JPH11292946A - Production of granulated material of thermoplastic polyurethane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a thermoplastic polyurethane scarcely generating an outgas or a low-molecular weight substance and effectively usable as a molding material for parts of electrical and electronic devices, or the like. SOLUTION: A prepolymer reaction of a polyol with a diisocyanate in an excessive molar amount is carried out under pressurized conditions of an inert gas. The prepolymer reaction is continued under conditions of a reduced pressure from the time when a theoretical NCO% attains. A urethanizing reaction is then conducted with a chain extender and the resultant hot cured urethanized material is subsequently granulated with an extruder while carrying out suction under conditions of a reduced pressure to produce the granulated material of the thermoplastic polyuerthane.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a granulated thermoplastic polyurethane. More specifically, the present invention relates to a method for producing a thermoplastic polyurethane granulated product having a small amount of outgassing and low molecular weight substances.

[0002]

2. Description of the Related Art Thermoplastic polyurethane has high strength and abrasion resistance, and has been used as a raw material for various sealing products and cushion rubbers. And its production is performed by a series of steps of hardening and grinding by a prepolymer method or a one-shot method using a polyol, a diisocyanate and a chain extender, and then re-melting and molding by an injection molding machine as it is. A method or a method of granulating with an extruder and then melting and molding with an injection molding machine is applied.

[0003] The thermoplastic polyurethane obtained by such a method should have been capable of being crushed and formed. However, it has recently been formed into a gasket, a stopper, a roller or the like which is applied to micro-precision electric / electronic parts. In some cases, outgassing and low molecular weight substances generated from thermoplastic polyurethane often cause malfunctions and malfunctions of electric and electronic devices.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a thermoplastic polyurethane which produces a small amount of outgas and low molecular substances and can be effectively used as a molding material for parts of electric and electronic equipment. Is to do.

[0005]

SUMMARY OF THE INVENTION The object of the present invention is as follows.
An excess molar amount of diisocyanate is prepolymerized to the polyol under the pressurized condition of inert gas.After the theoretical NCO%, the prepolymer reaction is continued under reduced pressure, and then the urethanization reaction is performed with a chain extender. This is achieved by producing a thermoplastic polyurethane granulated product by granulating the obtained thermoset product of the urethane product using an extruder while suctioning under reduced pressure conditions.

[0006]

DETAILED DESCRIPTION OF THE INVENTION The production of thermoplastic polyurethanes
It is performed by a prepolymer method. As the polyol component, polyester polyol, polyether polyol, polycarbonate polyol and the like are used.
Polyester polyols include well-known condensation reaction products of dicarboxylic acids and polyols, polycaprolactone polyols, and the like.Polyether polyols include, for example, polytetramethylene glycol, and polycarbonate polyols include, for example, poly Hexamethylene carbonate ether, polytetramethylene carbonate ether and the like are used.
Their molecular weight ranges from about 800 to 2500. For example, about 1500 to 2500 for polycaprolactone polyol and about 800 to 1200 for polyoxytetramethylene glycol.

As the diisocyanate as another reaction component, aromatic diisocyanates such as tolidine diisocyanate, 4,4′-diphenylmethane diisocyanate, p-phenylene diisocyanate, and 1,5-naphthylene diisocyanate, from the viewpoint of mechanical properties. Isophorone diisocyanate, hydrogenated xylylene diisocyanate,
An alicyclic diisocyanate such as hydrogenated 4,4'-diphenylmethane diisocyanate is used, and an aromatic diisocyanate is preferably used. In these diisocyanates, the isocyanate group is approximately equal to the hydroxyl group of the polyol.
It is used in an excess of 2 to 12 times, preferably about 3 to 9 times in molar ratio.

[0008] In the prepolymer reaction between the polyol and the excess molar amount of diisocyanate, firstly under pressure under an inert gas such as nitrogen, argon or the like, generally about 0.
The reaction is carried out under a pressurized condition of 3 to ² kg / cm ² , preferably about 0.5 to 1.0 kg / cm ² until the theoretical NCO% is reached (until the theoretically considered 100% reaction). At this time, while performing heat exchange, the maximum temperature during the reaction is about 110 ° C. or less, preferably about 95 ° C.
Keep to ~ 105 ° C. When the temperature of the reaction system becomes almost constant, the pressure of the reaction system is gradually returned to normal pressure, and then reduced pressure, generally about 750 mmHg or more, preferably about 755 to 760 mmH
The degree of vacuum is reduced to g, and the prepolymer reaction is further continued for about 60 to 90 minutes.

Next, a chain extender is added to the prepolymer thus formed, and the mixture is stirred for about 40 to 60 seconds, and then poured on a hot plate at about 100 to 120 ° C. to be cured.

As the chain extender, ethylene glycol,
Low molecular weight aliphatic diols such as 1,4-butanediol, 1,6-hexanediol, 2,3-butanediol, glycerin monoallyl ether, p-phenylenediene (β-hydroxyethyl ether), p-xylylene glycol , An aromatic or alicyclic diol such as cyclohexanediol, an aliphatic diamine such as ethylenediamine used in combination therewith, or 3,3′-dichloro-4,4′-diaminodiphenylmethane, diethyltoluylenediamine, N, N Aromatic diamines such as' -diaminopiperidine, and low molecular weight aliphatic triols such as glycerin, trimethylolpropane, and trimethylolethane are used.

The thermosetting product of the obtained urethane compound is pulverized and granulated by an extruder, and extruded from near the extruder head while melting and kneading using a single-screw or twin-screw extruder, and granulated. At this time, the granulation is carried out under reduced pressure, while suctioning generally under a reduced pressure of about 700 mmHg or more, preferably about 720 to 740 mmHg.

Molding using the obtained granules is performed by heating at about 80 to 125 ° C. for about 12 to 48 hours using an injection molding machine.

[0013]

According to the method of the present invention, by-products, dimerized isocyanates, a small amount of halides, and low polyols contained in the raw material polyol used in the two stages of the prepolymer reaction stage and the granulation process. Since it can effectively remove molecular substances, etc., when parts molded from the obtained thermoplastic polyurethane are mounted on various precision electrical and electronic equipment, there is a fatal adverse effect on the functions of these equipment. Effectively prevented. In addition, since the metal corrosion component contained in the thermoplastic polyurethane is effectively removed, the function of the device can be sufficiently maintained from this aspect.

[0014]

Next, the present invention will be described by way of examples.

Example 1 Polycaprolactone diol heated to 125 ° C. (MW 2000, O
To 100 parts of H value (56.1) (weight, the same applies hereinafter), add 60 parts of trizine diisocyanate (MW264) (about 4.5 times the NCO group to OH), pressurize to 0.7 kg / cm ² with nitrogen gas, and pressurize. The polymer was reacted. At the start of the reaction, external heating is required, but the temperature rise at that
° C or lower, and when the theoretical NCO% (in this case, 9.31%) is reached, 80 ° C at a reduced pressure of 755 mmHg
The prepolymer reaction was continued for a minute.

Next, 13.7 parts of 1,4-butanediol was added, and the mixture was stirred for about 40 to 60 seconds and poured on a hot plate (about 115 to 120 ° C.) to be cured. This is crushed, and it is
Melting was performed at around 0 ° C., and granulation was performed while suction was performed at a reduced pressure of 720 mmHg from the vicinity of the extruder head while kneading.

The granulated urethane composition is injected into an injection molding machine (nozzle 225 ° C., cylinder 215 ° C., 205 ° C. under hopper).
Was used to form a sheet (25 × 125 × 2 mm), which was further annealed at about 120 to 125 ° C. for 24 hours.

Comparative Example 1 In Example 1, the pressure reduction after reaching the theoretical NCO% during the prepolymer reaction was not performed.

Comparative Example 2 In Example 1, no decompression was performed during granulation by an extruder.

Example 2 While heating 100 parts of polytetramethylene glycol (OH value: 114) to 80 ° C., p-phenylene diisocyanate (M
W160) 27 parts were added, and the same prepolymer reaction as in Example 1 was performed.From the time when the theoretical NCO% (in this case, 4.44%) was reached, 7 parts were added.
The prepolymer reaction was continued at a reduced pressure of 50 mmHg for 60 minutes.

Then, 11.7 parts of p-phenylene (β-hydroxyethyl) ether was added, and a urethanization reaction, granulation, and forming into a sheet were carried out in the same manner as in Example 1.

Comparative Example 3 In Example 2, neither reduced pressure after reaching the theoretical NCO% during the prepolymer reaction nor reduced pressure during granulation by an extruder was performed.

The following items were measured for the sheets obtained in the above Examples and Comparative Examples. Physical property value: JIS K-6301 compliant Outgas test: 2 x 5 x 2 mm measurement specimen (about 4
g) was cut out and precisely weighed into a vial having a capacity of 22 ml. After the inside was purged with nitrogen gas, it was sealed and left in an oven adjusted to a temperature of 125 ° C. for 48 hours. The gas generated in the vial was qualitatively and quantitatively determined by gas chromatography and gas chromatograph mass spectrometer, and the total amount of outgas was calculated. Silver flake corrosion test: Put two sheets cut out to a size of 10 × 10 × 2 mm in a weighing bottle, one of them is set in contact with silver flakes, and the other one is After the stainless steel mesh was sandwiched between the sheet and the silver piece, it was set and covered, and then left at 100 ° C. for 90 hours, and the blackness of the silver piece surface was visually observed. No discoloration was indicated by ○, slight blackening was indicated by Δ, and blackening was indicated by ×. Measurement of chlorine, bromine, phosphorus, and sulfur content: Three sheets cut into a size of 30 x 110 x 2 mm were immersed in 150 ml of pure water, subjected to ultrasonic extraction for 10 minutes, and the extract was subjected to ion chromatography. subjected to chromatography ^{analysis, Cl -, Br -, PO4} ---, SO4
^- the average was calculated as.

The results obtained are shown in the following table. tableMeasurement and evaluation items Real-1 Ratio -1 Ratio-2 Real-2 Ratio -3  [Physical properties] Hardness (JIS A) 95 95 95 96 95 100% modulus (MPa) 12.0 12.0 12.5 14.5 14.0 Tensile strength (MPa) 53.5 52.0 53.0 60.0 58.5 Elongation (%) 510 550 530 690 720 Tear strength ( (KN / m) 125 120 125 145 140 Compression set (%) 27 32 30 22 25 [Outgassing test] Total outgassing (μg / g) 3.7 29.7 37.5 4.1 89.7 Contact state ○ △ △ ○ × Non-contact state ○ ○ ○ ○ × [Chlorine, bromine, phosphorus, sulfur content] Cl^- (× 10^-3(μg / ml) <7 17 12 <5 27 Br^- (× 10^-3μg / ml) <5 <5 <5 <5 <11 PO_Four ^--- (× 10^-3(μg / ml) <13 <13 <13 <7 <13 SO_Four ^- (× 10^-3(μg / ml) <11 <11 <11 <11 17

Claims (1)

[Claims] 1. A polyol is subjected to a prepolymer reaction of an excess molar amount of diisocyanate with a polyol under a pressurized condition of an inert gas, and the prepolymer reaction is continued under a reduced pressure condition when the theoretical NCO% is reached, followed by chain extension. A method for producing a thermoplastic polyurethane granulated product, comprising subjecting a thermosetting product of an obtained urethane product to a urethanization reaction with an agent and granulating the same using an extruder while suctioning under reduced pressure conditions.