CA2101334C - Free radical polymerization of vinyl aromatic monomers - Google Patents
Free radical polymerization of vinyl aromatic monomers Download PDFInfo
- Publication number
- CA2101334C CA2101334C CA002101334A CA2101334A CA2101334C CA 2101334 C CA2101334 C CA 2101334C CA 002101334 A CA002101334 A CA 002101334A CA 2101334 A CA2101334 A CA 2101334A CA 2101334 C CA2101334 C CA 2101334C
- Authority
- CA
- Canada
- Prior art keywords
- free radical
- acid
- molecular weight
- polymerization
- vinyl aromatic
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Landscapes
- Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)
Abstract
High. molecular weight polystyrene is prepared by free radical polymerization of styrene monomer in the presence of 5 to 5000 ppm of a soluble organic acid having pKa from 0.5 to 2.5.
Description
WO 92/13904 PCT/US91l09476 21~D1334 _1_ FREE RADICAL POLYMERIZATION OF VINYL AROMATIC MONOMERS
The present '_nvention relates to a process for polymerization of vinyl aromatic monomers. More particularly the present invention relates to an improved process for the free radical polymerization of vinyl aromatic monomers to make high molecular weight polymers.
Currently, production of high molecular weight vinyl aromatic polymers, particularly polymers having weight average molecular weights (Mw) of greater than 300,000, is best performed by the use of anionic polymerization techniques. This is due to the extremely slow polymerization rates required to make high molecular weight vinyl aromatic polymers using free radical chemistry. Disadvantageously however, anionic polymerization processes require expensive anionic initiators and tend to produce discolored products due to the presence of residual lithium-containing salts.
In addition, anionic processes utilize different equipment than free radical processes. Consequently commercial producers of. vinyl aromatic polymers by means of free radical chemistry must invest in anionic polymerization equipment in order to prepare very nigh molecular weight aolymers. Finally, anionic ~5 WO 92!13904 PCT/US91/09476 ~~0.~.33~
_2_ , polymerization cannot be employed to prepare many copoiymeric products. In many eases the monomer is not amenable to anionic polymerization. In other cases block copolymers are formed due to unequal reactivities of the comonomers.
It would be desirable if it were possible to produce high molecular weight polyvinyl aromatic resins utilizing free radical polymerization equipment while obtaining rates that. are commercially practical. Thus ~0 it is to the attainment of the preparation of such high molecular Weight polymers via free radical polymeri-zation techniques that the present invention is directed.
According to the present invention there is provided a process for free radical polymerization of a vinyl aromatic monomer to prepare a high molecular weight polymer characterized in that the polymerization is conducted in the presence of from 5 to 5000 parts per million (ppm) of a soluble organic acid having a pKa from 0.5 to 2.5 at 25°C. It has been surprisingly discovered that in the presence of such an amount of these acids, the free radical polymerization rate is substantially increased, thereby allowing the attainment of high molecular weight polymers in reasonable reaction times.
The vinyl aromatic monomers usefully employed according to the present process include styrene, ring alkyl substituted styrene, particularly C~-~ alkyl and -- especially methyl; ring substituted styrenes and a-methylstyrene. A preferred monomer is styrene. The polymerization can also include a comonomer to prepare vinyl aromatic copolymers. The comonomer must be _3- ~~.~~~~,4 noninterfering with the acid. Examples include (meth)acrylonitrile, (meth)acrylic acid and C1_4 alkyl esters thereof, N-C~_~ alkyl maleimide, N-phenyl maleimide, etc. In addition the polymerization may be conducted in the presence of predissolved elastomer to ' prepare impact modified, grafted rubber containing products.
By the term "soluble" is meant that the acid is sufficiently soluble in the reaction mixture to achieve the indicated.coneentration of organic acid. Preferred organic acids are miscible with neat styrene monomer.
Suitable organic acids include the C1-20 alkyl and aryl substituted sulfonic and phosphoric acids. Examples include methane sulfonic acid, toluene sulfonic acid, camphorsulfonic acid, napthalene sulfonic acid, methyl phosphoric acid, phenyl phosphoric acid, etc. Strong acids, that is, organic acids having a pKa less than 0.5, are not desired due to increased incidence of cationio polymerization as opposed to the desired free radical initiation. Preferred acids have pKa from 1.0 to 2Ø A preferred organic acid is camphorsulfonic acid.
It has been discovered that at increased concentrations of organic acid, cationic polymerization becomes prevalent. Generally, acids with higher pK, that is, weaker acids, may be employed in higher concentration without detrimental effect. Stronger acids are employed in relatively lower concentration. I
;,ationic polymerization is undesirable because~it results in extremely low~molecular weight oligomer~
formation. Even small quantities of such low molecular weight product would significantly reduce the l molecular weight average of the resulting product. Most WO 92/13904 PCT/US91/09a76 23~133~ ~ -~- ..
preferred are amounts of organic acid from 50 to 5000 ppm. The amount of acid is measured with respect to the molar quantity of vinyl aromatic monomer.
A free radical initiator may be employed to further improve the rate of free radical initiation.
Suitable initiators include organic peroxides, and hydroperoxides having up to 10 carbons and other well known free radical initiators. Preferably such initiator is used in an amount from 50 to 2000 ppm based on total monomer, preferably from 100 to 1000 ppm.
The monomer may be polymerized in bulk, that is, in the absence of a diluent, or in the presence of a diluent, that is, in solution. Suitable diluents include toluene, ethylbenzene, and other noninterfering organic liquids. Preferably the reaction is conducted under bulk polymerization conditions. Suitable polymerization temperatures are from 25 to 200°C, preferably from 85 to 180°C.
The polymerization rate according to the present process is substantially increased and the resulting product has substantially increased molecular weight compared to products prepared by free radical polymerization in the absence of an organic acid. --However, because the product has increased molecular weight, .the conversion rate is less at higher acid concentrations compared to lower acid concentrations.
That is, the higher molecular weight polymers require longer reaction times despite incrementally faster polymerization,rates. Preferred. polymer_produet:has a molecular weight (Mw) from 300,000 to 1,000.000, more WO 92/13904 PGT/US91/094~6 -5- ~
preferably 500,000 to 800,000, based on a polystyrene standard as measured by size exclusion chromatography.
The products are employed in applications where high molecular weight vinylaromatic polymers have previously found suitable uses. Particularly preferred are molding polymers comprising the presently prepared polymeric products. The product may be blended with other ingredients such as mold release additives, lubricants, colorants, ignition resistant additives, impact modifiers, glass fibers, as well as other resins such as polyvinylaromatic resins having different molecular weights, polyphenylene oxides, polycarbonates, elastomeric copolymers such as styrene-butadiene block copolymers, polybutadiene, etc.
Having described the invention the following examples are provided as further illustrative and are not to be construed as limiting.
Examples 1-3 Aliquots of styrene monomer which was purified by degassing and contacting with alumina were placed in glass tubes. To each tube was added an amount of methane sulfonic acid further identified in Table 1.
The tubes were sealed under vacuum and placed in an oil bath at 150°C for 1 hour. The tubes were withdrawn and the weight average molecular weight of the polystyrene in each tube measured using size exclusion chromatography. Results are contained in Table 1.
It may be seen~that significant increase in molecular weight is observed upon addition of small quantities of the acid.
WO 92/13904 .. PGT/US91/09476 ,...., 2~.013~4 -6_ Tabls 1 _Run Methane Sulfonie Acid (ppm) _Mw A'~ 0 270 , 000 1 100 460,000 2 300 580,000 3 500 830>000 'comparative Examples 4-8 The reaction conditions of Examples 1-3 were substantially repeated employing various concentrations of camphorsulfonic acid (CSA) at a reaction temperature of 140°C. Weight average molecular weight of the resulting polystyrene and conversion rates are provided in Table II.
Table II
Conversion Rate Run Amt. CSA ppm ~percent/hr) Mw B~ 0 43 28000000 comparative Examples 9-10 The reaction conditions of Examples 1-3 are substantially repeated utilizing phenylphosphonie acid (PPA) at a reaction temperature of 150°C. Weight average molecular weight of the resulting polystyrene and conversion rates are~provided in Table III.
WO 92/13904 ~ ~ ~ ~. ~ ~ l~ PGT/US91/09476 . ... -7- .
Table III
Amt. PPa Conversion Rate _Run (wt. percent)(pereent/hr) _Mw C'~ 0 50 240000 9 0.1 40 280000 0.5 25 430000 *'comparat i ve Examples 11 and 12 10 Aliquots of styrene monomer which was purified by degassing and contacting with alumina were placed in glass tubes. In examples 11 and 12, 500 ppm of camphor sulfonic acid was added to the tube. In Example 12 and comparative run D, 500 ppm t-butyl hydroperoxide was added. Thus, no camphor sulfonic acid is present in run D and Example 12 contained both camphor sulfonic acid and t-butyl hydroperoxide. The tubes were dried over anhydrous calcium chloride, sealed under reduced pressure and placed in an oil bath at 110°C for 2 hours.
The tubes were withdrawn and the polymer was recovered.
The weight average molecular weight of the polystyrene in each tube was measured using size exclusion chromatography. Conversions were determined by weight loss after drying a portion of the polymer at 240°C.
Results are contained in Table IV.
Table IV
Run Percent Solids Mw Mn D~ 19.9 336,000 11,000 11 3.3 1,257,000 754,000 12 24.5 411,000 221,000 snot an example of the invention WO 92/13904 . PCT/US91/09476 .....
~~.~'~~3r~ -8-It may be seen that the use of both a hydroperoxide initiator and an acid gave both high molecular weight polymer and high polymer conversion.
Examples 12-16 The reaction conditions of Examples 1-3 were substantially repeated employing oamphorsulfonic acid (500 ppm based on styrene) and 500 ppm of the following organic peroxides, ditertiary butyl peroxide (Ex. 12), 2,5-dimethy-2,5-dihydroperoxyhexane (Ex. 13), 2,5w dimethyl-2,5-t-butylperoxyhexane (Ex. 14), 9,9,12,12-tetramethyl-7,8, 13, 1~4-tetraoxaspiro [5.8] tetradecane (Ex. 15), and 1,1-di-t-butylperoxycyelohexane (Ex. .6).
Examples 12-15 were conducted at 150°C for two hours.
Example 16 was conducted at 110°C for two hours.
Results are contained in Table V.
~101'~'~~~
_Q_ Table V
Example ppm, csal Pereent MW X 103 Mn x '03 Solids 12 500 98.5 211 89 E# 0 98.8 171 76 13 500 83.4 223 110 F~ 0 86.0 186 93 1u 500 98.9 25u 100 G~' 0 98.8 20o 86 500 71.2 325 158 H~' 0 79.6 236 118 16 500 41.7 348 145 I'~ 0 42.8 266 135 15 ~ Comparative 1 Camphorsulfonie ac id
The present '_nvention relates to a process for polymerization of vinyl aromatic monomers. More particularly the present invention relates to an improved process for the free radical polymerization of vinyl aromatic monomers to make high molecular weight polymers.
Currently, production of high molecular weight vinyl aromatic polymers, particularly polymers having weight average molecular weights (Mw) of greater than 300,000, is best performed by the use of anionic polymerization techniques. This is due to the extremely slow polymerization rates required to make high molecular weight vinyl aromatic polymers using free radical chemistry. Disadvantageously however, anionic polymerization processes require expensive anionic initiators and tend to produce discolored products due to the presence of residual lithium-containing salts.
In addition, anionic processes utilize different equipment than free radical processes. Consequently commercial producers of. vinyl aromatic polymers by means of free radical chemistry must invest in anionic polymerization equipment in order to prepare very nigh molecular weight aolymers. Finally, anionic ~5 WO 92!13904 PCT/US91/09476 ~~0.~.33~
_2_ , polymerization cannot be employed to prepare many copoiymeric products. In many eases the monomer is not amenable to anionic polymerization. In other cases block copolymers are formed due to unequal reactivities of the comonomers.
It would be desirable if it were possible to produce high molecular weight polyvinyl aromatic resins utilizing free radical polymerization equipment while obtaining rates that. are commercially practical. Thus ~0 it is to the attainment of the preparation of such high molecular Weight polymers via free radical polymeri-zation techniques that the present invention is directed.
According to the present invention there is provided a process for free radical polymerization of a vinyl aromatic monomer to prepare a high molecular weight polymer characterized in that the polymerization is conducted in the presence of from 5 to 5000 parts per million (ppm) of a soluble organic acid having a pKa from 0.5 to 2.5 at 25°C. It has been surprisingly discovered that in the presence of such an amount of these acids, the free radical polymerization rate is substantially increased, thereby allowing the attainment of high molecular weight polymers in reasonable reaction times.
The vinyl aromatic monomers usefully employed according to the present process include styrene, ring alkyl substituted styrene, particularly C~-~ alkyl and -- especially methyl; ring substituted styrenes and a-methylstyrene. A preferred monomer is styrene. The polymerization can also include a comonomer to prepare vinyl aromatic copolymers. The comonomer must be _3- ~~.~~~~,4 noninterfering with the acid. Examples include (meth)acrylonitrile, (meth)acrylic acid and C1_4 alkyl esters thereof, N-C~_~ alkyl maleimide, N-phenyl maleimide, etc. In addition the polymerization may be conducted in the presence of predissolved elastomer to ' prepare impact modified, grafted rubber containing products.
By the term "soluble" is meant that the acid is sufficiently soluble in the reaction mixture to achieve the indicated.coneentration of organic acid. Preferred organic acids are miscible with neat styrene monomer.
Suitable organic acids include the C1-20 alkyl and aryl substituted sulfonic and phosphoric acids. Examples include methane sulfonic acid, toluene sulfonic acid, camphorsulfonic acid, napthalene sulfonic acid, methyl phosphoric acid, phenyl phosphoric acid, etc. Strong acids, that is, organic acids having a pKa less than 0.5, are not desired due to increased incidence of cationio polymerization as opposed to the desired free radical initiation. Preferred acids have pKa from 1.0 to 2Ø A preferred organic acid is camphorsulfonic acid.
It has been discovered that at increased concentrations of organic acid, cationic polymerization becomes prevalent. Generally, acids with higher pK, that is, weaker acids, may be employed in higher concentration without detrimental effect. Stronger acids are employed in relatively lower concentration. I
;,ationic polymerization is undesirable because~it results in extremely low~molecular weight oligomer~
formation. Even small quantities of such low molecular weight product would significantly reduce the l molecular weight average of the resulting product. Most WO 92/13904 PCT/US91/09a76 23~133~ ~ -~- ..
preferred are amounts of organic acid from 50 to 5000 ppm. The amount of acid is measured with respect to the molar quantity of vinyl aromatic monomer.
A free radical initiator may be employed to further improve the rate of free radical initiation.
Suitable initiators include organic peroxides, and hydroperoxides having up to 10 carbons and other well known free radical initiators. Preferably such initiator is used in an amount from 50 to 2000 ppm based on total monomer, preferably from 100 to 1000 ppm.
The monomer may be polymerized in bulk, that is, in the absence of a diluent, or in the presence of a diluent, that is, in solution. Suitable diluents include toluene, ethylbenzene, and other noninterfering organic liquids. Preferably the reaction is conducted under bulk polymerization conditions. Suitable polymerization temperatures are from 25 to 200°C, preferably from 85 to 180°C.
The polymerization rate according to the present process is substantially increased and the resulting product has substantially increased molecular weight compared to products prepared by free radical polymerization in the absence of an organic acid. --However, because the product has increased molecular weight, .the conversion rate is less at higher acid concentrations compared to lower acid concentrations.
That is, the higher molecular weight polymers require longer reaction times despite incrementally faster polymerization,rates. Preferred. polymer_produet:has a molecular weight (Mw) from 300,000 to 1,000.000, more WO 92/13904 PGT/US91/094~6 -5- ~
preferably 500,000 to 800,000, based on a polystyrene standard as measured by size exclusion chromatography.
The products are employed in applications where high molecular weight vinylaromatic polymers have previously found suitable uses. Particularly preferred are molding polymers comprising the presently prepared polymeric products. The product may be blended with other ingredients such as mold release additives, lubricants, colorants, ignition resistant additives, impact modifiers, glass fibers, as well as other resins such as polyvinylaromatic resins having different molecular weights, polyphenylene oxides, polycarbonates, elastomeric copolymers such as styrene-butadiene block copolymers, polybutadiene, etc.
Having described the invention the following examples are provided as further illustrative and are not to be construed as limiting.
Examples 1-3 Aliquots of styrene monomer which was purified by degassing and contacting with alumina were placed in glass tubes. To each tube was added an amount of methane sulfonic acid further identified in Table 1.
The tubes were sealed under vacuum and placed in an oil bath at 150°C for 1 hour. The tubes were withdrawn and the weight average molecular weight of the polystyrene in each tube measured using size exclusion chromatography. Results are contained in Table 1.
It may be seen~that significant increase in molecular weight is observed upon addition of small quantities of the acid.
WO 92/13904 .. PGT/US91/09476 ,...., 2~.013~4 -6_ Tabls 1 _Run Methane Sulfonie Acid (ppm) _Mw A'~ 0 270 , 000 1 100 460,000 2 300 580,000 3 500 830>000 'comparative Examples 4-8 The reaction conditions of Examples 1-3 were substantially repeated employing various concentrations of camphorsulfonic acid (CSA) at a reaction temperature of 140°C. Weight average molecular weight of the resulting polystyrene and conversion rates are provided in Table II.
Table II
Conversion Rate Run Amt. CSA ppm ~percent/hr) Mw B~ 0 43 28000000 comparative Examples 9-10 The reaction conditions of Examples 1-3 are substantially repeated utilizing phenylphosphonie acid (PPA) at a reaction temperature of 150°C. Weight average molecular weight of the resulting polystyrene and conversion rates are~provided in Table III.
WO 92/13904 ~ ~ ~ ~. ~ ~ l~ PGT/US91/09476 . ... -7- .
Table III
Amt. PPa Conversion Rate _Run (wt. percent)(pereent/hr) _Mw C'~ 0 50 240000 9 0.1 40 280000 0.5 25 430000 *'comparat i ve Examples 11 and 12 10 Aliquots of styrene monomer which was purified by degassing and contacting with alumina were placed in glass tubes. In examples 11 and 12, 500 ppm of camphor sulfonic acid was added to the tube. In Example 12 and comparative run D, 500 ppm t-butyl hydroperoxide was added. Thus, no camphor sulfonic acid is present in run D and Example 12 contained both camphor sulfonic acid and t-butyl hydroperoxide. The tubes were dried over anhydrous calcium chloride, sealed under reduced pressure and placed in an oil bath at 110°C for 2 hours.
The tubes were withdrawn and the polymer was recovered.
The weight average molecular weight of the polystyrene in each tube was measured using size exclusion chromatography. Conversions were determined by weight loss after drying a portion of the polymer at 240°C.
Results are contained in Table IV.
Table IV
Run Percent Solids Mw Mn D~ 19.9 336,000 11,000 11 3.3 1,257,000 754,000 12 24.5 411,000 221,000 snot an example of the invention WO 92/13904 . PCT/US91/09476 .....
~~.~'~~3r~ -8-It may be seen that the use of both a hydroperoxide initiator and an acid gave both high molecular weight polymer and high polymer conversion.
Examples 12-16 The reaction conditions of Examples 1-3 were substantially repeated employing oamphorsulfonic acid (500 ppm based on styrene) and 500 ppm of the following organic peroxides, ditertiary butyl peroxide (Ex. 12), 2,5-dimethy-2,5-dihydroperoxyhexane (Ex. 13), 2,5w dimethyl-2,5-t-butylperoxyhexane (Ex. 14), 9,9,12,12-tetramethyl-7,8, 13, 1~4-tetraoxaspiro [5.8] tetradecane (Ex. 15), and 1,1-di-t-butylperoxycyelohexane (Ex. .6).
Examples 12-15 were conducted at 150°C for two hours.
Example 16 was conducted at 110°C for two hours.
Results are contained in Table V.
~101'~'~~~
_Q_ Table V
Example ppm, csal Pereent MW X 103 Mn x '03 Solids 12 500 98.5 211 89 E# 0 98.8 171 76 13 500 83.4 223 110 F~ 0 86.0 186 93 1u 500 98.9 25u 100 G~' 0 98.8 20o 86 500 71.2 325 158 H~' 0 79.6 236 118 16 500 41.7 348 145 I'~ 0 42.8 266 135 15 ~ Comparative 1 Camphorsulfonie ac id
Claims (4)
1. A process for free radical polymerization of styrene to prepare high molecular weight polystyrene wherein the polymerization is conducted in the presence of from 5 to 5000 ppm of a soluble organic acid having pKa from 0.5 to 2.5 at 25°C.
2. The process according to claim 1 wherein the organic acid is methane-sulfonic acid or camphorsulfonic acid.
3. The process according to claim 2 wherein the polystyrene has a Mw from 300,000 to 1,000,000.
4. The process according to any one of claims 1 to 3 wherein an organic peroxide or hydroperoxide having up to 10 carbon atoms is additionally present in an amount from 50 to 2000 ppm.
Applications Claiming Priority (9)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US65107291A | 1991-02-06 | 1991-02-06 | |
| US651,072 | 1991-02-06 | ||
| US70448091A | 1991-05-23 | 1991-05-23 | |
| US704,480 | 1991-05-23 | ||
| US784,139 | 1991-10-29 | ||
| US07/784,139 US5115055A (en) | 1991-05-23 | 1991-10-29 | Hydroperoxide catalyzed free radical polymerization of vinyl aromatic monomers |
| US786,168 | 1991-10-31 | ||
| US07/786,168 US5311586A (en) | 1991-10-31 | 1991-10-31 | Dynamic routing-administration |
| PCT/US1991/009476 WO1992013904A1 (en) | 1991-02-06 | 1991-12-17 | Free radical polymerization of vinyl aromatic monomers |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2101334A1 CA2101334A1 (en) | 1992-08-07 |
| CA2101334C true CA2101334C (en) | 2003-08-05 |
Family
ID=27505273
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002101334A Expired - Fee Related CA2101334C (en) | 1991-02-06 | 1991-12-17 | Free radical polymerization of vinyl aromatic monomers |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2101334C (en) |
-
1991
- 1991-12-17 CA CA002101334A patent/CA2101334C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| CA2101334A1 (en) | 1992-08-07 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| AU733887B2 (en) | High gloss high impact monovinylidene aromatic polymers | |
| US5115055A (en) | Hydroperoxide catalyzed free radical polymerization of vinyl aromatic monomers | |
| US5145924A (en) | Free radical polymerization of styrene monomer | |
| KR0161974B1 (en) | Monovinylidene aromatic polymers with improved properties and process for their preparation | |
| AU730639B2 (en) | Improved acid catalyzed polymerization | |
| US3950454A (en) | Polymerizates of olefinic nitriles and diene rubbers | |
| US5990255A (en) | High molecular weight polysytrene production by vinyl acid catalyzed free radical polymerization | |
| EP0565075B1 (en) | Emulsion polymerization method for a brominated styrene | |
| CA2101334C (en) | Free radical polymerization of vinyl aromatic monomers | |
| US4361684A (en) | Process for preparing copolymers comprising α-alkyl styrene and unsaturated nitrile | |
| US4275182A (en) | Process for the preparation of improved styrene acrylic acid copolymers | |
| US4268652A (en) | Color styrene-acrylonitrile polymers | |
| WO1992013904A1 (en) | Free radical polymerization of vinyl aromatic monomers | |
| CA1277089C (en) | Preparation of impact-resistant poly(alkyl)styrene | |
| EP0862586B1 (en) | A process for preparing a branched polymer from a vinyl aromatic monomer | |
| EP2470591A1 (en) | High impact polymers and methods of making and using same | |
| US6084044A (en) | Catalyzed process for producing high molecular weight monovinylidene aromatic polymers | |
| EP1303526B1 (en) | Novel phosphorus-containing monomers and flame retardant high impact monovinylidene aromatic polymer compositions derived therefrom | |
| JP2565377B2 (en) | Method for producing α-methylstyrene-acrylonitrile copolymer | |
| MXPA97004364A (en) | Production of high-weight polystyrene molecularmedial polymerization of radical-free radical with vinyl acid | |
| US4036911A (en) | Preparation of graft copolymers | |
| CA1077187A (en) | Impact-resistant acrylonitrile copolymer process | |
| AU4458400A (en) | An improved process for producing high molecular weight monovinylidene aromatic polymers and polymodal compositions | |
| MXPA99011696A (en) | Improved acid catalyzed polymerization | |
| EP0149919A2 (en) | High impact copolymer and method of forming same |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed |