JP2948006B2 - Polyethylene naphthalate fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyethylene naphthalate fiber having improved heat resistance, particularly resistance to moist heat, and more particularly to a polyethylene naphthalate fiber suitable as a reinforcing fiber for use in industrial materials such as tire cords, belts and hoses. About.

[0002]

2. Description of the Related Art Polyethylene terephthalate fibers are widely used as reinforcing fibers for rubber materials such as tire cords, belts, hoses, etc., but when encapsulated in rubber and exposed to high temperatures, water is absorbed by the water in the rubber. Undergoing disassembly,
The strength is greatly reduced, and the durability in rubber is not sufficient. For this reason, it has been proposed to use polyethylene naphthalate fibers having excellent hydrolysis resistance for rubber reinforcement. However, when polyethylene naphthalate fiber is used, although hydrolysis resistance is certainly improved in comparison with polyethylene terephthalate, a fiber suitable for industrial material use cannot be obtained by simply using it alone. For example,
No. 27639 discloses that hydrolysis resistance can be improved by forming a specific crystal structure having a peak at a Bragg reflection angle 2θ = 18.7 ° in a wide-angle X-ray diffraction intensity distribution curve. However, in this proposal,
Due to having a specific crystal structure, the strength level of the obtained drawn yarn is limited to about 5 to 6 g / de, and although the strength level is sufficient for a papermaking canvas which is the object of the proposal, rubber It is insufficient as a reinforcing fiber for materials and the like. On the other hand, in the case of polyethylene terephthalate fiber, it is known to reduce the terminal carboxyl group concentration as a measure for improving the hydrolysis resistance.
JP-A-15604 and JP-B-3-47326 propose measures to reduce the carboxyl group concentration of polyethylene terephthalate fiber by adding a specific carbodiimide compound during spinning.

However, in the case of polyethylene naphthalate fiber, hydrolysis resistance may be originally good,
Also, there is no specific proposal for further improvement of the hydrolysis resistance, other than the aforementioned proposal for papermaking kanbans, because it has not yet been sufficiently used in the rubber material field. Is the current situation.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a polyethylene naphthalate fiber which exhibits extremely excellent hydrolysis resistance and is suitable as a reinforcing fiber for rubber materials such as tire cords, belts and hoses. And

[0005]

SUMMARY OF THE INVENTION The object of the present invention is to provide an ink composition having an intrinsic viscosity of 0.70 or more and a terminal carboxyl group content of 40 e.
q / 10 ⁶ g or less of a polyester containing 90 mol% or more of ethylene-2,6-naphthalate units,
N'-bis (2,6-diisopropylphenyl) carbodiimide in an amount of 0.5 to 2.5% by weight based on polyester
This is achieved by a polyethylene naphthalate fiber obtained by adding and melt-spinning, wherein the polyethylene naphthalate fiber satisfies the following at the same time. 0.70 ≦ intrinsic viscosity IV ≦ 1.00 terminal carboxyl group amount CV ≦ 15 eq / 10 ⁶ g strength ST ≧ 9.0 g / de density d ≧ 1.362 g / cm ³

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The polyethylene naphthalate referred to in the present invention comprises 90 units of ethylene-2,6-naphthalate.
It is sufficient if it contains at least 10 mol%, and a copolymer polyester containing an appropriate third component at a ratio of 10 mol% or less may be used. Generally, polyethylene-2,6-naphthalate is synthesized by subjecting naphthalene-2,6-dicarboxylic acid or an ester-forming derivative thereof to polycondensation with ethylene glycol under appropriate reaction conditions in the presence of a catalyst. At this time, one or more appropriate third or third tertiary amines may be added before the completion of the polymerization of polyethylene-2,6-naphthalate.
When the components are added, a copolymerized polyester is synthesized.

Suitable third components include (a) compounds having two ester-forming functional groups; for example, oxalic acid,
Aliphatic dicarboxylic acids such as succinic acid, adipic acid, sebacic acid and dimer acid; alicyclic dicarboxylic acids such as cyclopropanedicarboxylic acid, cyclobutanedicarboxylic acid and hexahydroterephthalic acid; phthalic acid, isophthalic acid, naphthalene-2,7 -Aromatic dicarboxylic acids such as dicarboxylic acid and diphenyl dicarboxylic acid; carboxylic acids such as diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenoxyethane dicarboxylic acid, and sodium 3,5-dicarboxybenzene sulfonate; glycolic acid, p-oxy Oxycarboxylic acids such as benzoic acid and p-oxyethoxybenzoic acid; propylene glycol, trimethylene glycol, diethylene glycol, tetramethylene glycol, hexamethylene glycol, neopentylene glycol Le, p- xylylene glycol,
1,4-cyclohexanedimethanol, bisphenol A, p, p'-dihydroxydiphenylsulfone,
4-bis (β-hydroxyethoxy) benzene, 2,2
Oxy compounds such as bis (p-β-hydroxyethoxyphenyl) propane and polyalkylene glycol; functional derivatives thereof; high degrees of polymerization derived from the carboxylic acids, oxycarboxylic acids, oxy compounds or functional derivatives thereof Examples of the compound include (b) a compound having one ester-forming functional group, for example, benzoic acid, benzyloxybenzoic acid, and methoxypolyalkylene glycol.

Further, (c) a compound having three or more ester-forming functional groups, for example, glycerin, pentaerythritol, trimethylolpropane and the like can be used within a range where the polymer is substantially linear. .

It goes without saying that the polyester may contain a matting agent such as titanium dioxide and a stabilizer such as phosphoric acid, phosphorous acid and esters thereof.

[0010] In the polyethylene naphthalate fiber of the present invention, the drawn yarn has an intrinsic viscosity of 0.7 to 1.0. The intrinsic viscosity referred to in the present invention is a value obtained by dissolving a polymer or an undrawn yarn in a mixed solvent of phenol and orthodichlorobenzene (volume ratio: 6: 4) and measuring the viscosity at 35 ° C. If the intrinsic viscosity is less than 0.70, not only the hydrolysis resistance is reduced, but also a high-strength, high-toughness yarn-like fiber cannot be obtained, which is unsuitable as a reinforcing fiber. On the other hand, a fiber having an intrinsic viscosity of more than 1.0 is liable to cause the spinning process to be defective, which is not desirable in practical use.

The amount of terminal carboxyl groups is 15 eq /
It is necessary to be 10 ⁶ g or less, and if it exceeds 15 eq / 10 ⁶ g, the hydrolysis resistance becomes insufficient.

Further, the strength must be 9 g / de or more, and the fiber density must be 1.362 g / cm ³ or more. If either one is less than the above, the hydrolysis resistance becomes insufficient.

As described above, in the present invention, in the polyethylene naphthalate fiber having a single fiber denier of less than 8 denier, the intrinsic viscosity is 0.70 to 1.0 and the terminal carboxyl group content is 15 eq / 10 ⁶ g or less. No fiber having extremely excellent hydrolysis resistance for the first time by having a high degree of orientation of 9.0 g / de or more and a fiber structure with advanced crystallization of a density of 1.362 g / cm ³ or more Was obtained.

When the polyethylene naphthalate fiber of the present invention is used as a rubber reinforcing fiber, the durability of the polyethylene naphthalate fiber is not limited to the conventional polyethylene terephthalate fiber, but also compared with the conventional high-strength polyethylene naphthalate fiber. Is remarkably excellent, and its industrial significance is great.

As a method for producing the polyethylene naphthalate fiber of the present invention, for example, the following method is exemplified.

That is, when a polyethylene naphthalate resin containing at least 90 mol% of ethylene-2,6-naphthalate units is melt-spun, an intrinsic viscosity of 0.7 or more and a carboxyl end group content of 40 eq / 10 ⁶ g or less are used. N, N'-bis (2,6-diisopropylphenyl)-
Carbodiimide is added in an amount of 0.5 to 2.5% by weight to obtain an undrawn polyethylene naphthalate yarn having a carboxyl end group content of 15 equivalents / 10 ⁶ g or less. And the density is 1.362 g / cm ³
The method of forming the above fibers is preferably employed.

Various methods have been proposed for adding a compound during melt spinning to reduce the amount of terminal carboxyl groups of the polyester resin. However, all of these methods mainly use polyethylene terephthalate, and as a compound to be added, an epoxy compound (for example, Japanese Patent Publication No. 44-27911), a cyclic carbonate or a carbodiimide compound (for example, Japanese Patent Publication No. 55-9091). ) Has been proposed. However, according to the study of the present inventors, in the case of polyethylene naphthalate which needs to have a melt spinning temperature of 310 ° C. or higher, the degree of polymerization of epoxy compounds and cyclic carbonates is greatly reduced,
They found that they could not be practically used due to vigorous foaming, and as a result of further investigation, when a specific monocarbodiimide compound was added, the terminal carboxyl groups were effectively reduced without reducing the degree of polymerization of polyethylene naphthalate. They found what could be done.

That is, since there is little thermal decomposition or side reaction during spinning and there is no decrease in the degree of polymerization of the polyethylene naphthalate polymer, in the present invention, N, N'-bis (2,6-diisopropylphenyl) is used as the monocarbodiimide compound. -Use carbodiimide. Incidentally, a polycarbodiimide compound such as a biscarbodiimide compound is used to rapidly increase the degree of polymerization of polyethylene naphthalate.
Kneading of the polyethylene naphthalate and the polycarbodiimide compound becomes difficult, which is not preferable.

As a method for adding the monocarbodiimide compound, a conventionally known method can be arbitrarily adopted. For example, a powder, a melt, or a solution dissolved in an inert solvent such as xylene or o-dichlorobenzene may be mixed with a resin chip or injected into the inlet of an extruder.

Next, the residence time of the monocarbodiimide compound and the resin in the spinning machine is from 2 minutes to 6 minutes after the resin temperature reaches 300 ° C. or higher, and the maximum temperature of the resin in the spinning is 330 minutes. It is preferable that the temperature is set to not more than ° C. 30
If the time after the temperature reaches 0 ° C. does not reach 2 minutes, the amount of terminal carboxyls does not decrease sufficiently. On the other hand, if the time exceeds 6 minutes, the monocarbodiimide compound itself is decomposed. It tends to be inferior. If the resin temperature during spinning does not reach 300 ° C., melt spinning cannot be performed stably, or even if it can be performed, only a weak yarn can be obtained. Conversely, if the temperature exceeds 330 ° C., the intrinsic viscosity of polyethylene naphthalate is greatly reduced and the monocarbodiimide compound is decomposed, so that sufficient strength and hydrolysis resistance tend not to be obtained.

The polyethylene naphthalate discharged from the spinneret is cooled and solidified to give a finishing oil, then wound up as an undrawn yarn, and then drawn by a so-called another drawing method, or continuously into the spinning process. The drawn yarn can be made into a drawn yarn by a direct drawing method in which an undrawn yarn is sent to a drawing step. The specific spinning and drawing method is not particularly limited, and a conventionally known method may be adopted, but the strength of the obtained drawn yarn is 9 g / de or more and the density is 1.362 g.
/ Cm ³ or more. As a preferred yarn-making method, a heating cylinder having an atmosphere temperature of 275 ° C. or more and a length of 20 cm or more is set directly below the spinneret, and the spinning speed is drawn at 1000 m / min or less to obtain an undrawn yarn first. Next, the first-stage stretching is performed at a magnification of 80% or more of the total stretching ratio, and then a fixed length or 3% between a heated roll and a non-heated roll at a temperature of 225 to 250 ° C.
The following limited shrinking and winding methods can be exemplified.

[0022]

The present invention will be described in more detail with reference to the following examples.
In addition, the measured value in an Example is based on the following method. (A) Strength and elongation: Measured in accordance with JIS L 1070. (A) Density: Measured by a density gradient tube method using carbon tetrachloride as a heavy liquid and n-heptane as a light liquid. (C) Terminal carboxyl group content: Mak by Conix
romolecularChemie 26,226
(1958), using a mixed solvent of m-cresol / xylene (volume ratio: 6/4) as a solvent,
Fiber was measured on undrawn yarn. (D) Moisture / heat resistance: The fiber was made to be in a relaxed state, and evaluated by a strength retention rate when left continuously in saturated steam at 120 ° C. for 20 days.

Example 1 Intrinsic viscosity 0.85, terminal carboxyl group content 28 eq / 1
0 ⁶ g of polyethylene-2,6-naphthalate chip and N, N'-bis (2,6-diisopropylphenyl) carbodiimide weight ratio of polyethylene-2,6-naphthalate / N, N'-bis (2,6 -Diisopropylphenyl) carbodiimide = 100 / 1.8 (50 equivalents of carbodiimide / 10 ⁶ g) and a solid-blended mixture was supplied to the extruder. The kneaded molten polymer was discharged from a die via a gear pump and a pack. The temperature of the spinning machine was 305 ° C. to 318 ° C. in the latter half of the extruder in which the polymer was melted, and the temperature until discharging from the spinneret was also 318 ° C. The time required for ejection during this time was about 4 minutes. After passing through a heating tube having a length of 350 cm and a length of 40 cm placed immediately below the base, the mixture was cooled and solidified with cooling air having a relative humidity of 65% and a temperature of 25 ° C over a length of 30 cm. An oil agent was applied to the cooled and solidified yarn with an oiling roller, and the yarn was wound at 200 m / min. The intrinsic viscosity of the undrawn yarn was 0.74, the amount of terminal carboxyl groups was 12 eq / 10 ⁶ g, and the single fiber fineness was 28 de.

Next, the undrawn yarn is pre-tensioned by 1%, and then subjected to first-stage drawing (magnification DRI) between a heating supply roll (FR) at 155 ° C. and a first-stage drawing roll (IR).
Then, the second stage stretching (stretching ratio 1.03 times) was performed between the first stage stretching roll and the second stage stretching roll (2R). Further, as a heat setting step, a 2% relaxation ratio (DR3) between 2R (heating) and a non-heating winding roll (WR).
, And was wound at 200 m / min.
In addition, some experiment Nos. In (6, 7), it was wound up without heat setting from the second-stage stretching roll which was not heated.
Table 1 shows the results. Table 1 also refers to the characteristics of commercially available polyethylene terephthalate fibers for tire yarns.
Shown in

[0025]

[Table 1]

Example 2 Experiment No. 1 of Example 1 1, except that the amount of N, N'-bis (2,6-diisopropylphenyl) carbodiimide was changed. Table 2 shows the results
Shown in

[0027]

[Table 2]

Comparative Example Intrinsic viscosity 0.70, terminal carboxyl group amount 40 equivalents / 1
0 ⁶ g using a polyethylene-2,6-naphthalate chip, spinning machines except that the maximum temperature was 315 ° C. The examples 1 Experiment No. Performed similarly to 1. At this time, the intrinsic viscosity of the undrawn yarn was 0.63, and the amount of terminal carboxyl groups was 21 eq.
/ 10 ⁶ g, the strength of 8.9 g / de, density 1.
It was 361 g / cm ³ . The wet heat resistance was 38%.

[0029]

As described above, the polyethylene naphthalate fiber of the present invention is made of conventional polyethylene-2,
Since it has extremely excellent heat and moisture resistance as compared with 6-naphthalate fiber, it is particularly suitable as a reinforcing fiber for industrial materials such as tire cords and belts, and its industrial significance is extremely large.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-104919 (JP, A) JP-A-58-163717 (JP, A) JP-B-52-66 (JP, B1) (58) Field (Int.Cl. ⁶ , DB name) D01F 6/62 301-308 D01F 6/92 301-309 D02G 3/48

Claims (1)

(57) [Claims] (1)Terminal carbohydrate with intrinsic viscosity of 0.70 or more
The amount of sil groups is 40 eq / 10 ⁶ g or less, ethylene-
Polyester containing 90 mol% or more of 2,6-naphthalate units
Add N, N'-bis (2,6-diisopropyl
Enyl) carbodiimide in an amount of 0.5
Polyethylene obtained by melt-spinning by adding about 2.5% by weight
A phthalate fiber which satisfies the following at the same time
A polyethylene naphthalate fiber, characterized in that:  0.70 ≦ intrinsic viscosity IV ≦ 1.00  Terminal carboxyl group content CV ≦ 15 eq / 10 ⁶ g  Strength ST ≧ 9.0 g / de  Density d ≧ 1.362 g / cm ^Three