DE19801101A1 - Production of random and block copolymers suitable for making fibers, films and moldings - Google Patents

Abstract

Production of random copolymers from monomers S and B by anionic polymerization comprises: (a) using a mixture containing monomers S and B in given initial concentrations; (b) bringing this mixture into contact with the polymerization initiator I or a growing polymer chain PBI or PSI; and (c) adding the remainder of monomer B at a rate determined by repeated solution of given differential equations. Production of random copolymers from monomers S and B by anionic polymerization with a polymerization initiator comprises: (a) using a mixture containing monomers S and B in initial concentrations (S)0 and (B)0 given by equation (1); (b) initiating copolymerization by bringing this mixture into contact with the polymerization initiator I or a growing polymer chain PBI or PSI; and (c) adding the remainder of monomer B at a rate rz for time t given by repeated solution of differential equations (2) to (6); -dB/dt = -rz .(B)z + (kSB/V) . PSI . B + (kBB/V) . PBI . B (2) -dS/dt = (kBS/V) . PBI . S + (kSS/V) . PSI . S (3) -dPBI/dt = (kBS/V) . PBI . S - (kSB/V) . PSI .B (4) -dPSI/dt = (kSB/V) . PSI . B - (kBS/V) . PBI .S (5) -dV/dt = -rz - (1/ rho s - 1/ rho p) Ms . dS/dt - (1/ rho B - 1/ rho p) MB . dB/dt (6) s = the required fraction of monomer B in the copolymer in mol.%; kBB = the reaction velocity constant for addition of monomer B to the growing polymer chain PBI with a monomer B as last added monomer; kSS = the reaction velocity constant for addition of monomer S to the growing polymer chain PSI with a monomer S as last added monomer; kSB = the reaction velocity constant for addition of monomer B to the growing polymer chain PSI with a monomer S as last added monomer; kBS = the reaction velocity constant for addition of monomer S to the growing polymer chain PBI with a monomer B as last added monomer; V = the volume of polymerization mixture at the particular moment; (B)z = the concentration of monomer B in the feed; rho S, rho B = the density of monomers S and B; rho P = the density of the copolymer; MS, MB = the molar weight of monomers S and B; S, B = the amounts of S and B under conditions (7); d(B)/dt = (b/s) . d(S)/dt (7) Independent claims are also included for (a) the production of block or 3-block copolymers with a random copolymer block S/B produced by this process; and (b) copolymers produced by this process.

Description

The invention relates to a method for producing stati copolymers of anionically polymerizable monomers S and B by anionic polymerization with a polymerization i initiator I, and the copolymers obtainable thereby.

The anionic polymerization of vinyl aromatic monomers such as Styrene and dienes such as butadiene are usually supplied in blocks copolymers. This is due to the different relative polymers Rises rates of the monomers used.

However, statistical copolymers or block copolymers are common with random copolymer blocks of vinyl aromatic monomers Ren and serve because of their from the block copolymers different properties, such as glass temperature and mechanical Behavior desired.

By adding polar solvents such as ethers, the copolymerization parameters and polymerization rate to influence so that copolymers with statistical Ver division of the comonomer units obtained along the polymer chain can be. The amount of polar solvents used for this is necessary, however, usually leads to copolymers with clearly higher vinyl content.

Different procedures with different Do. Sations of the monomers proposed, in which the statistical Monomer installation over the respective concentration ratios rend the reaction is effected. GB-A 903 331 describes a Process for the preparation of statistical styrene-butadiene copo low vinyl content polymers in which the comonomers of the Polymerization solution are added so slowly that under the respective polymerization conditions complete implementation of Comonomers takes place during the addition. The space-time yield is however, this method is low.

According to the process according to DE-A 21 17 995, the comonomers are added metered in at constant speed, the preselected Monomer ratio of the feed different from the monomer ver ratio of the template is. In this way it should be possible  the concentration of each monomer constant during the reaction to keep.

GB-A 994 726 teaches a method in which the total amount of vinyl aromatic monomers and those for the desired copolymer Composition necessary proportion of diene monomer is presented. The faster polymerizing butadiene is added in such a way that the initially selected monomer ratio during the polymerisation sation is kept constant. The process continues Regular or at least regular sampling and analysis for Determine the respective styrene concentration beforehand.

The object of the present invention was to provide a simple and economic process for the production of statistical To provide copolymers of monomers S and B. In particular should be the process of producing statistical styrene buta dien copolymers with a low vinyl content and be suitable complex process analysis can be dispensed with.

Accordingly, a process for the preparation of statistical copolymers from anionically polymerizable monomers S and B by anionic polymerization using a polymerization initiator I was found,

• a) produces a mixture containing the monomers S and B in the initial concentrations [S] ₀ and [B] ₀ , the concentration [B] _{0 of} the monomer B in the mixture being calculated according to equation 1:
  With
  s desired proportion of the monomers S in the copolymer in mole percent,
  b desired proportion of the monomers B in the copolymer in mole percent,
  k _BB reaction rate constant of the addition of a monomer B to the growing polymer chain PBI with a monomer B as the last added monomer,
  k _SS reaction rate constant of the addition of a monomer S to the growing polymer chain PSI with a monomer S as the last added monomer,
  k _SB reaction rate constant of the addition of a monomer B to the growing polymer chain PSI with a monomer S as the last added monomer,
  k _BS reaction rate constant of the addition of a monomer S to the growing polymer chain PBI with a monomer B as the last added monomer,
  b) the copolymerization is initiated by bringing the mixture of a) into contact with the polymerization initiator I or a growing polymer chain PBI or PSI,
  c) during copolymerization and the remaining amount of the monomer B with the feed rate r _z been added, with the feed rate r _z at time t by iteratively solving the differential equations (2) to (6)
  With
  V volume of the polymerization mixture at the respective time and
  [B] _z concentration of monomer B in the feed
  ρ _s , ρ _B density of the monomers S and B
  ρ _p density of the copolymer
  M _s , M _B molar mass of the monomers S and B
  S, B Amount of substance of the monomers S and B
  on condition (7)
  results.

The term statistical copolymers are copolymers or Understood copolymer blocks in which the comonomers ent speaking their relative proportion in mole percent in largely sta tistic sequence are built into the polymer.

The method can be applied to all anionically polymerizable monomers ren, preferably those with a vinyl group, such as vinyl aromatics, Dienes, acrylates, methacrylates, acrylonitrile, methacrylonitrile, Acrylamides and methacrylamides can be used.

The process is particularly suitable for the copolymerization of mono mers S and B, which tend to be homopolymers or To form homopolymer blocks, d. H. where one of the monomers reacted much more slowly in the mixture. As monomer S is refers to the monomer which slows down more slowly in the mixture acts.

Vinyl aromatic monomers are preferred as monomers S and Used as monomers B.

As vinyl aromatic monomers, styrene and its α-stel lung or substituted on the aromatic ring with 1 to 4 carbon atoms Derivatives, for example α-methylstyrene, p-methylstyrene, ethyl styrene, tert-butyl styrene, vinyl toluene can be used. Especially styrene is preferably used.

Basically, all dienes are suitable, are preferred but those with conjugated double bonds such as 1,3-butadiene, Isoprene, 2,3-dimethylbutadiene, 1,3-pentadiene, 1,3-hexadienes, Phenylbutadiene, piperylene or mixtures thereof are used. Especially 1,3-butadiene is preferably used.

All customary initiators can be used as the polymerization initiator I. are used, which trigger the anionic polymerization can. As a rule, organometallic ones are suitable for this Compounds, preferably alkali metal alkyls or aryls. Purpose organolithium compounds are used moderately like Ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert.-butyl,  Phenyl, diphenylhexyl, hexamethylenedi, butadienyl, isoprenyl or. Butyllithium, polystyryllithium or PSLi is preferred 1,1-Diphenylhexyllithium used which is easy from the implementation of 1,1-diphenylethylene available with n- or sec-butyllithium is. The amount of initiator required results from the desired amount Molecular weight and is usually in the range of 0.002 to 5 mole percent based on the amount of monomer to be polymerized.

Suitable solvents are compared to the polymerization initiator tor inert solvents. Conveniently one uses aliphatic, cycloaliphatic or aromatic hydrocarbons substances with 4 to 12 carbon atoms such as pentane, hexane, heptane, Cyclohexane, methylcyclohexane, iso-octane, benzene, alkylbenzenes such as Toluene, xylene, ethylbenzene or decalin or suitable mixtures.

The initial concentration [S] _{0 of} the monomer S in the initial charge is generally 2 to 40, preferably 5 to 25, percent by weight. The initial concentration [B] _{0 of} the monomer B results from the desired copolymer composition and the reaction rate constants according to equation (1).

Monomer B is preferably added solvent-free in the feed ben. However, it can also be added in a suitable solvent be. The same solvent is preferably used, in which the polymerization is carried out. This allows e.g. B. achieve better dosing accuracy.

Temperature and pressure are un for the implementation of the method critical. As a rule, at a pressure in the range of 1 to 20 bar and a temperature of 20 ° C to 130 ° C, preferably 60 ° C to Polymerized at 100 ° C.

If in the process according to the invention as a polymerization initiator is not a viable polymer PSI, e.g. B. Polystyryl lithium is used directly, the growing polymer chains PSI according to equation (13) or PBI according to equation (14) result for the first iteration step:

PBI ₍₀₎ = initiator ₍₀₎ -PSI ₍₀₎ (14)

The solution of the differential equations (2) to (6) with the condition (7) are known to the person skilled in the art. For the approximate solution of the system of equations (2) to (7), the following procedure, for example, has proven suitable, for which programs are also available on common personal computers:
For time increments Δt that are small compared to the total feed time of the monomer B, the feed rate r _z = 0 can approximately be used to solve the differential equations (2) to (6). The result is the amount of the monomers S _{t + Δt} and B _{t + Δt} and the growing polymer chains PSI _{t + Δt} and PBI _{t + Δt} as well as the instantaneous volume V _{t + Δt of} the polymerisation mixture at the time t + Δ _t . During this time increment Δ _t depletes the polymerization solution at the faster einpolymeri-stabilizing monomer B, so that the ratio of the monomers B t nomeren to Mo S at time + Δ not _t greater the output ratio [B] ₀ / [S] ₀ according to equation (1 ) corresponds. The amount of monomer B _z in moles which is necessary to restore the initial ratio [B] ₀ / [S] ₀ according to equation (1) is now calculated according to equation (15)

B _z = S _{t + Δt} .B ₀ / S ₀ -B _{t + Δt} (15).

From this amount of monomer B _z in mol and the concentration [B] _z in the feed, the feed rate r _z can be calculated in order to set the target ratio [B] ₀ / [S] ₀ again before the next time increment Δt.

This process is repeated iteratively as often as the amount of monomer B provided from the feed corresponds. In this way, a step-like function of the inlet speed r _z over time is obtained. The time increments Δ _t can be chosen to be constant or variable. The values of the inlet speeds obtained at different times can also be smoothed according to known mathematical methods and approximated by continuous functions, for example the form r _z = bm ^t . In this way, simple functions for controlling the run can be selected.

Towards the end of the feed of the monomers B, the feed rate r _z decreases. It has therefore proven to be advantageous, after polymerization of 90%, preferably 95%, in particular 98%, of the total amount of monomer B to be polymerized, to add the remaining amount in the feed at once or at a constant feed rate. As a result, the polymerization time can be shortened without significantly influencing the polymer composition.

In order to achieve an ideal statistical incorporation of the comonomers into the polymer, the feed rate r _z determined according to one of the methods described above is adhered to as precisely as possible. However, the metering accuracy is limited, particularly in the case of technical apparatus. In general, however, copolymers with the desired properties are obtained if the deviation to higher or lower feed rates on each side is less than 10%, preferably less than 5%, in particular less than 2% of the feed rate r _z determined at the respective time is.

The reaction rate constants k _BB , k _SS , k _SB and k _BS are experimentally determined with their temperature dependence for the respective polymerization system, that is to say for the respective combination of monomers, solvents and, if appropriate, additives such as Lewis bases.

For the system styrene, 1,3-butadiene and cyclohexane, for example, the temperature-dependent reaction rate constants result from equations (8) to (11):

After inserting the molar masses and densities for styrene, butadiene and the density of the random styrene / butadiene copolymer in equation (6), equation (6a) results:

-dV / dt = -r _z -0.020 ds / dt-0.029 dB / dt (6a).

The feed rate r _z can be approximated by an exponential equation of the formula (12)

r _z = V _tot .c ₁ .exp (-c ₂ .t) (12)

With
V _total volume from supply and inflow
c ₁ , c ₂ approximation parameters
t time from the start of the feed of monomer B.
describe.

The approximate parameters c ₁ and c ₂ are dependent on the temperature T and concentration of the polymerization solution and the desired molecular weight M _n and the desired molar ratio s / b of the monomers S and B of the copolymer. For example, they can be adapted to experimental data using standard regression methods.

For the production of statistical styrene-butadiene copolymers in cyclohexane as a solvent, for. B. the parameters c ₁ and c ₂ from Table 1 are used. They apply to the temperature range 313 K to 393 K and 30 to 70 percent by weight with a molecular weight of 25000 to 100000 g / mol and a styrene content of 30 to 70 percent by weight based on the copolymer.

Block copolymers can also be used in the process according to the invention which contain a random copolymer block S / B become. This can be done by the known methods such as sequential anionic polymerization or by multifunctional initiators or can be achieved with coupling agent.

For example, three-block copolymers SS / BS can be produced with a random copolymer block S / B and two blocks of essentially vinyl aromatic monomers S by sequential anionic polymerization. For this purpose, a polymer block PSI is first polymerized from vinylaromatic monomers S and a statistical copolymer block S / B is closed by the process according to the invention by adding a subset of monomer B in accordance with equation (1) and adding further monomer B with the addition rate r _z determined as described above . The second block S is then polymerized onto the copolymer block S / B by adding further vinylaromatic monomer S.

After the molecular weight has been built up, the "living" Po if necessary with usual chain termination or cop plating agents in amounts that are usually according to the used direct the amount of initiator, be implemented.

Proton-active substances are suitable as chain terminators or Lewis acids such as water, alcohols, aliphatic and aromatic carboxylic acids and inorganic Acids such as carbonic acid or boric acid.

To couple the block copolymers, bifunctional or multifunctional nelle compounds, for example halides of aliphatic Hydrocarbons such as dibromomethane, bischloromethylbenzene or Silicon tetrachloride, dialkyl silicon dichloride, alkyl silicon trichloride or tin tetrachloride, polyfunctional aldehydes such as Therephthalic acid dialdehyde, ketones, esters, anhydrides or epoxides be used. Carboxylic acid esters such as vinegar are preferred Acid ethyl ester used as a coupling agent if no Lewis bases such as tetrahydrofuran are present. In the presence of bases Diepoxides such as 1,4-butanediol diglycidyl are preferably used ether or epoxidized vegetable oils such as epoxidized linseed oil or soy.

As an additive influencing the polymerization parameters (Ran domizers) can, for example, Lewis bases, such as polar, aprotic Solvents or hydrocarbon-soluble metal salts inserted be set. As Lewis bases, for example dimethyl ether,  Diethylene glycol dimethyl ether, tetrahydrofuran, or tertiary Amines such as pyridine and tributylamine can be used. Among the hydrocarbon-soluble metal salts are preferably used Alkaline or alkaline earth salts of primary, secondary and tertiary Alcohols, particularly preferably the potassium salts, such as potassium tetrahy drolinaloolat.

With the addition of a randomizer, the statistical monomeure can be ensured even in the event of deviations from the ideal inlet speed r _z . The absolute polymerization rate can also be increased in this way, thus enabling higher space-time yields.

If you value a low vinyl content, but no randomizer added or the concentration so low held that the vinyl content does not increase significantly. The ideal Concentration depends on the choice of the randomizer. At Use of tetrahydrofuran as a randomizer, a coal water Hydrogen such as cyclohexane as a solvent and a lithium organ nyl compound as the initiator is the ideal concentration usually below 0.3 percent by volume, preferably below 0.1 vol .-%, particularly preferably below 0.03 vol .-%.

When using potassium tetrahydrolinaloolate as a randomizer, a hydrocarbon such as cyclohexane as a solvent and a lithium organyl as initiator is advantageously a Li thium / potassium ratio of at least 25/1, preferably at least 40/1 and particularly preferably selected at least 60/1.

The method according to the invention allows statistical Copolymers S / B from monomers S, such as styrene and monomers B, such as Butadiene in a simple and reproducible manner without time-consuming To produce process analytics. The process can quickly start their process conditions, such as temperature or other copolymer compositions without time-consuming preliminary tests the.

Examples Production of statistical styrene-butadiene copolymers Examples 1 to 3

Cyclohexane, styrene and butadiene were presented in the amounts V ₀ visible from Table 1. The polymerization initiator n-butyllithium (BuLi) was added at 80 ° C. and the butadiene feed was started at the same time. The feed rate was adjusted to the specified end time (Table 1) in accordance with the curves from FIG. 1, then the remainder was metered in at 0.01 ml / s. The copolymers show only one glass level and the 1,2-vinyl content is below 8% (Table 1).

Claims (7)

1. A process for the preparation of statistical copolymers from anionically polymerizable monomers S and B by anionic polymerization with a polymerization initiator I, characterized in that

• a) produces a mixture containing the monomers S and B in the initial concentrations [S] ₀ and [B] ₀ , the concentration [B) _{0 of} the monomer B in the mixture being calculated according to equation 1:
  With
  s desired proportion of the monomers S in the copolymer in mole percent,
  b desired proportion of the monomers B in the copolymer in mole percent,
  k _BB reaction rate constant of the addition of a monomer B to the growing polymer chain PBI with a monomer B as the last added monomer,
  k _SS reaction rate constant of the addition of a monomer S to the growing polymer chain PSI with a monomer S as the last added monomer,
  k _SB reaction rate constant of the addition of a monomer B to the growing polymer chain PSI with a monomer S as the last added monomer,
  k _BS reaction rate constant of the addition of a monomer S to the growing polymer chain PBI with a monomer B as the last added monomer,
• b) the copolymerization is initiated by bringing the mixture of a) into contact with the polymerization initiator I or a growing polymer chain PBI or PSI,
• c) during copolymerization and the remaining amount of the monomer B with the feed rate r _z been added, with the feed rate r _z at time t by iteratively solving the differential equations (2) to (6)
  With
  V volume of the polymerization mixture at the respective time and
  [B] _z concentration of monomer B in the feed
  ρ _s , ρ _B density of the monomers S and B
  ρ _P density of the copolymer
  M _s , M _B molar mass of the monomers S and B
  S, B Amount of substance of the monomers S and B
  on condition (7)
  results.

2. The method according to claim 1, characterized in that styrene is used as the monomer S and butadiene as the monomer B in cyclohexane as the solvent and the reaction rate is used which is constant according to the equations (8) to (11)
for the reaction temperature T. 3. The method according to claims 1 or 2, characterized in that the feed rate r _z by an exponential equation of the formula (12)
r _z = V _tot .c ₁ .exp (-c ₂ .t) (12)
With
V _total volume from supply and inflow
c ₁ , c ₂ approximation parameters
t Approximate time from the start of monomer B feed. 4. Process for the production of block copolymers with a sta statistical copolymer block S / B, characterized in that to copolymer block S / B by a method according to An produces sayings 1 to 3. 5. Process for the production of three-block copolymers SS / BS with a random copolymer block S / B and two blocks of essentially vinylaromatic monomers S, characterized in that

• a) a polymer block PSI is produced by anionic polymerization of vinylaromatic monomers S,
• b) polymerized a random copolymer block S / B by the method according to any one of claims 1 to 4
• c) and by adding further vinyl aromatic monomers S, the second block S is polymerized to the copolymer block S / B.

6. Copolymers, obtainable by the process according to one of the An sayings 1 to 5. 7. Use of the copolymers according to claim 6 for the preparation of fibers, foils and moldings.