CN113185639B - A kind of high-strength low-relaxation polyisoprene rubber and its preparation method - Google Patents

Abstract

The invention belongs to the technical field of rubber, and particularly relates to high-strength low-relaxation polyisoprene rubber and a preparation method thereof. The invention provides modified polyisoprene rubber, which is prepared by vulcanizing polyisoprene containing unsaturated end groups. The invention utilizes the in-situ crosslinking of the end groups of the polyisoprene rubber containing unsaturated end groups during vulcanization, and utilizes the high density and high crosslinking degree of local functional groups of the polyisoprene rubber to form in-situ crosslinking nano particles or microphases with adjustable hardness and size. The formation of in-situ crosslinked nano particles increases the crosslinking density and entanglement density on one hand, and further strengthens the toughening rubber through strain amplification effect, nano particle deformation and the like on the other hand. In addition, the in-situ crosslinking nano particles are connected with the main chain through covalent bonds, so that the defect that stress relaxation is increased due to the fact that the inorganic nano filler reinforced rubber introduces weak bonds is overcome.

Description

A high-strength low-relaxation polyisoprene rubber and preparation method thereof

Technical Field

The invention belongs to the technical field of rubber, and in particular relates to a high-strength, low-relaxation polyisoprene rubber and a preparation method thereof.

Background Art

Functional filling rubber materials, damping pads and rubber structural components in strategic weapon equipment systems all require rubber materials to have the characteristics of high strength, high toughness and low relaxation, but there is a significant contradiction between high strength and low relaxation performance in rubber materials. Natural rubber materials have high strength, but the non-rubber components inside them will cause greater stress relaxation. Although isoprene rubber based on polyisoprene main chain overcomes the adverse effects of non-rubber components in natural rubber on stress relaxation performance, its strength is still somewhat different from that of natural rubber. The general method of reinforcing rubber is to reinforce it with nanofillers, but the commonly used filler reinforcement system introduces a large stress relaxation factor while reinforcing the rubber. Therefore, the development of rubber materials with both high strength and low relaxation characteristics has become one of the key material bottlenecks that need to be broken through in related equipment development plans and related industry fields at home and abroad.

Summary of the invention

In view of the above problems, the present invention provides a high-strength, low-relaxation polyisoprene rubber and a preparation method thereof, wherein the polyisoprene rubber has unsaturated end groups (including both end groups of the main chain and also block-type end groups), and the end groups can undergo in-situ crosslinking during vulcanization (the unsaturated bonds located at the end groups are more reactive, and due to their more rigid structure or polarity difference, they can be partially phase-separated, resulting in crosslinking between some end groups and end groups to form nanoparticles or microphases), and by utilizing the high density and high degree of crosslinking of local functional groups, in-situ crosslinked nanoparticles or microphases with adjustable hardness and size can be formed. The formation of in-situ crosslinked nanoparticles increases the crosslinking density and entanglement density on the one hand, and further strengthens the toughened rubber through strain amplification effect, nanoparticle deformation, etc. on the other hand. In addition, the in-situ crosslinked nanoparticles are connected to the main chain through covalent bonds, which overcomes the defect of increased stress relaxation caused by the introduction of weak bonds into inorganic nanofiller-reinforced rubber (the inorganic nanofiller and the rubber molecular chain are combined through van der Waals forces or weak bonds).

The technical solution of the present invention:

The first technical problem to be solved by the present invention is to provide a modified polyisoprene rubber, wherein the modified polyisoprene rubber is prepared by vulcanizing polyisoprene containing unsaturated end groups; the unsaturated end groups include the end groups at both ends of the polyisoprene main chain, and also include block-type end groups. Since the polyisoprene used has unsaturated end groups, the end groups can be in-situ cross-linked during the vulcanization process, thereby playing a role of toughening and strengthening. In addition, the in-situ cross-linked nanoparticles are connected to the main chain through covalent bonds, which overcomes the defect of introducing weak bonds to reinforce the rubber by introducing inorganic nanofillers, which leads to increased stress relaxation, that is, it plays a role of toughening and strengthening while reducing stress relaxation.

Further, the polyisoprene containing unsaturated terminal groups is prepared by the following method 1:

Method 1: The functional precursor is aged and reacted at 40-60° C. for 30-100 minutes under the action of a catalyst; then isoprene is added and the reaction is continued at 40-60° C. for 8-15 hours; the obtained product is washed and dried to obtain polyisoprene containing unsaturated terminal groups;

Wherein, the functional precursor is selected from at least one of the following substances:

Among them, R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , R ₁₀ , R ₁₁ , R ₁₂ and R ₁₃ are alkyl chains or cyclic structures having 0 to 20 carbon atoms.

Furthermore, the molar ratio of the functional precursor to the catalyst is 20-50:1, and the molar ratio of the functional precursor to isoprene is 1:50-500, preferably 1:100-300.

Furthermore, the catalyst is a mixture of substances F, G and H, and the molar ratio of F, G and H is: F:G:H=0.8~1.2:15~25:1~3; wherein substance F is neodymium neodecanoate or neodymium isopropoxide or neodymium phosphate, substance G is triisobutylaluminum or diisobutylaluminum hydride, and substance H is diisobutylaluminum chloride or dimethylsilyl dichloride; preferably, F:G:H=1:10:1.

Furthermore, in the above method 1, after the reaction is completed, acidified ethanol is added dropwise to quench the reaction, and the obtained product is washed with acidified water and ethanol multiple times and dried in vacuum at 30-50°C.

Further, the polyisoprene containing unsaturated terminal groups is prepared by the following method 2:

Method 2: Dissolve polar polyisoprene rubber in a reaction solvent, add unsaturated monomers and condensation agents, and carry out condensation reaction at room temperature for 8 to 18 hours to obtain polyisoprene containing unsaturated end groups; the unsaturated monomers are selected from at least one of the following substances:

Among them, R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , R ₁₀ , R ₁₁ , R ₁₂ and R ₁₃ are alkyl chains or cyclic structures having 0 to 20 carbon atoms.

Furthermore, the polar polyisoprene rubber includes at least one of the following substances:

Wherein, D is -OH, -COOH or -NH ₂ , E is an alkyl chain or a cyclic structure of 0 to 20 carbon atoms; 10≤x≤10000, 5≤y≤20, 5≤m≤20, 100≤n≤10000, 5≤l≤20. Preferably, 100≤x≤1000, 10≤y≤15, 10≤m≤15, 100≤n≤1000.

Furthermore, in the above method 2, the reaction solvent is tetrahydrofuran, chloroform, dichloromethane, n-hexane or toluene; wherein the ratio of polar polyisoprene rubber to the reaction solvent is: 0.5-2 g/100 mL.

Further, in the above method 2, the condensing agent is selected according to the following principles:

When a condensation reaction of a carboxyl group with a hydroxyl group or an amino group occurs, the condensing agent is selected from the group consisting of dicyclohexylcarbodiimide (DCC), N,N'-diisopropylcarbodiimide (DIC), N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC.HCl), 4,5-dicyanoimidazole (DCI), N,N'-carbonyldiimidazole (CDI), N-hydroxysuccinimide (NHS(HOSu)), sodium salt of N-hydroxysulfosuccinimide (Sulfo-NHS), 1-hydroxy-7-azobenzotriazole (HOAT), 1-hydroxybenzotriazole (HOBt), 6-chloro-1-hydroxybenzotriazole (Cl-HOBt), O-(7- one of benzotriazole-N,N,N',N'-tetramethyluronium hexafluorophosphate (HATU), benzotriazole-N,N,N',N'-tetramethyluronium hexafluorophosphate (HBTU), O-benzotriazole-N,N,N',N'-tetramethyluronium tetrafluoroborate (TBTU), 6-chlorobenzotriazole-1,1,3,3-tetramethyluronium hexafluorophosphate (HCTU), O-(1,2-dihydro-2-oxo-pyridyl)-1,1,3,3-tetramethyluronium tetrafluoroborate (TPTU), N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ), and bis(2-oxo-3-oxazolidinyl)phosphinoyl chloride (BOP-Cl);

When the self-condensation and mutual condensation reaction of hydroxyl and amino groups occurs, the condensation agent is selected from the group consisting of diisopropyl azodicarboxylate (DIAD), diethyl azodicarboxylate (DEAD), benzotriazole-1-yl-oxytripyrrolidinophosphine hexafluorophosphate (PyBOP), benzotriazole-1-tris(trimethylamino)-hexafluorophosphate (BOP), and tripyrrolidinophosphonium bromide hexafluorophosphate (PyBrOP);

When a condensation reaction of acyl chloride with amino, hydroxyl or carboxyl occurs, the condensation agent is an organic base, such as one of triethylamine, triethylenediamine (DABCO), 1,8-diazabicycloundec-7-ene (DBU), 1,5-diazabicyclo[4.3.0]non-5-ene (DBN), 4-dimethylaminopyridine (DMAP), pyridine, N-methylmorpholine, tetramethylethylenediamine, tetramethylguanidine (TMG), potassium/sodium tert-butoxide, N,N-diisopropylethylamine (DIPEA) and diisopropylamine (DIPA).

Furthermore, in the above method 2, the molar ratio of the polar polyisoprene rubber, the unsaturated monomer and the condensing agent is: polar polyisoprene rubber: unsaturated monomer: condensing agent = 1:5-15:5-15, preferably 1:8-12:8-12.

Furthermore, the vulcanization refers to: the polyisoprene with unsaturated terminal groups is mixed with a vulcanizing agent and an auxiliary agent by twin-roll milling or solution blending, and then vulcanized and molded at a high temperature.

Furthermore, the vulcanization temperature is 120° C. to 190° C., and the vulcanization time is 15 to 120 min; preferably 140 to 150° C., 20 to 40 min.

Further, the vulcanizing agent is sulfur, tetramethylthiuram disulfide (TMTD), dipentamethylenethiuram tetrasulfide (DPTT) (TRA), 4-(2-benzothiazolyl disulfide)morpholine (MDB), tetraethylthiuram disulfide (TETD), tetrabutylthiuram disulfide (TBTD), tetramethylthiuram tetrasulfide (TMTT), 4,4'-dimorpholine disulfide (DTDM), N,N-polysulfide bis(dimethylamine), N,N'-polysulfide bis(diethylamine), cyclohexylthiuram disulfide (CTS ... At least one of 2-diisopropylamine, diisopropylbenzene peroxide (DCP), di-tert-butyl peroxide (DTBP), 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane (DBPMH), benzoyl peroxide (BPO), 2,4-dichlorobenzoyl peroxide (DCPB), tert-butyl perbenzoate (TBPB), di-tert-butylperoxyisopropylbenzene (BIPB), 3,3,5,7,7-pentamethyl-1,2,4-triepoxyhexane (PMTO), and cumyl hydroperoxide (CHP).

Furthermore, auxiliary agents may be added during the vulcanization process as required, and the auxiliary agents include zinc oxide, stearic acid, antioxidants, anti-aging agents or vulcanization accelerators.

Furthermore, the vulcanization formula in the vulcanization process is: 0.5 to 5 parts of vulcanizing agent, preferably 1 to 3 parts, 0.5 to 3 parts of vulcanization accelerator, 3 to 8 parts of zinc oxide, 1 to 4 parts of stearic acid, 1 to 3 parts of antioxidant, and 1 to 3 parts of antioxidant.

Furthermore, the double-roller blending time is 5 to 30 minutes, preferably 12 to 18 minutes; the solvent used in the solution blending includes tetrahydrofuran, chloroform, dichloromethane, n-hexane or toluene; the stirring time of the solution blending is 1 to 24 hours, preferably 2 to 8 hours.

The second technical problem to be solved by the present invention is to provide a method for preparing the modified polyisoprene rubber. The method comprises: selecting polyisoprene containing unsaturated end groups as a raw material, and preparing the modified polyisoprene rubber by vulcanizing the polyisoprene containing unsaturated end groups.

The third technical problem to be solved by the present invention is to provide a polyisoprene containing an unsaturated terminal group, wherein the polyisoprene containing an unsaturated terminal group is prepared by the following method 1 or method 2:

Method 1: The functional precursor is aged and reacted at 40-60° C. for 30-100 minutes under the action of a catalyst; then isoprene is added and the reaction is continued at 40-60° C. for 8-15 hours; the obtained product is washed and dried to obtain polyisoprene containing unsaturated terminal groups;

Wherein, the functional precursor is selected from at least one of the following substances:

wherein R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , R ₁₀ , R ₁₁ , R ₁₂ and R ₁₃ are alkyl chains or cyclic structures having 0 to 20 carbon atoms;

Method 2: Dissolve polar polyisoprene rubber in a reaction solvent, add unsaturated monomers and condensation agents, and carry out condensation reaction at room temperature for 8 to 18 hours to obtain polyisoprene containing unsaturated end groups; the unsaturated monomers are selected from at least one of the following substances:

Among them, R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , R ₁₀ , R ₁₁ , R ₁₂ and R ₁₃ are alkyl chains or cyclic structures having 0 to 20 carbon atoms.

Furthermore, in the above method 1, the molar ratio of the functional precursor to the catalyst is 20-50:1, and the molar ratio of the functional precursor to isoprene is 1:50-500, preferably 1:100-300.

Furthermore, in the above method 1, the catalyst is a mixture of substances F, G and H, and the molar ratio of F, G and H is: F:G:H=0.8~1.2:15~25:1~3; wherein substance F is neodymium neodecanoate or neodymium isopropoxide or neodymium phosphate, substance G is triisobutylaluminum or diisobutylaluminum hydride, and substance H is diisobutylaluminum chloride or dimethylsilyl dichloride; preferably, F:G:H=1:10:1.

Furthermore, in the above method 2, the polar polyisoprene rubber comprises at least one of the following substances:

Wherein, D is -OH, -COOH or -NH ₂ , E is an alkyl chain or a cyclic structure of 0 to 20 carbon atoms; 10≤x≤10000, 5≤y≤20, 5≤m≤20, 100≤n≤10000, 5≤l≤20. Preferably, 100≤x≤1000, 10≤y≤15, 10≤m≤15, 100≤n≤1000.

Furthermore, in the above method 2, the reaction solvent is tetrahydrofuran, chloroform, dichloromethane, n-hexane or toluene; wherein the ratio of polar polyisoprene rubber to the reaction solvent is: 0.5-2 g/100 mL.

Further, in the above method 2, the condensing agent is selected according to the following principles:

When a condensation reaction of a carboxyl group with a hydroxyl group or an amino group occurs, the condensing agent is selected from the group consisting of dicyclohexylcarbodiimide (DCC), N,N'-diisopropylcarbodiimide (DIC), N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC.HCl), 4,5-dicyanoimidazole (DCI), N,N'-carbonyldiimidazole (CDI), N-hydroxysuccinimide (NHS(HOSu)), sodium salt of N-hydroxysulfosuccinimide (Sulfo-NHS), 1-hydroxy-7-azobenzotriazole (HOAT), 1-hydroxybenzotriazole (HOBt), 6-chloro-1-hydroxybenzotriazole (Cl-HOBt), O-(7- one of benzotriazole-N,N,N',N'-tetramethyluronium hexafluorophosphate (HATU), benzotriazole-N,N,N',N'-tetramethyluronium hexafluorophosphate (HBTU), O-benzotriazole-N,N,N',N'-tetramethyluronium tetrafluoroborate (TBTU), 6-chlorobenzotriazole-1,1,3,3-tetramethyluronium hexafluorophosphate (HCTU), O-(1,2-dihydro-2-oxo-pyridyl)-1,1,3,3-tetramethyluronium tetrafluoroborate (TPTU), N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ), and bis(2-oxo-3-oxazolidinyl)phosphinoyl chloride (BOP-Cl);

When the self-condensation and mutual condensation reaction of hydroxyl and amino groups occurs, the condensation agent is selected from the group consisting of diisopropyl azodicarboxylate (DIAD), diethyl azodicarboxylate (DEAD), benzotriazole-1-yl-oxytripyrrolidinophosphine hexafluorophosphate (PyBOP), benzotriazole-1-tris(trimethylamino)-hexafluorophosphate (BOP), and tripyrrolidinophosphonium bromide hexafluorophosphate (PyBrOP);

When a condensation reaction of acyl chloride with amino, hydroxyl or carboxyl occurs, the condensation agent is an organic base, such as one of triethylamine, triethylenediamine (DABCO), 1,8-diazabicycloundec-7-ene (DBU), 1,5-diazabicyclo[4.3.0]non-5-ene (DBN), 4-dimethylaminopyridine (DMAP), pyridine, N-methylmorpholine, tetramethylethylenediamine, tetramethylguanidine (TMG), potassium/sodium tert-butoxide, N,N-diisopropylethylamine (DIPEA) and diisopropylamine (DIPA).

Furthermore, in the above method 2, the molar ratio of the polar polyisoprene rubber, the unsaturated monomer and the condensing agent is: polar polyisoprene rubber: unsaturated monomer: condensing agent = 1:5-15:5-15, preferably 1:8-12:8-12.

The fourth technical problem to be solved by the present invention is to provide a method for improving the strength of polyisoprene rubber while reducing its stress relaxation, the method comprising: firstly modifying polyisoprene to obtain polyisoprene containing unsaturated end groups, and then vulcanizing the polyisoprene.

Further, the method for modifying polyisoprene to obtain polyisoprene containing unsaturated end groups is one of the following two methods:

Method 1: The functional precursor is aged and reacted at 40-60° C. for 30-100 minutes under the action of a catalyst; then isoprene is added and the reaction is continued at 40-60° C. for 8-15 hours; the obtained product is washed and dried to obtain polyisoprene containing unsaturated terminal groups;

Wherein, the functional precursor is selected from at least one of the following substances:

wherein R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , R ₁₀ , R ₁₁ , R ₁₂ and R ₁₃ are alkyl chains or cyclic structures having 0 to 20 carbon atoms;

Method 2: Dissolve polar polyisoprene rubber in a reaction solvent, add unsaturated monomers and condensation agents, and carry out condensation reaction at room temperature for 8 to 18 hours to obtain polyisoprene containing unsaturated end groups; the unsaturated monomers are selected from at least one of the following substances:

Among them, R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ , R ₉ , R ₁₀ , R ₁₁ , R ₁₂ and R ₁₃ are alkyl chains or cyclic structures having 0 to 20 carbon atoms.

Furthermore, in the above method 1, the molar ratio of the functional precursor to the catalyst is 20-50:1, and the molar ratio of the functional precursor to isoprene is 1:50-500, preferably 1:100-300.

Furthermore, in the above method 1, the catalyst is a mixture of substances F, G and H, and the molar ratio of F, G and H is: F:G:H=0.8~1.2:15~25:1~3; wherein substance F is neodymium neodecanoate or neodymium isopropoxide or neodymium phosphate, substance G is triisobutylaluminum or diisobutylaluminum hydride, and substance H is diisobutylaluminum chloride or dimethylsilyl dichloride; preferably, F:G:H=1:10:1.

Furthermore, in the above method 2, the polar polyisoprene rubber comprises at least one of the following substances:

Wherein, D is -OH, -COOH or -NH ₂ , E is an alkyl chain or a cyclic structure of 0 to 20 carbon atoms; 10≤x≤10000, 5≤y≤20, 5≤m≤20, 100≤n≤10000, 5≤l≤20. Preferably, 100≤x≤1000, 10≤y≤15, 10≤m≤15, 100≤n≤1000.

Furthermore, in the above method 2, the reaction solvent is tetrahydrofuran, chloroform, dichloromethane, n-hexane or toluene; wherein the ratio of polar polyisoprene rubber to the reaction solvent is: 0.5-2 g/100 mL.

Further, in the above method 2, the condensing agent is selected according to the following principles:

When a condensation reaction of a carboxyl group with a hydroxyl group or an amino group occurs, the condensing agent is selected from the group consisting of dicyclohexylcarbodiimide (DCC), N,N'-diisopropylcarbodiimide (DIC), N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC.HCl), 4,5-dicyanoimidazole (DCI), N,N'-carbonyldiimidazole (CDI), N-hydroxysuccinimide (NHS(HOSu)), sodium salt of N-hydroxysulfosuccinimide (Sulfo-NHS), 1-hydroxy-7-azobenzotriazole (HOAT), 1-hydroxybenzotriazole (HOBt), 6-chloro-1-hydroxybenzotriazole (Cl-HOBt), O-(7- one of benzotriazole-N,N,N',N'-tetramethyluronium hexafluorophosphate (HATU), benzotriazole-N,N,N',N'-tetramethyluronium hexafluorophosphate (HBTU), O-benzotriazole-N,N,N',N'-tetramethyluronium tetrafluoroborate (TBTU), 6-chlorobenzotriazole-1,1,3,3-tetramethyluronium hexafluorophosphate (HCTU), O-(1,2-dihydro-2-oxo-pyridyl)-1,1,3,3-tetramethyluronium tetrafluoroborate (TPTU), N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ), and bis(2-oxo-3-oxazolidinyl)phosphinoyl chloride (BOP-Cl);

When the self-condensation and mutual condensation reaction of hydroxyl and amino groups occurs, the condensation agent is selected from the group consisting of diisopropyl azodicarboxylate (DIAD), diethyl azodicarboxylate (DEAD), benzotriazole-1-yl-oxytripyrrolidinophosphine hexafluorophosphate (PyBOP), benzotriazole-1-tris(trimethylamino)-hexafluorophosphate (BOP), and tripyrrolidinophosphonium bromide hexafluorophosphate (PyBrOP);

When a condensation reaction of acyl chloride with amino, hydroxyl or carboxyl occurs, the condensation agent is an organic base, such as one of triethylamine, triethylenediamine (DABCO), 1,8-diazabicycloundec-7-ene (DBU), 1,5-diazabicyclo[4.3.0]non-5-ene (DBN), 4-dimethylaminopyridine (DMAP), pyridine, N-methylmorpholine, tetramethylethylenediamine, tetramethylguanidine (TMG), potassium/sodium tert-butoxide, N,N-diisopropylethylamine (DIPEA) and diisopropylamine (DIPA).

Beneficial effects of the present invention:

The present invention utilizes the polyisoprene rubber containing unsaturated end groups to be crosslinked in situ during vulcanization, and utilizes the high density and high crosslinking degree of its local functional groups to form hard-soft, size-adjustable in situ crosslinked nanoparticles or microphases. The formation of in situ crosslinked nanoparticles increases the crosslinking density and entanglement density on the one hand, and further strengthens the toughening rubber through strain amplification effect, nanoparticle deformation, etc. on the other hand. In addition, the in situ crosslinked nanoparticles are connected with the main chain through a covalent bond, which overcomes the defect that the inorganic nanofiller reinforced rubber introduces weak bonds to cause stress relaxation to increase (the inorganic nanofiller and the rubber molecular chain are weakly combined through van der Waals force or weak bonds).

The present invention prepares a modified polyisoprene rubber with unsaturated bonds at both ends or branched end groups of a rubber molecule chain, and after the obtained polyisoprene containing unsaturated groups is vulcanized, its end groups can form locally highly cross-linked nanoparticles or microphases, thereby increasing the toughness of the rubber and simultaneously giving the rubber material low relaxation properties. The strength of the vulcanized rubber reaches 25MPa, and the elongation at break is 840%, which is comparable to Hainan natural rubber. The tensile strain is 40%, and the stress relaxation is 3.5% in 3 hours, which is much lower than the relaxation rate of natural rubber and even lower than that of vulcanized isoprene rubber. It can be seen that the present invention provides a new idea for synthesizing high-strength, low-relaxation polyisoprene rubber.

Description of the drawings:

FIG. 1 is a hydrogen nuclear magnetic resonance spectrum of OAIR obtained in Example 1.

FIG. 2 is a hydrogen nuclear magnetic resonance spectrum of HIR obtained in Example 2.

FIG3 is a hydrogen nuclear magnetic resonance spectrum of AIR obtained in Example 3.

Figure 4a and Figure 4b are transmission electron microscopy images of OAIR-V and IR-V, respectively.

FIG5 is a stress-strain curve of OAIR-V, HIR-V, AIR-V, NR-V and IR-V obtained in Examples and Comparative Examples.

FIG6 is the fitting curves of stress relaxation of OAIR-V, HIR-V, AIR-V, NR-V and IR-V.

FIG. 7 is a diagram showing the mechanism of obtaining modified polyisoprene rubber by vulcanization of polyisoprene containing unsaturated terminal groups according to the present invention.

DETAILED DESCRIPTION

The modified polyisoprene rubber main chain end group or block end group prepared by the present invention contains unsaturated bonds, and can form locally highly cross-linked nanoparticles or microphases with adjustable hardness and size (the longer the length of the side chain, the higher the degree of freedom of the unsaturated bonds on the chain, and the softer the formed nanoparticles; the longer the length of the block end group, the larger the nanoparticles formed by in-situ cross-linking), during vulcanization, thereby increasing the terminal entanglement density. In addition, the unique nanoparticle reinforcement and toughening effect makes the strength and elongation at break of the vulcanized rubber comparable to those of Hainan natural rubber, and the stress relaxation rate is much lower than that of vulcanized natural rubber.

The specific implementation modes of the present invention are further described below in conjunction with embodiments, but the present invention is not limited to the scope of the embodiments.

The raw materials used in the embodiments of the present invention are:

1,2-undecadiene (Moreau JL, Gaudemar M. Journal of Organometallic Chemistry. 1976, 108: 159-164) and 3-methylene-1,8-diene (Li Baojian, Wang Ziyu, Zhou Zhijun, et al. Method for preparing new phytadiene compounds from fatty acids:, 2017.) were synthesized according to the methods reported in the literature. Neodymium neodecanoate [Nd(VA) ₃ ] from Meryer Company, with a solid content of 0.69 g/mL, and the solvent is n-hexane; triisobutylaluminum [Al(i-Bu) ₃ ] and diisobutylaluminum chloride [Al(i-Bu) ₂ Cl] from Acros Chemical Company, with concentrations of 1.1 M and 0.8 M, respectively; isoprene from Alfa Company, which was refluxed with calcium hydride for 2 hours and then distilled for use. Both n-hexane and tetrahydrofuran solvents need to be dehydrated with sodium/benzophenone and then distilled for use. Natural rubber was provided by the Chinese Academy of Tropical Agricultural Sciences. Commercial isoprene rubber was provided by PetroChina Dushanzi Petrochemical Company. Vulcanizing agents from Adamas Chemical included sulfur, vulcanization accelerator CZ, antioxidant RD, antioxidant 4020, zinc oxide (ZnO), and stearic acid. Other pharmaceutical reagents, unless otherwise specified, were provided by Shanghai Titan Technology Co., Ltd.

Example 1

Nd(VA) ₃ , 1,2-undecadiene, Al(i-Bu) ₃ and Al(i-Bu) ₂ Cl were slowly injected into a sealed glass bottle in sequence and aged at 50°C for 60 minutes; then isoprene monomer was added and the reaction continued at 50°C for 12 hours; finally, a small amount of acidified ethanol was added to quench the reaction; the polymerization product was washed with acidified water and ethanol for multiple times, and then vacuum dried at 40°C to obtain n-octyl allene isoprene rubber (OAIR). The reaction equation is shown in Formula I, and the reaction ratio and the physical properties of the synthetic rubber are shown in Table 1.

100 parts of n-octyl allene isoprene rubber, 5 parts of zinc oxide, and 2 parts of stearic acid are mixed, and 1 part of antioxidant 4020, 1 part of antioxidant RD, 1 part of vulcanization accelerator CZ and 2 parts of sulfur are mixed and vulcanized in an open mill to obtain OAIR-V.

Example 2

The 1,2-undecadiene in Example 1 was replaced with 3-methylene-1,8-diene, and other conditions were kept unchanged, and hexenyl isoprene rubber (HIR) and HIR-V were synthesized according to the method of Example 1. The reaction equation is shown in Formula III, and the reaction ratio and physical properties of the synthetic rubber are shown in Table 1.

Example 3

Hydroxylated isoprene rubber (B-PIP-OH) was dissolved in THF, and acryloyl chloride, triethylamine and DMAP were added. The ratio of polar isoprene rubber: acryloyl chloride: triethylamine and DMAP was 1:10:10. The reaction was carried out at room temperature for 12 hours. After the reaction, the mixture was washed three times in methanol and finally dried in a vacuum oven at 40°C to obtain acrylate-based isoprene rubber (AIR). The reaction equation is shown in Formula IV.

100 parts of AIR, 5 parts of zinc oxide, and 2 parts of stearic acid were mixed, and 1 part of antioxidant 4020, 1 part of antioxidant RD, 1 part of vulcanization accelerator CZ and 2 parts of sulfur were mixed and vulcanized in an open mill to obtain AIR-V.

Comparative Example 1

100 parts of commercial polyisoprene rubber, 5 parts of zinc oxide, 2 parts of stearic acid were mixed, 1 part of antioxidant 4020, 1 part of antioxidant RD, 1 part of vulcanization accelerator CZ and 2 parts of sulfur were mixed and vulcanized in an open mill to obtain IR-V.

Comparative Example 2

100 parts of natural rubber, 5 parts of zinc oxide, 2 parts of stearic acid are mixed, 1 part of antioxidant 4020, 1 part of antioxidant RD, 1 part of vulcanization accelerator CZ and 2 parts of sulfur are mixed and vulcanized in an open mill to obtain NR-V.

Table 1 shows the reaction formula and synthetic rubber information of OAIR, HIR and AIR.

Table 1

Performance Testing:

The model of the spectral analyzer used for the nuclear magnetic resonance hydrogen spectrum test is Bruker AV 400, the test frequency is 400 MHz, and the test solvent is deuterated chloroform.

The instrument used for the mechanical property test was Instron 5966. The test sample was dumbbell-shaped with a size of 35×2×1 mm ³ . The test rates were 12 mm/min, 60 mm/min and 100 mm/min. The test temperature was room temperature. Each sample was tested three times in parallel and the average value was taken as the final data point.

The instrument model used for the dynamic mechanical property test is TA Instrument Q800, and the size of the tested sample is 12mm×3mm×0.5mm. The relaxation test is a room temperature test, with a constant temperature of 5 minutes and a relaxation time of 180 minutes.

The instrument used for TEM test was JEOL JEM-1011, and the samples were prepared by cryosectioning on a Leica EMUC6/FC6 ultrathin microtome. The sample size was 10 mm × 3 mm × 0.5 mm.

The NMR images of OAIR, HIR and AIR obtained in the examples are shown in FIGS. 1 to 3 .

Table 2 shows the mechanical properties data of OAIR-V, HIR-V, AIR-V, NR-V and IR-V.

Table 2

The present invention observes the morphological characteristics of the aggregates of the vulcanized n-octyl allene rubber and the vulcanized commercial isoprene rubber by TEM test, and the results are shown in Figure 4. Compared with IR-V (Figure 4a), OAIR-V (Figure 4b) has denser aggregates and more large-sized aggregates, which are highly cross-linked nanoparticles or microphases formed by cross-linking the unsaturated end groups of the n-octyl allene rubber.

The present invention conducted mechanical property tests and stress relaxation tests on the vulcanized rubber samples, as shown in Figures 5 and 6. The strength and elongation at break of the vulcanized rubber synthesized by the present invention are comparable to those of natural rubber, and the stress relaxation rate is much lower than that of vulcanized natural rubber, and even lower than that of commercial isoprene rubber.

The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims (16)

1. The modified polyisoprene rubber is characterized in that the modified polyisoprene rubber is prepared by vulcanizing polyisoprene containing unsaturated end groups; wherein the polyisoprene containing unsaturated end groups is prepared by the following method one or the following method two: the method comprises the following steps: aging the functional precursor at 40-60 ℃ for 30-100 min under the action of a catalyst; then adding isoprene, and continuously reacting for 8-15 h at the temperature of 40-60 ℃; washing and drying the obtained product to obtain polyisoprene with unsaturated end groups; the molar ratio of the functional precursor to the catalyst is: 20-50: 1, the molar ratio of functional precursor to isoprene is: 1: 50-500;

wherein the functional precursor is selected from at least one of the following substances:

、/>

；

wherein R is ₁ 、R ₂ 、R ₃ 、R ₄ 、R ₅ 、R ₆ 、R ₇ 、R ₈ 、R ₉ 、R ₁₀ 、R ₁₁ 、R ₁₂ And R is ₁₃ Alkyl chains or cyclic structures of 1 to 20 carbon atoms;

the second method is as follows: dissolving polar polyisoprene rubber in a reaction solvent, adding an unsaturated monomer and a condensing agent, and performing condensation reaction for 8-18 h at normal temperature to obtain polyisoprene containing unsaturated end groups; the molar ratio of the polar polyisoprene rubber, the unsaturated monomer and the condensing agent is as follows: polar polyisoprene rubber: unsaturated monomer: condensing agent = 1: 5-15: 5-15;

the unsaturated monomer is selected from at least one of the following substances:

；

wherein R is ₁ 、R ₂ 、R ₃ 、R ₄ 、R ₅ 、R ₆ 、R ₇ 、R ₈ 、R ₉ 、R ₁₀ 、R ₁₁ 、R ₁₂ And R is ₁₃ Alkyl chains or cyclic structures of 1 to 20 carbon atoms;

the polar polyisoprene rubber comprises at least one of the following substances:

；

wherein D is-OH, -COOH or-NH ₂ E is an alkyl chain or a cyclic structure of 1 to 20 carbon atoms; x is more than or equal to 10 and less than or equal to 10000,5, y is more than or equal to 20, m is more than or equal to 5 and less than or equal to 20, n is more than or equal to 100 and less than or equal to 10000,5 and l is more than or equal to 20.

2. The modified polyisoprene rubber of claim 1, wherein in method one, the molar ratio of functional precursor to isoprene is 1: 100-300.

3. The modified polyisoprene rubber according to claim 1 or 2, wherein in the first method, the catalyst is a mixture of substances F, G and H, and the molar ratio of F, G to H is: f: g: h=0.8 to 1.2: 15-25: 1-3; wherein, the substance F is neodecanoic acid neodymium or isopropyl alcohol neodymium or phosphate neodymium, the substance G is triisobutylaluminum or diisobutylaluminum hydride, and the substance H is diisobutylaluminum chloride or dichlorodimethylsilicon.

4. The modified polyisoprene rubber according to claim 1, wherein in the second method, the reaction solvent is tetrahydrofuran, chloroform, methylene chloride, n-hexane or toluene; wherein the ratio of polar polyisoprene rubber to reaction solvent is: 0.5-2 g/100mL.

5. The modified polyisoprene rubber according to claim 1, wherein in said method two, said condensing agent is selected according to the following principles:

when a condensation reaction of carboxyl groups with hydroxyl groups or amino groups occurs, the condensing agent is selected from the group consisting of: dicyclohexylcarbodiimide, N, N ' -diisopropylcarbodiimide, N- (3-dimethylaminopropyl) -N ' -ethylcarbodiimide hydrochloride, 4, 5-dicyanoimidazole, N, N ' -carbonyldiimidazole, N-hydroxysuccinimide, N-hydroxysulfosuccinimide sodium salt, 1-hydroxy-7-azobenzotriazole, 1-hydroxybenzotriazole, 6-chloro-1-hydroxybenzotriazole, O- (7-azobenzotriazole) -N, N, N ', N ' -tetramethylurea hexafluorophosphate, benzotriazole-N, N, N ', N ' -tetramethylurea hexafluorophosphate, O-benzotriazole-N, N, N ', one of N ' -tetramethylurea tetrafluoroborate, 6-chlorobenzotriazole-1, 3-tetramethylurea hexafluorophosphate, O- (1, 2-dihydro-2-oxo-pyridinyl) -1, 3-tetramethylurea tetrafluoroborate, N-ethoxycarbonyl-2-ethoxy-1, 2-dihydroquinoline, bis (2-oxo-3-oxazolidinyl) hypophosphorous acid chloride;

when the hydroxyl group self-condenses, or the hydroxyl and amino groups mutually condense, the condensing agent is selected from the group consisting of: one of diisopropyl azodicarboxylate, diethyl azodicarboxylate, benzotriazol-1-yl-oxy-tripyrrolidinylphosphine hexafluorophosphate, benzotriazol-1-tris (trimethylamino) -hexafluorophosphate, tripyrrolidinylphosphonium bromide hexafluorophosphate;

when the condensation reaction of acyl chloride and amino, hydroxyl or carboxyl occurs, the condensing agent is an organic base.

6. The modified polyisoprene rubber of claim 5, wherein said organic base is one of triethylamine, triethylenediamine, 1, 8-diazabicyclo undec-7-ene, 1, 5-diazabicyclo [4.3.0] non-5-ene, 4-dimethylaminopyridine, pyridine, N-methylmorpholine, tetramethylethylenediamine, tetramethylguanidine, potassium/sodium t-butoxide, N-diisopropylethylamine, diisopropylamine.

7. The modified polyisoprene rubber of claim 1, wherein said vulcanization means: the polyisoprene containing unsaturated end groups is mixed with a vulcanizing agent and an auxiliary agent through double-roll open mill or solution blending, and then vulcanized and molded at high temperature; the vulcanization temperature is 120-190 ℃, and the vulcanization time is 15-120 min.

8. The modified polyisoprene rubber according to claim 7, wherein the vulcanization temperature is 140-150 ℃ and the vulcanization time is 20-40 min.

9. The modified polyisoprene rubber according to claim 6, wherein said vulcanizing agent is at least one of sulfur, tetramethylthiuram disulfide, dipentamethylenethiuram tetrasulfide, 4- (2-benzothiazolyldithio) morpholine, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, tetramethylthiuram disulfide, 4-4 '-dimorpholine disulfide, N-polythiobis (dimethylamine), N' -polythiobis (diethylamine), cycloheptathioimine, dicumyl peroxide, di-t-butyl peroxide, 2, 5-dimethyl-2, 5-bis (t-butylperoxy) hexane, benzoyl peroxide, 2, 4-dichlorobenzoyl peroxide, t-butyl perbenzoate, di-t-butylperoxyisopropyl benzene, 3,5, 7-pentamethyl-1, 2, 4-trioxane, cumyl hydrogen peroxide.

10. The method for producing a modified polyisoprene rubber according to any one of claims 1 to 9, characterized in that the method for producing comprises: and (3) selecting polyisoprene with unsaturated end groups as a raw material, and vulcanizing the polyisoprene with the unsaturated end groups to prepare the modified polyisoprene rubber.

11. A method for increasing the strength of polyisoprene rubber while reducing stress relaxation thereof, the method comprising: firstly, modifying polyisoprene to obtain polyisoprene with unsaturated end groups, and then vulcanizing;

the method for modifying the polyisoprene to obtain the polyisoprene with unsaturated end groups is one of the following two methods:

the method comprises the following steps: aging the functional precursor at 40-60 ℃ for 30-100 min under the action of a catalyst; then adding isoprene, and continuously reacting for 8-15 h at the temperature of 40-60 ℃; washing and drying the obtained product to obtain polyisoprene with unsaturated end groups; the molar ratio of the functional precursor to the catalyst is: 20-50: 1, the molar ratio of functional precursor to isoprene is: 1: 50-500;

wherein the functional precursor is selected from at least one of the following substances:

、/>

；

wherein R is ₁ 、R ₂ 、R ₃ 、R ₄ 、R ₅ 、R ₆ 、R ₇ 、R ₈ 、R ₉ 、R ₁₀ 、R ₁₁ 、R ₁₂ And R is ₁₃ Alkyl chains or cyclic structures of 1 to 20 carbon atoms;

the second method is as follows: dissolving polar polyisoprene rubber in a reaction solvent, adding an unsaturated monomer and a condensing agent, and performing condensation reaction for 8-18 h at normal temperature to obtain polyisoprene containing unsaturated end groups; the molar ratio of the polar polyisoprene rubber, the unsaturated monomer and the condensing agent is as follows: polar polyisoprene rubber: unsaturated monomer: condensing agent = 1: 5-15: 5-15;

the unsaturated monomer is selected from at least one of the following substances:

；

wherein R is ₁ 、R ₂ 、R ₃ 、R ₄ 、R ₅ 、R ₆ 、R ₇ 、R ₈ 、R ₉ 、R ₁₀ 、R ₁₁ 、R ₁₂ And R is ₁₃ Alkyl chains or cyclic structures of 1 to 20 carbon atoms;

the polar polyisoprene rubber comprises at least one of the following substances:

；

wherein D is-OH, -COOH or-NH ₂ E is an alkyl chain or a cyclic structure of 1 to 20 carbon atoms; x is more than or equal to 10 and less than or equal to 10000,5, y is more than or equal to 20, m is more than or equal to 5 and less than or equal to 20, n is more than or equal to 100 and less than or equal to 10000,5 and l is more than or equal to 20.

12. The method for improving the strength of polyisoprene rubber while reducing the stress relaxation thereof according to claim 11,

in the first method, the catalyst is a mixture of substances F, G and H, and the molar ratio of F, G to H is: f: g: h=0.8 to 1.2: 15-25: 1-3; wherein, the substance F is neodecanoic acid neodymium or isopropyl alcohol neodymium or phosphate neodymium, the substance G is triisobutylaluminum or diisobutylaluminum hydride, and the substance H is diisobutylaluminum chloride or dichlorodimethylsilicon.

13. The method for improving the strength of polyisoprene rubber while reducing the stress relaxation thereof according to claim 11,

in the second method, the reaction solvent is tetrahydrofuran, chloroform, methylene dichloride, normal hexane or toluene; wherein the ratio of polar polyisoprene rubber to reaction solvent is: 0.5-2 g/100mL.

14. The method for improving the strength of polyisoprene rubber while reducing the stress relaxation thereof according to claim 11,

in the second method, the condensing agent is selected according to the following principle: when a condensation reaction of carboxyl groups with hydroxyl groups or amino groups occurs, the condensing agent is selected from the group consisting of: dicyclohexylcarbodiimide, N, N ' -diisopropylcarbodiimide, N- (3-dimethylaminopropyl) -N ' -ethylcarbodiimide hydrochloride, 4, 5-dicyanoimidazole, N, N ' -carbonyldiimidazole, N-hydroxysuccinimide, N-hydroxysulfosuccinimide sodium salt, 1-hydroxy-7-azobenzotriazole, 1-hydroxybenzotriazole, 6-chloro-1-hydroxybenzotriazole, O- (7-azobenzotriazole) -N, N, N ', N ' -tetramethylurea hexafluorophosphate, benzotriazole-N, N, N ', N ' -tetramethylurea hexafluorophosphate, O-benzotriazole-N, N, N ', one of N ' -tetramethylurea tetrafluoroborate, 6-chlorobenzotriazole-1, 3-tetramethylurea hexafluorophosphate, O- (1, 2-dihydro-2-oxo-pyridinyl) -1, 3-tetramethylurea tetrafluoroborate, N-ethoxycarbonyl-2-ethoxy-1, 2-dihydroquinoline, bis (2-oxo-3-oxazolidinyl) hypophosphorous acid chloride;

when the hydroxyl group self-condenses, or the hydroxyl and amino groups mutually condense, the condensing agent is selected from the group consisting of: one of diisopropyl azodicarboxylate, diethyl azodicarboxylate, benzotriazol-1-yl-oxy-tripyrrolidinylphosphine hexafluorophosphate, benzotriazol-1-tris (trimethylamino) -hexafluorophosphate, tripyrrolidinylphosphonium bromide hexafluorophosphate; when the condensation reaction of acyl chloride and amino, hydroxyl or carboxyl occurs, the condensing agent is an organic base.

15. The method for improving the strength and reducing the stress relaxation of polyisoprene rubber according to claim 14, wherein the organic base is one of triethylamine, triethylenediamine, 1, 8-diazabicyclo undec-7-ene, 1, 5-diazabicyclo [4.3.0] non-5-ene, 4-dimethylaminopyridine, pyridine, N-methylmorpholine, tetramethylethylenediamine, tetramethylguanidine, potassium/sodium t-butoxide, N-diisopropylethylamine and diisopropylamine.

16. The method for improving the strength of a polyisoprene rubber while reducing the stress relaxation thereof according to claim 11, wherein in the second method, the molar ratio of the polar polyisoprene rubber, the unsaturated monomer and the condensing agent is: 1: 8-12: 8-12.

Images