Polysilsesquioxane liquid precursor, cured object, and production methods therefor

Abstract

The present invention provides: a method for producing a thick polysilsesquioxane cured object that has high hardness and excellent transparency; a polysilsesquioxane liquid precursor for producing such a cured object; and a cured object. This polysilsesquioxane liquid precursor includes a copolymer of a trifunctional silicon alkoxide and a difunctional silicon alkoxide, the residual silanol fraction fSiOH of the copolymer being 0.02–0.3.

Description

Polysilsesquioxane-based liquid precursor, cured product, and method for producing the same

[0001] The present invention relates to a polysilsesquioxane-based liquid precursor, a cured product thereof, and methods for producing the same.

[0002] Silicon-based organic-inorganic hybrid materials contain silicon (Si) as a skeletal element. Silicon (Si) has four bonds, and exhibits a variety of properties depending on the atoms and functional groups to which it is bonded. Oxygen (O) and carbon (C) bond strongly with Si. Oxygen forms Si-O-Si bonds, bridging Si atoms together to form polymers. On the other hand, carbon has the effect of suppressing the formation of Si-O-Si bonds. Such silicon-based organic-inorganic hybrid materials are used in optical and electronic materials due to their excellent heat resistance, chemical durability, transparency, and electrical insulation.

[0003] Polysilsesquioxanes have the general formula RSiO, which has one Si-C bond and three Si-O bonds per Si atom. ３／２ (R is an organic functional group). Polysilsesquioxanes exhibit random, ladder, or cage structures, and have excellent mechanical strength and chemical and thermal stability.

[0004] Polysilsesquioxanes can be obtained by hydrolysis and polycondensation of trifunctional silicon alkoxides. Various synthesis methods have been investigated to synthesize polysilsesquioxanes.

[0005] For example, Patent Document 1 proposes a method for producing a polysilsesquioxane liquid, which comprises hydrolyzing and polycondensing a mixture of a trifunctional silicon alkoxide, water, and an acid catalyst without using an organic solvent, and then removing the alcohol produced by the hydrolysis of the trifunctional silicon alkoxide. １ ) is in the range of 2000 to 20000, and the silicon-containing bond unit T ３ １ (where T ３ １The term "polymethylsilsesquioxane" refers to a polymethylsilsesquioxane containing 65 mol % or more of a silicon-containing bond unit in which all three oxygen atoms bonded to a silicon atom are bonded to other silicon atoms, and having a weight average molecular weight (Mw ２ ) is 600 to 2000, and Mw ２ and silicon-containing bond unit T ３ ２ and the formula (1): T ３ ２ ≧0.026×Mw ２ It is disclosed that an oligomer satisfying the +20 relationship can be produced by condensing it in the presence of an acidic catalyst or in the absence of a catalyst at a concentration of 5 to 40% by mass.

[0006] Japanese Patent Publication No. 2013-253223 Japanese Patent Publication No. 2018-178011

[0007] The properties of conventionally known polysilsesquioxanes are not yet fully satisfactory, and further improvements and developments are desired. Furthermore, when a liquid precursor of a polysilsesquioxane is thermally cured without using additives, curing catalysts, or the like, it is difficult to produce a thick cured product using conventional manufacturing methods, and it has been difficult to obtain a cured product having a thickness of 5 mm or more.

[0008] Therefore, an object of the present invention is to provide a method for producing a thick polysilsesquioxane-based cured product that has high hardness and excellent transparency without using additives, curing catalysts, etc., and to provide a polysilsesquioxane-based liquid precursor and cured product for obtaining such a cured product.

[0009] One aspect of the present invention is a polysilsesquioxane-based liquid precursor containing a copolymer of a trifunctional silicon alkoxide and a bifunctional silicon alkoxide, wherein the copolymer has a residual silanol group fraction f ＳｉＯＨ is 0.02 to 0.3.

[0010] Another aspect of the present invention is a cured product of a copolymer of a trifunctional silicon alkoxide and a bifunctional silicon alkoxide, wherein the residual silanol group fraction f ＳｉＯＨThe cured body relates to a cured body having a viscosity of 0.02 to 0.3.

[0011] Another aspect of the present invention relates to a method for producing a polysilsesquioxane-based liquid precursor, in which a trifunctional silicon alkoxide and a difunctional silicon alkoxide are aged during hydrolysis and polycondensation in an aqueous solution in the presence of an acid catalyst without using an organic solvent.

[0012] Another aspect of the present invention relates to a method for producing a cured product, which comprises heating and curing the polysilsesquioxane liquid precursor obtained by the above-mentioned method for producing a polysilsesquioxane liquid precursor.

[0013] The polysilsesquioxane liquid precursor obtained by the method for producing a polysilsesquioxane liquid precursor of the present invention can provide a cured product having high hardness and excellent transparency, and is therefore expected to be used in a variety of electronic applications, such as ultraviolet-transparent materials, transparent adhesives, sealing materials, insulating films, and scratch-resistant materials.

[0014] 1 is a photograph showing the appearance of the liquid precursor prepared in Test Example 1, where (a) is a photograph of the appearance of the liquid precursor in Example 1, (b) is a photograph of the appearance of the liquid precursor in Example 2, (c) is a photograph of the appearance of the liquid precursor in Example 3, (d) is a photograph of the appearance of the liquid precursor in Example 4, (e) is a photograph of the appearance of the liquid precursor in Example 5, (f) is a photograph of the appearance of the liquid precursor in Example 6, (g) is a photograph of the appearance of the liquid precursor in Example 7, (h) is a photograph of the appearance of the liquid precursor in Example 8, (i) is a photograph of the appearance of the liquid precursor in Example 9, and (j) is a photograph of the appearance of the liquid precursor in Example 10. FIG. Figure 3 is a graph showing the change in viscosity of the liquid precursors in Test Example 3, where (a) is a graph showing the change in viscosity of the liquid precursors in Examples 12 to 14 and (b) is a graph showing the change in viscosity of the liquid precursors in Examples 17 to 19. Figure 4 is a photograph showing the appearance of the liquid precursors prepared in Test Example 4, where (a) is a photograph of the appearance of the liquid precursors in Example 20, (b) is a photograph of the appearance of the liquid precursors in Example 21, (c) is a photograph of the appearance of the liquid precursors in Example 22, (d) is a photograph of the appearance of the liquid precursors in Example 23, and (e) is a photograph of the appearance of the liquid precursors in Example 24. Figure 5 is a photograph showing the appearance of the cured body prepared in Test Example 5, where (a) is a photograph of the appearance of the cured body in Example 25 and (b) is a photograph of the appearance of the cured body in Example 26. Figure 6 is a photograph showing the appearance of the cured body in Example 27 prepared in Test Example 5, where (a) is a top view and (b) is a side view. Fig. 7 is a photograph showing the appearance of the cured body produced in Test Example 5, where (a) is a photograph showing the appearance of the cured body of Example 28, (b) is a photograph showing the appearance of the cured body of Example 29, (c) is a photograph showing the appearance of the cured body of Example 30, and (d) is a photograph showing the appearance of the hardened body of Example 31. Fig. 8 is a graph showing the stress-strain curve recorded in the uniaxial loading / unloading test of Test Example 6.

[0015] The present invention will be described below, but the present invention is not limited to the examples in the following description.

[0016] (Polysilsesquioxane Liquid Precursor) The polysilsesquioxane liquid precursor according to the present invention comprises a copolymer of a trifunctional silicon alkoxide and a bifunctional silicon alkoxide, and the copolymer has a residual silanol group fraction f ＳｉＯＨThe polysilsesquioxane liquid precursor of the present invention has a viscosity of 0.02 to 0.3. A polysilsesquioxane liquid precursor having such characteristics can produce a cured product that has high hardness while maintaining elasticity. Furthermore, the polysilsesquioxane liquid precursor of the present invention can maintain a liquid state for a long period of time without gelling during storage at room temperature.

[0017] Trifunctional silicon alkoxides are compounds in which three of the four bonds of silicon (Si) are bonded to alkoxy groups.

[0018] Examples of trifunctional silicon alkoxides include trimethoxysilane, methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, phenyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, vinyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, triethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, propyltriethoxysilane, phenyltriethoxysilane, 3-mercaptopropyltriethoxysilane, vinyltriethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-aminopropyltriethoxysilane, etc. The trifunctional silicon alkoxide may contain one of these alone or two or more. Among these, the trifunctional silicon alkoxide is preferably at least one selected from methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, and ethyltriethoxysilane, more preferably methyltrimethoxysilane, and further preferably contains 80 mol% or more of methyltrimethoxysilane relative to the total mol% of the trifunctional silicon alkoxide, and particularly preferably contains 95 mol% or more of methyltrimethoxysilane.

[0019] A bifunctional silicon alkoxide is a compound in which two of the four bonds of silicon are bonded to alkoxy groups.

[0020] Examples of bifunctional silicon alkoxides include dimethoxysilane, dimethoxymethylsilane, dimethoxydimethylsilane, dimethoxyethylsilane, dimethoxydiethylsilane, dimethoxyethylmethylsilane, dimethoxyphenylsilane, dimethoxymethylphenylsilane, dimethoxydiphenylsilane, dimethoxyvinylsilane, dimethoxymethylvinylsilane, dimethoxydivinylsilane, diethoxysilane, diethoxymethylsilane, diethoxydimethylsilane, diethoxyethylsilane, diethoxydiethylsilane, diethoxyethylmethylsilane, diethoxyphenylsilane, diethoxymethylphenylsilane, diethoxydiphenylsilane, diethoxyvinylsilane, diethoxymethylvinylsilane, diethoxydivinylsilane, etc. The bifunctional silicon alkoxide may contain one of these alone or two or more. Among these, the bifunctional silicon alkoxide is preferably at least one selected from dimethoxydimethylsilane, dimethoxyethylmethylsilane, dimethoxydiethylsilane, diethoxydimethylsilane, diethoxyethylmethylsilane, and diethoxydiethylsilane, with dimethoxydimethylsilane being more preferred, and it is even more preferred that the bifunctional silicon alkoxide contains 80 mol% or more of dimethoxydimethylsilane, and particularly preferably 95 mol% or more of dimethoxydimethylsilane, based on the total mol% of the bifunctional silicon alkoxide.

[0021] In this specification, the structural unit derived from the trifunctional silicon alkoxide in the copolymer is referred to as a "T-form," and the T-form is classified into three types depending on the number of bridging oxygen atoms bonded to other silicon atoms. When all of the three oxygen atoms are bonded to other silicon atoms, i.e., when there are three bridging oxygen atoms, the structural unit is called a "T-form." ３ When two of the three oxygen atoms are bonded to other silicon atoms, that is, when there are two bridging oxygen atoms, the structural unit is called a "T ２ When one of the three oxygen atoms is bonded to another silicon atom, that is, when there is one bridging oxygen, the structural unit is called a "T １Furthermore, the structural unit derived from bifunctional silicon alkoxide in the copolymer is called "D-form", and D-form is classified into two types depending on the number of bridging oxygen atoms bonded to other silicon atoms. When all of the two oxygen atoms are bonded to other silicon atoms, i.e., when there are two bridging oxygen atoms, the structural unit is called "D-form". ２ When one of the two oxygen atoms is bonded to another silicon atom, that is, when there is one bridging oxygen, the structural unit is called a "D １ It's called "body."

[0022] In the polysilsesquioxane liquid precursor of this embodiment, the proportion of crosslinking oxygen in the copolymer can be calculated by the following formula (1): proportion of crosslinking oxygen = <m> / <m> ｍａｘ ...(1) In formula (1), <m> ｍａｘ is a structural unit derived from a trifunctional silicon alkoxide in which all structural units have three bridging oxygen atoms. ３ D is a structural unit derived from a bifunctional silicon alkoxide, and all structural units in the structural unit derived from a bifunctional silicon alkoxide have two bridging oxygen atoms. ２ <m> is the maximum average number of crosslinking oxygen atoms in a complete copolymer when the copolymer is a unit structure, and <m> is the average number of crosslinking oxygen atoms actually contained in the copolymer, as expressed by the following formula (2): <m>=(f Ｔ１ ×n Ｔ１ ) + (f Ｔ２ ×n Ｔ２ ) + (f Ｔ３ ×n Ｔ３ ) + (f Ｄ１ ×n Ｄ１ ) + (f Ｄ２ ×n Ｄ２ )...(2) In formula (2), f Ｔ１ is a structural unit derived from a trifunctional silicon alkoxide having one bridging oxygen atom, T １ is the abundance ratio of the structural unit, n Ｔ１ Is T １ f represents the number of bridging oxygen atoms in the hydroxyl group of the hydroxyl group, which is 1; Ｔ２ is a structural unit derived from a trifunctional silicon alkoxide having two bridging oxygen atoms, T ２ is the abundance ratio of the structural unit, n Ｔ２ Is T ２f represents the number of bridging oxygen atoms in the bridging unit, which is 2; Ｔ３ is a structural unit derived from a trifunctional silicon alkoxide having three bridging oxygen atoms, T ３ is the abundance ratio of the structural unit, n Ｔ３ Is T ３ f represents the number of bridging oxygen atoms in the bridging unit, which is 3; Ｄ１ is a structural unit derived from a bifunctional silicon alkoxide having one bridging oxygen atom. １ is the abundance ratio of the structural unit, n Ｄ１ is D １ f represents the number of bridging oxygen atoms in the hydroxyl group of the hydroxyl group, which is 1; Ｄ２ is a structural unit derived from a bifunctional silicon alkoxide having two bridging oxygen atoms, D ２ is the abundance ratio of the structural unit, n Ｄ２ is D ２ f represents the number of bridging oxygen atoms in the bridging unit, which is 2; Ｔ１ , f Ｔ２ , f Ｔ３ , f Ｄ１ and f Ｄ２ There is the following relationship between f Ｔ１ +f Ｔ２ +f Ｔ３ +f Ｄ１ +f Ｄ２ =1

[0023] In addition, T １ Abundance ratio f of body structural units Ｔ１ , T ２ Abundance ratio f of body structural units Ｔ２ , T ３ Abundance ratio f of body structural units Ｔ３ , D １ Body structural unit abundance ratio f Ｄ１ and D ２ Abundance ratio f of body structural units Ｄ２ teeth, ２９ The ratio can be determined by measuring the Si NMR spectrum and calculating the respective ratios from the results.

[0024] The polysilsesquioxane liquid precursor of this embodiment has a residual silanol group fraction f ＳｉＯＨ is 0.02 to 0.3. Residual silanol group fraction f ＳｉＯＨis the ratio of the total number of SiOH groups present in the copolymer of trifunctional silicon and difunctional silicon to the total number of Si atoms and <m> ｍａｘ The residual silanol group fraction f is the ratio of the product of ＳｉＯＨ If the residual silanol group fraction f is 0.02 or more, the curing due to the polycondensation reaction during thermal curing will proceed more easily, resulting in a cured product with high hardness, and if it is 0.3 or less, the stability of the liquid precursor can be maintained. ＳｉＯＨ is preferably 0.03 or more, more preferably 0.05 or more, even more preferably 0.06 or more, particularly preferably 0.1 or more, and is more preferably 0.25 or less, even more preferably 0.2 or less.

[0025] Residual silanol group fraction f ＳｉＯＨ teeth, １ The residual methoxy group fraction f ＳｉＯＭｅ is determined and is calculated by the following formula (3): ＳｉＯＨ =1-(<m> / <m> ｍａｘ +f ＳｉＯＭｅ ) (3) In formula (3), <m> is the average number of crosslinking oxygen atoms actually contained in the copolymer, and <m> ｍａｘ is the maximum average number of crosslinking oxygen atoms in the complete copolymer, and <m> / <m> ｍａｘ is the proportion of cross-linking oxygen in the copolymer.

[0026] The polysilsesquioxane liquid precursor of this embodiment has a viscosity of 1×10 at 40° C. ６ It is preferable that the viscosity is 1×10 mPa·s or less. ６ When the viscosity is 1×10 mPa·s or less, the operability is excellent, defoaming and molding of the precursor are easy, and loss due to adhesion to the container can be suppressed. ５ The lower the viscosity, the better, and therefore there is no particular lower limit.

[0027] The viscosity of the liquid precursor is measured at 40° C. using, for example, a commercially available viscometer (for example, an EMS viscometer "EMS-1000S" manufactured by Kyoto Electronics Manufacturing Co., Ltd.).

[0028] The polysilsesquioxane liquid precursor of this embodiment has a molecular weight of 0.5 × 10 ３ ~50 x 10 ３ g / mol －１ The mass average molar mass Mm is preferably 0.8 × 10 ３ g / mol －１ More preferably, it is 1.0 × 10 ３ g / mol －１ More preferably, 20×10 ３ g / mol －１ More preferably, it is 15×10 ３ g / mol －１ More preferably, 10×10 ３ g / mol －１ The following are particularly preferred:

[0029] The polysilsesquioxane liquid precursor is 0.5 × 10 ３ ~5.0 x 10 ３ g / mol －１ The number average molar mass Mn is preferably 0.7×10 ３ g / mol －１ More preferably, it is 0.8×10 or more. ３ g / mol －１ More preferably, 4.0 × 10 ３ g / mol －１ More preferably, it is 3.0 x 10 or less. ３ g / mol －１ The following is even more preferred:

[0030] The mass-average molar mass Mm and the number-average molar mass Mn can be determined by known measurement methods such as gel permeation chromatography.

[0031] (Cured Product) The cured product of the present invention is a cured product of a copolymer of a trifunctional silicon alkoxide and a bifunctional silicon alkoxide, and the residual silanol group fraction f ＳｉＯＨThe cured product according to the present invention is a cured product of a polysilsesquioxane liquid precursor obtained by curing the polysilsesquioxane liquid precursor described above.

[0032] The trifunctional silicon alkoxide and difunctional silicon alkoxide used in the cured product are as described above, and the preferred ones are also as described above. The properties of the polysilsesquioxane liquid precursor are also as described above.

[0033] The pencil hardness of the cured product of this embodiment is preferably HB or higher. When the pencil hardness is HB or higher, the cured product is hard and has excellent hardness. The pencil hardness is more preferably H or higher, even more preferably 2H or higher, particularly preferably 4H or higher, and most preferably 6H or higher.

[0034] The pencil hardness is measured by a manual scratching method in accordance with the pencil scratch test specified in the former JIS K5400.

[0035] Furthermore, the Vickers hardness of the cured product measured in accordance with JIS R 1610-2003 is preferably 1 HV or more. A Vickers hardness of 1 HV or more indicates that the product has high hardness while retaining elasticity. A Vickers hardness of 2 HV or more is more preferable, and a Vickers hardness of 4 HV or more is even more preferable.

[0036] The hardened body of this embodiment exhibits remarkable elastic recovery behavior as shown in the uniaxial loading / unloading test in the Examples described later, and therefore, depending on the hardened body, no deformation mark is formed in the Vickers hardness test, and the Vickers hardness cannot be measured. If a deformation mark is formed by a Vickers indenter, it can be said that the hardened body has sufficient hardness, but if the Vickers hardness cannot be measured, the hardness may be measured by a pencil hardness test.

[0037] Furthermore, the cured product of this embodiment has high transparency. The cured product preferably has an ultraviolet absorption edge wavelength of 250 nm or less. When the ultraviolet absorption edge wavelength is 250 nm or less, the cured product exhibits excellent visible-ultraviolet transmittance, and therefore high ultraviolet resistance can be expected. The ultraviolet absorption edge wavelength is more preferably 220 nm or less, even more preferably 210 nm or less, and particularly preferably 200 nm or less.

[0038] The ultraviolet absorption edge wavelength is a value obtained as the intersection of the approximate straight line of the spectrum in the ultraviolet absorption edge region of the light absorption spectrum measured using a spectrophotometer (U-4100 manufactured by Hitachi High-Technologies Corporation) and the approximate straight line of the baseline spectrum in the transparent region on the long wavelength side.

[0039] The cured product of this embodiment can have a thickness of 4.8 mm or more, preferably 5 mm or more, more preferably 8 mm or more, and even more preferably 10 mm or more. In particular, when the thickness of the cured product is 10 mm or more, it can be used as a bulk material or applied to large components.

[0040] (Production Method) The polysilsesquioxane liquid precursor can be obtained by subjecting a trifunctional silicon alkoxide and a difunctional silicon alkoxide to hydrolysis and polycondensation in an aqueous solution in the presence of an acid catalyst without using an organic solvent, followed by aging.

[0041] The trifunctional silicon alkoxides and difunctional silicon alkoxides to which the production method of the present invention can be applied are as described above, and the preferred ones are also as described above.

[0042] The trifunctional silicon alkoxide is preferably used in the range of 0.5 to 0.99 mol per mol of total silicon alkoxide. When the amount of trifunctional silicon alkoxide used is within this range, the resulting cured product has increased hardness while retaining elasticity. The amount of trifunctional silicon alkoxide used is preferably 0.6 mol or more, more preferably 0.7 mol or more, and more preferably 0.95 mol or less, more preferably 0.9 mol or less, per mol of total silicon alkoxide.

[0043] The bifunctional silicon alkoxide is preferably used in the range of 0.01 to 0.5 mol per mol of total silicon alkoxide. When the amount of bifunctional silicon alkoxide used is within this range, the resulting cured product has increased hardness while retaining elasticity. The amount of bifunctional silicon alkoxide used is preferably 0.05 mol or more, more preferably 0.1 mol or more, and more preferably 0.4 mol or less, even more preferably 0.3 mol or less, per mol of total silicon alkoxide.

[0044] As the acid catalyst, nitric acid, hydrochloric acid, sulfuric acid, acetic acid, formic acid, etc., which are used in conventional sol-gel methods using organic solvents, can be preferably used, and hydrochloric acid is preferred from the viewpoints of availability, high purity, volatility, and ultraviolet transparency. Phosphoric acid can also be used as the acid catalyst, but it is preferable not to use phosphoric acid because it is highly non-volatile and tends to remain in the copolymer.

[0045] The amount of acid catalyst used varies depending on the type and composition of the silicon alkoxide used, the type of acid, etc., but it is preferable to mix the acid catalyst in an amount greater than 0 mol and not more than 0.01 mol per 1 mol of the total of the trifunctional silicon alkoxide and the difunctional silicon alkoxide. When the amount of acid catalyst is 0.01 mol or less per 1 mol of the total of all silicon alkoxides, a stable liquid precursor can be produced and residual acid in the liquid precursor and cured product can be reduced. For example, when methyltrimethoxysilane is used as the trifunctional silicon alkoxide and dimethoxydimethylsilane is used as the difunctional silicon alkoxide, it is preferable to use an acid catalyst in the range of 0.00002 to 0.002 mol per 1 mol of the total of all silicon alkoxides, and a range of 0.00002 to 0.001 mol is more preferable.

[0046] In this production method, the reaction proceeds in an aqueous solution without using an organic solvent, such as purified water, distilled water, or ion-exchanged water.

[0047] The amount of water used varies depending on the type and structure of the silicon alkoxide used, the type of acid, etc., but it is preferable to mix 1.5 to 50 mol of water per 1 mol of the total of the trifunctional silicon alkoxide and the difunctional silicon alkoxide. Using 1.5 mol or more of water can suppress an increase in viscosity of the reaction solution, while using 50 mol or less can suppress the amount of aqueous methanol solution produced as a by-product. For example, when methyltrimethoxysilane is used as the trifunctional silicon alkoxide and dimethoxydimethylsilane is used as the difunctional silicon alkoxide, it is preferable to use 5 to 50 mol of water per 1 mol of the total of all silicon alkoxides, more preferably 8 to 40 mol, and even more preferably 10 to 30 mol.

[0048] In the method for producing a polysilsesquioxane liquid precursor of this embodiment, a trifunctional silicon alkoxide, a difunctional silicon alkoxide, water, and an acid catalyst are mixed together to carry out hydrolysis and polycondensation, during which the mixture is aged by maintaining the mixture at a temperature of 20 to 100°C for approximately 1 to 48 hours. By carrying out the reaction within this temperature range, an increase in the viscosity of the resulting liquid precursor can be suppressed. Furthermore, by carrying out the reaction for a time within this range, the reaction proceeds sufficiently, and the residue of unreacted alkoxy groups can be suppressed.

[0049] It is necessary to remove excess water and alcohol produced during hydrolysis. Methods such as drying and liquid-liquid extraction are used to remove water and alcohol. When drying, it is preferable to dry at 20 to 100°C for 1 to 48 hours. Vacuum drying is preferred during drying, as it can reduce the amount of residual water and alcohol. In particular, in the production method of the present invention, when silicon methoxide is used as the silicon source, hydrolysis and polycondensation cause liquid-liquid phase separation into a polysilsesquioxane precursor-rich phase and a methanol and water-rich phase, making it possible to perform liquid-liquid extraction and shorten the drying time for the former.

[0050] The resulting polysilsesquioxane liquid precursor can be heated and cured to obtain a cured product.

[0051] The conditions for the heat treatment are not particularly limited, but are preferably carried out at a temperature of 100 to 300°C for about 1 hour to 1 week in air or an inert gas atmosphere such as nitrogen, or in a vacuum, and more preferably in an inert gas atmosphere such as nitrogen, or in a vacuum to improve transparency. The heat treatment may be carried out at a constant temperature, or may be carried out in multiple stages at different temperatures and / or times.

[0052] The polysilsesquioxane liquid precursor obtained in this embodiment is liquid and does not gel during storage at room temperature, making it easy to handle, and the cured product obtained from the liquid precursor has high hardness while retaining elasticity and exhibits excellent visible-ultraviolet transmittance. Furthermore, the cured product of this embodiment can be formed to a certain thickness, making it easy to obtain a bulk product.

[0053] The cured product of the present invention is suitable for use in electric and electronic parts, such as an ultraviolet-transparent material, a transparent adhesive for areas where alkali is intolerant, an ultraviolet LED sealing material, an electrical insulating film, a scratch-resistant coating, and an impact-resistant and scratch-resistant cover material.

[0054] As explained above, the present specification discloses the following: <1> A polysilsesquioxane-based liquid precursor containing a copolymer of a trifunctional silicon alkoxide and a difunctional silicon alkoxide, wherein the copolymer has a residual silanol group fraction f ＳｉＯＨ <2> A polysilsesquioxane-based liquid precursor having a viscosity of 1×10 at 40°C. ６<1> The polysilsesquioxane liquid precursor according to <1> above, having a viscosity of 1000 psi or less. <3> The polysilsesquioxane liquid precursor according to <1> or <2> above, wherein the trifunctional silicon alkoxide contains 80 mol % or more of methyltrimethoxysilane based on the total mol % of the trifunctional silicon alkoxide. <4> The polysilsesquioxane liquid precursor according to any one of <1> to <3> above, wherein the bifunctional silicon alkoxide contains 80 mol % or more of dimethoxydimethylsilane based on the total mol % of the bifunctional silicon alkoxide. <5> A cured product of a copolymer of a trifunctional silicon alkoxide and a bifunctional silicon alkoxide, wherein the copolymer has a residual silanol group fraction f ＳｉＯＨ A cured product having a molecular weight of 0.02 to 0.3. <6> The cured product according to <5> above, wherein the trifunctional silicon alkoxide contains 80 mol % or more of methyltrimethoxysilane, based on the total mol % of the trifunctional silicon alkoxide. <7> The cured product according to <5> or <6> above, wherein the bifunctional silicon alkoxide contains 80 mol % or more of dimethoxydimethylsilane, based on the total mol % of the bifunctional silicon alkoxide. <8> The cured product according to any one of <5> to <7> above, having a pencil hardness of HB or more. <9> The cured product according to any one of <5> to <8> above, having a Vickers hardness of 1 HV or more. <10> The cured product according to any one of <5> to <9> above, having an ultraviolet absorption edge wavelength of 250 nm or less. <11> The cured product according to any one of <5> to <10> above, having a thickness of 4.8 mm or more. <12> The cured product according to any one of <5> to <11>, which is used for electric and electronic parts.

[0055] <13> A method for producing a polysilsesquioxane-based liquid precursor, comprising aging a trifunctional silicon alkoxide and a difunctional silicon alkoxide during hydrolysis and polycondensation in an aqueous solution in the presence of an acid catalyst without using an organic solvent. <14> A method for producing a polysilsesquioxane-based liquid precursor according to <13> above, wherein 0.5 to 0.99 mol of the trifunctional silicon alkoxide is used per mol of the total silicon alkoxides. <15> A method for producing a polysilsesquioxane-based liquid precursor according to <13> or <14> above, wherein more than 0 mol and 0.01 mol or less of the acid catalyst is used per mol of the total silicon alkoxides. <16> A method for producing a polysilsesquioxane-based liquid precursor according to any one of <13> to <15> above, wherein 1.5 to 50 mol of water is used per mol of the total silicon alkoxides. <17> A method for producing the polysilsesquioxane liquid precursor according to any one of <13> to <16>, wherein the trifunctional silicon alkoxide contains 80 mol % or more of methyltrimethoxysilane relative to the total mol % of the trifunctional silicon alkoxide. <18> A method for producing the polysilsesquioxane liquid precursor according to any one of <13> to <17>, wherein the bifunctional silicon alkoxide contains 80 mol % or more of dimethoxydimethylsilane relative to the total mol % of the bifunctional silicon alkoxide. <19> A method for producing the polysilsesquioxane liquid precursor according to any one of <13> to <18>, comprising removing alcohol produced by the hydrolysis reaction. <20> A method for producing a cured product, comprising heating and curing the polysilsesquioxane liquid precursor obtained by the method for producing a polysilsesquioxane liquid precursor according to any one of <13> to <19>.

[0056] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these. Examples 1 to 27, 32, and 36 to 39 are working examples, and Examples 28 to 31, 33 to 35, and 40 are comparative examples.

[0057] (Test Example 1) (Example 1) Methyltrimethoxysilane, a trifunctional silicon alkoxide, and dimethoxydimethylsilane, a bifunctional silicon alkoxide, were mixed in a molar ratio of methyltrimethoxysilane:dimethoxydimethylsilane = 0.5:0.5 so that the total molar ratio was 1, for a total of 100 mmol. Dilute hydrochloric acid consisting of 0.2 mmol of hydrogen chloride (HCl / silicon ratio 0.002) and 250 mmol of water (water / silicon ratio 2.5) was added thereto, and the mixture was stirred at 20 ° C. for 3 hours in a sealed container. The mixture was then allowed to stand at 80 ° C. for 24 hours to mature, allowing hydrolysis and polycondensation to proceed. After aging, the mixture was cooled to room temperature, the container was opened, and the upper layer solution, which had undergone liquid-liquid phase separation, was extracted and removed with a Pasteur pipette. The lower layer solution was dried under vacuum at 60 ° C. for 24 hours, yielding a colorless, transparent liquid precursor.

[0058] Examples 2 to 10 A colorless, transparent liquid precursor was obtained in the same manner as in Example 1, except that the amounts of methyltrimethoxysilane, dimethoxydimethylsilane, and water used were changed as shown in Table 1.

[0059] <Viscosity Measurement> Using an EMS viscometer ("EMS-1000S" manufactured by Kyoto Electronics Manufacturing Co., Ltd.), the viscosity of the liquid precursor was measured at 30° C. and 40° C. The results are shown in Table 1.

[0060] <Measurement of Molar Mass> The mass-average molar mass (weight-average molecular weight) Mm and number-average molar mass (number-average molecular weight) Mn of the liquid precursor were determined by gel permeation chromatography. Measurements were performed using a Shimadzu Corporation "RID-10A" detector, a Showa Denko K.K. "Shodex KF-804L" column, and tetrahydrofuran as the solvent, at a flow rate of 1.0 ml / min and an injection volume of 20 μl. The mass-average molar mass and number-average molar mass were calculated from a calibration curve using polystyrene of known molar mass as the standard substance. The results are shown in Table 1.

[0061] <NMR measurement> Liquid precursor １ H and ２９ Si NMR spectra were measured using a JEOL "JMN-ECS300" instrument using CDCl as the solvent. ３ was measured using１ H nucleus is 300MHz, ２９ The Si nuclei were measured at 59.6 MHz. ２９ The abundance ratio of T-isomer and D-isomer (f Ｔ１ , f Ｔ２ , f Ｔ３ , f Ｄ１ , f Ｄ２ ) was determined, and the average number of bridging oxygen atoms <m> was calculated using the following formula (2): <m> = (f Ｔ１ ×n Ｔ１ ) + (f Ｔ２ ×n Ｔ２ ) + (f Ｔ３ ×n Ｔ３ ) + (f Ｄ１ ×n Ｄ１ ) + (f Ｄ２ ×n Ｄ２ )...(2) In formula (2), f Ｔ１ is a structural unit derived from a trifunctional silicon alkoxide having one bridging oxygen atom, T １ is the abundance ratio of the structural unit, n Ｔ１ Is T １ f represents the number of bridging oxygen atoms in the hydroxyl group of the hydroxyl group, which is 1; Ｔ２ is a structural unit derived from a trifunctional silicon alkoxide having two bridging oxygen atoms, T ２ is the abundance ratio of the structural unit, n Ｔ２ Is T ２ f represents the number of bridging oxygen atoms in the bridging unit, which is 2; Ｔ３ is a structural unit derived from a trifunctional silicon alkoxide having three bridging oxygen atoms, T ３ is the abundance ratio of the structural unit, n Ｔ３ Is T ３ f represents the number of bridging oxygen atoms in the bridging unit, which is 3; Ｄ１ is a structural unit derived from a bifunctional silicon alkoxide having one bridging oxygen atom. １ is the abundance ratio of the structural unit, n Ｄ１ is D １ f represents the number of bridging oxygen atoms in the hydroxyl group of the hydroxyl group, which is 1; Ｄ２ is a structural unit derived from a bifunctional silicon alkoxide having two bridging oxygen atoms, D ２ is the abundance ratio of the structural unit, n Ｄ２ is D ２f represents the number of bridging oxygen atoms in the bridging unit, which is 2; Ｔ１ +f Ｔ２ +f Ｔ３ +f Ｄ１ +f Ｄ２ =1.

[0062] The proportion of cross-linking oxygen was calculated using the following formula (1): proportion of cross-linking oxygen = <m> / <m> ｍａｘ ...(1) In formula (1), <m> ｍａｘ is a structural unit derived from a trifunctional silicon alkoxide in which all structural units have three bridging oxygen atoms. ３ D is a structural unit derived from a bifunctional silicon alkoxide, and all structural units in the structural unit derived from a bifunctional silicon alkoxide have two bridging oxygen atoms. ２ This is the maximum average number of crosslinking oxygen atoms in a complete copolymer when the copolymer is a structural unit.

[0063] Next, １ The residual methoxy group fraction f ＳｉＯＭｅ is determined, and the residual silanol group fraction f is calculated using the following formula (3): ＳｉＯＨ The residual silanol group fraction f ＳｉＯＨ =1-(<m> / <m> ｍａｘ +f ＳｉＯＭｅ ) ... (3)

[0064] The results are shown in Table 1. In Examples 2, 4, and 8 to 10, the liquid precursor structure was such that the maximum average number of crosslinking oxygen atoms in the complete copolymer, <m> ｍａｘ In Table 1, only the mass-average molar mass Mm and the number-average molar mass Mn were measured in Example 4, and no physical property measurements were performed in Example 2. Ｔ１ , f Ｔ２ , f Ｔ３ , f Ｄ１ and f Ｄ２ ) and the sum of <m> / <m> in Example 7 ｍａｘ , f ＳｉＯＭｅ and f ＳｉＯＨ The reason why the sum of these is not 1 is due to rounding errors.

[0065]

[0066] The appearances of the liquid precursors of Examples 1 to 10 are shown in Figure 1. In Figure 1, (a) is the liquid precursor of Example 1, (b) is the liquid precursor of Example 2, (c) is the liquid precursor of Example 3, (d) is the liquid precursor of Example 4, (e) is the liquid precursor of Example 5, (f) is the liquid precursor of Example 6, (g) is the liquid precursor of Example 7, (h) is the liquid precursor of Example 8, (i) is the liquid precursor of Example 9, and (j) is the liquid precursor of Example 10. As shown in Figures 1(a) to (j), all of the liquid precursors of Examples 1 to 10 were obtained in liquid form.

[0067] (Test Example 2) (Example 11) Methyltrimethoxysilane, a trifunctional silicon alkoxide, and dimethoxydimethylsilane, a bifunctional silicon alkoxide, were mixed in a molar ratio of methyltrimethoxysilane:dimethoxydimethylsilane = 0.8:0.2 so that the total molar ratio was 1, for a total of 100 mmol. Dilute hydrochloric acid consisting of 0.02 mmol of hydrogen chloride (HCl / silicon ratio 0.0002) and 500 mmol of water (water / silicon ratio 5) was added thereto, and the mixture was stirred at 20 ° C. for 3 hours in a sealed container. The mixture was then allowed to stand at 80 ° C. for 24 hours to mature, allowing hydrolysis and polycondensation to proceed. After aging, the mixture was cooled to room temperature, the container was opened, and the upper layer solution, which had undergone liquid-liquid phase separation, was extracted and removed with a Pasteur pipette. The lower layer solution was dried under vacuum at 60 ° C. for 24 hours, yielding a colorless, transparent liquid precursor.

[0068] Examples 12 to 19 A colorless, transparent liquid precursor was obtained in the same manner as in Example 11, except that the amounts of methyltrimethoxysilane, dimethoxydimethylsilane, water, and hydrogen chloride used were changed as shown in Table 2.

[0069] <Viscosity Measurement> The viscosity of the liquid precursor at 40° C. was measured in the same manner as in Test Example 1. The results are shown in Table 2.

[0070] <Measurement of Molar Mass> The mass-average molar mass and number-average molar mass of the liquid precursor were calculated in the same manner as in Test Example 1. The results are shown in Table 2.

[0071] <NMR Measurement> In the same manner as in Test Example 1, the abundance ratios of the T-isomer and the D-isomer in the liquid precursor (f Ｔ１ , f Ｔ２ , f Ｔ３ , f Ｄ１ , f Ｄ２ ), average number of crosslinking oxygen atoms <m>, maximum average number of crosslinking oxygen atoms in a complete copolymer <m>ｍａｘ , the ratio of bridging oxygen <m> / <m> ｍａｘ , residual methoxy group fraction f ＳｉＯＭｅ , residual silanol group fraction f ＳｉＯＨ The results are shown in Table 2. In Table 2, the abundance ratio (f Ｔ１ , f Ｔ２ , f Ｔ３ , f Ｄ１ and f Ｄ２ ) and the sum of <m> / <m> in Example 14 ｍａｘ , f ＳｉＯＭｅ and f ＳｉＯＨ The reason why the sum of these is not 1 is due to rounding errors.

[0072]

[0073] The appearances of the liquid precursors of Examples 11 to 19 are shown in Figure 2. In Figure 2, (a) is the liquid precursor of Example 11, (b) is the liquid precursor of Example 12, (c) is the liquid precursor of Example 13, (d) is the liquid precursor of Example 14, (e) is the liquid precursor of Example 15, (f) is the liquid precursor of Example 16, (g) is the liquid precursor of Example 17, (h) is the liquid precursor of Example 18, and (i) is the liquid precursor of Example 19. As shown in Figures 2(a) to (i), all of the liquid precursors of Examples 11 to 19 were obtained in liquid form.

[0074] (Test Example 3) The change in viscosity over time was confirmed for the liquid precursors of Examples 12 to 14 and Examples 16 to 19 prepared in Test Example 2. The viscosity was measured using an EMS viscometer "EMS-1000S" manufactured by Kyoto Electronics Manufacturing Co., Ltd., measuring the viscosity at 40°C of the liquid precursor immediately after preparation and the liquid precursor after being stored in a sealed container at room temperature (approximately 20 to 30°C) for up to 60 days, and the viscosity increase rate (%) was calculated using the following formula: Viscosity increase rate (%) = (viscosity after storage at room temperature for 60 days / viscosity immediately after preparation - 1) × 100

[0075] The results of the viscosity increase rate are shown in Table 3. The liquid precursors of Examples 12, 14, and 16 did not increase in viscosity to 1×10 within 60 days. ６ Since the viscosity exceeded 100 mPa s, it was not possible to measure the rate of viscosity increase. The changes in the viscosity of the liquid precursors for Examples 12 to 14 and Examples 17 to 19 are shown in Figure 3. In Figure 3, (a) shows the results for Examples 12 to 14, and (b) shows the results for Examples 17 to 19.

[0076]

[0077] 3, the liquid precursors of Examples 12 to 14 and Examples 16 to 19 showed a gradual increase in viscosity and were excellent in stability over time. In particular, the liquid precursors of Examples 13 and 17 to 19 showed a small increase in viscosity even after 60 days, indicating that the viscosity was stable over a long period of time.

[0078] (Test Example 4) (Example 20) Methyltrimethoxysilane, a trifunctional silicon alkoxide, and dimethoxydimethylsilane, a bifunctional silicon alkoxide, were mixed in a molar ratio of methyltrimethoxysilane:dimethoxydimethylsilane = 0.8:0.2 so that the total molar ratio was 1, for a total of 100 mmol. Dilute hydrochloric acid consisting of 0.2 mmol of hydrogen chloride (HCl / silicon ratio 0.002) and 2000 mmol of water (water / silicon ratio 20) was added thereto, and the mixture was stirred at 20 ° C. for 3 hours in a sealed container. The mixture was then allowed to stand at 80 ° C. for 24 hours to mature, allowing hydrolysis and polycondensation to proceed. After aging, the mixture was cooled to room temperature, the container was opened, and the upper layer solution, which had undergone liquid-liquid phase separation, was extracted and removed with a Pasteur pipette. The lower layer solution was dried under vacuum at 60 ° C. for 24 hours, yielding a colorless, transparent liquid precursor.

[0079] (Examples 21 to 24) Transparent, colorless liquid precursors were obtained in the same manner as in Example 20, except that the amounts of methyltrimethoxysilane, dimethoxydimethylsilane, water, and hydrogen chloride used were changed as shown in Table 4. The liquid precursor in Example 22 was the same as that in Example 13.

[0080] <Viscosity Measurement> The viscosity of the liquid precursor at 40° C. was measured in the same manner as in Test Example 1. The results are shown in Table 4.

[0081] <Measurement of Molar Mass> The mass-average molar mass and number-average molar mass of the liquid precursor were calculated in the same manner as in Test Example 1. The results are shown in Table 4.

[0082]

[0083] The appearances of the liquid precursors of Examples 20 to 24 are shown in Figure 4. In Figure 4, (a) is the liquid precursor of Example 20, (b) is the liquid precursor of Example 21, (c) is the liquid precursor of Example 22, (d) is the liquid precursor of Example 23, and (e) is the liquid precursor of Example 24. As shown in Figures 4(a) to (e), the liquid precursors of Examples 20 to 24 were all obtained in liquid form.

[0084] Test Example 5 Example 25 The liquid precursor of Example 13 was heated in a nitrogen atmosphere at 200°C for 24 hours to obtain a cured body having a thickness of 4.9 mm. The appearance of the obtained cured body (photograph viewed from above) is shown in Figure 5(a).

[0085] Example 26 The liquid precursor of Example 13 was heated in a nitrogen atmosphere at 200°C for 12 hours and then at 250°C for 24 hours to obtain a cured product having a thickness of 5.4 mm. The appearance of the obtained cured product (photograph taken from the top) is shown in Figure 5(b).

[0086] Example 27: A colorless, transparent liquid precursor was obtained by the same procedure as in Example 13, except that the total amount of the trifunctional silicon alkoxide methyltrimethoxysilane and the difunctional silicon alkoxide dimethoxydimethylsilane was 300 mmol. The fluidity of the liquid precursor was visually comparable to that of Example 13, and therefore the viscosity at 40°C was determined to be comparable to that of Example 13. The resulting liquid precursor was placed in a mold with a diameter of 30 mm and a depth of 20 mm and heated in a nitrogen atmosphere at 120°C for 6 hours, 180°C for 6 hours, and then 250°C for 24 hours to obtain a cured product with a thickness of 15.6 mm. A top view of the resulting cured product is shown in Figure 6(a), and a side view is shown in Figure 6(b).

[0087] (Example 28) Dilute hydrochloric acid consisting of 0.02 mmol of hydrogen chloride (HCl / silicon ratio 0.0002) and 2000 mmol of water (water / silicon ratio 20) was added to 100 mmol of trifunctional silicon alkoxide ethyltrimethoxysilane, and the mixture was stirred in a sealed container at 20°C for 3 hours. The mixture was then allowed to stand at 80°C for 24 hours to mature, allowing hydrolysis and polycondensation to proceed. After aging, the mixture was cooled to room temperature, the container was opened, and the upper layer solution, which had undergone liquid-liquid phase separation, was extracted and removed with a Pasteur pipette. The lower layer solution was dried in vacuum at 60°C for 24 hours to obtain a colorless, transparent liquid precursor. The viscosity of the liquid precursor at 40°C was 27,300 mPa·s. The resulting liquid precursor was heated in a nitrogen atmosphere at 200°C for 24 hours to obtain a cured product with a thickness of 4.8 mm. The appearance of the resulting cured product (top view) is shown in Figure 7(a).

[0088] (Examples 29 to 31) Cured products were obtained in the same manner as in Example 28, except that the heating conditions for the liquid precursor were changed as shown in Table 5. The appearances of the obtained cured products (photographs taken from above) are shown in Figure 7(b) to (d). In Figure 7, (b) is the cured product of Example 29, (c) is the cured product of Example 30, and (d) is the cured product of Example 31.

[0089] <Hardness Measurement> The pencil hardness of the cured product was measured by a manual scratching method in accordance with the pencil scratch test specified in the old JIS K5400. First, the tip of the pencil to be tested was placed perpendicular to 400-grit abrasive paper placed on a hard, flat surface, and the tip was ground so that the tip was flat and the corners were sharp. The sharpened lead was placed at a 45° angle to the surface of the cured product, and while pressing the lead against the coating surface as hard as possible without breaking it, the tester pushed the pencil forward at a uniform speed of approximately 1 cm to scratch the coating surface. The pushing speed was approximately 1 cm / s. The tip of the pencil lead was sharpened after each scratch, and the test was repeated five times using a pencil of the same concentration symbol. The concentration symbol one level lower than the hardness of the pencil that caused tears or cuts in the coating film two or more times out of five tests was recorded. The evaluation criteria were as follows, from hardest to hardest: 9H, 8H, 7H, 6H, 5H, 4H, 3H, 2H, H, F, HB, B, 2B, 3B, 4B, 5B, 6B. The results are shown in Table 5.

[0090]

[0091] The results in Table 5 and Figures 5 to 7 show that Examples 25 to 27 had high hardness and produced sufficiently thick, transparent cured bodies. In particular, Example 27 produced a cured body 15.6 mm thick. In contrast, Examples 28 and 29 produced bubbles, resulting in poor appearance and low pencil hardness. Example 30 developed many cracks on the surface after heat treatment, and Example 31 suppressed bubble generation compared to Examples 28 and 29, but also produced partial poor appearance and low pencil hardness. These results demonstrate that the combined use of a trifunctional silicon alkoxide and a bifunctional silicon alkoxide, each of which has a methyl group as the organic functional group, produces a cured body with high hardness and improved appearance.

[0092] Test Example 6 Example 32 The cured body of Example 26 produced in Test Example 5 was cut into a size of 5 mm length x 5 mm width x 4 mm height to prepare a sample of Example 32.

[0093] Example 33 The cured product of Example 29 prepared in Test Example 5 was cut into a size of 5 mm length x 5 mm width x 4 mm height to prepare a sample of Example 33.

[0094] Example 34 A commercially available polymethyl methacrylate (PMMA) resin ("Acrylite (registered trademark) L001" manufactured by Mitsubishi Chemical Corporation) was prepared. The PMMA resin was cut into a size of 5 mm length × 5 mm width × 4 mm height to prepare a sample for Example 34.

[0095] Example 35 A commercially available polyethylene terephthalate (PET) resin ("Sunroid Pet Ace EPG100" manufactured by Sumitomo Bakelite Co., Ltd.) was prepared. The PET resin was cut into a size of 5 mm length × 5 mm width × 4 mm height to prepare a sample for Example 35.

[0096] <Uniaxial loading / unloading test> Compression was applied to each sample at 0.5 mm / min under displacement control, and the stress-strain curve was measured. Subsequently, the stress-strain curve was measured when the sample was unloaded at 0.5 mm / min. The results are shown in Figure 8.

[0097] 8, it was found that Example 32 exhibited strong elastic behavior, with the strain returning to a state close to the initial state upon unloading, compared with Examples 34 and 35. Moreover, Example 33 yielded under high stress and did not return to the initial state even after unloading.

[0098] Test Example 7 The ultraviolet absorption edge wavelength was determined using the cured product of Example 26 prepared in Test Example 5.

[0099] <Measurement of UV-Visible Light Absorption Spectrum> The UV-visible light absorption spectrum was measured using a spectrophotometer ("U-4100" manufactured by Hitachi High-Tech Corporation) and normalized by the sample thickness to obtain a spectrum of the light absorption coefficient. The UV absorption edge wavelength was determined as the intersection of the approximation line of the spectrum in the UV absorption edge region of the obtained light absorption spectrum and the approximation line of the baseline spectrum in the transparent region on the long wavelength side. The UV absorption edge was observed near 195 nm, which indicated that the sample had high transparency in the UV region.

[0100] (Test Example 8) (Example 36) The liquid precursor of Example 9 (viscosity at 40°C: 23,300 mPa·s) prepared in Test Example 1 was heated in a nitrogen atmosphere at 200°C for 12 hours and then at 250°C for 24 hours to obtain a cured product.

[0101] (Example 37) Methyltrimethoxysilane, a trifunctional silicon alkoxide, and dimethoxydimethylsilane, a bifunctional silicon alkoxide, were mixed in a molar ratio of 0.75:0.25 (methyltrimethoxysilane:dimethoxydimethylsilane) so that the total molar ratio was 1, resulting in a total of 100 mmol. Dilute hydrochloric acid consisting of 0.2 mmol of hydrogen chloride (HCl / silicon ratio 0.002) and 3,000 mmol of water (water / silicon ratio 30) was added thereto, and the mixture was stirred at 20°C for 3 hours in a sealed container. The mixture was then allowed to stand at 80°C for 24 hours to mature, allowing hydrolysis and polycondensation to proceed. After aging, the mixture was cooled to room temperature, the container was opened, and the upper layer solution, which had undergone liquid-liquid phase separation, was extracted and removed with a Pasteur pipette. The lower layer solution was dried under vacuum at 60°C for 24 hours, yielding a colorless, transparent liquid precursor. The viscosity of the liquid precursor at 40°C was 50,400 mPa·s. The resulting liquid precursor was heated in a nitrogen atmosphere at 200° C. for 12 hours and then at 250° C. for 24 hours to obtain a cured product.

[0102] Example 38 The cured product of Example 26 prepared in Test Example 5 was used.

[0103] Example 39 A colorless, transparent liquid precursor was obtained in the same manner as in Example 37, except that the amounts of methyltrimethoxysilane, dimethoxydimethylsilane, hydrogen chloride, and water used were changed as shown in Table 6. The viscosity of the liquid precursor at 40°C was 1 x 10 ６ The resulting liquid precursor was heated in a nitrogen atmosphere at 150° C. for 12 hours and then at 250° C. for 24 hours to obtain a cured product.

[0104] Example 40 The cured product of Example 29 prepared in Test Example 5 was used.

[0105] <Hardness Measurement> The Vickers hardness of the cured product was measured in accordance with JIS R 1610-2003. The results are shown in Table 6.

[0106]

[0107] The results in Table 6 show that Examples 36 to 39 all had a Vickers hardness of 4 or higher, and that Examples 38 and 39, in which the ratio of methyltrimethoxysilane to the total silicon alkoxide was 0.8 or higher, exhibited elastic recovery to the extent that indentation could not be observed. In contrast, Example 40 had a low Vickers hardness of 2.8 and was unable to maintain hardness.

[0108] Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. This application is based on a Japanese patent application (Patent Application No. 2023-138037) filed on August 28, 2023, the contents of which are incorporated herein by reference.

Claims

1. A polysilsesquioxane-based liquid precursor containing a copolymer of a trifunctional silicon alkoxide and a bifunctional silicon alkoxide, wherein the residual silanol group fraction f in the copolymer is ＳｉＯＨ is 0.02 to 0.

3.

2. Viscosity at 40°C is 1 x 10 ６ 2. The polysilsesquioxane-based liquid precursor of claim 1, having a viscosity of less than or equal to mPa·s.

3. The polysilsesquioxane liquid precursor of claim 1, wherein the trifunctional silicon alkoxide comprises 80 mol % or more of methyltrimethoxysilane based on the total mol % of the trifunctional silicon alkoxide.

4. The polysilsesquioxane-based liquid precursor of claim 1, wherein the bifunctional silicon alkoxide comprises 80 mol % or more of dimethoxydimethylsilane based on the total mol % of the bifunctional silicon alkoxide.

5. A cured copolymer of a trifunctional silicon alkoxide and a bifunctional silicon alkoxide, wherein the residual silanol group fraction in the copolymer is f ＳｉＯＨ A hardened body, wherein the viscosity is 0.02 to 0.

3.

6. The cured product described in claim 5, wherein the trifunctional silicon alkoxide contains 80 mol % or more of methyltrimethoxysilane based on the total mol % of the trifunctional silicon alkoxide.

7. The cured product described in claim 5, wherein the bifunctional silicon alkoxide contains 80 mol % or more of dimethoxydimethylsilane based on the total mol % of the bifunctional silicon alkoxide.

8. The cured product according to claim 5, having a pencil hardness of HB or more.

9. The hardened body according to claim 5, having a Vickers hardness of 1 HV or more.

10. The cured product according to claim 5, having an ultraviolet absorption edge wavelength of 250 nm or less.

11. The hardened body according to claim 5, having a thickness of 4.8 mm or more.

12. The cured product according to claim 5, which is used for electric / electronic parts.

13. A method for producing a polysilsesquioxane-based liquid precursor, comprising maturing a trifunctional silicon alkoxide and a difunctional silicon alkoxide during hydrolysis and polycondensation reactions in an aqueous solution in the presence of an acid catalyst without using an organic solvent.

14. The method for producing a polysilsesquioxane liquid precursor according to claim 13, wherein the trifunctional silicon alkoxide is used in an amount of 0.5 to 0.99 mol per 1 mol of the total silicon alkoxide.

15. The method for producing a polysilsesquioxane-based liquid precursor according to claim 13, wherein the acid catalyst is used in an amount of more than 0 mol and not more than 0.01 mol per 1 mol of the total silicon alkoxide.

16. The method for producing a polysilsesquioxane liquid precursor according to claim 13, wherein 1.5 to 50 mol of water is used per mol of the total silicon alkoxide.

17. The method for producing a polysilsesquioxane-based liquid precursor according to claim 13, wherein the trifunctional silicon alkoxide contains 80 mol % or more of methyltrimethoxysilane based on the total mol % of the trifunctional silicon alkoxide.

18. The method for producing a polysilsesquioxane-based liquid precursor according to claim 13, wherein the bifunctional silicon alkoxide contains 80 mol % or more of dimethoxydimethylsilane based on the total mol % of the bifunctional silicon alkoxide.

19. A method for producing the polysilsesquioxane-based liquid precursor of claim 13, comprising removing the alcohol produced in the hydrolysis reaction.

20. A method for producing a cured product, comprising heating and curing a polysilsesquioxane liquid precursor obtained by the method for producing a polysilsesquioxane liquid precursor according to any one of claims 13 to 19.

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