JPH07138341A - Polyurethane elastomer and its production - Google Patents

Abstract

PURPOSE:To produce a thermoplastic polyurethane elastomer excellent in elastic recovery and elongation at break by using a specific low-mol.-wt. diol and a specific high-mol.-wt. diol and using a prepolymer process. CONSTITUTION:This polyurethane elastomer is obtd. by reacting an org. polyisocyanate with a polyether diol having a wt.-average mol.wt. of 1,800-2,800 and a ratio of the wt.-average to the number average mol.wt. of 1.15 or lower, reacting the resulting prepolymer with 1, 6-hexanediol, and subjecting the resulting product to solid-phase polymn.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoplastic polyurethane elastic body excellent in elastic recovery and elongation at break, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, a polyurethane elastic material has a high molecular polyol and a polyisocyanate as raw materials, and if desired, a low molecular weight compound having two or more activated hydrogens as raw materials. As an ether polyol,
Polyoxyalkylene polyol (PP produced by the reaction of an alkylene oxide with an initiator having active hydrogen)
G), polytetramethylene glycol (PTMG) obtained by cationic polymerization of THF, and polyether glycol modified products obtained by modifying these polyols are used. JP-A-57-185313 discloses that a polyurethane in which the molecular weight distribution of polycaprolactone polyol is specified has an elastic recovery rate and a low viscosity and is excellent in workability.

[0003]

Generally, polyurethane elastic yarns using polyether glycol have inferior light resistance as compared with polyurethane elastic yarns using other ester-based or carbonate-based glycols, but have excellent elastic performance. It is known to have. However, the polyurethane elastic yarn obtained by melt spinning is excellent in the uniformity of the yarn, but the elastic recovery property and the elongation at break are lower than those obtained by other spinning methods. There is a method of introducing an intermolecular crosslinked structure into polyurethane as a method of making the elastic recovery rate excellent, but in the case of the polyurethane elastic yarn thus obtained, the elongation is remarkably reduced due to the intermolecular crosslinked structure. . The present invention is to propose a polymerization composition and a polymerization method for simultaneously satisfying a high elastic recovery rate and a high breaking elongation even in a melt spinning method in a low temperature atmosphere.

[0004]

[Means and Actions for Solving Problems] The inventors of the present invention have made diligent studies to solve the above problems, and as a result,
It has been found that a polyurethane elastomer which can achieve the objects of the invention can be produced in the following limited manner.

That is, the polyurethane elastic material of the present invention is a thermoplastic polyurethane elastic material using 1,6 hexanediol as a low molecular weight diol, and has a weight average molecular weight in the range of 1800 to 2800. A polyether glycol having a ratio of the weight average molecular weight to the molecular weight of 1.15 or less is used. The polyurethane elastic body of the present invention exhibits excellent elongation at break and elongation recovery rate.

The method for producing a polyurethane elastic material of the present invention comprises a polyether glycol having a weight average molecular weight in the range of 1800 to 2800, and a ratio of the weight average molecular weight to the number average molecular weight of 1.15 or less and an organic compound. It is characterized in that diisocyanate is reacted to produce a prepolymer, and then it is reacted with 1,6 hexanediol and then solid-phase polymerized.

In the present invention, the polymer diol has a weight average molecular weight (Mw) in the range of 1800 to 2800, and the ratio of the weight average molecular weight to the number average molecular weight (M
A polyether glycol having a ratio of 1.15 or less is used. When the weight average molecular weight is less than 1800, the elongation at break of the polyurethane elastic body becomes low, while when the weight average molecular weight exceeds 2800, the crystallinity of the polyether glycol itself is increased and the physical properties are deteriorated. Further, if the M ratio exceeds 1.15, the yarn physical properties become unstable.
Further, at the time of forming the prepolymer, an isocyanate group is added so that the number of moles of the isocyanate group with respect to the total number of hydroxyl groups of the polyether glycol is 1.8 to 2.2, and two or more kinds of polyether glycol In the case of using, the ratio of the weight average molecular weight of the other to the polyether glycol having the smallest weight average molecular weight is preferably 1.5 or less, which makes the elongation recovery rate extremely good.

As the low molecular weight diol, ethylene glycol having a molecular weight of less than 500, 1,4 butane diol, 1,6
Hexanediol, dimethylhexanediol, xylene glycol, catechol, neopentyl glycol,
Aliphatic such as 1,4 bishydroxyethoxybenzene,
Aromatic diols may be mentioned. In the present invention, 1,6 hexanediol is usually used as a low molecular weight diol in an amount of 80 mol% or more. A polyurethane elastic body produced by using 90 mol% or more is preferable because of high elongation.

As the polyisocyanate used in the present invention, known aliphatic, alicyclic and aromatic organic polyisocyanates containing two or more isocyanate groups in the molecule, particularly 4,4'- Examples thereof include diphenylmethane diisocyanate, p-phenylene diisocyanate, toluylene diisocyanate, and 1,5 naphthylene diisocyanate.

As a method for polymerizing a polyurethane elastic material, there is one called a one-shot method. When this method is used, a mixture of a high molecular diol and a low molecular diol and an organic diisocyanate are reacted at a time, so that it is highly efficient. A homogeneous polyurethane elastic body cannot be obtained due to the difference in reactivity between the molecular diol and the low molecular diol. However, in the present invention, since the prepolymer method in which the organic diisocyanate and the polymeric diol are reacted in advance is adopted, a homogeneous polyurethane elastic body can be easily obtained. The prepolymer and the low molecular weight diol are polymerized by bulk melt polymerization using, for example, a screw type extruder. Next, if necessary, solid-state polymerization may be carried out in the form of pellets in a nitrogen stream at 70 to 100 ° C. for 5 to 30 hours.

The weight average molecular weight (Mw) of the polyurethane of the present invention is generally 50,000 to 500,000, preferably 20.
Those in the range of 10,000 to 450,000 are easy to mold such as melt spinning. Those having a weight average molecular weight of about 200,000 or less are subjected to solid-state polymerization, if necessary, to about 300 to 500,000, and then subjected to melt extrusion molding such as melt spinning.

The high-molecular diol, low-molecular diol, and organic diisocyanate are used in a molar ratio (K) of isocyanate groups to hydroxyl groups of all polyols of 1.8.
To 2.2, and the molar ratio (L) of the low molecular weight diol to the isocyanate groups remaining in the prepolymer is preferably 0.49 to 0.51. When the K value and the M value are out of this range, it is difficult to obtain satisfactory physical properties for the polyurethane elastic body produced.

[0013]

The present invention will be described in detail with reference to the following examples. The low molecular diols used are shown in Table 1 by abbreviations.

[0014]

[Table 1]

The obtained polyurethane was evaluated by the following methods. Molecular weight Waters 710 type fully automatic sample processor, Waters 590 multipurpose pump, Weight
rs type 481 wavelength tunable ultraviolet detector, Showa Denko K
Using gel permeation chromatography equipped with a -80M and KD-802 type packed column, dimethylformamide is used as a solvent, and the absorption intensity at 0.35% by weight, a column temperature of 50 ° C, and an ultraviolet ray of 280 nm is measured. Polystyrene (weight average molecular weight = 1,951, 4, 4,
000, 20,800, 33,000, 111,000, 22
5,300, 498,000, 867,000, 2,610,00
0) was used. The number average molecular weight and the weight average molecular weight of the measured sample are equivalent to those of standard polystyrene. Elongation at break Tensile properties were measured using TENSILON RTA-100 manufactured by Orientec. The measurement was carried out at a room temperature of 23 ° C. and a humidity of 65% at a sample length of 5 cm and a tensile speed of 20 mm / min. In the present invention, when the polyurethane elastic body is a fiber having a denier of 200 (a modifier such as a heat-resistant agent or a crosslinking agent is not added), the content is preferably 950% or more. Elongation recovery rate The 100% expansion and contraction of the polyurethane elastic fiber was repeated twice, and the stress at the time of recovery at the elongation rate of 50% was measured at the second time, and the stress at the time of recovery was evaluated.
In the present invention, when the polyurethane elastic body is a fiber having a denier of 200 (a modifier such as a heat-resistant agent or a cross-linking agent is not added), it is preferably 80% or more. Hot water resistance 200 denier fiber stretched 100% is evaluated by elongation when immersed in hot water at 100 ° C. for 30 minutes. In the present invention, it is preferably 45% or less.

Examples 1 to 5 and Comparative Examples 1 to 3 PTMG was used as the high molecular diol and HD was used as the low molecular diol. 2.0, L
Ratio 0.5). First, after mixing PTMG and MDI with a high-speed mixer, in a control tank equipped with a stirrer, under a nitrogen atmosphere at 90 ° C.
React for 1 hour. After this, HD is added, 45 mm
Polymerization was carried out with a φ twin screw type extruder, discharged from a 2.4 mmφ 2-hole die with an average residence time of 4 minutes, and pelletized with an underwater pelletizer. In Examples 4 and 5, equimolar amounts of PTMG having different weight average molecular weights were used.

A solid-phase polymerized polymer was prepared according to a conventional method to give 20
After vacuum drying for 80 hours to obtain a water content of 80 ppm or less, melt spinning was performed with a spinning machine at a spinning speed of 100 m / min to obtain polyurethane elastic fibers of 200 denier. Various physical properties of this polyurethane elastic fiber were measured, and the results are shown in Table 2.

[0018]

[Table 2]

Examples 6 and 7, Comparative Examples 4 and 5 As polymer diol, Mw / M ratio = 2000 / 1.12
A polyurethane elastic body and fibers thereof were produced in the same manner as in Example 2 except that the low molecular weight diol was changed by using PTMG. The results are shown in Table 3. In Example 6, 10 mol% of BHEB was used together for the purpose of improving hot water resistance.

[0020]

[Table 3]

Examples 8-10 Except that the molar ratio of isocyanate groups to hydroxyl groups (K ratio) of all polyols and the molar ratio of low molecular diols to isocyanate groups remaining in the prepolymer (M ratio) were changed. In the same manner as in 6, a polyurethane elastic body and its fiber were manufactured. The results are shown in Table 4.

[0022]

[Table 4]

[0023]

As is clear from the above results, according to the present invention, it is possible to obtain a polyether polyurethane elastic body having excellent elongation recovery and elongation at break and its fiber.

Claims (3)

[Claims] 1. A thermoplastic polyurethane elastic body using 1,6 hexanediol as a low molecular weight diol, wherein the weight average molecular weight is in the range of 1800 to 2800, and the ratio of the weight average molecular weight to the number average molecular weight. A polyurethane elastic body characterized by using a polyether glycol having a ratio of 1.15 or less. 2. A weight average molecular weight of 1800 to 2800.
And a ratio of the weight average molecular weight to the number average molecular weight of 1.15 or less is reacted with an organic diisocyanate to form a prepolymer, and then 1,6 hexanediol is added. A method for producing a polyurethane elastic body, which comprises reacting and then solid-phase polymerizing. 3. A polyurethane elastic fiber comprising the polyether elastic body according to claim 1.