JPS5846573B2 - Manufacturing method of polyurethane elastic yarn - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an elastic polyurethane thread, and more particularly to a method for producing an elastic polyurethane thread having excellent heat resistance by a melt spinning method.

Generally, a wet spinning method or a dry spinning method is used to produce polyurethane elastic yarns, and there are relatively few cases where a melt spinning method is used.

This is because when melt-spinning a polyurethane elastomer, it is difficult to operate stably for a long time because the polyurethane elastomer generally has poor thermal stability when melted, and the polyurethane elastic yarn obtained by melt-spinning is not heat resistant. This is thought to be due to problems such as poor deformation and insufficient recovery from deformation at high temperatures.

Several methods have been proposed to improve the thermal performance of urethane yarns obtained by melt spinning.

For example, Japanese Patent Publication No. 44-20247 proposes a method of adding a special polyfunctional compound during the synthesis of polyurethane.

Further, Japanese Patent Publication No. 7426/1983 proposes a method of synthesizing polyurethane using a polyfunctional polyol and melt-spinning the polyurethane.

However, in the method of improving the heat resistance of polyurethane elastic yarn by imparting crosslinks to polyurethane using these polyfunctional compounds, the melting temperature of the polymer increases if sufficient crosslinking is imparted to improve the heat resistance. This creates a need to raise the temperature.

As a result, polyurethane tends to thermally decompose, resulting in unstable spinning.

An object of the present invention is to provide an elastic polyurethane yarn with excellent recovery characteristics from deformation at high temperatures.

Another object is to provide a method for producing such polyurethane elastic threads in a stable and industrially advantageous manner.

The method of the present invention is characterized in that when thermoplastic polyurethane is melt-spun, a polyisocyanate compound having a molecular weight of 400 or more is added to the molten polyurethane elastomer for mixed wave spinning.

The thermoplastic polyurethane elastomer applied to the present invention contains a known segmented polyurethane copolymer, and includes polyols with a molecular weight of 500 to 6,000, such as dihydroxy polyether, dihydroquine polyester, dihydroxy polylactone, dihydroxy polyester amide,
Dihydroxy carbonate and block copolymers thereof, etc., and organic diisocyanates with a molecular weight of 500 or less, such as p-p'-diphenylmethane diisocyanate, tolylene diisocyanate, hydrogenated p-p'-diphenylmethane diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, isophorone. Diisonanate, P.5-naphthylene diisocyanate, etc., and a chain extender having a molecular weight of 500 or less, such as water,
It is a polymer obtained by reaction with hydrazine, diamine, glycol, triol, etc.

Particularly good among these polymers are those using polytetramethylene ether glycol, polycaprolactone polyester, or polybutylene adipate, polyhexamethylene adipate, or polycarbonate as the polyol.

Moreover, as the organic diisocyanate, PV-diphenylmethane diisocyanate is suitable.

In addition, glycol is particularly suitable as a chain extender, and
-bis(β-hydroxyethoxy)benzene and 1.
4-butanediol is preferred.

As described above, in the present invention, as a thermoplastic polyurethane as a spinning raw material, a synthetic polymer is used as a general rule without using a branching agent or a crosslinking agent.

Therefore, the spinning temperature can be kept at a low level, and thermal deterioration of polyurethane can be suppressed.

Of course, polymers containing branching or crosslinking to the extent that the spinning temperature is not extremely high can also be suitably used.

The thermoplastic polyurethane used in the present invention can be synthesized by the so-called prepolymer method in which a polyol and an organic diisocyanate compound are reacted in advance and then reacted with a chain extender, or the so-called one-shot method in which all reaction raw materials are mixed at once. Either of these can be adopted.

Although it is possible to use a solvent or diluent during polymer synthesis, bulk polymerization is more suitable for producing polymer pellets for melt spinning.

As a method for bulk polymerization, a method of continuously or semi-continuously collecting the polymer using an extruder, a method of obtaining a block, powder or flake polymer by batch reaction, etc. are preferably used.

In the present invention, in addition to completely thermoplastic polyurethanes in which the polymer synthesis reaction has been sufficiently completed, which are used in the field of molded polyurethane elastomers, so-called incomplete thermoplastic nidistomers, that is, very few isocyanate groups remain. It is also possible to create crosslinking after molding using the pellets.

However, such pellets have a problem in that they are susceptible to deterioration due to humidity, temperature, etc. during storage, so it is convenient to use thermoplastic polyurethane that has undergone a complete reaction.

The polyisocyanate compound with a molecular weight of 400 or more applied to the present invention is a compound having at least two incyanate groups in the molecule. It can be synthesized by reacting a double equivalent or more of an organic diisocyanate with a molecular weight of 500 or less.

Moreover, a compound having three or more hydroxyl groups can also be used as the polyol.

Further, as the polyisocyanate compound, a dimer of organic diisocyanate or a carbodiimide-modified polyisocyanate can also be suitably used.

The number of isocyanate groups contained in one molecule of the polyisocyanate compound is preferably 2 to 4, and 2 diisocyanate compounds are particularly preferred.

If the number of isocyanate groups is too large, the viscosity of the polyisocyanate compound becomes high and handling becomes difficult.

The polyisocyanate compound preferably has a molecular weight of 400 or more, particularly 800 to 3,000.

The molecular weight of the polyisocyanate compound applied to the present invention is the apparent molecular weight calculated from the incyanate group weight measured by amine titration.

When the molecular weight of the polyisocyanate compound is less than 400, the activity is high, so it is easy to deteriorate on storage, and when adding a predetermined equivalent amount, the amount added becomes small, making handling difficult.

Moreover, if the molecular weight becomes too large, the amount of polyisocyanate compound to be added increases, and spinning after mixing tends to become unstable.

A suitable polyisocyanate compound has a molecular weight of 300.
Examples include isocyanate-terminated compounds obtained by addition-reacting at least one polyol selected from the group consisting of polyether, polyester, polyester amide, and polycarbonate with an organic diisocyanate having a molecular weight of 500 or less.

Particularly suitable polyols include polytetramethylene ether glycol, polycaprolactone polyester or polybutylene adipate.

Moreover, as the organic diisocyanate, P-P'-diphenylmethane diisocyanate is preferable.

The amount of the polyisocyanate compound of the present invention added is preferably 3 to 30% (by weight), particularly preferably 5 to 20% by weight, based on the mixture of the thermoplastic polyurethane elastomer and the polyisocyanate compound to be subjected to spinning. %.

The amount added varies depending on the type of polyisocyanate compound used, but if the amount added is small, the desired improvement in the thermal performance of the urethane thread will be insufficient.

On the other hand, if the amount added is too large, non-uniform mixing, deterioration of yarn quality, etc. tend to occur, and spinning becomes unstable, which is not preferable.

The melt spinning of the present invention involves adding a polyisocyanate compound to a part for melt extruding a thermoplastic polyurethane elastomer,
Preferably, the process is carried out in a spinning device with a mixing section and a spinning head.

As such a spinning device, a known device used for adding a modifier during spinning can be used.

Although it is possible to use a kneading device having a rotating part for adding and mixing the polyisocyanate compound to the molten polyurethane, it is more preferable to use a mixing device having a stationary kneading element. be.

A known mixing device having a static kneading element can be used.

The shape and number of elements of the static kneading element vary depending on the conditions of use, but are selected so that sufficient mixing of the polyurethane elastomer and polyisocyanate compound is completed before they are discharged from the spinneret. It is essential to do so.

An example of an embodiment of the present invention will be described below.

A pellet of thermoplastic polyurethane elastomer is supplied from a popper and heated and melted in an extruder.

The melting temperature is preferably in the range of 190 to 230°C.

On the other hand, the polyisocyanate compound is
The polyisocyanate compound is melted at a temperature below ℃ and degassed in advance. If the melting temperature is too high, the polyisocyanate compound tends to deteriorate, so it is preferable to keep it as low as possible within the melting range. Temperatures between room temperature and 100 ℃ are used as appropriate. It will be done.

The molten polyisocyanate compound is metered by a metering pump, filtered if necessary by a filter, and added to the molten polyurethane at a meeting point provided at the tip of the extruder.

The polyisocyanate compound and polyurethane are kneaded using a kneading device having a static kneading element.

This mixture is metered by a metering pump and introduced into the spinning head.

As the spinning head, a conventional synthetic fiber spinning device may be used, but it is preferable to design the spinning head in a shape that has as few retention areas as possible for the mixture.

After foreign matter is removed by a r-piece such as a wire mesh or glass beads in one layer provided in the spinning head if necessary, the mixture is discharged from the spinneret, cooled in air, coated with oil, and then wound up. Speed is usually 400-1500m/mix
is used.

Urethane yarn wound onto a spinning bobbin may have poor strength immediately after spinning, but its strength improves while it is left at room temperature, and its recovery characteristics from elongation at high temperatures also improve.

Further, by applying heat treatment by an appropriate method after spinning, improvement of yarn quality and thermal performance is promoted.

The reason why the yarn quality and thermal performance of the polyurethane elastic yarn spun as described above change over time is because the reaction of the polyisocyanate compound mixed with the thermoplastic polyurethane elastomer used as the spinning raw material is completed during spinning. It is presumed that this is because the process proceeds even after spinning without any process.

This reaction is believed to be the formation of a branched or crosslinked polymer through allophanate bonds between the polyurethane and the polyisocyanate compound.

The present invention will be explained below with reference to Examples.

Example 1 55.48 parts of dehydrated polytetramethylene ether glycol having a hydroxyl value of 102 (all parts hereinafter mean parts by weight).

) and 499 parts of 1,4-bis(β-hydroxyethoxy)benzene were charged into a jacketed Nigu, and after sufficiently dissolving with stirring, the temperature was kept at 85°C, and P
-P'-diphenylmethane diisocyanate 1953
** was added and reacted.

When stirring was continued, powdered polyurethane was obtained in about 30 minutes, which was formed into pellets using an extruder to form a polyurethane elastomer having a relative viscosity of 2.50 at a concentration of 1f/100cc measured at 25°C in dimethylformamide. Obtained.

On the other hand, 1000 parts of polytetramethylene ether glycol having a hydroxyl value of 112 and 500 parts of pp'-diphenylmethane diisocyanate were reacted at 80°C for 30 minutes to obtain a viscous polyisocyanate compound.

The isocyanate group content of this product was 5.60%, and the molecular weight calculated from this was 1500.

Using the thermoplastic polyurethane elastic pellets thus obtained and the polyisocyanate compound as spinning raw materials, spinning was carried out using a spinning machine equipped with a polyisocyanate compound supply device and a kneading device having a static intermixing element.

Using a nozzle with a diameter of 1.0 mm as a spinneret, a monofilament of 50 denier was spun at a winding speed of 500 m/rrIiII.

Table 1 shows the results of spinning with varying amounts of the polyisocyanate compound added to the urethane system.

The yarn quality and heat centrate shown in Table 1 are values measured after the spun urethane yarn bobbin was left at room temperature for 5 days.

The heat setting rate at 130°C is the setting rate when a 100% elongated urethane thread is heat-treated with dry heat at 130°C for 10 minutes.

From Table 1, when no polyisocyanate compound is added, the heat setting rate is large and the heat resistance is poor, but by adding a polyisocyanate compound and spinning, the heat setting rate is reduced, and therefore the heat resistance is improved. I understand that.

In addition, the larger the amount of polyisocyanate compound added, the softer the urethane yarn discharged from the spinneret, and although it was necessary to set the spinning temperature to a lower value, the effect of lowering the heat set rate was also greater.

Example 2 Dihydroxypolyε-caprolactone 7 with hydroxyl value 56
000 parts of 1,4-bis(β-hydroxyethoxy)benzene, 921 parts of P-P'-diphenyl diisocyanate), and the same method as in Example 1 to obtain a polymer powder. was pelletized using an extruder to obtain pellets of polyurethane elastomer having a relative viscosity of 1.98.

Further, 1500 parts of dihydroxypolyε-caprolactone having a hydroxyl value of 150 and 1000 parts of PV-diphenylmethane diisocyanate were reacted at 80°C to obtain a viscous polyisocyanate compound.

The incyanate content of this product was 6.74% and the molecular weight was 1250.

Spinning was carried out in the same manner as in Example 1 using the thermoplastic polyurethane elastomer pellets thus obtained and the polyisocyanate compound as spinning raw materials.

Table 2 shows the results of spinning with varying amounts of the polyisocyanate compound added.

Also shown are the results of constant length heat treatment at 130° C. for 3 hours immediately after spinning.

The heat setting rate of the urethane yarn spun without adding a polyisocyanate compound was 93%, but as seen in Table 2, the heat resistance was improved by the method of the present invention.

In addition, a test was conducted in which the polyurethane pellets used in Example 2 and the polyisocyanate compound were mixed in advance, the polyisocyanate compound was attached to the surface of the pellets, and then the pellets were fed into the hopper of a spinning machine. Because of this, the flow of the pellets was hindered and the pellets could not be fed to the extruder.

Example 3 1535 parts of polybutylene adipate with a hydroxyl value of 112,
314.4 parts of 1,4-butanediol and P-P'-
1198 parts of diphenylmethane diisocyanate were reacted to obtain polyurethane pellets with a relative viscosity of 2.05.

This polyurethane elastomer and the polyinsyanate compounds shown in Table 3 were used as spinning raw materials, and spinning was carried out in the same manner as in Example 1.

Table 4 shows the yarn quality and 130° C. heat set rate of the obtained urethane yarn after it was left at room temperature for 5 days.

130℃ without adding polyisocyanate compound
The heat setting rate was 95%, and it can be seen from Table 4 that the heat resistance was significantly improved by the method of the present invention.

Good results were also obtained when a trifunctional compound was used as the polyisocyanate compound.

However, when polyinsyanate compounds represented by symbols E, F, and G were used, spinning could be carried out stably for a long time in all cases;
When the polyisocyanate compound represented by is added, yarn breakage and nozzle clogging of the polyisocyanate compound supply device occurred, making stable spinning for a long time difficult.

Claims (1)

[Scope of Claims] 1. A method for producing polyurethane elastic yarn, which comprises performing mixed wave spinning by adding a polyisocyanate compound having a molecular weight of 400 or more to the melted polyurethane elastic body during melt spinning of the thermoplastic polyurethane elastic body. 2 Polyol forming thermoplastic polyurethane is 50%
Claim 1, which is a polyol containing at least one member selected from the group consisting of polytetramethylene glycol or polycaprolactone polyester, polybutylene adipate, polyhexamethylene adipate, and polycarbonate having a number average molecular weight of 0 to 6000. The method described in section. 3. The method according to claim 1, wherein the chain extender forming the thermoplastic polyurethane elastomer is a glycol or triol having a molecular weight of 500 or less. 4. The method according to claim 1, wherein the organic diincyanate forming the thermoplastic polyurethane elastomer is p-p'-diphenylmethane diisocyanate. 5. The method according to claim 1, wherein the polyisocyanate compound has a molecular weight of 800 or more. 6. The method according to claim 1, wherein the polyisocyanate compound is a diisocyanate compound. 7 The diisocyanate compound has a molecular weight of 300 to 2500
Claim 6, which is an isocyanate-terminated compound obtained by adding P-P'-diphenylmethane diisocyanate to both ends of at least one polyol selected from the group consisting of polyether, polyester, polyester amide, and polycarbonate. Method. 8. The method according to claim 1, wherein the amount of the polyisocyanate compound added is 3 to 30% by weight of the thermoplastic polyurethane elastomer. 9. The method according to claim 1, wherein the mixing is performed using a device equipped with a static crosstalk element.