DE1125656B - Process for the production of suspension polymers in granular form - Google Patents

Description

The invention relates to an improved process for polymerizing aromatic vinyl hydrocarbon monomers with rubber-like polymers of conjugated 1,3-dienes _{dissolved therein} . a suspension polymerization process. In the following description of the invention, for brevity, the aromatic vinyl hydrocarbon monomer solution of the rubbery conjugated 1,2-diene polymer will be referred to simply as the "aromatic vinyl hydrocarbon solution" or the "aromatic vinyl hydrocarbon monomer solution".

Process for the preparation of polymers from aromatic vinyl hydrocarbon monomers with Rubber-like polymers of conjugated 1,3-dienes dissolved therein by suspension polymerization processes are known. One method involves introducing the vinyl aromatic hydrocarbon monomer solution, of water, suspending agent and polymerization initiator in a reaction vessel and stirring and heating the Reaction mixture until the polymerization is essentially complete. In a different way of working the vinyl aromatic hydrocarbon monomer solution is stirred first and in bulk heated to approximately 15% or more of the aromatic Vinyl hydrocarbon monomers are polymerized. The partially polymerized monomer solution is then introduced into a reaction vessel with water and suspending agent while stirring and the polymerization then continued as in the procedure described first.

However, there are difficulties associated with both of the suspension polymerization processes described above. When the aromatic vinyl hydrocarbon monomer solution is introduced directly into the suspension polymerization process, certain properties of the resulting polymers are relatively poor. This applies in particular to the malleability of the polymers and the surface of the objects produced, molded or injection-molded from them. Polymers with good overall properties can be obtained by the other polymerization method in which the aromatic vinyl hydrocarbon monomer solution is first partially polymerized in bulk. However, this other method requires long reaction times because the aromatic vinyl hydrocarbon monomer solution has a very high viscosity and the initial bulk or bulk polymerization is carried out at very low polymerization rates
Suspension polymers in granular form

Applicant:

Monsanto Chemical Company,
St. Louis, Mo. (V. St. A.)

Representative: Dr. E. Wiegand, Munich 15, and
Dipl.-Ing. W. Niemann, Hamburg 1, Ballindamm 26, patent attorneys

Alvin Stein and Robert Louis Walter,

Springfield, Mass. (V. St. A.),
have been named as inventors

must be performed in order to achieve good heat transfer and thus overheating of the material to be polymerized to prevent. There are moreover

as limits on the viscosity of the partial polymerized vinyl aromatic hydrocarbon monomer solutions set, polymerized further in conventional reactors equipped with a stirrer can be. This fact and further the consideration that the vinyl aromatic hydrocarbon monomer solution must be prepolymerized to a conversion of at least 15% and preferably at least 20% prior to entering the suspension polymerization step is added limit the percentage of the rubbery, conjugated 1,3-diene polymer that the polymer can be incorporated. This upper limit on the percentage of rubbery Material that can be incorporated into the polymer again limits the physical Properties, especially the notched impact strength of the end product.

This invention relates to an improved process for the suspension polymerization of aromatic Vinyl hydrocarbon monomers in which major amounts of a rubbery conjugated 1,3-diene polymer are dissolved, which at relatively high polymerization rates can be executed.

The method is characterized in that a mixture "of at least about 35 parts Water and 100 parts of an aromatic vinyl

209 519/475

hydrocarbon monomers in which 1 to 25 parts of a rubbery, conjugated 1,3-diene polymer dissolved, heated in the absence of dispersants, until at least about 15% of the monomers are polymerized and the solution has a viscosity of at least about 75 P at 40 ° C, that one then adds a dispersant and the reaction mixture with stirring and heating in the essentially fully polymerized.

Catch polymerization stage has sometimes been observed that the viscosity increases to a maximum, thereafter it falls and then begins to rise again, so that there is an initial "peak" in the viscosity conversion curve forms. It is very desirable to beyond the conversion in the initial polymerization to carry out this "tip".

After the vinyl aromatic hydrocarbon monomer solution partially in the above

At the initial stage of the process to the _{extent that i 0 has} been polymerized, a

Invention are water and the aromatic dispersants and additionally water, if ge

Vinyl hydrocarbon monomer solution desirably or necessary to the reaction system

Chuk-like, conjugated 1,3-diene polymer, added, and heating and stirring continued,

preferably with a content of an initiator for up to the aromatic vinyl hydrocarbon mono-

free radical polymerization, in a reactor one 15 is essentially completely polymerized.

brought and heated, and in the absence of any -. _ - Suspending agent stirred until (1) at least 15%
of vinyl aromatic hydrocarbon monomer

are polymerized and (2) the viscosity of the partial

The invention is not to the use of any limited to particular dispersants, however, water-soluble ones are preferred for this purpose Mixed polymers of acrylic acid, meth-

polymerized, aromatic vinyl hydrocarbyl acrylic acid or mixtures thereof and 2-ethylhexyl material monomer solution is at least 75 P at 45 ° C. acrylate, 2-ethylhexyl methacrylate or their. It is important to note that the initial mixes used. In this case, such copolymerization must be continued in the absence of suspending agents until the two above-mentioned conditions are met. When the 25 water dissolve at 25 ° C. Such water-soluble suspending agents before reaching one or both copolymers should be 1.5 to 6.5 mol percent and the above conditions are added,
the final polymer has a lower formability and / or poorer surface properties. When carrying out the initial cost and execution reasons, it is customary to use the whole amount of copolymers of acrylic acid and 2-ethyl of water, the hexyl acrylate used in the suspension polymerization.

level is used, with the exception of a small The dispersing effect of the water-soluble mixing

Bring in amount of water that is retained and polymerisate is only weak through changes as a solvent for the dispersing agent is influenced in molecular weight. The preferred

polymers regarded as water-soluble if 0.5 parts of the copolymer are in 99.5 parts

preferably 2.0 to 5.0 mole percent of the 2-ethylhexyl ester included, while the remainder of the copolymer consists of the monomeric acid. the end

However, dispersants have specific viscosities of at least 0.1 when methacrylic acid, and of at least about 0.8 when acrylic acid is the acid monomer contained in the copolymer.

can be used, which will eventually be added to the system. In almost all cases, the The amount of water used initially is at least about 35%, or preferably 50% by weight

of the aromatic vinyl hydrocarbon monomers 40 Both of the above values of the specific viscosity

represent the solution. sity are in 1% solutions in water

It is desirable to polymerize the vinyl aromatic carbon at 25.degree. C. according to the known formula: hydrogen monomer solution to the highest conversion at which the material to be polymerized can still be conveniently handled 45
can. In most cases this is the stage

Specific viscosity

Solution viscosity

■ solvent viscosity

of the process the viscosity of the partially polymerized, vinyl aromatic hydrocarbon monomer solution is the limiting factor

Solvent viscosity determined.

Process for the preparation of such water-soluble

Viscosity is known, apart from the grade of mono-50 dispersants. A method for meren conversion, mainly from the amount of synthetic production of the water-soluble dispersible rubber-like, conjugated 1,3-diene polymer, yeast is that a suitable mono is introduced into the monomer solution, and a mixture of mers and a free radical generating the molecular weight of the rubbery, conjugate - Depending on the polymerization initiator in an organic liquid 1,3-diene polymer. In most cases, an aromatic vinyl hydrocarbon mixture, but a nonsolvent for the monomer solution containing 20% or more of the copolymer produced, should be dissolved and rubber-like, conjugated 1,3-diene polymer to produce it The polymerization is heated to a conversion of at least 15% or usually only a minor dispersant is preferably at least 20% polymerized. 60 concentration necessary, 0.02 to 1.0% and ins-On the other hand, aromatic vinyl hydrocarbon monomer solutions should be 10% or less
rubbery, conjugated 1,3-diene polymer
to a conversion of at least 25% and preferably of at least about 35% polymerized 6g yeast is to be used and that amounts of are. Dispersant above or below this

With a graphic representation of the optimum amount of polymerizate with a higher particle viscosity compared to the conversion in magnitude. Preferably, the

especially 0.05 to 0.5%, based on the amount of water used, is usually sufficient. It is often found that in order to achieve a minimum particle size, an optimal amount of dispersant

smallest amount of dispersant applied, which polymers of the desired particle size generated.

When performing the suspension polymerization stage According to the invention, the pH of the aqueous dispersing medium is preferably below held about 7.0. When using the water-soluble, acidic polymers of the above The type described, the pn value of the aqueous dispersant is in the range from 3.0 to 4.0, which is close to the optimal pn value. If desired, small amounts of inorganic salts can be added to the aqueous medium to suppress emulsification of the polymer.

The value of the procedure is excellent in the z5 Polymerization of aromatic vinyl hydrocarbon monomer solutions containing substantial amounts, z. B. more than 2% and in particular more than 5% of the rubbery, conjugated 1,3-diene polymer contain. The process has been successful in polymerizing styrene monomers at 25 weight percent rubber-like butadiene-styrene copolymer dissolved therein been. The upper limit of the content of rubbery, conjugated 1,3-diene polymer is mainly set by the viscosity obtained in the initial polymerization step.

The rubbery conjugated 1,3-diene polymer of the polymerizable mixture may consist essentially of any rubbery conjugated 1,3-diene polymer having a brittleness temperature of 0 ⁰ C or less exist, the brittleness according to the procedure of ASTM test D 746 -52 T is determined. Typical examples of such polymers are natural rubber itself, synthetic polyisoprene, polybutadiene, copolymers of butadiene and / or isoprene with styrene, acrylonitrile, acrylate ester.

The monomeric component of the polymerizable mixture may consist of (1) one vinyl aromatic hydrocarbon such as styrene; Vinyl naphthalene; ring-substituted alkylstyrenes, d. H. Vinyl toluene, o-ethylstyrene, p-ethylstyrene, 2,4-dimethylstyrene; ring-substituted halostyrenes, d. H. o-chlorostyrene, p-chlorostyrene, o-bromostyrene, 2,4-dichlorostyrene; ring-substituted, alkyl ring-substituted Halostyrenes, d. H. 2-chloro-2-methylstyrene, 2,6-dichloro-4-methylstyrene, etc .; (2) one Mixture of 2 or more aromatic vinyl hydrocarbons which have an aromatic May include vinyl hydrocarbon which does not readily homopolymerize, e.g. B. a-methylstyrene, or (3) a mixture of a vinyl aromatic hydrocarbon in a minor amount a vinyl monomer copolymerizable therewith. Examples of such copolymerizable ones Vinyl monomers are conjugated 1,3-dienes, e.g. B. butadiene, isoprene, «, ^ - unsaturated, monobasic Acids and their derivatives, e.g. B. acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate and the corresponding esters of methacrylic acid, acrylamide, methacrylamide, acrylonitrile, Methacrylonitrile

Except for the rubbery, conjugated 1,3-diene polymer and the aromatic vinyl hydrocarbon monomer the polymerizable mixtures can also generate free radical polymerization initiators, antioxidants, Plasticizers, heat and light stabilizers, polymerization modifiers, dyes or contain coloring agents.

Where parts are given in the examples, they refer to parts by weight.

example 1

100 parts were put into an autoclave lined with glass and provided with a stirrer freshly distilled water and 100 parts of a polymerizable mixture introduced from 94 parts of styrene monomers and 6 parts of a rubbery, conjugated 1,3-diene copolymer with a content of 75% butadiene and 25% styrene. In addition to the styrene monomer and the rubbery material, the polymerizable mixture contained 0.05% ditertiary butyl peroxide, 0.3% of an antioxidant, 0.1% of a technical Cia mercaptan modifier and 2.0% of a refined hydrocarbon oil lubricant. After the atmosphere, After the sphere in the reaction vessel has been purged free of oxygen by means of nitrogen, the reaction mixture is stirred and heated to 120 ° C. for 4 hours heated. At the end of this period, about 40% of the styrene monomer had polymerized, and some of it polymerized styrene monomer solution had a viscosity above 200 P at 40 ° C.

100 parts of water containing 0.05 parts of calcium chloride were then added to the reaction vessel and 0.18 part of a copolymer of 95.5 mole percent acrylic acid and 4.5 mole percent 2-ethylhexyl acrylate with a specific viscosity of about 4.0, which in a 1% solution in water at 25 ° C, which had been determined, were dissolved. The reactor was pressurized with nitrogen, and the reaction mixture was stirred and raised to 130 ° C for 3 hours and 5 hours 140 ° C heated. The product was essentially in quantitative yield and in the form of small, spherical pearls preserved. The polymer exhibited fully comparable or in some cases superior Properties compared to those of the polymer, which according to the known, im Comparative Experiment I was prepared using the method described below. The total response time is 12 hours.

Comparative experiment I

The solution of styrene monomer and rubber-like butadiene-styrene copolymer used in Example 1 was polymerized by stirring the styrene monomer solution and in the Heated mass to a temperature of 110 ° C. As a result of the low heat transfer of the highly viscous solution, the maximum temperature was which could be used in this initial polymerization stage was 110 ° C. 9 hours required to polymerize 33% of the styrene monomer, and the resulting, partially polymerized solution had a viscosity of about 120 P at 40 ° C.

The partially polymerized styrene solution was added to 200 parts of water containing 0.18 part of the Acrylic acid-2-ethylhexyl acrylate copolymer described in Example 1 and contained 0.05 part calcium chloride. The polymerization was taking

Nitrogen pressure completed by stirring the reaction mixture for 3 hours at 130 ⁰ C and 5 hours at 140 ° C. The yield of finely divided polymer particles was quantitative. The total reaction time was 17 hours in comparison with a 12 hour reaction time in Example 1.

Example 2

Example 1 was repeated with the exception that the polymerizable mixture used 10 parts of the rubbery 75:25 butadiene-styrene copolymer, dissolved in 90 parts of styrene monomer. At the end of the initial In the 4 hour polymerization period, 40% of the styrene monomer was polymerized, and that partially polymerized «Styrofoam solution had a viscosity which was significantly above 200 P at 40 ° C. The received Results were comparable to those obtained according to Example 1.

Example 3

In the reactor described in Example 1, 100 parts of water and 100 parts of a polymerizable mixture were introduced which consisted of 6 parts of the 75:25 butadiene-styrene copolymer described in Example 1, 84 parts of styrene monomer and 10 parts of methylstyrene monomer, wherein the polymerizable mixture also contained 0.05% ditertiary butyl peroxide, 0.3% anti-OAydative, 0.1% Q2 engineering mercaptan modifier, and 2.0% refined hydrocarbon oil lubricant. The atmosphere in the reactor was purged free of oxygen by means of nitrogen, and the reaction mixture was stirred and ^{heated to 120 °} C. for 4 hours. At the end of this time, approximately 40% of the monomeric components of the mixture had polymerized and the viscosity of the partially polymerized solution was over 200 P at 40 ° C.

100 parts of water containing 0.18 part of the acrylic acid-2-ethylhexyl acrylate copolymer described in Example 1 and 0.05 part of calcium chloride were introduced into the reaction vessel. The reaction mixture was placed stirred with nitrogen under pressure and heated for 4 hours at 13O ⁰ C and 9 hours at 135 ° C. The resulting polymer was obtained in the form of small, discrete particles.

Example 4

Example 1 was repeated with the exception that 20 parts of the butadiene-styrene copolymer Were dissolved in 80 parts of styrene monomer and the initial polymerization in Absence of the dispersant for only 3 hours instead of that used in Example 1 Hours. After 3 hours, approximately 25% of the styrene monomer had polymerized, and the viscosity of the partially polymerized styrene monomer solution was well over 200P at 40 ° C. The polymerization was carried out by stirring and heating the reaction mixture under nitrogen pressure Completed at 130 ° C for 8 hours. The results obtained were similar to those of Comparable to example 1.

Claims (3)

PATENT CLAIMS; 1. A process for the preparation of suspension polymers in granular form, characterized in that a mixture of at least about 35 parts of water and 100 parts of a 1 to 25% solution of a rubbery, conjugated 1,3-diene polymer in an aromatic vinyl hydrocarbon monomer is in the absence a dispersant until at least about 15% of the monomeric constituents have been polymerized and the solution has a viscosity of at least about 75 P at 40 ° C., a dispersant is then added and the reaction mixture is substantially polymerized with stirring and heating. 2. The method according to claim 1, characterized in that one is used as the dispersant water-soluble copolymer used, the 93.5 to 98.5 mol percent acrylic acid and / or Methacrylic acid and correspondingly 6.5 to 1.5 mol percent of 2-ethylhexyl acrylate and / or 2-ethylhexyl methacrylate contains. 3. The method according to claim 2, characterized in that one is considered rubber-like Polymer is a 1,3-butadiene polymer or a copolymer of 1,3-butadiene and styrene and as a monomer, styrene or a mixture from a larger amount of styrene and a smaller amount of -methylstyrene or acrylonitrile used. Considered publications:
German Auslegeschrift No. 1 047 437;
U.S. Patent No. 2,606,163. . 209 519/475 3.62