CN109824853B - Method for synthesizing polyurethane prepolymer, prepolymer and casting polyurethane elastomer - Google Patents
Method for synthesizing polyurethane prepolymer, prepolymer and casting polyurethane elastomer Download PDFInfo
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Abstract
The invention relates to a method for synthesizing isocyanate group-terminated polyurethane prepolymer, the prepolymer and a casting polyurethane elastomer containing the prepolymer; the synthesis method comprises the following steps: a first step: mixing and heating a polyol with a first portion of a polyisocyanate in a reactor to react to about the theoretical NCO value to obtain a first liquid, wherein the molar ratio of the total amount of isocyanate groups in the first portion of the polyisocyanate to the total amount of hydroxyl groups in the polyol is R1; and a second step: adding a second part of polyisocyanate into the first liquid, mixing and heating to react to about a theoretical NCO value so as to obtain a prepolymer, wherein the molar ratio of isocyanate groups of all polyisocyanates to hydroxyl groups of polyhydroxy substances in the prepolymer synthesis formula is R; wherein R and R1 need to satisfy a defined relationship.
Description
Technical Field
The invention relates to a method for synthesizing isocyanate-terminated polyurethane prepolymer, the prepolymer and a casting polyurethane elastomer containing the prepolymer.
Background
The casting polyurethane elastomer (CPU) is prepared by reacting oligomer polyol, polyisocyanate and a chain-extending crosslinking agent. According to the type of oligomer polyol, the polyol is divided 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 the chain extension crosslinking agent, the chain extension crosslinking agent is divided into alcohol chain extension type, amine chain extension type and the like.
The CPU processing is usually a two-step method, also called prepolymer method or prepolymer method; firstly, reacting oligomer polyol with polyisocyanate under certain conditions to generate prepolymer; and secondly, adding a chain-extending cross-linking agent (also called a chain extender) into the prepolymer, and curing, molding and post-curing under certain conditions.
The casting polyurethane elastomer used as an industrial accessory has products such as sealing elements, sieve plates, cutter cutting boards, printer scrapers and the like for coal mines, and often has higher requirements on the mechanical properties (such as modulus, tearing strength, permanent deformation and the like) of materials; at the same time, the hardness required for the above applications is often limited to a narrow range, typically 2 degrees (shore a). How to strengthen the mechanical properties (such as modulus, tear strength and permanent deformation) on the premise of keeping the hardness of the material basically unchanged is a problem to be solved by industry relatives. Changing the NCO content of the prepolymer, or adjusting the formulation composition of the prepolymer or elastomeric article, is a common solution that either does not have a significant improvement or makes it difficult to balance modulus, tear strength, and permanent set with other properties such as material elasticity, low temperature, etc.
Disclosure of Invention
The invention aims to provide a method for synthesizing isocyanate-terminated polyurethane prepolymer, the prepolymer and a casting polyurethane elastomer containing the prepolymer. The present inventors have conducted intensive studies to solve the above problems, and as a result, have found that the mechanical properties (e.g., modulus, tear strength, and permanent set) and process processability of an elastomer product can be effectively enhanced within a certain range by changing the synthesis method of a prepolymer without changing the formulation of a polyurethane prepolymer and a cast polyurethane elastomer product, and that the application sites having high requirements for the elastomer product can be better matched, thereby completing the present invention.
In order to achieve one aspect of the above object, the present invention provides the following technical solutions:
a method of synthesizing an isocyanate group-terminated polyurethane prepolymer, the method comprising:
a first step: mixing a polyol with a first portion of a polyisocyanate and heating to react to about theoretical NCO value to obtain a first liquid, wherein the molar ratio of the total amount of isocyanate groups in said first portion of polyisocyanate to the total amount of hydroxyl groups in said polyol is R1; and
a second step: adding a second part of polyisocyanate into the first liquid, mixing and heating to react to about a theoretical NCO value so as to obtain a prepolymer, wherein the molar ratio of isocyanate groups of all polyisocyanates to hydroxyl groups of polyhydroxy substances in the prepolymer synthesis formula is R;
wherein R and R1 satisfy the following relationship:
when R is more than or equal to 1.80 and less than or equal to 2.20, R is more than 1 and less than or equal to 0.94R and less than or equal to 1;
when R is more than 2.20 and less than or equal to 3.00, R is more than 1 and less than or equal to 0.88R in 1;
when R is more than 3.00, R1 is more than 1 and less than or equal to 0.80R;
the first portion of polyisocyanate is the same or different from the second portion of polyisocyanate. In the context of the present invention, "about the theoretical NCO value" means that the difference between the NCO value reached in the reaction and the theoretical NCO value is between. + -. 0.5% of the theoretical NCO value, preferably between. + -. 0.2% of the theoretical NCO value.
According to the synthesis method of the present invention, preferably, R and R1 satisfy the following relationship,
when R is 1.80 ≦ 2.20, R1 is (0.70-0.94) R, such as 0.75R, 0.8R, 0.85R, or 0.9R;
when R is more than 2.20 and less than or equal to 3.00, R1 is (0.60-0.88) R, such as 0.65R, 0.7R, 0.75R, 0.8R or 0.85R;
when R > 3.00, R1 is (0.50-0.80) R, such as 0.55R, 0.6R, 0.65R, 0.7R, or 0.75R.
According to the synthesis method of the present invention, preferably, in the first process step, the polyhydroxy substance is an oligomeric polyol, and optionally a small molecule diol or/and triol. In the present invention, the expression "optional" may or may not be present.
According to the synthesis method of the present invention, preferably, in the first process step, the reactant of the reaction further includes an additive, and the additive includes one or more of acid chloride, phosphoric acid and phosphate.
According to the synthesis method of the present invention, preferably, the first step is carried out under continuous stirring at a reaction temperature of 60 to 90 ℃, such as 70 ℃ or 80 ℃, for a reaction time of 1 to 12 hours, such as 2,4, 6, 8 or 10 hours; the second step is carried out under continuous stirring at a temperature of 60-90 deg.C, such as 70 deg.C or 80 deg.C, for a reaction time of 0.5-2h, such as 1 or 1.5 h.
In order to achieve another aspect of the above object, the present invention also provides an isocyanate group-ended polyurethane prepolymer produced according to the above synthesis method.
In order to achieve another aspect of the above objects, the present invention also provides a cast polyurethane elastomer prepared by mixing and reacting reaction raw materials comprising a chain-extending crosslinking agent and the isocyanate group-terminated polyurethane prepolymer according to claim 7.
By adopting the novel isocyanate-terminated polyurethane prepolymer synthesis method, the mechanical properties (such as modulus, tear strength, permanent deformation and the like) and the process manufacturing performance and the like of the elastomer product can be effectively enhanced within a certain range on the premise of not changing the formula composition of the polyurethane prepolymer and the cast polyurethane elastomer product, so that the application places with higher requirements on the elastomer product can be better matched.
Detailed Description
The present invention will be described in detail below.
The invention relates to a method for synthesizing isocyanate-terminated polyurethane prepolymer, the prepolymer and a casting polyurethane elastomer containing the prepolymer.
Prepolymer synthesis
The cast polyurethane elastomer (CPU) product is prepared by reacting Toluene Diisocyanate (TDI) or diphenylmethane diisocyanate (MDI) type prepolymer with amine or small molecular alcohol chain-extending cross-linking agent. The TDI-type prepolymer is usually prepared from amine chain-extending crosslinking agent, such as 3,3 '-dichloro-4, 4' -diaminodiphenylmethane (MOCA), 3, 5-dimethylthiotoluenediamine (DMTDA), diethyltoluenediamine (DETDDA), etc.; the MDI type prepolymer is usually prepared from small molecular alcohol chain-extending crosslinking agent, such as glycol, 1, 4-butanediol, propylene glycol, 1, 6-hexanediol, 1, 4-cyclohexanediol, neopentyl glycol, hydroquinone bis (beta-hydroxyethyl) ether (HQEE), hydrogenated bisphenol A, resorcinol dihydroxyethyl ether (HER), etc.; and triols such as trihydroxypropane and glycerol, which are determined mainly based on the processing technology of the product and the performance requirements of the product.
The NCO content of the TDI prepolymer with the amine chain extension is generally distributed between 4.0 and 7.0 weight percent, and the NCO content of the MDI prepolymer with the alcohol chain extension is generally distributed between 6.0 and 9.0 weight percent, which is mainly used for distributing the obtained CPU product between 80 and 98A Shore; considering the NCO content and the molecular mass difference of TDI and MDI, the molar ratio R of isocyanate groups to hydroxyl groups in the synthesis process of the TDI prepolymer is usually 2.0 +/-0.2, and R is the molar ratio of the isocyanate groups of all polyisocyanates to the hydroxyl groups of polyhydroxy substances in the synthesis formula of the prepolymer; the R values of MDI prepolymers are generally higher, even above 3.00.
In the present invention, R1 is the molar ratio of isocyanate groups of polyisocyanate to hydroxyl groups of polyhydroxy material in the first step, and R1 at least comprise the following relationship:
when R is more than or equal to 1.80 and less than or equal to 2.20, R1 is more than or equal to 1 and less than or equal to 0.94R, preferably, R1 is more than or equal to 0.70R and less than or equal to 0.94R;
when R is more than 2.20 and less than or equal to 3.00, R1 is more than 1 and less than or equal to 0.88R, preferably, R1 is more than or equal to 0.60R and less than or equal to 0.88R;
when R > 3.00, 1 < R1 ≦ 0.80R is preferred, 0.50R ≦ R1 ≦ 0.80R,
in the first procedure, calculating the ratio of polyisocyanate to hydroxyl-containing material according to the R1 value, the hydroxyl value or equivalent of the polyhydroxy material and the NCO content of the polyisocyanate, adding the polyhydroxy material into the polyisocyanate, mixing and heating to react to about the theoretical NCO value, thereby obtaining a first liquid;
the first step is preferably carried out under continuous stirring, and the reaction can be protected by nitrogen as required; the mode of adding the polyhydroxy substance is according to the known mode in the industry, namely adding in batches, so as to ensure that the temperature of the reactant system is maintained between 60 and 90 ℃; in order to further protect the reaction of the first procedure, avoid the phenomenon of over-quick temperature rise, even gelation and implosion, and simultaneously, corresponding additives such as acyl chloride, phosphoric acid or phosphate ester can be added, and the acyl chloride, the phosphoric acid or the phosphate ester is generally added into the polyhydroxy substance firstly, and the addition amount is different from several ppm to hundreds of ppm; the synthesis reaction time of the first step is 1-12 h.
In the second step, the polyisocyanate is added into the first liquid, mixed and heated to react, the added polyisocyanate is the same as or different from that in the first step, and the molar ratio of the isocyanate group to the hydroxyl group in the reaction system is R; maintaining the temperature of the reaction system at 60-90 ℃, and continuously stirring; the synthesis reaction time of the second procedure is 0.5-2 h.
A second step of optionally adding a defoaming assistant, and performing vacuum defoaming or the like; the selection and addition of the assistant defoaming agent and the process control of vacuum defoaming are carried out according to the known mode in the industry.
Casting type polyurethane elastomer (CPU) and prepolymer raw material and formula selection
According to the practical application condition and the processing technology requirement, proper CPU product raw materials and formula components are selected, wherein the proper CPU product raw materials comprise polyisocyanate, polyhydroxy substances and chain-extending cross-linking agents.
Cast polyurethane elastomer (CPU) and prepolymer raw material
Polyisocyanates
The polyisocyanate to which the present invention relates may be a polyisocyanate commonly used in the art for preparing polyurethane elastomers, comprising mainly Toluene Diisocyanate (TDI) and diphenylmethane diisocyanate (MDI); the TDI contains two isomers of 2,4-TDI and 2,6-TDI, the products sold in the market are a mixture of the two isomers, and the products are divided into three specifications of TDI-100, TDI-80 and TDI-65 according to the mass ratio of the 2, 4-TDI; MDI comprises two isomers of 4,4 ' -MDI and 2,4 ' -MDI, and the commercial products are divided into MDI-100 and MDI-50 specifications according to the mass ratio of the 4,4 ' -MDI, and in addition, carbodiimide modified C-MDI is also included. Of course, it is understood by those skilled in the art that it may also comprise other polyisocyanates besides TDI and MDI, such as Hexamethylene Diisocyanate (HDI), isophorone diisocyanate (IPDI), cyclohexylmethane diisocyanate (HMDI), 1, 5-Naphthalene Diisocyanate (NDI), p-phenylene diisocyanate (PPDI), 3' -dimethylbiphenyl diisocyanate (TODI), and the like.
Polyhydroxy materials
The polyol materials to which the present invention relates may be those commonly used in the art for preparing polyurethane elastomers, and preferably may be oligomeric polyols, and optionally comprise small molecule diols or/and triols. In the present invention, the oligomer polyol means a polymeric polyol having a molecular weight of not more than 4000, such as 3000, such as one or more of polyoxypropylene glycol, polytetramethylene ether glycol, polyester diol and polycaprolactone diol.
The polyoxypropylene diol to which the present invention relates is a conventional product which is obtained by ring-opening polymerization of propylene oxide in the presence of an active hydrogen-containing compound as an initiator and a catalyst. The molecular weight of the polypropylene oxide glycol for the elastomer is 400-3000, and different specifications are mainly distinguished by molecular weight; in addition to molecular weight, the product specifications of polyoxypropylene glycol include acid number, pH, moisture content, unsaturation, and catalyst type selection. They are well known in the industry and will not be listed here.
The polytetramethylene ether glycol of the present invention is a conventional product, and is a polyether glycol obtained by ring-opening polymerization of tetrahydrofuran. The molecular weight of the polytetramethylene ether glycol for the elastomer is 600-2000, and different specifications are mainly distinguished by molecular weight; in addition to the molecular weight, the product index of polytetramethylene ether glycol includes acid value, moisture content, color, and the like. They are well known in the industry and will not be listed here.
The invention relates to polyester dihydric alcohol, which is mainly formed by polycondensation of dibasic fatty carboxylic acid and polyhydric alcohol. The dicarboxylic acid is adipic acid, and the polyhydric alcohols include ethylene glycol, 1, 2-propanediol, 1, 4-butanediol, diethylene glycol, neopentyl glycol, and 1, 6-hexanediol. The molecular weight of the polyester diol for the elastomer is 1000-2000, and different specifications are mainly distinguished by molecular weight; in addition to molecular weight, the product index of the polyester diol includes acid value, moisture content, viscosity, chroma, iron compound content, etc. They are well known in the industry and will not be listed here.
The polycaprolactone diol is prepared by the ring-opening polymerization of caprolactone in the presence of an initiator and a catalyst. The elastomer is prepared by using polycaprolactone diol with the molecular weight of 500-4000, and different specifications are mainly distinguished by molecular weight; in addition to molecular weight, the product index of polycaprolactone diol includes acid value, water content, viscosity, chroma, initiator type, molecular weight distribution, etc. Typical suppliers and products include the Placcel series of the japanese cellosolve chemical industry corporation and the Capa series of the swedish Perstorp, which are well known raw materials in the industry and will not be listed here.
The present invention relates to small molecule diols or triols which are aliphatic diols or triols having a molecular weight of no more than 400, such as 300.
Wherein the small molecule diol such as an aliphatic diol includes, but is not limited to, the following diols: ethylene glycol, 1, 4-butanediol, diethylene glycol, triethylene glycol, 1, 2-propanediol, neopentyl glycol, methylpropanediol, 1, 6-hexanediol, and 1, 3-propanediol, or a mixture of one or more thereof.
The small molecule trihydric alcohols include, but are not limited to, the following trihydric alcohols: trimethylolpropane, glycerol, trimethylolethane, 1,2, 6-hexanetriol, etc., or a mixture of one or more thereof.
Chain-extending cross-linking agent
The present invention relates to chain extending and crosslinking agents including, but not limited to, the following diamines, diols and triols: diamines such as 3,3 '-dichloro-4, 4' -diaminodiphenylmethane (MOCA), 3, 5-dimethylthiotoluenediamine (DMTDA) and diethyltoluenediamine (DETDA); diols such as ethylene glycol, 1, 4-butanediol, propylene glycol, 1, 6-hexanediol, 1, 4-cyclohexanediol, neopentyl glycol, hydroquinone bis (. beta. -hydroxyethyl) ether (HQEE), hydrogenated bisphenol A, and resorcinol dihydroxyethyl ether (HER); triols such as trihydroxypropane and glycerol.
Molding of cast polyurethane elastomer (CPU)
The CPU forming method can adopt a forming method known in the industry, such as a manual batch method or a mechanical continuous method. The manual batch method comprises the processes of prepolymer weighing, heating/constant temperature, defoaming, chain extension crosslinking agent adding, mixing, secondary defoaming, pouring and the like. Heating/keeping the temperature of the prepolymer at 70-85 ℃, mixing and stirring for 0.5-2 minutes, and defoaming for 1-6 minutes for the second time.
The invention relates to a CPU molding process, namely a molding process or a vulcanization process known in the industry; the vulcanization process is divided into three stages of molding vulcanization, post vulcanization and post curing; the molding and vulcanizing temperature is preferably 100-; the post-vulcanization temperature is preferably 90-110 ℃, and the time is preferably 10-48 hours; post-curing is the placing of the post-vulcanized CPU at room temperature or slightly elevated temperature for 3-7 days.
The advantages of the present invention will be further illustrated by the following examples.
The experimental methods contained in the examples listed include: the NCO content and viscosity (80 ℃) of the prepolymer, and the hardness, resilience and mechanical properties of the CPU product.
Hardness: the test is carried out according to GB/T531.1-2008 by using a Japanese TECCLOCK Shore A durometer.
Springback: a Taiwan high-speed rail detection instrument GT-7042-V1 resiliometer is adopted for testing according to GB/T1681-2009.
Mechanical properties: the modulus (100% stress at definite elongation and 300% stress at definite elongation), tensile strength and elongation at break of the standard dumbbell-shaped test piece are tested according to GB/T528-.
And (3) permanent tensile deformation: the standard dumbbell specimen was pulled to 300% strain at a rate of 200mm/min for 10min, then the external force was removed at the same rate and the test specimen length was changed after 10min recovery, with a test environment temperature of 26 + -1 deg.C.
Compression set: the compression set was tested according to GBT/7759-.
The raw materials contained in the exemplified examples are specifically as follows:
MDI: diphenylmethane diisocyanate having an NCO content of about 33.5% (wanhua chemistry,
)；
TDI-100: toluene diisocyanate, NCO content about 48.2%, Hungarian Bosu chemical;
diol P1: adipic acid copolymerized with 1, 4-butanediol and 1, 6-hexanediol and having a hydroxyl number of about 59.1mgKOH/g, BG/HG 0.85/1(mol) (homemade);
diol P2: polytetramethylene ether glycol having a hydroxyl number of about 112.2mgKOH/g, basf corporation.
BDO: 1, 4-butanediol, basf corporation.
TMP: trimethylolpropane, Shandong Fufengpastol.
MOCA: 3,3 '-dichloro-4, 4' -diaminodiphenylmethane, suzhou xiangyuan.
Unless otherwise specified, the reagents used below were all analytical grade.
Example 1
Preparation of isocyanate-terminated polyurethane prepolymers
According to the theoretical NCO value (8.0%) of the prepolymer, the R value of a total formula system (MDI/P1) is calculated to be 3.689, R1 is set to be 2.162, and the feeding proportion of a first procedure is calculated according to R1, namely MDI: p1 (100: 350.17 by mass), phosphoric acid (85 wt% concentration) was added in an amount of 12ppm based on the total amount of the first step reaction product, and the reaction was stirred at 70 to 80 ℃ for 3 hours, and the NCO value was measured to be about 4.00%; calculating the feeding amount of MDI in the second procedure according to the R value and the feeding amount of MDI and P1 in the first procedure, stirring and reacting for 0.5 hour at 70-80 ℃, and determining the NCO value to be about 8.0 percent; and (4) after vacuum defoaming for 0.5h, sealing after nitrogen purging for later use.
Preparation of casting type polyurethane elastomer
Firstly, pretreating a chain extension crosslinking agent, heating and melting 1, 4-Butanediol (BDO) and Trimethylolpropane (TMP), uniformly mixing the BDO/TMP (70/30) according to the proportion, and carrying out vacuum dehydration at 110 ℃ for about 2 hours for later use; secondly, according to the prepolymer: respectively weighing the chain extension cross-linking agent in a ratio of 100:8, respectively preheating to 80 ℃ and 40 ℃, mixing and stirring (1500rpm) for about 45 seconds, then defoaming in vacuum for about 4min until no bubbles overflow, then pouring the mixture into a mold preheated to 110 ℃, curing in a 110 ℃ oven, and demolding after about 1 hour; and finally, demolding the cured sample, transferring the cured sample into a 100 ℃ oven, curing for 15h, taking out the sample, curing for more than 3 days at normal temperature, and testing the performance of the sample.
Examples 2 to 4
Referring to example 1, isocyanate-terminated polyurethane prepolymer preparation was carried out with the synthesis recipe parameters as given in table one.
The physical properties of the cast polyurethane elastomer samples are shown in Table II.
Comparative example 1
Preparation of isocyanate-terminated polyurethane prepolymers
The charge ratio of the formulation system (MDI/P1) was calculated from the theoretical NCO value of the prepolymer (8.0%), i.e. MDI: p1-100: 205.24 (mass ratio), phosphoric acid (85%) in an amount of 12ppm based on the total amount of the reaction mixture was added, the reaction mixture was stirred at 70 to 80 ℃ for 4 hours, the NCO value was measured to be about 8.0%, and after 0.5 hour of vacuum degassing, nitrogen gas was purged and sealed for future use.
Preparation of casting type polyurethane elastomer
Refer to example 1.
Example 5
Preparation of isocyanate-terminated polyurethane prepolymers
Calculating the R value of a total formula system (TDI-100/P2) to be 1.995 according to the theoretical NCO value (6.2%) of the prepolymer, setting R1 to be 1.496, and calculating the feeding ratio of a first procedure according to R1, namely TDI-100: p2-100: 382.30 (mass ratio) and stirred at 70-80 ℃ for 4 hours, and the NCO value was determined to be about 3.30%; calculating the feeding amount of TDI in the second procedure according to the R value and the feeding amount of TDI and P2 in the first procedure, stirring and reacting for 0.5 hour at 70-80 ℃, and determining the NCO value to be about 6.24%; and (4) after vacuum defoaming for 0.5h, sealing after nitrogen purging for later use.
Preparation of casting type polyurethane elastomer
Firstly, the chain-extending cross-linking agent is pretreated, and 3,3 '-dichloro-4, 4' -diaminodiphenylmethane is added
(MOCA) heating to melt for use; secondly, according to the prepolymer: respectively weighing the chain extension cross-linking agents in a ratio of 100:18, respectively preheating to 80 ℃ and 110 ℃, mixing and stirring (1500rpm) for about 45 seconds, then defoaming in vacuum for about 3min until no bubbles overflow, then pouring the mixture into a mold preheated to 110 ℃, curing in an oven at 110 ℃, and demolding after about 1 hour; and finally, demolding the cured sample, transferring the cured sample into a 100 ℃ oven, curing for 15h, taking out the sample, curing for more than 3 days at normal temperature, and testing the performance of the sample.
Examples 6 to 8
Referring to example 5, isocyanate-terminated polyurethane prepolymer preparation was carried out with the synthesis recipe parameters as given in table one.
Comparative example 2
Preparation of isocyanate-terminated polyurethane prepolymers
According to the theoretical NCO value (6.2%) of the prepolymer, the charge ratio of the formula system (TDI-100/P2) is calculated, namely TDI-100: p2 is 100:287.67 (mass ratio), the reaction is stirred for 4 hours at 70-80 ℃, the NCO value is measured to be about 6.19%, after 0.5 hour of vacuum defoamation, nitrogen is purged and sealed for standby.
Preparation of casting type polyurethane elastomer
Refer to example 5.
Example 9
Preparation of isocyanate-terminated polyurethane prepolymers
According to the theoretical NCO value (8.5%) of the prepolymer, the R value of the total formula system (MDI/P2) is calculated to be 2.696, R1 is set to be 1.754, and the feeding proportion of the first procedure is calculated according to R1, namely MDI: p2 (100: 227.34 by mass), phosphoric acid (85%) was added in an amount of 12ppm based on the total amount of the first step reaction product, and the reaction was stirred at 70 to 80 ℃ for 3 hours to obtain an NCO value of about 4.40%; calculating the feeding amount of MDI in the second procedure according to the R value and the feeding amount of MDI and P2 in the first procedure, stirring and reacting for 0.5 hour at 70-80 ℃, and determining the NCO value to be about 8.5%; and (4) after vacuum defoaming for 0.5h, sealing after nitrogen purging for later use.
Preparation of casting type polyurethane elastomer
Firstly, pretreating a chain extension crosslinking agent, heating and melting 1, 4-Butanediol (BDO), and then dehydrating in vacuum at 110 ℃ for about 2 hours for later use; secondly, according to the prepolymer: respectively weighing the chain extension cross-linking agent in a ratio of 100:8.7, respectively preheating to 80 ℃ and 40 ℃, mixing and stirring (1500rpm) for about 45 seconds, then defoaming in vacuum for about 4min until no bubbles overflow, then pouring the mixture into a mold preheated to 110 ℃, curing in an oven at 110 ℃, and demolding after about 1 hour; and finally, demolding the cured sample, transferring the cured sample into a 100 ℃ oven, curing for 15h, taking out the sample, curing for more than 3 days at normal temperature, and testing the performance of the sample.
Examples 10 to 12
Referring to example 9, isocyanate-terminated polyurethane prepolymer preparation was carried out with the synthesis recipe parameters as given in table one.
The physical properties of the cast polyurethane elastomer samples are shown in Table II.
Comparative example 3
Preparation of isocyanate-terminated polyurethane prepolymers
The charge ratio of the formulation system (MDI/P2) was calculated from the theoretical NCO value of the prepolymer (8.5%), i.e. MDI: p2 is 100:147.93 (mass ratio), phosphoric acid (85%) is added in an amount of 12ppm based on the total amount of the reaction mixture, the reaction mixture is stirred at 70 to 80 ℃ for 4 hours, the NCO value is measured to be about 8.0%, and after 0.5 hour of vacuum degassing, the reaction mixture is sealed after purging with nitrogen gas and is ready for use.
Preparation of casting type polyurethane elastomer
Reference is made to example 9.
Table A synthetic recipe parameters and indices for examples 1-12 and comparative examples 1-3
TABLE II physical Properties of samples of examples 1 to 12 and comparative examples 1 to 3
The results show that by adopting the isocyanate group-terminated polyurethane prepolymer synthesis method, the mechanical properties (such as modulus, tear strength, permanent deformation and the like) and the process manufacturing performance and the like of the elastomer product can be effectively enhanced in a certain range on the premise of not changing the formula composition of the polyurethane prepolymer and the cast polyurethane elastomer product, and the application places with higher requirements on the elastomer product can be better matched.
Claims (9)
1. A method of synthesizing an isocyanate group-terminated polyurethane prepolymer, the method comprising:
a first step: mixing a polyol with a first portion of a polyisocyanate and heating to react until the difference between the NCO value reached and the theoretical NCO value is within 0.5% of the theoretical NCO value, thereby obtaining a first liquid, wherein the molar ratio of the total amount of isocyanate groups in the first portion of the polyisocyanate to the total amount of hydroxyl groups in the polyol is R1; and
a second step: adding a second part of polyisocyanate into the first liquid, mixing and heating for reaction until the difference between the NCO value and the theoretical NCO value is +/-0.5% of the theoretical NCO value, thereby obtaining a prepolymer, wherein the molar ratio of the isocyanate groups of all the polyisocyanate to the hydroxyl groups of the polyhydroxy material in the synthesis formula of the prepolymer is R;
wherein R and R1 satisfy the following relationship:
when R is more than or equal to 1.80 and less than or equal to 2.20, R is more than 1 and less than or equal to 0.94R and less than or equal to 1;
when R is more than 2.20 and less than or equal to 3.00, R is more than 1 and less than or equal to 0.88R in 1;
when R is more than 3.00, R1 is more than 1 and less than or equal to 0.80R;
the first portion of polyisocyanate is the same or different from the second portion of polyisocyanate.
2. The method of synthesis according to claim 1, characterized in that: r and R1 satisfy the following relationship,
when R is more than or equal to 1.80 and less than or equal to 2.20, R1 is (0.70-0.94) R;
when R is more than 2.20 and less than or equal to 3.00, R1 is (0.60-0.88) R;
when R > 3.00, R1 is (0.50-0.80) R.
3. The method of synthesis according to claim 1, characterized in that: in the first process step, the polyol is an oligomeric polyol, and optionally a small molecule diol or/and triol.
4. The method of synthesis according to claim 2, characterized in that: in the first process step, the polyol is an oligomeric polyol, and optionally a small molecule diol or/and triol.
5. The synthesis method according to any one of claims 1 to 4, characterized in that: in the first process, the reactant of the reaction further comprises an additive, and the additive comprises one or more of acyl chloride, phosphoric acid and phosphate ester.
6. The method of synthesis according to claim 5, characterized in that: the first step is completed under continuous stirring, the reaction temperature is 60-90 ℃, and the reaction time is 1-12 h.
7. The method of synthesis according to claim 6, characterized in that: the second step is completed under continuous stirring, the reaction temperature is 60-90 ℃, and the reaction time is 0.5-2 h.
8. An isocyanate-terminated polyurethane prepolymer prepared according to the synthesis method of any one of claims 1 to 7.
9. A cast polyurethane elastomer, characterized by: prepared by mixing and reacting reaction starting materials comprising a chain-extended crosslinker and the isocyanate-terminated polyurethane prepolymer of claim 8.
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| CN112375205A (en) * | 2020-11-20 | 2021-02-19 | 南京艾德恒信科技有限公司 | Preparation method and application of high-strength polyurethane elastomer |
| CN114957595A (en) * | 2021-11-08 | 2022-08-30 | 上海联景高分子材料有限公司 | Polyurethane elastomer for chopping board and preparation method thereof |
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