Copolymer of alpha-methyl styrene and acrylonitrile, and process for its preparation.

p0001Copolymers of α-methyl styrene and acrylonitrile, hereinafter also referred to as AMS resins, are used as thermoplastic mixing partner in ABS plastics and various blends.

p0002From U.S. Patent 3,644,577 it is known to modify the properties of polyvinyl chloride (PVC) by the addition of AMS resins in the direction of higher heat resistance, improved processability and lower permeability to gases.

p0003EP-A 0,042,106 describes similar polymer mixtures which additionally contain graft polymers with specific chemical structure. Here, the AMS copolymer is prepared in emulsion and spray dried as latex mixture with the Pfropfsystem. This modified PVC is used for drainage pipes for hot water.

p0004However, conventional AMS copolymers tend to blend with PVC to thermal degradation and discoloration, which makes these mixtures for many uses unusable. There have therefore been attempts to alter by specific reaction conditions, the structure of AMS-resin so that this disadvantage is eliminated.

p0005So one has developed in the US Patent 3,491,071 a suspension process in which the polymerization of the monomers takes place under pressure and with a connected degassing the liberation of residual monomers. Due to the great expense of this process a conventional emulsion polymerization has been unsuccessful.

p0006The same applies to the one described in EP-A 0,107,795 or mass suspension polymerization, in which one must also work with very specific and difficult to access bifunctional peroxides.

p0007The EP-A 0,044,097 describes an emulsion polymerization process for the preparation of AMS resins, is produced in which, by a certain temperature a little guide thermoformable copolymer. This material tends to thermal discoloration, however, especially in combination with PVC.

p0008From EP-A 0041703, a polymerization process is known in which by maintaining certain concentrations are accessible with low thermal discoloration of acrylonitrile in the reaction mixture residual monomer products. These show in combination with other polymers, for example graft rubbers, only moderate toughness; at higher processing temperatures, surface defects form.

p0009In DE-OS 3128370 the production of color-stable, heat-resistant form AMS resins is described, wherein the molar ratio of α-methyl styrene / acrylonitrile up to a conversion of 90% at 1.3: 1 is maintained: 1 to 3.0. The polymerization stops at about 97%, so that high levels of residual monomers remain; characterized the heat resistance of blends is lower. Further, these resins give under thermal load, considerable amounts of Ausdampfprodukten on how the "fogging" test according to DIN Draft 75 201 permits or provisional ISO prove 6452nd

p0010DE-OS 3,431,194 specifies an emulsion for producing AMS resins in which certain of compliance monomer ratios to sales well polymerized products with a low tendency to discoloration are available in ABS systems specifically. For use in PVC, the thermal stability of the materials, however, is not sufficient.

p0011It has been found that an AMS resin is accessible through a special emulsion, which provides in combination with other polymers, in particular PVC, excellent thermal and color-stable alloys and also shows high heat resistance and good fogging behavior.

p0012The inventive AMS resin is obtained by radical-initiated copolymerization of a mixture feed 30 to 32 parts by weight acrylonitrile and 68 to 70 parts by weight of α-methylstyrene in the presence of a carboxyl-containing emulsifier, wherein the polymerization is carried out so that prior to the feed-start of the monomers, a seed latex of a same or analogous copolymer is submitted, the reaction temperature was maintained between 75 and 82 ° C and the molar ratio of emulsifier to initiator is 4 to 6

p0013The thus reconstituted AMS resin preferably has molecular weights of 5 x 10⁴ to 5 x 10⁵, more preferably 10⁵ to 2 x 10⁵ (viscosimetric determination according to Angew. Makromol Chemistry 2 (1969), pp 16-34).

p0014In principle, all the known emulsion polymerization techniques for the preparation of the novel copolymers are suitable. Be particularly favorable following procedure has been found:

p0015An aqueous liquor in a stirred reactor is used in an amount of 150 - 300 presented wt .-% (based on the polymerizing monomer); it contains the emulsifying, the seed latex and optionally a regulator. After heating of the charge to the polymerization temperature 75-82 ° C, the initiator to and metered afterwards in 4 to 7 hours, the monomer mixture, is optionally added to further initiator and allowed to react. The resin latex obtained is, where appropriate after mixing with other polymer latexes, and optionally after the addition of aggregates coagulated in a known manner, washed, dried and further processed thermoplastically.

p0016Suitable emulsifiers are anionic, Carboxyl into consideration, for example resin soaps, fatty acid soaps and alkali metal salts of synthetic, surface-active carboxylic acids; thereof are resin soaps, ie disproportionated and isomerized abietic acid are particularly preferred.

p0017The initiators water-soluble systems, such as persulfates and perphosphates; Especially preferred are persulfates, of which potassium peroxodisulfate produces the best product properties.

p0018As a regulator for adjusting the molecular weights used to organosulfur compounds which are long-chain mercaptans such as n- and t-dodecylmercaptan being preferred. The regulators are dissolved in appropriate monomer.

p0019Emulsifiers, initiators and regulators, may also be vergelegt in the aqueous liquor or separately metered as a further feeds over the polymerization.

p0020The reaction temperature must present invention are at 75 to 82 ° C, the precise location rich is directed within this Be on technical possibilities to dissipate the heat of polymerization. Temperatures below 75 ° C, the reaction slow down too much, at temperatures above 82 ° C, the desired molecular weights are not achieved and the final yield returns. In order to achieve both high molecular weight and low residual monomer content, it has been proven, the temperature is lower than about 3/4 of Monomerdosierzeit to keep eg at 77 ° C and constant in the last quarter and at the subsequent time to fully react on eg 80 ° C increase. In this temperature control must not exceed 82 ° C. It then reaches final conversions of> 97%, usually> 98%.

p0021Compliance with these conditions is critical for the quality of the produced AMS resin.

p0022According to the invention are employed in the aqueous polymerization a seed latex a, which was also preferably manufactured according to the invention. The amount of seed latex is from 0.1 to 3.5, preferably 1.0 to 2.0 wt .-% (solid / solid) of the total amount of the product to AMS resin. As seed latex and copolymers are used, in which the α-methyl styrene is completely or partly replaced by styrene.

p0023Particularly preferred are seed latices, in which the average particle diameter of the polymer particles, as measured by turbidity measurement is less than 110 nm. For the polymerization, it is usually 0.2 to 1.0 wt .-%, preferably 0.3 to 0.8 wt .-% of initiator, and 1.5 to 3.0 wt .-%, preferably 2.0 up to 2.8 wt .-% emulsifier is a (quantities based on 100 parts by weight of AMS resultant resin). Type and amount of these two components are dimensioned such that a molar ratio of emulsifier to initiator results in 4 to 6 This molar ratio is - on the known laws of the emulsion addition - of decisive importance for the technical quality of AMS resins. If one stays below the said ratio, the polymerization is slow, high revenues do not, and the product discolor under thermal stress. Exceeding the relationship, so the rises "fogging" value greatly.

p0024The inventively obtained AMS resin emulsions can be further processed by known methods. For example, they can, if appropriate after addition of additives such as stabilizers, antioxidants, anti-aging agents alone or after mixing with other Lataces such graft rubbers are coagulated, washed, dehydrated and dried to obtain powdery masses arise. These powders can with other polymers, in particular PVC and plasticizers, by conventional mixing techniques, are combined on snails, kneaders and calenders for example, using conventional plastic surcharges such as colorants, slip agents, antistatic agents, excipients and fillers and reinforcing agents may be added. The End-molding into useful objects is possible with known techniques such as the film or injection molding.

EXAMPLES AND COMPARATIVE EXPERIMENTS

p0025Here it will be shown that the desired combination of properties can only be achieved within the teaching of the invention. All amounts are parts by weight. The final conversion was determined by gravimetric analysis. The fogging number is to DIN 75 201 (draft), the Vicat value according to DIN 53 460, method B, heating 50 deg / min determined, the AMS resin this grd on a roll at the 190th with 0.4 parts by weight of a lubricant (Loxiol G 70) was compounded and drawn into a coat.

Example:

p0026In a reactor were charged: 3868 parts of demineralized water 42 parts of rosin soap as an emulsifier 42 parts of 1N sodium hydroxide solution 119 parts of an AMS resin latex (seed latex)

p0027The initial charge was heated to 80 ° C and with stirring a solution of 7.7 parts of potassium persulfate in added 300 parts of deionized water about 5 hours from a mixture 1625 parts α-methyl styrene 731 parts of acrylonitrile and 1.8 parts of tert-dodecyl zodosiert stirring constantly. After the feed is added to an aqueous solution of 1 part potassium and stirred for 4 hours at 80-82 ° C after.

p0028After cooling, the latex is stabilized with a salt solution is precipitated usual. Is obtained after washing and drying, a powdery polymer that is processable into plastic alloys in a known manner.

p0029. In the comparative experiments the above-formulation according to Table 1 was changed; the product properties are planar balls noted in Tab. 1.<tables id="tabl0001" num="0001"><table frame="topbot"><title>Table 1</title><tgroup cols="10" colsep="1" rowsep="0"><colspec colnum="1" colname="col1" colwidth="15.75mm" /><colspec colnum="2" colname="col2" colwidth="15.75mm" /><colspec colnum="3" colname="col3" colwidth="15.75mm" /><colspec colnum="4" colname="col4" colwidth="15.75mm" /><colspec colnum="5" colname="col5" colwidth="15.75mm" /><colspec colnum="6" colname="col6" colwidth="15.75mm" /><colspec colnum="7" colname="col7" colwidth="15.75mm" /><colspec colnum="8" colname="col8" colwidth="15.75mm" /><colspec colnum="9" colname="col9" colwidth="15.75mm" /><colspec colnum="10" colname="col10" colwidth="15.75mm" /><thead valign="top"><row><entry namest="col1" nameend="col10" align="left">Comparative example of the invention and comparative tests</entry></row><row><entry namest="col1" nameend="col1" align="left">example 1</entry><entry namest="col2" nameend="col2" align="center">Ex. 1</entry><entry namest="col3" nameend="col3" align="center">Vergleichsvers. a</entry><entry namest="col4" nameend="col4" align="center">b</entry><entry namest="col5" nameend="col5" align="center">c</entry><entry namest="col6" nameend="col6" align="center">d</entry><entry namest="col7" nameend="col7" align="center">e</entry><entry namest="col8" nameend="col8" align="center">f</entry><entry namest="col9" nameend="col9" align="center">G</entry><entry namest="col10" nameend="col10" align="center">H</entry></row></thead><tbody valign="top"><row><entry namest="col1" nameend="col1" align="left">Emulsifier amount</entry><entry namest="col2" nameend="col2" align="char" char=",">42</entry><entry namest="col3" nameend="col3" align="char" char=",">30</entry><entry namest="col4" nameend="col4" align="char" char=",">42</entry><entry namest="col5" nameend="col5" align="char" char=",">42</entry><entry namest="col6" nameend="col6" align="char" char=",">42</entry><entry namest="col7" nameend="col7" align="char" char=",">58.9</entry><entry namest="col8" nameend="col8" align="char" char=",">70.7</entry><entry namest="col9" nameend="col9" align="char" char=",">82.5</entry><entry namest="col10" nameend="col10" align="char" char=",">42</entry></row><row><entry namest="col1" nameend="col1" align="left">Seed latex template (solid)</entry><entry namest="col2" nameend="col2" align="char" char=",">42.8</entry><entry namest="col3" nameend="col3" align="char" char=",">42.8</entry><entry namest="col4" nameend="col4" align="char" char=",">-</entry><entry namest="col5" nameend="col5" align="char" char=",">42.8</entry><entry namest="col6" nameend="col6" align="char" char=",">42.8</entry><entry namest="col7" nameend="col7" align="char" char=",">42.7</entry><entry namest="col8" nameend="col8" align="char" char=",">42.7</entry><entry namest="col9" nameend="col9" align="char" char=",">42.7</entry><entry namest="col10" nameend="col10" align="char" char=",">42.7</entry></row><row><entry namest="col1" nameend="col1" align="left">Acrylonitrile template</entry><entry namest="col2" nameend="col2" align="char" char=",">----</entry><entry namest="col3" nameend="col3" align="char" char=",">----</entry><entry namest="col4" nameend="col4" align="char" char=",">-</entry><entry namest="col5" nameend="col5" align="char" char=",">22</entry><entry namest="col6" nameend="col6" align="char" char=",">----</entry><entry namest="col7" nameend="col7" align="char" char=",">----</entry><entry namest="col8" nameend="col8" align="char" char=",">----</entry><entry namest="col9" nameend="col9" align="char" char=",">----</entry><entry namest="col10" nameend="col10" align="char" char=",">----</entry></row><row><entry namest="col1" nameend="col1" align="left">dosage AMS</entry><entry namest="col2" nameend="col2" align="char" char=",">1625</entry><entry namest="col3" nameend="col3" align="char" char=",">→</entry><entry namest="col4" nameend="col4" align="char" char=",">→</entry><entry namest="col5" nameend="col5" align="char" char=",">→</entry><entry namest="col6" nameend="col6" align="char" char=",">→</entry><entry namest="col7" nameend="col7" align="char" char=",">1615</entry><entry namest="col8" nameend="col8" align="char" char=",">→</entry><entry namest="col9" nameend="col9" align="char" char=",">→</entry><entry namest="col10" nameend="col10" align="char" char=",">→</entry></row><row><entry namest="col1" nameend="col1" align="left">dosage ACN</entry><entry namest="col2" nameend="col2" align="char" char=",">731</entry><entry namest="col3" nameend="col3" align="char" char=",">→</entry><entry namest="col4" nameend="col4" align="char" char=",">→</entry><entry namest="col5" nameend="col5" align="char" char=",">709</entry><entry namest="col6" nameend="col6" align="char" char=",">800</entry><entry namest="col7" nameend="col7" align="char" char=",">722</entry><entry namest="col8" nameend="col8" align="char" char=",">→</entry><entry namest="col9" nameend="col9" align="char" char=",">→</entry><entry namest="col10" nameend="col10" align="char" char=",">→</entry></row><row><entry namest="col1" nameend="col1" align="left">sales temperature</entry><entry namest="col2" nameend="col2" align="char" char=",">80 ° C</entry><entry namest="col3" nameend="col3" align="char" char=",">→</entry><entry namest="col4" nameend="col4" align="char" char=",">70 ° C</entry><entry namest="col5" nameend="col5" align="char" char=",">80 ° C</entry><entry namest="col6" nameend="col6" align="char" char=",">80 ° C</entry><entry namest="col7" nameend="col7" align="char" char=",">80 ° C</entry><entry namest="col8" nameend="col8" align="char" char=",">80 ° C</entry><entry namest="col9" nameend="col9" align="char" char=",">80 ° C</entry><entry namest="col10" nameend="col10" align="char" char=",">85 ° C</entry></row><row><entry namest="col1" nameend="col1" align="left">molar ratio</entry><entry namest="col2" nameend="col2" align="char" char=",">4.53</entry><entry namest="col3" nameend="col3" align="char" char=",">3.24</entry><entry namest="col4" nameend="col4" align="char" char=",">4.53</entry><entry namest="col5" nameend="col5" align="char" char=",">4.53</entry><entry namest="col6" nameend="col6" align="char" char=",">4.53</entry><entry namest="col7" nameend="col7" align="char" char=",">6.45</entry><entry namest="col8" nameend="col8" align="char" char=",">7.75</entry><entry namest="col9" nameend="col9" align="char" char=",">9.00</entry><entry namest="col10" nameend="col10" align="char" char=",">4.53</entry></row><row><entry namest="col1" nameend="col1" align="left">Emulsifier / initiator end sales (%)</entry><entry namest="col2" nameend="col2" align="char" char=",">98.6</entry><entry namest="col3" nameend="col3" align="char" char=",">95.5</entry><entry namest="col4" nameend="col4" align="char" char=",">99.2</entry><entry namest="col5" nameend="col5" align="char" char=",">99.4</entry><entry namest="col6" nameend="col6" align="char" char=",">93.9</entry><entry namest="col7" nameend="col7" align="char" char=",">97.4</entry><entry namest="col8" nameend="col8" align="char" char=",">98.3</entry><entry namest="col9" nameend="col9" align="char" char=",">92.8</entry><entry namest="col10" nameend="col10" align="char" char=",">86.4</entry></row><row><entry namest="col1" nameend="col1" align="left">Fogging number DIN 75201 (Dev.)</entry><entry namest="col2" nameend="col2" align="char" char=",">94</entry><entry namest="col3" nameend="col3" align="char" char=",">0</entry><entry namest="col4" nameend="col4" align="char" char=",">0</entry><entry namest="col5" nameend="col5" align="char" char=",">0</entry><entry namest="col6" nameend="col6" align="left">not marked.</entry><entry namest="col7" nameend="col7" align="char" char=",">91</entry><entry namest="col8" nameend="col8" align="char" char=",">90</entry><entry namest="col9" nameend="col9" align="char" char=",">90</entry><entry namest="col10" nameend="col10" align="char" char=",">0</entry></row><row><entry namest="col1" nameend="col1" align="left">Vicat value VSTB / 50</entry><entry namest="col2" nameend="col2" align="char" char=",">116</entry><entry namest="col3" nameend="col3" align="char" char=",">115</entry><entry namest="col4" nameend="col4" align="char" char=",">117</entry><entry namest="col5" nameend="col5" align="char" char=",">113</entry><entry namest="col6" nameend="col6" align="left">"</entry><entry namest="col7" nameend="col7" align="char" char=",">103</entry><entry namest="col8" nameend="col8" align="char" char=",">106</entry><entry namest="col9" nameend="col9" align="char" char=",">98</entry><entry namest="col10" nameend="col10" align="char" char=",">93</entry></row><row><entry namest="col1" nameend="col10" align="justify">AMS = α-methyl styrene</entry></row><row><entry namest="col1" nameend="col10" align="justify">ACN = Acrylonitrile</entry></row></tbody></tgroup></table></tables>