DE1001001B - Process for the production of thermoplastic copolymers - Google Patents

Description

LIBRARY OF THE GERMAN PATSN OFFICE

GERMAN

NOTICE
THE REGISTRATION
AND ISSUE OF THE
EDITORIAL: JANUARY 17, 1957

This invention relates to the preparation of thermoplastic interpolymers by interpolymerization of styrene and acrylonitrile. In particular, the invention proposes a process for copolymerization of styrene and acrylonitrile, in which the polymerization rate and the Molecular weight of the polymeric product can be well controlled, so that solid, castable resins can be obtained.

Copolymers of about 65 to 80 percent by weight styrene and correspondingly 35 to 20 percent by weight Acrylonitrile are known as "solvent-resistant" resins; H. Resins that are resistant to certain liquids, such as gasoline, alcohol, water, aqueous acids, and aqueous alkalis, are relatively persistent, though these resins are swellable and / or distributable in certain other liquids, such as methyl ethyl ketone. Such copolymers, when properly made, are solid, hard, rigid thermoplastics that by the usual means, e.g. B. by pressing or Sp ritz deformation, spraying, welding, hot pressing etc., can be easily deformed into suitable objects.

Copolymers of styrene and acrylonitrile in the above proportions were thereby obtained that monomeric mixtures of styrene and acrylonitrile are subjected to polymerization conditions became. However, it has been difficult to consistently produce good polymerisation products with satisfactory ones mechanical properties and good behavior when deforming. It is known, that these properties of the product depend on the average molecular weight of the copolymer are dependent. It is also known that the most appropriate combination of mechanical properties (e.g. strength, hardness and flexibility) and behavior when deforming (ζ. e.g. flow rate) is found in copolymers that have such average molecular weights, that 10% solutions of the copolymer in methyl ethyl ketone at a temperature of 25 ° viscosities from 6 to 40, preferably 10 to 30 cP. Since the interpolymerization reaction under violent heat development takes place, it was difficult to regulate this reaction so that copolymerization products of the most convenient kind. The rate of the polymerization reaction increases with the reaction temperature, while the average molecular weight of the copolymer decreases as the temperature increases. This is where the difficulties in producing Copolymers: at temperatures at which the copolymerization reaction can be easily controlled the rate of formation of the copolymer

Process for the production of thermoplastic copolymers

Applicant:

The Dow Chemical Company,
Midland, me. (V. St. A.)

Representative: Dr.-Ing. H. Ruschke, Berlin-Friedenau,

and Dipl.-Ing. K. Grentzenberg, Munich 13,

Ainmillerstr. 26, patent attorneys

Clifford Jones, Linwood, Mich., Bronson Ora Harris
and Frank Lawrence Ingley, Midland, Mich. (V. St. A.) _r have been named as inventors

unfavorably slow, and the molecular weight (or the solution viscosity) of the copolymer is too big. Conversely, at the temperatures at which the copolymer is a favorable average Molecular weight would make the reaction rate so great that it is extremely difficult, if not impossible, to regulate implementation.

An object of this invention is an improved method for making thermoplastic interpolymers of styrene and acrylonitrile of the type described above. A particular goal is a controllable process for the production of a homogeneous copolymer from 65 to 80 percent by weight Styrene and correspondingly 35 to 20 percent by weight of acrylonitrile, the copolymer in 10 weight percent solution in methyl ethyl ketone, d. H. Butanone, has a viscosity of 6 to 40 cP and can be deformed into solid, hard, rigid objects. Other objects and advantages of the invention emerge from the following description.

The objects of this invention are achieved by providing a homogeneous, liquid mixture of 65 to 80 percent by weight Styrene and 35 to 20 percent by weight of acrylonitrile ajuf between 130 and 175 ° lying temperature is heated, wherein the mixture has been added a small amount of at least one modifying agent selected from a group consisting of Benzene, alkylbenzenes and derivatives thereof chlorinated on the nucleus, that styrene was selected and acrylonitrile are copolymerized until. the polymerization mixture does not exceed 70 percent by weight, preferably 20 to 50 percent by weight of the copolymer formed,

609 766/445

and the interpolymer of the non-polymeric ones, the continuous mode being preferred Components of the reaction mixture is separated. will. The polymerizable substances and the modifi-one Part of the styrene can be separated by a-methylstyrene forming agent to mix in the are set, e.g. B. can be given a homogeneous mixture of reaction zone with velocities up to 80 percent by weight styrene, 30 to 0 percent by weight, that of the desired composition a-methylstyrene and 35 to 20 percent by weight speak, or the polymerizable substances can Acrylic acid nitrile is advantageously mixed beforehand as described here. Preferably the whole These processes are misehpolymerized. Charging of polymerizable substances and

The Modifiers for the Polymerization Modifiers in desired amounts prior to this invention are: benzene, chlorobenzenes, mixed and added to a polymerization zone. Alkylbenzenes and alkylchlorobenzenes, e.g. B. Benzene, The type of devices for the polymerization is toluene, xylenes, polymethylbenzenes, ethylbenzene, ethyltoluenes, ethylxylenes, diethylbenzenes, diethyltoluenes,
Polyethylbenzenes, isopropylbenzene, isopropyltoluenes,
Isopropylxylenes, isopropylethylbenzenes, isopropyl-15
ethyltoluenes, isopropyl diethylbenzenes, diisopropylbenzenes, diiisopropyltoluenes, polyisopropylbenzenes,
Chlorobenzenes, di-, tri- and polychlorobenzenes, am
Core halogenated di-, tri- and polyhalotoluenes, am

not particularly critical as long as proper mixing of the contents and heat transfer are used to and from the system are ensured.

The reaction mixture in the polymerization zone is usually heated to temperatures between 130 and 175 °, preferably between 140 and 165 °, held, albeit slightly lower or higher temperatures can be used. At temperatures that

based on a mixture, can be used with good success
can to the desired control of the polymerization rate and the viscosity of the solution
to achieve the polymer.

The polymerization modifiers of this invention are persistent substances that under the conditions the polymerization behave chemically inert. It is not known for sure how their modified

Nuclear chlorinated mono- and polyethylbenzenes and 20 significantly below 130 °, the reaction proceeds with other homologues of benzene chlorinated on the nucleus. Whether- uneconomically low speed, and the probably all these substances and mixtures will have the same viscosity as the solution of the copolymer suitable for practicing this invention are large, if not relatively large, amounts of modification they are applied in their effect on the polymerization agent, which increases the speed of the Process and on the Mischpolymierisatprodukt, such as 25 further reduce polymerization. It is reversed is explained in more detail below, not equivalent. at temperatures well above 175 °, the The polymerization reaction mixture contains pre-polymerization rate in terms of a partially 10 to 40 percent by weight or effective control of heat dissipation too high, any of the above modifying agents, if not relatively large amounts of the modifying agent even if in some cases already 5%, but also up to 30%, which is the solution viscosity of the polyzu 50% modifier to reduce the reaction merizate to an undesired extent.

The presence of the modifying agents in the reaction mixture according to this invention creates two fundamental and important effects emerge: firstly, the rate of polymerization and 35 second, the average molecular weight or the solution viscosity of the polymeric product obtained compared to results obtained under otherwise identical conditions, but without this modifying end Effect comes about, but it is possible to obtain 40 fixing agents, reduced. All that These modifiers generally apply to the activation: the greater the amount of in the output influence and that it is a modifying agent used as an interlinking agent, act during the polymerization. The modification, the greater is the reduction in the polishing agents are not the rate of merization and the solution viscosity of the copolymer chemically bound and can be removed from this according to the mixed polymer. However, the individual are at the end of the polymerization are easily separated. Modifying agents are not the same in their effect,

The process of this invention is essentially as shown in Example 1 below borrowed a modified mass, i. H. Block polymer In the practice of the invention throw the

sation. The starting material consists of a homogeneously polymerizable substance in the reaction zone polynen Mix a polymerizable fraction and 50 meriized until the reaction mixture is no more than the modifier. As indicated above, it is 70 percent by weight, preferably 20 to 50 percent by weight the polymerizable fraction contains 20 to 35 percent by weight of the copolymer. Operations, weight percent acrylonitrile, 35 to 80 weight- in which reaction mixtures are formed that percent styrene and 0 to 30 percent by weight α-methyl contain less than 20 percent by weight polymer, styrene. The modifier levels up to 55 are usually uneconomical. Total reaction mix related, not more than the counterpart, which escapes more than 70 percent by weight of polymer the polymerizable portion, e.g. B. 5 to 50, become excessively viscous, which in turn preferably 10 to 40 percent by weight, since the heat dissipation is made more difficult. In some cases consists essentially of at least one flavor-prone mixture that is more than 70 percent by weight tables contain hydrocarbons of the benzene series or a 60 polymer, to crosslink or soam Nuclear chlorinated derivative of the same. The said "shoot" polymers to form that don't gang mix should be practically free of water and sufficiently thermoplastic to produce good fittings Be polymerization inhibitors. Preferably will give. With the continuous modifications no polymerization catalyst added, although this method can feed rate of the a small amount of a catalyst that forms free radicals, starting material and residence time of the reaction scale, e.g. B. an organic peroxide compound, mixture in the reaction zone can be well regulated, so can optionally be used, but that the desired concentration of polymer in the homely is not required. Mixture leaving the reaction zone is obtained.

The polymerization can be carried out in batches, in half-con

carried out continuously or continuously 70 set monomeric substance and the modification

medium in the usual way, e.g. B. by heating in a vacuum to remove the volatile, non-polymeric substances evaporate and remove, or by precipitation in a non-dissolving liquid in which the is not polymeric substances are soluble, are separated.

The following examples illustrate the invention but do not limit its scope. In the examples Unless otherwise stated, parts and percentages are based on weight.

example 1

This example illustrates the use of some typical modifiers in the process of this Invention.

A mixture of 70% monomeric styrene and 30% monomeric acrylonitrile was produced. For each of several parts of this monomeric mixture one of the following was then added Modifiers are added to make blends labeled A through G. Every of the mixtures obtained (except for mixture E) contained 49% styrene, 21% acrylonitrile and 30% one of the modifiers. Mixture E contained 56% styrene, 24% acrylonitrile and 20% one the modifier. Each of the mixtures A through G was separately put into a continuous apparatus Given polymerization.

The device for continuous polymerization consisted of a pipe coil about 2 m a 2.5 cm thick pipe that was arranged in tight turns and connected to a pump circulate the content; also was for heat transfer taken care to maintain a temperature of 148 to 152 ° in it. The capacity the reaction zone was about 1100 grams of reaction mixture. There were devices attached uim to introduce the starting mix into the queue at a known, controllable speed. At at a point in the queue remote from the feed point of the starting mixture were devices attached to a portion of the 'reaction mixture circulating at the same rate as the Starting mixture was supplied, to be taken, while maintaining sufficient pressure in the reaction zone to obtain the polymerization mixture in the liquid state. The feeding speed was adjusted for each mixture so that a concentration of approximately 20% copolymer was obtained in the reaction mixture. The withdrawn part of the reaction mixture was in Passed a continuous vacuum evaporator where at 5 to 10 mm Hg and with the application of heat the non-polymeric constituents were removed and the copolymer obtained as a residue was less than 1% remaining volatile! Substance contained.

In Table I, the type of modifier, the average polymerization rate in parts by weight of the copolymer formed within 1 hour per 100 parts by weight of reaction mixture in the reaction zone and the solution viscosity and the tensile strength of the copolymer are given for each of the starting mixtures A to G. The solution viscosity of the copolymer is the viscosity in centipoise of a 10% solution of the copolymer in butanone at a temperature of 25 °. The tensile strength of each of the copolymers was determined using injection-molded test pieces in the customary manner and is given in Table I ^{as the tensile strength in kg / cm 2 cross section.}

The copolymerization of a mixture of 70 parts of styrene and 30 parts of acrylonitrile without additives a modifier runs at a temperature of 150 ° with very large and dangerous Speed, and the copolymer made from this mixture has a high solution viscosity and is difficult to deform. In contrast, the polymerization proceeded in the presence of those listed in Table I. Modifying agents at a moderate, well-controlled rate, and all copolymers could be easily deformed after the injection molding process and gave clear, hard products.

Modification with
Art Tabel I. Medium
Polymerization
speed
% per hour Viscosity in cP
in 10%
Butanone solution tensile strenght
kg / cm ^a Starting
mixture benzene tel
%
in the starting
mixture 10.9
27.5
27.9
14.3
20.9
16.2
24.1 9.5
17.2
10.9
5.1
9.9
23.3
17.2 561.4
690.9
711.2
345.8
687.4
692.3
703.5 A.
B.
C.
D.
E.
F.
G toluene 30th
30th
30th
30th
20th
30th
30th Ethylbenzene
Polyisopropylbenzene *)
Polyisopropylbenzene *)
Chlorobenzene
o-dichlorobenzene

*) Mixture of tri-, tetra- and higher isopropylated benzenes.

Example 2

This example shows the effect of the concentration of a modifier, especially of Ethylbenzene, in the starting mixture on the copolymerization of styrene and acrylonitrile.

A mixture of 70 parts of styrene and 30 parts of acrylonitrile was prepared. Ethylbenzene was added to separate parts of this mixture in amounts of 10, 20, 30, 40 and 50 percent by weight, based on the resulting starting mixtures. These starting mixtures were then polymerized in the device described in Example 1 at a temperature of approximately 145 °. In Table II, the mean rate of polymerization is given for each of these tests in parts by weight of the polymer formed in 1 hour per 100 parts by weight of the starting mixture in the reaction zone. The table also contains the viscosity in centipoise of a 10% solution of the copolymer in butanone at 25 ° and the tensile strength of the copolymer in kg / cm ² . All of these products could easily be molded by injection molding.

Tabel II Tensile strength Ethylbenzene
# τί "ΐ r * f% 4 — rr t Tl 0 / Medium poly
merization viscosity
in cP in speed addition m ^ q
the initial speedy
ability, io ° / ₀ iger
Butanone kg / cm ² mixture % per hour solution 682.5 10 42.2 37.4 682.5 20th 29.7 27.7 702.1 30th 19.7 18.1 633.9 40 17.0 12.5 546.7 50 9.5 8.6

IO manner, as described in Example 1, polymerized. In Table IV, the amount of ethylbenzene in the starting mixture, the average polymerization rate in parts of polymer formed in 1 hour per 100 parts of reaction mixture in the polymerization zone, the solution viscosity of the copolymer and the tensile strength of an injection molded specimen are given for each sample.

Table IV Example 3

This example shows the effect that changes in the polymerization temperature have on the Copolymerization of styrene and acrylonitrile in the presence of a modifier, in particular of ethylbenzene.

Several experiments were carried out in the manner described in Example 1, in which starting mixtures from 70 parts of styrene and 30 parts of acrylonitrile, which various amounts of ethylbenzene were added. These tests were carried out at different temperatures and the rates of polymerization and the properties of the products in the usual manner certainly. The average was taken from these numbers (see Table III).

Table III

35

40

45

Ethylbenzene,
% the
Starting
mixture Medium poly
merization
swiftly
ability,
% per hour viscosity
in cP
in io%
Butanone
solution Tensile strength
speed
kg / cm ² 10
30th 47.6
23.7 14.4
10.9 698.6
706.7

temperature
⁰ C Ethylbenzene,
° / o the
Starting
mixture Medium poly
merizations ^
swiftly
ability,
% per hour viscosity
in cP in
io% iger
Butanone
solution 130 20th
30th 18th
12th 36
25th 140 10
20th
30th 43
30th
20th 38
26th
18th 150 10
20th
30th 72
50
35 28
19th
13th 160 20th
30th 80
55 15th
10 170 30th 90 7.5

The table shows that the choice of temperature and concentration of modifying agent any desired combination of rate of polymerization and solution viscosity of the Product can be obtained. Other modifiers as ethylbenzene give results similar to those obtained with ethylbenzene, but in measure deviate from them, which gives even more leeway for the number of conditions, to get a desired product.

Example 4

To 2 parts of a monomer mixture consisting of 30 parts of acrylonitrile, 61 parts of styrene and 9 parts α-methylstyrene consisted of ethylbenzene as a polymerization modifier in an amount of, based on the ethylbenzene monomer mixture, 10 or 30% given. The masses obtained were then separated at 145 ° in the device and in the

Claims (8)

PATENT CLAIMS: 1. A process for the production of thermoplastic copolymers, characterized in that that in a reaction zone at a polymerization temperature between 130 and 175 ° a homogeneous, liquid reaction mixture, that of a polymerizable mass and a polymerization modifier consists, is heated, the polymerizable mass of 20 to 35 percent by weight of acrylonitrile, 80 to 35 percent by weight styrene and 0 to 30 percent by weight methyl styrene, the Polymerization modifiers 10 to 40 percent by weight of the entire reaction mixture and from a group consisting of benzene, alkylbenzenes and derivatives chlorinated on the nucleus is selected that the reaction mixture is heated until it is no longer contains than 70 percent by weight of a copolymer, and that of at least part of the obtained reaction mixture, a copolymer is separated, which in 10 oiger solution in Butanone has a viscosity of 6 to 40 cP at 25 °. 2. The method according to claim 1, characterized in that that a homogeneous starting mixture is added to a polymerization zone, the consists of a polymerizable mass and a polymerization modifier, wherein the polymerizable mass of 20 to 35 percent by weight acrylonitrile, 80 to 35% styrene and 0 to 30% alpha-methylstyrene, the polymerization modifier 10 to 40 percent by weight of the starting mixture and from a group consisting of benzene, alkylbenzenes and chlorinated derivatives thereof on the nucleus, is selected that the reaction mixture heated in the polymerization zone to a polymerization temperature between 130 and 175 ° is until the reaction mixture contains 20 to 50 percent by weight copolymer that at least part of the reaction mixture, which contains 20 to 50 percent by weight copolymer, from is removed from the polymerization zone, and that the copolymer is separated from the portion removed from the reaction zone, the Copolymer in 10% solution in butanone at 25 ° has a viscosity of 6 to 40 cP. 3. The method according to claim 2, characterized in that the polymerizable mass in the ίο essentially from 20 to 35 percent by weight of acrylonitrile and 80 to 65 weight percent styrene. 4. The method according to claim 1, 2 or 3, characterized in that the polymerization modifier Is benzene. 5. The method according to claim 1, 2 or 3, characterized in that the Polymerisatiomsmodisierungsmittel Is toluene. 6. The method according to claim 1, 2 or 3, characterized in that the polymerization modifier Is ethylbenzene. 7. The method according to claim 1, 2 or 3, characterized in that the polymerization modifier Is polyisopropylbenzene. 8. The method according to claim 1, 2 or 3, characterized in that the polymerization modifier Is chlorobenzene.