JP7576004B2 - Polyurethane foam and molded body thereof - Google Patents

Description

The present invention relates to polyurethane foams suitable for thermal compression molding and molded articles thereof.

Thermoplastic resins can be shaped by heating, but they have the problem of poor distortion characteristics (large distortion).
On the other hand, thermosetting resins can be shaped by pre-processing using a mold, and although post-processing is difficult, they have the advantage of good distortion characteristics (low distortion).
Furthermore, although conventional polyurethane foams can be subjected to hot compression molding at high temperatures, there is a problem in that the distortion characteristics are not very good.

JP 2009-013304 A

The present invention has been made in consideration of the above points, and aims to provide a polyurethane foam that can be thermally compressed and has good distortion characteristics, and a molded product thereof.

The invention of claim 1 is a polyurethane foam obtained by a mechanical froth method from a polyurethane reaction composition containing a polyol component, a foam stabilizer, a catalyst, and an isocyanate component, and an inert gas, wherein the polyol component contains a polymer polyol, and the polyurethane reaction composition contains an acid-modified polyolefin powder.

The invention of claim 2 is characterized in that in claim 1, the acid-modified polyolefin powder is a polyolefin powder modified with maleic anhydride.

The invention of claim 3 is characterized in that in claim 1 or 2, the total weight of the solid content of the polymer polyol and the acid-modified polyolefin powder is 5 to 40% by weight of the polyurethane reaction composition.

The invention of claim 4 is characterized in that in any one of claims 1 to 3, the compression residual set of the polyurethane foam (based on JIS 6401) is 10% or less.

The invention of claim 5 is a molded product having irregularities formed on the surface of a polyurethane foam sheet by thermal compression molding, the polyurethane foam being the polyurethane foam of any one of claims 1 to 4.

The polyurethane foam of the present invention contains a polymer polyol and an acid-modified polyolefin powder in the polyurethane reaction composition, which allows the polyurethane foam to be thermoplastically deformed at temperatures below the decomposition temperature of the polyurethane bond, and allows the foam to retain its shape during thermal compression molding while maintaining good distortion characteristics.

The polyurethane foam molded article of the present invention can provide a sheet-like molded article with good distortion characteristics that can maintain the surface irregularities formed by thermal compression molding.

FIG. 1 is a plan view showing one embodiment of a molded article of a polyurethane foam. 2 is a cross-sectional view showing the cross section 2-2 of FIG. 1. 1 is a table showing the values and evaluations of the formulations, mold retention, 25% CLD, and compression set of the examples and comparative examples.

An embodiment of the polyurethane foam of the present invention will be described below. The polyurethane foam of the present invention can be obtained by a mechanical froth method from a polyurethane reaction composition and an inert gas.
The mechanical froth method is a method of forming a polyurethane foam by supplying a mixed raw material obtained by compressing and mixing an inert gas into a polyurethane reaction composition to an OX mixer or a nozzle with a narrowed tip and discharging the mixed raw material from the OX mixer or nozzle. In the mechanical froth method, the inert gas that had been compressed expands when the mixed raw material is discharged to form bubbles, and in this state, the polyol component and the isocyanate component react and harden to form a polyurethane foam. Therefore, the polyurethane foam uses an inert gas as a foaming functional agent (foaming agent) for the polyurethane reaction composition, and the cells of the polyurethane foam contain the inert gas.

The polyurethane reaction composition contains a polyol component, a foam stabilizer, a catalyst, an isocyanate component, and in the present invention, further contains an acid-modified polyolefin powder, and further contains an inert gas as a foaming functional agent (foaming agent) as a mixed raw material.
The polyol component includes polymer polyols as well as polyols other than polymer polyols.

Examples of polymer polyols include those obtained by graft-polymerizing acrylonitrile, styrene, etc. onto polyether polyol. The polymer polyol preferably has a molecular weight of 2000 to 5000, 2 to 4 functional groups, and a solid content of acrylonitrile, styrene, etc. in the polymer polyol of 10 to 50 weight % (wt %). Two or more types of polymer polyols may be used in combination. By including a polymer polyol in the polyol component, the distortion characteristics can be improved.

The amount of polymer polyol in the polyurethane reaction composition is preferably 5 to 40% by weight. If the amount of polymer polyol is too small, appropriate hardness cannot be obtained, and if the amount is too large, the viscosity of the polyurethane reaction composition increases too much, making it difficult to foam by mechanical froth. The solids content of the polymer polyol in the polyurethane reaction composition is preferably 2 to 13% by weight. If the solids content of the polymer polyol is too small, it becomes difficult to thermally mold and the shape retention becomes poor, and if the solids content is too high, it is easy to thermally mold, but the viscosity of the polymer polyol increases too much, making it difficult to handle.

As polyols other than polymer polyols, known polyols such as polyether polyols and polyester polyols can be used. As polyether polyols, those with a molecular weight of 400 to 5000 and a functional number of 2 to 4 are preferred, and as polyester polyols, those with a molecular weight of 300 to 3000 and a functional number of 2 to 4 are preferred. Two or more types of polyols other than polymer polyols may be used in combination.

As the foam stabilizer, those known for use in polyurethane foams can be used. Examples include silicone-based foam stabilizers, fluorine-based foam stabilizers, and known surfactants. The amount of foam stabilizer is determined appropriately, but an example is 1.0 to 6.0 parts by weight per 100 parts by weight of the polyol component.

Catalysts include amine catalysts for polyurethane foams and organometallic catalysts, which are used alone or in combination. Examples of amine catalysts include monoamine compounds, diamine compounds, triamine compounds, polyamine compounds, cyclic amine compounds, alcohol amine compounds, ether amine compounds, etc., and these may be used alone or in combination of two or more. Examples of organometallic catalysts include organotin compounds, organoferric compounds, organobismuth compounds, organolead compounds, organozinc compounds, etc., and these may be used alone or in combination of two or more. The amount of catalyst is determined appropriately, but an example is 0.03 to 3.0 parts by weight per 100 parts by weight of the polyol component.

The isocyanate component may be any of aromatic, alicyclic, and aliphatic isocyanates, and may also be bifunctional isocyanates having two isocyanate groups in one molecule, or trifunctional or higher isocyanates having three or more isocyanate groups in one molecule, and these may be used alone or in combination.

For example, bifunctional isocyanates include 2,4-tolylene diisocyanate (TDI), 2,6-tolylene diisocyanate (TDI), m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate (MDI), 2,4'-diphenylmethane diisocyanate (MDI), 2,2'-diphenylmethane diisocyanate (MDI), xylylene diisocyanate, 3,3'-dimethyl-4,4'-biphenylene diisocyanate, 3, Examples include aromatic compounds such as 3'-dimethoxy-4,4'-biphenylene diisocyanate, alicyclic compounds such as cyclohexane-1,4-diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, and methylcyclohexane diisocyanate, and aliphatic compounds such as butane-1,4-diisocyanate, hexamethylene diisocyanate, isopropylene diisocyanate, methylene diisocyanate, and lysine isocyanate.

An example of a difunctional or higher isocyanate is polymethylene polyphenylisocyanate (polymeric MDI). Examples of trifunctional or higher isocyanates include 1-methylbenzene-2,4,6-triisocyanate, 1,3,5-trimethylbenzene-2,4,6-triisocyanate, biphenyl-2,4,4'-triisocyanate, diphenylmethane-2,4,4'-triisocyanate, methyldiphenylmethane-4,6,4'-triisocyanate, 4,4'-dimethyldiphenylmethane-2,2',5,5'tetraisocyanate, and triphenylmethane-4,4',4"-triisocyanate. The isocyanate is not limited to one type, and may be one or more types. For example, one type of aliphatic isocyanate and two types of aromatic isocyanate may be used in combination. The isocyanate index is preferably 90 to 110. The isocyanate index is the value obtained by multiplying the number of moles of isocyanate groups per mole of active hydrogen groups contained in the urethane raw material by 100, and is calculated as [(isocyanate equivalent in the foaming raw material/active hydrogen equivalent in the foaming raw material) x 100].

Examples of acid-modified polyolefin powders include powders of polyethylene (PE), polypropylene (PP), polybutene (PB), polypentene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, styrene-ethylene-butene-styrene copolymer (SEBS), etc., modified with an acid of an unsaturated carboxylic acid or its anhydride.

Among the acid-modified polyolefins, acid-modified polyolefins modified with maleic anhydride are preferred. Examples of acid-modified polyolefins modified with maleic anhydride include maleic anhydride-modified polyethylene, maleic anhydride-modified polypropylene, and maleic anhydride-modified ethylene-propylene copolymers. The maleic anhydride-modified polypropylene includes polypropylene, which is a random copolymer with ethylene, modified with maleic anhydride, and the maleic anhydride-modified ethylene-propylene copolymer includes polypropylene, which is a so-called block copolymer in which ethylene and propylene are copolymerized, modified with maleic anhydride. In particular, maleic anhydride-modified polyethylene and maleic anhydride-modified polypropylene are preferred because they have better mold retention than other acid-modified polyolefins. The acid-modified polyolefin powder is not limited to one type, and may include multiple types. The powder refers to a particle size of 5 to 250 μm. The melting point of the acid-modified polyolefin is 80 to 165° C., and preferably 90 to 140° C.
By including an acid-modified polyolefin powder in the polyurethane reaction composition together with a polymer polyol, the polyurethane foam can be preheated at a temperature higher than the melting point of the acid-modified polyolefin powder, and the polyurethane foam can be thermoplastically deformed (thermal compression molding) at or below the decomposition temperature of the urethane bond, and the distortion characteristics are improved.

The amount of acid-modified polyolefin powder in the polyurethane reaction composition is preferably 3 to 35% by weight. If the amount of acid-modified polyolefin powder is too small, it will not be possible to thermally shape the composition, and if the amount is too large, the viscosity will increase and foaming by mechanical froth will not be possible.

The total weight of the polymer polyol solids and the acid-modified polyolefin powder is preferably 5 to 40% by weight of the polyurethane reaction composition. If the total weight of the polymer polyol solids and the acid-modified polyolefin powder is too small, thermal shaping is not possible, and if it is too large, the viscosity of the polyurethane reaction composition increases too much, making it impossible to foam using mechanical froth.

Other optional additives may be added to the polyurethane reaction composition, such as crosslinkers, fillers, dyes, pigments, antioxidants, and flame retardants.
Examples of the crosslinking agent include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1-4 butanediol, and 1,6-hexanediol.
Fillers include alumina trihydrate, silica, talc, calcium carbonate, clay, and the like.

As the inert gas used as the foaming functional agent (foaming agent), a gas that does not adversely affect the reaction between the polyol and the isocyanate, such as dry air or nitrogen, is suitable. The mixing ratio of the inert gas in the polyurethane reaction composition is preferably 31 to 91 volume percent. The mixing ratio of the inert gas refers to the volume percent of the foaming gas relative to 100 parts by volume of the polyurethane reaction composition excluding the inert gas.

The polyurethane foam of the present invention has a compression set (based on JIS K 6401) of 10% or less and is less susceptible to plastic deformation due to long-term use.
The polyurethane foam of the present invention preferably has a 25% compression load (25% CLD, JIS K 6254: compressive stress when a φ50 mm sample is compressed 25% at a rate of 1 mm/min) of 0.01 to 0.1 MPa.

The polyurethane foam of the present invention is shaped by thermal compression molding to produce a molded product. Thermal compression molding is performed by preheating the polyurethane foam at 190°C to 210°C for 3 to 10 minutes, and then compressing and pressing it in a mold at room temperature (20 to 30°C). The mold surface is provided with irregularities, which are then formed on the surface of the molded product. The compression ratio during thermal pressing is preferably 25 to 75%. The compression ratio is calculated as compression ratio = [(original thickness - thickness when compressed) / original thickness x 100].

An example of a polyurethane foam molded body is shown. The polyurethane foam molded body 10 shown in Figures 1 and 2 is formed by preheating a sheet of the polyurethane foam of the present invention having a specified thickness at 200°C for 5 minutes and compression molding it at room temperature (25°C), and is used as an insole. The polyurethane foam molded body 10 has recesses 101 and 103 and protrusions 102, 104, and 106 formed in areas corresponding to the base of the toes, the arch, and the heel. Reference numeral 107 denotes a general portion 107 with no recesses or protrusions.

The polyurethane foam molded body 10 made by thermal compression molding is made of the polyurethane foam of the present invention, which has good distortion characteristics, so the uneven shape is not easily plastically deformed even when pressed during long-term use, and good quality can be maintained.

The following raw materials were used in the polyurethane reaction composition having the formulation shown in FIG. 3, and the mixing ratio of inert gas (nitrogen) was adjusted to 85% by volume. The mixture was mixed and stirred in a mechanical froth foaming machine, and continuously discharged onto release paper and heated to 120 to 200° C. to produce a sheet-like polyurethane foam with a thickness of 10 mm.
Polyol 1: Polyether polyol, product name; PP-3000, manufactured by Sanyo Chemical Industries, Ltd., molecular weight 3000, number of functional groups 3, propylene oxide content 100%
Polyol 2: polymer polyol, product name: EX-914, manufactured by Asahi Glass Co., Ltd., molecular weight: 3000, number of functional groups: 3, solid content: 22.9% by weight
Polyol 3: polymer polyol, product name: EX-913, manufactured by Asahi Glass Co., Ltd., molecular weight: 3000, number of functional groups: 2, solid content: 20% by weight
Polyol 4: polymer polyol, product name; FS-7301, manufactured by Sanyo Chemical Industries, Ltd., molecular weight 3000, number of functional groups 3, solid content 43% by weight
・Normal polyethylene (PE) powder: 1050, melting point = 105°C, manufactured by Tokyo Ink Co., Ltd. ・Polyamide resin powder: SK-1, melting point = 115°C, manufactured by Tokyo Ink Co., Ltd. ・Polyester resin powder: G-120, melting point = 125°C, manufactured by Tokyo Ink Co., Ltd. ・Acid-modified polyethylene (PE) powder: maleic anhydride modified polyethylene, product name: Admer AT1000, melting point = 123°C, manufactured by Mitsui Chemicals, Inc.
Acid-modified polypropylene (PP) powder: maleic anhydride-modified polypropylene, product name: UMEX 1010, melting point: 135°C, manufactured by Sanyo Chemical Industries, Ltd. Silicone foam stabilizer: product name: SZ-1952, manufactured by Dow Corning Toray Co., Ltd. Iron catalyst: product name: FIN-P1, manufactured by Nippon Kagaku Sangyo Co., Ltd. Isocyanate: product name: M5S, manufactured by BASF Inoac Polyurethanes, polymeric MDI (crude MDI), NCO %: 34%
In addition, since ordinary polyethylene (PE) powder, polyamide resin powder, polyester resin powder, acid-modified polyethylene (PE) powder, and acid-modified polypropylene (PP) powder are all thermoplastic resin powders, they are all classified as "thermoplastic powders" in FIG. 3.
3, "wt %" refers to the weight % in the polyurethane reaction composition. The total resin amount (wt %) refers to the weight % of the total amount of the thermoplastic resin powder and the solid content of the polymer polyol in the polyurethane reaction composition relative to the polyurethane reaction composition.

The foaming state was judged visually for each Example and Comparative Example. The evaluation was made as "◎" if there were no broken bubbles or other defects, and "×" if there were any defects such as broken bubbles.

In addition, for each of the Examples and Comparative Examples, thermal compression molding was performed, and the initial moldability, shape retention after 24 hours at room temperature (room temperature x 24 h), and shape retention after 1 week at room temperature (room temperature x 1 week) were measured.
In the thermal compression molding, a polyurethane foam sheet having a thickness (original thickness) of 10 mm was preheated at 200° C. for 5 minutes, and then compressed to a thickness of 5 mm (compression rate of 50%) in a press at room temperature and maintained in that state for 5 minutes. During pressing, a spacer having a thickness of 5 mm was placed on both sides of the polyurethane foam sheet to adjust the pressing amount to 5 mm.
The initial formability (%) was calculated as the shape retention immediately after molding, in which the compressed state was maintained for 5 minutes, by [(original thickness-thickness immediately after molding)/(original thickness-spacer thickness)×100].
Shape retention (room temperature × 24 h (%)) was calculated as the shape retention rate after leaving the molded product at room temperature for 24 hours by the formula: [(original thickness−thickness after 24 hours)/(original thickness−thickness immediately after molding) × 100].
The shape retention (room temperature x 1 week (%)) was calculated by the shape retention rate after leaving the molded product at room temperature for 1 week, as follows: [(original thickness - thickness after 1 week) / (original thickness - thickness immediately after molding) x 100].
The initial formability and form retention were evaluated as follows: if the form retention rate was less than 50%, it was marked "x", if it was between 50% and less than 70%, it was marked "△", if it was between 70% and less than 90%, it was marked "◯", and if it was between 90% and 100%, it was marked "◎".

Further, for each of the examples and comparative examples, the 25% CLD and the compression set were measured.
25% CLD (MPa) is the compressive stress when a φ50 mm sample is compressed by 25% at a speed of 1 mm/min, based on JIS K 6254.
The compression set (%) is a value calculated according to JIS K6401 by compressing a 50×50 mm sample by 50% in the thickness direction, leaving it to stand at a prescribed temperature (70° C.) for 22 hours, and then releasing the compressive stress at room temperature. After 30 minutes, the thickness of the sample (thickness after release) is measured and calculated according to the following formula:
Compressive set (%) = [(thickness before compression - thickness after release) / thickness before compression x 100]
The evaluation of the compression set was made as follows: when the compression set was less than 5%, it was marked "A", and when it was 5% or more, it was marked "X".
An overall evaluation was performed according to the results of each test item. The overall evaluation was determined to be the lowest evaluation of the evaluations of each test item. For example, if there was even one "x" in the evaluation of a test item, the overall evaluation was "x", if all the evaluations of the test items were "△" or higher and even one was "△", the overall evaluation was "△", if all the evaluations of the test items were "〇" or higher and even one was "〇", the overall evaluation was "〇", and if all the evaluations of the test items were "◎", the overall evaluation was "◎".

Comparative Example 1 is an example in which the polyol component contains a polymer polyol, and ordinary polyethylene powder is added as the thermoplastic resin powder. The results of Comparative Example 1 showed that the foam had broken, so other tests were not performed. The overall evaluation was "X".

Comparative Example 2 is an example that does not contain polymer polyol and does not add thermoplastic resin powder. Comparative Example 2 has a foaming state of "◎", initial moldability of 10.6%, rated "×", mold retention (room temperature x 24 h) of 90.5%, rated "◎", mold retention (room temperature x 1 week) of 66.7%, rated "△", 25% CLD of 0.015 MPa, compression set of 2.8%, rated "◎", and poor initial moldability, with an overall rating of "×".

Comparative Example 3 contains polymer polyol, but does not add thermoplastic resin powder, and has a polymer polyol solid content of 5 wt% in the polyurethane reaction composition and a total resin content of 5.0 wt%. Comparative Example 3 has a foaming state of "◎", initial moldability of 20.5%, rated "×", mold retention (room temperature x 24 h) of 93.5%, rated "◎", mold retention (room temperature x 1 week) of 41.9%, rated "×", 25% CLD of 0.050 MPa, compression set of 2.7%, rated "◎", and poor initial moldability and mold retention (room temperature x 1 week), resulting in an overall rating of "×".

Comparative Example 4 is an example in which polymer polyol is included, thermoplastic resin powder is not added, the polymer polyol solid content in the polyurethane reaction composition is 7.5 wt%, and the total resin amount is 7.5 wt%. Comparative Example 4 has a foaming state of "◎", initial moldability of 35.1%, rated "×", mold retention (room temperature x 24 h) of 91.7%, rated "◎", mold retention (room temperature x 1 week) of 64.3%, rated "△", 25% CLD of 0.053 MPa, compression residual set of 2.5%, rated "◎", and initial moldability is poor, resulting in an overall rating of "×".

Comparative Example 5 is an example that does not contain polymer polyol, and 29.4 wt% of normal polyethylene powder is added as the thermoplastic resin powder, making the total resin amount 29.4 wt%. Comparative Example 5 has the following foaming state: ◎, initial moldability: 28.2%, rated "x", mold retention (room temperature x 24 h): 82.5%, rated "good", mold retention (room temperature x 1 week): 38.6%, rated "x", 25% CLD: 0.028 MPa, compression set: 2.1%, rated "◎", and initial moldability and mold retention (room temperature x 1 week) are poor, resulting in an overall rating of "x".

Comparative Example 6 contains polymer polyol, and polyamide resin powder is added as thermoplastic resin powder, the polymer polyol solid content in the polyurethane reaction composition is 15 wt%, the amount of polyamide resin powder added is 18.1 wt%, and the total resin amount is 33.1 wt%. Comparative Example 6 has a foaming state of "◎", initial moldability of 31.8%, rated "x", mold retention (room temperature x 24 h) of 78.8%, rated "◯", mold retention (room temperature x 1 week) of 69.5%, rated "△", 25% CLD of 0.103 MPa, compression set of 7.1%, rated "x", and the initial moldability and compression set are poor, resulting in an overall rating of "x".

Comparative Example 7 is the same as Comparative Example 6, except that polyester resin powder was used as the thermoplastic resin powder. Comparative Example 7 has the following characteristics: foaming state is "◎", initial moldability is 30.4%, rated "×", mold retention (room temperature x 24 h) is 78.2%, rated "◯", mold retention (room temperature x 1 week) is 69.4%, rated "△", 25% CLD is 0.048 MPa, compression set is 8.0%, rated "×", and the initial moldability and compression set are poor, resulting in an overall rating of "×".

Example 1 is an example in which 5 parts by weight of polyol 4 (POP) as a polymer polyol and 5 parts by weight of acid-modified polyethylene powder as a thermoplastic resin powder are added to 65.9 parts by weight of the polyol component, the content of the polymer polyol in the polyurethane reaction composition is 5.0 wt%, the solid content of the polymer polyol is 2.0 wt%, the amount of acid-modified polyethylene powder added to the polyurethane reaction composition is 5.0 wt%, and the total resin amount is 7.0 wt%. Example 1 has a foaming state of "◎", initial moldability of 63.5%, rated "△", mold retention (room temperature x 24 h) of 71%, rated "〇", mold retention (room temperature x 1 week) of 60.3%, rated "△", 25% CLD of 0.691 MPa, compression residual set of 3.7%, rated "◎", and an overall rating of "△". Example 1 had no "x" marks in any of the evaluations, and the initial moldability, mold retention, and compression set were all good, so it can be thermally compressed and has good distortion characteristics.

Example 2 is the same as Example 1 except that 20 parts by weight of polyol 4 (POP) was used as the polymer polyol in 65.9 parts by weight of the polyol component, the content of the polymer polyol in the polyurethane reaction composition was 20.1 wt%, the solid content of the polymer polyol was 5.0 wt%, the amount of acid-modified polyethylene powder added in the polyurethane reaction composition was 5.0 wt%, and the total resin amount was 10.0 wt%. Example 2 has the following foaming state: ◎, initial moldability: 97.9%, evaluation: ◎, mold retention (room temperature x 24 h): 91.3%, evaluation: ◎, mold retention (room temperature x 1 week): 84.8%, evaluation: ○, 25% CLD: 0.715 MPa, compression residual set: 3.3%, evaluation: ◎, and the overall evaluation: ○. Example 2 received all evaluations of "good" or better, and the initial moldability, mold retention, and compression set were all good, so it is possible to perform thermal compression molding and has good distortion characteristics.

Example 3 is the same as Example 1, except that 40 parts by weight of polyol 4 (POP) as a polymer polyol and 10 parts by weight of acid-modified polyethylene powder were added to 65.9 parts by weight of the polyol component, and the content of the polymer polyol in the polyurethane reaction composition was 38.2 wt%, the solid content of the polymer polyol was 11.0 wt%, the amount of acid-modified polyethylene powder added to the polyurethane reaction composition was 9.6 wt%, and the total resin amount was 20.6 wt%. Example 3 has a foaming state of "◎", initial moldability of 95.4%, rated "◎", mold retention (room temperature x 24 h) of 92.2%, rated "◎", mold retention (room temperature x 1 week) of 88.5%, rated "〇", 25% CLD of 1.073 MPa, compression residual set of 3.7%, rated "◎", and an overall rating of "〇". Example 3 received all evaluations of "good" or better, and the initial moldability, mold retention, and compression set were all good, so it can be thermally compressed and has good distortion characteristics.

Example 4 is the same as Example 1, except that 30 parts by weight of polyol 4 (POP) as a polymer polyol and 30 parts by weight of acid-modified polyethylene powder were added to 65.9 parts by weight of the polyol component, and the content of the polymer polyol in the polyurethane reaction composition was 24.1 wt%, the solid content of the polymer polyol was 8.4 wt%, the amount of acid-modified polyethylene powder added to the polyurethane reaction composition was 24.1 wt%, and the total resin amount was 32.5 wt%. Example 4 has a foaming state of "◎", initial moldability of 97.0%, rated "◎", mold retention (room temperature x 24 h) of 96.8%, rated "◎", mold retention (room temperature x 1 week) of 95.2%, rated "◎", 25% CLD of 0.669 MPa, compression residual set of 3.1%, rated "◎", and an overall rating of "◎". Example 4 received an excellent rating for all evaluations, with good initial moldability, mold retention, and compression set, making it possible to perform thermal compression molding and providing good distortion characteristics.

Example 5 is an example in which the ratio of polymer polyol and acid-modified polyethylene powder was changed while maintaining the total resin amount at 32.5 wt%, the same as in Example 4. Example 5 is the same as Example 4, except that 10 parts by weight of polyol 4 (POP) was used as the polymer polyol and 40 parts by weight of acid-modified polyethylene powder was added to 65.9 parts by weight of the polyol component, and the content of polymer polyol in the polyurethane reaction composition was 7.4 wt%, the solid content of polymer polyol was 2.8 wt%, the amount of acid-modified polyethylene powder added to the polyurethane reaction composition was 29.7 wt%, and the total resin amount was 32.5 wt%. Example 5 has a foaming state of "◎", initial moldability of 97.1%, rated "◎", mold retention (room temperature x 24 h) of 98.1%, rated "◎", mold retention (room temperature x 1 week) of 97.2%, rated "◎", 25% CLD of 0.550 MPa, compression set of 3.6%, rated "◎", and an overall rating of "◎". Example 5 has all ratings of "◎", and initial moldability, mold retention, and compression set are all good, so it can be thermally compressed and has good distortion characteristics.

Example 6 is the same as Example 5 except that the amount of acid-modified polyethylene powder was increased to 50 parts by weight. The content of polymer polyol in the polyurethane reaction composition was 6.9 wt%, the solid content of polymer polyol was 2.8 wt%, the amount of acid-modified polyethylene powder added to the polyurethane reaction composition was 34.6 wt%, and the total resin amount was 37.4 wt%. Example 6 has a foaming state of "◎", initial moldability of 97.7%, rated "◎", mold retention (room temperature x 24 h) of 98.8%, rated "◎", mold retention (room temperature x 1 week) of 97.9%, rated "◎", 25% CLD of 0.405 MPa, compression set of 4.6%, rated "◎", and an overall rating of "◎". Example 6 has all ratings of "◎", and the initial moldability, mold retention, and compression set are all good, so that thermal compression molding is possible and the distortion characteristics are good.

Example 7 is the same as Example 3 except that acid-modified polypropylene was added instead of acid-modified polyethylene. The content of polymer polyol in the polyurethane reaction composition is 38.2 wt%, the solid content of polymer polyol is 11 wt%, the amount of acid-modified polypropylene powder added in the polyurethane reaction composition is 9.6 wt%, and the total resin amount is 20.6 wt%. Example 7 has a foaming state of "◎", initial moldability of 94.2%, rated "◎", mold retention (room temperature x 24 h) of 91.5%, rated "◎", mold retention (room temperature x 1 week) of 87.2%, rated "〇", 25% CLD of 1.082 MPa, compression set of 3.8%, rated "◎", and an overall rating of "◎". Example 7 has all ratings of "◎", and the initial moldability, mold retention, and compression set are all good, so that thermal compression molding is possible and the distortion characteristics are good.

In this way, the polyurethane foam of the present invention can be thermally compressed and has good distortion characteristics. Furthermore, molded articles of the polyurethane foam of the present invention have good distortion characteristics that enable them to maintain the surface irregularities formed by thermal compression molding.

10 Molded article of polyurethane foam 101, 103 Concave portion 102, 104, 106 Convex portion 107 General portion without concavities and convexities

Claims (5)

A polyurethane foam is a foam of a polyurethane reaction composition containing a polymer polyol and an acid-modified polyolefin powder having a melting point of 80 to 165°C, the polyurethane foam containing an inert gas in cells and having a compression set (based on JIS K6401) of less than 5%. The polyurethane foam according to claim 1, which has an initial moldability (%) of 50% or more as measured by the following method.
<Measurement method>
A polyurethane foam sheet having an original thickness of 10 mm is heated at 200° C. for 5 minutes, compressed to 5 mm using a press at room temperature, and the "thickness immediately after molding" is measured after maintaining this state for 5 minutes. The initial moldability (%) is calculated using the following formula.
Initial formability (%) = [100 x (10 mm - thickness immediately after forming) / 5 mm] The polyurethane foam according to claim 1 or 2, characterized in that the 25% compression load is within the range of 0.405 to 1.082 MPa. A molded article having irregularities, formed by compressing the polyurethane foam according to any one of claims 1 to 3. An insole comprising the molded article according to claim 4.

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