Modified polyurethane bearing substrate

Abstract

The present invention provides a modified polyurethane bearing substrate formed from a modified polyurethane. The modified polyurethane includes a soft segment formed from a polyol and a hard segment formed from a diisocyanate and a chain extender, the chain extender being a diacid anhydride. The common logarithm of the ratio of the storage modulus of the modified polyurethane at -30°C to the storage modulus of the modified polyurethane at 150°C is from 0.40 to 1.30.

Description

Technical Field

[0001] This invention relates to a modified polyurethane support substrate, and more particularly to a modified polyurethane support substrate with good heat resistance. Background Technology

[0002] Since the emergence of the concept of the metaverse, wearable devices related to augmented reality (AR) and virtual reality (VR) have gradually gained attention.

[0003] In the research and development of wearable devices, improving their functionality and practicality has become a key research focus. To enhance these aspects, the market demand for flexible printed circuit boards (FPCs) is increasing. Besides requiring good elasticity and flexibility, FPCs also need excellent heat resistance to meet manufacturing process requirements.

[0004] Currently, most smart fabric and interactive textiles (SFIT) on the market (such as heart rate sensing clothing) use polyurethane as the material for flexible printed circuit boards because polyurethane is soft and has good wear resistance, impact resistance, and elasticity. However, polyurethane has poor heat resistance and cannot withstand high processing temperatures. Therefore, how to provide polyurethane materials with good heat resistance has become one of the important issues that this industry seeks to solve. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a modified polyurethane load-bearing substrate to address the shortcomings of the prior art.

[0006] To address the aforementioned technical problems, one technical solution adopted by this invention is to provide a modified polyurethane support substrate. The modified polyurethane support substrate is formed from a modified polyurethane. The modified polyurethane comprises a soft segment and a hard segment; the soft segment is formed from a polyol, and the hard segment is formed from a diisocyanate and a chain extender, wherein the chain extender is a dianhydride. The commonly used logarithm of the ratio of the storage modulus of the modified polyurethane at -30°C to its storage modulus at 150°C is 0.40 to 1.30.

[0007] Preferably, the chain extender is selected from the group consisting of: pyromellitic dianhydride (PMDA), 1,2,4,5-cyclohexanetetracarboxylic dianhydride (HPMDA), 4,4'-biphthalic anhydride (BPDA), 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), 4,4'-oxydiphthalic anhydride (ODPA), and 3,4,9,10-perylenetetracarboxylic dianhydride. dianhydride (PTCDA), 4,4'-(4,4'-isopropylidenediphenoxy)bis(phthalicanhydride) (BPADA) and mixtures thereof.

[0008] Preferably, the chain extender content is 10% to 35% by weight, with the total weight of the modified polyurethane carrier substrate being 100% by weight.

[0009] Preferably, the content of hard segments is 20 to 70% by weight, based on 100% of the total weight of the modified polyurethane. More preferably, the content of hard segments is 30 to 50% by weight.

[0010] Preferably, the hard segment includes a crankshaft structure that alters the molecular chain orientation of the modified polyurethane. The crankshaft structure is formed from diisocyanate.

[0011] Preferably, the diisocyanate forming the crankshaft structure is selected from the group consisting of: 1,3-bis(isocyanatomethyl)cyclohexane (H6XDI), isophorone diisocyanate (IPDI), 1,3-bis(2-isocyanato-2-propyl)benzene (TMXDI), m-xylyene diisocyanate (m-XDI), 2,4'-methylenebis(phenyl isocyanate) (2,4'-MDI), 2,2'-methylenebis(phenyl isocyanate) (2,2'-MDI), and combinations thereof.

[0012] Preferably, the crankshaft structure content is 10% to 25% by weight, with the total weight of the modified polyurethane being 100% by weight.

[0013] Preferably, the hard segment further comprises a straight-chain structure, wherein the diisocyanate forming the straight-chain structure is selected from the group consisting of: 4,4'-methylenebis(phenylisocyanate), 4,4'-MDI, 4,4'-diisocyanato-methylenedicyclohexane, H12MDI, hexamethylene diisocyanate, HDI, and combinations thereof.

[0014] Preferably, the mass ratio of the diisocyanate forming the crankshaft structure to the diisocyanate forming the linear structure is 1:0.8 to 1.2.

[0015] To address the aforementioned technical problems, another technical solution adopted by the present invention is to provide a modified polyurethane support substrate. The modified polyurethane support substrate is formed from a modified polyurethane, which comprises a soft segment and a hard segment. The hard segment includes a crankshaft structure to change the molecular chain orientation of the modified polyurethane. The commonly used logarithm of the ratio of the storage modulus of the modified polyurethane at -30°C to its storage modulus at 150°C is 0.40 to 1.30.

[0016] One of the beneficial effects of the present invention is that the modified polyurethane carrier substrate provided by the present invention can have good heat resistance through the technical solution that "the chain extender is dianhydride" and "the common logarithm of the ratio of the storage modulus of the modified polyurethane at -30°C to the storage modulus at 150°C is 0.40 to 1.30".

[0017] To further understand the features and technical content of this invention, please refer to the following detailed description of the invention; however, it is for reference and illustration only and is not intended to limit the invention. Detailed Implementation

[0018] The following specific examples illustrate the embodiments of the "modified polyurethane carrier substrate" disclosed in this invention. Those skilled in the art can understand the advantages and effects of this invention from the content disclosed in this specification. This invention can be implemented or applied through other different specific embodiments, and the details in this specification can also be modified and changed based on different viewpoints and applications without departing from the concept of this invention. The following embodiments will further describe the relevant technical content of this invention in detail, but the disclosed content is not intended to limit the scope of protection of this invention. Furthermore, the term "or" as used herein may include, depending on the actual situation, any combination of any one or more of the associated listed items.

[0019] This invention provides a modified polyurethane substrate for supporting integrated circuits, enabling its application in smart textiles. The modified polyurethane substrate exhibits good elastic strength and heat resistance, making it suitable for manufacturing flexible printed circuit boards. The thickness of the modified polyurethane substrate is not limited; specifically, it can be a film-like substrate or a plate-like substrate well-known in the art.

[0020] The modified polyurethane carrier substrate of this invention is made of modified polyurethane. The modified polyurethane is composed of alternating soft and hard segments. This invention improves the elastic strength and heat resistance of the modified polyurethane by adjusting the structure of the hard segments. Furthermore, the modified polyurethane of this invention maintains good elastic strength regardless of whether the environment is high or low temperature.

[0021] It is worth noting that in existing technologies, the elastic strength of modified polyurethane is mostly adjusted by changing the structure of the soft segments or by changing the ratio of soft to hard segments. In contrast, this invention achieves the effect of adjusting the elastic strength of modified polyurethane by changing the structure of the hard segments.

[0022] In this specification, the present invention evaluates the elastic strength of modified polyurethane by measuring its storage modulus (E'). Furthermore, the present invention measures the storage modulus of the modified polyurethane at low temperature (-30°C) and high temperature (150°C), and takes the common logarithm (log10) of the ratio of the storage moduli (log(E'(-30°C) / E'(150°C))) as a reference for evaluating the difference in elastic strength of the material at low and high temperatures.

[0023] In this invention, the commonly used logarithm of the ratio of the storage modulus of the modified polyurethane at -30°C to its storage modulus at 150°C is 0.40 to 1.30. Preferably, the commonly used logarithm of the ratio of the storage modulus of the modified polyurethane at -30°C to its storage modulus at 15°C is 0.7 to 1.2. Specific measurement methods and results will be described later.

[0024] In this invention, the content of soft segments and hard segments can be adjusted according to performance requirements. In some embodiments, the content of hard segments is 20% to 70% by weight, with the total weight of the modified polyurethane as 100% by weight. However, the invention is not limited thereto.

[0025] In the modified polyurethane of this invention, the hard segments are formed from diisocyanate and a chain extender. The soft segments are formed from polyols.

[0026] Chain extender

[0027] The chain extender is a dianhydride, which improves the heat resistance and physical properties of the modified polyurethane. Even at higher temperatures, the modified polyurethane retains high thermal latent recovery. Therefore, the modified polyurethane of this invention can withstand higher processing temperatures and meets the process requirements of flexible printed circuit boards.

[0028] In one exemplary embodiment, the number-average molecular weight of the chain extender is from 150 g / mol to 550 g / mol. However, the invention is not limited thereto.

[0029] In one exemplary embodiment, the chain extender is a dianhydride. Preferably, the chain extender may be phenylmethyltetracarboxylic anhydride, 1,2,4,5-cyclohexanetetracarboxylic anhydride, bisphenyltetracarboxylic anhydride, 3,3',4,4'-benzylphenol tetracarboxylic anhydride, 4,4'-(hexafluoroisopropene)dianhydride, 4,4'-oxobisphthalic anhydride, 3,4,9,10-perylenetetracarboxylic anhydride, 4,4'-(4,4'-isopropyldiphenoxy)bis(phthalic anhydride), or mixtures thereof. More preferably, the chain extender is phenylmethyltetracarboxylic anhydride. However, the invention is not limited thereto.

[0030] In one exemplary embodiment, the chain extender content is 10% to 35% by weight, with the total weight of the modified polyurethane being 100% by weight. However, the invention is not limited thereto.

[0031] [Diisocyanate]

[0032] The hard segments can be formed from one or more diisocyanates. Some of the diisocyanates form a crankshaft structure after the synthesis reaction, while others form a straight-chain structure.

[0033] In some embodiments, the diisocyanate may be entirely formed into a crankshaft structure. In some embodiments, the diisocyanate may also be entirely formed into a linear structure. In some embodiments, a portion of the diisocyanate forms the crankshaft structure, while a portion forms a linear structure.

[0034] The presence of the crankshaft structure alters the molecular chain orientation of the modified polyurethane, resulting in excellent elastic strength in the modified polyurethane of this invention. In a preferred embodiment, the hard segments in the modified polyurethane include the crankshaft structure.

[0035] The main structure of the crankshaft can be composed of cyclohexane or one or more benzene rings. The crankshaft structure has two functional groups, which are attached to the cyclohexane or one or more benzene rings. To achieve the effect of altering the molecular chain orientation of the modified polyurethane, the two functional groups are not positioned opposite each other on the main structure.

[0036] Specifically, when the main structure of the crankshaft is a benzene ring, the two functional groups will not be located at the para position of the benzene ring. When the main structure of the crankshaft contains two benzene rings (e.g., diphenylmethane), the two functional groups will not be located at the 4 positions of the two benzene rings respectively. Similarly, when the main structure of the crankshaft is cyclohexane, the two functional groups will not be located at opposite positions on the cyclohexane ring.

[0037] In one exemplary embodiment, when the main structure of the crankshaft is a benzene ring, the two functional groups can be disposed at the meta position of the benzene ring. When the main structure of the crankshaft includes two benzene rings (e.g., diphenylmethane), the two functional groups can be disposed at the 2 position of one benzene ring and the 4 position of the other benzene ring, respectively, or the two functional groups can be disposed at the 2 position of each of the two benzene rings.

[0038] Preferably, the crankshaft structure is formed of an aliphatic isocyanate, and the two functional groups of the crankshaft structure are isocyanate groups. For example, when the main structure of the crankshaft structure is cyclohexane, the diisocyanate forming the crankshaft structure can be 1,3-bis(methyl isocyanate)cyclohexane or isofrone diisocyanate.

[0039] Preferably, the crankshaft structure is formed from an aromatic isocyanate, and the two functional groups of the crankshaft structure are isocyanate groups. For example, when the main structure of the crankshaft structure is a benzene ring, the diisocyanate forming the crankshaft structure can be 1,3-bis(2-isocyano-2-propyl)benzene or isophthalic dimethyl isocyanate. When the main structure of the crankshaft structure contains two benzene rings (e.g., diphenylmethane), the diisocyanate forming the crankshaft structure can be 2,4'-diphenylmethane diisocyanate or 2,2'-diphenylmethane diisocyanate. In some embodiments, both isophthalic dimethyl isocyanate and 2,4'-diphenylmethane diisocyanate may be used simultaneously as monomers forming the crankshaft structure.

[0040]

[0041] In one exemplary embodiment, the crankshaft structure content is 10% to 25% by weight, with a total weight of 100% of the modified polyurethane; more preferably, the crankshaft structure content can be 12% or 23% by weight. However, the invention is not limited thereto.

[0042] The number-average molecular weight of the diisocyanate forming the crankshaft structure can be from 150 g / mol to 300 g / mol. On the other hand, the number-average molecular weight of the diisocyanate forming the linear structure can be from 100 g / mol to 400 g / mol. However, the present invention is not limited thereto.

[0043] For example, the diisocyanate forming the linear structure can be 4,4'-diphenylmethane diisocyanate, 4,4'-diisocyanate dicyclohexylmethane, hexamethylene diisocyanate, or combinations thereof. Preferably, the diisocyanate forming the linear structure is 4,4'-diphenylmethane diisocyanate. However, the invention is not limited thereto.

[0044] It is worth noting that the biggest difference between diisocyanates forming crankshaft structures and those forming straight-chain structures lies in their different structures. In other words, diisocyanates forming crankshaft structures and those forming straight-chain structures can be isomers.

[0045] When the diisocyanate forming the crankshaft structure and the diisocyanate forming the linear structure are isomers, the modified polyurethane can exhibit a lower glass transition temperature and better elasticity and flexibility. For example, the crankshaft structure is formed by 2,4'-diphenylmethane diisocyanate, and the linear structure is formed by 4,4'-diphenylmethane diisocyanate.

[0046] In one exemplary embodiment, the mass ratio of the diisocyanate forming the crankshaft structure to the diisocyanate forming the linear structure is 1:0.8 to 1.2. However, the invention is not limited thereto.

[0047] [Polypolyols]

[0048] The addition of polyols can lower the glass transition temperature of modified polyurethane, thereby improving its elastic strength. In some embodiments, the polyol may be a polyester polyol (e.g., polydibutyl adipate or polycaprolactone), a polycarbonate polyol, or a polyether polyol (e.g., polytetramethylene ether glycol). However, the invention is not limited thereto.

[0049] In some embodiments, the number average molecular weight of the polyol is from 400 g / mol to 4000 g / mol. However, the invention is not limited thereto.

[0050] The modified polyurethane of the present invention can be represented by formula (I):

[0051]

[0052] Formula (I).

[0053] In formula (I), R1 can be formed from the following diisocyanates: 1,3-bis(methyl)cyclohexane, isoflavone diisocyanate, 1,3-bis(2-isocyano-2-propyl)benzene, isophenyl dimethyl isocyanate, 2,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diisocyanate dicyclohexylmethane, hexamethylene diisocyanate, and combinations thereof. R2 can be formed from a polyol with a number average molecular weight of 50 g / mol to 4000 g / mol. R3 can be cyclohexane, benzene, biphenyl, benzophenone, diphenylpropane, diphenyl ether, tetracarboxylic acid, or phenolic methane having a tetravalent bond. n and m are each independent integers between 1 and 100.

[0054] More specifically, the modified polyurethane of the present invention can be represented by formula (II). In formula (II), n and m are each an integer between 1 and 100.

[0055]

[0056] Equation (II).

[0057] In equation (II), It is selected from the group consisting of the following:

[0058]

[0059] The following specific examples illustrate the synthesis method of modified polyurethane and the formation of the modified polyurethane carrier substrate.

[0060] [Example 1]

[0061] 16.8 g of 2,4'-diphenylmethane diisocyanate (2,4'-MDI) (crankshaft structure), 16.8 g of 4,4'-diphenylmethane diisocyanate (4,4'-MDI) (linear structure), and 100 g of polycaprolactone (PCL) were mixed at 80°C and stirred at 300 rpm to form a polyurethane prepolymer. In Example 1, the theoretically bondable isocyanate groups (NCO) in the polyurethane prepolymer were 5.20%.

[0062] 17.2 g of phenylmethyltetrahydrocarbon anhydride (PMDA) (chain extender) was dissolved in N-methylpyrrolidone (NMP) and added to a polyurethane prepolymer at 60°C. The mixture was then stirred at 300 rpm at 60°C to obtain a modified polyurethane solution with a solid content of 45 wt%. The modified polyurethane solution was centrifuged, dried (at 70°C for 4 hours), and cured (at 180°C for 2 hours) to obtain the modified polyurethane of this invention, which can be further used to prepare a modified polyurethane carrier substrate.

[0063] In Example 1, the content of chain extender (benzopyrene) in the modified polyurethane was 11.4 wt%. The content of crankshaft structure in the modified polyurethane was 11.1 wt%.

[0064] [Examples 2 to 4]

[0065] The synthesis methods of the modified polyurethane support substrates in Examples 2 to 4 are similar to those in Example 1, the difference being the different amounts of diisocyanate and chain extender added. Examples 1 to 4 can be used to compare the effects of different hard segment contents on the properties of the modified polyurethane. The theoretically bondable isocyanate groups (NCO) in the polyurethane prepolymer, the content of the chain extender, and the crankshaft structure content in the modified polyurethane are shown in Table 1.

[0066] In Example 2, the amount of 2,4'-diphenylmethane diisocyanate (2,4'-MDI) added was 23.1 g, the amount of 4,4'-diphenylmethane diisocyanate (4,4'-MDI) added was 23.1 g, and the amount of benzopyrene (PMDA) added was 27.7 g.

[0067] In Example 3, the amount of 2,4'-diphenylmethane diisocyanate (2,4'-MDI) added was 31.7 g, the amount of 4,4'-diphenylmethane diisocyanate (4,4'-MDI) added was 31.7 g, and the amount of benzopyrene (PMDA) added was 42.1 g.

[0068] In Example 4, the amount of 2,4'-diphenylmethane diisocyanate (2,4'-MDI) added was 98.9 g, the amount of 4,4'-diphenylmethane diisocyanate (4,4'-MDI) added was 98.9 g, and the amount of phenylmethylenetetramine anhydride (PMDA) added was 154.5 g. It is worth noting that the formulation in Example 4, due to the excessive addition of diisocyanates, resulted in the modified polyurethane being unable to be used as a modified polyurethane carrier substrate.

[0069] [Examples 5 to 8]

[0070] The synthesis methods of the modified polyurethanes in Examples 5 to 8 are similar to those in Example 1, except that the amounts of diisocyanate and chain extender added are different, and different diisocyanates are used. Examples 5 to 8 can be used to compare the effects of different hard segment structures on the properties of modified polyurethanes. The types of diisocyanates, the theoretically bondable isocyanate groups (NCO) in the polyurethane prepolymer, the content of the chain extender, and the content of crankshaft structures in the modified polyurethane are shown in Table 1.

[0071] In Example 5, the diisocyanate was 4,4'-diphenylmethane diisocyanate (4,4'-MDI) (linear structure). The amount of 4,4'-diphenylmethane diisocyanate (4,4'-MDI) added was 46.5 g, and the amount of benzopyrene (PMDA) added was 27.6 g.

[0072] In Example 6, the diisocyanate was 4,4'-diisocyanato-methylenedicyclohexane (H12MDI) (linear structure). The amount of 4,4'-diisocyanato-methylenedicyclohexane added was 47.3 g, and the amount of phenylmethyltetrahydrocarbon anhydride (PMDA) added was 27.3 g.

[0073] In Example 7, the diisocyanate was hexamethylene diisocyanate (HDI) (linear structure). The amount of hexamethylene diisocyanate added was 35.0 g, and the amount of benzopyrene (PMDA) added was 32.4 g.

[0074] In Example 8, the diisocyanate was m-xylylene diisocyanate (m-XDI) (crankshaft structure). The amount of m-xylylene diisocyanate added was 37.8 g, and the amount of phenyl pyromellitic anhydride (PMDA) added was 31.1 g.

[0075] [Comparative Example 1]

[0076] 29.2 g of 2,4'-diphenylmethane diisocyanate (2,4'-MDI) (crankshaft structure), 29.2 g of 4,4'-diphenylmethane diisocyanate (4,4'-MDI) (linear structure), and 100 g of polycaprolactone (PCL) were mixed at 80°C and stirred at 300 rpm to form a polyurethane prepolymer. In Comparative Example 1, the theoretically bondable isocyanate groups (NCO) in the polyurethane prepolymer were 9.58%.

[0077] 15.6 g of 1,4-butanediol (1,4-BDO) was added to a polyurethane prepolymer at 70°C. The mixture was then stirred to obtain a polyurethane colloid with a solid content of 100 wt%. The polyurethane colloid was centrifuged, dried (at 100°C for 2 hours), and cured (at 100°C for 15 hours) to obtain polyurethane, which can be used to prepare a polyurethane substrate.

[0078] In Comparative Example 1, the content of chain extender (1,4-butanediol) in the polyurethane was 8.97 wt%. The content of crankshaft structure in the polyurethane was 16.8 wt%.

[0079] [Feature Testing]

[0080] To facilitate comparison of the differences between the modified polyurethane of the present invention and existing polyurethanes, the modified polyurethane support substrates of Examples 1 to 3, 5 to 8 and the polyurethane support substrate of Comparative Example 1 were subjected to characteristic tests, and the results are listed in Table 2.

[0081] In Table 2, the Young's modulus, tensile strength, and elongation at break of the modified polyurethane load-bearing substrate were measured according to the standard test method of ASTM D638 (type V). Toughness was obtained by calculating the area under the stress-strain curve.

[0082] In Table 2, the glass transition temperature, storage modulus at -30°C (E'(-30°C)), and storage modulus at 150°C (E'(150°C)) of the modified polyurethane carrier substrate were measured using a dynamic mechanical analyzer (brand: TECHMAX, model: TA7000). The ratio of the storage moduli divided by the storage modulus was taken as the common logarithm (log10) (log(E'(-30°C) / E'(150°C))) as a reference for evaluating the difference in elastic strength of the material at low and high temperatures.

[0083] In Table 2, the coefficient of thermal expansion and thermal latent recovery of the modified polyurethane were measured using a thermomechanical analyzer (brand: TA, model: TMA450). The thermal latent recovery was measured by applying an external force of 0.05 N at 150°C for 10 minutes, releasing the external force for 20 minutes, and then calculating the recovery rate.

[0084] In Table 2, the 5 wt% thermogravimetric loss and ash content of the modified polyurethane were measured using a thermogravimetric analyzer (brand: HITACHI, model: STA7200).

[0085] In Table 2, the 25% permanent deformation rate of the modified polyurethane load-bearing substrate was measured according to the standard test method of ISO 2285.

[0086] In Table 2, the moisture absorption rate of the modified polyurethane carrier substrate was measured according to the standard test method of ASTM D570.

[0087] Table 1

[0088]

[0089] Table 2

[0090]

[0091] As can be seen from the results in Table 2, the modified polyurethane substrate of the present invention has better physical properties (e.g., Young's coefficient and toughness) compared to existing polyurethane films.

[0092] According to Examples 1 to 3, as the content of the chain extender (phenylene pyromellitic anhydride) increases, the Young's modulus of the modified polyurethane substrate also increases. To balance the elastic and mechanical strength of the modified polyurethane substrate, the chain extender content is preferably 10% to 35% by weight, with the total weight of the modified polyurethane substrate as 100% by weight. More preferably, the chain extender content is 10% to 25% by weight. Even more preferably, the chain extender content is 12% to 22% by weight.

[0093] In this invention, the Young's modulus of the modified polyurethane load-bearing substrate is from 20 MPa to 400 MPa, preferably from 25 MPa to 350 MPa. The tensile strength of the modified polyurethane load-bearing substrate is from 10 MPa to 65 MPa, preferably from 14 MPa to 63 MPa. The toughness of the modified polyurethane load-bearing substrate is 4.5 GJ / m. 3 Up to 18 GJ / m 3 Preferably, the modified polyurethane load-bearing substrate has a toughness of 5 GJ / m. 3 Up to 15 GJ / m 3 The elongation of the modified polyurethane carrier substrate is 300% to 700%, preferably 350% to 680%.

[0094] As can be seen from the results in Table 2, compared with existing polyurethane films, the modified polyurethane carrier substrate of the present invention has better heat resistance (e.g., coefficient of thermal expansion, thermal creep recovery).

[0095] According to Examples 1 to 3, the heat resistance of the modified polyurethane substrate increases with the increase of the chain extender (benzopyrene) content. However, when the chain extender content is too high (Example 4, hard segment content greater than 75 wt%), brittleness occurs, and a continuous film cannot be formed.

[0096] In this invention, the coefficient of thermal expansion of the modified polyurethane support substrate is from 1.5 μm / °C to 4.0 μm / °C, preferably from 1.8 μm / °C to 3.9 μm / °C. The modified polyurethane support substrate exhibits a 50% to 80% thermal recovery at 150°C, preferably from 60% to 75%. The glass transition temperature of the modified polyurethane support substrate is from -35°C to -60°C. The storage modulus of the modified polyurethane support substrate at -30°C is 2.0 × 10⁻⁶. 7 Up to 5.0×10 9 Preferably, the modified polyurethane substrate has a storage modulus of 3.0 × 10⁻⁶ at -30°C.7 Up to 2.0×10 9 The storage modulus of the modified polyurethane substrate at 150°C is 5.5 × 10⁻⁶. 6 Up to 3×10 8 Preferably, the modified polyurethane substrate has a storage modulus of 5.7 × 10⁻⁶ at 150°C. 6 Up to 2.0×10 8 The ratio of the common logarithm of the storage modulus of modified polyurethane at -30°C to the common logarithm of its storage modulus at 150°C is 0.40 to 1.30, preferably 0.7 to 1.2.

[0097] Compared to existing polyurethane films, the modified polyurethane substrate of this invention has a lower moisture absorption rate, making it suitable for use in the manufacture of flexible printed circuit boards. Specifically, the moisture absorption rate of the modified polyurethane substrate is less than 1.12%, and preferably, it is less than 0.8%.

[0098] [Beneficial Effects of the Examples]

[0099] One of the beneficial effects of the present invention is that the modified polyurethane carrier substrate provided by the present invention can have good heat resistance through the technical solution that "the chain extender is dianhydride" and "the ratio of the common logarithm of the storage modulus of the modified polyurethane at -30°C to the common logarithm of the storage modulus at 150°C is 0.40 to 1.30".

[0100] Furthermore, this invention improves the heat resistance of the modified polyurethane load-bearing substrate by selecting specific chain extenders and controlling their content. Additionally, by incorporating a crankshaft structure into the hard chain segments (adjusting the structure of the hard chain segments), the elastic strength of the modified polyurethane load-bearing substrate is improved.

[0101] The content disclosed above is only a preferred and feasible embodiment of the present invention, and is not intended to limit the scope of protection of the claims of the present invention. Therefore, all equivalent technical changes made based on the content of the present invention specification are included within the scope of protection of the claims of the present invention.

Claims

1. A modified polyurethane load-bearing substrate, characterized in that, The modified polyurethane carrier substrate is formed of a modified polyurethane, wherein the modified polyurethane comprises a soft segment and a hard segment, the soft segment being formed of a polyol, the hard segment being formed of a diisocyanate and a chain extender, the chain extender being a dianhydride, the commonly used logarithm of the ratio of the storage modulus of the modified polyurethane at -30°C to the storage modulus at 150°C is 0.40 to 1.30, the chain extender content is 10% to 35% by weight, and the hard segment content is 30% to 50% by weight, with the total weight of the modified polyurethane as 100% by weight.

2. The modified polyurethane carrier substrate according to claim 1, characterized in that, The chain extender is selected from the group consisting of: phenylpyridine, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, bisphenyltetracarboxylic anhydride, 3,3',4,4'-benzylphenol tetracarboxylic anhydride, 4,4'-(hexafluoroisopropene) dianhydride, 4,4'-oxobisphthalic anhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 4,4'-(4,4'-isopropyldiphenoxy)bis(phthalic anhydride), and mixtures thereof.

3. The modified polyurethane carrier substrate according to claim 1, characterized in that, The hard segment includes a crankshaft structure that alters the molecular chain orientation of the modified polyurethane, and the crankshaft structure is formed from the diisocyanate.

4. The modified polyurethane carrier substrate according to claim 3, characterized in that, The diisocyanate forming the crankshaft structure is selected from the group consisting of: 1,3-di(methyl)cyclohexane, isoflavone diisocyanate, 1,3-bis(2-isocyano-2-propyl)benzene, isophenyl dimethyl isocyanate, 2,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, and combinations thereof.

5. The modified polyurethane carrier substrate according to claim 3, characterized in that, The crankshaft structure comprises 10% to 25% of the total weight of the modified polyurethane, with the total weight of the modified polyurethane being 100% by weight.

6. The modified polyurethane carrier substrate according to claim 3, characterized in that, The hard segment further includes a straight-chain structure, wherein the diisocyanate forming the straight-chain structure is selected from the group consisting of: 4,4'-diphenylmethane diisocyanate, 4,4'-diisocyanate dicyclohexylmethane, hexamethylene diisocyanate, and combinations thereof.

7. The modified polyurethane carrier substrate according to claim 6, characterized in that, The mass ratio of the diisocyanate forming the crankshaft structure to the diisocyanate forming the linear structure is 1:0.8 to 1.

2.

8. A modified polyurethane load-bearing substrate, characterized in that, The modified polyurethane carrier substrate is formed of a modified polyurethane, wherein the modified polyurethane comprises a soft segment and a hard segment, the hard segment comprising a crankshaft structure to change the molecular chain orientation of the modified polyurethane, the common logarithm of the ratio of the storage modulus of the modified polyurethane at -30°C to the storage modulus at 150°C is 0.40 to 1.30, the hard segment comprises a chain extender, the content of the chain extender being 10% to 35% by weight per 100% of the total weight of the modified polyurethane, and the content of the hard segment being 30% to 50% by weight.

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