JP3375419B2 - Polyamide composition with improved thermal yellowing - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyamide composition comprising polyhexamethylene adipamide and useful as a fiber and a resin material. More specifically, the present invention provides a fiber, an engineering resin, a film and the like made of polyhexamethylene adipamide in which yellowing discoloration in a heat treatment step is suppressed and the color tone is remarkably improved.

[0002]

BACKGROUND OF THE INVENTION Polycapramide (nylon 6) and polyhexamethylene adipamide (nylon 66) are generally manufactured as polyamide fibers and resin materials. Among them, nylon 66 has a high melting point and high heat resistance. Due to its excellent characteristics, it is very suitable for fibers for industrial materials such as engineering resins and tire cords.

On the other hand, however, it has a drawback that it tends to cause yellowing and coloring due to thermal oxidation during heating at a high temperature. Particularly for fibers for clothing, there is a step of heat-treating in the air atmosphere after knitting the fiber, and yellowing coloring occurs in this heat treatment step, resulting in a decrease in whiteness or a dull color even when dyed. There is a problem of deterioration of color tone such as no clear color.

In order to suppress oxidative deterioration during heat treatment, a resin material or a fiber such as a tire cord which does not have a problem in color tone,
A copper compound is generally added as a heat resistance stabilizer. However, although these methods are effective in preventing reduction in mechanical strength due to thermal oxidation, on the contrary, they tend to deteriorate in coloring and are not effective in improving color tone. To improve the color tone of polyamide, for example, JP-A-2-200
As disclosed in Japanese Patent Application Laid-Open No. 816, Japanese Patent Application Laid-Open No. 4-153315, Japanese Patent Application Laid-Open No. 4-202852, etc., it has been frequently performed to reduce the concentration of amino end groups as a polymer composition.

In these publications, it is believed that the yellowing coloring of polyamide fibers is accompanied by the modification of amino end groups, and in order to prevent this and improve the color tone, the amino end groups are positively blocked. Thus, it is common practice to reduce the concentration of amino end groups.

[0006]

However, these known methods are aimed at preventing light yellowing, cardboard yellowing, and NOx yellowing, and the yellowing coloring during heat treatment, which is the subject of the present invention, is considered. No effect, no effect. Moreover, as described in the known examples, these methods mainly target nylon 6, but in the case of nylon 66 (polyhexamethylene adipamide) targeted by the present invention, photoyellowing, cardboard Thermal yellowing rather than yellowing or NOx yellowing is a serious problem in practical use.

The present invention provides a polyhexamethylene adipamide composition having a markedly improved color tone, which is capable of suppressing yellowing and coloring even when subjected to high temperature heat treatment during polymerization, spinning / molding, and post-processing. It is the one we are trying to provide. As a means for preventing yellowing discoloration during heat treatment, a method of adding an antioxidant is used as disclosed in JP-A-51-1557. However, this method causes adverse effects such as discoloration due to decomposition of the antioxidant itself, exudation of the agent later due to poor compatibility with the polymer, and change in dyeability of the fiber. There are many.

[0008]

As a result of intensive studies by the present inventor, the thermal yellowing phenomenon associated with heat treatment has been described in JP-A No. 2-2.
It has been found that the modification reaction of the carboxyl terminal group is a dominant factor, rather than the modification of the amino terminal group as shown in Japanese Patent Publication No. 081616. Then, it was discovered that thermal yellowing can be suppressed by controlling the concentration of carboxyl end groups of the polymer to be below a certain amount.

The most convenient and effective method for reducing the concentration of carboxyl terminal groups is to add hexamethylenediamine, which is one component of the raw material, at the time of polymerization. However, at this time, the concentration of the carboxyl end group can be decreased, while the concentration of the amino end group is increased. This is completely contrary to the conventional belief that reducing the concentration of amino end groups is effective for improving the color tone of polyamide, and is a surprising finding.

However, as disclosed in Japanese Patent Publication No. 3-57966, it is not preferable to increase the concentration of amino end groups in polyhexamethylene adipamide, because the formation of branched by-products due to thermal decomposition of the polymer is remarkable. It is said that. In particular, problems such as frequent occurrence of yarn breakage during spinning due to viscosity unevenness and shortening of the cleaning cycle of the spinning machine, molding machine, etc. occur, and they cannot be used as they are.

Therefore, it is essential for the stabilization of the production process to prevent the formation of branched by-products due to the thermal decomposition of the polymer, which is the addition of an alkali metal compound as a heat stabilizer to the polymer. Made possible by that. As described above, the polyhexamethylene adipamide composition with improved yellowing at the time of heating was practically used for the first time by adjusting the concentration of the terminal group of the polymer and combining the techniques of applying the thermal decomposition stabilizer. The technique of the present invention for stable production has been completed.

That is, the present invention provides a polyamide composition having improved heat yellowing, which is characterized in that polyhexamethylene adipamide simultaneously satisfies the following (1) to (3). (1) 30 ≦ [NH ₂ ] + [COOH] ≦ 200 (2) [COOH] ≦ 60 (3) 0.005 to 0.5 of alkali metal compound to polymer
Contains by weight%. (However, [NH ₂ ] is the concentration of the amino end group of the polymer, [COO
[H] represents the concentration of the carboxyl end group, and is expressed as a unit in milliequivalents per 1 kg of the polymer. ) The present invention will be specifically described below. The polyhexamethylene adipamide used in the present invention is mainly composed of a repeating unit represented by the following formula.

[0013]

[Chemical 1]

It may contain 20% by weight or less of other amide-forming units. These other amide-forming units include:
Aliphatic dicarboxylic acids such as sebacic acid and dodecanoic acid; aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid; aliphatic diamines such as decamethylenediamine; aromatic diamines such as metaxylylenediamine; and 6-aminocapron Ω-amino acids such as acids; lactams such as ε-caprolactam are used. It is also possible to use a mixture of the above polyhexamethylene adipamide with 20% by weight or less of another polyamide such as polycapramide and polyhexamethylene sebacamide.

The polyhexamethylene adipamide used in the present invention is produced by ordinary melt polycondensation, and may be a batch polymerization system or a continuous polymerization system. For example, as a batch polymerization method, a 50 wt% aqueous solution of hexamethylene diammonium adipate (AH salt), which is a salt of hexamethylene adipamide and adipic acid, is mixed with additives such as a polymerization degree adjusting agent and charged in a concentration tank. Heat to about 150 ℃ and concentrate to a concentration of about 80% by weight. This concentrated liquid is supplied to the polymerization tank and heating is continued. At this time, the condensation water is removed while controlling the pressure in the polymerization tank to about 18 kg / cm ² with a pressure control valve, and the internal temperature is raised to 250 ° C. Next, while continuing heating, the pressure in the polymerization tank is gradually released to return to normal pressure, the internal temperature is raised to 280 ° C. and maintained for several tens of minutes to complete polycondensation. The produced polymer melt can be pressurized with an inert gas, extruded from a discharge nozzle, and cooled to form pellet chips.

Further, as a continuous polymerization method, Brit.
54 (1949) and Adv. Poly. Tech., 6 , (3), 267 (1986) and the like. Further, the polymer chip obtained by the above-mentioned polymerization method, 20
The polymerization degree may be further increased by heating at a temperature lower by -80 ° C in a vacuum or in an inert gas to carry out solid-state polymerization.

In these general polymerization methods, in order to regulate the carboxyl terminal group concentration to a predetermined amount or less, for example, hexamethylenediamine, which is one component of the raw material, is added in excess when the raw material is charged to carry out the polymerization. , The most common, simple and effective. It can also be achieved by adding this hexamethylenediamine during the polymerization. Further, it is also possible to add another diamine substance or a monoamine substance such as hexylamine at the time of charging the raw materials or during the polymerization to block the carboxyl end group.

When the amino terminal group concentration and the carboxyl terminal group concentration of the polymer are expressed as [NH ₂ ] and [COOH] (units are expressed in milliequivalents per kg of polymer),
These values are defined as follows: 70 ≤ [NH ₂ ] + [COOH] ≤ 200
It is necessary to be. If the amount exceeds 200 meq / kg polymer, the molecular weight is too low and the mechanical strength is insufficient, so that a practical fiber or resin cannot be obtained. Also,
If it is less than 70 meq / kg polymer, the melt viscosity is high because the molecular weight is too high, and melt molding such as spinning or injection becomes difficult. A more preferable range for practical use is 80 ≦ [NH ₂ ]
+ [COOH] ≦ 175.

Further, it suppresses yellowing coloring during heating,
To improve the color tone, [COOH] ≤
It should be 60. If it exceeds 60 meq / kg of polymer, yellowing due to heating will occur greatly and the color tone will deteriorate, which is not possible. At this time, in order to prevent the generation of branched by-products due to thermal decomposition of the polymer and stabilize the manufacturing process, an alkali metal compound as a heat stabilizer is added to the polymer in an amount of 0.005 to
It is necessary to add 0.5% by weight. Examples of the alkali metal compound include hydroxides of alkali metals such as sodium hydroxide and potassium hydroxide, alkali metal salts of inorganic acids such as sodium sulfate and potassium nitrate, alkali metal salts of organic acids such as sodium adipate and potassium acetate. Is effective, and particularly, an alkali salt of dicarboxylic acid shows an excellent effect.

The amount of these alkali metal compounds is 0.005 to 0.5% by weight based on the polymer. If the addition amount is less than 0.005% by weight, the effect of suppressing thermal decomposition is small and unsuitable. 0.5
If it exceeds 5% by weight, adverse effects such as polymerization inhibition and clogging of the spinning filter occur, which is also unsuitable. As an addition method, it may be added when the raw materials are charged, or may be added to the polymer at an arbitrary time in the polymerization step.

In the polymer of the present invention, other additives such as heat stabilizers such as copper acetate, copper chloride, copper iodide and mercaptobenzimidazole; light stabilizers such as manganese acetate and manganese hypophosphite. A thickener such as phosphoric acid, phenylphosphonic acid or sodium pyrophosphate; a delusterant such as titanium dioxide, silicon dioxide or kaolin; an activator such as calcium stearate or a plasticizer. The polyhexamethylene adipamide thus obtained can also be directly supplied in a molten state to spinning and molding, and once made into chips, remelted by using a screw type extruder or the like. It is also possible to supply it for spinning or molding. Fibers can be obtained by discharging the molten polymer from the spinneret and winding it with a winder. Also,
Engineering resins and films can be obtained by extrusion molding, injection molding, blow molding and the like.

[0022]

EXAMPLES The present invention will be described in detail below with reference to actual examples. First, the implementation method and measurement method in the examples will be described. Relative viscosity of polymer chips formic acid Polymer chips obtained by polymerization were dissolved in 90% by weight formic acid solution to a concentration of 8.4% by weight.
Relative viscosity in ° C. Polyhexamethylene adipamide chips obtained by spin polymerization were melted at a temperature of 300 ° C. with a screw type extruder after humidity control, and 39 g from a spinneret having nozzle holes of 24 holes.
The ink was discharged at a rate of / minute. The discharged polymer was cooled with cooling air to form fibers, and after applying an oil agent, it was wound at a speed of 5000 m / min through a godet roll to wind a yarn of 70 denier / 24 filament. The refined yarn was immersed in 100 times the weight of a nonionic surfactant having a concentration of 2 g / liter and washed at 60 ° C. for 30 minutes to remove the oil agent.

After the yarn spun by the method of amino terminal group concentration and carboxyl terminal group concentration was scoured by the method, "Polymer Analysis Handbook" edited by Japan Society for Analytical Chemistry (Asakura Shoten)
Analysis was performed using the method on page 323. Using a yarn spun by the method of heat yellowing, a tubular knitted fabric was prepared by a single-knitting machine with a diameter of 3.75 inches, and refined by the method. After this knitted fabric was left to dry, it was placed in a hot air oven and heat-treated at 190 ° C. for 5 minutes in an air atmosphere. The yellowness YI was obtained by measuring the color of this knitted fabric using a spectral colorimeter SZ-Σ90 manufactured by Nippon Denshoku Industries Co., Ltd. When spinning is continued by the cleaning cycle method, deterioration products that are thought to be caused by thermal decomposition of the polymer adhere to the nozzle hole outlet of the spinneret, causing the discharged polymer on the spinneret surface to bend and eventually progress to thread breakage. To do. Therefore, in order to continue spinning stably, it is necessary to periodically wipe the spinneret surface with a metal spatula or the like to remove the deteriorated material and clean it. The cleaning cycle of the spinneret by wiping was recorded for stable spinning without causing such yarn breakage, and the thermal decomposability of the polymer was evaluated.

[0024]

Example 1 Raw materials were charged in the following proportions in an autoclave having a capacity of 400 liters to carry out batch polymerization. Of hexamethylene diammonium adipate (AH salt)
50% by weight aqueous solution 280 liters Hexamethylenediamine 14% by weight aqueous solution 4.4 liters Titanium oxide 8% by weight aqueous solution 0.4 liters Disodium adipate 0.104 kg Charge the raw material aqueous solution first in a concentrating tank at a temperature of 150 ° C. It was heated for an hour and concentrated to 80% by weight. Next, it was sent to a polymerization tank, and while continuing heating, the condensation water was removed while controlling the internal pressure to 17.5 kg / cm ² , the temperature was raised to 250 ° C., and the polymerization was allowed to proceed for 1.5 hours. Next, raise the internal temperature to 280 ° C and gradually return to normal pressure over a period of 1 hour.
Hold for minutes. Then, the polymer was pressurized with nitrogen gas, discharged, and cooled with water to obtain 130 kg of chips.

Relative viscosity of formic acid of this polymerized polymer chip,
In addition, the cleaning cycle of the spinneret when spinning was performed using chips, the amino and carboxyl terminal group concentrations of the obtained yarn, and the yellowing of the knitted fabric during heat treatment were evaluated. The results are summarized in Table 1.

[0026]

Example 2 A polymer chip was prepared by the same polymerization method as in Example 1, with the raw material charging ratio set as follows. AH salt 50% by weight aqueous solution 280 liters Hexamethylenediamine 14% by weight aqueous solution 2.4 liters Titanium oxide 8% by weight aqueous solution 0.4 liters Disodium adipate 0.065 kg This polymerized polymer chip relative viscosity of formic acid Cleaning cycle of the spinneret when spinning is performed using
Further, the obtained yarn was evaluated for amino and carboxyl end group concentrations and yellowing in the heat treatment of the knitted fabric. The results are summarized in Table 1.

[0027]

[Comparative Example 1] Polymer chips were prepared by the same polymerization method as in Example 1 except that the raw material charging ratio was set as follows. 280 liters of 50% by weight aqueous solution of AH salt 4.4 liters of 14% by weight aqueous solution of hexamethylenediamine 0.4 liters of 8% by weight aqueous solution of titanium oxide 0.4% relative viscosity of formic acid of this polymerized polymer tip, and when spinning was performed using the tip Spinneret cleaning cycle,
Further, the obtained yarn was evaluated for amino and carboxyl end group concentrations and yellowing in the heat treatment of the knitted fabric. The results are summarized in Table 1.

[0028]

[Comparative Example 2] Polymer chips were prepared by the same polymerization method as in Example 1 while setting the ratio of raw material charging as follows. 280 liters of 50% by weight aqueous solution of AH salt, 2.4 liters of 14% by weight aqueous solution of hexamethylenediamine, 0.4 liters of 8% by weight aqueous solution of titanium oxide. Relative viscosity of formic acid of this polymerized polymer chip, and when spinning was performed using the chips. Spinneret cleaning cycle,
Further, the obtained yarn was evaluated for amino and carboxyl end group concentrations and yellowing in the heat treatment of the knitted fabric. The results are summarized in Table 1.

[0029]

[Comparative Example 3] Polymer chips were prepared by the same polymerization method as in Example 1 except that the raw material charging ratio was set as follows. 280 liters of 50 wt% aqueous solution of AH salt, 0.4 liter of 8 wt% aqueous solution of titanium oxide Relative viscosity of formic acid of this polymerized polymer chip, and cleaning cycle of spinneret when spinning is performed using the chips,
Further, the obtained yarn was evaluated for amino and carboxyl end group concentrations and yellowing in the heat treatment of the knitted fabric. The results are summarized in Table 1.

[0030]

[Comparative Example 4] Polymer chips were prepared by the same polymerization method as in Example 1 except that the raw material charging ratio was set as follows. AH salt 50% by weight aqueous solution 280 liters Adipic acid 4% by weight aqueous solution 11.7 liters Titanium oxide 8% by weight aqueous solution 0.4 liters Relative viscosity of formic acid of this polymerized polymer chip, and when spinning was performed using the chips. Cleaning cycle of the spinneret,
Further, the obtained yarn was evaluated for amino and carboxyl end group concentrations and yellowing in the heat treatment of the knitted fabric. The results are summarized in Table 1.

[0031]

Example 3 A polymer chip was prepared by the same polymerization method as in Example 1, with the raw material charging ratio set as follows. AH salt 50% by weight aqueous solution 280 liters Hexamethylenediamine 14% by weight aqueous solution 4.4 liters Titanium oxide 8% by weight aqueous solution 0.4 liters Disodium adipate 0.065 kg The obtained polymer chip is a tumbler type with a volume of 400 liters. The mixture was placed in a solid-state polymerization vessel and heated at 180 ° C. for 20 hours while flowing nitrogen gas to carry out solid-state polymerization to increase the degree of polymerization. Relative viscosity of formic acid of the polymerized polymer chips, cleaning cycle of the spinneret when spinning was performed using the chips, amino and carboxyl end group concentrations of the resulting yarns, and evaluation of yellowing during heat treatment of the knitted fabric. Was carried out. The results are summarized in Table 1.

[0032]

Example 4 Polymer chips and solid phase polymerization were carried out in the same manner as in Example 3 by setting the ratio of raw material charging as follows, to prepare polymer chips. AH salt 50% by weight aqueous solution 280 liters Hexamethylenediamine 14% by weight aqueous solution 2.4 liters Titanium oxide 8% by weight aqueous solution 0.4 liters Disodium adipate 0.039 kg This polymerized polymer chip relative viscosity of formic acid Cleaning cycle of the spinneret when spinning is performed using
Further, the obtained yarn was evaluated for amino and carboxyl end group concentrations and yellowing in the heat treatment of the knitted fabric. The results are summarized in Table 1.

[0033]

[Comparative Example 5] Polymer chips were prepared by carrying out polymerization and solid phase polymerization in the same manner as in Example 3, with the proportions of the raw material charges set as follows. AH salt 50% by weight aqueous solution 280 liters Adipic acid 4% by weight aqueous solution 11.7 liters Titanium oxide 8% by weight aqueous solution 0.4 liters Formic acid relative viscosity of this polymerized polymer chip, and when spinning was performed using the chips. Cleaning cycle of the spinneret,
Further, the obtained yarn was evaluated for amino and carboxyl end group concentrations and yellowing in the heat treatment of the knitted fabric. The results are summarized in Table 1.

As shown in Table 1, the values of the amino and carboxyl end group concentrations were set under the conditions of the present invention.
Further, only when a predetermined amount of the alkali metal compound is added, thermal yellowing is greatly improved, thermal decomposition of the polymer is also suppressed, and the cleaning cycle of the spinneret can be maintained for a long time to obtain a practical fiber. There is.

[0035]

[Table 1]

[0036]

INDUSTRIAL APPLICABILITY The composition of the specific polyhexamethylene adipamide of the present invention, such as fiber and resin material, suppresses thermal decomposition of the polymer in a molten state during polymerization, spinning or molding. Therefore, stable production is possible, and even when subjected to a high temperature heat treatment during the post-processing, the yellowing coloring is remarkably reduced and the color tone is significantly improved.

Continuation of front page (51) Int.Cl. ⁷ Identification code FI // D01F 6/90 301 D01F 6/90 301

Claims (3)

(57) [Claims] 1. A polyamide composition with improved thermal yellowing, characterized in that polyhexamethylene adipamide simultaneously satisfies the following (1) to (3). (1) 70 ≦ [NH ₂ ] + [COOH] ≦ 200 (2) [COOH] ≦ 60 (3) 0.005 to 0.5 of alkali metal compound to polymer
Contains by weight%. (However, [ NH ₂ ] is the concentration of the polymer amino end group,
[OOH] represents the concentration of the carboxyl end group, and is expressed in milliequivalents per 1 kg of the polymer as a unit. ) 2. The polyamide composition according to claim 1, wherein 80 ≦ [NH ₂ ] + [COOH] ≦ 175. 3. The polyamide composition according to claim 1, wherein the alkali metal compound is an alkali salt of dicarboxylic acid.