution can be calculated from the amount of dodecanedioic acid used in the preparation. Normally, the concentration of the nylon 612 salt is about 40% by weight.

Salts of nylon 69, 610,61 and 6T are prepared similarly as the salt of nylon 612.

Because of the lower solubility of nylon 61 and 6T salts, a 30 weight percent salt concentration is used in the preparation of these nylon salts. For instance, a 30 weight percent nylon 6T salt is prepared by mixing 70 parts by weight of water, 12.3 parts by weight of hexamethylene diamine and 17.7 parts by weight of terephthalic acid. The mixture is agitated and heated to about 70"C. The pH of the nylon salt solution is then measured and adjusted to between 7.3 and 8.6 by adding either hexamethylene diamine or terephthalic acid. The actual concentration of the nylon salt solution can be calculated from the amount of terephthalic acid used in the preparation. The nylon 61 salt is prepared by using isophthalic acid in lieu of the terephthalic acid.

For convenience, it may be desired to prepare all the nylon salts simultaneously, and this can be accomplished by reacting hexamethylene diamine with a mixture of the acids in the proper proportions. This method is more desirable when one of the nylon salt components is nylon 636 salt. The nylon 636 salt has a much greater tendency to form foam and lower solubility in water than nylon 6T or 61 salt. An alternate method for the preparation of nylon 636 salt is to use methanol as a solvent. This method is described in British Patent 1,367,840.

The preparation of the terpolyamide resin of the invention can be conducted in the presence of a catalyst system comprising compounds of phosphorus such as orthophosphoric acid.

The preparation of the terpolyamide resin of the invention is preferably conducted in the presence of monofunctional acids to control the molecular weight. For instance, up to 0.2 weight percent of acetic acid, preferably below 0.06 weight percent, may be used.

The preparation of the terpolyamide resin of the invention is preferably conducted in an aqueous solvent system.

The preparation of the terpolyamide resin of the invention can proceed within a broad temperature range. For example, the preparation can be conducted as low as 2000C to as high as about 300"C. The specific reaction temperature employed initially and the course of the reaction temperature will depend to some extent upon the melting point of the terpolyamide resin and the selection of process conditions such as the particular nylon salts that are employed, or the molecular weight of the terpolyamide, as will readily be understood bg anyone skilled in the art.

The preparation of the terpolyamide resin of the invention can be carried out at any convenient pressure. Preferably, the preparation is carried out at a pressure between 180 psig and 250 psig.

The molecular weight of the terpolyamide resin of the invention is sutilciently high that it can be molded into shaped articles. The terpolyamide resin can be cut into small pellets that are suitable for molding.

The inherent viscosity of the terpolyamide resin is at least 1.0, when measured in a solution of the terpolyamide resin in m-cresol at 250 C. Inherent viscosity data is obtained by measuring the viscosity of the terpolyamide solution relative to that of the solvent alone, and inherent viscosity is calculated from the following equation Viscosity of Terpolyamide Solution Natural ( ) Inherent ~ Logarithm Viscosity of Solvent Viscosity - C wherein C is the concentration expressed in grams of terpolyamide resin per 100 milliliters of solution. The terpolyamide solution is obtained by dissolving 0.5 gram of the terpolyamide in an initial amount of solvent less than 100 mls at 500C, and then adjusting the total solution to 100 mls by adding additional solvent at 25"C. As is known in the polymer art, inherent viscosity is directly related to the molecular weight of polymers.

The terpolyamide resin molding pellets can be surface coated with suitable lubricants in order to facilitate the molding thereof. For instance, 0.09% by weight, based upon the terpolyamide resin weight, of aluminum distearate can be coated onto the terpolyamide resin molding pellets. Suitable additives such as heat stabilizers, e.g. potassium iodide and cuprous iodide, can be added to the terpolyamide resin. As an example, 0.35 weight percent of potassium iodide and 0.05 weight percent cuprous iodide, based upon the weight of the terpolyamide resin may be used. When required by end-use applications. ultravoilet light absorbers can be added. Typically, about 0.2 weight percent, based on the terpolyamide resin, of benzotriazole derivatives such as 2(2'hydroxy-5'methylphenyl)benzotriazole can be used. Commercially available antioxidants which are derivatives of phenols and aromatic amines may also be used in concentrations up to 0.5 weight percent, based upon the terpolyamide resin. Dyes and pigments such as carbon black and titanium dioxide may also be present in an amount of up to 0.2 weight percent, based upon the terpolyamide resin.

Furthermore, nucleating agents such as talc may be present in concentrations up to 0.2 weight percent, based upon the terpolyamide resin.

The terpolyamide resin of the invention may also contain plasticizers. For instance, up to 18 weight percent, preferably 1t) to 1$ujo, based on the terpolyamide resin, of butylbenzene sulfonamide or N-ethyl toluene sulfonamide may be added.

The invention is illustrated by the following Examples. All parts and percentages expressed in the following Examples are by weight unless otherwise indicated.

The terpolyamide resins of the invention prepared in the following Examples were subjected to the following tests: Zinc Chloride Test Molded specimens of terpolyamide resin having a rectangular form and a length of 5 inches, a width of one-half inch and a thickness of one-eight inch were bent around the surface of a mandrel having a diameter of one inch and secured thereto. Each bent specimen was immersed in a 50% aqueous zinc chloride solution and inspected periodically to determine its resistance to zinc chloride.

EXAMPLES Example I A terpolyamide resin having an inherent viscosity of 1.45 and containing 80 weight percent of nylon 612 segments, 15 weight percent of nylon 61 segments, and 5 weight percent of nylon 69 segments was prepared as described below.

53.6 parts by weight of nylon 612 salt having a concentration of 40.0 weight percent was charged into an agitated tank. Thereafter, 72 parts by weight of water and 5.6 parts by weight of hexamethylene diamine having a concentration of 80 weight percent were added to the tank. To the mixture of nylon salt was added 2.1 parts by weight of azelaic acid and 6.1 parts by weight of isophthalic acid. The resulting mixture of nylon salts was then heated to about 700 C. The pH of the mixture of nylon salts was measured and adjusted to 8.75 by adding additional amounts of hexamethylene diamine. 6 Milliliters of DowCorningS antifoam FG-10 emulsion was then added and the mixture of nylon salts was charged into an autoclave after which is was heated to 2000C and a pressure of 180 psig in about 10 minutes. For 75 minutes the water in the form of steam was allowed to escape while maintaining pressure in the autoclave at 180 psig. When the temperature of the polymer reached 246"C., the pressure in the autoclave was then slowly reduced within 58 minutes to atmospheric pressure. 13.1 Parts by weight of "Santicizer" 8 ("Santicizer" 8 is a Registered Trademark for a mixture of N-ethyl and o- and ptoluenesulfonamide manufactured by Monsanto Co.) was added and the terpolyamide was held for 35 minutes at atmospheric pressure and the temperature was allowed to rise to 2680C. Vacuum was then applied to the terpolyamide for 24 minutes; during this step the temperature of the batch rose to 2700 C. The terpolyamide resin was then extruded through a die, quenched in cold water,and cut into small pellets. The pellets were then surface coated with 0.2 weight percent octylene glycol, followed by 0.35 weight percent potassium iodide, 0.05 weight percent cuprous iodide, and 0.05 weight percent aluminum distearate lubricant.

The octylene glycol was used to facilitate adhesion of the additives onto the pellets.

The terpolyamide resin pellets were then injection molded into rectangular test specimens having planar dimensions of 5 inches by 1/2 inch and a thickness of 1/8 inch.

Ten specimens of the terpolyamide resin moldings were tested for zinc chloride resistance as described above. All the specimens withstood 32 days immersion in 50 weight percent zinc chloride solution without exhibiting any cracks, Analysis of the polymer showed that it contained 17.5 weight percent of the "Santicizer" 8 plasticizer.

Control Example A homopolymer of nylon 612 plasticized with 17.1 weight percent "Santicizer" 8 and an inherent viscosity of 1.56 was prepared in accordance with the procedure described in Example 1. Five specimens were tested for zinc chloride resistance.

After 3 days in 50 weight percent zinc chloride solution, all the specimens exhibited cracks. This illustrates the vulnerability of plasticized nylon 612 to zinc chloride solutions.

Example 2 A terpolyamide resin haying an inherent viscosity of 1.44 and composed of 75 weight percent nylon 612 segments, 20 weight percent nylon 6T segments, and 5 weight percent of nylon 636 and plasticized with 12.9 weight percent butylbenzenesulfonamide was prepared as in Example 1. Ten specimens of this terpolyamide were tested for zinc chloride resistance. All the specimens withstood 18 days immersion in 50 weight percent zinc chloride solution.

Example 3 A terpolyamide resin having an inherent viscosity of 1.34 and composed of 75 weight percent of nylon 612 segments, 20 weight percent of nylon 61 segments, and 5 weight percent of nylon 636 segments and plasticized with 16.4 weight percent of "Santicizer" 8. (N-ethyltoluene sulfonamide) was prepared as in Example 1. Ten specimens of the terpolyamide resin were subjected to the zinc chloride test for 16 days. None of the specimens exhibited cracks after the 16 days of testing in the zinc chloride solution.

Example 4 A terpolyamide resin having an inherent viscosity of 1.48 and composed of 75 weight percent of nylon 612 segments, 20 weight percent of nylon 61 segments, and 5 weight percent of nylon 636 segments and plasticized with 1 & 5 weight percent of butylbenzenesulfonamide was prepared in accordance with The procedure described in Example 1. Ten specimens of the terpolyamide resin were subjected to the zinc chloride test for 16 days. None of the specimens exhibited cracks after the 16 days of testing in the zinc chloride solution.

WHAT WE CLAIM IS: 1. A terpolyamide resin having distributed therein the following repeating segments

wherein x is 8 or 10:

wherein R is an aliphatic hydrocarbon group of 7, 8, 10 or 34 carbon atoms the resin having an inherent viscosity of at least 1.0 and segments (1), (2) and (3) being present in amounts of (1) from 35% to 80% by weight, (2) between 15% and 25% by weight and (3) between 3% and 40% by weight, the amounts each being based upon the resin weight, with the proviso that segments (1) and (3) may not be identical.

2. A terpolymer according to Claim 1, wherein the units (3) are present in an amount of between 3 and 10% by weight.

3. A terpolymer according to Claim 2 wherein the units (3) are present in an amount of between 5 and 10% by weight.

4. A terpolymer according to Claim 1, 2 or 3, wherein the units (1) are present in an amount between 75 and 80% by weight.

5. A terpolymer according to Claim 2 substantially as described in any one of Examples 1 to 4.

6. A shaped article formed of a terpolymer as claimed in any one of the preceding claims.

7. Flexible tubing and wire and cable jackets formed of a terpolymer as claimed in any one of Claims 1 to 5.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. Analysis of the polymer showed that it contained 17.5 weight percent of the "Santicizer" 8 plasticizer. Control Example A homopolymer of nylon 612 plasticized with 17.1 weight percent "Santicizer" 8 and an inherent viscosity of 1.56 was prepared in accordance with the procedure described in Example 1. Five specimens were tested for zinc chloride resistance. After 3 days in 50 weight percent zinc chloride solution, all the specimens exhibited cracks. This illustrates the vulnerability of plasticized nylon 612 to zinc chloride solutions. Example 2 A terpolyamide resin haying an inherent viscosity of 1.44 and composed of 75 weight percent nylon 612 segments, 20 weight percent nylon 6T segments, and 5 weight percent of nylon 636 and plasticized with 12.9 weight percent butylbenzenesulfonamide was prepared as in Example 1. Ten specimens of this terpolyamide were tested for zinc chloride resistance. All the specimens withstood 18 days immersion in 50 weight percent zinc chloride solution. Example 3 A terpolyamide resin having an inherent viscosity of 1.34 and composed of 75 weight percent of nylon 612 segments, 20 weight percent of nylon 61 segments, and 5 weight percent of nylon 636 segments and plasticized with 16.4 weight percent of "Santicizer" 8. (N-ethyltoluene sulfonamide) was prepared as in Example 1. Ten specimens of the terpolyamide resin were subjected to the zinc chloride test for 16 days. None of the specimens exhibited cracks after the 16 days of testing in the zinc chloride solution. Example 4 A terpolyamide resin having an inherent viscosity of 1.48 and composed of 75 weight percent of nylon 612 segments, 20 weight percent of nylon 61 segments, and 5 weight percent of nylon 636 segments and plasticized with 1 & 5 weight percent of butylbenzenesulfonamide was prepared in accordance with The procedure described in Example 1. Ten specimens of the terpolyamide resin were subjected to the zinc chloride test for 16 days. None of the specimens exhibited cracks after the 16 days of testing in the zinc chloride solution. WHAT WE CLAIM IS:

1. A terpolyamide resin having distributed therein the following repeating segments

wherein x is 8 or 10:

8. A process for the preparation of a terpolyamide resin as claimed in Claim I

which comprises polycondensing aqueous salt solutions of precursors of the polymer segments, evaporating the water from the reaction mixture and allowing the polycondensation reaction to continue to completion, the aqueous salt solutions containing sufficient amounts of the precursors of segments (I), (2) and (3) to provide the terpolyamide of composition given in Claim 1.

9. A process according to Claim 7 substantially as described by reference to Example 1.