Liquid polybutadiene, process for its preparation and use

Abstract

The application discloses a kind of liquid polybutadiene and its preparation method and application, belong to high polymer material technical field.The liquid polybutadiene includes two different molecular chains of end structure;Wherein, one end of molecular chain is C1-C 10 Linear or branched alkyl, the other end is methyl end or vinyl end;The proportion of the molecular chain of vinyl end is ≥50%;The total content of vinyl unit in the molecular chain of the liquid polybutadiene is ≥70%;The vinyl unit is 1,2-vinyl structural unit.The molecular structure of the liquid polybutadiene is regular, and the reaction activity is uniform, can form uniform crosslinking network in curing process, avoid producing micro-bubble, crystallization and other defects, so as to ensure that thermosetting plastic has excellent transparency, while having excellent mechanical properties and good flexibility, aging resistance and certain stability, can be widely used in optical lens, electronic packaging materials, transparent composite materials and other high-end fields.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a liquid polybutadiene, its preparation method, and its applications. Background Technology

[0002] Liquid polybutadiene is a liquid polymer compound with an unsaturated double bond structure. Due to its good flexibility, low-temperature resistance, and chemical stability, it is widely used in adhesives, coatings, composite materials, and rubber modification. With the increasing demand for transparent polymer materials in industries such as optics, electronics, and automobiles, higher requirements are being placed on the structural controllability and application performance of liquid polybutadiene.

[0003] In existing technologies, the molecular structure of liquid polybutadiene (such as molecular weight, vinyl unit content, and end-group structure) is difficult to precisely control simultaneously, resulting in the inability of cured products to meet the requirements of high-end applications in terms of transparency and mechanical properties. For example, conventional liquid polybutadiene has a low vinyl unit content and a disordered end-group capping structure, leading to uneven curing reactivity. The resulting thermosetting plastics are prone to problems such as turbidity and yellowing, and the transparency is difficult to reach above 85%.

[0004] Regarding synthesis methods, existing initiation systems and reaction conditions struggle to balance polymerization efficiency and product purity. Some synthesis processes utilize non-polar solvents, resulting in low vinyl unit content. While some processes can increase vinyl content, post-reaction impurity removal is difficult, leading to insufficient product transparency and failing to meet the requirements for subsequent transparent material preparation. Furthermore, existing liquid polybutadiene, when used to prepare thermosetting plastics, suffers from drawbacks such as excessively high curing temperatures, slow curing speeds, or poor transparency and mechanical properties after curing, limiting its application in high-end transparent materials.

[0005] Therefore, the research and development of a liquid polybutadiene with controllable molecular structure, high purity, and efficient preparation of highly transparent thermosetting plastics, as well as its synthesis method, has become an urgent technical problem to be solved in this field. Summary of the Invention

[0006] In view of this, the technical problem to be solved by the present invention is to provide a liquid polybutadiene, its preparation method, and its application. The liquid polybutadiene has a unique structure, and its use in preparing thermosetting plastics can achieve both excellent transparency and mechanical properties.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] This invention provides a liquid polybutadiene, the molecular chain of which has a C1-C structure at one end. 10 A straight-chain or branched alkyl group, with one end capped;

[0009] The vinyl unit content in the end-capping structure is ≥50%; preferably 60%-90%, more preferably 70%-85%.

[0010] The liquid polybutadiene has a vinyl unit content of ≥70% in its molecular chain; preferably 75%-95%; more preferably 80%-90%.

[0011] The vinyl unit is a 1,2-vinyl structural unit.

[0012] The liquid polybutadiene of this invention has a controllable molecular structure, high vinyl content, and regular end group structure.

[0013] Preferably, the number-average molecular weight of the liquid polybutadiene is 600-20000; more preferably 1000-15000; and even more preferably 2000-10000.

[0014] Preferably, the viscosity of the liquid polybutadiene at 25°C is 500-100000 mPa·s.

[0015] The liquid polybutadiene described in this invention exhibits excellent reactivity and structural regularity through the combined effects of its molecular weight, vinyl unit content, and end-group structure.

[0016] The design of the end-group structure in the liquid polybutadiene of this invention avoids the defect of disordered end groups in the prior art. By controlling the content of molecular chains with different end-capping structures, the application performance of the product is further optimized.

[0017] Preferably, in this invention, one end of the molecular chain of the liquid polybutadiene is a C1-C4 straight-chain or branched alkyl group.

[0018] The C1-C4 straight-chain or branched alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, etc.

[0019] The present invention is more preferably n-butyl.

[0020] The present invention also provides a method for preparing the above-mentioned liquid polybutadiene, comprising the following steps:

[0021] The liquid polybutadiene was obtained by mixing and reacting 1,3-butadiene monomer, polar solvent and initiator under an inert atmosphere.

[0022] The initiator is selected from a mixture of alkyl lithium and diethylmagnesium, or a mixture of alkyl lithium and tetrabutyltin; the alkyl lithium is selected from one or more of n-butyllithium, isobutyllithium, and sec-butyllithium.

[0023] The initiator is preferably a mixture of n-butyllithium and diethylmagnesium, or a mixture of n-butyllithium and tetrabutyltin.

[0024] The molar ratio of n-butyllithium to diethylmagnesium in the mixture of n-butyllithium and diethylmagnesium is preferably 1:(0.1-0.5); more preferably 1:(0.3-0.5).

[0025] The above molar ratio range can promote the effective regulation of polymerization reaction efficiency by the composite initiator, increase the content of vinyl units, and accurately control the end group structure, thereby generating liquid polybutadiene with the above content requirements.

[0026] The polar solvent is selected from tetrahydrofuran and / or tetramethylethylenediamine; preferably a mixture of tetrahydrofuran and tetramethylethylenediamine.

[0027] The preferred volume ratio of tetrahydrofuran to tetramethylethylenediamine in the mixed solvent is (5-10):1.

[0028] The purity of the tetrahydrofuran or tetramethylethylenediamine is ≥99.8%.

[0029] The preparation method described in this invention selects a suitable polar solvent to solvate the active center ion pairs, thereby improving the reactivity, promoting the formation of 1,2-vinyl structures, avoiding the over-generation of 1,4-vinyl structures, and providing a suitable reaction environment for the regulation of end-group structures.

[0030] The above preparation method achieves the preparation of the unique and novel liquid polybutadiene through precise control of the solvent and initiator.

[0031] In the above preparation method, the reaction is an anionic polymerization reaction. Preferably, the content of the 1,3-butadiene monomer in the reaction system is 10 wt%-40 wt%; more preferably, it is 20 wt%-30 wt%.

[0032] Preferably, the molar ratio of the 1,3-butadiene monomer to the initiator is (10-1000):1; more preferably, it is (120-500):1.

[0033] The purity of the 1,3-butadiene monomer is ≥99.5%.

[0034] Preferably, the reaction temperature is 0℃-50℃; more preferably, it is 20℃-30℃.

[0035] Preferably, the reaction pressure is -0.1 to 0.5 MPa; more preferably, it is 0.2 to 0.4 MPa.

[0036] The reaction time is preferably 2-8 h; more preferably 3-6 h.

[0037] The stirring rate of the reaction is 150-250 r / min.

[0038] The above anionic polymerization reaction was carried out under an inert atmosphere.

[0039] The inert atmosphere includes, but is not limited to, nitrogen, argon, etc.

[0040] The reaction is preferably carried out in an anhydrous and oxygen-free environment.

[0041] The present invention does not impose any special limitation on the equipment used in the reaction of the above preparation method; any polymerization reaction equipment known to those skilled in the art is acceptable.

[0042] In some specific embodiments of the present invention, a reaction vessel is preferably used.

[0043] The stirring rate of the reactants in the reactor is preferably 100-300 r / min.

[0044] The reaction time is preferably 2-8 h.

[0045] The pressure of the inert gas in the reactor is preferably 0.05-0.1 MPa.

[0046] The inert gas in the reactor is replaced 2-3 times.

[0047] Preferably, the preparation method of the present invention further includes sequential reaction termination and filtration post-treatment;

[0048] Preferably, the reaction terminator is selected from methanol or ethanol;

[0049] The terminator needs to be added in excess to ensure complete termination of the reaction.

[0050] The molar amount of the terminator is preferably 0.5%-2% of the 1,3-butadiene monomer; more preferably 0.8%-1.5%.

[0051] Preferably, the filtration medium is selected from diatomaceous earth or alumina.

[0052] The amount of the filter medium used is 5%-15% of the total mass of the reaction system; more preferably 8%-12%.

[0053] The preferred filtration temperature is 20℃-40℃, more preferably 25℃-35℃.

[0054] The pressure of the filter is preferably 0.1-0.3 MPa; more preferably 0.15-0.25 MPa.

[0055] The filter medium must be dried before use.

[0056] The drying temperature is 100℃-120℃.

[0057] The drying process takes 2-4 hours.

[0058] The purpose of the filtration is to remove impurities and residual initiators from the reaction system, thereby obtaining liquid polybutadiene with high purity.

[0059] The filtration process also includes solvent removal.

[0060] The solvent removal method described in this invention is not particularly limited and can be any method known to those skilled in the art.

[0061] In some specific embodiments of the present invention, the solvent removal process includes removing the solvent by vacuum distillation of the filtered clarified filtrate to obtain colorless and transparent liquid polybutadiene.

[0062] The preferred temperature for vacuum distillation is 60℃-120℃; more preferably 70℃-100℃.

[0063] The pressure of the vacuum distillation is preferably 0.01-0.05 MPa; more preferably 0.02-0.04 MPa.

[0064] The solvent removal time is preferably 1-3 h; more preferably 1.5-2.5 h.

[0065] The purity of the product (liquid polybutadiene) after solvent removal is ≥99%. This invention effectively removes impurities from the anionic polymerization reaction through the above-mentioned reaction termination, filtration, and solvent removal processes, resulting in a high purity of liquid polybutadiene, exceeding 99%.

[0066] This invention achieves precise control of the molecular structure of liquid polybutadiene through the above preparation method, solving the problems of uneven product structure and low purity in existing processes.

[0067] The above preparation method has mild reaction conditions, which can effectively control the polymerization process, avoid excessively wide molecular weight distribution, and ensure the uniformity of product structure.

[0068] The present invention also provides a thermosetting plastic, which is obtained by curing the liquid polybutadiene described above or the liquid polybutadiene prepared by the above preparation method.

[0069] Preferably, the transparency of the thermosetting plastic is ≥90%; more preferably, it is 90%-95%.

[0070] Preferably, the tensile strength of the thermosetting plastic is ≥15 MPa; more preferably, it is 15-20 MPa.

[0071] Preferably, the impact strength of the thermosetting plastic is ≥25 kJ / m. 2More preferably 25-30 kJ / m 2 .

[0072] The high vinyl unit content in the liquid polybutadiene of this invention can increase the molecular chain crosslinking density, C1-C 10 The straight-chain or branched alkyl structure can improve molecular compatibility and avoid phase separation during subsequent curing. The high content of vinyl end-capped structure can ensure the uniformity of the curing reaction and avoid the generation of micropores during curing. The three work together to improve the transparency and mechanical properties of the cured product.

[0073] This invention improves curing efficiency by controlling curing conditions, thereby enhancing the performance of thermosetting plastics and significantly improving their transparency and mechanical properties.

[0074] Preferably, the curing temperature is 270℃-320℃; more preferably, it is 280℃-300℃.

[0075] Preferably, the curing heating rate is 5-10℃ / min; more preferably, it is 6-8℃ / min.

[0076] The curing time is preferably 0.5-3 h; more preferably 1-2 h.

[0077] Preferably, the curing process further includes the addition of a peroxide curing agent.

[0078] Preferably, the peroxide curing agent is selected from one or more of benzoyl peroxide, di-tert-butyl peroxide, and di-tert-pentyl peroxide; more preferably, it is benzoyl peroxide, or a mixture of benzoyl peroxide and di-tert-butyl peroxide.

[0079] In the mixture of benzoyl oxide and di-tert-butyl peroxide, the mass ratio of benzoyl oxide to di-tert-butyl peroxide is 1:(0.5-2).

[0080] The di-tert-butyl peroxide is in powder form with a purity of ≥98%.

[0081] Preferably, the amount of the peroxide curing agent added is 0.1wt%-2wt% of the liquid polybutadiene; more preferably, it is 0.5wt%-1.5wt%.

[0082] Preferably, the curing temperature is 80℃-150℃; more preferably, it is 100℃-130℃.

[0083] Preferably, the curing heating rate is 3-8℃ / min; more preferably, it is 4-6℃ / min.

[0084] The curing time is preferably 2-4 h; more preferably 1-5 h.

[0085] After the above curing process, the thermosetting plastic described in this invention can be obtained by cooling it to room temperature.

[0086] Compared with the prior art, the liquid polybutadiene provided by the present invention comprises molecular chains with two different end-capping structures; wherein, one end of the molecular chain is C1-C 10 The liquid polybutadiene comprises straight-chain or branched alkyl groups, with one end capped by methyl or vinyl groups; the vinyl-capped molecular chain accounts for ≥50%; the total content of vinyl units in the molecular chain of the liquid polybutadiene is ≥70%; the vinyl units are 1,2-vinyl structural units. The liquid polybutadiene has a regular molecular structure and uniform reactivity, forming a uniform cross-linked network during curing, avoiding defects such as microbubbles and crystallization, thus ensuring excellent transparency of the thermosetting plastic. It also possesses excellent mechanical properties, good flexibility, aging resistance, and a certain degree of stability, making it widely applicable in high-end fields such as optical lenses, electronic packaging materials, and transparent composite materials. Detailed Implementation

[0087] To further illustrate the present invention, the liquid polybutadiene, its preparation method, and its applications provided by the present invention are described in detail below with reference to embodiments. All reactants or solvents described below are commercially available products.

[0088] The molecular weight determination below was performed using gel permeation chromatography (GPC). The test conditions were: tetrahydrofuran as the mobile phase, flow rate 1.0 mL / min, column temperature 30 °C, and polystyrene as the standard for calibration.

[0089] The method for testing the total content of vinyl units in the molecular chain of the following liquid polybutadiene is ¹H-NMR, wherein the test solvent is deuterated chloroform and the test temperature is 25℃.

[0090] The method for testing the vinyl end-capping ratio (i.e., the content of vinyl-terminated molecular chains) in the following end-capped structures is ¹H-NMR, with deuterated chloroform as the test solvent and 25°C as the test temperature.

[0091] The following viscosities were measured using a rotational viscometer.

[0092] The curing process described below is performed using a mold, wherein the mold temperature is the same as the curing temperature, and the molding pressure is 0.1-0.3 MPa.

[0093] The transparency was measured using a transmittance meter, referring to GB / T 2410-2008 "Determination of transmittance and haze of transparent plastics", where the test wavelength was 550 nm and the sample thickness was 2 mm.

[0094] The tensile strengths described below were determined using a universal testing machine, referring to GB / T 1040.1-2025 Determination of Tensile Properties of Plastics, with a test rate of 5 mm / min.

[0095] The impact strengths described below were determined using a simply supported beam impact testing machine without notches.

[0096] The Shore hardness test described below refers to GB / T 2411-2008 Plastics and Hard Rubber, which uses a hardness tester to determine the indentation hardness (i.e., Shore hardness).

[0097] The liquid polybutadiene prepared in Examples 1 and 2 and Comparative Example 1 respectively all contain molecular chains with the following two end-capped structures:

[0098] Formula 1;

[0099] Formula 2;

[0100] Where m and n are the degrees of polymerization, and R is C1-C2. 10 The straight-chain or branched alkyl group, specifically n-butyl in Examples 1 and 2.

[0101] Example 1

[0102] Preparation of liquid polybutadiene:

[0103] 1) Polymerization reaction: Add 1,3-butadiene monomer (20 wt% of the total reaction system), a mixed solvent of tetrahydrofuran and tetramethylethylenediamine (volume ratio 8:1) to a dry polymerization reactor, stir evenly, add initiator (a mixture of n-butyllithium and diethylmagnesium, molar ratio 1:0.3), the molar ratio of monomer to initiator is 125:1; control the reaction temperature at 25℃, the reaction pressure at 0.3MPa, and the reaction time at 4h to obtain the polymerization reaction solution.

[0104] 2) Termination and filtration: Add methanol (1% of the monomer molar amount) to the polymerization reaction solution as a terminator and stir for 10 min to terminate the reaction; then add diatomaceous earth (10% of the total mass of the reaction system) and filter at 30℃ and 0.2MPa to remove impurities.

[0105] 3) Solvent removal: The filtered liquid was placed in a vacuum distillation apparatus, and the distillation temperature was controlled at 80℃ and the distillation pressure at 0.03MPa for 2 hours to obtain colorless and transparent liquid polybutadiene. The liquid polybutadiene was then tested.

[0106] The number-average molecular weight is 5000, the viscosity is 40000 mPa·s (at 25°C), the total content of vinyl units in the molecular chain is 85%, one end of the molecular chain has a butyl structure, and the other end is capped with a vinyl or methyl structure, of which the content of the vinyl-capped molecular chain is 75%. Example 2

[0107] Preparation of liquid polybutadiene:

[0108] 1) Polymerization reaction: Add 1,3-butadiene monomer (30% by mass) and tetrahydrofuran solvent to a dry polymerization reactor, stir evenly, and then add initiator (a mixture of n-butyllithium and tetrabutyltin in a molar ratio of 1:0.5). The molar ratio of monomer to initiator is 220:1. Control the reaction temperature at 15℃, the reaction pressure at 0.2MPa, and the reaction time at 6h to obtain the polymerization reaction solution.

[0109] 2) Termination and filtration: Add ethanol (1.5% of the monomer molar amount) to the polymerization reaction solution as a terminator and stir for 15 min to terminate the reaction; then add alumina (8% of the total mass of the reaction system) and filter at 25℃ and 0.15MPa to remove impurities.

[0110] 3) Solvent removal: Place the filtered liquid in a vacuum distillation apparatus, control the distillation temperature at 100℃ and the distillation pressure at 0.02MPa, and remove the solvent for 1.5h to obtain colorless and transparent liquid polybutadiene.

[0111] The liquid polybutadiene was tested and found to have a number average molecular weight of 8000, a viscosity of 90000 mPa·s (at 25℃), a total vinyl unit content of 80% in the molecular chain, a butyl structure at one end of the molecular chain, and a vinyl or methyl end-capping structure at the other end, with the vinyl end-capping molecular chain accounting for 70%.

[0112] Example 3

[0113] Preparation of transparent thermosetting plastics:

[0114] The liquid polybutadiene prepared in Example 1 was cured. Specifically, benzoyl peroxide was used as a curing agent and mixed with the liquid polybutadiene prepared in Example 1 (the mass of the curing agent was 1.0% of the mass of the liquid polybutadiene). After stirring evenly, the mixture was placed in an oven at 120°C and cured for 3 hours to obtain a thermosetting plastic.

[0115] The thermosetting plastic was tested and found to have a transparency of 92%, a tensile strength of 18 MPa, and an impact strength of 28 kJ / m. 2 It exhibits no cloudiness or yellowing, and is colorless and transparent in appearance. Its Shore hardness at 25°C is D74.

[0116] Example 4

[0117] Preparation of transparent thermosetting plastics:

[0118] The liquid polybutadiene prepared in Example 2 was cured. The specific operation was as follows: the liquid polybutadiene was directly cured, the curing temperature was controlled at 290°C, and the curing time was 1.5h to obtain thermosetting plastic.

[0119] The thermosetting plastic was tested and found to have a transparency of 91%, a tensile strength of 16 MPa, and an impact strength of 26 kJ / m. 2 It is colorless and transparent in appearance, and its Shore hardness at 25°C is D70.

[0120] Comparative Example 1

[0121] 1) Polymerization reaction: Add 1,3-butadiene monomer (20 wt% of the total reaction system) and cyclohexane as the polymerization solvent to a dry polymerization reactor. After stirring evenly, add n-butyllithium initiator. The molar ratio of monomer to initiator is 115:1. Control the reaction temperature at 35℃, the reaction pressure at 0.4 MPa, and the reaction time at 6 h to obtain the polymerization reaction solution.

[0122] 2) Termination and filtration: Add methanol (1% of the monomer molar amount) to the polymerization reaction solution as a terminator and stir for 10 min to terminate the reaction; then add diatomaceous earth (10% of the total mass of the reaction system) and filter at 30℃ and 0.2MPa to remove impurities.

[0123] 3) Solvent removal: Place the filtered liquid in a vacuum distillation apparatus, control the distillation temperature at 80℃ and the distillation pressure at 0.03MPa, and remove the solvent for 2 hours to obtain colorless and transparent liquid polybutadiene.

[0124] The liquid polybutadiene was tested and found to have a number average molecular weight of 6000, a viscosity of 12000 mPa·s (at 25°C), a vinyl unit content of 55% in the molecular chain, a butyl structure at one end of the molecular chain, and a vinyl or methyl end-capping structure at the other end, with the vinyl end-capping molecular chain accounting for 30% of the total content. The product was slightly yellow.

[0125] Preparation of transparent thermosetting plastics:

[0126] Thermosetting plastics were prepared using the same curing method as in Example 3, with a transparency of 78% and slight turbidity.

[0127] By comparing Examples 1-4 with Comparative Example 1, the results show that the liquid polybutadiene prepared by the present invention has a regular molecular structure and high purity. The thermosetting plastics prepared with it have excellent mechanical properties and significantly better transparency than the prior art (Comparative Example 1), which fully demonstrates the superiority of the present invention.

[0128] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A liquid polybutadiene, characterized in that, It contains two different end-capped molecular chains; One end of the molecular chain is C1-C. 10 A straight-chain or branched alkyl group, with the other end capped by methyl or vinyl; The vinyl-terminated molecular chain accounts for ≥50%; The total content of vinyl units in the molecular chain of the liquid polybutadiene is ≥70%; The vinyl unit is a 1,2-vinyl structural unit.

2. The liquid polybutadiene according to claim 1, characterized in that, The number-average molecular weight of the liquid polybutadiene is 600-20000; At 25°C, the viscosity of the liquid polybutadiene is 500-100000 mPa·s.

3. The liquid polybutadiene according to claim 1 or 2, characterized in that, The liquid polybutadiene has a C1-C4 straight-chain or branched alkyl group at one end of its molecular chain.

4. The method for preparing liquid polybutadiene according to any one of claims 1-3, characterized in that, Includes the following steps: The liquid polybutadiene was obtained by mixing and reacting 1,3-butadiene monomer, polar solvent and initiator under an inert atmosphere. The initiator is selected from a mixture of alkyl lithium and diethylmagnesium, or a mixture of alkyl lithium and tetrabutyltin; The alkyl lithium is selected from one or more of n-butyllithium, isobutyllithium, and sec-butyllithium; The polar solvent is selected from tetrahydrofuran and / or tetramethylethylenediamine.

5. The preparation method according to claim 4, characterized in that, The content of the 1,3-butadiene monomer in the reaction system is 10wt%-40wt%; The molar ratio of the 1,3-butadiene monomer to the initiator is (10-1000):1; The reaction temperature is 0℃-50℃; The reaction pressure is -0.1 to 0.5 MPa.

6. The preparation method according to claim 4, characterized in that, The preparation method further includes sequential reaction termination and filtration post-treatment; The reaction termination agent is selected from methanol or ethanol; The filtration medium is selected from diatomaceous earth or alumina.

7. A thermosetting plastic, characterized in that, It is obtained by curing the liquid polybutadiene prepared by any one of claims 1-3 or the liquid polybutadiene prepared by any one of claims 4-6; The thermosetting plastic has a transparency of ≥90%, a tensile strength of ≥15MPa, and an impact strength of ≥25kJ / m. 2 .

8. The thermosetting plastic according to claim 7, characterized in that, The curing temperature is 270℃-320℃; The curing temperature rise rate is 5-10℃ / min.

9. The thermosetting plastic according to claim 7, characterized in that, The curing process also includes the addition of a peroxide curing agent; The peroxide curing agent is selected from one or more of benzoyl peroxide, di-tert-butyl peroxide, and di-tert-pentyl peroxide.

10. The thermosetting plastic according to claim 9, characterized in that, The amount of the peroxide curing agent added is 0.1wt%-2wt% of the liquid polybutadiene; The curing temperature is 80℃-150℃; The curing temperature rise rate is 3-8℃ / min.