Dihydroxy-terminated polyisoprene liquid rubber as well as preparation method and application thereof

Abstract

The invention relates to dihydroxy-terminated polyisoprene liquid rubber which is obtained by taking a dihydroxy-terminated trithioester compound as a chain transfer agent through reversible addition-fragmentation chain transfer polymerization of isoprene. The double-hydroxyl-terminated polyisoprene liquid rubber is structurally characterized in that p-xylylene is arranged in the middle of a molecular chain, homo-polyisoprene unsaturated chain segments are arranged on the two sides of the p-xylylene, trithioester groups are arranged on the outer sides of the homo-polyisoprene unsaturated chain segments, and the outer sides of the trithioester groups (namely the two ends of the molecular chain) are terminated by hydroxyl groups. The molecular weight distribution (PDI) of the dihydroxy-terminated polyisoprene liquid rubber can be controlled to be 1.7 or below, a polymer is easy to separate, in addition, a solvent and a monomer used in the preparation process can be recycled, so that the waste of resources is reduced, the overall production cost is reduced, and through a continuous flow synthesis method, the production cost is reduced. And possibility is provided for future industrial production.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials, and more particularly to a double-terminal hydroxyl polyisoprene liquid rubber and a preparation method and application thereof. Background Art

[0002] Liquid rubber has a low molecular weight, good fluidity at room temperature or under heating, and is easy to process and shape. Common hydroxyl-terminated liquid rubbers include hydroxyl-terminated liquid butadiene rubber, hydroxyl-terminated liquid isoprene rubber, hydroxyl-terminated liquid nitrile rubber and other diene liquid rubbers, which are mainly used in adhesives, solid rubber reactive plasticizers, resin toughening agents, coatings, synthetic polyurethanes, etc.

[0003] Hydroxyl-terminated liquid rubber is mainly obtained by anionic polymerization, free radical polymerization and coordination polymerization. Chinese patent CN116496433A provides a modified initiator for preparing dihydroxy-terminated liquid diene rubber by anionic polymerization. Anionic polymerization can prepare products with a very narrow molecular weight distribution, but it has high requirements on the purity of the raw materials and process accuracy.

[0004] Chinese patent CN114195938A discloses a method for preparing a high-functionality hydroxyl-terminated liquid rubber, which is obtained by introducing a polymer chain segment with a hydroxyl functional group into a polymer chain segment, so the product has high functionality but needs to be obtained through multiple steps of reaction.

[0005] Chinese patent CN114656583A discloses a method for preparing end-functionalized liquid polydiene rubber by coordination polymerization followed by grafting, and the molecular weight distribution of the coordination polymerization product is relatively wide. Summary of the invention

[0006] In order to solve the technical problems existing in the prior art, the present invention provides a dihydroxyl-terminated polyisoprene liquid rubber and a preparation method and application thereof. The dihydroxyl-terminated polyisoprene liquid rubber of the present invention has a narrow polymer molecular weight distribution, which solves the problem that the molecular weight distribution of free radical polymerization in the prior art is difficult to control; in addition, the dihydroxyl-terminated polyisoprene liquid rubber of the present invention still retains polymerization activity, and other monomers can be added thereto to continue polymerization to prepare a block copolymer.

[0007] One of the purposes of the present invention is to provide a double-terminal hydroxyl polyisoprene liquid rubber, the structure of the double-terminal hydroxyl polyisoprene liquid rubber is shown in the following formula (I):

[0008]

[0009] In formula (I), R is -CH 2 OH, -CH 2 CH 2OH, -CH(CH 3 )OH or -CH(OH)CH 2 OH; X=1-700, Y=1-100, Z=1-100; preferably, X=27-661, Y=1-32, Z=2-44.

[0010] As can be seen from formula (I), the double-terminal hydroxyl polyisoprene liquid rubber of the present invention has a p-xylylene in the middle of the molecular chain, homopolyisoprene unsaturated segments on both sides of the p-xylylene, trithioester groups on the outside of the homopolyisoprene unsaturated segments, and hydroxyl groups on the outside of the trithioester groups (i.e., both ends of the molecular chain). The homopolyisoprene unsaturated segments include three types of polyisoprenes, which are 3,4-polyisoprene, 1,2-polyisoprene and 1,4-polyisoprene from the middle of the chain to the outside of the chain.

[0011] In a preferred embodiment of the present invention, the number average molecular weight of the dihydroxy-terminated polyisoprene liquid rubber is 1000-50000; the molecular weight distribution of the dihydroxy-terminated polyisoprene liquid rubber is less than 1.7, preferably 1.4-1.6.

[0012] In a preferred embodiment of the present invention, in formula (I), X is 89-92% of the sum of X, Y and Z, that is, in the homopolyisoprene unsaturated segment containing three types of polyisoprenes, the molar ratio of 1,4-polyisoprene is 89-92%.

[0013] The second object of the present invention is to provide a method for preparing the dihydroxy-terminated polyisoprene liquid rubber according to the first object of the present invention, the method comprising:

[0014] Isoprene, a chain transfer agent, an initiator and a solvent are mixed, heated and pressurized to react, so as to obtain the dihydroxy-terminated polyisoprene liquid rubber; wherein the chain transfer agent is a dihydroxy-terminated trithioester chain transfer agent.

[0015] The following technical solutions can be used:

[0016] The present invention uses a trithioester compound with double-terminal hydroxyl groups as a chain transfer agent, and obtains double-terminal hydroxyl polyisoprene liquid rubber through reversible addition-fragmentation chain transfer polymerization of isoprene. In the preparation method of the double-terminal hydroxyl polyisoprene liquid rubber of the present invention, the polymerization process is carried out in a stainless steel high-temperature and high-pressure reactor equipped with a magnetic stirrer. Isoprene, a chain transfer agent, an initiator, and a solvent are added to the reactor, and after freezing and pumping, the reactor is pressurized and sealed under nitrogen, and reacted under stirring. After the polymerization reaction is completed, the reaction liquid is dripped into a methanol solvent, and the mixture is centrifuged to obtain a solid product, which is dried in a high-temperature vacuum oven to obtain a double-terminal hydroxyl polyisoprene liquid rubber.

[0017] In a preferred embodiment of the present invention, the structure of the dihydroxyl-terminated trithioester chain transfer agent is as shown in the following formula (II):

[0018]

[0019] In formula (II), R is -CH 2 OH, -CH 2 CH 2 OH, -CH(CH 3 )OH or -CH(OH)CH 2 OH. That is, the dihydroxyl-terminated trithioester chain transfer agent is

[0020]

[0021] Any one of .

[0022] When the dihydroxyl-terminated trithioester chain transfer agent is When the prepared double-terminated hydroxyl polyisoprene liquid rubber is

[0023]

[0024] When the dihydroxyl-terminated trithioester chain transfer agent is When the prepared double-terminated hydroxyl polyisoprene liquid rubber is

[0025]

[0026] When the dihydroxyl-terminated trithioester chain transfer agent is When the prepared double-terminated hydroxyl polyisoprene liquid rubber is

[0027]

[0028] When the dihydroxyl-terminated trithioester chain transfer agent is When the prepared double-terminated hydroxyl polyisoprene liquid rubber is

[0029]

[0030] Technicians can select appropriate dihydroxyl-terminated trithioester chain transfer agents according to actual needs.

[0031] In a preferred embodiment of the present invention, the initiator includes an azo initiator and / or an organic peroxide initiator. Preferably, the azo initiator includes azobisisobutyronitrile and / or azobisisoheptylnitrile; the organic peroxide initiator includes at least one of benzoyl peroxide, acetophenone peroxide, and di-tert-butyl peroxide. The technician can select a suitable initiator according to actual needs. In another preferred embodiment of the present invention, the solvent includes at least one of dioxane, tetrahydrofuran, n-hexane, and cyclohexane. The technician can select a suitable solvent according to actual needs.

[0032] In a preferred embodiment of the present invention, the molar ratio of the isoprene, the chain transfer agent, the initiator, and the solvent is 100-2000: 1: 0.2-0.5: 100-500, preferably 500-1000: 1: 0.3-0.5: 200-400. The technicians can select the appropriate molar ratio according to actual needs.

[0033] In a preferred embodiment of the present invention, the reaction time is 2 to 24 hours, the reaction temperature is 65 to 130° C., and the reaction pressure is 0.5 to 1 MPa. The technicians can select appropriate reaction time, reaction temperature and reaction pressure according to actual needs.

[0034] In the above method for preparing dihydroxy-terminated polyisoprene liquid rubber, dihydroxy-terminated polyisoprene liquid rubber with different molecular weights can be obtained by changing the reaction time or changing the feed ratio of isoprene, initiator and chain transfer agent.

[0035] The third object of the present invention is to provide the use of the double-terminal hydroxyl polyisoprene liquid rubber described in the first object of the present invention or the double-terminal hydroxyl polyisoprene liquid rubber obtained by the preparation method described in the second object of the present invention in adhesives, plasticizers, toughening agents, coatings, and synthetic polyurethanes.

[0036] Compared with the prior art, the present invention has the following positive effects:

[0037] The bihydroxyl-terminated polyisoprene liquid rubber of the present invention has a molecular weight distribution (PDI) that can be controlled below 1.7, and the polymer is easy to separate, which solves the problem that the molecular weight distribution of free radical polymerization in the prior art is difficult to control; and the bihydroxyl-terminated polyisoprene liquid rubber of the present invention still retains polymerization activity, and other monomers can be added thereto to continue polymerization to prepare a block copolymer. In addition, the process of preparing the bihydroxyl-terminated polyisoprene liquid rubber has a mild reaction and is easy to operate, and the solvent and monomer used can be recycled and reused, which not only reduces the waste of resources, but also helps to reduce the overall production cost; more importantly, the preparation of the bihydroxyl-terminated polyisoprene liquid rubber adopts a continuous flow synthesis method, which is more conducive to future industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is the H NMR spectrum of the dihydroxy-terminated polyisoprene liquid rubber obtained in Example 1 of the present invention;

[0039] Figure 2 This is the H NMR spectrum of the dihydroxy-terminated polyisoprene liquid rubber obtained in Example 2 of the present invention;

[0040] Figure 3 This is the H NMR spectrum of the dihydroxy-terminated polyisoprene liquid rubber obtained in Example 3 of the present invention;

[0041] Figure 4 This is the H NMR spectrum of the dihydroxy-terminated polyisoprene liquid rubber obtained in Example 4 of the present invention;

[0042] Figure 5 This is the H NMR spectrum of the dihydroxy-terminated polyisoprene liquid rubber obtained in Example 5 of the present invention;

[0043] Figure 6 This is the H NMR spectrum of the dihydroxy-terminated polyisoprene liquid rubber obtained in Example 6 of the present invention;

[0044] Figure 7 This is the H NMR spectrum of the dihydroxy-terminated polyisoprene liquid rubber obtained in Example 7 of the present invention;

[0045] Figure 8 The polymerization kinetic curves of the dihydroxy-terminated polyisoprene liquid rubber prepared in Examples 3 to 7 of the present invention. DETAILED DESCRIPTION

[0046] The present invention is described in detail below in conjunction with specific drawings and embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the content of the present invention still fall within the scope of protection of the present invention.

[0047] In the present invention, DTBP is di-tert-butyl peroxide.

[0048] The raw materials used in the examples are all conventional commercially available raw materials, and the instruments used are also conventional commercially available instruments.

[0049] Example 1

[0050] This example was carried out in a 50 mL polymerization tube equipped with a magnetic stirrer. Take isoprene (3.4 g, 50 mmol), chain transfer agent (0.205g, 0.5mmol), di-tert-butyl peroxide (DTBP, 0.024g, 0.16mmol) were added to the reactor. Dioxane (10mL, 0.117mol) was taken as a solvent and added to the reactor. The top space of the reactor was flushed with nitrogen three times. The solution was then degassed by a single freeze-pump-thaw cycle, and the reactor was pressurized and sealed under nitrogen, and the reaction pressure was 0.5MPa. The reactor was reacted for 16 hours under stirring (500rpm) and at 125°C. After the polymerization reaction was completed, the reaction solution was dripped into the methanol solvent, and the mixture was treated by centrifugation. The solid product obtained was dried in a high-temperature vacuum oven (45°C, 0.7kPa) for 48 hours to obtain a double-terminal hydroxyl polyisoprene liquid rubber. The number average molecular weight of the double-terminal hydroxyl polyisoprene liquid rubber was measured by gel permeation chromatography (GPC) to be 2865g / mol, and the molecular weight distribution was 1.54. By 1 H NMR (such as Figure 1 ) It can be confirmed that the structural formula of the double-terminal hydroxyl polyisoprene liquid rubber is

[0051]

[0052] Among them, X=31-33, Y=1-2, Z=2-3.

[0053] Example 2

[0054] This example was carried out in a 50 mL polymerization tube equipped with a magnetic stirrer. Isoprene (6.8 g, 100 mmol), chain transfer agent (0.205g, 0.5mmol), di-tert-butyl peroxide (DTBP, 0.024g, 0.16mmol) were added to the reactor. Dioxane (10mL, 0.117mol) was taken as the solvent and added to the reactor. The top space of the reactor was flushed with nitrogen three times, and then the solution was degassed by a single freeze-pump-thaw cycle, and the reactor was pressurized and sealed under nitrogen. The reaction pressure was 0.5MPa. The reactor was reacted for 16 hours under stirring (500rpm) and at 125°C. After the polymerization reaction was completed, the reaction solution was dripped into the methanol solvent, and the mixture was treated by centrifugation. The solid product obtained was dried in a high-temperature vacuum oven (45°C, 0.7kPa) for 48 hours to obtain a double-terminal hydroxyl polyisoprene liquid rubber. The number average molecular weight of the double-terminal hydroxyl polyisoprene liquid rubber was measured by gel permeation chromatography (GPC) to be 5982g / mol, and the molecular weight distribution was 1.48. By 1 H NMR (such as Figure 2 ) It can be confirmed that the structural formula of the double-terminal hydroxyl polyisoprene liquid rubber is

[0055]

[0056] Among them, X=63-65, Y=2-5, Z=4-6.

[0057] Example 3

[0058] Take isoprene (34 g, 500 mmol), chain transfer agent (0.41g, 1mmol), di-tert-butyl peroxide (DTBP, 0.045g, 0.3mmol) were added to the reactor. Dioxane (17.1mL, 0.2mol) was taken as the solvent and added to the reactor. The top space of the reactor was flushed with nitrogen three times. The solution was then degassed by a single freeze-pump-thaw cycle, and the reactor was pressurized and sealed under nitrogen, and the reaction pressure was 0.5MPa. The reactor was reacted for 2 hours under stirring (500rpm) and at 125°C. After the polymerization reaction was completed, the reaction solution was dripped into the methanol solvent, and the mixture was treated by centrifugation. The solid product obtained was dried in a high-temperature vacuum oven (45°C, 0.7kPa) for 48 hours to obtain a double-terminated hydroxyl polyisoprene liquid rubber. By 1 H NMR (such as Figure 3 ) It can be confirmed that the structural formula of the double-terminal hydroxyl polyisoprene liquid rubber is

[0059]

[0060] Among them, X=74-76, Y=2-4, Z=4-6.

[0061] Example 4

[0062] This example is basically the same as Example 3, except that the reactor was stirred (500 rpm) and reacted at 125° C. for 4 hours. 1 H NMR (such as Figure 4 ) It can be confirmed that the structural formula of the double-terminal hydroxyl polyisoprene liquid rubber is

[0063]

[0064] Among them, X=78-80, Y=3-5, Z=4-6.

[0065] Example 5

[0066] This example is basically the same as Example 3, except that the reactor was stirred (500 rpm) and reacted at 125° C. for 6 hours. 1 H NMR (such as Figure 5 ) It can be confirmed that the structural formula of the double-terminal hydroxyl polyisoprene liquid rubber is

[0067]

[0068] Among them, X=88-90, Y=4-6, Z=5-7.

[0069] Example 6

[0070] This example is basically the same as Example 3, except that the reactor was stirred (500 rpm) and reacted at 125° C. for 10 hours. 1 H NMR (such as Figure 6 ) It can be confirmed that the structural formula of the double-terminal hydroxyl polyisoprene liquid rubber is

[0071]

[0072] Among them, X=107-109, Y=4-6, Z=6-8.

[0073] Example 7

[0074] This example is basically the same as Example 3, except that the reactor was stirred (500 rpm) and reacted at 125° C. for 12 hours. 1 H NMR (such as Figure 7 ) It can be confirmed that the structural formula of the double-terminal hydroxyl polyisoprene liquid rubber is

[0075]

[0076] Among them, X=114=116, Y=5-7, Z=7-9.

[0077] The number average molecular weight and molecular weight distribution of the dihydroxy-terminated polyisoprene liquid rubber obtained in Examples 3 to 7 were determined by gel permeation chromatography (GPC) and plotted as Figure 8 Reaction kinetics curve. Figure 8 In the figure, the X-axis is the reaction time, the left Y-axis is the number average molecular weight, and the right Y-axis is the molecular weight distribution. Each example has two point values, the square is the number average molecular weight of the example, and the triangle is the molecular weight distribution of the example. Figure 8 It can be seen that the number average molecular weight of the dihydroxy-terminated polyisoprene liquid rubber in Examples 3 to 7 increases linearly with the increase of reaction time, indicating that when the molar ratio of the isoprene, the chain transfer agent, the initiator, and the solvent is the same, the degree of polymerization of the obtained dihydroxy-terminated polyisoprene liquid rubber increases linearly with the increase of reaction time, that is, the active controllable polymerization of the dihydroxy-terminated polyisoprene liquid rubber can be achieved by regulating the reaction time. In addition, the molecular weight distribution of the dihydroxy-terminated polyisoprene liquid rubber of the present invention can also be controlled within a certain range.

Claims

1. A double-terminal hydroxyl polyisoprene liquid rubber, characterized in that: The structure of the dihydroxy-terminated polyisoprene liquid rubber is shown in the following formula (I): In formula (I), R is -CH2OH, -CH2CH2OH, -CH(CH3)OH or -CH(OH)CH2OH; X=1-700, Y=1-100, Z=1-100; preferably, X=27-661, Y=1-32, Z=2-44.

2. The double-terminal hydroxyl polyisoprene liquid rubber according to claim 1, characterized in that: The number average molecular weight of the dihydroxy-terminated polyisoprene liquid rubber is 1000 to 50000; and / or The molecular weight distribution of the dihydroxy-terminated polyisoprene liquid rubber is less than 1.7, preferably 1.4 to 1.

6.

3. The double-terminal hydroxyl polyisoprene liquid rubber according to claim 1, characterized in that: In formula (I), X is 89-92% of the sum of X, Y and Z.

4. A method for preparing a dihydroxy-terminated polyisoprene liquid rubber as claimed in any one of claims 1 to 3, characterized in that The method comprises: Isoprene, a chain transfer agent, an initiator and a solvent are mixed, heated and pressurized to react, so as to obtain the dihydroxy-terminated polyisoprene liquid rubber; wherein the chain transfer agent is a dihydroxy-terminated trithioester chain transfer agent.

5. The method according to claim 4, characterized in that: The structure of the dihydroxyl-terminated trithioester chain transfer agent is shown in the following formula (II): In formula (II), R is -CH2OH, -CH2CH2OH, -CH(CH3)OH or -CH(OH)CH2OH.

6. The method according to claim 4, characterized in that: The initiator includes an azo initiator and / or an organic peroxide initiator; Preferably, The azo initiator includes azobisisobutyronitrile and / or azobisisoheptanenitrile; The organic peroxide initiator includes at least one of benzoyl peroxide, acetophenone peroxide, and di-tert-butyl peroxide.

7. The method according to claim 4, characterized in that: The solvent includes at least one of dioxane, tetrahydrofuran, n-hexane and cyclohexane.

8. The method according to claim 4, characterized in that: The molar ratio of the isoprene, the chain transfer agent, the initiator and the solvent is 100-2000:1:0.2-0.5:100-500; preferably 500-1000:1:0.3-0.5:200-400.

9. The method according to claim 4, characterized in that: The reaction time is 2 to 24 hours; and / or The reaction temperature is 65 to 130°C; and / or The reaction pressure is 0.5~1Mpa.

10. Use of the dihydroxy-terminated polyisoprene liquid rubber as claimed in any one of claims 1 to 3 or the dihydroxy-terminated polyisoprene liquid rubber obtained by the preparation method as claimed in any one of claims 4 to 9 in adhesives, plasticizers, toughening agents, coatings, and synthetic polyurethanes.

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