KR920006762B1 - Process for preparing impact-polystyrent with good behaviour towards corrosive agents - Google Patents

Abstract

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Description

Method for producing impact resistant polystyrene with good corrosion resistance

The present invention relates to a method for producing a molding material based on polystyrene. More specifically, the present invention relates to a method for producing impact resistant polystyrene with enhanced crack resistance under stress and / or in contact with a caustic.

It is known that molded articles of styrene polymer are cracked by stress when prolonged contact with chemicals causing corrosion. These chemicals are especially oils and fats and organic halogenated blowing agents (eg Freons). In fact, this corrosion appears in the manufacture of packaging for fatty foods and refrigerators of impact-resistant polystyrene; In refrigerator manufacturing, the refrigerator chamber is cracked while the polyurethane is inflated by a blowing agent such as freon. Such a bad property of impact-polystyrene becomes more serious due to the corrosion caused by the penetration of freon when the refrigerator is already completed, and the refrigerator needs to be disposed of or separately disassembled and assembled at a cost.

In order to solve this problem, it has been proposed to coat a refrigerator wall in contact with a freon with a freon-resistant film such as acrylonitrile-butadiene-styrene terpolymer (ABS). However, the installation of such a protective device is expensive. It is also proposed to replace some ABS with polyethylene film. Unfortunately, it is very difficult to bond these dither thermoplastics well. It has also been proposed to increase the crack resistance afterwards by adding another rubber. Unfortunately, even though a large amount of rubber was used, it was ineffective.

It has been found that processes for the manufacture of molding materials which have a good effect in connection with cracking under stress and / or in contact with a caustic have been found.

The present invention bulk polymerizes a rubber solution in styrene, wherein the rubber is an anionic poly with a 1-2vinyl isomer ratio of 10 to 12%, a molecular weight of 300,000 or more, and a viscosity of at least 140 cps for a 5% solution in styrene. Α-methylstyrene dimer, or n-dodecylmercaptan, which is butadiene, and the solution contains 7 to 10% by weight of rubber and the amount used is 0.08% by weight or more based on the total weight of all the components. The presence of a compound selected from tea-dodecyl mercaptan, diphenyl 1,3-butadiene, cis-diphenylcyclobutene, trans-diphenylcyclobutene, methyl phenylindane, diphenylcyclobutane or a mixture of one or more compounds Cyclohexane and Isopar (consisting of aliphatic hydrocarbons) of not less than 7% by weight relative to the total weight of all components present in the solution and in solution: Condensed Chemical Dictionary, Ro se, REINHOLD] or to a process for preparing rubber-modified styrene polymers exhibiting improved stress cracking properties and good low temperature properties, characterized in that the polymerization is carried out in the presence of ethylbenzene. According to an important characteristic of the process of the invention, based on the weight of all components in the solution, based on the mono and / or di and / or triglycerides or mixtures thereof, polyethylene wax, additives with polyethylene glycol functionalities or silicone oils 0.5 to 1% by weight of an additive selected from additives used is used. The use of such additives makes them useful in the molding of polymers. According to the invention, these additives are preferably added after polymerization, for example in an internal mixer.

Using the method of the present invention, it is possible to obtain polymers which not only have good impact resistance but above all have low sensitivity to cracking under stress and / or contact with a caustic and exhibit good performance at the following low temperatures. These properties can be used without special protective treatments for the manufacture of bathroom furniture or kitchen utensils, which must be frequently cleaned with detergents, and for the production of liners and doorliners of refrigerators and freezers. In addition, due to their resistance to corrosive agents, the polymers can be used for the production of seafood containers, especially for fish transportation, and for the production of food packaging, especially for fatty substances.

Using the process according to the invention it is possible to obtain polymers having a swelling index of at least 10. This swelling index is determined by dissolving the obtained polymer in toluene and then centrifuging and decanting the solution. The solid part obtained was weighed in the wet state, dried and re-weighed. Swelling index is defined as:

This index can in fact represent the degree of crosslinking of the rubber. This is also regarded as the inverse of the weight concentration, so the higher the swelling index, the lower the crosslinking degree of the rubber.

In the process of the invention a polymer having a gel content of at least 30 is obtained. This gel content shows the ratio of rubber | gum and is converted into 1 gram of polymer, and is shown by the following relationship.

Another characteristic of the polymer obtained according to the method of the present invention is the average diameter of the dispersed rubbery particles observed according to the electron microscopy described in KATO, J. Electro.Micros. 14, 19865 (20). These are 8 to 13 microns; This diameter is determined according to the method described by CRAIG (J. Polym. Sci. Polim Chem. Ed 15,433 (1977)) and JAMES (Polym. Eng. Sci. 8, 241 (1968)). These measurements can determine the average size and particle size distribution of the elastomeric mass dispersed in the polystyrene matrix. A device commonly used to determine the size polydispersity and size of elastomeric particles dispersed in a styrene matrix is a "COULTER" calculator sold by Coultronics.

In the process of the present invention, a polymer having a characteristic of having a simple glass transition temperature on an elastomer is prepared, which glass transition is measured according to a known method for measuring viscoelasticity and controlled at -80 ° C or lower. The polymer obtained does not exhibit a second transition of -70 ° C to 0 ° C. The measurement of glass transition is carried out by RHEOVIBRON DDV-IIC Viscosity Elasticity Meter or METRAVIB Viscosity Elasticity Meter. The measurement is based on the mechanical properties of polymers and mixtures by NIFLSEN, Vol. 2, 1974, Marcel DERKER Inc. N.Y. And Macromol. Sci. Phys. B9 (2) 187 (1974) by J. BOYER. According to the invention, the rubbery glass transition spectrum spans a specific temperature range corresponding to the frequency position characteristic of the high speed impact frequency.

According to the invention, the solution of styrene and rubber is bulk polymerized by using a rubber composed of anionic polybutadiene having a molecular weight of 300,000 to 400,000 and a viscosity of 140 to 220 cps. The viscosity is measured by dissolving 5 parts by weight of rubber in 95 parts by weight of styrene. Rubbers with viscosities of 200 cps or higher are too viscous to obtain solutions that cannot be handled on an industrial scale, while rubbers with viscosities of 140 cps or less yield polymers as too small particle sizes of less than 10 microns. do. According to the invention, the amount of rubber used is 7 to 10% by weight, based on the amount of styrene used. If more than 10% is used, a polymer is obtained which is too elastic and has moderate mechanical properties, in particular poor strength. According to the invention anionic polybutadienes are recognized as rubbers produced by "anionic" type processes.

According to another feature of the invention, the polymerization reaction is α-methylstyrene dimer or n-dodecyl metcaptan, tertiary dodecyl mercaptan, diphenyl 1,3 butadiene, cis-diphenylcyclobutene, transdiphenyl In the presence of a compound selected from cyclobutene, methylphenylindane, diphenylcyclobutane, or a mixture consisting of one or more of these mixtures, in an amount of 0.08 to 0.3% by weight, based on the total weight of the solution.

)사에 의해 시판되는 중합체 왁스이다. 폴리에틸렌왁스는 적점(dropping point)이 70 내지 80℃이고 밀도가 0.86 내지 0.88이며 평균 분자량이 약 2,500인 제품이며; 이는 씨디에프 시미(CdF CHIMIE)사에 의해 시판된다. 실리콘 왁스는 대부분의 유기 용매에 용해할 수 있는 제품이며, 그들은 다우코닝사에 의해 "DOWCORNING 200 FLUID"란 상품으로 시판된다. 이러한 첨가제의 사용은 완결 제품의 수득한 중합체의 이후의 사용 및 완성제품의 특성을 유용하게 한다. 바람직하게는, 이들 첨가제는 내부 혼합기에서 중합후 첨가된다. 예를들면, 베르너-플라이더러(WERNER-PFLEIDERER)사에 의해 판매되는 GK 5형 혼합기를 이용한다. 용융 흐름 지수는 특히 액체파라핀으로 구성된 가소제 1 내지 3%를 가하여 조절되고, 용융 흐름지수는 "ASTM 스탠다드 D 1238"법에 의해 측정된다.According to another important feature of the invention, the polymerization reaction is carried out in the presence of cyclohexane, isopa or ethylbenzene, which is used in an amount of at least 7% by weight based on the total weight of the solution. In the present invention, the amount used varies depending on the nature of the solvent used, but 8% ethylbenzene, 10% cyclohexane and 13% isopa are preferred. According to another important feature of the invention, the polymerization is selected from mono and / or di and / or triglycerides of stearates, or mixtures thereof polyethylene wax, additives comprising polyethylene glycol functional groups or additives based on silicone oils. The additive is carried out in the presence of 0.5 to 1% by weight based on the total weight of the additive. Di and / or triglycerides of stearates are compounds having a melting point of about 60 ° C. and a flash point of at least 150 ° C. and are marketed under the trade name ATMOS 150 by ICI AMERICA INC. Polyethylene wax is a horse (

It is a polymer wax marketed by Corporation. Polyethylene wax is a product having a dropping point of 70 to 80 ° C., a density of 0.86 to 0.88 and an average molecular weight of about 2,500; It is marketed by CdF CHIMIE. Silicone waxes are soluble in most organic solvents and are marketed by Dow Corning as "DOWCORNING 200 FLUID". The use of such additives makes the subsequent use of the obtained polymer of the finished product and the properties of the finished product useful. Preferably, these additives are added after polymerization in the internal mixer. For example, use a GK 5 type mixer sold by WERNER-PFLEIDERER. The melt flow index is especially adjusted by adding 1 to 3% of a plasticizer consisting of liquid paraffin, and the melt flow index is measured by the "ASTM Standard D 1238" method.

In order to use the method of the present invention, the polymerization reaction is carried out by known techniques. The autoclave used is equipped with a stirrer, a heating device and a cooling device. All reactants and additives used are chemicals used in bulk polymerization processes, for example antioxidants such as 2,6-di-tert-butylpara-cresol, 2,2-methylenebis (4-methyl-6 Tert-butyl phenol), octadecyl 3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, tri (2-decyl-4-hydroxy-5-tert-butylphenyl) Butane, triethylene glycol bis-3- (tert-butyl-4-hydroxy-5-methylphenyl) propionate] or a mixture of phenolic antioxidants and phosphates, polymerization initiators (eg benzoyl peroxide, di-3 Primary butyl peroxide, cyclohexane peroxide, tertiary butylperoxy isopropyl carbonate, dicumyl peroxide or tertiary butyl perbenzoate). All these additives are used in small amounts. In the case of the sulfate agent, less than 0.5% by weight based on styrene, and in the case of peroxide used alone or in combination, the amount is less than 0.3% by weight based on styrene. It is also possible to add other conventional additives such as paraffin oil up to 5% by weight relative to styrene. The use of these compounds makes it possible to produce polymers with good thermal and flow properties simultaneously and the polymers obtained can be readily used.

Except for the peroxides, all the reactants are heated at the same time with stirring at 40 ° C. for 3 hours to introduce the autoclave to dissolve the rubber in the other reactants. After this rubber-dissolving step the mixture is heated to a temperature of 80-250 ° C. for about 8 hours. The polymer obtained after the polymerization was heat treated and then devolatilized to granules.

The following examples illustrate the invention. All amounts are in parts by weight.

Example 1

A reactor used for bulk polymerization and equipped with a stirring device, a heating device and a cooling device, prepared by an anion process, having a content of 1-2 vinyl isomers of 10 to 12%, a molecular weight of 350,000, and styrene, α-methylstyrene two equivalents In a solution of 0.15 parts of a sieve, 8 parts of ethylbenzene, and 1 part of paraffin, 7.5 parts of polyburadiene rubber having a viscosity of 190 cps and 83.30 parts of styrene are charged to 5% by weight.

Next, 0.05 part of an antioxidant consisting of octadecyl 3- (3,5-di-tert-butyl-4-hydroxy phenyl) propionate is added. The reaction mixture is introduced into a heating step such that its final temperature reaches 145 ° C. after 7 hours 50 minutes.

After this heating step, 80 parts of the obtained solid was subjected to high temperature for 1 hour and 50 minutes. The polymer is granulated after devolatilization consisting of heat treating the polymer at 200 to 240 ° C. under vacuum of 730 to 740 mm Hg. The properties are summarized in the following table:

-VICAT points are measured according to standard DIN 53460,

Melt flow index is determined according to ASTM Standard D 1238,

Impact strength is measured using ASTM Standard D 256,

The gel content is calculated by stirring the resulting polymer in cold toluene and then centrifuging the mixture to determine the amount of gel insoluble in toluene. The dry material of the insoluble polymer is determined by milling the obtained gel under vacuum; The gel content for the sample represents the gel content,

The swelling index is equal to the mass ratio of the gel to the dry resin,

The particle size distribution is determined using the James method according to the Gato method described above,

Tensile emphasis is determined according to standard DIN 53455,

Resistance to stress-crack corrosion is determined in accordance with Standard AGK 31, which is implemented as standard by a group of practitioners consisting of refrigerators and manufacturers of thermoplastics; This standard represents the residual ratio upon stretching under stress of 75 kg / cm 2 for the injection formed specimens; In the case of halogenated hydrocarbons (freons) when the specimen is injection molded, the residual ratio should be at least 75%; When the sample is prepared by extrusion, the residual ratio should be at least 50%; Finally, this residual ratio should be at least 40% when the specimen is compression molded.

Example 2

Example 1 is repeated except that 6.85 parts of the same polybutadiene rubber, 10 parts of ethylbenzene, 81.08 parts of styrene, 0.1 parts of α-methylstyrene dimer and 1.97 parts of paraffin oil are used as in Example 1. The properties of the resulting polymers are summarized in the table below.

Example 3

Example 2 is repeated except that 0.2 parts and 80.98 parts of styrene are used instead of 0.1 parts of α-methylstyrene dimer. The properties of the resulting polymers are summarized in the table below.

Example 4

Styrene 79.18 parts, ethylbenzene 11 parts, α-methylstyrene dimer 0.15 parts, paraffin oil 3.85 parts, fully anionic polybutadiene rubber 5.8 parts, octadecyl 3- (3,5-di-tert-butyl-4-hydroxy Example 1 is repeated using 0.042 parts of phenyl) propionate. The properties of the resulting polymers are summarized in the attached table.

Example 5

Example 1 is repeated using 82.9 parts of styrene, 7.5 parts of ethylbenzene, 0.10 part of α-methylstyrene dimer, 2.3 parts of paraffin oil, 1 part of a mixture of glycerol mono and distearate and 6.2 parts of polybutadiene. The properties are summarized in the attached table.

Example 6

Example 1 is repeated using 78.06 parts of styrene, 6.82 parts of rubber, 13 parts of isopa, 0.15 parts of α-methylstyrene dimer, 1.97 parts of oil and 0.5 part of a mixture of glycerol mono and distearate. The properties are summarized in the attached table.

Example 7

79.18 parts of styrene, 0.042 parts of antioxidant sold under the trade name IRGANOX 1076, 3.83 parts of paraffin oil, 5.8 parts of anionic polybutadiene, 11 parts of ethylbenzene, 0.10 parts of α-methylstyrene dimer and octadecyl 3- (3,5- Example 1 is repeated using 0.042 parts of di-tert-butyl-4-hydroxyphenyl) propionate.

Example 8

Styrene 83.69 parts; 7.5 parts of ethylbenzene; 0.083 parts of α-methylstyrene dimer; 1.91 parts of paraffin oil; Example 1 is repeated using 0.5 parts of polyethylene wax and 6.82 parts of anionic polybutadiene having an average molecular weight of 2500, a viscosity of 60 to 100cp, a density of 0.86 and a dropping point of 70 to 80 ° C at 120 ° C. Its properties are summarized in the table.

Example 9 (Comparative Example)

The following amounts of reactants were used to obtain the product:

Styrene 83.69;

7.5 parts of ethylbenzene,

6.82 parts of polybutadiene consisting of a mixture (mixing ratio 50:50) of anionic polybutadiene (1,2 vinyl 10-12%) and Ziegler polybutadiene (1-4 cis isomer 97%) instead of single anionic polybutadiene,

0.073 parts of -α-methylstyrene dimer,

1.91 parts of paraffin oil.

Example 10

Polymers are prepared from the following components:

Styrene 83.69;

7.5 parts of ethylbenzene,

6.82 parts of a polybutadiene rubber obtained by an anion process, having a 1-2vinyl isomer content of 10 to 12%, a molecular weight of 350,000, and a viscosity of 190 cps for a 5% by weight solution in styrene,

0.083 parts of -α-methylstyrene dimer,

1.91 parts of paraffin oil,

0.5 parts of synthetic wax having a melting point of 140 ° C., sold under the trade name of “NOPCOWAX 22 DS” by Diamond Shamrock Co., Ltd., and summarized in the table.

Example 11

Example 10 is repeated except that one part of the wax sold under the trade name " POLYWAX 2000 " The obtained polymer properties are summarized in the table.

Example 12

Example 10 is repeated instead of NOPCOWAX 22 DS wax with one part of polyethylene wax having an average molecular weight of 2500, a viscosity of 60 to 100cp, a density of 0.86 and a dropping point of 70 to 80 ° C at 120 ° C. The obtained polymer properties are summarized in the table.

Example 13

Example 10 is repeated using 1 part of silicone oil sold by Dow Corning under the trade name "DOW CORNING 200 FLUID" in place of 0.5 part of wax. The properties of the obtained product are shown in the table.

Example 14

Example 10 is repeated using 0.5 parts of the solid polymer wax "800" sold by Hulse in lieu of silicone oil. The properties of the obtained product are shown in the table.

Example 15 (Comparative Example)

The polymer is prepared from the following components:

83.70 parts of styrene,

7.5 parts of ethylbenzene,

0.073 parts of -α-methylstyrene dimer,

1.91 parts of paraffin oil,

6.82 parts of anionic polybutadiene having a solution viscosity of 95 cps and an average molecular weight of 273000 and consisting of 11% of 1-2 vinyl isomers.

Example 16

Use the following ingredients:

-Styrene 81.03,

10 parts ethylbenzene,

6.85 parts of the same polybutadiene rubber as in Example 1,

0.10 part of -α-methylstyrene dimer,

1.97 parts of paraffin oil,

0.05 parts of an antioxidant based on octadecyl 3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate,

0.5 parts of a mixture of glycerol mono and distearate.

Example 17

Use the following ingredients:

-Styrene 81.03,

10 parts of ethylbenzene,

6.85 parts of the same polybutadiene as in Example 1,

0.10 part of -α-methylstyrene dimer,

1.97 parts of paraffin oil,

0.5 parts of silicone oil.

Example 18

Example 1 is repeated by using a mixture consisting of diphenyl 1,3 butadiene, cis-diphenylcyclobutene, trans-diphenylcyclobutene, methylphenylindan and diphenylcyclobutane instead of α-methylstyrene dimer.

Its properties are summarized in the table.

The abbreviations in the table are as follows:

-T.S. : The tensile strength

-M: Modulus

-B.S. : Fracture stress

-Y.S. : Yield stress

-E.B. : Elongation at break

-R.E. : Residual elongation

-E.S. Extruded specimen

-M.S: molded sample

Oil resistance was determined with LIVIO ^R olive oil.

The size of the extruded specimens was 200 × 20 × 2 mm.

The stress-crack corrosion resistance is expressed as percent residual fracture elongation, as in the following equation:

Claims (1)

All rubber solutions in styrene containing 7 to 10% by weight of anionic polybutadiene rubber having a proportion of 1-2 vinyl isomers of 10 to 12%, a molecular weight of 300,000 or more, and a viscosity of 140 cps or more with respect to a 5% solution in styrene Α-methylstyrene dimer or N-dodecyl mercaptan, tertiary dodecyl mercaptan, diphenyl 1,3 butadiene, cis-ciphenylcyclobutene, trans- Cyclohexane and isopha in an amount of 7% by weight or more in the presence of a compound selected from diphenylcyclobutene, methylphenylindane, diphenylcyclobutene or a mixture composed of one or more of the above compounds and in the total weight of all components present in the solution; or Mono or di or triglycerides of stearates or mixtures thereof, polyethylene wax, polyethylene glycol functionality in the presence of ethylbenzene Improved stress-cracking, characterized in that the polymerization is carried out by carrying out the polymerization reaction using an additive selected from the group consisting of an additive containing a silicone oil or an additive based on a silicone oil with respect to the weight of all components in the solution. A process for the preparation of rubber-modified styrene polymers, which exhibits good properties and good low temperature properties.