JP2752317B2 - Polyurethane elastic body excellent in heat resistance and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-quality thermoplastic polyurethane elastomer having excellent heat resistance and a method for continuously producing the same.

[0002]

2. Description of the Related Art To obtain a thermoplastic polyurethane resin industrially, a polymer diol having a long molecular weight at both ends and a polymer diol having a short molecular weight and an organic diisocyanate having an isocyanate group at both terminals are polyaddition. The reaction is generally carried out. At present, thermoplastic polyurethanes are used in a wide range of fields, and various methods are also known for their production by bulk polymerization. Two, three
For example, a method of producing a polyurethane elastic body by reacting a polymer glycol with a diisocyanate compound and a low molecular weight diol in a kneader such as a kneader and then performing a heat treatment (JP-B-39-17093) ),
There is known a method in which raw materials mixed in advance are supplied onto a movable conveyor, and the raw materials are maintained at a temperature at which the reaction sufficiently proceeds, and then continuously pelletized (Japanese Patent Publication No. 43-5920). Among these methods, when an elastic body is obtained by performing a reaction in a kneader, the reaction product has strong adhesiveness, and the work of peeling off from the rotating blade is extremely difficult. Therefore, it is very difficult to strictly control the ratio of the raw materials charged for each batch, the processing temperature, the processing time, the water content, and the like, and it is therefore difficult to achieve uniform products. Further, the method of continuously supplying and mixing the raw materials on the conveyor has a long heat treatment time on the conveyor, and is extremely inefficient and difficult to use industrially.

As a means for avoiding these drawbacks, there is a method for producing a polyurethane resin continuously and in a short time (JP-A-5-128137). This method is a continuous production method of polyurethane resin and is very excellent as a labor-saving and energy-saving production method.However, it is not possible to obtain a polyurethane elastic body having excellent thermal stability and few lump, and the control of the reactor is difficult. Due to the difficulty, there is a problem that the viscosity (degree of polymerization) becomes non-uniform.

Further, as a method for improving the thermal stability, there is a method of limiting the composition of the raw material (JP-A-2-191161) and a method of using a special organic diisocyanate (JP-A-1-95119). . However, these methods have excellent thermal stability for a relatively short time, but when the thermoplastic polyurethane is exposed to a heating state for an extremely long time such as spinning, the thermally degraded polymer accumulates on the tube wall, and lumps are generated. A high quality polyurethane elastic body cannot be obtained.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a high-quality polyurethane elastic body which is excellent in thermal stability and has a small amount of lumps, and a process for continuously producing the same, which is industrially advantageous. It is in.

[0006]

Means and Action for Solving the Problems The present inventors have
As a result of studying to solve the above problems, it has been found that a polyurethane elastic body that can achieve the object of the present invention can be produced only in a limited method as described below,
The present invention has been completed.

That is, the polyurethane elastomer of the present invention is a thermoplastic polyurethane elastomer produced by bulk polymerization, and is 5 to 70% by weight of the organic diisocyanate used.
Consists of paraphenylene diisocyanate and 5-70% by weight of the low molecular weight diol used consists of bishydroxyethoxybenzene, the ratio of the melt index at 27-30 minutes to the melt index at 220 ° C. at 6-9 minutes (MI 1.00-1.
01.

A second aspect of the present invention is a polyurethane elastic fiber comprising the above polyurethane elastic body. The polyurethane elastic body and the polyurethane elastic fiber of the present invention further comprise a fish eye based on a polyurethane substrate and a polyurethane 1k.
It contains only 500 or less per g. It should be understood that a fisheye based on a polyurethane substrate does not include additives added to the polyurethane, such as fillers, matting agents such as titanium oxide, or unintentionally contained insolubles (dust). It is. The preferred proportion of fisheye is polyurethane elastomer 1
Not more than 200 per kg.

[0009] Fisheye based on polyurethane substrates, according to the work of the present inventor, shows that (a) 5 ° C at 20 ° C.
A crystal grain having a size of about 50 μm and melting at a melting point (Tm) of a homopolymer composed of only a hard segment constituting a polyurethane substrate, or (b) having a size of 5 μm or more at 20 ° C. However, it was revealed that the gel was not melted at the melting point Tm. When the former is observed with a polarizing microscope, it can be confirmed that the crystallized portion of the hard segment in the polyurethane elastic material emits light (birefringence) and disappears when heated to the crystal melting point Tm of the polymer composed of the hard segment. The size of the crystallized portion of this hard segment is 5
For example, 1,4-butanediol and 4,4′-diphenylmethane diisocyanate have a crystal melting point of 245 ° C. to 260 ° C., so that the crystal grains of μm or more usually melt at 200 ° C. to 240 ° C. Even after melt extrusion molding such as spinning, it remains on the fiber or film as it is and becomes a fish eye or its core, spun yarn breakage, poor unwinding of the wound body due to remarkable stickiness, perforation of the knitted fabric, weft step or film fish Large crystal grains which cause troubles such as eyes and do not pass through the filter, for example, 40μ
Those having a diameter of about m or more cause an increase in filtration pressure. On the other hand, a gel-like substance having a size of 5 μm or more, which does not disappear even at the crystal melting point, emits light weaker than crystal grains and is often amorphous. The gel-like substance remains as an insoluble substance when the polyurethane elastic body is dissolved with a solvent. This gel-like substance passes through a filter or a nozzle hole, but becomes a fisheye such as a fiber or a film or its core as well as crystal grains, and causes trouble. On the other hand, a colored portion having a size of less than 5 μm does not cause the above trouble.

In the present invention, fish eyes are defined or measured as follows. Fish eye: Fish eye having a diameter of 100 μm or more. Fish eye is measured by running a fiber (usually having a diameter of about 20 μm to 70 μm) between a pair of roll bearings, detecting a change in the distance between the roll bearings using a strain gauge to detect a node having a diameter of 100 μm or more, and then confirming with a polarizing microscope. Measurement. For sheets and films (usually about 20 μm to 600 μm in thickness), fish eyes having a predetermined size are counted with a microscope.

The method for producing a polyurethane elastomer according to the present invention is characterized in that a prepolymer is formed by preliminarily reacting an organic diisocyanate in which paraphenylene diisocyanate accounts for 5 to 70% by weight with a high molecular weight diol. Prepolymer and bishydroxyethoxybenzene are 5
Wherein the molar ratio of isocyanate groups in all organic diisocyanates to hydroxyl groups in all diols is 0.9.
It is preferred to polymerize so as to be in the range of 8 to 1.02.

The organic diisocyanate used as a raw material in the present invention may be any of parafinylene diisocyanate occupying 5 to 70% by weight and aromatic or aliphatic diisocyanate generally used for producing polyurethane resin. May be. For example, 4,4'-diphenylmethane diisocyanate, toluene diisocyanate,
Naphthalene-1,5-diisocyanate, polymethylene polyphenyl isocyanate, xylene diisocyanate, 2,2'-dimethyl-4,4'-diphenylmethane diisocyanate, 1,3- or 1,4-bis ( Isocyanatomethyl) benzene, 1,3- or 1,4-
Bis (isocyanatomethyl) cyclohexane, 4,
Known diisocyanates such as 4'-methylenebiscyclohexyl metadiisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, cyclohexane diisocyanate and the like, and isocyanurate-modified and carbodiimidated products of these isocyanates;
Bullet-modified products. These organic diisocyanates may be used alone or in combination of two or more.

The proportion of parafinylene diisocyanate to the total organic diisocyanate needs to be 5 to 70% by weight. If it is less than 5% by weight, the required heat resistance cannot be obtained, and if it exceeds 70% by weight, a side reaction due to parafinylene diisocyanate is liable to occur, and a polyurethane elastic body having less fish eyes is obtained. It is not possible.

The high molecular diol is selected from the group consisting of polyester diol, polyether diol, polycarbonate diol and polyester ether diol.
One or more polymer diols are included. As the polyester diol, ethylene glycol, propylene glycol, 1,4-butanediol, 1,5-
Pentanediol, 1,6-hexanediol, neopentyl glycol, 2-methylpropanediol or other low molecular weight diols and low-molecular-weight substances such as glutanic acid, adipic acid, pimelic acid, suberic acid, sebacic acid, terephthalic acid, and isophthalic acid Examples thereof include a condensation polymer with a molecular weight dicarboxylic acid, and a polylactone diol obtained by ring-opening polymerization of lactone, such as polycaprolactone glycol, polypropiolactone glycol, and polyvalerolactone glycol. Examples of the polyether glycol include polyalkylene ether glycols such as polyethylene ether glycol, polypropylene ether glycol, polytetramethylene ether glycol, and polyhexamethylene ether glycol. Further, as the polycarbonate diol, low molecular weight diols such as 1,4-butanediol,
Polycarbonate diols obtained by condensing aliphatic or alicyclic diols such as pentanediol, 1,6-hexanediol, octanediol, and decanediol with the action of diphenyl carbonate or phosgene.

The average molecular weight of these high molecular weight diols is usually from 500 to 3,000, preferably from 500 to 3,000.
It is preferably in the range of 2500. If the average molecular weight is too small, the compatibility with the organic diisocyanate is too good, and the elasticity of the produced polyurethane is poor.On the other hand, if the average molecular weight is too large, the compatibility with the organic diisocyanate becomes poor, and the mixing in the polymerization step is difficult. It does not work well, resulting in the formation of lumps of gel-like substances and the inability to obtain a stable polyurethane.

The low molecular diols are those having bishydroxyethoxybenzene of 5 to 70% by weight and a molecular weight of less than 500, and include ethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentane glycol, Examples thereof include aliphatic and aromatic diols such as methylpentane glycol, 1,6-hexanediol and 1,4-bishydroxyethylbenzene. These may be used alone or as a mixture of two or more.

It is necessary that the ratio of bishydroxyethoxybenzene to the total low molecular weight diol be 5 to 70% by weight. If the amount is less than 5% by weight, the required heat resistance cannot be obtained, and if it exceeds 70% by weight, a side reaction due to bishydroxyethoxybenzene tends to occur, and a polyurethane elastic body having less fish eyes can be obtained. Can not.

According to the method described in JP-B-43-5920, a mixture of the above-mentioned polymer diol and low-molecular-weight diol is reacted with an organic diisocyanate at a time. Due to the difference in reactivity of the molecular diol, a large number of lumps due to the crystalline hard segments are generated, and the viscosity also varies greatly.
However, a prepolymer method in which the organic diisocyanate and the polymer diol are reacted in advance preferably in a molar ratio of 5: 1 to 2: 1, more preferably in a range of 3.5: 1 to 2.5: 1 By taking the above, fish eyes can be remarkably reduced to 500 or less (preferably 200 or less) per kg.

The ratio of the high molecular diol, the low molecular diol and the organic diisocyanate used is determined by the molar ratio (R) of the isocyanate group in the organic diisocyanate to the hydroxyl group in all the diols of the high molecular diol and the low molecular diol.
Is preferably in the range of 0.98 to 1.02. If the R value is out of this range, the resulting polyurethane elastic body is not satisfactory in terms of physical properties and melt moldability or contains many gel-like fish eyes, which is not preferable.

In the polymerization of the polyurethane elastomer, the prepolymer and the low molecular weight diol are first uniformly mixed and then supplied to a screw type extruder. A twin screw extruder can be suitably used as the screw type extruder.
The rotation speed is 30 to 300 rpm, the cylinder temperature of the polymerization zone is 210 to 245 ° C, and the tip extrusion pressure is 20 to 45 kg.
By performing melt polymerization at / cm ² , a high-quality polyurethane resin having a small variation in molecular weight and an extremely small fisheye can be obtained. The average residence time depends on the screw and its L / D, but is usually from 2 to 20 minutes and the extrusion is continued from the outlet.

When a polyurethane elastic body or its fiber or film tube is manufactured according to the present invention, a finely divided colorant, an antioxidant, a lubricant, a weathering agent,
A well-known modifier such as a heat-resistant agent can be added from the popper opening of the extruder or dispersed in the prepolymer. In addition, when a prepolymer and a low molecular weight diol are mixed to increase the molecular weight, a known polymerization catalyst such as dibutyltin laurate or N-methylmorpholine can be dispersed in the low molecular weight diol and used.

[0022]

According to the production method of the present invention, a high-quality polyurethane elastic body having excellent heat resistance and extremely few fish eyes can be continuously produced in a short time. Further, the polyurethane elastic body of the present invention is excellent in melt moldability, and particularly eliminates yarn breakage due to fish eyes and perforations and weft steps in knitted products such as stockings, swimwear, and inners using yarns containing fish eyes. It is useful as a polyurethane elastic fiber.

[0023]

The present invention will be described below in detail with reference to examples. In addition, “parts” indicates parts by weight unless otherwise specified. Example 1 Polyesterdiol (polyhexanediol adipate: PHA, molecular weight 2017) 6 obtained by condensation polymerization of adipic acid and 1,6-hexanediol 6
7.30 parts, 11,65 parts of 4,4'-diphenylmethane diisocyanate (MDI) and 11.05 parts of parafinylene diisocyanate (PPDI) were each added to 70 parts.
At 80 ° C, PPDI in flake form
The reaction was carried out for 2 hours in an adjustment tank with a stirrer kept at a temperature of ° C. to prepare a prepolymer. Next, 5.15 parts of 1,4-butanediol (1,4-BD) as a low molecular weight diol,
Bishydroxyethoxybenzene (BHEB) 4.85
, And prepared in a storage tank at 80 ° C. From each tank, 18.0 kg / h and 2.0 kg / h were continuously supplied by a metering pump, mixed by a high-speed mixer, and then injected into a 45φ twin-screw extruder (rotating in the same direction) to carry out polymerization.
The cylinder temperature of the twin-screw extruder is 160 ° C, 180 ° C, 220 ° C, 240 ° C,
210 ° C. Pellets could be stably obtained in water from a 2.4φ 2-hole die at a screw rotation speed of 150 rpm and an extrusion pressure of 35 kg / cm ² using a pelletizer.

Next, the pellets were dewatered and dried to a water content of 80 ppm or less, and then a 25φ single screw extruder was used.
30 denier 1 filament x 8 at head temperature 190 ° C
When the melt spinning was performed for 5 days, polyurethane elastic fibers could be obtained extremely stably. Further, when a lump was measured on the obtained polyurethane elastic monofilament, it was found that the lump was a polyurethane elastic body having extremely few lump.

[0025]

[Table 1]

Example 2 The cylinder temperature of a twin screw extruder was set to 160
° C, 180 ° C, 220 ° C, 220 ° C, 210 ° C, PHA 76.52 parts, MDI 16.05 parts, PPDI
1.98 parts, BD 1.82 parts, BHEB 3.64 parts, the injection amount to the twin-screw extruder was 18.9 kg / hour,
A polyurethane elastic monofilament was produced in the same manner as in Example 1 except that the weight was 1.1 kg / hour.

Example 3 67.74 of a polyether diol (polytetramethylene glycol: PTMG, molecular weight 2014) obtained by ring-opening polymerization of tetrahydrofuran from a polymer diol was used.
Parts, MDI 9.63 parts, PPDI 11.75 parts, BD
A polyurethane elastic monofilament was produced in the same manner as in Example 1 except that 3.84 parts, 7.10 parts of BHEB, and the injection amount to the twin screw type extruder were 17.8 kg / hour and 2.2 kg / hour. .

Example 4 The dried pellets of Example 1 were melted by an extruder and then melted.
The sheet was extruded from a slit at 0 ° C. onto a quenching rotary drum to produce a sheet having a thickness of 0.6 mm. When the fish eye of this sheet was measured, an extremely high quality sheet of about 60 pieces per kg was obtained.

Comparative Example 1 A composition different from that of Example 1, 75.15 parts of PHA, MDI
19.41 parts, PPDI 0.90 parts, BD 3.79 parts,
A polyurethane elastic fiber was obtained in the same manner as in Example 1, except that 0.75 parts of BHEB and the injection amount to a twin screw extruder were 19.1 kg / hour and 0.9 kg / hour.

Comparative Example 2 A composition different from that of Example 1, 69.51 parts of PHA, MDI
9.89 parts, PPDI 11.07 parts, BD 4.96 parts,
A polyurethane elastic fiber was obtained in the same manner as in Example 1, except that 4.57 parts of BHEB and the injection amount to a twin screw extruder were set to 18.1 kg / hour and 1.9 kg / hour.

Comparative Example 3 76.80 parts of PTMG, 15.36 parts of MDI, PPDI
3.05 parts, BD 1.54 parts, and BHEB 3.99 parts were injected into the twin-screw extruder by one-shot method at an injection amount of 1
8.9 kg / h, 1.1 kg / h, and cylinder temperatures of 150 ° C, 170 ° C, 180 ° C, 190 ° C, 1
The temperature was changed to 90 ° C. A polyurethane elastic fiber was produced from the obtained polyurethane elastic body in the same manner as in Example 1.

Comparative Example 4 70.31 parts of PTMG, 4.98 parts of MDI, PPDI1
A polyurethane elastic sheet was produced in the same manner as in Example 4 except that 5.07 parts, BD 5.62 parts, and BHEB 3.32 parts were used.

[Brief description of the drawings]

FIG. 1 is a schematic view of an example of an apparatus suitable for the production method of the present invention.

[Table 2]

Claims (5)

(57) [Claims] 1. A thermoplastic polyurethane elastomer produced by bulk polymerization, wherein 5-70% by weight of the organic diisocyanate used consists of paraphenylene diisocyanate and 5-70% by weight of the low molecular weight diol used. % Of bishydroxyethoxybenzene, 200%
The ratio of the melt index at 27 to 30 minutes to the melt index at 6 to 9 minutes at 0 ° C is 1.0.
A polyurethane elastic material which is between 0 and 1.01. 2. A polyurethane elastic fiber comprising the polyurethane elastic body according to claim 1. 3. A polyurethane elastic sheet comprising the polyurethane elastic body according to claim 1. 4. The method according to claim 1, wherein the paraphenylene diisocyanate is 5 to 5.
An organic diisocyanate occupying 70% by weight and a polymer diol are previously reacted to form a prepolymer,
Next, a method for producing an elastic polyurethane material, comprising polymerizing the low molecular weight diol in which the prepolymer and bishydroxyethoxybenzene account for 5 to 70% by weight. 5. The molar ratio of isocyanate groups in all organic diisocyanates to hydroxyl groups in all diols is 0.9.
5. The method for producing a polyurethane elastic body according to claim 4, wherein the polymerization is carried out so as to be in the range of 8 to 1.02.