JPH05163612A - Polyethylene naphthalate yarn - Google Patents

Abstract

PURPOSE:To provide the subject yarn having a specific intrinsic viscosity, a specific terminal carboxyl group content, a specific strength and a specific density, excellent in hydrolysis resistance and the wet heating resistance and suitable for reinforcing rubbers, etc. CONSTITUTION:The objective yarn comprises a polyethylene naphthalate yarn produced from a polyester containing ethylene 2,6-naphthalate units in an amount of >=90mol% and having a single filament fineness of <8 denier and simultaneously satisfies the following; an intrinsic viscosity I.V. of >=0.65; a terminal carboxyl group content CV of <=25eq/10<6>g; a strength of >=8.0g/de; and a density d of >=1.360g/cm<3>. The fiber is produced e.g. by adding N,N'-bis(2,6- isopropylphenyl) carbodiimide in an amount of 0.5-2.5wt.% based on a polyester to the polyester containing >=90mol% of ethylene terephthalate units and subsequently melt-spinning the mixture.

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 wet heat resistance, and more particularly to a polyethylene naphthalate fiber suitable for reinforcement in industrial material applications such as tire cords, belts and hoses. ..

[0002]

Polyethylene terephthalate fiber is widely used as a reinforcing fiber for rubber materials such as tire cords, belts and hoses. However, when it is enclosed in rubber and exposed to high temperatures, it is hydrated by moisture in the rubber. Undergoes disassembly,
The strength is greatly reduced and the durability in rubber is not sufficient. Therefore, it has been proposed to use polyethylene naphthalate fibers having excellent hydrolysis resistance for rubber reinforcement. However, when polyethylene naphthalate fiber is used, hydrolysis resistance is certainly improved as compared with polyethylene terephthalate, but it is not possible to obtain a material suitable for industrial material use only by itself. For example, Japanese Patent Publication Sho 56-
JP-A-27639 proposes that hydrolysis resistance can be improved by allowing 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. But with this proposal,
Since the drawn yarn has a specific crystal structure, the strength level of the obtained drawn yarn is about 5 to 6 g / de, which is a sufficient strength level as a canvas for papermaking which is the object of the proposal. It is insufficient as a reinforcing fiber for materials.
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 hydrolysis resistance. For example, Japanese Patent Publication No. 1-15
Japanese Patent Publication No. 604 and Japanese Patent Publication No. 3-47326 propose a method of adding a specific carbodiimide compound at the time of spinning to reduce the carboxyl group concentration of polyethylene terephthalate fiber.

However, in the case of polyethylene naphthalate fiber, the hydrolysis resistance may be originally good,
In addition, since it has not been sufficiently used in the rubber material field, no specific proposal for further improvement in hydrolysis resistance can be found other than the above-mentioned proposal for the papermaking kanbans. The current situation.

[0004]

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

[0005]

The above object of the present invention is a polyethylene naphthalate fiber having a single yarn fineness of less than 8 denier, which is made of polyester containing 90 mol% or more of ethylene-2,6-naphthalate units. (i) ~ (i
This is achieved by a polyethylene naphthalate fiber characterized by satisfying v) at the same time. (i) Intrinsic viscosity IV ≧ 0.65 (ii) Terminal carboxyl group amount CV ≦ 25 eq / 10 ⁶ g (iii) Strength ST ≧ 8.0 g / de (iV) Density d ≧ 1.360 g / cm ³

The polyethylene naphthalate referred to in the present invention contains 90 mol% of ethylene-2,6-naphthalate unit.
It suffices to include the above, and a polymer containing an appropriate third component in an amount of 10 mol% or less may be used. Generally, polyethylene-2,6-naphthalate is naphthalene-
It is synthesized by polycondensing 2,6-dicarboxylic acid or its ester-forming derivative with ethylene glycol in the presence of a catalyst under suitable reaction conditions. At this time, if one or more appropriate third components are added before the completion of the polymerization of polyethylene-2,6-naphthalate,
Copolyester is synthesized.

Suitable third components include (a) compounds having two ester-forming functional groups; eg oxalic acid,
Aliphatic dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, dimer acid; alicyclic dicarboxylic acids such as cyclopropane dicarboxylic acid, cyclobutane dicarboxylic acid, hexahydroterephthalic acid; phthalic acid, isophthalic acid, naphthalene-2,7 -Aromatic dicarboxylic acids such as dicarboxylic acid and diphenyldicarboxylic acid; carboxylic acids such as diphenyletherdicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenoxyethanedicarboxylic acid and sodium 3,5-dicarboxybenzenesulfonate; glycolic acid, p-oxy Benzoic acid, oxycarboxylic acid such as 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'-dihydroxydiphenyl sulfone, 1,
4-bis (β-hydroxyethoxy) benzene, 2,2
An oxy compound such as bis (p-β-hydroxyethoxyphenyl) propane and polyalkylene glycol; a functional derivative thereof; a high degree of polymerization derived from the carboxylic acid, oxycarboxylic acid, oxy compound or a functional derivative thereof. Examples thereof include compounds and (b) compounds having one ester-forming functional group, such as benzoic acid, benzyloxybenzoic acid, and methoxypolyalkylene glycol.

Further, (c) a compound having three or more ester-forming functional groups, such as glycerin, pentaerythritol, and trimethylolpropane, can be used within the 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.

The polyethylene naphthalate fiber of the present invention has an intrinsic viscosity of the drawn yarn of 0.65 or more, preferably 0.7 to 1.0. The intrinsic viscosity referred to in the present invention is 35% by dissolving the polymer or undrawn yarn in a mixed solvent of phenol and orthodichlorobenzene (volume ratio 6: 4).
It is a value obtained from the viscosity measured at ° C. Intrinsic viscosity is 0.
When it is less than 65, not only the hydrolysis resistance is lowered, but also fibers of high strength and high toughness are not obtained, which is unsuitable as a reinforcing fiber. Fibers having an intrinsic viscosity of more than 1.0 tend to be defective in the spinning process and are not desirable in practice.

The amount of terminal carboxyl groups is 25 eq /
It is necessary to make it 10 ⁶ g or less, preferably 15 eq / 10 ⁶ g or less, and if it exceeds 25 eq / 10 ⁶ g, the hydrolysis resistance decreases and the object of the present invention cannot be achieved.

Further, the strength must be 8 g / de or more, preferably 9 g / de or more, and the fiber density must be 1.360 g / cm ³ or more, preferably 1.362 g / cm ³ or more, and one of them is less than the above. Also in this case, the hydrolysis resistance is insufficient and the object of the present invention cannot be achieved.

As described above, according to the present invention, the polyethylene naphthalate fiber having a single fiber denier of less than 8 denier has an intrinsic viscosity of 0.65 or more and a terminal carboxyl group amount of 25 eq / 10 ⁶ g or less, and A fiber having extremely excellent hydrolysis resistance can be obtained for the first time by providing a highly oriented fiber structure having a strength of 8.0 g / de or more and a density of 1.360 wobbles / cm ³ or more. I found that I could be done.

When the polyethylene naphthalate fiber of the present invention is used as a rubber reinforcing material, needless to say when the conventional polyethylene terephthalate fiber is used, its durability is higher than that of the conventional high strength polyethylene naphthalate fiber. It is remarkably excellent and its industrial significance is great.

Examples of the method for producing the polyethylene naphthalate fiber of the present invention include the following methods. That is, when melt-spinning a polyethylene naphthalate resin containing 90 mol% or more of ethylene-2,6-naphthalate units, a resin having an intrinsic viscosity of 0.7 or more and a carboxyl end group amount of 40 eq / 10 ⁶ g or less is used as a mono A carbodiimide compound is added in an amount of 0.5 to 2.5% by weight to obtain a polyethylene naphthalate unstretched yarn having a carboxyl end group amount of 25 equivalents / 10 ⁶ g or less, which is then heat-stretched to have a strength of 8 g / de or more. And the density is 1.360 g / cm ³
The method of using the above fibers is preferably adopted.

Various methods have been hitherto proposed for adding a compound during melt spinning to reduce the amount of terminal carboxyl groups of a polyester resin. However, all of these methods are directed to polyethylene terephthalate, and no polyethylene naphthalate has been proposed yet. In the case of polyethylene terephthalate, the compound to be added is an epoxy compound (Japanese Patent Publication No. 44-2).
7911) and cyclic carbonates and carbodiimide compounds (Japanese Patent Publication No. 55-9091). However, according to the study by the present inventors,
In the case of polyethylene naphthalate, which requires a melt spinning temperature of 310 ° C. or higher, it was found that the epoxy compound or the cyclic carbonic acid ester cannot be practically used because of a large decrease in the degree of polymerization or severe foaming. As a result of the investigation, they have found that the addition of the monocarbodiimide compound can effectively reduce the terminal carboxyl groups without lowering the polymerization degree of polyethylene naphthalate.

As the monocarbodiimide compound, for example, N, N'-di-o-toluylcarbodiimide, N, N'-
N'-diphenylcarbodiimide, N, N'-di-2,
6-Dimethylphenylcarbodiimide, N, N'-bis (2,6-diisopropylphenyl) -carbodiimide and the like are used, and among them, N, N'-bis (2,6-diisopropylphenyl) -carbodiimide is used for the heat during spinning. It is preferable because it causes less decomposition and side reactions. A polyfunctional carbodiimide compound such as a biscarbodiimide compound is not preferable because it makes it difficult to knead the polyethylene naphthalate and the polyfunctional carbodiimide compound in order to rapidly increase the polymerization degree of polyethylene naphthalate.

As a method for adding the monocarbodiimide compound, any conventionally known method can be adopted. For example, when the compound is a liquid, it remains in a liquid state, and when the compound is a solid, it is in a powder form, a melt, or an inert solvent such as xylene,
The solution melted in o-dichlorobenzene or the like may be mixed with the resin chips or injected into the inlet of the extruder.

Next, the residence time of the monocarbodiimide compound and the resin in the spinning machine is 2 minutes to 6 minutes after the resin temperature reaches 300 ° C. or higher, and the maximum temperature of the resin in spinning is 330 ° C. The following is preferable. 300
If the time after reaching ℃ does not reach 2 minutes, the amount of terminal carboxyl does not decrease sufficiently, while if it exceeds 6 minutes, the monocarbodiimide compound itself decomposes, resulting in poor hydrolysis resistance. Tend to come. Further, if the resin temperature during spinning does not reach 300 ° C., melt spinning cannot be stably performed, or even if it is possible, only weak yarn can be obtained. On the other hand, when 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 agent, and then temporarily wound as an undrawn yarn and then drawn by a so-called separate drawing method or continuously in a spinning process. The drawn yarn can be obtained by the direct drawing method in which the undrawn yarn is sent to the drawing process. The specific spinning and drawing methods are not particularly limited, and a conventionally known method may be adopted, but the strength of the obtained drawn yarn is 8 g / de or more and the density is 1.360 g /
It is necessary to set the spin-drawing conditions as appropriate so as to be at least cm ³ . As a preferred spinning method, a heating cylinder having an atmospheric temperature of 275 ° C. or more and a length of 20 cm or more is set immediately below the spinneret, and the spinning speed is set to 1000 m / min or less to obtain an undrawn yarn. Then, the first stage drawing is performed at a total draw ratio of 8
An example is a method in which after performing the stretching at a ratio of 0% or more, a fixed length or 3% or less of the limited shrinkage between the heating roll and the non-heating roll at a temperature of 225 to 250 ° C. and winding is performed.

[0021]

The present invention will be described in more detail with reference to the following examples.
The measured values in the examples are based on the following method. (A) Strength and elongation: Measured according to 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) Amount of terminal carboxyl group: A. Mak by Conix
romolecularChemie 26 , 226
According to the method described in (1958), an m-cresol / xylene mixed solvent (volume ratio 6/4) is used as a solvent,
Fibers were measured on undrawn yarn. (D) Moisture and heat resistance: The strength retention rate was evaluated when the fiber was allowed to relax and allowed to stand in saturated steam at 120 ° C. for 20 days continuously.

[0022]

Example 1 A polyethylene-2,6-naphthalate chip having an intrinsic viscosity of 0.85 and a terminal carboxyl group amount of 28 eq / 10 ⁶ g and N, N'-bis (2,6-isopropylphenyl) carbodiimide in a weight ratio of polyethylene. -
2,6-naphthalate / N, N'-bis (2,6-isopropylphenyl) carbodiimide = 100 / 1.8
The solid blended mixture at a ratio of (carbodiimide 50 equivalent / 10 ⁶ g) was fed to the extruder. The kneaded molten polymer was discharged from the die through 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 before discharging from the spinneret was also 318 ° C. The time required for discharging during this period was about 4 minutes. After passing through a heating cylinder with a length of 40 cm and a temperature of 350 ° C installed immediately below the base, a relative humidity of 65% and a temperature of 25
It was cooled and solidified with cooling air of ℃. An oiling 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 is 0.74, the amount of terminal carboxyl groups is 12 eq / 10 ⁶ g, and the single yarn fineness is 28d.
It was e.

Next, the unstretched yarn was pretensioned with 1%, and then the first stage drawing (ratio DRI) was performed between the heating supply roll (FR) at 155 ° C. and the 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). Furthermore, as a heat setting step, a relaxation rate (DR3) of 2% between the 2R (heated) and the unheated take-up roll (WR)
Shrinkage heat setting was carried out at, and it was wound up at 200 m / min.
Further, in some examples (No. 6 and No. 7), it was wound from the non-heated second stage drawing roll without heat setting.
The results are shown in Table 1. In addition, referring to the characteristics of commercially available polyethylene terephthalate fiber for tire yarn, Table 1
Shown in.

[0024]

[Table 1]

[0025]

Second Embodiment Experiment No. 1 of the first embodiment. In 1, N,
The same procedure was performed except that the amount of N'-bis (2,6-isopropylphenyl) carbodiimide added was changed. The results are shown in Table 2.

[0026]

[Table 2]

[0027]

[Comparative example] Intrinsic viscosity 0.70, terminal carboxyl group amount 4
Experiment No. 1 of Example 1 except that 0 equivalent / ton of polyethylene-2,6-naphthalate chips was used and the maximum temperature of the spinning machine was 315 ° C. The same procedure as 1 was performed. At this time, the intrinsic viscosity of the undrawn yarn is 0.63 and the amount of terminal carboxyl groups is 2
It was 1 eq / 10 ⁶ g, the strength was 8.9 g / de, and the density was 1.361 g / cm ² . Moisture and heat resistance was 38%.

[0028]

As described above, the polyethylene naphthalate fiber of the present invention is the same as the conventional polyethylene-2.
Since it has extremely excellent resistance to moisture and heat 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.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location D01F 6/92 301 F 7199-3B // D02G 3/48

Claims (3)

[Claims] 1. A single yarn fineness of 8 comprising a polyester containing 90 mol% or more of ethylene-2,6-naphthalate units.
A polyethylene naphthalate fiber having a denier less than that satisfying the following requirements (i) to (iv) at the same time. (i) Intrinsic viscosity IV ≧ 0.65 (ii) Terminal carboxyl group amount CV ≦ 25 eq / 10 ⁶ g (iii) Strength ST ≧ 8.0 g / de (iV) Density d ≧ 1.360 g / cm ³ 2. Ethylene having an intrinsic viscosity of 0.70 or more and a terminal carboxyl group content of 40 eq / 10 ⁶ g or less
A polyester obtained by adding 90-mol% or more of 2,6-naphthalate unit to a polyester containing 0.5 to 2.5% by weight of monocarbodiimide, and melt-spinning the obtained product.
The polyethylene naphthalate fiber described. 3. The polyethylene naphthalate fiber according to claim 2, wherein the monocarbodiimide is N, N′-bis (2,6-isopropylphenyl) carbodiimide.