MXPA97001913A - Process for the polymerization of monomeros dedieno conjug - Google Patents

Abstract

The present invention relates to a process for the polymerization of conjugated diene monomers, characterized in that it comprises anionically polymerizing the monomers in the presence of an anionic polymerization initiator and a microstructure control agent to control the vinyl content of the asynchronous polymer , so the control agent is added to the polymerization mixture in two or more doses, or continuously.

Description

PROCESS FOR THE POLYMERIZATION OF CONJUGATED DIAMOND MONOMERS FIELD OF THE INVENTION The present invention relates to the anionic polymerization of conjugated diene monomer in the presence of an anionic polymerization initiator and an icro-structure controlling agent to control the vinyl content of the polymer thus obtained.

BACKGROUND OF THE INVENTION The polymers of conjugated dienes have been produced by numerous methods. However, the anionic polymerization of such dienes in the presence of an anionic polymerization initiator is the most widely used commercial process. The polymerization is carried out in an inert solvent such as hexane, cyclohexane or toluene and the polymerization initiator is commonly an alkali metal organ compound, especially an alkyl lithium compound. The control of the microstructure of the conjugated diene polymers or conjugated diene polymer blocks REF: 24204 within the polymers is important because a controlled degree of branching in the polymer is desirable. If, as in the case of butadiene, the diene in the polymer is a fully linear chain, such as 1,4-polybutadiene, the polymer, when hydrogenated, will be polyethylene and will have crystallinity. In order to achieve good thermoplastic elastomeric properties in the polymer, it is desirable that the microstructure include a specific uniform degree of branching or vinyl content, such as that possessed by 1,2-butadiene. This will ensure that the desired glass transition temperature (Tg) and hardness are achieved. The desired control of the microstructure to include a desired amount of branching or vinyl content is commonly accomplished by including a microstructure control agent in the polymerization mixture (i.e., the mixture comprising the conjugated diene monomers, the inert solvent , the initiator of the anionic polymerization and the polymer obtained). The desired level of vinyl content is achieved by appropriately selecting the type and amount of those microstructure control agents, which are commonly Lewis basic compounds. Such compounds include ether compounds and tertiary amines. Suitable examples are cyclic ethers such as tetrahydrofuran, tetrahydropyran and 1,4-dioxane; aliphatic monoethers such as diethyl ether and dibutyl ether; aliphatic polyethers such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl. ether, diethylene glycol diethyl ether, and diethylene glycol dibutyl ether; aromatic ethers such as diphenyl ether and anisole; tertiary amine compounds such as triethyl amine, tipropyl amine, tributyl amine; and other compounds such as N, N, N ', N'-tetramethylethylene diamine, N, N-diethyl aniline, pyridine and quinoline. Many of these microstructure control agents are sensitive to temperature. In other words, they will produce varying amounts of vinyl content in the conjugated diene polymer at different temperatures. Thus, if a constant vinyl content is required in the conjugated polymer, the polymerization must be carried out isothermally. Diethyl ether is often used because it is not as sensitive to temperature as others and does not require isothermal operation. Diethyl ether, however, has disadvantages. It is not as effective in the production of conjugated diene polymers with a high vinyl content as other ethers and large amounts of this have to be used. In fact, the quantities that are necessary require that it be separated from the main solvent, such as cyclohexane, in the case of a block polymerization, for example, styrene, the polymerization of which must be ether-free because the ether eliminates many of the the chains of the styrene polymer. The separation of diethyl ether is an additional step that increases costs since it has to be purified and stored for reuse. further, diethyl ether only allows a vinyl content of up to about 38% in butadiene polymers or butadiene polymer blocks. For some applications, however, it may be desirable to achieve a higher vinyl content. Another disadvantage of diethyl ether is that it can not be separated from some solvents such as isopentane. In view of the above, it could be advantageous to use a process to control the microstructure that would not have to be operated isothermally. In addition, it could be an advantage to be able to use a microstructure control agent which would not have to be used in large quantities requiring the separation of the main solvent and purification. It could also be advantageous to be able to vary the microstructure of the polymer produced during the polymerization process. The present invention as described below provides such advantages.

BRIEF DESCRIPTION OF THE INVENTION The present invention constitutes an improvement over the known processes, wherein the conjugated dienes are anionically polymerized in the presence of an anionic polymerization initiator and a microstructure control agent, which is used to control the vinyl content of the obtained polymer . The improvement to this process comprises adding the control agent to the polymerization mixture in two or more doses. In a preferred embodiment of the present invention, the polymerization is carried out in a first adiabatic stage and a second isothermal stage. The control agent is then added to the polymerization mixture in two or more doses during the adiabatic stage in sufficient amounts and times to maintain the desired vinyl content in the relatively constant polymer. In another suitable embodiment of the present invention, the control agent is added in amounts and times so as to produce substantially different vinyl content conjugated diene blocks in the polymer. Preferred microstructure control agents for use in the present process are 1,2-diethoxy-ethane and 1,2-diethoxy propane.

BRIEF DESCRIPTION OF THE FIGURES Figure 1 shows a graph of the temperature / vinyl content ratio for butadiene-styrene block copolymers, which were made using 1,2-diethoxy propane. Figure 2 shows a graph of vinyl content versus butadiene conversion for a conventional one step process. Figure 3 shows a similar graph for the process of adding three steps.

DETAILED DESCRIPTION OF THE INVENTION According to the present invention, polymers containing ethylenic and / or aromatic unsaturations can be prepared by copolymerizing one or more polyolefins, particularly conjugated diene monomers, with themselves or with one or more alkenyl aromatic hydrocarbon monomers. Polymers can, of course, be disordered, recorded, bLocks or a combination of those, as well as linear, starry or radial. Those polymers containing ethylenic unsaturation or aromatic and ethylenic unsaturation can be prepared using anionic initiators or polymerization catalysts, and volumetric techniques, in solution or emulsion. In any case, the polymer containing at least ethylenic unsaturation will generally be recovered as a solid such as a lump, a powder, a pellet or the like. The polymers containing ethylenic unsaturation and the polymers containing aromatic and ethylenic unsaturation are, of course, commercially available from various suppliers. When the anionic techniques are used in solution, conjugated diene polymers and conjugated diene copolymers and alkenyl aromatic hydrocarbons can be prepared by contacting the monomer or monomers to be polymerized simultaneously or sequentially with an anionic polymerization initiator such as the metals of the Group IA, its alkalis, amides, silanolates, naphtalides, biphenyls and anthracenyl derivatives. Suitably use is made of an alkali metal organ compound in a suitable solvent at a temperature within the range of -150 ° C to 300 ° C, preferably at a temperature in the range of 0 ° C to 100 ° C. . Particularly effective anionic polymerization initiators are organolithium compounds having the general formula: RLin In which: R is an aliphatic, cycloaliphatic, aromatic or aromatic hydrocarbon radical substituted with alkyl of 1 to 20 carbon atoms; and n is an integer from 1 to 4. The conjugated diene monomers to be polymerized can be a mixture of two or more different conjugated diene monomers. Suitably, a type of conjugated diene is used. Conjugated dienes that can be anionically polymerized include those conjugated dienes containing from 4 to 12 carbon atoms such as 1,3-butadiene, isoprene, piperylene, methylpentadiene, phenylbutadiene, 3,4-dimethyl-l, 3-hexadiene, Y 4, 5-diethyl-l, 3-octadiene. Conjugated diolefins containing from 4 to 8 carbon atoms are more preferred. The alkenyl aromatic hydrocarbons which may be copolymerized include the vinyl aryl compounds such as styrene, various styrenes substituted with alkyl, styrenes substituted with alkoxy, 2-vinyl pyridine, 4-vinyl pyridine, vinyl naphthalene, and vinyl naphthalates substituted with alkyl. Any of the solvents known in the prior art as useful in the preparation of such polymers can be used. Suitable solvents include straight and branched chain hydrocarbons such as pentane, hexane, heptane and octane, as well as, alkyl substituted derivatives thereof; cycloaliphatic hydrocarbons such as cyclopentane, cyclohexane and cycloheptane, as well as, alkyl-substituted derivatives thereof; aromatic and alkyl-substituted derivatives thereof; alkyl-substituted aromatic and aromatic hydrocarbons such as benzene, naphthalene, toluene and xylene; hydrogenated aromatic hydrocarbons such as tetralin and decalin; linear and cyclic ethers such as methyl ether, methyl ethyl ether, diethyl ether and tetrahydrofuran. The conjugated diene polymers and conjugated diene-alkenyl diene copolymers which may be prepared in accordance with the present invention include those copolymers described in US Pat. Nos. 3,135,716; 3,150,209; 3,496,154; 3,498,960; 4,145,298 and 4,238,202, documents which are incorporated herein by reference. Conjugated diolefin-alkenyl aromatic hydrocarbon copolymers which can be prepared according to the present invention also include the block copolymers described in US Patent Nos. 3,231,635; 3,265,765 and 3,322,856, documents which are also incorporated herein by reference. Polymers that can be prepared in accordance with this invention also include coupled and radial block copolymers such as those described in U.S. Patent Nos. 4,033,888; 4,077,893; 4,141,847; 4,391,949 and 4,444,953, documents which are also incorporated herein by reference. The radial polymers can be symmetric or asymmetric polymers. As indicated hereinabove, it is a common practice to control the microstructure of the diene polymer, ie the vinyl content (1,2 content in the case of polybutadiene), by adding to the polymerization mixture a people controlling the microstructure . These are usually Lewis's basic compounds. They are conventionally added in one dose in the polymerization mixture and the total vinyl content of the polymer is controlled by adjusting the ratio of the microstructure control agent and the polymerization initiator and / or the polymerization temperature. Before the process of the present invention is carried out, the final vinyl content of the polymer must be chosen and the temperature profile of the reaction must be determined. The temperature is determined by the temperature of the feed and the total heat release during the reaction. Next, the temperature / vinyl content / concentration ratio is used for the desired control agent. This is determined by reacting the monomers with the control agent at different temperatures and measuring the vinyl content. These data can be plotted as shown in Figure 1. The data is used to determine how much control agent should be added to keep the vinyl content constant at different temperatures as the temperature increases. The control agent can be added in two or more doses at different temperatures. Continuous addition is the most preferred technique to give the closest possible control of the vinyl content. By speed we approximate the continuous addition with a series of dose. The number of doses depends on the total temperature change. More doses are required for higher temperature increases. The initial temperature indicates the initial concentration and it will not be necessary for the temperature to rise in the adiabatic portion of the reaction according to the predetermined temperature profile. Many agents for controlling the microstructure can be used in the process of the present invention. Those include the aforementioned compounds and heavy ethers, which are difficult to use in the present practice because they are sensitive to temperature. Such heavy ethers include 1,2-diethoxy-ethane, 1,2-diethoxy-propane, orthodimethoxybenzene, 1,2-di-n-butoxy-ethane, 1-t-butoxy-2-n-butoxy-ethane, n -C4H90CH2CH: 0-n-C4H9 / n-C4H9OCH2CH2? -CHOCH3, n-C4H9OCH2CH20-t-C4H9, n-CH9OCH2CH2OCHCH3-0-i-C4H9. Those control agents which are stronger and can be used in small amounts such as diethyl ether used in the present and thus, do not require recovery, storage and treatment facilities, making the total process less expensive to operate. They can be separated from solvents similar to isopentane. In effect, it is preferred to use from 100 ppm to 300 ppm of microstructure control agent to achieve the desired vinyl content. This amount can also be divided between different doses of the agent that is added to the polymerization mixture or several amounts can be added at several points as required or can be added continuously. As indicated hereinabove, many of these microstructure control agents are sensitive to temperature. When the temperature rises, they become less effective and the vinyl content in the polymer produced decreases. The addition of more control agent of the microstructure to the polymerization mixture as the temperature rises helps maintain the microstructure thereof, that is, the vinyl content does not vary appreciably. If this can be achieved, then the process does not have to be done isothermally, a difficult state to achieve. For reproducibility and control in the polymerization process it is much easier to start the process and continue the process where the initial portion of the process was carried out adiabatically and the rest of the process was carried out isothermally. In this way, the microstructure control agent is suitably added to the polymerization mixture during the start or adiabatic portion of the process to maintain the microstructure constant during that time. The addition of the microstructure control agent is usually not necessary during the second or isothermal stage of the process because under those conditions, the microstructure will not change appreciably. Another important advantage of the present process is that conjugated diene blocks with different vinyl content can be produced within the same polymer. For example, a first block of conjugated diene polymer with a desired vinyl content can be produced by adding a certain amount of a microstructure control agent. When the polymerization proceeds, a second quantity of microstructure control agent may be added to the polymerization mixture to produce a second conjugated diene block having a higher vinyl content. In this way, the properties of the polymer can be varied along the length of the polymer as well as its propensity to react to various added functionalizing agents such as epoxy, hydroxyl, amines, and anhydrides to the polymer chain. The invention will now be illustrated by means of the following Examples.

Examples In the following experiments, styrene-butadiene-styrene block copolymers were prepared. The general polymerization scheme for this polymer is shown in Table 1 below.

Table 1: Formulation with Dioxo The following formulation is given as a basis for the described experiments. Some values were adjusted during the course of the experiments (see Tables). Polymer: 12% solids, cy / C6 / i-C5 75/25 weight / weight; 226.8 kg total.

Polymer Temperature of the second step 70 ° C Step I: CH (kg) 79.8 Total sty (kg) 4.5 BuLi (mmoles) 155 Reaction temperature (° C) 30-60 Reaction time (min) 30 Step II: CH (kg) 69.9 • IP (kg) 49.9 Dioxo (g) 29.6 Ratio of Bd (kg / min) 0.456 Bd time (min) 40 Washing time (min) 35 Step III: Temperature (° C) 60 Total Sty (kg) 4.5 Styling time of Sty (min) 4 Washing time (approx; min) 10 Cy-Cβ = Cyclohexane = CH Í-C5 = isopentanto = IP dioxo = 1,2-diethoxy ethane Bd = butadiene Sty = styrene Bu Li = butyl lithium The polymerizations of steps II and III were carried out in a mixture of cyclohexane / isopentane. Part of the butadiene was added in batches and the titration of the solvent was carried out by thermal detection. The control agent of the microstructure, 1,2-diethoxy-ethane was added after completing the titration. After step I and during step II, samples were taken every 5 to 10 minutes to determine the molecular weight increase (by gel permeation chromatography) and to determine the vinyl and styrene content (by H NMR). The polymer thus obtained was hydrogenated. The hydrogenation was carried out using nickel octoate / triethyl aluminum catalyst. After hydrogenation, the polymer cement was washed with acid and neutralized. The mixing time was 30 minutes and the phases were allowed to separate for 15 minutes. The pH of the aqueous phase was 10. The polymer was then recovered by coagulation in steam. 4055 tests were carried out with the semiadiabatic temperature profile during step II, polymerizing 50% of the butadiene batch. Beginning at 30 ° C, the temperature was allowed to rise to 70 ° C without cooling. The cooling began to maintain the temperature at 70 ° C while adding the rest of the butadiene. The amount of control agent of the microstructure used was 130 ppm. In the 4056 trials, only 25% of the butadiene was batch polymerized according to the semiadiabatic temperature profile. In this case, the microstructure control agent was charged in three steps to compensate for the temperature gradient. At the start of step II, 55 parts per million were loaded at 40 ° C, followed by 40 parts per million at 55 ° C and the final 35 parts per million at 70 ° C. The data of the polymerization process are shown below in Table 2: Table 2. Data of the Polymerization Process Test no. 4055 4056 Step I: Reaction time (min) 29 30 Transfer temperature (° C) 46 55 Step II: Temperature (° C) 30-70 40-70 Qualification (mi) 15 12 Dioxo (ppm) 130 55/40/35 Bd in batches (kg) 11.41 5.71 Reason Bd (kg / min) 0.59 0.59 Total Bd (kg) 22.82 22.82 Washing time (min) 30 30 Step III: Temperature (° C) 70-74 70-74 Washing time (min) 10 10 Reason for Sty (kg / min) 1.41 1.41 Total Sty (kg) 5.60 5.60 The analytical data showing the results of the tests on the samples taken during and after the polymerization are shown below in Table 3: Table 3: Analytical Data Test no. 4055 4056 Step I: PM1 (* 10 ~ 3) 29.0 27.3 Step II: PM1 (* 10 ~ 3) 242.6 243.5 Content of Vin (%) 45.1 43.2 Content of Sty (%) 19.2 18.7 Step III: PM1 (* 10 ~ 3) 275.9 277.3 Content of Vin (%) 45.0 43.0 Content of Sty (%) 32.7 32.0 PM Apparent In both Figures 2 and 3, the solid line shows the distribution of instant or immediate vinyl and the dotted line shows the average vinyl content of the polymer produced at a particular time. Figure 2 shows the effect of using a dose of the microstructure control agent in the partially adiabatic process described above. The graphic figure shows the distribution of vinyl in the middle butadiene block as a function of the butadiene conversion. It can be seen that the vinyl content is gradual from 75% to 40% and does not become uniform until the conversion of 30% (constant temperature point). This is due to the high sensitivity to the temperature of the control agent of the microstructure used. In Test 4056, the temperature change was compensated by adding the control agent of the microstructure in three steps as previously discussed. These results are shown in Figure 3. The Figure shows that the vinyl content became uniform at the 5% conversion and remained even when the temperature was increased. It can be seen in Figure 2 that the vinyl distribution falls drastically and is much smaller than the average distribution. However, when the process of the present invention was used (Figure 3), it can be seen that the actual vinyl distribution can be controlled so that it is very close to the cumulative distribution. This is important because it confirms that the actual instantaneous vinyl content remains at the required level and does not fall with the temperature. The tensile properties of the polymers were determined after they were hydrogenated. Those tensile properties are shown in the following Table 4: Table 4. Values of strain and strain and Shore A hardness for hydrogenated and composite polymers1.

Effort (psi) Elongation (%) 3966 4056 100 124 136 300 204 218 500 307 339 TB2 976 952 EB3 (%) 950 900 Hardness Shore A 49 45 1 Average values 2 Tension at break 3 Elongation at break In where # 3966 represents the product resulting from the process using modifier not sensitive to diethyl ether temperature; and # 4056 represents the product of the process using a temperature-sensitive modifier, dioxo, but using the technique incorporated herein to compensate for temperature variation. The data in Table 4 show that the tensile properties of the two polymers are very similar.

This means that several of the important product characteristics of the products made according to the prior art process can be duplicated using the novel and improved process which, in addition, produces a polymer with a highly uniform vinyl content with which, as experience has taught, will produce a polymer with the desired total elastomeric thermoplastic properties especially Tg.

Table 5: Real Measurement versus Estimated Tg. Sample PS PE PB Tg Tg% W% W% w (estimated) (measured) ° C ° C 4055 28.27 38.16 33.25 -46 -482 ± 2 4056 30.59 40.14 29.07 -48 -471 ± 1 4060 30.19 41.97 27.65 -49 -491 ± 1 According to the Fox Equation, we estimate the Tg of the middle block for the three materials. There is only a difference of three ° C between the three materials. The measurement results cover the estimated values, but the errors due to the instrument and the variations in the preparation of the sample are not small enough to differentiate them by themselves. It is noted that with regard to this date, the best method known by the applicant to bring the said invention into practice is that which is clear from the present description of the invention. Having described the invention as above, property is claimed as contained in the following:

Claims (7)

1. A process for the polymerization of conjugated diene monomers, characterized in that it comprises anionically polymerizing the monomers in the presence of an anionic polymerization initiator and a microstructure control agent to control the vinyl content of the polymer thus obtained, so that the Control agent is added to the polymerization mixture in two or more doses, or continuously.

2. The process according to claim 1, characterized in that the polymerization is carried out in a first adiabatic stage and a second isothermal stage, wherein the control agent is added to the polymerization mixture during the adiabatic stage in sufficient amounts and time to keep the vinyl content of the polymer relatively constant.

3. The process according to claim 1 or 2, characterized in that the control agent is selected from the group consisting of 1,2-diethoxyethane, 1,2-diethoxypropane, 1,2-di-n-butoxy-ethane, 1- t-butoxy-2-n-butoxy-ethane, n-C4H9OCH2CH20-n-C4H9, n-C4H9OCH2CH2OCH2OCH3, n-C4H9OCH2CH2OCHCH3OCH2CH3, n-C4H90CH2CH20-tC-.H ?, and nC. | H9OCH2CH2? CHCH3-0-i- C4CH9.

4. The process according to claim 3, characterized in that the control agent is 1,2-diethoxyethane or 1,2-diethoxypropane.

5. The process according to any of claims 1-4, characterized in that the control agent is used in an amount of 100 to 300 ppm.

6. The process according to any of claims 1-5, characterized in that the control agent is added in amounts and times such that diene blocks with substantially different diene contents are produced.

7. The process according to any of claims 1-6, characterized in that the control agent is added to the polymerization mixture continuously.