JPS58132115A - Production of polyester multifilament with improved chemical stability - Google Patents

Abstract

PURPOSE:N,N'-Bis-(2,6-diisopropylphenyl)carbodiimide is added to polyester and the mixture is subjected to melt spinning to produce the titled multifilament yarn used in rubber reinforcement without discoloration. CONSTITUTION:A polyester containing more than 90mol% of polyethylene terephthalate is combined with 0.1-2wt% of N,N'-bis-(2,6-diisopropylphenyl)carbodiimide to reduce the amount of terminal carboxyl groups to a level lower than 20eq/10<6> grams, then subjected to melt spinning at a temperature lower than 310 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing polyester multifilaments with improved chemical stability. More specifically, the present invention relates to a method for producing polyester multifilament, which has improved chemical stability such as hydrolysis resistance and amine decomposition resistance, and is particularly suitable for rubber reinforcement.

Polyester multifilament has good dimensional stability and high initial modulus, so it is widely used as an industrial leaf material, especially for reinforcing rubber such as tire cords. There is a drawback that hydrolysis and amine decomposition of polyester multifilament are accelerated. The cause of such decomposition reactions is the terminal carboxyl groups present in polyester multifilament, and it is known that the amount of carboxyl terminal groups present is directly related to the magnitude of the decomposition reaction. In order to suppress the chemical properties and amine decomposability to below a nearly satisfactory level, it is necessary to reduce the amount of carboxyl end groups to 10 eq/1069 or less, and to obtain even more satisfactory results, /! It is more desirable that eqI be 10"9 or less, particularly 10@Q/10"g or less.

It is known that using a carbodiimide compound is effective as one method for reducing the amount of carboxyl terminal groups in a polyester multifilament. However, although carbodiimide compounds have the effect of reducing the amount of carpyl terminal groups in ester multifilaments, they have not been put to practical use industrially. According to the studies of the present inventors, the reason for this is considered to be due to the following points.

(2) Since the reactivity between the carbodiimide compound and the carboxyl terminal group is poor, it is necessary to add a large amount of the carbodiimide compound, which is economically disadvantageous.

■ If the carbodiimide compound remains unreacted and exists in the polyester multifilament, the polyester multifilament will become colored and its commercial value will decrease.

Otherwise, the physical properties (eg, strength) of the multifilament are reduced.

Despite the reduction in the amount of no-carboxyl end groups, chemical stability is not improved.

There are other problems.

In particular, the problem (2) caused by the residual unreacted carbodiimide compound is the biggest reason why it is difficult to industrially provide polyester multifilament with improved chemical stability using carbodiimide compounds.

As a way to solve these problems, Tokukosho! J-
No. 909/A method of publication disclosure was proposed.

In this method, by adding a carbodiimide compound in an amount equivalent to the amount of carboxyl end groups of the polyester used and the amount of carboxyl end groups generated during extrusion, it is possible to avoid substantially containing unreacted carbodiimide compounds. This is a distinctive method.

However, according to studies by the present inventors, it is difficult to eliminate unreacted carbodiimide compounds even with this method, and the problem caused by the presence of unreacted substances has not been solved. Moreover, it has become clear that this method cannot reach the amount of carboxyl terminal groups of less than 10 eqI10''9 required to exhibit excellent chemical stability. In this case, the obtained polyester multifilament was colored yellow and had poor commercial value.

Therefore, there is still no known method for producing industrially practical polyester multifilament having excellent chemical stability using a carbodiimide compound.

An object of the present invention is to provide a method that solves the above-mentioned problems and makes it possible to industrially produce polyester multifilaments with improved chemical stability.

As a result of intensive research aimed at achieving this objective, the present inventors have found that, by selecting a specific carbodiimide from among a large number of carbodiimide compounds, adding it, and melt-spinning it, the above-mentioned conventional technology can be improved. The problem was solved at once, and the present invention was completed by discovering that it is possible to industrially produce polyester multifilament with improved chemical stability without the hindrance, despite the presence of unreacted substances. reached.

That is, in the present invention, when melt-spinning polyester consisting of 90 mol% or more of polyethylene terephthalate,
By adding N,N'-bis-(2゜6-diitubrobylphenyl)-carbodiimide to the polyester, the amount of carboxyl terminal groups in the polyester can be reduced by 10%.
*q//C! DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in detail below.

The polyester in the present invention has a copolymerization component of
Polyethylene terephthalate is essentially polyethylene terephthalate, with less than 90 moles of ethylene terephthalate, and is obtained by well-known polymerization methods such as transesterification, direct esterification, and BHET. The intrinsic viscosity of the polyester measured by a conventional method is preferably 0.10 or more, which may contain additives used in
Among industrial uses, when it is necessary to increase the strength for rubber reinforcement, those with a relatively high degree of polymerization and an intrinsic viscosity of atto or higher are used. The i-lyester used is PO
HL Method CAnal, Chenb, 244/Al
The amount of carboxyl terminal groups measured by
-CoOaq/ / O”9.

It goes without saying that if the amount of carboxyl end groups in the polyester is small, a polyester multifilament with a low amount of carboxyl end groups can be obtained with a small amount of the carbodiimide compound used.

However, when such polyester is melt-spun without adding carbodiimide, the number of carboxyl groups increases due to thermal decomposition of the polyester, and the amount of carboxyl end groups in the resulting polyester multifilament is J □-j
Oeq/ / O"Q, and only filaments with poor chemical stability can be obtained. The amount of carboxyl terminal groups in commercially available industrial polyester fibers is approximately at this level.

In the present invention, among a large number of carbodiimide compounds, N,
N'-bis=(ko, 4-shiitsubu 4biru 7enyl)-
A major feature lies in the selection of lupodiimide. N
, N'-bis-(,2,G-diisopropylphenyl)
- When using carbodiimide, it is possible to reduce the amount of carboxyl terminal groups, and even if unreacted substances of this compound are present in the polyester multifilament, there will be no coloring or deterioration of physical properties, and the amount of terminal carboxyl groups can be reduced. Sufficient chemical stability improvement with a decrease in i
+J ability, which is a totally unexpected effect. The reason why only this carbodiimide exhibits uniquely stable properties despite the presence of unreacted substances compared to other carbodiimide compounds is not clear, but according to the present inventors' estimation, This is thought to be due to the fact that the three-dimensional structure of the molecules constituting this compound and the physical properties such as boiling point and decomposition temperature are most suitable for the field of the present invention.

N,N'-his-(λ,6-diitubrobylphenyl)
- The amount of carbodiimide added to the polyester must be such that the amount of carxyl end groups in the polyester multifilament is less than 9.

The specific amount added is determined by the relationship with the amount of carboxyl end groups of the polyester used, but it is usually Ql ~ Co weight attack,
Preferably it is a3 to 71 weight range.

When using the N,N-bis-(λ,6-diitupropylphenyl)-carbodiimide of the present invention, Japanese Patent Publication No. 3! -9
As shown in Publication No. 07, it is not necessary to add an amount equivalent to the additive amount, and it is also possible to add an excess amount, so that the amount of carboxyl terminal groups is less than 10 eq//♂q, and even less than jeq//
It became possible to obtain a polyester multifilament with an extremely small number of less than ♂7.

It is also effective to simultaneously include a small amount of a known reaction catalyst such as a phosphorus compound in order to improve the reactivity with the carboxyl terminal group.

The method of adding carbodiimide during melt spinning is not particularly limited as long as it can be sufficiently melt-mixed with the polyester and retained for 2 to 70 minutes, which is safe for reaction with carboxyl end groups. . In one embodiment, when chipped polyester is melt-spun using a known extruder, implementation P1 can be carried out by continuously adding carbodiimide to the chip supply port of the extruder while being measured. In addition, in the case of direct spinning in which the fibers are spun continuously after polymerization without being made into chips, it is possible to add them in the same way from after the completion of polymerization to the final metering pump.

Melt spinning is carried out by weighing the molten polyester using a weighing pump and then extruding it from a spinneret in accordance with a conventional method.

The temperature of the polyester during spinning is usually above the melting point of the i+) ester and between 320"C and 320"C; Hereinafter, it is preferably carried out at 10 to 300°C.

The polyester extruded from the spinneret is cooled and solidified, and a finishing oil is applied thereto, and then it is wound up as an undrawn yarn or continuously drawn by a conventional method to form a polyester multifilament.

The amount of unreacted carbodiimide present in the polyester multifilament obtained by the production method of the present invention can be easily determined by a known extraction method using a carbodiimide solvent such as carbon tetrachloride, chloroform, or acetone, as described below. can be found.

According to the koji pickling method of the present invention, despite the presence of unreacted carbodiimide, yarn breakage during spinning and drawing is no longer a problem as in the case without the addition of carbodiimide. In addition, the obtained polyester multifilament has no coloring, has a small amount of carboxyl terminal groups of less than 0, and has extremely excellent chemical stability against hydrolysis, amine decomposition, etc. are doing.

The polyester multifilament obtained according to the present invention is
It exhibits excellent effects when used for rubber reinforcement, particularly for tire hoods, but is not limited thereto.

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

In addition, the numerical values in Examples were measured by the following method.

(1) Using a strength and elongation tensile tester, yarn length 23cIIL, tensile speed J
OcIIv conditions, temperature 25″C and humidity 10%
Measure in an atmosphere of

(2) Hydrolysis resistance (moisture heat resistance strong retention rate) Polyester multifilament was placed in an autoclave filled with water at a constant length and saturated in steam for 10 minutes. Untreated. When the strength of the polyester multifilament is To and the strength after treatment is T, the strength retention rate was determined by a soft method.

(3) Amine decomposition resistance (amine resistance strong retention rate) 27wt% ammonia water was charged into an autoclave, and 1
The method is the same as for hydrolysis resistance, except that the treatment is carried out at 10° C. for 30 minutes.

(4) Amount of unreacted carbodiimide: The weight W1 of about 109 polyester multifilaments that has been scoured and dried using a conventional method is weighed. Using chloroform as an extraction solvent, time extraction is performed by the known Soxhlet extraction method. The weight of the carbodiimide collected by evaporating the chloroform solution is measured, and the content of unreacted substances is calculated using the following formula.

Example 1 Intrinsic viscosity 0.6J, carboxyl terminal group amount 3j・q/1
cf9 polyethylene terephthalate chip 27j
Solid phase polymerization was carried out at ℃ for λ1 hour under reduced pressure, and the intrinsic viscosity Q
tjs carboxyl terminal group amount was set to 2Qeq/1069. This chip is spun using a known extruder at a temperature of 2
/9 at 92°C and residence time during extrusion of approximately 1 minute.
It was extruded from a spinneret with J spinning holes. At this time, insert N, N'-bis-(co,
6-diitupropylphenyl)-carbodiimide as the first
It was added continuously using a metering pump at the rate shown in the table. The yarn extruded from the spinneret is cooled by a conventional method, and after applying a finishing oil, it is drawn and heat-set in a known direct spinning/drawing device without being wound up to a length of 1000 d//
921 rubber reinforcing polyester multifilament.

Table 7 shows the physical properties and hydrolysis resistance of the obtained polyester multifilament.

(Margin below) Table 7 Note l) This is a measure of hydrolysis resistance (the same applies below).

-) The value within 0 indicates the equivalent amount of carbodiimide added (the same applies hereinafter).

3) l: No coloring, slight coloring, 3 near iI color (
(According to sensory tests conducted by two inventors) (the same applies hereinafter) As is clear from Table 1, the production method of the present invention has a very low temperature during production, despite the presence of unreacted substances. Somehow, the carboxyl terminal group cap is 20＠q//(F
Those with a rating of 9 or less exhibit excellent hydrolysis resistance and no coloration is observed.

Example 2 Using ethylene terephthalate chips shown in Table 2 obtained by melt polymerization and solid phase polymerization, N,N'-bis-(co,6-diitubrobylphenyl)- After adding lupodiimide, spinning and stretching were performed. The physical properties and amine decomposition resistance of the obtained polyester multifilament are shown in Table 1. As shown by the data in the #I table, the amount of carboxyl end groups increased despite the presence of unreacted substances. -Those with q/106Li or less exhibit excellent amine decomposition resistance and are not colored.

(Left below) Comparative Example According to the method disclosed in Japanese Patent Publication No. 5S-QO'YI, intrinsic viscosity ays, carboxyl terminal group amount 27 eq/10"
Using as much ethylene tere-7thaletate as possible, various carbodiimide compounds shown in Table 3 were added to the carboxyl end group of the tip (here, 27aq/10').
) and the amount of carboxyl terminal groups generated during extrusion of this chip (teq/10'9 in this example) and the equivalent amount (33 eq/1069 in this example) by the method in Example/ Added. Spinning temperature 290″C1
A polyester multifilament was obtained by spinning and drawing in the same manner as in Example 1, except that the residence time was 25 minutes. Table 3 shows the spinning conditions, properties and hydrolysis resistance of the polyester multifilament. The example of the present invention to be compared with this table is the fifth example from the top in No. liI of Example 1 (corresponding to the amount of carbodiimide added of 100 wt%).

As is clear from Table 3, when using a carbodiimide compound other than the present invention and adding it according to the method of Japanese Patent Publication No. 13-909/, unlike the example of the present invention, there were many unreacted substances, The hydrolysis resistance of the polyester multifilament was also insufficient. Moreover, the obtained fibers were colored yellow.

Patent applicant Asahi Kasei Industries Co., Ltd. Representative patent attorney Toru Ouno Procedural amendment (
(Voluntary) December 27, 1980 Kazuo Wakasugi, Commissioner of the Japan Patent Office 3 Relationship with the case of the person making the amendment Patent applicant 4 Agent Address 3-7 Yotsuya and Shin Building 5, Shinjuku-ku, Tokyo
B6 Number of inventions increased by amendment None Contents of amendment (1) Applicant for the patent in the “Filament coloring” column of Table 1 on page 14 of the specification Toru Hoshino, Patent Attorney for Asahi Kasei Industries Co., Ltd.

Claims (1)

[Claims] (1) When melt-spinning a polyester consisting of 90 mol% or more of polyethylene terephthalate, by adding N,N'-bis-(λ,6-diitupropylphenyl)-carbodiimide to the polyester. , the amount of carboxyl end groups in the polyester is 20q//
069 A method for producing a polyester multifilament with improved chemical stability, characterized by: