KR850000111B1 - Process for preparing alkenyl aromatic-butadiene rubbery polymer - Google Patents

Abstract

No content.

Description

Process for preparing alkenyl aromatic-butadiene rubbery polymer

The present invention relates to a process for preparing a rubbery polymer of alkenyl aromatic-butadiene.

Solution polymerized butadiene polymers prepared with lithium base catalysts such as polybutadiene, styrene-butadiene polymers and the like butyene polymers have been found to have very desirable physical action in many applications. A method for synthesizing butadiene polymer with lithium base catalyst is described in US Pat. No. 3,317,918. One end use of these butadiene polymers is in the reinforcement and impact resistant rubber reinforced moldings and extrusion compositions of styrene polymers as described in US Pat. Nos. 3,264,374 and 3,976,721.

These butadiene polymers are produced by various methods. However, in many respects, preferred products are provided as lithium base catalysts. The blotting polymerization of 1,3-butadiene is described in US Pat. No. 3,970,607, which uses 1,2-diene as a reaction regulator to prevent excessive exotherm during polymerization.

Often lithium-initiated or solution polymerized rubbery butadiene polymers are useful as solid-based rubbery masses or extremely viscous liquid forms. In preparing rubber-reinforced alkenyl aromatic polymers such as polystyrene, the rubbery butadiene polymer is dissolved in styrene monomer and the resulting rubber solution is polymerized by mass polymerization or mass-suspension polymerization with or without a diluent. The desired impact resistant styrene polymer is obtained. In preparing the alkenyl aromatic monomer-rubber solution, a corresponding apparatus, service and time are required to obtain a rubber homogeneous solution in the monomer. The monomer-rubber solution is often subjected to polymerization conditions after filtration.

There has been a need for an improved method for preparing rubbery butadiene polymers as solutions using alkenyl aromatic monomers as solvents, in particular to avoid the treatment of undissolved rubber.

(1) 80 to 30 parts by weight of alkenyl aromatic monomer, 20 to 70 parts by weight of butadiene (preferably 75 to 35 parts by weight of alkenyl aromatic monomer and 30 to 60 parts by weight of butadiene) and a solvent which is generally inert under polymerization conditions. To prepare a solution containing up to 50% by weight relative to the total weight of the solution, (2) about 5 to 30% by weight of the combined weight of the alkenyl aromatic monomer and butadiene by initiating polymerization with a lithium-based polymerization initiator This advantage is now achieved in the process for preparing alkenyl aromatic-butadiene rubbery polymers by continuing until conversion to monomer-butadiene polymers, followed by (3) terminating the polymerization and separating unreacted butadiene therefrom. Preferably, the process (4) continues to initiate polymerization until the desired amount of alkenyl aromatic monomer or alkenyl aromatic monomer and comonomer is converted to an alkenyl aromatic polymer until the alkenyl aromatic monomer or alkenyl aromatic After inducing polymerization of the monomer with a comonomer such as acrylonitrile, (5) further separating the alkenyl aromatic polymer reinforced with the rubbery alkenyl aromatic monomer-butadiene polymer from the reaction mixture.

The term "alkenyl aromatic monomer" means an alkenyl aromatic compound of the following structural formula.

Wherein R ₁ is hydrogen or methyl, R ₂ R ₃ , R ₄ are selected from the group consisting of hydrogen and alkyl residues containing up to 10 carbon atoms, provided that the total of R ₂ , R ₃ and R ₄ Carbon atoms are not greater than 10

Examples of such alkenyl aromatic monomers include styrene, vinyl-toluene (all isomeric forms and p-isomers are preferred), α-methylstyrene, p-tert-butyl-styrene, 3,4-di-methylstyrene, 2- Ethylhexylstyrene (all isomers), n-decylstyrene (all isomers) and n-butyl-styrene.

The butadiene and alkylaromatic monomers used in the present invention should generally not contain active hydrogen compounds which inactivate the lithium base catalyst.

Suitable lithium base catalysts for carrying out the invention are described in detail in US Pat. No. 3,317,918. In general, n-butyllithium is preferred from the viewpoint of usability and convenience of use.

The polymerization reaction for preparing the rubbery alkenyl aromatic-butadiene polymers of the invention is advantageously carried out at about 10 to 70 ° C, preferably 30 to 50 ° C. Preferably, this polymerization reaction is carried out in a vessel equipped with a condenser capable of refluxing butadiene as a stirrer and a heat conductor.

The main point is that in the polymerization according to the invention only a relatively small amount of butadiene is converted into a rubbery polymer. The kinetics of the polymerization is that when a large amount of butadiene is polymerized, the polymer no longer becomes rubbery due to the excess alkenyl aromatic monomer content. In addition, when butadiene is converted to more than about 30% by weight of butadiene, the possibility of heat radiation, that is, the possibility that the alkenyl aromatic monomer polymerizes quickly and without difficulty becomes very large. Increasing the polymer conversion of butadiene increases the percent alkenyl aromatic monomer in the polymer and loses rubbery properties suitable for reinforcement.

Termination of the lithium-induced polymerization is easily accomplished by the addition of compounds that donate protons. Representative reaction terminating compounds include water, methyl alcohol, ethyl alcohol, propyl alcohol, acetic acid and propionic acid. At the end of the anionic polymerization, distillation is usually carried out under reduced or no pressure to remove unreacted butadiene from the system. Butadiene is easily condensed and can be reused.

Butadiene rubber prepared according to the present invention has a molecular weight of about 30,000 to 700,000 g per mole and contains about 1 to 40% by weight of alkenyl aromatic monomer copolymerized thereto. Preferably, this rubber contains from about 2 to 25% by weight of alkenyl aromatic monomers and preferably 5 to 15% by weight of styrene used to reinforce the styrene polymer matrix, such as polystyrene or styrene-acrylonitrile copolymers. do.

After the butadiene removal, free radical polymerization of the alkenyl aromatic monomer is carried out using a common free residue initiator such as a peroxy compound, an azo compound or a mixture of peroxy and azo compounds, or the free residue polymerization is exothermicly initiated. Can be.

In general, the free residue polymerization is carried out at a temperature of about 60 to 170 ℃. Free residue polymerization initiated with peroxy is generally carried out in the range of 60 to 170 ° C., but exothermic initiation is generally carried out at a temperature in the range of about 110 to 170 ° C. At least in the initial stage of the alkenyl aromatic monomer polymerization, it is preferable to stir to obtain the desired impact resistant polymer. Suitable devices for this polymerization are described in US Pat. No. 3,243,481.

When the polymerization of the alkenyl aromatic monomers occurs to a desired degree, the reaction mixture is heated at a temperature of about 180 to 250 ° C. and about 0.10 to 100 mmHg pressure to expose the surface of the reaction mixture as much as possible in the volatile removal chamber, and then the polymer is cooled. To remove residual monomer. This polymer is generally useful for extrusion and injection molding.

The invention is illustrated in the following examples.

Example 1

A 1 liter round bottom flask was equipped with a dry ice reflux condenser and stirrer. The vessel is placed under a stream of nitrogen to add 318 g of purified styrene and 170 g of purified butadiene. The contents of the flask are brought to ambient temperature (about 22 ° C.). 2 ml of a solution of 0.523 n of n-butyllithium in hexane is added to initiate the polymerization reaction. The polymerization temperature in the flask depends on the reflux rate of butadiene and ranges from about 14 to 24 ° C. The polymerization was terminated by adding about 0.2 ml of n-propane 5 hours after n-butyllithium was added. Precipitating with methanol recovered the polymer to give 45.5 g of a rubbery styrene-butadiene polymer with 9.3% by weight of the starting monomer weight.

Gel permeation chromatography is used to measure molecular weight using an ultraviolet and refractive index detector. The molecular weight is 187,000 g per mole and the polymer contains 14.9 wt% styrene and 85.1 wt% butadiene. Using the reaction ratios of Hsieh and Glaze (see Rubber Chem. Tech., 43, 22, 1970), where the reaction ratio of styrene is 0.1 and butadiene is 12.5, the calculated composition has 14.5% styrene and butadiene This is 85.5%.

Example 2

A. Fill a 2 liter reaction vessel with a stirrer with nitrogen and add 554 g of purified styrene and 677 g of purified butadiene. The polymerization is initiated with 12.5 ml of a 0.55 normal n-butyllithium solution in hexane. Dry ice is placed on top of the reactor and the reaction mixture is heated to 45 ° C. to condense butadiene vapor and maintain the temperature of the contents below 50 ° C. One hour and 45 minutes after n-butyllithium was added, 5 ml of 1-normal ethyl benzene solution of n-propanol was added to terminate the polymerization.

A test taken of a sample of the reaction mixture showed a solids content of 21.6 wt%. The molecular weight of the polymer measured using the apparatus of Example 1 was 322,000 g per mole, containing 6.8% by weight of styrene, with the remainder being butadiene.

The reaction mixture was mixed with 2 liters of styrene, the solution was stirred and vacuumed to remove excess butadiene monomer, yielding 1123 g of a mixture consisting of 84 g of styrene butadiene rubber polymer and 1039 g of styrene.

B. Add 228.5 g of styrene to this mixture and dilute. To the mixture 150 g of ethylbenzene, 3.75 g of minerals, 1.05 g of 2.25 g alphamethylstyrene dimer (available under the trade name Irganox 1076) and 25 of 1,1-di (tert-butylperoxy) -cyclohexane in ethylbenzene 3 g of active solution is added.

1200 g of the mixture is added to a stirred batch polymerizer and the temperature is raised from 110 ° C. to 160 ° C. over 7 hours. After 4 h an additional 200 g of feed mixture are added. At 7 hours the heating is stopped and the mixture containing 72.1% by weight of solid is placed in a shallow pan and left for 90 minutes in a vacuum oven at about 200 ° C.

The polymer from which the volatiles have been removed is removed from the pan and ground into granules. Samples are extruded to measure physical properties. The tensile strength of the polymer obtained is 2840 pounds per square inch (19.6 MPa) and the tensile strength at break is 2965 pounds per square inch with elongation of 28.1%. Notch Izod impact strength is 1.4 feet-pounds per inch (75 J / m) and the Vicat thermal warping temperature is 212 ° F. This is typical of conventional rubber-containing impact resistant polystyrenes.

Example 3

Various rubbers are prepared by the general method of Example 1 using a change in toluene as a diluent and a styrene-butadiene monomer having a weight ratio of 65:35 as mentioned in the start temperature, n-butyllithium concentration and polymerization time. . The results are described in Table I.

TABLE 1

n-BuLI = n-butyllithium

Conv = Conversion

M _W = average molecular weight g per mole

Cal. = Calculated value

Obs = new value

Claims (1)

A solution containing 80 to 30 parts by weight of an alkenyl aromatic monomer, 20 to 70 parts by weight of butadiene and a solvent which is generally inert under polymerization conditions to 50% by weight relative to the total weight of the solution is prepared, and the polymerization is initiated with a lithium basic polymerization initiator. Until the weight of the combined alkenyl aromatic monomer and butadiene is about 5 to 30% by weight to the rubbery alkenyl aromatic monomer-butadiene polymer, which terminates the weighting and separates unreacted butadiene. A process for preparing a kenyl aromatic-butadiene rubbery polymer.