Thermoplastic polyurethane, polyurethane resin composition comprising same, and molded product obtained from polyurethane resin composition

Abstract

Disclosed is a thermoplastic polyurethane as a product obtained from a reaction mixture comprising (A) a polycarbonate polyol having a number average molecular weight Mn greater than 500 and less than 2000, (B) an alicyclic polyisocyanate, and (C) a chain extender. The thermoplastic polyurethane has less than 40% by mass of hard segments (HS), based on the total mass of the thermoplastic polyurethane.

Description

Technical Field

[0001] The present invention relates to thermoplastic polyurethane (TPU), a polyurethane resin composition containing the TPU, and a molded product obtained from the polyurethane resin composition. Background Art

[0002] Resin glass, as an alternative to conventional silica-based glass, has been widely used, for example, for lightweight and shatterproof vehicle windows.

[0003] Such resin glass is usually made of a plastic substrate (such as polyacrylate or polycarbonate) and a hard coat (such as a silica-based material or a polymer material) applied to the substrate. In other words, to protect the plastic substrate, the plastic substrate is covered with a hard coat.

[0004] For example, Japanese Patent 5944069 (Patent Document 1) discloses a polymer substrate covered with a silica layer as a hard coat, particularly a polymer substrate having good transparency to visible light. The silica layer is obtained by plasma-enhanced chemical vapor deposition (PE-CVD).

[0005] In addition, Japanese Unexamined Patent Application JP 2020-69749A (Patent Document 2) discloses a laminated panel including a polycarbonate substrate and a thermoplastic elastomer such as polystyrene, polyurethane, polyester, polyamide, etc. as a hard coat. In JP 2020-69749A, in order to improve the adhesion between the substrate and the hard coat, it is recommended to further use a primer layer.

[0006] In Japanese Patent 5944069, a silicon-based inorganic material is used as a hard coat, and the silicon-based inorganic material must be deposited on the substrate by using a special deposition device (such as a device for plasma-enhanced chemical vapor deposition).

[0007] On the other hand, JP-A 2020-69749 proposes to use a polymer film as a hard coat of resin glass. However, according to JP-A 2020-69749, a primer must be applied to the plastic substrate before applying the hard coat made of a polymer to hold the hard coat on the substrate.

[0008] Technical Problem

[0009] However, known materials do not necessarily have good initial transparency, small initial haze, nor sufficient abrasion resistance, especially as a hard coat to be provided on resin glass, specifically as a hard coat that meets the ECE R43 standard for glass components in vehicles. In addition, it is desired that a resin or resin composition suitable as a hard coat can be manufactured economically following a simple procedure.

[0010] Accordingly, an object of the present invention is to provide a thermoplastic polyurethane having good transparency, a low haze value, and good abrasion resistance, which can be easily applied as a hard coat on a polymeric substrate. Preferably, the thermoplastic polyurethane can be applied to the substrate economically.

[0011] Solution to the problem

[0012] The inventors of the present invention have found that the object of the present invention is solved by the following means:

[0013] A thermoplastic polyurethane, which is a product from a reaction mixture comprising:

[0014] (A) A polycarbonate polyol having a number average molecular weight Mn greater than 500 and less than 2000,

[0015] (B) An alicyclic polyisocyanate, and

[0016] (C) A chain extender, and

[0017] wherein, based on the total mass of the thermoplastic polyurethane, the thermoplastic polyurethane has a hard segment (HS) accounting for less than 40% by mass; or

[0018] A thermoplastic polyurethane, which is a product from a reaction mixture comprising:

[0019] (A) A polycarbonate polyol having a number average molecular weight Mn greater than 500 and less than 3000,

[0020] (B) An alicyclic polyisocyanate, and

[0021] (C) At least two types of chain extenders,

[0022] wherein, based on the total mass of the thermoplastic polyurethane, the thermoplastic polyurethane has a hard segment (HS) accounting for less than 50% by mass Detailed description

[0023] [Thermoplastic polyurethane (TPU1)]

[0024] The thermoplastic polyurethane (TPU1) of the present invention is a product from a reaction mixture (RM1) comprising:

[0025] (A1) A polycarbonate polyol having a number average molecular weight Mn greater than 500 and less than 2000 (referred to as polyol (A1) or component (A1)),

[0026] (B1) An alicyclic polyisocyanate (referred to as polyisocyanate (B1) or component (B1)), and

[0027] (C1) Chain extender (referred to as chain extender (C1) or component (C1)).

[0028] In the thermoplastic polyurethane (TPU1) obtained from a reaction mixture (RM1) comprising a polyol (A1), a polyisocyanate (B1) and a chain extender (C1), the hard segment (HS) accounts for less than 40% by mass of the total mass of the thermoplastic polyurethane. The thermoplastic polyurethane has a hard segment (HS) and a soft segment (SS). The hard segment (HS1) serving as a crosslinking point in the TPU is prepared from the polyisocyanate (B1) and the chain extender (C1), while the soft segment (SS1) serving as the polymer matrix is prepared from the polyol (A1). The resulting TPU1 has good initial transparency (specifically represented by a low initial haze value that can be maintained for a long time) and good abrasion resistance.

[0029] Details of components (A1) to (C1) are as follows:

[0030] [(A1) Polycarbonate polyol]

[0031] A polycarbonate diol (A1) is used to prepare TPU1. The polyol (A) can be

[0032] represented by the following formula (I):

[0033]

[0034] In formula (I), n ranges from 1 to 100, preferably from 2 to 20, and R is a straight-chain alkylene group, preferably a C2-C 16 alkylene group, more preferably a C3-C 12 alkylene group, and most preferably any one or more of C4-C9 alkylene groups. To prepare TPU1, a polycarbonate diol (A1) having a number-average molecular weight Mn in the range of greater than 500 and less than 2000, more preferably in the range of 600 to 1600, and further preferably in the range of 750 to 1200 is used.

[0035] A single type of or a combination of or two or more types of polycarbonate diols can be used as the polyol (A1).

[0036] In the present invention, the number-average molecular weight Mn is determined by the following formula:

[0037] Mn = (56100 × valency) / hydroxyl value.

[0038] In the above expression, the valency refers to the number of hydroxyl groups in the molecule. At this time, the valency of the polycarbonate diol in formula (1) is 2. In addition, the hydroxyl value is measured according to JIS K 1557 (Method B).

[0039] [Method for producing polycarbonate polyol]

[0040] The polyol (A1) of formula (I) can be produced by reacting an alcohol component (such as a C2-C 16 alkylene glycol, preferably a C3-C 12 alkylene glycol, and more preferably a C4-C9 alkylene glycol) with a dicarbonate component (such as dimethyl carbonate). Generally, the transesterification reaction is carried out with substantially equimolar amounts of the alcohol component and the dicarbonate component in the presence of a catalyst.

[0041] The reaction temperature during the transesterification reaction is not particularly limited as long as a practical reaction rate can be obtained. The lower limit of the reaction temperature is usually 70 °C, preferably 100 °C, and more preferably 130 °C. The upper limit of the reaction temperature is usually 250 °C, preferably 200 °C, more preferably 190 °C, even more preferably 180 °C, and particularly preferably 170 °C. The reaction pressure at the end of the reaction is not particularly limited, but the upper limit at this time is usually 10 kPa, preferably 5 kPa, and more preferably 1 kPa.

[0042] Based on 100 parts by weight of all the components for obtaining the thermoplastic polyurethane of the present invention in the reaction, the blending amount of the polyol (A1) can usually be selected from 40 parts by weight to 75 parts by weight, and preferably from 50 parts by weight to 75 parts by weight. In the present invention, the above blending amount of the polyol (A1) does not have any undue influence on the haze value. In addition, by using the polyol (A1) in the above blending ratio, the cooling time of the TPU after injection molding can be shortened.

[0043] The polyol (A1) has a linear structure, that is, a straight-chain structure without branches. However, a small amount of other types of polyols (such as branched polyols), for example, less than 5% by weight based on the total amount of the polyol (A1), can also be included in the formulation for preparing TPU1. For such branched polyols, R in formula (I) can be a C3-C 14 alkylene having one or two C1-C3 alkyl side chains.

[0044] Based on technical knowledge, good crystallinity comes from linear polyols. Therefore, in the prior art, it is considered that it is not recommended to use thermoplastic polyurethanes prepared by using linear polyols, specifically polyols without branches, for obtaining products with good transparency. Contrary to this perception, the use of the polyol (A1) in the present invention helps to impart good initial transparency and a small initial haze value to TPU1.

[0045] [(B1) Alicyclic polyisocyanate]

[0046] As a component of TPU1, an alicyclic polyisocyanate (B1) is used.

[0047] Examples of the alicyclic polyisocyanate (B1) include alicyclic diisocyanates such as cyclohexane diisocyanate, dicyclohexylmethane diisocyanate, isophorone diisocyanate (IPDI), 4,4'-dicyclohexylmethane diisocyanate (hydrogenated MDI), hydrogenated xylylene diisocyanate (hydrogenated XDI), and 1,4-bis(isocyanatomethyl)cyclohexane (1,4-H6XDI).

[0048] Among them, alicyclic diisocyanates having a completely or highly symmetric structure such as 4,4'-dicyclohexylmethane diisocyanate, hydrogenated 1,4-xylylene diisocyanate, and 1,4-bis(isocyanatomethyl)cyclohexane are preferred. Primary isocyanates such as hydrogenated 1,4-xylylene diisocyanate and 1,4-bis(isocyanatomethyl)cyclohexane are particularly preferred.

[0049] A single type or two or more types of polyisocyanates can be used as the polyisocyanate (B1) for preparing the thermoplastic polyurethane. Generally, the amount of the polyisocyanate (B1) is independent of the functionality of the polyol (A1) and the polyisocyanate (B1), and the NCO can be made to be completely equimolar or approximately equimolar with respect to the OH groups in the polyol (A1).

[0050] Based on the total mass of the components (A1) to (C1), the concentration of the alicyclic polyisocyanate (B1) can be in the range of 1.1 mol / kg to 1.8 mol / kg, preferably in the range of 1.2 mol / kg to 1.8 mol / kg.

[0051] [(C1) Chain extender]

[0052] As a component of TPU1, a chain extender (C1) selected from at least one of the group consisting of: 1,2-ethylene glycol, 1,3-propanediol (1,3-PD), 1,4-butanediol (1,4-BD), 1,5-pentanediol, 1,6-hexanediol (1,6-HD), 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol (1,9-ND), 3-methyl-1,5-pentanediol, 2-methyl-1,8-octanediol, diethylene glycol, and dipropylene glycol is used.

[0053] In other words, as the chain extender (C1), a single type or a combination or two or more types of the above-mentioned diols can be used.

[0054] It is preferred to use 1,4-butanediol alone. In addition, a combination of 1,4-butanediol with one or more of 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, and 1,9-nonanediol (1,9-ND) is also preferred. Specifically, by using a combination, the initial haze and abrasion resistance of the TPU tend to be improved.

[0055] [Hard segment (HS1)]

[0056] Relative to the total mass of the TPU1, the TPU1 of the present invention has a hard segment (HS1) of less than 40% by mass, preferably 10% to 35% by mass, and particularly 15% to 30% by mass. When the hard segment (HS1) is less than 40% by mass, a TPU1 with good abrasion resistance is obtained. Within the above numerical range, not only the abrasion resistance of the TPU1 is improved, but also the chemical resistance and anti-fouling performance are improved. In addition, when HS1 is set as described above, good processability, especially molding characteristics and film-forming characteristics, can be obtained.

[0057] The content of the hard segment can be controlled within the above range according to known methods by appropriately selecting the blending amounts of the components in the reaction mixture (RM1). More specifically, the weight ratio of the polyol (A1) to the polyisocyanate (B1) can be in the range of (10:10) to (10:2), preferably in the range of (10:9) to (10:3), and particularly (10:7) to (10:5) ((A1):(B1)). At the same time, the weight ratio of the polyisocyanate (B1) to the chain extender (C1) can be in the range of (1:1) to (6:1), preferably in the range of (1:1) to (5:1), and particularly (1.5:1) to (3.5:1) ((B1):(C1)).

[0058] Another type of thermoplastic polyurethane (TPU2) is as good as the TPU1 in terms of optical properties (initial transparency, initial haze) and mechanical strength (abrasion resistance).

[0059] [Thermoplastic polyurethane (TPU2)]

[0060] The thermoplastic polyurethane (TPU2) of the present invention is a product from a reaction mixture (RM2) containing the following substances:

[0061] (A2) A polycarbonate polyol having a number average molecular weight Mn greater than 500 and less than 3000 (referred to as polyol (A2) or component (A2)),

[0062] (B2) An alicyclic polyisocyanate (referred to as polyisocyanate (B2) or component (B2)), and

[0063] (C2) At least two types of chain extenders (referred to as chain extender (C1) or component (C1)).

[0064] To prepare the TPU2, two or more types of chain extenders are required in the reaction mixture (RM2) containing components (A2) to (C2).

[0065] Thermoplastic polyurethane (TPU2) is obtained from a reaction mixture (RM2) comprising a polyol (A2), a polyisocyanate (B2), and a chain extender (C2), wherein TPU2 accounts for less than 50% by mass of the total mass of the thermoplastic polyurethane (TPU 2). The thermoplastic polyurethane has hard segments (HS) and soft segments (SS). The hard segments (HS2), which serve as crosslinking points in the TPU, are prepared from the polyisocyanate (C2) and the chain extender (B2), while the soft segments (SS2), which serve as the polymer matrix, are prepared from the polyol (A1). The resulting TPU2 has good initial transparency (specifically represented by a low initial haze value that can be maintained for a long time) and good abrasion resistance.

[0066] [(A2) Polycarbonate polyol]

[0067] Regarding the polycarbonate polyol (A2) used for preparing TPU2, the same materials as those used for the polyol (A1) can be used, except that the number average molecular weight Mn of the polyol (A2) can be in the range of greater than 500 and less than 3000. Other details including the determination of the number average molecular weight Mn and production examples of the polyol (A2) are also the same as those described for the polyol (A1).

[0068] [(B2) Alicyclic polyisocyanate]

[0069] The alicyclic polyisocyanate (B1) that can be used for TPU1 is also used as the alicyclic polyisocyanate (B2).

[0070] [(C2) Chain extender]

[0071] As another component of TPU2, at least two types of chain extenders (C2) selected from the group consisting of: 1,2-ethanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 3-methyl-1,5-pentanediol, 2-methyl-1,8-octanediol, diethylene glycol, and dipropylene glycol are used.

[0072] The combination use of smaller chain extenders such as 1,2-ethanediol or 1,3-propanediol (smaller CE) with one or more larger chain extenders (larger CE) selected from 1,2-ethanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 3-methyl-1,5-pentanediol, 2-methyl-1,8-octanediol, diethylene glycol, and dipropylene glycol is preferred. Further preferably, the blending ratio of the smaller CE and the larger CE is in the range of (3:97) to (60:40), particularly in the range of (5:95) to (30:70).

[0073] [Hard segment (HS2)]

[0074] Relative to the total mass of TPU2, the TPU1 of the present invention has a hard segment (HS1) of less than 50% by mass, preferably 10% to 40% by mass, particularly 15% to 35% by mass. When the hard segment (HS2) is less than 50% by mass, a TPU2 with good abrasion resistance is obtained. Within the above numerical range, not only the abrasion resistance of TPU2 is improved, but also the chemical resistance and anti-fouling performance are improved. In addition, when HS2 is set as described above, good processability, particularly molding characteristics and film-forming characteristics, can be obtained.

[0075] In the TPU (TPU1 or TPU2) of the present invention, the content of HS (HS1 or HS2) in the TPU is set by selecting amounts of the polyol (A), isocyanate (B), and chain extender (C) so as to satisfy the following formula by selecting amounts having the above ranges:

[0076] Content of HS: { (molar amount of isocyanate (B) - molar amount of OH end groups of polyol (A)) * (mass of isocyanate (B)) + (mass of chain extender (C))} / (mass of isocyanate (B))

[0077] + mass of chain extender (C) + mass of polyol (A) ) × 100

[0078] In other words, the content of the hard segment can be controlled within the above range by appropriately selecting the blending amounts of the components in the reaction mixture (RM2) according to known methods. More specifically, the weight ratio of the polyol (A2) and the polyisocyanate (B2) can be in the range of (10:10) to (10:2), preferably in the range of (10:8) to (10:4), and particularly (10:7) to (10:5 ((A2):(B2))). At the same time, the weight ratio of the polyisocyanate (B2) and the chain extender (C2) can be in the range of (1:1) to (6:1), preferably in the range of (1:1) to (4:1), and particularly (1.5:1) to (2.5:1) ((B2):(C2)).

[0079] Despite the slight differences in the formulations between the thermoplastic polyurethanes, i.e., TPU1 and TPU2 of the present invention, they both have excellent optical properties. In the present invention, a sample of TPU or a TPU composition that is cooled to room temperature (25 °C) under atmospheric pressure shortly after preparation and kept as such for up to 88 hours while remaining in the same state without exposure to outdoor conditions is referred to as an "initial state sample". The total transparency and haze value of the initial state sample are referred to as the initial total transparency (TT) and the initial haze. The TPU and TPU composition of the present invention have excellent initial total transparency (TT) and a small initial haze value. Additionally, the thermoplastic polyurethane of the present invention has good mechanical properties, such as hardness sufficient to protect the surface of a plastic substrate that is part of plexiglass and improved abrasion resistance. Therefore, due to the good abrasion resistance, the thermoplastic polyurethane well maintains the initial transparency and the initially obtained low haze value even after exposure to harsh environmental conditions.

[0080] [Manufacture of thermoplastic polyurethane (TPU)]

[0081] The thermoplastic polyurethane can be synthesized according to known methods by using the above components (A) to (C) as raw materials, optionally using catalysts, crosslinking agents, crosslinking aids, etc. The polyurethane can be produced batchwise or continuously, both by known methods.

[0082] In the continuous method, for example, by using a reactive extruder, the polyurethane is produced according to the one-step method, the prepolymer method, etc. Generally speaking, considering production costs and time, the one-step method is preferably used. On the other hand, the semi-prepolymer method and the prepolymer method can also be used in order to carry out reactions to obtain products with uniform quality and improved transparency. In these methods, components (A) to (C) are generally continuously mixed and usually react with each other immediately after mixing. When using an extruder such as a twin-screw extruder, components (A) to (C) and additional catalysts and / or other materials (if any) are loaded into the extruder individually or in the form of a premixed state. The temperature of the extruder can be raised to 120 °C - 240 °C, preferably 150 °C - 220 °C. Then, the resulting polyurethane is extruded and then cooled and pelletized.

[0083] From the viewpoints of durability and molding properties, it is preferable that the weight-average molecular weight Mw of the thermoplastic polyurethane is in the range of preferably 80,000 to 250,000, more preferably 100,000 to 150,000. The molecular weight can generally be controlled by adjusting the ratio of the molar amount of the OH-bearing components (the sum of the polyol and the chain extender) to the molar amount of the polyisocyanate component. The molecular weight can also be controlled by adding a monohydric alcohol (monoalcohol) such as methanol, ethanol, propanol, butanol, 2-ethylhexanol to the reaction system.

[0084] The molecular weight of the polyurethane was measured by the GPC method (gel permeation chromatography), using polystyrene as the standard polymer and THF as the eluent. The sample solution was prepared to have a concentration of about 0.1%. The measurement was carried out within 15 minutes using an HLC-8220GPC manufactured by Tosoh Corporation (for example, with a flow rate of 0.35 ml / min and a temperature of 40 °C). The same applies to the following examples.

[0085] As described above, the polyurethane according to the present invention can first be generally prepared in the form of pellets, but can also be prepared in the form of powder. Subsequently, TPU processing can be further carried out by known methods such as injection molding, calendering or extrusion. Particularly for forming a TPU sheet applied as a hard coat on a resin substrate, a twin-screw extruder is preferably used.

[0086] Additional materials such as catalysts, crosslinking agents and crosslinking aids can also be used in the production of the polyurethane according to the present invention. The type of materials that can be applied is not particularly limited as long as the object of the present invention can be achieved.

[0087] Specific examples of the catalyst include organotin metal compounds containing tin, such as dibutyltin dilaurate (DBTDL), dioctyltin dilaurate, dibutyltin diacetate, tin(II) bis(2-ethylhexanoate); titanates; zirconium compounds; organobismuth metal compounds containing bismuth, such as bismuth carboxylates, including bismuth(III) neodecanoate and bismuth(III) 2-ethylhexanoate; organoiron metal compounds; amine-based catalysts, such as triethylamine, triethylenediamine, N-methylimidazole, N-ethylmorpholine, 1,8-diazabicyclo[5,4,0]-7-undecene (DBU); potassium acetate; phosphorus compounds, such as tributylphosphine, phosphine and phosphine oxide. These catalysts can be used alone or in combination of two or more.

[0088] Based on the total mass of components (A) to (C), the total amount of the catalyst to be used is preferably 5% by mass or less, more preferably in the range of 0.001% by mass to 2% by mass.

[0089] The thermoplastic polyurethane according to the present invention can be molded without further using additives, etc. The resulting formed product exhibits excellent transparency and abrasion resistance. In addition, if any improvement is necessary, additives can be further added to the TPU.

[0090] In the present invention, the total light transmittance (Tt) according to JIS K 7361-1:1997 and the haze according to JIS K 7136:2000 are used to evaluate the transparency.

[0091] [Thermoplastic polyurethane composition]

[0092] As described above, one or more additives can even be added to the finished TPU. Examples of such additives include antioxidants, light stabilizers, ultraviolet absorbers, nucleating agents, surface modifiers, fluorescent brighteners, lubricants, hydrolysis inhibitors, crosslinking agents, antistatic agents, antiblocking agents, heat stabilizers, flame retardants, heat resistance improvers, weather resistance improvers, reaction retardants, plasticizers, conductivity imparting agents, antibacterial agents, antifungal agents, inorganic fillers and organic fillers, fiber-based reinforcing agents, and colorants. By using the above additives, thermoplastic polyurethane compositions having various properties can be obtained according to the application or intended use.

[0093] As an additive for imparting weather resistance, an antioxidant, a light stabilizer, an ultraviolet inhibitor, or a combination of two or more of them can be added to the polyurethane according to the intended use of the polyurethane composition.

[0094] When a molded product obtained from a polyurethane or a polyurethane composition is exposed to outdoor use or other environmental conditions where oxidative degradation is expected, an antioxidant is preferably added to the polyurethane or the polyurethane composition. The type of the antioxidant is not particularly limited, and known substances can be used.

[0095] In addition, phosphorus-based antioxidants (e.g., tris(2,4-di-tert-butylphenyl) phosphite (Irgafos (trademark) 168, manufactured by BASF Japan Ltd.)) and vitamin E-based antioxidants (e.g., 3,4-dihydro-2,5,7,8-tetramethyl-2-(4,8,12-trimethyltridecyl)-2H-chromen-6-ol (Irganox (trademark) E 201, BASF Japan Ltd.)) can also be used.

[0096] When the polyurethane or the polyurethane composition should not be colored, the use of amine-based antioxidants is not preferred.

[0097] Based on the total mass of the thermoplastic polyurethane, the amount of the antioxidant can be from 0.01% by mass to 2% by mass, preferably from 0.1% by mass to 1% by mass, and particularly from 0.1% by mass to 0.5% by mass.

[0098] In addition, as discussed above, an ultraviolet absorber can be added to the polyurethane composition. The type of the ultraviolet absorber is not particularly limited, and known substances can be used. Specific examples of the ultraviolet absorber include cinnamic acid esters, diphenyl cyanoacrylates, formamidines, benzylidene malonic acid esters, diaryl butadienes, triazine-based and benzotriazole-based ultraviolet absorbers (e.g., Tinuvin (trademark) 329 manufactured by BASF Japan Ltd.).

[0099] As described above, the polyurethane according to the present invention exhibits excellent transparency and low haze, and these properties can be maintained for a long time even without relying on an ultraviolet absorber. Therefore, an ultraviolet absorber is generally not added to the polyurethane. In contrast, when the molded product is continuously exposed to strong ultraviolet rays, such as for outdoor equipment, it is preferable to use an ultraviolet absorber.

[0100] Similarly, as discussed above, a light stabilizer can be added to the polyurethane according to the present invention. The type of the light stabilizer is not particularly limited, and known substances can be used. As the light stabilizer, a hindered amine light stabilizer (HALS) can be used. Examples of HALS stabilizers as commercially available products are described in "Plastic Additives Handbook" (5th Edition, H. Zweifel, Hanser Publishing Co., Munich, 2001, pages 123 - 136). The hindered amine light stabilizer has a number average molecular weight preferably of 500 g / mol to 10,000 g / mol, more preferably 1,000 g / mol to 5,000 g / mol. Particularly preferred hindered amine light stabilizers are bis(1,2,2,6,6 - pentamethylpiperidinyl) sebacate (Tinuvin (trademark) 765, manufactured by BASF Japan Ltd.), the condensation product of 1 - hydroxyethyl - 2,2,6,6 - tetramethyl - 4 - hydroxypiperidine and succinic acid (Tinuvin (trademark) 622, manufactured by BASF Japan Ltd.), and polymeric sterically hindered amine (Chisorb (trademark) 622LT, Double Bond Chemical Ind., Co., Ltd.). It is particularly preferred to use the condensation product of 1 - hydroxyethyl - 2,2,6,6 - tetramethyl - 4 - hydroxypiperidine and succinic acid (Tinuvin (trademark) 622). Based on the mass of the polyurethane, the use concentration of the HALS compound is preferably 0.01% by mass to 3% by mass, more preferably 0.1% by mass to 2.0% by mass, and even more preferably 0.1% by mass to 1.0% by mass.

[0101] In addition, a nucleating agent can be added to the polyurethane according to the present invention. The type of the nucleating agent is not particularly limited. Known nucleating agents can be used. Specific examples include nucleating agents based on dibenzylidene sorbitol (e.g., Millad (trademark) NX8000 manufactured by Milliken Chemical Co., Ltd.), nucleating agents based on metal benzoates, nucleating agents based on phosphate salts, and nucleating agents based on rosin. Based on the mass of the polyurethane, the blending ratio of the nucleating agent can be 0.3% by mass or less, more preferably 0.1% by mass to 0.25% by mass. When the addition amount of the nucleating agent is 0.3% by mass or less, the haze value and yellowing resistance of the resulting polyurethane molded product become excellent.

[0102] The surface modifier can be used as another additive in the polyurethane according to the present invention. The type of the surface modifier is not particularly limited. Known surface modifiers such as waxes or lubricants can be used. Specific examples include petroleum-derived hydrocarbon waxes such as ozokerite, paraffin wax, montanic acid ester wax; animal waxes such as beeswax, shellac wax, wool wax; or vegetable waxes such as carnauba wax, candelilla wax, rice wax; fatty acid amide waxes such as ethylene bisstearamide (EBS), N,N'-ethylene bisoleamide (EBO) or erucamide; polyolefin waxes such as polyethylene wax, polypropylene wax, Fischer-Tropsch wax, polyethylene oxide wax and modified polyolefin waxes such as graft-type or copolymer-type polyolefins. In addition, acrylic polymer lubricants (for example, Metabrene L1000 manufactured by Mitsubishi Chemical Corporation) can be used as surface modifiers. In the present invention, montanic acid ester wax (for example, Licolub WE4 manufactured by Clariant Japan Co., Ltd.) and acrylic polymer lubricants are particularly preferably used. Thus, the product molded from the polyurethane will have improved lubrication characteristics and good mold release properties. In addition, the bleeding phenomenon over time can be restricted by adjusting the amount of the additive.

[0103] As described above, the surface modifier can be added alone or as a combination of two or more types. Based on the mass of the polyurethane, the amount of the surface modifier can be 0.01% by mass to 1% by mass, preferably 0.01% by mass to 0.5% by mass.

[0104] Known colorants can be added to the polyurethane composition according to the present invention. Its type is not particularly limited. Blue pigments can also be used as bluing agents to reduce the initial yellowness. In addition, by using a fluorescent brightener in combination, the appearance of the polyurethane composition can be further improved.

[0105] [Preparation of polyurethane composition (TPU composition)]

[0106] To prepare the TPU composition, that is, the mixture of the above-mentioned TPU and additional components, a predetermined amount of one or more additives is appropriately metered into the TPU and then mixed by means of known blending devices and equipment (including kneaders and stirrers). The TPU is usually processed into pellets or powders according to known methods such as injection molding, calendering or extrusion. For example, the TPU is supplied to a post-extruder and then kneaded and melted at a temperature of about 150 to 230 °C in an ambient atmosphere. Then, the TPU is extruded into the desired shape. Twin-screw stirrers including continuous kneading extruders, continuous single-screw or twin-screw stirrers can be used.

[0107] The TPU composition can be in the form of a powder, sheet, rod, sheet or block, or alternatively in the form of pellets or granules by, for example, strand cutting or underwater cutting.

[0108] [Manufacture of molded product]

[0109] The (TP composition thus obtained is molded, for example, by using a suitable molding device or mold into a product having a desired shape. Known molding devices or molds can be appropriately used as long as the polyurethane composition can be molded into the desired shape.

[0110] The application of the molded product obtained from the TPU composition is not particularly limited. The TPU of the present invention is suitable, for example, as a hard coating film especially for windows of transportation means or buildings because of its excellent transparency (which can be well maintained even after long-term exposure to environmental stress) and good hardness. Further applications of the TPU of the present invention include molded articles such as exterior parts of automobiles, motorcycles, bicycles, ships, trains or airplanes.

[0111] [Substrate]

[0112] The TPU itself or the TPU composition of the present invention can be applied to a substrate, for example, as a hard coating film on the substrate. Examples of the substrate include resins such as polycarbonate resin, polymethyl methacrylate resin, methyl methacrylate resin, transparent acrylonitrile-butadiene-styrene resin, transparent polystyrene resin, transparent epoxy resin, polyarylate, polysulfone, polyethersulfone, transparent nylon resin, transparent polybutylene terephthalate, transparent fluororesin, poly-4-methylpentene-1, transparent phenoxy resin, polyimide resin and transparent phenolic resin.

[0113] The present invention will now be illustrated with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, "parts" and "%" are based on mass.

[0114] Example

[0115] [Examples 1-1 to 1-9 and 2-1 to 2-3 and Comparative Examples 2-1 to 2-5 and 2-1 to 2-4]

[0116] <TPU synthesis>

[0117] The following operations were carried out for the examples and comparative examples by using the materials in the amounts shown in Table 1.

[0118] The polyol (A) and the chain extender (C) are quantitatively added to a cylindrical 2L-sized metal container at a temperature in the range of 90°C to 95°C. An antioxidant, a light stabilizer, an ultraviolet absorber, a lubricant, a nucleating agent, and a catalyst are added, and the mixture is stirred at 200 rpm - 300 rpm until the mixture is uniformly mixed. Then, the polyisocyanate (B) preheated to 50°C is loaded into the container, and the mixture is continuously stirred until the temperature reaches 105°C.

[0119] After reaching 105°C, the liquid mixture thus obtained is transferred to a Teflon (trademark) container, and then annealed at 95°C for 15 hours to increase the molecular weight to form a polymer. Thus, a TPU resin in the form of a plate is obtained. The slab is cut and crushed to form flakes.

[0120] The flakes are fed from a feeder into a twin-screw extruder (manufactured by WERNER&PFLEIDER-ER, ZSK30: )). The temperature in the area from the hopper to the die head is set to 180°C - 210°C. While the screw rotates at a speed of 100 rpm to 110 rpm, the flakes are melted and kneaded, and at the same time, extruded in the form of strands. These strands are placed in a water bath, cooled therein, and then cut by a granulator to continuously obtain uniformly prepared pellet-like TPU compositions.

[0121] <Molding of test sample>

[0122] Using an injection molding machine (TM130F2: manufactured by Toyo Machinery&Metal Co., Ltd.), the above TPU composition is injection molded under the following conditions. Regarding the molding temperature, the nozzle tip of the injection molding machine is set to have a temperature in the range of 200°C to 210°C. The temperature of the barrel is sequentially decreased by 5°C toward the hopper side. The temperature of the lower part of the hopper is set to 180°C to 190°C. The mold temperature is set at 25°C.

[0123] The TPU composition is heated and melted, and then by using a screw, injection is carried out at an injection speed of 10% (11 mm / sec) and an injection pressure of 90 kgf / (1130 kgf / cm 2 ). After maintaining a pressure of 80 kgf / (1070 kgf / cm 2 ) for 40 seconds to cool the mold, a plate-shaped molded product with a length of 160 mm, a width of 105 mm, and a thickness of 2 mm is obtained. It is found that all test samples have excellent surface smoothness, without depressions or scratches on them. These samples are used to evaluate the Shore A hardness. The same samples are also used to evaluate the optical properties.

[0124] It was found that the test sample had excellent surface smoothness, with no depressions or scratches thereon. In this article, the test sample (initial state sample) cooled to 25 °C under atmospheric pressure and maintained for 88 hours under the same conditions was used for the following tests.

[0125] <Determination of HS content (%)>

[0126] The hard segment (HS) in the initial state sample was set to have the value described in Table 1 by quantitatively adding polyol (A), isocyanate (B), and chain extender (C) so as to satisfy the following formula:

[0127] Content of HS: { (molar amount of isocyanate (B) - molar amount of OH end groups of polyol (A)) * (mass of isocyanate (B)) + (mass of chain extender (C))} / (mass of isocyanate (B) + mass of chain extender (C) + mass of polyol (A)) × 100

[0128] [Evaluation of optical properties]

[0129] <Evaluation of total light transmittance (TT)>

[0130] The total light transmittance of the initial state sample was evaluated according to JIS K 7361-1:1997. The obtained value was recorded as the initial total light transmittance, i.e., "initial TT" in Table 1.

[0131] <Evaluation of initial haze>

[0132] The haze value of the initial state sample was evaluated according to JIS K 7136:2000, and the measured value was recorded as "initial haze" in Table 1.

[0133] Generally, the transparency of a sample is affected by haze. Generally, a sample with an initial total light transmittance of 85% or more and an initial haze of 10% or less is acceptable for products requiring transparency.

[0134] When the initial total light transmittance is 85% or more, particularly 90% or more, and specifically 95% or more, and the initial haze is 5% or less, particularly 3.5 or less, and specifically 3.0 or less, good transparency is perceived. When the initial state sample has a thickness of 2 mm or less, particularly 150 μm or less, the above initial haze value is applicable.

[0135] <Evaluation of difference in haze value after Taber abrasion test>

[0136] To evaluate the abrasion resistance of the samples, the Taber abrasion test was carried out on the samples for 500 revolutions according to ASTM D1044 (Taber 500). The haze value of the samples after the Taber abrasion test was measured according to JIS K 7136:2000. The difference (Δhaze) (%) between the haze value of the samples after the Taber abrasion test and the initial haze was obtained:

[0137] Δhaze (%) = haze (%) of the samples after Taber 500 - initial haze (%)

[0138] The results are shown as "Taber 500 (Δhaze)" in Table 1. Undoubtedly, the lower the Δhaze value, the better the abrasion resistance.

[0139] [Evaluation of mechanical properties]

[0140] <Evaluation of Shore A hardness>

[0141] The Shore A hardness of the test samples was measured according to JIS K 7311-1995. For each of the examples and comparative examples, the Shore A hardness was measured using a Type A durometer with 3 stacked test samples having a total thickness of 6 mm. The evaluation results are shown in Table 1.

[0142]

[0143] The materials described in Table 1 are as follows:

[0144] Polycarbonate polyol: 1,6-hexanediol polycarbonate with number average molecular weight Mn of 500, 1000, 2000, and 3000

[0145] H6XDI: 1,4-bis(isocyanatomethyl)cyclohexane

[0146] 1,3-PD: 1,3-propanediol

[0147] 1,4-BD: 1,4-butanediol

[0148] 1,9-ND: 1,9-nonanediol

[0149] Table 2 shows the weight ratios of the polyol (A) and the chain extender (C) calculated from the masses of the polyol (A) and the chain extender (C) in Table 1, respectively.

[0150] Table 2

[0151]

[0152] As can be seen from Table 1, the TPU composition of the present invention not only exhibits excellent optical properties but also exhibits good mechanical properties.

[0153] It should be understood that the novel polyurethanes and compositions described herein can be modified and changed as long as they fall within the scope of the appended claims or their equivalents.

Claims

1. A thermoplastic polyurethane, which is a product from a reaction mixture comprising: (A) a polycarbonate polyol having a number average molecular weight Mn greater than 500 and less than 2000, (B) an alicyclic polyisocyanate, and (C) a chain extender, and wherein, based on the total mass of the thermoplastic polyurethane, the thermoplastic polyurethane has a hard segment (HS) accounting for less than 40% by mass.

2. A thermoplastic polyurethane, which is a product from a reaction mixture comprising: (A) a polycarbonate polyol having a number average molecular weight Mn greater than 500 and less than 3000, (B) an alicyclic polyisocyanate, and (C) at least two types of chain extenders, wherein, based on the total mass of the thermoplastic polyurethane, the thermoplastic polyurethane has a hard segment (HS) accounting for less than 50% by mass.

3. The thermoplastic polyurethane according to claim 1 or 2, wherein the polycarbonate polyol (A) is a reaction product of a C2-C 16 alkylene diol and a carbonic acid diester.

4. The thermoplastic polyurethane according to claim 1, wherein the chain extender (C) is at least one selected from the group consisting of: 1,2-ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 3-methyl-1,5-pentanediol, 2-methyl-1,8-octanediol, diethylene glycol, and dipropylene glycol.

5. The thermoplastic polyurethane according to claim 2, wherein the chain extender (C) comprises a combination of at least two selected from the group consisting of: 1,2-ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 3-methyl-1,5-pentanediol, 2-methyl-1,8-octanediol, diethylene glycol, and dipropylene glycol.

6. The thermoplastic polyurethane according to claim 1, 2, 4 or 5, wherein, based on the total mass of the polycarbonate polyol (A), the alicyclic polyisocyanate (B) and the chain extender(s) / chain extender (C), the concentration of the alicyclic polyisocyanate (B) is in the range of 1.2 mol / kg to 1.8 mol / kg.

7. A polyurethane resin composition, which comprises: the thermoplastic polyurethane according to claim 1 or 2, and an antioxidant.

8. A molded product, which is obtained from the polyurethane composition in any one of the resin compositions according to claim 7.

9. The molded product according to claim 8, wherein the molded product is in the form of a sheet configured to be applied to a substrate for resin glass.

10. The molded product according to claim 9, wherein the sheet having a thickness of 2 mm has an initial haze value of 5% or less.

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