Polyamide chain extension process

ES 2 302 706 T3

DESCRIPTION

Process to extend the polyamide chain.

This invention relates to processes for increasing the relative viscosity (RV) of a reactive polyamide through the use of chain extender compounds.

Various methods have been proposed for imparting high viscosity to polyamides.

Catalysts are used to accelerate the reaction. For example, the synthesis of polyamide 6,6 involves the reaction of a diamine (hexamethylenediamine) and a diacid (adipic acid) to produce polyamide 6,6 and water. The rate of polyamide formation is highly dependent on the removal of water from the reaction system. Catalysts do speed up the reaction, but water removal is still the determining factor for speed.

Another method of imparting a high viscosity to polyamides is the so-called chain extension. Chain extension is based on a reaction between a polyamide chain end group (an acid end group or an amine end group) and a chain extender molecule with two reactive end groups that react with either the amine end group. or with the acid end group of the polyamide to connect two polyamide chains. Previous use of polyamide chain extenders has failed to increase RV enough to embrace the technology. The use of bis-lactams for acceleration of polyamidation was described by Flory in US Patent 2,682,526.

There is a need to take a low RV polyamide and quickly increase its RV to a predictable end product with a higher RV.

These and other objects of the invention will become clear in light of the following description.

This invention refers to a process that is to increase the relative viscosity (RV) of a reactive polyamide and comprises the steps of:

bringing the reactive polyamide and a chain extender compound into contact with each other selected from the group consisting of bis-N-acyl-bislactam compounds and mixtures thereof, both in a liquid phase, the reactive polyamide having a Starting RV, an amine end group concentration (AEG (R)) and a carboxyl end group concentration (CEG (R)), AEG (R) being greater than CEG (R), the chain extender compound having a lactam end group (LEG) concentration of at least about 10 equivalents per million grams of the reactive polyamide less than the AEG (R), for a period of time from 0.5 to 10 minutes, increased RV of reactive polyamide;

forming a product other than flakes, the product being selected from the group consisting of a spun article, blow molded articles, extruded articles and injection molded shaped articles; and subjecting the product to rapid cooling to room temperature in a state of unbalance in such a way that the product has a final RV greater than the starting RV and a concentration of terminal amine groups (AEG (P)) as defined by formula:

AEG (P) = {AEG (R) - LEG} ± X (Formula 1) where:

AEG (P) is the concentration of amine end groups in the product already subjected to rapid cooling in equivalents / 1,000,000 g of the product;

AEG (R) is the concentration of amine end groups in the reactive polyamide in equivalents / 1,000,000 g of the reactive polyamide;

LEG is the concentration of lactam end groups in the chain extender compound in equivalents / 1,000,000 g of the reactive polyamide;

{AEG (R) -LEG} is the theoretical or calculated amine end group concentration that would result from a stoichiometric reaction between the chain extender compound and the polyamide; Y

X is a deviation factor that is within the limits of plus or minus 5 amine end groups / million grams of polyamide with respect to the theoretical or calculated amine end group concentration that would result from a stoichiometric reaction between the chain extender compound and polyamide;

ES 2 302 706 T3 where formula 1 requires that the product be subjected to rapid cooling when the actual or measured amine end group concentration in the polyamide product, that is the AEG (P), is within a deviation factor X with respect to a stoichiometric reaction between the chain extender compound and the polyamide.

The invention may be more fully understood in light of the following detailed description thereof in connection with the accompanying drawings described below.

Figure 1 is a schematic illustration of a system that can be used to produce a polyamide filament in accordance with the present invention.

Figure 2 is a graph showing a schematic representation of relative viscosity versus time for a reaction to produce nylon 6,6 using a chain extender compound.

Throughout the following detailed description, like reference characters refer to like elements throughout the drawing figures.

I. The Process

The invention relates to a process that is to increase the relative viscosity (RV) of a reactive polyamide and comprises the steps of putting the reactive polyamide and a reactive chain extender compound in contact with each other, forming a product, and subjecting the product to rapid cooling to room temperature in a state of reaction unbalance to maintain the polymer at a RV level located within a limited and defined range of values ​​with respect to a maximum RV level reached during the process. .

A. The Contact Step

The first step in the process is to bring the reactive polyamide into contact with a chain extender compound, both of which are in a liquid phase.

The contacting step is prolonged for a period of reaction time, which is that which elapses between the point in time at which the first contact is established between the reactive polyamide and the chain extender compound, both being in the liquid state, and the point in time at which the formed product is subjected to rapid cooling. This reaction time period lasts for a period of time from 0.5 minutes to 10 minutes. If virtually no water or catalyst is added or present in the reaction mixture, the reaction time may be about 10 minutes. The expression "practically no water is added or present" means a water content of 0.08% to 0.18%. If water or a catalyst is added or present, the reaction time period is typically no more than a little plus or minus 4 minutes. If both water and a catalyst are added or present, the reaction time period is typically no more than a little plus or minus 2 minutes.

The contacting step can be carried out at a temperature of 5 ° C to 20 ° C higher than the melting point of the polymer. For example, for nylon 6,6, the temperature can be 270 ° C to 285 ° C. The contacting step can be carried out at a pressure of 0.25 psig (psig = pounds / inch²) at 250 psig, depending on the process and polymer used. Preferably, the contacting step is carried out while mixing the reagents.

1. The Reactive Polymer

The reactive or starting polyamide has a starting RV, an amine end group concentration (AEG (R)) and a carboxyl end group concentration (CEG (R)), with AEG (R) being greater than CEG (R). ).

Polymers that are suitable for use as the reactive polyamide in this invention include synthetic, melt-spinnable polyamide materials having recurring amide groups (--CO - NH--) as an integral part of the polymer chain. As used herein, the term "polyamide" refers to homopolymers and copolymers of polyamide and mixtures thereof.

Illustrative polyamides that can be used in accordance with the invention include poly (hexamethylene adipamide) homopolymer (i.e., nylon 6,6), poly (e-caproamide) homopolymer (i.e., nylon 6), polidodecanolactam (ie nylon 12), poly (tetramethylene adipamide) homopolymer (ie nylon 4,6), poly (hexamethyleneosebacamide) homopolymer (ie nylon 6,10), n-dodecanedioic acid homopolymer polyamide (i.e. nylon 6,12), dodecamethylenedioic acid homopolymer polyamide (i.e. nylon 12,12), copolymers thereof, and mixtures of the same themselves. Illustrative polyamides and copolyamides that may be employed in the process of this invention are those described in US Pat. 5,077,124, 5,106,946, and 5,139,729 (each in the name of Cofer et al.), Each of which is incorporated herein by reference. Illustrative polyamide blends that may be employed in the process of this invention are those described by Gutmann in Chemical Fibers International, pages 418-420, Volume 46, December 1996, said publication being incorporated herein by reference.

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Illustrative polyamides also include copolymers made from a dicarboxylic acid component, such as terephthalic acid, isophthalic acid, adipic acid, or sebacic acid, and a diamine component, such as hexamethylenediamine, 2-methylpentamethylenediamine, or 1,4-bis ( aminomethyl) cyclohexane.

Reactive polyamides can be prepared using batch or continuous polymerization methods that are known in the art. As illustrated in Figure 1, a suitable method for preparing polyamides is to store a polyamide salt solution / mixture in a salt storage container 10. The salt solution / mixture is fed from storage container 10 to a polymerizer 12 such as a continuous polymerizer or a batch-operated autoclave. In polymerizer 12, the polyamide salt solution / mixture is heated under pressure in an inert atmosphere substantially free of oxygen as is known in the art. The polyamide salt solution / mixture is polymerized and is thus converted into a molten polymer. When the polymerizer 12 is a continuous polymerizer, the molten polymer can be supplied from the continuous polymerizer 12 and transported such as by a booster pump 14 and by a transport line 16 to at least one spinneret 18 of at least one spinning machine 20 . Alternatively when polymerizer 12 is a continuous polymerizer, or when polymerizer 12 is a batch-operated autoclave, the molten polymer can be extruded from polymerizer 12, for example in the form of strands. The extruded polymer strands can be quenched in a cooling station 26, such as in a water bath, to be converted into solid polymer strands, and can be fed to a pelletizer 28 which cuts, molds or granulates the polymer in flake form. Other terms used to refer to these "flakes" include nodules, granules, and particulates. The flakes can be of any shapes and sizes that are suitable for use in the present invention.

Depending on the end use, the polymer flakes may have an RV based on formic acid of at least 30 to 180. This translates into a molecular weight which as a number average molecular weight is 15,000 to 25,000.

The flakes can be fed to a holding or conditioning container 30 where the flakes can be stored or conditioned, that is, e.g. ex. they can be heated, water can be added or removed, and / or they can be subjected to solid phase polymerization. The flakes can be conveyed by line 32 to a gravimetric or volumetric flake delivery feeder 34 that is adapted to deliver the flakes into a melt extruder 36. The flakes are melted in the melt extruder 36, and the molten polymer is extruded through an outlet of the melt extruder 36 into a transport line 38. The extruded molten polymer is conveyed, such as by means of a booster pump 40 , via transport pipe 38 to at least one row 18 of at least one spinning machine 20.

Typically, the residence time of the molten polymer in the melt extruder 36 and in the transport line 38 is 3 to 15 minutes, and preferably 3 to 10 minutes.

2. The Chain Extender Compound

Suitable chain extender compounds are bis-N-acyl-bislactam compounds and mixtures thereof. Preferred chain extender compounds are bis-N-acyl-bis-caprolactam compounds and mixtures thereof. The most preferred chain extender compounds include isophthaloyl-bis-caprolactam (IBC), adipoyl-bis-caprolactam (ABC), terephthaloyl-bis-caprolactam (TBC), and mixtures thereof. The preferred and highly preferred chain extender compounds are insensitive to the moisture content of the polyamide at the water levels generally present during polyamidation reactions, are effective within a wide range of RV's of the starting polyamide, and are not they generate by-products.

Chain extender compounds work based on a reaction between a polyamide chain with an acid end group or an amine end group and a chain extender compound with two reactive end groups that react with either the amine end group or the acid end group of the polyamide chain. Chain extender compounds that are bis-N-acyl-bislactam compounds react stoichiometrically with the amine end groups of polyamide chains. This means that a lactam end group of a bis-N-acyl-bislactam compound reacts with an amine end group of a polyamide chain. This offers predictability of the final RV and end-group balance sheet. As the amount of chain extender compound is increased, it connects to a greater number of the amine end groups of the polyamide chains creating a higher RV polyamide. The maximum RV is reached when the moles of chain extender compound are equal to half the equivalents of the amine end groups and all the amine end groups are consumed.

The chain extender compound has a lactam end group concentration (LEG) of at least about 10 equivalents per million grams of the reactive polyamide less than the AEG (R). This leaves a concentration (AEG (R)) of amine end groups of at least about 10 equivalents per million grams of the reactive polyamide after the chain extender compound has connected the amine end groups of the polyamide chains creating the RV polymer. highest. These remaining "at least about 10 equivalents" of amine end groups have been found to be desirable based on experimentation to minimize hydrolysis of the higher RV product back to the starting reagents.

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The chain extender compound can be fed to melt extruder 36 simultaneously or consecutively with respect to the flakes. In this case, when the flakes are melted in the melt extruder 36, the molten polymer contacts and reacts with the liquid chain extender compound. Alternatively, and indeed preferably, the chain extender compound is supplied to the conveyor line 16 or 38 with the molten polyamide. In this case, as soon as the chain extender compound melts, if it was not already in a liquid phase, it contacts and reacts with the molten polyamide. Preferably, when the chain extender compound is delivered to transport line 16 or 38, the chain extender compound is in a liquid phase. The addition of the chain extender compound to extruder 36 or transport line 16 or 38 can eliminate the need for the conditioner or any solid state polymerization vessel 30 prior to extruder 36 or transport line 38.

In each case, a particularly convenient method of adding the chain extender compound is to put the chain extender compound in a solution of mixed ingredients including the chain extender compound and a carrier. The purpose of adding the chain extender compound mixed with a carrier is to dilute the chain extender compound to allow a more accurate measurement of the amount of chain extender compound that is added. This form of addition further increases the dispersion of the chain extender compound in the polyamide. Suitable supports include low-melting polyamides (i.e., melting below 150 ° C), such as poly (N, N'-dibutylhexamethylenedodecanediamide), and other polyamides that are dispersed in polyamide, such as polypropylene. partially maleate (eg 3%), partially maleate polyethylene (eg 3%) and aliphatic polyesters. Low melting point polyamides are preferred supports.

3. The Catalysts

No catalyst is needed in this invention. However, one or more polyamidation catalysts can optionally be supplied normally to the polymerizer 12 simultaneously or consecutively with respect to the salt solution / mixture, but also to the melt extruder 36 simultaneously or consecutively with respect to the flakes and / or the transport pipe 16 or 38, thereby establishing contact with the molten polyamide.

The effect of adding a polyamidation catalyst, in addition to a chain extender compound, is that the catalyst shortens the time that elapses between the point in time of the initial contact between the molten polyamide and the chain extender compound and the point in time in which the resulting product has to be subjected to cooling fast to room temperature so that the product has a final RV greater than the starting RV and a concentration of amine end groups (AEG (P)) as defined by the above formula (1).

Polyamidation catalysts that are suitable for use in the process of the invention include phosphonic acids, phosphinic acids and their derivatives and salts. Exemplary suitable catalysts include those described in US Patents 3,365,428, 3,763,113, 3,944,518, 4,912,175 and 4,966,949 and in the references cited therein. Of these, the preferred catalysts are phenylphosphonic acid and 2- (2'-pyridyl) ethylphosphonic acid.

An effective amount of the catalyst or catalysts is added. Generally the catalyst is supplied to polymerizer 12 in an amount of 0.25 moles to 5 moles per million grams, mpmg, of polyamide (typically in an amount of 50 ppm to 1,000 ppm based on the polyamide). Preferably, the catalyst is added in an amount of 0.4 moles to 0.8 moles per million grams, mpmg, of polyamide (80 ppm to 160 ppm based on the polyamide). This range of amounts provides commercially useful polymerization rates during initial polymerization and / or after re-melting of the flake polymer such as in extruder 36 and / or in delivery line 16 or 38 under the conditions herein. invention, while minimizing the detrimental effects that can occur when the catalyst is used at higher levels, such as increased pressure in the spinning group during subsequent spinning.

A particularly convenient method of adding the polyamidation catalyst is to place the catalyst in a solution of polymer ingredients in which polymerization is initiated, such as e.g. ex. by adding to a salt solution such as the hexamethylene diammonium adipate solution that is used to make nylon 6,6.

Instead of or in addition to one or more liquid phase polyamidation catalysts, one or more solid state polymerization catalysts such as those described in International Patent Application WO 98/23666 can optionally be added.

The catalysts that are used in the polyamide production processes of the state of the art are generally not effective in increasing the RV of the polyamide when the starting polyamide has an RV of less than 30, and they are mostly not effective when the The starting polyamide has an RV of less than 45. When a catalyst and a chain extender compound are added in accordance with this invention, the RV of the reactive polyamide can be as low as on the order of about 4 when the chain extender compound is effective to increase the RV of the polyamide to the RV of the polyamide high enough that both the chain extender and the catalyst become effective in increasing its RV.

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Four. Additives

In the process of this invention the usual amounts of additives that are known in the art can be added to the polyamide. Such additives can be added when the chain extender compound comes into contact with the polyamide, or before. For example, typical additives include plasticizers, delusters, pigments, colorants, light stabilizers, thermostabilizers and / or oxidation stabilizers, antistatic additives to reduce static, additives to modify dyeability, agents to modify surface tension, etc.

Molten polymer in transport line 16 or 38 and flakes in conditioner 30 can contain varying amounts of absorbed water. Water can also be fed to conditioner 30 or melt extruder 36 as a control of the final RV of the product. The addition of water reduces the RV of the product.

B. The Formation Step

During the contacting step the reactive polyamide and the chain extender compound react to form a modified polyamide having a higher RV than the RV of the reactive polyamide.

After the contacting step, a product other than flakes is formed from the modified polyamide. As in the case of the polyamide that was used prior to this invention to make product, the modified polyamide of this invention must have a molecular weight that is suitable for use to form the desired end product. For example, when the product is a filament, the modified polyamide must be of a molecular weight suitable for filament formation in order to be melt-spun into filaments. For most end uses, including filament production, modified polyamides can have any molecular weight distribution.

The products made by the process of the invention are spun articles (such as filaments), blow-molded articles (such as bottles), extruded articles (such as films) and molded shaped articles. by injection.

Referring again to Figure 1, preferably the article is made by spinning the polyamide in the form of at least one filament 46. Metering pumps 41 can be used to pressure pump molten polymer from a manifold 42 connected to conveyor line 16 or 38 past spinning filter groups 44 and then through rows 18, each having a plurality of capillaries traversing the spinneret 18, thereby the molten polymer being spun through the capillaries in the form of a plurality of filaments 46.

C. The Rapid Cooling Step

Then the product is subjected to rapid cooling to room temperature, in such a way that the product has a final RV greater than the starting RV and a concentration of terminal amine groups (AEG (P)) as defined by the formula:

AEG (P) = {AEG (R) - LEG} ± X (1) where:

AEG (P) is the concentration of amine end groups in the product already subjected to rapid cooling in equivalents / 1,000,000 g of the product;

AEG (R) is the concentration of amine end groups in the reactive polyamide in equivalents / 1,000,000 g of the reactive polyamide;

LEG is the concentration of lactam end groups in the chain extender compound in equivalents / 1,000,000 g of the reactive polyamide;

{AEG (R) -LEG} is the theoretical or calculated amine end group concentration that would result from a stoichiometric reaction between the chain extender compound and the polyamide; Y

X is a deviation factor that is within the limits of plus or minus 5 amine end groups / million grams of polyamide with respect to the theoretical or calculated amine end group concentration that would result from a stoichiometric reaction between the chain extender compound and polyamide.

The filaments 46 exiting each row 18 are typically quenched by an air flow (illustrated in Figure 1 with arrows 48) that is transverse to the length of the filaments 46. By means of a convergence device 50 it can be done then the filaments 46 converge thus forming a thread, and said thread can then be wound by a winding device 54, for example on a tube 56 so as to be in the form of a thread spool 58.

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The resulting filaments 46 can be made into yarns 52 and fabrics for a variety of applications that are well known in the art. The product formed by the process of the invention can be further processed as long as it is not remelted in such processing steps. For example, after being formed, the filaments 46 can be subsequently stretched, textured, curled and / or cut, etc., as is well known in the art.

When chain extender compounds with polyamides were used prior to this invention, it was not appreciated that the product had to be quenched in an unbalanced state according to the above formula (1) to fix the polymer structure in the state in the that your chain is prolonged maintaining the high RV achieved by adding the chain extender compound. It is believed that the reason why the product has to be quenched according to the above formula (1) is that the addition of the chain extender compound appears to shift the reaction of the polyamide away from its equilibrium state.

This can be explained by referring to the following schematic chemical reaction of polyamide (i.e. nylon 6,6) in which a reactant (i.e. hexamethylenediamine (H₂N- (CH₂)₆-NH₂)) has an amine terminal group (-NH₂) and another reagent (i.e. adipic acid (HOOC- (CH₂)₄-COOH)) has an acid group (-COOH) and the products comprise polyamide chains with a plurality of amide groups (-NHCO-) ​​along the chains and water (H2O).

H2N- (CH2) 6-NH2 + HOOC- (CH2) 4-COOH θ R- (HN- (CH2) e-NHCO- (CH2) 4-CO)_n-R + H2O (3) where

R is H or OH; and n is 10 to 150.

This reaction continues until an equilibrium between reactants and products is established. This equilibrium can be expressed by the following equation.

K_eq = [-NHCO -] [H2O] / [- NH2] [- COOH] (4) where

K_eq is a constant;

[-NHCO-] is the concentration of amide groups;

[H2O] is the concentration of water;

[-NH2] is the concentration of free amine end groups; Y

[-COOH] is the concentration of free acid end groups.

However, when a bis-N-acyl-bislactam compound is added to the reaction mixture, one pair of amine end groups is consumed for each of the bis-N-acyl-bislactam molecules. This causes the concentration of amine end groups to decrease and the number of amide groups to increase, increasing the RV of the polymer, without variation in terms of acid and water end groups.

This is illustrated in Figure 2, which is a graph of RV versus time. At the Ti point in time, the chain extender compound contacts the polyamide 6,6 and / or the reactants to produce the polyamide, all of which are in a liquid state. The ingredients react rapidly up to the point T2 in time, in which the RV has increased to a maximum possible value and that surprisingly is not the state of equilibrium. It was surprisingly discovered that if the polymer is kept in a liquid state and if the product is not subjected to rapid cooling to stop the reaction, over time the polyamide will react with water (hydrolyze) returning to its equilibrium state and generating more amine end groups and acid end groups and fewer amide groups and a lower RV, as illustrated at point T₃ over time in Figure 2. See Figure 2. This clearly results in less than optimal efficacy of the chain extender compound. Similarly, if the product is subjected to rapid cooling according to the invention but is subsequently melted again, the water that is present in the mixture will bring the reaction back to a state of equilibrium with the lowest RV that is illustrated at point T₃ over time in Figure 2. The rate of the hydrolysis part of the curve is dependent on temperature, moisture content, and the presence of an amidation catalyst.

The invention recognizes that the desired product must be quenched to room temperature to maintain the polymer at an RV level that is within a limited and defined range of values ​​relative to its maximum RV level to maintain advantage. of the high RV that is produced by adding the

ES 2 302 706 T3 chain extender compound. This is captured by formula (1). In formula (1), AEG (P) is the actual or measured concentration of amine end groups in the already quenched product. The difference between the amine end group concentration in the reactive polyamide and the lactam end group concentration in the chain extender compound {AEG (R) -LEG} is the theoretical or calculated amine end group concentration that would result from a stoichiometric reaction between the chain extender compound and the polyamide. Formula (1) requires the product to be quenched when the actual or measured concentration of amine end groups in the polyamide product, AEG (P), is within a deviation factor X that is plus to minus 5 amine end groups / million grams of polyamide relative to the theoretical or calculated concentration of amine end groups that would result from a stoichiometric reaction between the chain extender compound and the polyamide. As such, the deviation factor X can be any number that is within a range of values ​​from 0 to 5. Preferably, X is any real number that is within a range of values ​​from 0 to 2. In the sense that As used in the present, the word "number" means all real numbers, including integers and fractions.

II. The product

The product that is made by the process of the invention preferably comprises a filament comprising a melt-spun synthetic polymer that includes:

polyamide repeating units (R₁);

polyamide chain extender halves (R₂), each being independently selected from the group consisting of bis-N-acyl-bislactam moieties; and end groups (R₃) each of which is independently selected from the group consisting of a hydrogen atom and a hydroxyl group;

including the polymer chains that each independently have a chemical structure such as the following:

R₃- (R₁-R2)_Y-R₁-R₃ (2) where y is an integer from 1-7; and the filament has a relative viscosity based on formic acid of at least about 30.

Suitable polyamide repeating units (R1) may each be independently selected from the group consisting of (I) - {CO (CH₂)_k-CONH- (CH₂)_mNH}_n-, where k and m are each independently an integer from 1-12, and n is an integer from 10-140, and (II) - {NH (CH₂)_x-CO}_z-, where x is an integer of 112 and z is an integer of 20-280. In formula (I), when k = 4 and m = 6, the formula represents a nylon 6,6 repeating unit. In formula (II), when x = 5, the formula represents a nylon 6 repeating unit.

Suitable polyamide chain extender moieties (R2) can each be independently selected from the group consisting of bis-N-acyl-bis-caprolactam moieties. Preferably R₃ each is independently selected from the group consisting of an isophthaloyl-bis-caprolactam (IBC) moiety, an adipoyl-bis-caprolactam (ABC) moiety, and a terephthaloyl-bis-caprolactam (TBC) moiety.

Using the reagents described here and / or following the procedures described here would produce other products.

The advantages

This invention allows for higher capital productivity, lower manufacturing cost, and greater process flexibility compared to prior methods for making high RV polyamides. The chain extension process of the invention is very fast and takes place in minutes or seconds, contrary to the hours that were necessary in the methods of the state of the art. Due to the rapid chain extension chemistry, higher RV polymer can be made without exposing the polymer to long periods of high temperature, and oxidation and branching are therefore minimized.

Definitions and test methods

Unless otherwise described, the following test methods were used throughout this specification to make the following determinations.

In the sense in which the expression is used herein, the relative viscosity or relative viscosity (RV) of polyamides referred to formic acid refers to the relationship between the viscosities of the solution and the solvent as measured in a viscometer. capillary at 25 ° C. The solvent is formic acid which contains

ES 2 302 706 T3 10% by weight of water. The solution is polyamide polymer dissolved at 8.4% by weight in the solvent. This test is based on the Test Method of ASTM D 789. The actual or measured concentration of amine end groups (AEG) can be determined by means of the following steps: Weigh exactly 1,000 g of a dry ground polyamide sample and put them in a cuvette equipped with a magnetic stirrer. Add 70 ml of phenol / methanol solution in a volumetric ratio of 85/15 (menol) to the cuvette. Cover and shake until the sample is dissolved. Titrate the polyamide-menol solution with perchloric acid (HClO₄) 0.025N in methanol using an automatic titrator. 70 ml of pure (virgin) menol solution are titrated in the same way. The amine end group (AEG) concentration is then determined using the following formula:

amine end groups (AEG) = (AB) (N) (1000) / (W) (5) where:

A = ml of HClO solution₄ to titrate the polyamide-menol solution.

B = ml of HClO solution₄ to assess the virgin solution.

N = Normality of the HClO solution₄ in equivalents per liter.

W = Weight of the polyamide sample in g.

AEG units are equivalents of amine end groups per 1,000,000 g of polyamide polymer. AEG (R) refers to the amine end groups of the reactive or starting polyamide. On the other hand, AEG (P) refers to the amine end groups of the polyamide obtained as a product, that is, of the article already subjected to rapid cooling.

The actual or measured concentration of carboxyl end groups (CEG) can be determined by the following steps: Weigh exactly 3,000 g of a dry, ground polyamide sample and place it in a cuvette equipped with a magnetic stirrer. Add 100 ml of benzyl alcohol to the cuvette. Cover and shake with the addition of heat until the sample has dissolved. Using a phenolphthalein indicator, titrate the contents of the beaker with a normal 0.1N aqueous potassium hydroxide (KOH) solution. 100 ml of pure benzyl alcohol (control) are titrated in the same way. The concentration of carboxyl end groups (CEG) is then determined using the following formula:

carboxyl end groups (CEG) = (AB) (N) (1000) / (W) (6) where

A = ml of KOH solution to titrate the polyamide solution.

B = ml of KOH solution to titrate the control.

N = Normality of the KOH solution in equivalents per liter.

W = Weight of the polyamide sample in g.

CEG units are equivalents of carboxyl end groups per 1,000,000 g of polyamide polymer. CEG (R) refers to the carboxyl end groups of the reactive or starting polyamide. On the other hand, CEG (P) refers to the carboxyl end groups of the polyamide that is obtained as a product, that is, of the article already subjected to rapid cooling.

Similar suitable methods for determining AEG and CEG are described in The Encyclopedia of Industrial Chemical Analysis, Vol. 17, John Wiley & Sons, New York, 1973, p. 293-294, and in US Patent 3,730,685, both publications being incorporated herein by reference.

The actual or measured concentration of lactam end groups (LEG) can be determined on the basis of the weight of the biscaprolactam chain extender compound used by means of the following formula:

lactam end groups (LEG) = (2) (W '/ M) (1,000,000) / (W) (7) where

W '= Weight of biscaprolactam chain extender compound in g.

M = Molecular weight of the biscaprolactam chain extender compound.

W = Weight of the polyamide sample in g.

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LEG units are equivalents of lactam end groups per 1,000,000 g of polyamide polymer.

All parts and percentages are by weight based on total weight, unless otherwise indicated.

Examples

This invention is now illustrated by the following specific examples. Examples prepared according to the process of the present invention are indicated with numerical values. Comparative or Control Examples are indicated by letters.

The Synthesis of Chain Extender Compounds

The adipoylbiscaprolactam (ABC) chain extender compound used in the examples below was prepared by dissolving 136 grams of caprolactam (1.2 moles) in 500 ml of tetrahydrofuran (THF) in a 2 liter Erlenmeyer flask, cooling the resulting solution in an ice bath to less than 5 ° C, and slowly adding 100 grams of adipoyl chloride (0.55 mole) with stirring. The temperature was kept at a level of minus 5 ° C. 200 ml of pyridine was added to the stirred solution to form a precipitate of ABC and pyridinium chloride. The mixture was stirred for 1/2 hour at less than 5 ° C and was then heated to boiling for 30 minutes, the hot solution then being poured into a 3 gallon (13.5 liter) bucket. ) half filled with a 50/50 mixture of water and ice, while vigorously stirring. ABC precipitates, and all other ingredients remain in solution. Solid AUC (155.8 grams) was collected by aspiration filtration.

Isophthaloylbiscaprolactam (IBC) was prepared by the same method as in the case of ABC, except for the fact that the 100 g of adipoyl chloride were replaced by 112 g of isophthaloyl chloride.

Terephthaloylbiscaprolactam (TBC) was prepared by the same method as in the case of ABC, except for the fact that the 100 g of adipoyl chloride were replaced by 112 g of terephthaloyl chloride.

Examples 1-3

These Examples demonstrate that since the polyamide is reactive (i.e., the nylon 6,6 homopolymer) contacted with different amounts of a chain extender compound (i.e., adipoylbiscaprolactam (ABC)), the greater the amount of compound chain extender that is added, the higher the RV of the product, the more amine end groups are consumed, and in each case the reactions satisfy formula (1).

In Examples 1, 2 and 3, nylon 6,6 homopolymer was used as the reactive or starting polyamide. The nylon 6,6 homopolymer was prepared from an aqueous solution of adipic acid / hexamethylenediamine salt, using an excess of 0.56% by weight of hexamethylenediamine, without the addition of catalyst and using standard autoclaving methods. This amine-terminated nylon 6,6 had an RV of 37.9, an AEG (R) of 97.5 equivalents / million grams of polyamide, and a CEG (R) of 53 equivalents / million grams of polyamide.

Adipoylbiscaprolactam (ABC) was added to 6.00 g of the nylon 6.6 homopolymer and mixed thoroughly in a solid state in a test tube. The amount of ABC added was increased in Example 2 over Example 1 and increased in Example 3 over Example 2. The tube had a small wire stirrer, was covered with a stopper, and had a nitrogen blanket. . The test tube was placed in a molten metal bath at 286 ° C for a period of 4 minutes, after which the tube was quenched in a water bath at room temperature. The polymer was removed from the tube and tested. Table 1 indicates for each Example (1) the weight of AUC used, (2) the concentration of lactam end groups (LEG) based on the weight of AUC, (3) the determined RV value, (4) the actual value or measured from the concentration of amine end groups (AEG (P)) of the nylon obtained as a product, (5) the calculated or theoretical amine end group concentration (calculated AEG (P)) of the nylon obtained as a product based on a stoichiometric reaction of the amine end groups of reactive nylon and the lactam end groups of ABC, and ( 6) the deviation factor X that has been defined in formula (1).

Example A

The procedure of Example 1 was followed using the same materials, equipment and conditions, except that no ABC chain extender compound was added. Table 1 indicates the RV of the product and the AEG (P) of the product for this Example A.

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TABLE 1

<td rowspan="2">Example</td><td rowspan="2">ABC (g)</td><td rowspan="2">ABC LEG</td><td colspan="2">Measurements in Nylon Obtained as a Product</td><td rowspan="2">AEG (P) calculated (AEG (R) - LEG)</td><td rowspan="2">X</td>

<td>RV</td><td>AEG (P)</td>

<td>TO</td><td> 0</td><td> 0</td><td> 42,7</td><td> 88,3</td><td>NA *</td><td>NA</td>

<td> 1</td><td> 0,045</td><td> 44,6</td><td> 56,4</td><td> 52,7</td><td> 52,9</td><td> -0,2</td>

<td> 2</td><td> 0,060</td><td> 59,5</td><td> 72,3</td><td> 34,9</td><td> 38,0</td><td> -3,1</td>

<td> 3</td><td> 0,075</td><td> 74,4</td><td> 92,0</td><td> 23,9</td><td> 23,1</td><td> +0,8</td>

* NA means not applicable. When no chain extender compound is added, there is no LEG.

Examples 4 and 5

These Examples demonstrate that when different reactive polymers with different starting RVs are put in contact with a chain extender compound, the resulting products have higher RVs than those of the reactive polymers, with fewer amine end groups, and in each case the reactions satisfy formula (1). These Examples also illustrate the use of isophthaloylbiscaprolactam (IBC) as a chain extender compound.

The starting polymer used in Example 4 is the same amine-rich nylon 6,6 homopolymer that was used in Example 1. The starting polymer used in Example 5 was an amine-rich nylon 6,6 homopolymer. amine which was synthesized in a method identical to that used in Example 1, except that a 2% by weight excess of hexamethylenediamine was used. The nylon 6,6 that was used in Example 5 had an RV = 17.1, an AEG (R) = 244, and a CEG (R) = 16.

Otherwise, the same procedure as that used in Example 1 was applied in these Examples, except that ABC was replaced by isophthaloylbiscaprolactam (IBC).

Table 2 indicates (1) the determined RV, (2) the amine end group concentrations (AEG (R)) of the reactive nylons, (3) the IBC weights used, (4) the caprolactam end group concentrations based on in the weight of IBC (LEG), (5) the measured RVs, (6) the actual or measured concentrations of amine end groups (AEG (P)) of the nylon obtained as product, (7) the calculated amine end group concentrations (calculated AEG (P)) based on a stoichiometric reaction of the amine end groups of reactive nylon and IBC, and (8) the bias factor X as defined in the formula (1).

TABLE 2

<td rowspan="2">Ex</td><td rowspan="2">RV of reagent</td><td rowspan="2">Nylon AEG (R)</td><td rowspan="2">IBC, g</td><td rowspan="2">IBC LEG</td><td colspan="2">Measures on the Nylon obtained as a Product</td><td rowspan="2">Calculated AEG (P) (AEG (R) LEG)</td><td rowspan="2">X</td>

<td>RV</td><td>AEG (P)</td>

<td> 4</td><td> 37,9</td><td> 97,5</td><td> 0,045</td><td> 42,1</td><td> 52,6</td><td> 52,7</td><td> 55,4</td><td> -2,7</td>

<td> 5</td><td> 17,1</td><td> 244,0</td><td> 0,090</td><td> 84,3</td><td> 27,3</td><td> 161,2</td><td> 159,7</td><td> +1,5</td>

Examples 6-8

These Examples demonstrate that when a reactive polymer (i.e., nylon 6,6 homopolymer) is contacted with varying amounts of IBC, to which a support has been added, as the chain extender compound in a commercial facility in a spinning machine by varying the dryness of the reactive polymer and the amount of chain extender, the resulting products have higher RVs than those of reactive polymers, with fewer amine end groups, and in each case the reactions satisfy formula (1).

The nylon 6,6 homopolymer for Examples 6-8 was prepared in an autoclave from an aqueous solution of adipic acid / hexamethylenediamine salt containing an excess of 0.5% by weight of hexamethylenediamine (to generate nylon 6 , 6 rich in amine), 50 ppm of "Dow Conning Antifoam B", which is an antifoam agent, and 16 ppm of manganous hypophosphite, which is an antioxidant. The homopolymer had an RV of 40, an AEG (R) of 97 equivalents per million grams of polymer, and a CEG (R) of 54 equivalents per million grams of polymer. The homopolymer was pelletized in the form of flakes.

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The nylon 6,6 homopolymer flakes were fed to a twin screw extruder of a spinning machine that was equipped as a conveyor line to the spinneret as described in US Patent 5,370,935, which is incorporated herein. by reference. For Example 8, the nylon flakes of Example 6 were used, and the polymer flakes were exposed to nitrogen gas at 105 ° C as the flakes were supplied from the conditioner to the extruder to dry the flakes before their contribution to the interior of the extruder. The temperature in the transport pipe was 288 ° C. Mixing was done using a series of Koch and Kenics in-line static mixers.

A chain extender compound concentrate of 40% by weight IBC and 60% low molecular weight polyamide support (with a Mw of about 3500) was prepared. The support was poly (N, N'-dibutylhexamethylenedodecanediamide) synthesized from N, N'-dibutylhexamethylene, dodecanediamide and stearic acid as termini prepared using the method described in US Patent 3,900,676, which is incorporated herein by reference. The chain extender compound concentrate was injected into the delivery line at a fixed rate such that predetermined concentrations of the chain extender compound were reached in the total reagents. The residence time of the polymer in the transport line between the injection point and the spinneret was approximately 1 minute and 30 seconds.

Table 3 indicates for each of these Examples (1) the state of dryness of the starting polymer, (2) the concentration of IBC, (3) the concentration of caprolactam end groups (LEG) based on the injection percentage of the concentrate. of IBC, (4) the determined RV, (5) the actual or measured concentrations of amine end groups (AEG (P)) of the nylon fiber obtained as a product, (6) the calculated amine end group concentrations (calculated AEG (P)) based on a stoichiometric reaction of the amine end groups of the starting nylon and the IBC in the transport line, and (7) the deviation factor X that is defined in formula (1).

Example B

This is a comparative example in which the procedure is the same as in Example 6 except that no IBC concentrate was injected into the delivery line. The relevant process variables and properties are listed in Table 3.

Example C

This is a comparative example in which the procedure is the same as in Example 6, except for the fact that a pure polyamide support without IBC was injected into the transport pipe at a percentage of 1% by weight. The other relevant process variables and properties are listed in Table 3.

TABLE 3

<td rowspan="2">Ex</td><td rowspan="2">Polymer Dryness</td><td rowspan="2">wt% IBC concentrate</td><td rowspan="2">IBC (LEG)</td><td colspan="2">Measures on the Nylon obtained as a Product</td><td rowspan="2">Calculated AEG (P) (AEG (R) -LEG)</td><td rowspan="2">X</td>

<td>RV</td><td>AEG (P)</td>

<td> 6</td><td>As received</td><td> 1,25%</td><td> 28,1</td><td> 52,1</td><td> 70,5</td><td> 68,9</td><td> +1,6</td>

<td> 7</td><td>As received</td><td> 2,50%</td><td> 56,2</td><td> 74,4</td><td> 40,6</td><td> 40,8</td><td> -0,2</td>

<td> 8</td><td>Dried</td><td> 1,25%</td><td> 28,1</td><td> 56,1</td><td> 69,0</td><td> 68,9</td><td> +0,1</td>

<td>B</td><td>As received</td><td> 0</td><td> 0</td><td> 40,8</td><td> 96,7</td><td>NA</td><td>NA</td>

<td>C</td><td>As received</td><td> 0</td><td> 0</td><td> 40,9</td><td> 97,5</td><td>NA</td><td>NA</td>

Examples 9-11

These Examples demonstrate that starting polymers that have higher RVs than the starting polymers of other Examples when contacted with the IBC chain extender compound in a commercial installation on a spinning machine result in products that still have RVs. higher than those of high RV reactive polymers, with fewer amine end groups, and in each case the reactions satisfy formula (1).

The same conditions, the same equipment and the same materials that were used in Example 6 were used in Examples 9-11, except for the fact that the nylon 6,6 flakes were solid phase polymerized before being added to the extruder of the spinning machine and varied the injection percentage of the

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IBC. The flakes were solid phase polymerized by exposing the flakes to a circulating nitrogen gas at 150 ° C for 16 hours. The solid phase polymerized nylon flakes had an RV = 78.3, an AEG (R) = 75.8 and a CEG (R) = 35.1.

Table 4 indicates for each of these Examples (1) the injection percentage of the IBC concentrate, (2) the caprolactam end group (LEG) concentrations based on the injection percentage of the IBC concentrate, (3) the RV determined, (4) the actual or measured concentrations of amine end groups (AEG (P)) of the nylon fiber obtained as a product, (5) the calculated amine end group concentrations (calculated AEG (P)) based on a stoichiometric reaction of the amine end groups of the reactive nylon and the IBC in the transport tubing, and (6) the deviation factor X that is define in formula (1).

TABLE 4

<td rowspan="2">Ex</td><td rowspan="2">wt% IBC concentrate</td><td rowspan="2">IBC (LEG)</td><td colspan="2">Measurements on Final Nylon</td><td rowspan="2">Calculated AEG (P) (AEG (R) LEG)</td><td rowspan="2">X</td>

<td>RV</td><td>AEG (P)</td>

<td> 9</td><td> 0,425%</td><td> 9,6</td><td> 93,7</td><td> 65,8</td><td> 66,2</td><td> -0,4</td>

<td> 10</td><td> 0,85%</td><td> 19,1</td><td> 103,2</td><td> 59,7</td><td> 56,7</td><td> +3,0</td>

<td> 11</td><td> 1,25%</td><td> 28,1</td><td> 116,3</td><td> 50,7</td><td> 47,7</td><td> +3,0</td>

Example 12

This Example demonstrates that a nylon 6,6 copolymer that contacts terephthaloylbiscaprolactam (TBC) as a chain extender compound results in obtaining a product that has a higher RV than that of the reactive polymer, with fewer amine end groups, satisfying the reaction is formula (1).

A nylon 6.6 copolymer was prepared in the same manner as the nylon 6.6 homopolymer in Example 1, except that 5 mole% of the hexamethylenediamine was replaced by the same number of moles of 1.4 -bis (methylamine) cyclohexane. The nylon 6,6 copolymer produced had an RV = 41.6, an AEG (R) = 122.9 and a CEG (R) = 42.8.

0.06 g of terephthaloylbiscaprolactam (TBC) was added to 6.00 g of the nylon 6.6 copolymer. This was mixed, heated, and quenched as described in Example 1. The copolymer produced was removed from the tube and tested.

Table 5 indicates (1) the weight of TBC used, (2) the concentrations of caprolactam end groups (LEG) based on the weight of TBC, (3) the RV values ​​determined, (4) the concentrations of amine end groups. actual or measured (AEG (P)) of the nylon obtained as a product, (5) the calculated amine end group concentrations (AEG (P) calculated) based on a stoichiometric reaction of the amine end groups of reactive nylon with the compound extender. TBC chain, and (6) the deviation factor X that is defined in formula (1).

Example D

This is a comparative example in which the weight, procedure and conditions of the example are the same as those of Example 12, except that no TBC chain extender compound was added. The relevant process variables and properties are listed in Table 5.

TABLE 5

<td rowspan="2">Ex</td><td rowspan="2">g of TBC</td><td rowspan="2">IBC (LEG)</td><td colspan="2">Measurements in Nylon Obtained as a Product</td><td rowspan="2">AEG (P) calculated (AEG (R) - LEG)</td><td rowspan="2">X</td>

<td>RV</td><td>AEG (P)</td>

<td> 12</td><td> 0,06</td><td> 56,2</td><td> 94,8</td><td> 67,9</td><td> 66,7</td><td> +1,2</td>

<td>D</td><td> 0,0</td><td> 0</td><td> 43,1</td><td> 118,2</td><td>NA</td><td>NA</td>

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Examples 13-15

These Examples demonstrate that a nylon 6 copolymer that is contacted with IBC as the chain extender compound, as the amount of chain extender compound is increased, results in obtaining a product that has a RV higher than that of of the reactive copolymer, more amine end groups being consumed, and the reactions satisfy formula (1).

The nylon 6 copolymer that was used in Examples 13-15 was prepared based on caprolactam and 0.59% by weight of hexamethylenediamine in an autoclave to produce amine terminally rich nylon 6. The produced nylon 6 was pelletized in the form of flakes which were rinsed with water to remove the unreacted caprolactam. The polymer flakes had an RV = 20.0, an AEG (R) = 106.6 equivalents / million grams of polymer and a CEG (R) = 57.1 equivalents / million grams of polymer.

The same procedure was used as in Example 1, except that the nylon 6 flakes were used in place of the nylon 6,6 flakes and IBC was used in place of ABC.

Table 6 indicates for each of these Examples (1) the weight of IBC used, (2) the concentration of caprolactam end groups (LEG) based on the weight of IBC, (3) the RV values ​​determined, (4) the actual or measured amine end group concentrations (AEG (P)) of the product nylon, (5) the calculated amine end group concentrations of the product nylon (calculated AEG (P)) based on a stoichiometric reaction of the amine end groups of the reactive nylon 6 and IBC chain extender compound, and (6) the deviation factor X.

Example E

This is a comparative Example in which the weight, procedure and conditions of the example are the same as in Example 13, except that no IBC chain extender compound was added. The process variables and the resulting data are indicated in Table 6.

TABLE 6

<td rowspan="2">Ex</td><td rowspan="2">g for ABC</td><td rowspan="2">IBC (LEG)</td><td colspan="2">Measurements in Nylon Obtained as a Product</td><td rowspan="2">Calculated AEG (P) (AEG (R) LEG)</td><td rowspan="2">X</td>

<td>RV</td><td>AEG (P)</td>

<td> 13</td><td> 0,03</td><td> 28,1</td><td> 27,2</td><td> 77,0</td><td> 78,5</td><td> -1,5</td>

<td> 14</td><td> 0,045</td><td> 42,1</td><td> 31,0</td><td> 65,2</td><td> 64,5</td><td> +0,7</td>

<td> 15</td><td> 0,06</td><td> 56,2</td><td> 41,4</td><td> 49,8</td><td> 50,4</td><td> -0,6</td>

<td>AND</td><td> 0,0</td><td> 0</td><td> 20,4</td><td> 104,5</td><td>NA</td><td>NA</td>

Taking advantage of the teachings of the present invention as set forth above, those skilled in the art will be in a position to make numerous modifications thereto. These modifications are to be understood as being within the scope of the present invention as set forth in the accompanying claims.