KR20020041589A - Manufacture of high strength, heat-resistant polyamide 6 fiber for the industrial use - Google Patents

Abstract

PURPOSE: Provided is a manufacturing method of high strength polyamide 6 which is characterized by preventing denaturation of polyamide, having high strength and excellent thermal stability, having high degree of polymerization, having excellent workability and being useful for filament yarn for tire cord. CONSTITUTION: The high strength polyamide 6 is obtained by a process containing the steps of: as a first process, mixing caprolactam and 0.1-5wt.% of water as initiator, under 1.0wt.% of dicarboxylic acid(based on weight of caprolactam) as chain regulator and 5-100ppm of phosphoric acid as polymerizing catalyst to produce a mixture; melt-condensation polymerizing the mixture at 240-300deg.C to produce prepolymer; and then, as a second process, removing water at 240-300deg.C under a condition of pressure reduction to promote a condensing reaction. The polyamide 6 contains under 30meq/kg of amine end and under 100meq/kg of total ends.

Description

Manufacturing method of high strength, heat-resistant polyamide 6 fiber for the industrial use

The present invention relates to a method for producing a high strength polyamide 6 industrial company having excellent heat resistance, and more particularly to a method for producing a polyamide fiber that maintains a high degree of polymerization of at least 30,000 molecular weight and has excellent strength characteristics and heat stability.

Polyamide fibers have excellent strength and are widely used in medical and industrial applications.

However, when used in harsher conditions, for example tire cords, there is an urgent need for high strength fibers with greater strength and better thermal stability.

Generally, in order to obtain high strength, a method of increasing the degree of polymerization has been used. Usually, caprolactam is melt-condensed with water, which is a polymerization initiator, to produce a polymer having a molecular weight of 30,000 or more and melt spinning.

However, polyamides prepared with water as a polymerization initiator can obtain polymers of high molecular weight, but due to uneven molecular chains, the physical properties are non-uniform, and when melt spinning at a high temperature around 280 ° C, depolymerization occurs. The degree of polymerization may be reduced or pyrolysis may cause workability defects such as trimming.

Therefore, it is necessary to make the polyamide chain uniform in order to eliminate such physical property unevenness. In this case, monocarboxylic acid or monoamine or a salt thereof is added to the beginning of polymerization as a molecular chain regulator, or dicarboxylic acid or diamine is used. It is also preferable to manufacture by adding.

The addition of an amine compound among the compounds is advantageous in terms of improving dyeing properties in general medical doctors, but is disadvantageous in order to obtain high strength.

The reason for this is that polyamide pyrolysis at high temperature proceeds at the amine end, so that it has an excess of carboxyl end relative to the amine end to suppress deformation in a later step.

It is also more advantageous to obtain a higher strength than the monocarboxylic acid to have an excess of carboxyl terminal relative to the amine terminal by using a bifunctional compound, that is, dicarboxylic acid.

U.S. Patent No. 2,174,527 discloses a method for stabilizing molecular weight by blocking an amine end with an excess of dicarboxylic acid in a diacid-diamine polyamide, and U.S. Patent No. 2,241,321 discloses sebacic acid in the presence of diamine. A method of polymerization using a chain extender is shown.

In addition, U.S. Patent No. 3,386,967 discloses a polymer having a high molecular weight of 25,000 to 40,000 by a multi-step process using 0.1 to 0.7 mol% of dicarboxylic acid, that is, adipic acid, sebacic acid, dodecanediol acid and terephthalic acid. A method of preparing the compound is disclosed, and US Pat. No. 3,839,530 discloses a method of using a dicarboxylic acid ester as a chain control agent. However, the ester compound has a relatively high volatility and thus is difficult to handle.

More recently, U. S. Patent No. 5,149, 758 has a high strength medical polyamide polymer having 0.1 to 0.6% by weight of terephthalic acid or isophthalic acid as a chain regulator, with a total terminal content of 115 to 150 meq / kg and an amine terminal content of 25 meq / kg. A method of making is shown.

The conventional methods described above are methods of adding terminal terminators such as monocarboxylic acid or dicarboxylic acid at the beginning or the middle of the polymerization, and these methods are not only low productivity due to delayed polymerization rate but also high degree of polymerization of polyamide. There is a drawback that is difficult to obtain.

Therefore, in order to solve this drawback, Japanese Patent Application Laid-Open No. 1-236,238 prepares a polyamide having a high degree of polymerization by a conventional method, and adds a bifunctional N-acyllactam during melt spinning to produce a high strength polyamide. US Patent No. 3,890,286 discloses a method of adding dicarboxylic acid esters upon spinning to produce high strength polyamides with excess carboxyl ends.

The present invention has been made to solve the problems of the conventional method as described above, and to provide a high degree of polymerization and high strength industrial yarn method.

The present invention is described in detail as follows.

The present invention uses water as a polymerization initiator in a two-stage polymerization column in which a prepolymer is prepared in one step, and the prepared prepolymer is removed in a vacuum in two steps to remove water. Is added as a molecular chain modifier to melt polycondensation, thereby reducing the terminal amine content and increasing the carboxyl terminus, thereby improving thermal stability by inhibiting deformation from the terminal amine, and simultaneously improving the degree of polymerization. Or it relates to a high-strength polyamide 6 industrial company excellent in high strength and thermal stability, characterized in that it is added during polymerization.

In the present invention, water is added as a polymerization initiator in accordance with the characteristics of 0.1 to 5.0% by weight of a polymerization tower so that a high strength polyamide having excellent heat resistance can be produced without a decrease in the degree of polymerization, and dicarboxylic acid is 1.0 weight compared to caprolactam as a chain regulator. % Or less, more preferably 0.2 to 0.6% by weight to have an excess of carboxyl terminal relative to the amine terminal, the amine terminal content of the extracted and dried chip is 30 meq / kg or less, the total terminal content is 100 meq / kg It is characterized by the following.

In the present invention, since the degree of polymerization is remarkably lowered when the amount of water added exceeds 5% by weight, the amount of water added is preferably 0.1% by weight or more and 5% by weight or less.

In addition, the present invention is a method characterized by adding a phosphate compound in parallel with the purpose of further improving the degree of polymerization together with the addition of dicarboxylic acid.

The present invention is described in more detail as follows.

In order to increase the degree of polymerization, the polymerization of caprolactam is carried out in a two step process.

In the first step (VK), 0.1 to 5% by weight of caprolactam and an initiator, 0.1 to 5% by weight of dicarboxylic acid as the chain regulator, and 5 to 100 ppm of phosphoric acid are added with a polymerization catalyst. Melt polycondensation of the mixture at 240 ℃ to 300 ℃ to prepare a prepolymer, high polymerization degree by promoting the condensation reaction by removing the water under reduced pressure polymerization temperature 240 to 300 ℃ in a two-stage (VS) process Polyamide 6 is prepared.

Here, phosphoric acid as a polymerization catalyst may be added not only before the polymerization but also during the polymerization.

The polymerization time was adjusted until the total terminal content became 100 meq / kg or less.

Dicarboxylic acids that can be used include alkanedicarboxylic acid, cycloalkane dicarboxylic acid, aromatic dicarboxylic acid. For example, alkanedicarboxylic acid include adipic acid, pivelic acid, suberic acid, azela. Acids, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, and preferred are adipic acid and sebacic acid.

Cycloalkane dicarboxylic acids include cycloalkane-1,3-dicarboxylic acid and cyclohexane-1,4-dicarboxylic acid, with cyclohexane-1,4-dicarboxylic acid being preferred.

Aromatic dicarboxylic acids include terephthalic acid and isophthalic acid.

In general, the phosphoric acid additive is added before or during the polymerization, and the reaction rate is relatively faster than that of the non-addition, and it is advantageous to prepare a polyamide having a high degree of polymerization.

Phosphoric acid compounds used include phosphoric acid, phosphorous acid, hypophosphorous acid and the like.

In the present invention, as the heat stabilizer, copper halide, potassium halide and the like can be added together.

In the present invention, dicarboxylic acid is added at 1.0% by weight or less relative to caprolactam to have an excess of carboxyl terminal relative to the amine terminal, and a number average molecular weight of 30,000 to Highly strong polyamides with a high degree of polymerization of 40,000 were prepared.

When the dicarboxylic acid is added in an amount exceeding 1.0% by weight as a chain regulator, it is difficult to obtain the required property property in a post process due to the marked decrease in the degree of polymerization.

In addition, when the amine end content exceeds 30 meq / kg after the polymerization reaction, the properties of the amine end due to denaturation and post-polymerization reaction result in poor strength and poor workability and poor workability during heat treatment.

In addition, the higher the total terminal content, the lower the degree of polymerization and the non-uniform polyamide chain length due to post-polymerization between the amine end and the carboxyl end, thereby lowering the heat stability and strong maintenance rate.

Therefore, it is important to make the total end content below 100 meq / kg.

It is preferable that the moisture content of the chip used by this invention shall be 0.2 weight% or less.

This is because excessive moisture content promotes hydrolysis during spinning, lowering the degree of polymerization and weakening thermal stability.

Hereinafter, the present invention will be described in more detail with reference to Examples.

The present invention is not limited to the following examples.

Example 1

2 parts by weight of water was used as an initiator in 100 parts by weight of caprolactam, and 0.2 part by weight of terephthalic acid, which is dicarboxylic acid, was used as a chain regulator in a polymerization reactor and polymerized at 270 ° C for 8 hours.

After removing the internal pressure and reacted for 6 hours at a reduced pressure of 250 torr (torr) to prepare a polyamide 6 chip.

The extract content of the obtained chips was 10.8 wt%, and the relative viscosity (95% sulfuric acid, 25 ° C.) was 3.03.

The relative viscosity after extraction was 3.34, and the amine end content and the carboxyl end content were 24 meq / kg and 59 meq / kg, respectively.

The extracted chip was blended with 0.3 parts by weight of copper iodide and 1.2 parts by weight of potassium iodide to prepare a dry chip, which was melt spun at a moisture content of 0.05% by weight and a melting temperature of 280 ° C to prepare a yarn for tire cords of 1260 deniers.

The obtained yarn had a strength of 9.71 g / De, an elongation of 24%, and a spinning workability of 90.3%.

Raw cord prepared by combining two strands of yarn was heat treated at 180 ° C. for 10 hours, and the strength was 93%.

Comparative Example 1

Only 100 parts by weight of caprolactam was used as an initiator in a 2 parts by weight polymerization reactor and polymerized at 275 ° C for 9 hours.

After removing the internal pressure and reacted for 4 hours at a reduced pressure of 250 torr to prepare a polyamide 6 chip.

The extract content of the obtained chips was 11.4%, and the relative viscosity (95% sulfuric acid, 25 ° C) was 3.03.

The relative viscosity after extraction was 3.28, and the amine end content and the carboxyl end content were 40 meq / kg and 40 meq / kg, respectively.

The extracted chip was blended with 0.3 parts by weight of copper iodide and 1.2 parts by weight of potassium iodide to prepare a dry chip.

The prepared chip was melt spun at a moisture content of 0.05% by weight and a melting temperature of 280 ° C. to prepare a yarn for tire cords having a 1260 diameter.

The obtained yarn had a strength of 9.16 g / De, an elongation of 23%, and a spinning workability of 68%.

The raw cord prepared by combining two strands of yarn was heated at 180 ° C. for 10 hours, and the strong retention rate was 88%.

Example 2

2 parts by weight of water was used as an initiator for 100 parts by weight of caprolactam, 0.5 part by weight of terephthalic acid, which is a dicarboxylic acid, and 25 ppm of phosphoric acid as a polymerization catalyst were put in a polymerization reactor for 6 hours at 270 ° C.

Thereafter, the internal pressure was removed and the reaction was carried out under reduced pressure of 250 Torr for 6 hours to prepare a polyamide 6 chip.

The extract content of the obtained chips was 9.8%, the relative viscosity (95% sulfuric acid, 25 ℃) was 3.24.

The relative viscosity after extraction was 3.36, and the amine end content and the carboxyl end content were 12 meq / kg and 65 meq / kg, respectively.

The extracted chip was blended with 0.3 parts by weight of copper iodide and 1.2 parts by weight of potassium iodide to prepare a dry chip, and a moisture content of 0.04% by weight was spun under conditions of a melting temperature of 280 ° C to prepare a yarn for tire cords of 1260 diameter. .

The obtained yarn had a strength of 10.36 g / De, an elongation of 23%, and a spinning workability of 93%.

The raw cord prepared by combining two strands of yarn was heat treated at 180 ° C. for 10 hours and was found to be 97%.

Example 3

1.2 parts by weight of water was used as an initiator in 100 parts by weight of caprolactam, and 0.5 parts by weight of terephthalic acid, which is a dicarboxylic acid, as a chain regulator was placed in a polymerization reactor and polymerized at 275 ° C for 8 hours.

Thereafter, the internal pressure was removed and the reaction was carried out at a reduced pressure of 250 Torr for 10 hours to prepare a polyamide 6 chip.

The extract content of the obtained chips was 10.2%, and the relative viscosity (95% sulfuric acid, 25 ° C) was 3.24. The relative viscosity after extraction was 3.38, and the amine end content and the carboxyl end content were 18 meq / kg and 77 meq / kg, respectively.

The extracted chip was blended with 0.3 parts by weight of copper iodide and 1.2 parts by weight of potassium iodide to prepare a dry chip, thereby preparing a yarn for tire cords having a moisture content of 0.04% by weight and a melting temperature of 280 ° C for 1260 deniers.

The obtained yarn had a strength of 10.32 g / De, an elongation of 24%, and a spinning workability of 89%.

The raw cord prepared by combining two strands of yarn was heated at 180 ° C. for 10 hours, and the strong retention rate was 90%.

Comparative Example 2

1.2 parts by weight of water was used as an initiator in the same manner as in Comparative Example 1, 25 ppm of phosphoric acid as a polymerization catalyst was placed in a polymerization reactor, and polymerization was carried out at 275 ° C for 8 hours.

After removing the internal pressure and reacted for 5 hours under reduced pressure of 250 torr to prepare a polyamide 6 chip.

The extract content of the obtained chips was 11.1%, the relative viscosity (95% sulfuric acid, 25 ℃) was 3.23. The relative viscosity after extraction was 3.40, and the amine end content and carboxyl end content were 38meq / kg and 37meq / kg, respectively.

The spinning was carried out in the same manner as in Comparative Example 2 and the workability and the strong retention were 62% and 77%, respectively.

<Table 1>

Example 1 Comparative Example 1 Example 2 Example 3 Comparative Example 2 Initiator (wt%) Water 2.0 ← 2.0 ← 2.0 ← 1.2 ← 1.2 Chain conditioner (% by weight) TPA0.20 - TPA0.50 TPA0.50 - Polymerization catalyst (ppm) - - Phosphoric Acid 25 - Phosphoric Acid 25 (Step 1) Temperature (℃) Polymerization Time (hrs) 2708 2759 2706 2758 2758 (Step 2) Vacuum polymerization time (hrs) 2506 → 4 → 6 → 10 → 4 Relative Viscosity (RV) 3.03 3.03 3.24 3.24 3.23 Extract (wt%) 10.8 11.4 9.8 10.2 11.1 After extraction Relative Viscosity (RV) 3.31 3.28 3.36 3.38 3.40 Amine end 24 40 12 18 34 Carboxyl terminus 59 40 68 77 30 After spinning Relative Viscosity (RV) 3.39 3.46 3.42 3.50 3.55 Strength (g / De) 9.71 9.16 10.36 10.32 9.26 Elongation (%) 24 23 23 24 21 Workability(%) 90.3 68.0 93.0 90.1 62.0 Strong retention rate (%) 93 88 97 90 77

Note 1 The end content is meq / kg.

2. The relative viscosity (RV) of polyamide and filament is 95% of sulfuric acid at 25 ℃.

Measured at a concentration of 1 g per ml.

3. Strength retention rate is the retention rate of strength before and after heat treatment of raw cord prepared by combining 2 strands of yarn at 180 ℃ for 10 hours.

As shown in Table 1, the embodiment shows a higher strength and improved strength retention than the prior art without deteriorating the degree of polymerization, which is stable due to the combination of dicarboxylic acid and polyamide chain in the external environment change due to heat treatment. It has little change in physical properties and shows excellent heat resistance.

In addition, the use of phosphoric acid as a polymerization catalyst together with the addition of dicarboxylic acid as a chain regulator can produce a high degree of polymerization of polyamide, and it has been shown to have higher strength, heat resistance and excellent workability.

In the present invention, since the amine content of the dried chip is 30 meq / kg or less and the total terminal content is 100 meq / kg or less, the polyamide is prevented from being denatured due to the post-polymerization reaction at a high temperature, thereby having high strength characteristics and excellent thermal stability. Industrial polyamide 6 yarn of polymerization degree can be manufactured.

Industrial polyamide 6 is suitable for the manufacture of filament yarn for tire cords requiring high strength.

Moreover, this invention is excellent in workability compared with the conventional method.

Claims (4)

In the first step (VK), a prepolymer was prepared by melt-condensing a mixture made by mixing 0.1 to 5% by weight of water and 0.1 to 1.0% by weight of dicarboxylic acid to caprolactam and caprolactam. In step 2 (VS), the prepolymer is water-removed under reduced pressure to polycondensate the amine end content to 30 meq / kg or less and the total terminal content to 100 meq / kg or less. Manufacturing method of industrial company. The method according to claim 1, wherein the prepolymer is prepared by adding 5 to 100 ppm of one selected from phosphoric acid, phosphorous acid, or hypophosphoric acid as a polymerization catalyst. The method for producing a high strength polyamide 6 industrial company having excellent heat resistance according to claim 1, wherein a copper compound and a halogenated calcium compound are used as heat-resistant agents during melt spinning. The method according to claim 1, wherein the polymerization catalyst is added before or during the polymerization.