JPH04277513A - Production of polyurethane elastomer, and fiber and sheet of the elastomer - Google Patents

Abstract

PURPOSE:To provide a process for producing a polyurethane elastomer of a low agglomerate content and a low dispersion of viscosity continuously, stably and industrially advantageously, and a fiber and a sheet prepared by molding the elastomer. CONSTITUTION:A process for producing a polyurethane elastomer comprising prereacting at least an organic diisocyanate with a polymer diol to form a prepolymer, continuously mixing said prepolymer with a low-molecular diol, and conducting continuous solid phase polymerization of the mixture, and an elastic fiber and an elastic sheet prepared from the elastomer.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for continuously producing high quality thermoplastic polyurethane elastomers, and to fibers and sheets thereof.

0002

BACKGROUND OF THE INVENTION Various methods are known for producing thermoplastic polyurethane. An example is a method of producing a polyurethane elastomer by subjecting a polymer glycol, a diisocyanate compound, and a crosslinking agent to a solution polymerization reaction in a solvent (Japanese Patent Publication No. 35-16588).
, a method for producing a polyurethane elastomer by reacting a polymer glycol and a diisocyanate compound in a kneader such as a kneader without using a solvent (Japanese Patent Publication No. 39-17093
Publication No.) etc. are known.

[0003] Among these methods, the method in which the reaction is carried out using a solvent requires a step of separating the solvent after the reaction is completed, and is extremely inefficient because it is a batch method. In addition, when obtaining an elastic body by performing a solid phase polymerization reaction in a kneader without using a solvent, the reaction product has strong adhesive properties,
It is extremely difficult to remove it from the rotating blades or turn it into powder. Generally, when carrying out a batch reaction, it is very difficult to strictly control the ratio of raw materials to be charged in each batch, treatment temperature, treatment time, regulation of moisture content, etc. is difficult to measure.

[0004] As a means to avoid these drawbacks, a method for continuously producing polyurethane resin (Japanese Patent Publication No. 43-52
No. 90). This method is very excellent as a labor-saving and energy-saving manufacturing method for polyurethane resin as it is a continuous solvent-free method, but it is not possible to obtain a polyurethane elastomer with few lumps, and it is difficult to control the reactor, so the viscosity (
There is a problem that the degree of polymerization becomes non-uniform.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide an industrially advantageous method for continuously producing a high-quality polyurethane elastomer with less lumps and less variation in viscosity.

[0006]

[Means for Solving the Problems] As a result of studies to solve the above-mentioned problems, the present inventors have discovered that it is possible to produce a polyurethane elastomer that can achieve the object of the present invention using a limited method as described below. They discovered this and completed the present invention.

That is, the present invention is characterized in that at least an organic diisocyanate and a high-molecular diol are reacted in advance to form a prepolymer, and then the prepolymer and a low-molecular diol are mixed and then subjected to solid phase polymerization. . Preferably, the average viscosity (ηa) of the polyurethane elastomer obtained by solid phase polymerization is 2.0 to 2.5, and the number of lumps is 500 or less per kg. More preferably, the present invention relates to a polyurethane elastic body whose viscosity (η) is 95% by weight or more and satisfies the following formula (I). 0.95ηa ≦η≦1.05η
a...(I)

Further, the present invention provides polyurethane elastic fibers and polyurethane elastic sheets (including films) made of the above polyurethane.

In the present invention, lumps and viscosity are defined or measured as follows.

[0010] Agglomerates: Agglomerates with a diameter of 100 μm or more. The measurement method for lumps is based on fibers (usually diameter is 20 μm ~
(approximately 60 μm), it is measured by running it and measuring the change in transmittance of the optical sensor due to the lumps. For sheets and films (usually about 20 μm to 60 μm thick), the lumps are counted using a microscope.

Viscosity: Using an Ostwald viscometer, using dimethylformamide (DMF) as a blank, measuring the falling seconds of a 1% by weight DMF solution at 25°C, and calculating from the following formula.

The organic diisocyanate used as a raw material in the present invention may be any aromatic or aliphatic diisocyanate generally used in the production of polyurethane resins, such as 4,4'-diphenylmethane diisocyanate. Nato, toluene diisocyanate, naphthalene-1,5-diisocyanate, polymethylene polyphenylisocyanate, 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 , 4,4'-
Known diisocyanates such as methylenebiscyclohexylmetadiisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, cyclohexane diisocyanate, and isocyanurate-modified products, carbodiimidation-modified products, and buret-modified products of these isocyanates. It is of good quality. These organic diisocyanates may be used alone or in combination of two or more.

[0013] As the polymer diol, one selected from polyester diol, polyether diol, polycarbonate diol, and polyester/ether diol is used.
Examples include one species or two or more kinds of polymeric diols. Examples of polyester diol include 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 diols such as glutanic acid, adipic acid, pimelic acid, suberic acid, sebacic acid, terephthalic acid, isophthalic acid, etc. Condensation polymer with molecular weight dicarboxylic acid,
Alternatively, polylactone diols obtained by ring-opening polymerization of lactones, such as polycaprolactone glycol, polypropiolactone glycol, polyvalerolactone glycol, etc., can be mentioned. Examples of the polyether glycol include polyalkylene ether glycols such as polyethylene ether glycol, polypropylene ether glycol, polytetramethylene ether glycol, and polyhexamethylene ether glycol. Furthermore, polycarbonate diols include low molecular weight diols such as aliphatic or aromatic diols such as 1,4-butanediol, pentanediol, 1,6-hexanediol, octanediol, and decanediol, which are treated with diphenyl carbonate or phosgene. Examples include polycarbonate diols condensed with

[0014] The average molecular weight of these high molecular weight diols is usually 500 to 3,000, preferably 500 to 2,000.
Preferably, it is within the range of 500. If the average molecular weight is too small, the compatibility with the organic diisocyanate will be too good and the resulting polyurethane will have poor elasticity, while if the average molecular weight is too large, the compatibility with the organic diisocyanate will be poor and mixing in the polymerization process will be difficult. This does not go well, resulting in the formation of gel-like lumps and the inability to obtain stable polyurethane.

[0015] Low-molecular diols have a molecular weight of less than 500, and include ethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentane glycol, 3-methylpentane glycol, 1,6-hexanediol, Examples include aliphatic and aromatic diols such as 1,4-bishydroxyethylbenzene. These may be used alone or in combination of two or more.

The method for polymerizing the polyurethane elastomer is as described in Japanese Patent Publication No. 43-5920. When a mixture of the above-mentioned high-molecular diol and low-molecular diol is reacted with an organic diisocyanate, the high-molecular diol and the low-molecular diol are reacted at once. Due to the difference in reactivity of molecular diols, many lumps of crystalline hard segments are generated, and the viscosity also varies widely. However, a prepolymer method in which an organic diisocyanate and a polymeric diol are reacted in advance preferably at a molar ratio of 5:1 to 2:1, more preferably 3.5:1 to 2.5:1. By taking the above amount, the number of lumps can be significantly reduced to 500 pieces or less (preferably 200 pieces or less) per 1 kg. The average viscosity (ηa) of the polyurethane elastomer is usually 2.0 to 2.5, and the viscosity (η) of 95% by weight or more measured with pellets etc. is preferably in the range of formula (I) below, more preferably is the following (I
I) is within the range of formula. 0.95ηa ≦η≦1.05η
a...(I)
0.97ηa ≦η≦1.03ηa
...(II)

[0017] Also,
The usage ratio of high molecular diol, low molecular diol and organic diisocyanate is 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 low molecular diol. 1.0
It is preferable that the amount is within the range of 5. If the R value deviates from this range, the resulting polyurethane elastomer may not be satisfactory in terms of physical properties or melt moldability, or it may contain a large number of gel-like lumps, which is not preferable.

The detailed method for producing the polyurethane elastomer according to the present invention is as follows. The prepolymer and low-molecular-weight diol are mixed in a high-speed mixer, i.e., at a rotation speed of 500 to 500.
After uniformly mixing with a device that has rotor blades that rotate at 0 rpm and has the ability to combine sufficient mixing and extrusion,
It is discharged onto a continuously moving belt conveyor at a temperature of 120° C. or lower and within an average residence time of 1 minute. If the temperature of the high-speed mixer is set to 120°C or higher, the reaction between the prepolymer and the low-molecular-weight diol will proceed rapidly, causing gelation in the high-speed mixer, which is undesirable. It is undesirable because it causes oxidation. Furthermore, the mixture on the belt conveyor is 80℃~160℃
The temperature is preferably maintained at 120°C to 140°C, which is sufficient to sufficiently promote the solid phase polymerization reaction, and after residence for 0.1 to 2 hours, it is made into particles by a sheet cutter or a pulverizer, which is continuously It is then fed to an extruder and made into pellets.

When producing a polyurethane elastomer or its fibers or film according to the present invention, if necessary, finely powdered colorants, antioxidants, lubricants, weathering agents, heat resistant agents, etc. are extruded during pelletization. Add it from the hopper mouth of the machine,
They can also be dispersed in prepolymers.

[0020] Also, when mixing the prepolymer and low-molecular diol to increase the molecular weight, dibutyltin laurylate, N
- It is also possible to use a known polymerization catalyst such as methyl monophorine dispersed in a low molecular diol.

Furthermore, solid phase polymerization and particle formation are carried out at 200 ppm.
It is preferable to carry out the following inert gas. If the above water content is 200 ppm or more, many lumps of gelled product will be formed due to the reaction between the isocyanate groups and the water in the system, and the resulting polyurethane elastomer will not be satisfactory in terms of physical properties and melt moldability, which is undesirable. .

[0022]

[Example] Example 1 Polyester diol obtained by condensation polymerization of adipic acid and 1,6-hexanediol (polyhexanediol adipate ester: hereinafter referred to as PHA, molecular weight 20
00) 48.7 parts and 19.8 parts of 4,4'-diphenylmethane diisocyanate (MDI) were each pre-melted at 70°C and reacted for 2 hours in an adjustment tank with a stirrer kept at 85°C. The polymer was prepared.

Next, 1,4-butanediol (1,4-BD) was used as a low molecular weight diol and prepared in a storage tank at 80°C. 9.8k from each tank by metering pump
After continuously feeding 0.7 kg/hour and mixing with a high-speed mixer, a polyurethane sheet with a thickness of 5 mm was continuously discharged onto a belt conveyor whose surface was smoothed. The mixture on the belt conveyor is at 120°C and has a moisture content of 200.
After solid-phase polymerization was carried out by moving the mixture in an oven in a nitrogen atmosphere kept below ppm for about 1 hour, the mixture was pulverized by a roller sheet cutter and continuously fed to the hopper mouth of a single-screw extruder. The cylinder temperatures of the single-screw extruder are maintained at 160°C, 190°C, and 230°C from the hopper mouth. The above polyurethane has a screw rotation speed of 100 r.
pm and was discharged into water from a 2.4φ 4-hole mouthpiece, and could be stably pelletized using a pelletizer.

Next, the pellets were dehydrated and dried to a moisture content of 80 ppm or less, and then melt-spun into 8 x 30 denier filaments using a 25φ single screw extruder at a head temperature of 190°C. When the obtained polyurethane elastomer monofilament was measured for lumps,
It was found to be a polyurethane elastomer with extremely few lumps (see Table 1).

Example 2 A polyurethane elastomer monofilament was produced in the same manner as in Example 1, except that the temperature on the belt conveyor was changed to 150° C. and the time during which the belt conveyor moved in the oven was changed to 30 minutes.

Comparative Example 68.5 parts of the polyol with a molecular weight of 2000 from Example 1 and 1
, 4-BD 6.8 parts mixture and MDI at 80°C.
Using a metering pump from a storage tank, 7.5 kg/hour, 2.8
A polyurethane elastomer monofilament was produced in the same manner as in Example 1, except that kg/hour was continuously fed to the high-speed mixer.

[0027]

[Table 1]

[0028]

[Effects of the Invention] As is clear from the results of the above Examples and Comparative Examples, if the production method of the present invention is followed, a high quality polyurethane elastomer with less lumps and less variation in viscosity can be obtained.
and its fibers and sheets can be obtained. Furthermore, the production method of the present invention is found to be an industrially advantageous method since the polyurethane elastomer can be obtained continuously and stably.

Claims (6)

[Claims] Claim 1: At least an organic diisocyanate and a high-molecular-weight diol are reacted in advance to produce a prepolymer, and then the prepolymer and a low-molecular-weight diol are continuously mixed, followed by continuous solid phase polymerization. A method for producing a characteristic polyurethane elastic body. 2. A claim characterized in that the polyurethane elastomer obtained by solid phase polymerization has an average viscosity (ηa) of 2.0 to 2.5, and the number of lumps is 500 or less per kg. The method described in Section 1. 3. The method according to claim 1, wherein the prepolymer and the low-molecular-weight diol are mixed in a high-speed mixer. 4. The method according to claim 1, wherein the mixing and solid phase polymerization are carried out in an inert gas with a moisture content of 200 ppm or less. 5. A polyurethane elastic fiber comprising the polyurethane elastic body according to claim 1. 6. A polyurethane elastic sheet comprising the polyurethane elastic body according to claim 1.