CN112574386B

CN112574386B - Method for producing cast polyurethane elastomers with improved light transmission and use thereof as polishing pad window material

Info

Publication number: CN112574386B
Application number: CN202011404085.1A
Authority: CN
Inventors: 刘振东; 王凯; 罗建勋; 方璞
Original assignee: Wanhua Chemical Group Electronic Materials Co ltd
Current assignee: Wanhua Chemical Group Electronic Materials Co ltd
Priority date: 2020-12-03
Filing date: 2020-12-03
Publication date: 2022-08-05
Anticipated expiration: 2040-12-03
Also published as: CN112574386A

Abstract

The invention relates to a method for preparing casting polyurethane elastomer, which comprises specific casting and forming process conditions and the like, and specifically comprises the steps of firstly forming a casting mixture containing isocyanate-terminated polyurethane prepolymer, diamine chain extender and fluorine-containing hydrocarbon compound, then enabling the casting mixture to stay for a period of time under the specific temperature condition, and finally curing; the polyurethane elastomer material prepared by the method has improved light transmission performance on the premise of not losing mechanical properties such as hardness, storage modulus and the like; can be used as an optical endpoint detection material in Chemical Mechanical Polishing (CMP) processes, and the like.

Description

Method for producing cast polyurethane elastomers with improved light transmission and use thereof as polishing pad window material

Technical Field

The invention relates to a method for manufacturing a casting polyurethane elastomer, in particular to a casting polyurethane elastomer with improved light transmittance and application of the casting polyurethane elastomer as a polishing pad window material.

Background

The cast polyurethane elastomer (CPU) is prepared by reacting an oligomer polyol, a polyisocyanate and a chain extender. According to the type of oligomer polyol, it is classified into a polyoxypropylene ether type, a polytetramethylene ether type, a polyester type and a polycaprolactone type; according to the type of polyisocyanate, there are classified into TDI (toluene diisocyanate) type, MDI (diphenylmethane diisocyanate) type and other isocyanate type; according to the type of chain extender, the chain extender is classified into alcohol chain extender type and amine chain extender type.

Generally, a two-step process is used for CPU fabrication. Firstly, reacting oligomer polyol with polyisocyanate under certain conditions to generate prepolymer; and secondly, adding the chain extender into the prepolymer to form a mixture, injecting the mixture into a mold, and curing under certain conditions to obtain a final product.

In the industry, the molding and curing of a mixture of CPUs in a mold is also called a vulcanization process, and is divided into molding vulcanization, post-vulcanization and post-curing in sequence.

Form cure is the process of curing in a mold before demolding the CPU article. The temperature of the molding and vulcanization is preferably 100-120 ℃, the polyether type can be selected from 100-110 ℃, the polyester type can be selected from 110-120 ℃, and the demolding time is 10-60 minutes, on the basis that the product has demolding strength and does not generate permanent deformation during demolding; meanwhile, the utilization rate of the die and the equipment is also considered.

Post-cure is the process of continued heat curing after the article is demolded. The post-vulcanization temperature is generally lower than the shaping vulcanization temperature, preferably from 90 to 110 ℃ and the post-vulcanization time is from 10 to 48 hours, in order to complete the reaction of the NCO groups.

Post cure is the process by which the post cured product is allowed to stand at room temperature or slightly elevated temperature for a week to optimize the structure and physical properties of the product.

Polyurethane elastomer materials obtained by the casting process are widely used in various industries or working conditions. Included among these are applications as a window for a polishing pad during Chemical Mechanical Polishing (CMP).

The object of optically detecting the state of the wafer surface during CMP is achieved by means of a polishing pad window formed of a polyurethane material, as disclosed in CN1068814C, US6280290(B1), etc.

Prior art polishing pad windows, as disclosed in CN102310366B, the window material is a reaction product comprising an isocyanate terminated prepolymer and an amine based curative (e.g., 3 'dichloro-4, 4' -diphenylmethanediamine, MOCA). Specifically, the prepolymer is formed from the reaction of an aromatic isocyanate, comprising most preferably less than 12 weight percent aliphatic isocyanate, with polytetrahydrofuran diol (PTMEG) and has an NCO content of 8.75 to 9.40 weight percent. In one example, the casting process is described as mixing the prepolymer and MOCA, adding to the mold, heating in an oven at 93 ℃ for 20min, followed by heating in an oven at 104 ℃ for 15h40min, and finally cooling to 21 ℃ and holding for 2 h.

The above formulations and processes provide improved performance window materials, and polishing pads comprising the same exhibit reduced polishing defects (e.g., scratching of the substrate) during CMP. Disadvantageously, however, the window material has a relatively low optical transmission, e.g., 20-50% at 670nm (about 1.27mm thick), lacking the optical transmission required for demanding polishing applications.

It has been reported that the inventive examples, such as CN100347826C and CN102161182B, mainly based on aliphatic isocyanates, form aliphatic polyurethane window materials, achieving the purpose of improving the light transmission of windows:

J.V.H.Roberts is disclosed in CN100347826C, and a window material is formed by reacting a prepolymer formed from an aliphatic polyisocyanate and a hydroxyl group-containing material with a curing agent. In one embodiment, by maintaining at 65.6 deg.C

LW520 or LW570 (commercially available prepolymers containing aliphatic isocyanates) and a curing agent at room temperature were mixed and degassed, and the mixture was injected into a mold and cured at 104.4 ℃ for 18h to form a window material. Polishing pad windows comprising the window material have improved laser signal transmission, providing greater optical signal intensity (e.g., relative intensity as the beam exits/enters the window). Roberts believes that materials containing aromatic diisocyanates such as Toluene Diisocyanate (TDI) and diphenylmethane diisocyanate (MDI) often have high crystallinity and are not suitable for applications where light transmission is highly required;

in CN102161182B, a.lok et al disclose that a window material formed from a prepolymer of an aliphatic or cycloaliphatic isocyanate and a polyol, reacted with an amine-based chain extender, provides a polishing pad window fabricated therefrom having high optical transmission and durability for polishing applications, and does not exhibit window bulging.

In the aforementioned invention report, the window having improved light transmittance is a window material comprising aliphatic polyurethane formed from aliphatic isocyanate. Which is different from the aromatic polyurethane material forming the polishing layer. Known polishing pads, as disclosed in CN100353502C, relate to a polyurethane material which is the reaction product of a prepolymer comprising toluene diisocyanate and polytetrahydrofuran diol, and 4, 4' -methylene-bis-o-chloroaniline (MOCA). The difference of the chemical structures of the two materials will make the two materials have different physical properties.

The polishing pad window, as part of the polishing pad, must undergo interactions throughout the polishing process, which should have similar physical properties to the polishing pad material. In addition, in order to realize in-situ optical detection, it is necessary to have high transmittance for light of a certain wavelength. The aromatic polyurethane window material with improved light transmittance is prepared by selecting the material composition which is the same as or similar to that of the polishing layer, so that the contradiction between higher light transmittance requirement and better polishing performance can be balanced undoubtedly.

Disclosure of Invention

It is an object of the present invention to provide an aromatic polyurethane material that can be used as a polishing pad window, which has improved light transmission properties.

The present invention has been completed by finding that aromatic polyurethane elastomer materials having improved light transmittance under specific casting and molding process conditions are suitable for in situ optical end point detection applications such as in CMP processes.

The invention provides a method for manufacturing a casting type polyurethane elastomer with improved light transmission, which comprises the following steps: (1) a pretreatment step (2) and a curing step,

wherein the pretreatment step comprises:

firstly, forming a casting mixture at least containing isocyanate-terminated polyurethane prepolymer, diamine chain extender and fluorine-containing hydrocarbon compound; and

secondly, enabling the casting mixture to stay at the temperature T for a time T; wherein T is more than T0-80 and less than T0, T0 is the temperature value of the raw material of the isocyanate-terminated polyurethane prepolymer, and the unit is that T0 is 20-80; t is more than 0.1H and less than 6H, and H is hour;

the curing step is a curing step of allowing the product obtained in the pretreatment step to stay at a temperature of 80-120 ℃ for 12-48H.

In another aspect of the present invention, there is provided a cast polyurethane elastomer material having improved light transmittance prepared according to the aforementioned method.

In still another aspect of the present invention, there is provided a polishing pad window material formed by machining the cast polyurethane elastomer material having improved light transmittance.

The present invention will be described in detail below.

The method for manufacturing the casting type polyurethane elastomer with improved light transmission performance comprises the steps of (1) preprocessing and (2) curing.

The pretreatment step (1) of the present invention comprises:

firstly, forming a casting mixture at least comprising isocyanate-terminated polyurethane prepolymer, diamine chain extender and fluorine-containing hydrocarbon compound:

wherein the isocyanate-terminated polyurethane prepolymer is an isocyanate-terminated product formed from a starting material comprising an isocyanate component and polytetramethylene ether glycol, wherein the isocyanate component comprises at least Toluene Diisocyanate (TDI), and optionally dicyclohexylmethane diisocyanate (HMDI);

the toluene diisocyanate, preferably the mass fraction of 2,6-TDI is 0-20%, more preferably 10-20%;

the isocyanate component of the present invention may be a combination of toluene diisocyanate and dicyclohexylmethane diisocyanate, the content of HMDI in the isocyanate-terminated polyurethane prepolymer being < 12%;

the polytetramethylene ether glycol (PTMEG) of the present invention preferably has a molecular weight of 650-1500, more preferably 1000, and is commercially available from INVISTA, Mitsubishi, Germany, Basff, and the like. The PTMEG content in the isocyanate-terminated polyurethane prepolymer is 50 to 55 wt.%.

The isocyanate-terminated polyurethane prepolymer of the present invention generally comprises, in addition to the isocyanate component and the polytetramethylene ether glycol, a small molecule diol having a molecular weight of less than 200, such as a mixture of one or more selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol, 1, 2-propanediol, 1, 3-propanediol, dipropylene glycol, tripropylene glycol, 1, 3-butanediol, 1, 4-butanediol, 1, 5-pentanediol and 1, 6-hexanediol, preferably diethylene glycol (abbreviated as DEG); the content of the micromolecular dihydric alcohol in the isocyanate-terminated polyurethane prepolymer is less than 8 weight percent;

the isocyanate-terminated polyurethane prepolymer of the present invention can be prepared by a conventional method in the art. For example, from the raw material components including the isocyanate component, polytetramethylene ether glycol, and small molecule diol, etc., under continuous stirring. The reaction temperature is generally 40 to 90 ℃, preferably 55 to 75 ℃, and the reaction time is 1 to 12 hours, preferably 4 to 6 hours;

the isocyanate-terminated polyurethane prepolymer of the present invention, optionally, may have added thereto during the preparation thereof an amount of an acidic material comprising: acyl chlorides such as one or more mixtures of adipoyl chloride, benzoyl chloride and benzenesulfonyl chloride, and phosphate esters such as one or more mixtures of di-n-butyl phosphate and di-iso-octyl phosphate. The amount added is generally from 10 to 200ppm, based on the total amount of isocyanate-terminated polyurethane prepolymer.

In the preparation process of the isocyanate-terminated polyurethane prepolymer, the preferable dosage of TDI is 32-36 wt%, the dosage of HMDI is 3-11 wt%, the dosage of PTMEG is 50-55 wt%, and the dosage of micromolecular dihydric alcohol is 5-7 wt%;

the isocyanate-terminated polyurethane prepolymer preferably has an isocyanate group content of 6.0 to 12.0 wt%, more preferably 8.0 to 10.0 wt%.

In the method of the present invention, the diamine-based chain extender is one or more selected from the group consisting of 3,3 'dichloro-4, 4' -diphenylmethanediamine (MOCA), 3, 5-dimethylthiotoluenediamine (DMTDA), 3, 5-diethyltoluenediamine (DETDA), 4 'methylenebis (3-chloro-2, 6-diethylaniline) (M-CDEA), 4' methylenebis (2, 6-diethylaniline) (M-DEA) and 1, 3-propanediol bis (4-aminobenzoate) (740M), preferably 3,3 'dichloro-4, 4' -diphenylmethanediamine (MOCA), or a mixture of MOCA and M-CDEA, wherein the M-CDEA is present in the casting compound in an amount of < 2.0% by weight, and in some embodiments in an amount of 1.0 to 1.1% by weight of the casting compound.

In the process of the present invention, the molar ratio of the amino groups of the diamine-based chain extender to the isocyanate groups of the polyurethane prepolymer in the potting compound is from 0.7 to 1.1, preferably from 0.8 to 1.0.

In the method of the present invention, the fluorine-containing hydrocarbon compound is one or more selected from the group consisting of 1,1,1,3, 3-pentafluorobutane, 1,1,1,3, 3-pentafluoropropane, 1, 1-dichloro-1-fluoroethane, trans-1-chloro-3, 3, 3-trifluoropropene, and 1,1,1,4,4, 4-hexafluoro-2-butene; preferably 1,1,1,3, 3-pentafluorobutane (abbreviated as HFC-365mfc), commercially available product brands such as Solkane 365mfc (Solvay, Germany), Forane 365mfc (Arkema, France); and, 1,1,1,4,4, 4-hexafluoro-2-butene (abbreviated HFO-1336mzz), commercially available products such as Chemours Opteon, USA ^TM 1100。

The fluorocarbon-based compounds of the present invention are present in the casting mixture in an amount of 0.1 to 10.0 wt.%, preferably 1.0 to 8.0 wt.%, most preferably 2.0 to 5.0 wt.%. The fluorine-containing hydrocarbon compound is added according to the processing technology requirement, and the function of the fluorine-containing hydrocarbon compound is to remove the heat of a mixture system at the early stage of a forming reaction by virtue of the heated vaporization process of the fluorine-containing hydrocarbon compound, so that an article with uniform light transmission performance is obtained. The amount added does not take into account the quality of the final product to be obtained.

The process of forming the casting mixture comprises the following steps of weighing isocyanate-terminated polyurethane prepolymer, diamine chain extender and fluorine-containing hydrocarbon compound for later use, mixing and defoaming:

the weighing for standby comprises: according to the specification of the product to be obtained (such as length, width, height, 80, 66 and 25mm), calculating the required amount of the isocyanate-terminated polyurethane prepolymer, the diamine chain extender and the fluorine-containing hydrocarbon compound, weighing, and then placing at a certain temperature to ensure that the isocyanate-terminated polyurethane prepolymer, the diamine chain extender and the fluorine-containing hydrocarbon compound respectively have uniform raw material temperature; for example, the isocyanate-terminated polyurethane prepolymer may have a starting temperature value of 20 to 80 ℃, preferably 40 to 60 ℃, most preferably 50 ± 2 ℃; the temperature value of the diamine chain extender is 90-120 ℃, preferably 105-115 ℃; the temperature value of the fluorine-containing hydrocarbon compound is 0-20 ℃, preferably 5-10 ℃;

the mixing and defoaming comprises the steps of mixing and defoaming under vacuum and reduced pressure. As in one embodiment, this was achieved using an ARV series mixer from THINKY CORPORATION, Japan, for a treatment time < 180S, resulting in a casting mix.

The pretreatment step (1) of the present invention further comprises:

secondly, the casting mixture is kept at the temperature T for a time T (casting mixture pre-forming); wherein T is more than T0 and more than T0-80, T0 is the raw material temperature value of the isocyanate-terminated polyurethane prepolymer, the unit is that the temperature is 0.1H and more than T6H, and H is hour; preferably T0-60 < T0-10, 0.1H < T < 4H; more preferably T0-50 < T0-20, 0.1H < T < 1H; further, T < T0-35 is preferable;

the casting mixture is poured into a mold, and is preformed and cured under certain conditions. The die is preferably made of aluminum with a high heat conductivity coefficient, the die cavity is a cuboid, and the specification of the die is referred to the size of a product to be prepared and the shrinkage rate of the product. As in one embodiment, the article is 80 × 66 × 25mm long by wide, and the mold cavity is 81.8 × 67.0 × 25.5mm long by wide;

specifically, the procedure may be to leave the entire mold containing the casting mixture standing in an external environment at a temperature T for a residence time T; the external environment of the temperature T can be conveniently controlled if a constant temperature box with uniform temperature value is selected. Generally, a uniform temperature is advantageous to obtain articles with uniform optical and mechanical properties;

the process can also be that after the mixture is injected into the mould, the temperature of the flowing medium attached to the outside of the mould cavity is set to be T, and the temperature is maintained for T; the flowing medium attached to the outside of the mold cavity can be a liquid medium flowing along a preset path in an interlayer/jacket outside the mold cavity, such as pure water or an aqueous solution of ethylene glycol, and can also be dry air with a certain temperature blown along each surface of the mold, and a certain air temperature and air quantity can be maintained by means of a fan device; as in one embodiment, model XB-OTS-225HQThe equipment can provide uniform drying air with the air temperature of-40 to 120 ℃, and the air quantity is 12m ³ /min。

In the method of the invention, the pouring mixture in the mould does not usually reach the strength required for removing the mould within the retention time t although the pouring mixture is cured and formed; generally, the resin needs to be placed at a higher temperature for a period of time, such as 80-100 ℃, and the time is 0.5-2H, so that the resin can be removed, and the improvement of the production efficiency, the utilization rate of a die and the like is facilitated.

In the method of the present invention, the product obtained from the pretreatment step, i.e., the demolded product, is subjected to a curing step (2) which is a process of continuing heating and vulcanization to completely react the residual NCO groups.

In the method of the present invention, the curing step (2) is to keep the product at a temperature of 80 to 120 ℃ for 12 to 48 hours, preferably at a temperature of 95 to 115 ℃ for 16 to 24 hours.

Further, the product after completion of the post-vulcanization is preferably left to stand at room temperature or a slightly high temperature for 2 to 5 days to optimize the structure and physical properties of the product.

The invention also relates to a casting polyurethane elastomer with improved light transmission property, which is prepared by the method.

The polishing pad window material of the present invention is formed by machining the polyurethane elastomer material manufactured as described above, for example, by cutting, milling, and grinding, to form the desired window piece or window block.

The window sheets or window pieces of the present invention have different dimensional specifications to match the selected method of manufacturing the polishing pad containing the window; the window sheet is generally rectangular or oval, has a thickness of 1.25mm or 2.0mm, and is suitable for the pasting process to form a window on the polishing pad; the window block is usually a cuboid, the specification of which is matched with the polishing layer blank, and the window block is suitable for the integral process to prepare the polishing layer blank containing the window.

The invention has the beneficial effects that:

1. through pretreatment and curing of raw materials under specific conditions, the light transmittance of the CPU is improved, and the light transmittance reaches more than 60% (600 nm).

2. The prepared CPU can be applied to polishing pad window materials.

Detailed Description

The advantages of the present invention will be described in more detail with reference to examples.

The starting materials referred to in the examples and comparative examples comprise:

TDI-80: toluene diisocyanate, 2,6-TDI, at about 20% by weight, Vanhua chemical.

TDI-90: toluene diisocyanate, 2,6-TDI with the mass fraction of about 10%, is prepared from TDI-80 and TDI-100 according to the mass ratio of 1:1, wherein TDI-100 is a Wanhua chemical product.

HMDI: dicyclohexylmethane diisocyanate, wanhua chemistry.

PTMEG-1000: molecular weight 1000, mitsubishi chemical.

DEG: diethylene glycol, purity > 99.0 wt%, komi europe.

Diisooctyl phosphate (IOAP): purity > 99.4 wt%, and aladine.

Type i fluorocarbons: 1,1,1,3, 3-pentafluorobutane, explosion limit 3.6-13.3%, boiling point 40.2 ℃, Solvay, Germany.

Type II fluorocarbons: 1,1,1,4,4, 4-hexafluoro-2-butene, noncombustible, boiling point 33.0 ℃, U.S. Chemours.

Preparation example of isocyanate-terminated polyurethane prepolymer:

preparation of prepolymer a:

firstly, according to the theoretical proportion of prepolymer A, the formula is calculated as TDI-80: HMDI: PTMEG-1000: DEG ═ 100: 11: 152.7: 18 (mass ratio).

Next, a clean 500ml three-necked flask, a stirring paddle, etc. were taken, dried for use, and the heating system of the water/oil bath was checked. 100g of TDI-80, 11g of HMDI and 0.0395g of IOAP were weighed into a dry three-necked flask and mixed thoroughly by stirring continuously (150 rpm) at 20. + -. 2 ℃ for 15 min. 152.7g of PTMEG-1000 was weighed into a flask and stirred continuously (about 220rpm) while ensuring that the reaction mixture temperature was 85 ℃ or less and after the end of the addition, the reactant temperature was maintained at 70. + -. 2 ℃. After about 2h (PTMEG-1000 addition start meter), 18g of DEG was added to the flask and the reactant temperature was maintained at 70. + -. 2 ℃. After about 4h (counting at the end of the DEG addition), the NCO content was determined and was measured to be 8.5. + -. 0.2%, i.e.the end of the reaction was reached.

Finally, the prepolymer A is defoamed in vacuum for 0.5h, sealed and reserved.

Preparation of prepolymers B to F:

the preparation method is the same as that of prepolymer A, the synthesis formula is shown in Table 1, wherein the percentages of TDI, HMDI, PTMEG-1000 and DEG respectively account for the sum of the mass of the four raw materials; the ratio of IOAP refers to its ratio to the sum of the masses of TDI, HMDI, PTMEG-1000, DEG.

TABLE 1 formulation compositions of prepolymers A-F

Example 1

Preparation of a casting mixture:

first, 125g of prepolymer A, 30.2g of MOCA, and 1.89g of 1,1,1,3, 3-pentafluorobutane were weighed out in an oven at 50 ℃, 110 ℃ and 8 ℃ in accordance with [ -NH2]/[ -NCO ] (0.9), and the weighed materials were kept at a temperature of 50 ℃, 110 ℃ and 8 ℃ for 30 minutes.

Then, the three materials were quickly poured into a special mixing cup, and mixing and defoaming under vacuum reduced pressure were completed with the aid of an ARV-310 blender of the THINKY CORPORATION, Japan, and the treatment time was about 120S.

Finally, the casting mix was poured into an aluminum mold having a cavity size of 81.8 mm by 67.0 mm by 25.5 mm.

Performing a casting mixture:

first, a device model XB-OTS-225HQ was set to 6 deg.C (T) and preheated for 30 minutes.

Then, the aluminum mold containing the casting mixture is placed in an XB-OTS-225HQ device and stays for 30 minutes (t).

And finally, taking out the mold, placing the mold into a thermostat with the temperature of 100 ℃ for 1H, and demolding.

A curing process:

and (4) putting the product obtained in the pre-forming step into a thermostat at 105 ℃ again, and staying for 16H to finish curing for later use.

Examples 2 to 18

Referring to example 1, the casting compound preparation and casting compound pre-forming of examples 2-18, the formulations are shown in tables 2 and 3, respectively.

TABLE 2 compositions of the casting mixes of examples 1-18

TABLE 3 Process parameters for preforming the casting mixes of examples 1-18

	Prepolymer and temperature (T0)	T(℃)	t (minutes, Min)
				Example 1	A，50℃	6	30
Example 2	B，46℃	2	40
				Example 3	C，43℃	-6	55
Example 4	D，40℃	-10	55
				Example 5	E，55℃	10	30
Example 6	F，50℃	8	30
				Example 7	A，50℃	2	45
Example 8	B，46℃	-6	55
				Example 9	C，43℃	-10	55
Example 10	D，40℃	-14	55
				Example 11	E，55℃	18	10
Example 12	F，50℃	10	15
				Example 13	A，50℃	8	30
Example 14	B，46℃	0	30
				Example 15	C，43℃	-8	40
Example 16	D，40℃	-16	45
				Example 17	E，55℃	16	10
Example 18	F，50℃	6	30

Comparative example 1

First, 125g of prepolymer A and 30.2g of MOCA were weighed out in accordance with [ -NH2]/[ -NCO ] ═ 0.9, and the weighed materials were kept at 50. + -. 2 ℃ and 110. + -. 2 ℃ for 30 min.

Then, prepolymer A and MOCA were mixed, added to a mold, heated in an oven at 93 ℃ for 20min, then heated in an oven at 104 ℃ for 15h40min, finally cooled to 21 ℃ and left for 2 h. And (5) demolding for later use.

Comparative examples 2 to 6

Comparative examples 2-6 were prepared according to comparative example 1, and the formulations are given in Table 4.

TABLE 4 formulation compositions of comparative examples 1-6

	Prepolymers	Diamine chain extender	[-NH2]/[-NCO]
				Comparative example 1	A	MOCA	0.9
Comparative example 2	B	MOCA	0.9
				Comparative example 3	C	MOCA	0.9
Comparative example 4	D	MOCA	0.9
				Comparative example 5	E	MOCA	0.9
Comparative example 6	F	MOCA	0.9

The mechanical and optical performance tests of the samples prepared in the above examples and comparative examples are carried out, and the related test methods are as follows:

hardness: the test is carried out according to GB/T531.1-2008 by using a Japanese TECCLOCK Shore D hardness tester.

Storage modulus: e', quantitatively characterizing the ability of the polyurethane elastomeric material to exhibit an elastic behaviour in response to an applied deformation, measured in shear mode by model number DMA861E (METTLER company), at a frequency of 1Hz and at a rate of temperature increase of 3 ℃/min.

Light transmittance: the cast polyurethane elastomer obtained was cut into a polyurethane resin sheet having a thickness of about 2.0mm by a microtome (manufactured by FECKEN KIRFEL Co.), and the light transmittances at 500nm, 600nm and 700nm were measured by a Ci7X00 series desk type spectrophotometer (manufactured by X-RITE PANTONE Co.).

The mechanical and optical properties measured are shown in table 5.

TABLE 5 results of dynamic mechanical and light transmittance tests of examples 1-18 and comparative examples 1-6

Comparing the test results listed in Table 5, examples 1-18 have higher light transmittance with substantially the same hardness and storage modulus as comparative examples 1-6.

Claims

1. A method of making a cast polyurethane elastomer having improved light transmission, the method comprising: (1) a pretreatment step, and (2) a curing step,

wherein the pretreatment process comprises:

firstly, forming a casting mixture at least containing isocyanate-terminated polyurethane prepolymer, diamine chain extender and fluorine-containing hydrocarbon compound; wherein the fluorine-containing hydrocarbon compound is selected from one or more than two of 1,1,1,3, 3-pentafluorobutane, 1,1,1,3, 3-pentafluoropropane, 1, 1-dichloro-1-fluoroethane, trans-1-chloro-3, 3, 3-trifluoropropene and 1,1,1,4,4, 4-hexafluoro-2-butene, and the content of the fluorine-containing hydrocarbon compound in the casting mixture is 0.1-10.0 wt%;

and

secondly, enabling the casting mixture to stay at the temperature T for a time T;

wherein T is more than T0-80 and less than T0, T0 is the temperature value of the raw material of the isocyanate-terminated polyurethane prepolymer, and T0 is 20-80 ℃; t is more than 0.1h and less than 6h,

after the casting mixture stays at the temperature T for a time T, the casting mixture is required to be placed at 80-100 ℃ for 0.5-2h before the curing process is carried out.

2. The method of claim 1, wherein T0-60 < T0-10, 0.1h < T < 4 h.

3. The method of claim 2, wherein T0-50 < T0-20, 0.1h < T < 1 h.

4. The method of claim 1, wherein forming the casting compound comprises: enabling the isocyanate-terminated polyurethane prepolymer, the diamine chain extender and the fluorine-containing hydrocarbon compound to have uniform raw material temperatures respectively, and then mixing and defoaming to obtain a casting mixture;

wherein the temperature value of the raw material of the isocyanate-terminated polyurethane prepolymer is 40-60 ℃; the temperature value of the raw material of the diamine chain extender is 90-120 ℃; the temperature of the raw material of the fluorine-containing hydrocarbon compound is 0-20 ℃.

5. The method of claim 4, wherein the isocyanate-terminated polyurethane prepolymer has a raw material temperature value of 50 ± 2 ℃; the temperature value of the raw material of the diamine chain extender is 105-115 ℃; the temperature of the raw material of the fluorine-containing hydrocarbon compound is 5-10 ℃.

6. The method of claim 1, wherein the molar ratio of the amino groups of the diamine-based chain extender to the isocyanate groups of the polyurethane prepolymer in the casting mixture is from 0.7 to 1.1; the content of the fluorine-containing hydrocarbon compound in the casting mixture is 1.0 to 8.0 wt%.

7. The method of claim 6, wherein the molar ratio of the amino groups of the diamine-based chain extender to the isocyanate groups of the polyurethane prepolymer in the casting mixture is 0.8 to 1.0; the content of the fluorine-containing hydrocarbon compound in the casting mixture is 2.0 to 5.0 wt%.

8. The method according to any one of claims 1 to 7, wherein the isocyanate group content of the isocyanate-terminated polyurethane prepolymer is 6.0 to 12.0 wt.%,

the preparation raw materials comprise: isocyanate component, polytetramethylene ether glycol and micromolecular dihydric alcohol.

9. A process according to claim 8, wherein the isocyanate component is TDI, or a mixture of TDI and HMDI, the HMDI being present in the prepolymer in an amount of < 12%,

the molecular weight of the polytetramethylene ether glycol is 650-1500, the content of the polytetramethylene ether glycol in the prepolymer is 50-55 wt%,

the molecular weight of the small molecular dihydric alcohol is less than 200, and the small molecular dihydric alcohol is selected from one or more of ethylene glycol, diethylene glycol, triethylene glycol, 1, 2-propylene glycol, 1, 3-propylene glycol, dipropylene glycol, tripropylene glycol, 1, 3-butanediol, 1, 4-butanediol, 1, 5-pentanediol and 1, 6-hexanediol; the content of the small molecular diol in the prepolymer is less than 8 wt%.

10. The method of claim 9, wherein the small molecule diol is diethylene glycol.

11. The method of claim 9, wherein the isocyanate-terminated polyurethane prepolymer is prepared from TDI in an amount of 32 to 36 wt%, HMDI in an amount of 3 to 11 wt%, PTMEG in an amount of 50 to 55 wt%, and a small molecule diol in an amount of 5 to 7 wt%.

12. The process according to any one of claims 1 to 7, wherein the diamine-based chain extender is selected from one or more of 3,3 '-dichloro-4, 4' -diphenylmethanediamine (MOCA), 3, 5-dimethylthiotoluenediamine (DMTDA), 3, 5-diethyltoluenediamine (DETDA), 4 '-methylenebis (3-chloro-2, 6-diethylaniline) (M-CDEA), 4' -methylenebis (2, 6-diethylaniline) (M-DEA) and 1, 3-propanediol bis (4-aminobenzoate) (740M).

13. The process of claim 12 wherein said diamine chain extender is MOCA or a mixture of MOCA and M-CDEA, wherein the M-CDEA content of the casting mix is < 2.0 wt.%.

14. The method according to any one of claims 1 to 7, wherein the curing step is carried out by leaving the article at a temperature of 80 to 120 ℃ for 12 to 48 hours.

15. The method according to any one of claims 1 to 7, wherein the curing step is carried out by leaving the article at a temperature of 95 to 115 ℃ for 16 to 24 hours.

16. A cast polyurethane elastomer with improved light transmission prepared according to the process of any one of claims 1 to 15.

17. A polishing pad window material formed of the cast polyurethane elastomer of claim 16.