JP2010195868A - Foamed polyurethane and method for producing the same, and mounting member made of urethane composed of foamed polyurethane - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide: a foamed polyurethane excellent in hydrolysis resistance and setting resistance; to provide a method for producing the foamed polyurethane; and to provide a mounting member made of urethane composed of the foamed polyurethane. <P>SOLUTION: An unreactive gas dissolved thermoplastic polyurethane composition is obtained by mixing a thermoplastic polyurethane composition containing: a thermoplastic polyurethane synthesized with at least one polyol of polyether-base polyols, polylactone-based polyols and polycarbonate-based polyols, and a polyisocyanate as essential components; and an isocyanate-terminated prepolymer synthesized with a polyether-based polyol and a polyisocyanate as essential components in a molten state, with an unreactive gas in a supercritical state. Then, the foamed polyurethane is made by injection molding the unreactive gas-dissolved thermoplastic polyurethane composition into a die. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a foamed polyurethane excellent in hydrolysis resistance and settling resistance, a method for producing the same, and a urethane mounting member made of the foamed polyurethane.

  For example, in an automobile suspension, in order to elastically regulate the amount of displacement generated between a vehicle body and a wheel, a mounting device including a mounting member made of an elastic body is provided. As rubber, rubber is generally used. However, in recent years, polyurethane foam tends to be used as such an elastic body from the viewpoint of reducing the weight of the mounting device and preventing abnormal noise generated when the mounting member is compressed and deformed.

  In general, foamed polyurethane is obtained by foaming and curing a composition containing a polyester-based polyol, polyisocyanate, and a foaming agent as raw materials. However, when foamed polyurethane synthesized with polyester-based polyol as an essential component is used as a mounting member, polyurethane foam tends to undergo hydrolysis over time due to the adhesion of water during traveling and the influence of moisture in the air. As a result, the elastic properties of the polyurethane foam deteriorated, and further, there was a tendency to break.

  In the following Patent Document 1, the foamed urethane was obtained by foaming and curing a foamable composition having a fluorine-based water repellent as an essential component in addition to a polyester-based polyol, a polyisocyanate, and a foaming agent. A foamed polyurethane is described. This foamed polyurethane has the greatest feature that a fluorine-based water repellent is used as an essential component. With such a configuration, the invention described in Patent Document 1 improves the hydrolysis resistance of the foamed polyurethane. The purpose is that. However, the urethane foam described in Patent Document 1 is still susceptible to hydrolysis because it contains a polyester-based polyol as an essential component.

JP 2004-293697 A

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a foamed polyurethane excellent in hydrolysis resistance and sag resistance, a method for producing the same, and a urethane mounting member composed of the foamed polyurethane. There is to do.

  As a result of intensive studies to solve the above problems, the present inventors have found that the above object can be achieved by the foamed polyurethane shown below, and have completed the present invention.

  That is, the polyurethane foam according to the present invention is a non-reactive gas-dissolved thermoplastic polyurethane composition obtained by mixing a non-reactive gas in a supercritical state with a molten thermoplastic polyurethane composition, and injection-molded into a mold. The thermoplastic polyurethane composition is obtained by synthesizing at least one of a polyether-based polyol, a polylactone-based polyol and a polycarbonate-based polyol, and a polyisocyanate as essential components. It contains polyurethane and an isocyanate-terminated prepolymer synthesized with polyether-based polyol and polyisocyanate as essential components.

  Since the foamed polyurethane is obtained from a thermoplastic polyurethane composition containing a thermoplastic polyurethane and an isocyanate-terminated prepolymer that acts as a crosslinking agent, a three-dimensional crosslinked structure appears in the foamed polyurethane. As a result, the polyurethane foam according to the present invention is excellent in the settling resistance. In addition, the thermoplastic polyurethane is synthesized using at least one of a polyether polyol, a polylactone polyol and a polycarbonate polyol, and a polyisocyanate as essential components, and the isocyanate-terminated prepolymer comprises a polyether polyol and a polyisocyanate. Since it is synthesized as an essential component, the foamed polyurethane obtained using a thermoplastic polyurethane composition containing these as raw materials is excellent in hydrolysis resistance. Furthermore, the polyurethane foam according to the present invention is a non-reactive gas-dissolved thermoplastic polyurethane composition obtained by mixing a non-reactive gas in a supercritical state with a molten thermoplastic polyurethane composition. Therefore, the foamed state is uniform and has a high bubble rate.

  In the foamed polyurethane, when the number of urethane bonds (mol / kg) in the thermoplastic polyurethane is U and the number of isocyanate groups (mol / kg) in the isocyanate-terminated prepolymer is I, 0.01 ≦ I / U ≦ It is preferable that it is 0.2. When I / U is less than 0.01 or more than 0.2, the obtained polyurethane foam may deteriorate in the sag resistance. In order to further improve the settling resistance of the foamed polyurethane, it is preferable that 0.05 ≦ I / U ≦ 0.15.

  In the foamed polyurethane, it is preferable that a mixing amount of the non-reactive gas with respect to the thermoplastic polyurethane composition is 0.01 to 5% by weight. When the mixing ratio of the thermoplastic polyurethane composition and the non-reactive gas is within the above range, the polyurethane foam has a desired specific gravity and is reduced in weight. Specifically, the specific gravity is 0.4 to 0.8. A foamed polyurethane is obtained.

  Moreover, the urethane mount member according to the present invention is composed of the polyurethane foam described above. As described above, since the polyurethane foam according to the present invention is excellent in hydrolysis resistance and sag resistance, the urethane mount member according to the present invention is also excellent in hydrolysis resistance and sag resistance. As a result, the urethane mount member according to the present invention has excellent durability.

  Further, the method for producing a foamed polyurethane according to the present invention comprises a melting step of heating the thermoplastic polyurethane composition to a molten state, and mixing the non-reactive gas in a supercritical state with the thermoplastic polyurethane composition in the molten state. A process for producing a foamed polyurethane comprising: a dissolving step for forming a non-reactive gas-dissolving thermoplastic polyurethane composition; and an injection-molding step for injection-molding the non-reactive gas-dissolving thermoplastic polyurethane composition into a mold. The thermoplastic polyurethane composition comprises a polyether-based polyol, a polylactone-based polyol and a polycarbonate-based polyol, and a thermoplastic polyurethane synthesized with polyisocyanate as an essential component, and a polyether-based polyol and a polyisocyanate. Synthesized as an essential ingredient And isocyanate-terminated prepolymers, characterized in that it contains.

  In general, when an unfoamed polyurethane is produced by injection molding a thermoplastic polyurethane composition containing a thermoplastic polyurethane and an isocyanate-terminated prepolymer that acts as a cross-linking agent, the injection pressure at the time of injection molding has elapsed over time. As the pressure rises, the injection pressure tends to increase to a region where injection is impossible. For this reason, the injection molding of the thermoplastic polyurethane composition containing the thermoplastic polyurethane and the isocyanate-terminated prepolymer has a problem that productivity is lowered.

  In the method for producing foamed polyurethane according to the present invention, after mixing a non-reactive gas in a supercritical state with a molten thermoplastic polyurethane composition to obtain a non-reactive gas-dissolving thermoplastic polyurethane composition (dissolution step), A non-reactive gas-dissolved thermoplastic polyurethane composition is injection molded into a mold (injection molding process). Here, when the non-reactive gas is in the supercritical state in the dissolution step, the dissolution and diffusion effect on the molten thermoplastic polyurethane composition is greatly increased, and the thermoplastic polyurethane resin composition in the molten state in a short time To penetrate. As a result, the thermoplastic polyurethane resin composition can be greatly plasticized, the injection pressure at the time of injection molding can be reduced, and the productivity of the polyurethane foam can be improved. In addition, at least one kind of polyether polyol, polylactone polyol and polycarbonate polyol, and thermoplastic polyurethane synthesized with polyisocyanate as an essential component, and synthesized with polyether polyol and polyisocyanate as an essential component. By using a thermoplastic polyurethane composition containing an isocyanate-terminated prepolymer as a raw material, a foamed polyurethane excellent in hydrolysis resistance and settling resistance can be produced.

  In the manufacturing method described above, the urethane mount member can be easily manufactured by designing the mold so that the foamed polyurethane has a desired shape.

(A) The figure showing the durability evaluation method, (b) The figure showing the shape of the durability evaluation sample

  The foamed polyurethane according to the present invention is obtained by injection-molding a non-reactive gas-dissolved thermoplastic polyurethane composition obtained by mixing a non-reactive gas in a supercritical state into a molten thermoplastic polyurethane composition into a mold. Is obtained. The thermoplastic polyurethane composition comprises at least one of a polyether polyol, a polylactone polyol and a polycarbonate polyol, and a thermoplastic polyurethane synthesized with polyisocyanate as an essential component, and a polyether polyol and polyisocyanate as essential components. And an isocyanate-terminated prepolymer synthesized as a component.

  Examples of the polyether-based polyol include polypropylene glycol, polytetramethylene glycol, and polyhexamethylene glycol. Examples of the polylactone-based polyol include polycaprolactone glycol, polypropiolactone glycol, and polyvalerolactone glycol. Polycarbonate polyols include polyols obtained by dealcoholization reaction of polyhydric alcohols such as ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, octanediol, and nonanediol with diethylene carbonate, dipropylene carbonate, and the like. Can be mentioned. These polyether polyols, polylactone polyols or polycarbonate polyols can be used alone or in admixture of two or more.

  Examples of the polyisocyanate include diphenylmethane diisocyanate, toluene diisocyanate, naphthalene diisocyanate, dimethyldiphenyl diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, phenylene diisocyanate, dicyclohexylmethane diisocyanate, xylene diisocyanate, and isophorone diisocyanate. These polyisocyanates can be used alone or in admixture of two or more polyisocyanates.

  The thermoplastic polyurethane may be synthesized from a composition containing other polyols, chain extenders and the like as optional components in addition to the above essential components. However, in order to improve the hydrolysis resistance of the polyurethane foam, it is preferably synthesized from a composition containing no adipate polyol.

  As the chain extender, a bifunctional chain extender having active hydrogen at both ends is used. Specifically, ethylene glycol, propylene glycol, 1,4-butanediol, 1,3-butanediol, 1,6-hexanediol, 3-methyl 1,5-pentanediol, neopentyl glycol, methyloctanediol, Aliphatic diols such as 1,9-nonanediol; alicyclic diols such as 1,4-cyclohexanediol; 1,4-bis (β-hydroxyethoxy) benzene, hydroquinone, resorcin, chlorohydroquinone, bromohydroquinone, Methylhydroquinone, phenylhydroquinone, methoxyhydroquinone, phenoxyhydroquinone, 4,4'-dihydroxybiphenyl, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl sulfide, 4,4'-dihydroxydipheni Sulfone, 4,4′-dihydroxybenzophenone, 4,4′-dihydroxydiphenylmethane, bisphenol A, 1,1-di (4-hydroxyphenyl) cyclohexane, 1,2-bis (4-hydroxyphenoxy) ethane, 1,4 -Aromatic diols such as dihydroxynaphthalene and 2,6-dihydroxynaphthalene. These chain extenders can be used alone or in admixture of two or more chain extenders.

  Examples of the isocyanate-terminated prepolymer include those synthesized using a polyether-based polyol and a polyisocyanate as essential components, and the same ones as described above can be used as the polyether-based polyol and polyisocyanate. Here, the number average molecular weight of the isocyanate-terminated prepolymer is preferably 3000 or less, and more preferably 2000 or less. When the number average molecular weight exceeds 3000, the settling resistance of the polyurethane foam may deteriorate. On the other hand, the lower limit of the number average molecular weight of the isocyanate-terminated prepolymer is not particularly limited, but is preferably a certain number average molecular weight in a solid state at room temperature, specifically 550 or more.

  In the present invention, when the number of urethane bonds (mol / kg) in the thermoplastic polyurethane is U and the number of isocyanate groups (mol / kg) in the isocyanate-terminated prepolymer is I, 0.01 ≦ I / U ≦ 0.2 It is preferable that When I / U is less than 0.01 or more than 0.2, the obtained polyurethane foam may deteriorate in the sag resistance. In addition, when I / U exceeds 0.2, the injection pressure at the time of injection molding rises to a region where injection is impossible, and foamed polyurethane productivity may deteriorate. In order to further improve the settling resistance of the foamed polyurethane, it is preferable that 0.05 ≦ I / U ≦ 0.15.

  In addition to the above-mentioned thermoplastic polyurethane and isocyanate-terminated prepolymer, the thermoplastic polyurethane composition includes, as necessary, other thermoplastic resins other than polyurethane, plasticizers, dispersants, compatibilizing agents, and crosslinking agents. , Crosslinking aids, process oils, pigments, antioxidants, reinforcing materials, colorants, hydrolysis inhibitors, foam stabilizers and the like.

  Thermoplastic resins include polystyrene, butadiene-styrene copolymer, acrylonitrile-styrene copolymer, acrylonitrile-butadiene-styrene copolymer, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, polybutene, polycarbonate, polyacetal, polyphenylene. Examples thereof include sulfide, polyphenylene ether, polyphenylene oxide, polyvinyl alcohol, polymethyl methacrylate, polyester, polyamide, polyimide, polyether sulfone, and polyether ether ketone. When the thermoplastic resin is used together with the thermoplastic polyurethane, it is preferable that the content of the thermoplastic resin is 20 parts by weight or less with respect to 100 parts by weight of the thermoplastic polyurethane in order to maintain good properties of the polyurethane. More preferably, it is 10 parts by weight or less.

  By the way, the present inventors diligently studied the relationship between the thickness of the foamed polyurethane skin layer and the hydrolysis resistance of the foamed polyurethane. When the skin layer is thin, the foamed polyurethane is easily hydrolyzed and is not resistant to hydrolysis. It was found that the degradability deteriorated. Therefore, the polyurethane foam according to the present invention is preferably one having a skin layer thickness of 50 μm to 150 μm because the hydrolysis resistance is particularly excellent. A method for producing a foamed polyurethane having such a skin layer thickness will be described later.

Here, in the present invention, the “skin layer thickness” of the polyurethane foam is measured by the following method.
a) Arithmetic average roughness (hereinafter referred to as “Ra”) in a cut surface obtained by cutting foamed polyurethane perpendicularly to the surface with a sharp blade at intervals of 10 μm from the surface of foamed polyurethane (thickness direction). Then, the measurement is sequentially performed from the surface to the 1.5 mm thickness position. Ra is measured with a non-contact high-speed three-dimensional shape measurement system (MAP-3D (manufactured by COMMS)) in a 1 mm long cross-sectional shape parallel to the polyurethane foam surface at an arbitrary thickness position (n = 5). And calculating by averaging.
b) Ra is measured at a thickness position of 1.5 mm from the surface of the polyurethane foam (this measured value is referred to as “reference Ra”).
c) Sample surface in a thickness position where Ra measured at intervals of 10 μm (thickness positions 10 μm, 20 μm...) in the vertical direction (thickness direction) from the foamed polyurethane surface is 0.3 × (reference Ra) or less. The thickness up to the thickness position farthest from is defined as the thickness of the skin layer.

  In addition, in order to further improve the hydrolysis resistance of the polyurethane foam, the closed cell rate of the polyurethane foam is preferably 70 to 98%, and more preferably 75 to 95%.

  The method for producing a polyurethane foam according to the present invention includes a melting step of heating a thermoplastic polyurethane composition to a molten state, and mixing a non-reactive gas in a supercritical state with the molten thermoplastic polyurethane composition to perform a non-reaction. The melt | dissolution process which makes a reactive gas melt | dissolution thermoplastic polyurethane composition, and the injection molding process of injection-molding a non-reactive gas melt | dissolution thermoplastic polyurethane composition to a metal mold | die are included. Hereinafter, each process will be described with reference to an example of manufacturing by injection molding.

(Melting process)
First, in the melting step, the thermoplastic polyurethane composition is brought into a molten state by heating. Specifically, the thermoplastic polyurethane composition is fed into a resin melting cylinder of an injection molding machine from a hopper or the like, and a temperature equal to or higher than the melting point or the plasticizing temperature of the thermoplastic polyurethane composition, specifically 160 to A molten state is obtained by heating at a temperature of 240 ° C.

(Dissolution process)
Next, a non-reactive gas in a supercritical state is mixed with the molten thermoplastic polyurethane composition in the melting step to obtain a non-reactive gas-dissolved thermoplastic polyurethane composition. Specifically, a non-reactive gas such as nitrogen gas or carbon dioxide gas in a supercritical state is mixed with a thermoplastic polyurethane composition kept in a molten state in a resin melting cylinder of an injection molding machine, and non-reactive. Gas soluble thermoplastic polyurethane composition. For example, a non-reactive gas in a supercritical state is injected into a metering pump from a cylinder storing non-reactive gas in a liquefied (or vaporized) state, and the pressure is increased in the metering pump. And mixed with the thermoplastic polyurethane composition kept in a molten state. At this time, if the non-reactive gas present in the resin melting cylinder is in the supercritical state, the melt diffusion effect on the thermoplastic polyurethane composition in the molten state is greatly enhanced, and the thermoplastic polyurethane resin in the molten state in a short time Penetrates into the composition. In the melting step, the set temperature in the resin melting cylinder of the injection molding machine may be set to 165 to 245 ° C in order to keep the temperature of the non-reactive gas-melting thermoplastic polyurethane composition within the range of 160 to 240 ° C. preferable.

  In the dissolving step, the mixing amount of the non-reactive gas with respect to the thermoplastic polyurethane composition is preferably 0.01 to 5% by weight, and more preferably 0.05 to 3% by weight. According to this production method, a foamed polyurethane having a desired specific gravity, specifically, a foamed polyurethane having a specific gravity of 0.40 to 0.8 can be obtained.

(Injection molding process)
Next, in the injection molding process, the non-reactive gas-dissolved thermoplastic polyurethane composition is injection molded into a mold. Specifically, the non-reactive gas-dissolved thermoplastic polyurethane composition present in the resin melting cylinder of the injection molding machine is fed into, for example, an injection apparatus equipped with an injection plunger, and weighed by such an injection apparatus. Injection into the mold. In the production method according to the present invention, the injection amount of the non-reactive gas-dissolving thermoplastic polyurethane composition in the injection molding step and the mixing amount of the non-reactive gas in the non-reactive gas-dissolving thermoplastic polyurethane composition are adjusted. By doing, the foaming urethane which has arbitrary specific gravity and foaming magnification can be manufactured.

  In the present invention, it is preferable that the non-reactive gas-dissolving thermoplastic polyurethane composition in the melting step is in the range of 160 to 240 ° C., and the mold temperature in the injection molding step is in the range of 20 to 50 ° C. . When the temperature condition is set in this way, the non-reactive gas-dissolving thermoplastic polyurethane composition is foamed as the non-reactive gas in the non-reactive gas-dissolving thermoplastic polyurethane composition is vaporized. A urethane mounting member composed of a foamed polyurethane with a skin layer having a sufficient thickness when the composition is rapidly cooled in a mold, specifically, a thickness of 50 μm to 150 μm, preferably 100 to 150 μm. A foamed polyurethane having a certain skin layer and improved hydrolysis resistance can be produced.

  When the mold temperature in the injection molding process is less than 20 ° C., the fluidity of the non-reactive gas-dissolved thermoplastic polyurethane composition injected into the mold deteriorates, and the surface of the foamed polyurethane skin layer is roughened. There is a tendency for voids to occur in the polyurethane foam. On the other hand, when the mold temperature in the injection molding process exceeds 50 ° C., the skin layer thickness of the polyurethane foam tends to be thin. In order to more reliably adjust the thickness of the foamed polyurethane skin layer within a desired range, it is preferable that the mold temperature in the injection molding step be within a range of 30 to 45 ° C.

  Hereinafter, examples and the like specifically showing the configuration and effects of the present invention will be described. In addition, various physical properties of the polyurethane foam were evaluated as follows.

(1) Self-foaming ratio Foamed polyurethane was cut out in a sample shape of 20 × 20 × 25 mm so as not to include a skin layer, and measured using an air comparison type hydrometer 930 type (manufactured by Beckman). The single bubble rate was calculated from the following formula based on the counter value obtained by measurement and the sample volume value.
(Cell rate (%)) = 100 × (counter value) / (sample volume value)

(2) Moisture content The foamed polyurethane was cut out in a sample shape of 20 × 20 × 25 mm so as not to include a skin layer, and the weight of the sample was measured, and then immersed in water for 24 hours. Thereafter, the sample was taken out of water, and water droplets on the sample surface were wiped off to measure the weight. Based on the weight before and after immersion in water, it was calculated from the following formula.
(Moisture content (%)) = 100 × ((weight after immersion) − (weight before immersion)) / (weight before immersion)
(3) Specific gravity Foamed polyurethane was cut out in a cylindrical shape having a diameter of 30 mm and a thickness of 12.5 mm so as not to include a skin layer, and measured using a Sartorius-LA230S.

(4) Hydrolysis resistance (half life of tensile strength retention due to wet heat degradation)
A foamed polyurethane sample (sheet shape without a skin layer of 100 × 50 × 3 mm) was placed in a thermostatic chamber at a temperature of 80 ° C./humidity of 95% for 168 hours (1 week), 504 hours (3 weeks), 1008 Time (6 weeks), 2016 hours (12 weeks), 3024 hours (18 weeks), 4032 hours (24 weeks), then removed from the thermo-hygrostat, and a tensile test is performed according to JIS K-7312. Tensile strength was measured. Calculate the retention rate of the tensile strength of the sample after curing with respect to the tensile strength measured in the sample before curing in a constant temperature and humidity chamber, create a graph of the curing time on the horizontal axis and the tensile strength retention rate on the vertical axis, The curing time (half-life of tensile strength retention rate) when the tensile strength retention rate was 50% in the curve was read. In addition, when the tensile strength retention after 4032 hour curing exceeds 50%, the half-life is set to 4000 hours or more. The longer the half life of the tensile strength retention rate of the foamed polyurethane, the more the foamed polyurethane has hydrolysis resistance.

(5) Durability (Change rate of static spring constant after wet heat degradation)
As shown in FIG. 1, two ring-shaped foamed polyurethane samples 1 (shape: outer diameter R1 = 55 mm, inner diameter R2 = 33 mm, height H = 18 mm; FIG. 1 (b)) whose static spring constant was measured in advance (1 Set) in the outer cylinder 3 with the inner cylinder 2 being sandwiched, cured for 168 hours (one week) in a thermostatic chamber at a temperature of 80 ° C./humidity of 95%, and then removed from the thermostatic chamber The static spring constant was measured when a vibration was applied 10,000 times at a load of ± 4900 N and an excitation frequency of 2 Hz. The static spring constant Ks is a deflection in a range of ± 4900 N at a displacement speed of 10 mm / min in a bidirectional load method of a static characteristic test in accordance with JIS K6385 from a state where a predetermined load is applied to room temperature. The load is applied three times, the load-deflection relationship in the third loading process is measured, and this relationship is used to calculate the deflection range = ± 980 N by the calculation method described in the same standard. Based on the static spring constant before curing and the static spring constant after curing and vibration 10,000 times, it was calculated from the following formula.
(Change rate of static spring constant after wet heat degradation (%))
= 100 × ((static spring constant after curing and vibration 10,000 times) − (static spring constant before curing)) / (static spring constant before curing)

Reference Comparative Example 1
85 parts by weight of polyethylene adipate polyester polyol (“Polylite ODX-2402”, manufactured by Dainippon Ink & Chemicals, Inc.), which is a polyester polyol, and 25 parts by weight of naphthalene diisocyanate (“Cosmonate ND”, manufactured by Mitsui Chemicals Polyurethanes) Next, 15 parts by weight of polyethylene adipate polyester polyol ("Polylite ODX-2402", manufactured by Dainippon Ink & Chemicals, Inc.) and a blowing agent ( After adding 2 parts by weight of water) and stirring, the mixture was poured into a mold set at 75 ° C. Twenty minutes after the injection, the mixture was removed and further post-cured to produce a polyurethane foam. The results of the above characteristic evaluation using such a foamed polyurethane are shown in FIG. To show.

Example 1
100 parts by weight of a thermoplastic polyurethane (“E380-MNAT”, manufactured by Nippon Polyurethane Industry Co., Ltd.) synthesized from a composition containing polytetramethylene glycol, 1,4-butanediol and diphenylmethane diisocyanate at 90 ° C. for 5 hours It was dried above. 10 parts by weight of this thermoplastic polyurethane and an isocyanate-terminated prepolymer synthesized from a composition containing polytetramethylene glycol and diphenylmethane diisocyanate (“Crosnate EM30” (number average molecular weight 1800), manufactured by Dainichi Seika Kogyo Co., Ltd.) Is melted by feeding it into a resin melting cylinder from a hopper of a MuCell type injection molding machine (manufactured by Nippon Steel Co., Ltd.) (melting process), and then supercritical nitrogen gas (non-reactive gas) is thermoplastic. The mixture was fed into a resin melting cylinder so as to be 0.1% by weight with respect to the polyurethane composition and mixed to obtain a nitrogen gas-dissolved thermoplastic polyurethane composition (dissolution step). The ratio I / U between the number of isocyanate groups (mol / kg) I in the isocyanate-terminated prepolymer and the number of urethane bonds (mol / kg) U in the thermoplastic polyurethane was 0.08. Further, the set temperature in the resin melting cylinder in the melting step was set to 200 ° C., and the temperature of the nitrogen gas-melting thermoplastic polyurethane composition at this time was 195 ° C. Further, a nitrogen gas-dissolved thermoplastic polyurethane composition at 195 ° C. was injection-molded in a mold set at 40 ° C., left for 5 minutes and then removed from the mold to produce a polyurethane foam. Table 1 shows the results of the above characteristic evaluation using such polyurethane foam. Moreover, the peak pressure (MPa) of the injection pressure at the time of injection molding was measured (n = 15). The results are shown in Table 2.

Example 2
15 weights of isocyanate-terminated prepolymer (“Crosnate EM30” (number average molecular weight 1800), manufactured by Dainichi Seika Kogyo Co., Ltd.) with respect to 100 parts by weight of thermoplastic polyurethane (“E380-MNAT”, manufactured by Nippon Polyurethane Industry Co., Ltd.) A foamed polyurethane was produced in the same manner as in Example 1 except that I / U was 0.12. Table 1 shows the results of the above characteristic evaluation using such polyurethane foam.

Example 3
As the thermoplastic polyurethane, 100 parts by weight of a thermoplastic polyurethane (“E980-PSID”, manufactured by Nippon Polyurethane Co., Ltd.) synthesized from a composition containing polyhexamethylene carbonate polyol and diphenylmethane diisocyanate was used, and an isocyanate-terminated prepolymer (“ A polyurethane foam was produced in the same manner as in Example 1 except that 15 parts by weight of Crossnate EM30 "(manufactured by Dainichi Seika Kogyo Co., Ltd.) was used and I / U was 0.139. Table 1 shows the results of the above characteristic evaluation using such polyurethane foam.

Comparative Example 1
A polyurethane foam was produced in the same manner as in Example 1 except that no isocyanate-terminated prepolymer was used (I / U = 0). Table 1 shows the results of the above characteristic evaluation using such polyurethane foam.

Comparative Example 2
30 weights of isocyanate-terminated prepolymer (“Crosnate EM30” (number average molecular weight 1800), manufactured by Dainichi Seika Kogyo Co., Ltd.) with respect to 100 parts by weight of thermoplastic polyurethane (“E380-MNAT”, manufactured by Nippon Polyurethane Industry Co., Ltd.) The foamed polyurethane was produced by the same method as in Example 1 except that the I / U was 0.241. became. Table 1 shows the results of the above characteristic evaluation using such polyurethane foam.

Comparative Example 3
As the thermoplastic polyurethane, use a thermoplastic polyurethane synthesized from a composition containing polyhexamethylene carbonate polyol and diphenylmethane diisocyanate (“E980-PSID”, manufactured by Nippon Polyurethane Co., Ltd.) and do not use an isocyanate-terminated prepolymer ( A foamed polyurethane was produced in the same manner as in Example 1 except that I / U = 0). Table 1 shows the results of the above characteristic evaluation using such polyurethane foam.

Comparative Example 4
A non-foamed polyurethane was produced in the same manner as in Example 1 except that nitrogen gas in a supercritical state was not used (the amount of non-reactive gas mixed with the thermoplastic polyurethane composition was 0% by weight). The peak pressure (MPa) of the injection pressure when the non-foamed polyurethane was injection molded was measured (n = 15). The results are shown in Table 2.

  From the results in Table 1, it can be seen that the foamed polyurethanes of Examples 1 to 3 are all excellent in hydrolysis resistance and durability. On the other hand, in the foamed polyurethane of Reference Comparative Example 1, the thickness of the skin layer was extremely thin, the hydrolysis resistance was deteriorated, and the durability was deteriorated as compared with the foamed polyurethanes of Examples 1 to 3. Moreover, since the foaming polyurethane of the comparative example 1 and the comparative example 3 did not contain the isocyanate terminal prepolymer which acts as a crosslinking agent, compared with the foaming polyurethane of Examples 1-3, durability deteriorated. In addition, when manufacturing the polyurethane foam of Comparative Example 2, the injection pressure during the injection molding gradually increased, and the productivity of the polyurethane foam deteriorated. Moreover, since the polyurethane foam of the comparative example 2 has much content of the isocyanate terminal prepolymer which acts as a crosslinking agent, compared with the polyurethane foam of Examples 1-3, durability deteriorated too.

  From the results of Table 2, when the non-foamed polyurethane of Comparative Example 4 was injection molded, the injection pressure gradually increased with time, and injection molding became impossible after the 14th shot. In addition, when the non-foamed polyurethane of Comparative Example 4 was injection molded, since the injection pressure was high on average, the injection speed could not be set high. As a result, the injection molding cycle per hour could not be accelerated, and the productivity was greatly deteriorated. On the other hand, the average value of the injection pressure at the time of injection molding the foamed polyurethane of Example 1 is 90.04 (MPa), and the injection pressure at the time of injection molding is approximately halved compared to the case of Comparative Example 4. I was able to. For this reason, the screw rotational speed in the resin melting cylinder of the injection molding machine can be maintained to some extent faster. As a result, the injection molding cycle per hour can be accelerated, and the productivity is greatly improved.

1: Ring-shaped foamed polyurethane sample 2: Inner cylinder 3: Outer cylinder

Claims (5)

A foamed polyurethane obtained by injection-molding a non-reactive gas-dissolved thermoplastic polyurethane composition obtained by mixing a molten thermoplastic polyurethane composition with a non-reactive gas in a supercritical state into a mold, ,
The thermoplastic polyurethane composition comprises a polyether-based polyol, a polylactone-based polyol and a polycarbonate-based polyol, a thermoplastic polyurethane synthesized with polyisocyanate as an essential component, a polyether-based polyol and a polyisocyanate. A foamed polyurethane comprising an isocyanate-terminated prepolymer synthesized as an essential component.   When the number of urethane bonds (mol / kg) in the thermoplastic polyurethane is U and the number of isocyanate groups (mol / kg) in the isocyanate-terminated prepolymer is I, 0.01 ≦ I / U ≦ 0.2. The foamed polyurethane according to claim 1.   The foamed polyurethane according to claim 1 or 2, wherein a mixing amount of the non-reactive gas with respect to the thermoplastic polyurethane composition is 0.01 to 5% by weight.   A urethane mounting member made of the polyurethane foam according to claim 1. A non-reactive gas-dissolving thermoplastic polyurethane composition is prepared by mixing a thermoplastic polyurethane composition into a molten state by heating, and mixing the thermoplastic polyurethane composition in a molten state with a non-reactive gas in a supercritical state. A method for producing a polyurethane foam comprising: a dissolution step; and an injection molding step of injection-molding the non-reactive gas-dissolved thermoplastic polyurethane composition into a mold,
The thermoplastic polyurethane composition comprises a polyether-based polyol, a polylactone-based polyol and a polycarbonate-based polyol, a thermoplastic polyurethane synthesized with polyisocyanate as an essential component, a polyether-based polyol and a polyisocyanate. A process for producing a foamed polyurethane comprising an isocyanate-terminated prepolymer synthesized as an essential component.

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