SE502757C2 - Polymer composition containing linear copolymers of alternating polydiene segments and polyvinyl aromatic segments and process for their preparation - Google Patents

Abstract

1. CASE 2967 "POLYMERIC COMPOSITIONS AND METHOD FOR PREPARING THEM" New polymeric compositions comprising: (a) a linear copolymer constituted by four alternating blocks, which can be represented by the formula (I) or (II) B1-T-A1-B2-A2 (I) or B1 A1-B2-T-A2 (II) wherein: B1 and B2 are polydienic blocks, preferably polybutadienic blocks; A1 and A2 are polyvinylaromatic blocks and preferably polystyrenic blocks; T is a portion of random copolymer formed by dienic and vinylaromatic monomer units; (b) a linear copolymer constituted by two blocks, which can be represented by the formulae (III) or (IV) B3-T-A3 (III) or B3-A3 (IV) wherein: B3 is a polydienic block; A3 is a polyvinylaromatic block; 2. and T has the above seen meaning. The polymeric composition, which can be blended with polystyrene, can be obtained both by blending the individual components, and by means of novel and original synthesis processes which make it possible both (A) and (B) components to be obtained simultaneously. The polymeric compositions according to the instant invention are suitable for all of those uses in which characteristics of impact strength, transparence and processability are required.

Description

This is the case with the linear block copolymers which consist of alternating blocks of polydienes and polyvinyl arenes, with a special structure and distribution of the individual segments, and with a structural formula according to the (I) or (III) type, which exhibits an extremely favorable balance between physical and mechanical characteristics.

Such block copolymers, as well as derivatives thereof, are described by the applicant in Swedish patent application 8704292-5 and in a simultaneous patent application.

The blending of block copolymers both with each other, and with impact-resistant and non-impact-resistant polystyrene to achieve resins with improved properties is known in the art.

Compositions and / or block copolymers characterized by the use of polymeric structures suitable for all those uses in which transparent and impact resistant polystyrene have been used in the past, or are still in use, are known from e.g.

BP-A-1 130 770, BP-A-1 335 077 and US-A-4 086 298.

However, the copolymers according to these references do not exhibit an optimal balance of theological properties, impact strength and transparency.

Such a balance of the properties can be further modified with the possible use of polystyrene which, on the one hand improves the optical characteristics, on the other hand reduces the impact strength of the compositions thus obtained.

The disadvantages of the prior art are overcome by the polymeric co-positions according to the present invention, which consist of mixtures of the two block copolymers according to the general formulas (I) or (III) and (II) or (IV), as described above. .

Accordingly and in accordance with a first object, the present invention relates to novel polymeric compositions comprising: (a) from 40 to 90% by weight of a block copolymer of the general formula (I) or (III); (b) from 10 to 60% by weight of a block copolymer of the general formula (II) or (IV), in which the symbols A, A2, A3, B, Bz, B, and T have the meanings given above. delsema. The polymer compositions according to the present invention are characterized in that the weight part molecular weight of the four-segment copolymer of formula (I) or (III) is comprised in the range from 50,000 to 300,000, while the weight part molecular weight of that of two segments The existing copolymer is in the range of from 20,000 to 150,000.

In the same composition, the weight percentage of the statistical segment T is included in the range from 5 to 50%, preferably from 10 to 25%, in comparison with the total amount of the two copolymers which constitute the mixture.

In the same grain position, the total amount of vinyl aromatic monomer units is included in the range from 60 to 90% by weight, the remainder being diene monomer units.

In the above definitions, segments A1, A2, A, and B1, B, and B are constituted in practice pure segments; i.e. they consist almost entirely of vinylar and diene units. In the preferred embodiment, segments B1, B, and B are polystyrene segments and T is a styrene-butadiene random copolymer.

Still in the preferred embodiment, the total content of diene units in the polymeric composition is in the range from 20 to 30% by weight, and the average molecular weight of the 4-block copolymer is in the range from 100,000 to 200,000; and the average molecular weight of the 2-block copolymer is included in the range from 40,000 to 100,000. To this composition, a further polystyrene resin, such as e.g. polystyrene or impact-resistant polystyrene is added in such an amount that does not damage the combination of properties of the binary composition.

Polymeric compositions in accordance with the present invention represent an improvement in the properties, over the block copolymers of formula (I) or (III), considered on an individual basis.

The linear block copolymer consisting of four alternating blocks which correspond to the general formula (I) or (III) in accordance with the present invention can be obtained by polymerization in an organic solvent to which teachable amounts of optional additives of an aliphatic or cycloaliphatic polar compound selected from 502,757 -4 ethers or arnines, at temperatures ranging from 30 ° C to 150 ° C and under pressures equal to, or greater than, atmospheric pressure, in the presence of said alkyl metal or aryl metal initiators, those commonly used in polymer synthesis according to the living anionic polymerization method.

Such an oxygen route is shown in the Swedish patent application 8704292-5 which shows such copolymers and the method for producing them. In contrast, the 2-block copolymers which correspond to the above formulas (II) or (IV) can be synthesized according to methods known in the art, as well as using the same synthetic procedure known from the above patent application, limiting the reaction. to the first step. For the synthesis of resin polymers of formula (II), preferably measured amounts of butadiene and styrene are fed to a reactor as a mixture with each other, and the polymerization is carried out in a solution of a hydrocarbon, with a suitable initiator for the living anionic polymerization, until the monomer conversion is total or substantially total; in this way a living 2-block copolymer B, - T - A is formed, which consists of non-pure segments, i.e. of segments linked to each other by a copolymer chain part, which consists of statistically linked monomer units of butadiene and styrene.

The polymer formed is recovered after a preliminary quenching of the living active centers, by feeding a compound with the recovery of the polymer material carried out in accordance with known methods, such as e.g. by evaporating the solvent and drying the polymer (steam evaporating the solvent).

The copolymer of formula (IV) is obtained by anionic polymerization, with sequential addition of the monomers according to the prior art.

The consumers of the polymeric compositions in accordance with the present invention may be mixed and formulated in accordance with modalities and routes well known in the art. Then e.g. the ingredients are mixed in a molten state and extruded or mixed in a Banbury-type mixer or they can be mixed in the form of solutions. The applicant 502 757 _ 5 _ have also developed - and they constitute a further object of the present invention - new and special processes which make it possible to produce the two components simultaneously using a single synthesis process.

According to such a process, the synthesis is carried out according to the following steps: (1) A first step during which a mixture is copolymerized in the presence of initiators, until the conversion of the monomers is substantially total, the mixture being composed of a vinyl aromatic monomer and a conjugated diene monomer in a non-polar solvent selected from the group of solvents in which polystyrene has an average molecular weight ranging from 30,000 to 120,000 is soluble at concentrations from 5 to 20% by weight. The initiators are alkyl-lithium compounds to produce a "living polymer system". The solution system may contain polar compounds (such as ethers, amines, etc.), in a maximum concentration of 0.1% by weight relative to the solvent. The weight percent of monomers fed into the mixture for the first reaction step in accordance with the process of the present invention is comprised in the range of from 30 to 60% by weight, relative to all monomers fed to the reaction. During the reaction shown above, a "living copolymer" of type B, - T - A1 is formed. (2) In a second step in which a certain percentage of the living active centers generated during the first reaction step are quenched by means of addition to the reaction system of compounds characterized in that they contain acidic hydrogen atoms (H 2 O, alcohols, etc.) in the chemical structure.

The amount of inactivators of the active centers added in the second step of such a process is included in the range of from 10 to 50 mol%, relative moles of initiator fed in the first step. (3) A third step, during which conjugated dienes are fed to the "living system" which comes from the second step and undergoes a total transformation. (4) A fourth step in which a vinyl aromatic monomer is imnatant and substantially completely converted. (5) A fifth step in which the "living aldive centers" are totally inactivated by ingesting a compound with an acid reaction. In this way the mixture of the two copolymers B, -TA, -B, -A is obtained. + ß, -'rA ,.

This process is carried out under the general conditions of temperature and pressure indicated above, i.e. at temperature values ranging from 30 ° to 150 ° C and under atmospheric or superatlinosphere pressure.

One of the variants which constitute alternative paths for the above process comprises at the end of the first step of polymerizing the monomer mixture a second step, in which an equal portion of initiator is fed.

Such a process leads to the formation of a further number of active centers, on which pure block copolymers previously described by means of the formula B, - T - A, are formed. In this case, the different sequential steps consist of: (1) synthesis of a pure service segment; (2) synthesis of a pure vinyl aromatic segment in sequence with the service segment; (3) feeding an additional equal portion of initiator; (4) feeding a mixture consisting of a diene monomer and a vinyl aromatic monomer. The amount of monomers fed in admixture with each other is included in the range of from 30 to 60% relative to the total amount of monomers fed to the reaction; (5) inactivation (quenching) of the living active centers by means of a compound containing acidic hydrogen atoms.

Using analogous procedures to those shown above, two polymer blends can be obtained: BI'AI'B2'T "A2 + BI'AI or BI'T'AI'B2'A2 + B2" A2.

The preferred initiators for the intended purpose are those belonging to the group consisting of both linear and branched alkyl-lithium compounds, and, among them, n-butyl-lithium and sec-butyl-lithium.

These initiators are commonly used in the various steps of the process in amounts ranging from 0.025 to 0.2 parts by weight per 100 parts of monomers subjected to polymerization.

The suitable solvents for the intended purpose are non-polar solvents and, among them, those in which the polyvinyl aromatic segments having a weight average molecular weight ranging from 50,000 to 200,000 are soluble; Among the most suitable of these, cyclohexane and benzene may be mentioned.

Said solvents may contain polar compounds (such as ethers, amines, etc.), the presence of which also causes, in addition to an increase in the reaction rate of the polymerization which takes place in the various steps, an increase in the weight of the random copolymer moiety. T; among these, tetrahydroferan is preferred.

The following experimental examples are illustrative and not limiting of the scope of the present invention.

Example 600 g of anhydrous cyclohexane, 55 g (99.9% pure) of styrene and 13 g (99.85% of pure) of butadiene are fed into a reactor with stirring of 1000 cms; the temperature of the pulp is increased up to 50 ° C, and 0.055 g of sec-butyl lithium (dissolved in n-hexane) is fed. 25 minutes later, the reaction mass reaches a temperature of 75 ° C and the conversion of the monomers is practically total. Then 0.009 g of pure methanol is added to the system, and 7 g of the bnmdiene are added. After 10 minutes, the mass opens the belt ss, and the conversion of butadiene is practically total.

Finally, 25 g of styrene, and 15 minutes later the conversion is practically total, the temperature of the pulp having reached the value of 90 ° C.

Inactivation of the living active centers is performed by adding 0.5 cc of H 2 O to the polymer solution. 1.0 g of triphenyl-nonyl-phosphate and 0.2 g of [pentaerythrityl-tetraalkyl, 5-di-tert-butyl-4-hydroxyphenyl-propionate]] are added to the polymer solution. The recovery of the polymer mixture is carried out by steam distillation of the reaction solvent and subsequent drying in a vacuum oven at 60 ° C for 24 hours.

The physical characteristics of the two components of the polymer blend are shown in Table 1. The mechanical and optical properties of compression-molded samples at 180 ° C are summarized in Table 2.

IahelLnLl Mw x 10 "* Mw x 10" * Total Segment MF! (4) Example (B, TA B, A2) (B, TA,) styrene styrene (g / 10 no. (1) (1)% (2)% (3) min) 1 140 80 80 68 4.5 Analysis GPC (1) LR. analysis (2) Demolition with OSO, (3) 2oo ° c, s kg (4) IaIxJLnLZ - Transparency% 92 - Tensile strength kg / cmz 230 - Elongation at break% 35 - Modulus kg / cm ”8000 - abrasion impact test at 23 ° c kg x cin / cm 2.5 Eaemmll 850 g of anhydrous cyclohexane, 37.5 g of styrene and 12.5 g of butadiene are fed into a stirred reactor of 2000 cms; the temperature of the system is increased up to s5 ° c, and 0.040 g of n-butyl-li fi um (dissolved in n-nexane) are fed. _ 9 _ 45 minutes later, the reaction mass reaches a temperature of 68 ° C and the conversion of the monomers is practically total.

Then, 0.032 g of n-butyllithium and 37.5 g of butadiene are added sequentially to the reaction mixture; after 20 minutes, the reaction mass reaches a temperature of 78 ° C and the conversion is practically total. 112.5 g of styrene are then added to the polymer solution and, 60 minutes later, the monomer conversion is complete.

The reaction is stopped by adding 2 g of methanol to the solution containing the polymer mixture. Addition of the antioxidant, and recovery and drying of the polymer are carried out in the same manner as in Example 1.

The physical characteristics of the two compounds in the polymer blend are shown in Table 3.

The mechanical and optical properties of samples which have been compression pressed at 180 ° C are summarized in Table No. 4. lalmlLnLí Example Mw x 10 * Mw x 103 Total Segment MFI No. (B, TA, B, A2) (B, TA,) styrene% styrene % (gl 10 min) 1 170 85 75 65 3.5 jlabçll n; 4 - Transparency% 86 - Tensile strength kg / cmz 165 - Elongation at break% 100 - Modulus kg / cm ”7000 - Notch impact test at 23 ° C kg x cm / cm 3.2 Exem-.Low 1.2 kg cyclohexane, 0.3 g tetrahydrofuran, 100 g of styrene and 45 g of butadiene are fed into a reactor with a capacity of 1.5 liters; the temperature of the reaction mass is raised to 150 ° C, and 0.12 g of n-butyl-u fi um (dissolved in n-nexane) is fed. 502 757 _ 10 _ 30 minutes later the reaction mass reaches the temperature of 80 ° C and the conversion of the monomers is substantially total.

Then 0.012 g of 11.0 and then 15 g of butadiene are added to the system. 10 minutes later, the reaction mass reaches the ternary parameters 90 ° C and the conversion of butadiene is total.

Finally, 40 g of styrene are added and after 15 minutes of reaction, the conversion is complete.

Before the solid polymer is recovered, the living active centers are inactivated by adding 2 g of isopropyl alcohol to the system.

After the addition of antioxidant as in Example 1, the recovery of the solid polymer is carried out by steam distillation of the solvent, and subsequent drying of the solid residue at 65 ° C for 24 hours.

The physical / chemical characteristics are reported in Table 5.

IaheILnLS Example Mw x 103 Mw x 103 Total Segment MFI no. (B, TA, B, A2) (B, TAz) styrene% styrene% (g / 10 min) 3 130 80 70 50 8.5 Eisenman 5 kg of the mixture as shown in Example 3 is mixed with 5 kg of commercial crystalline polystyrene [Mw (GPc) = 250 x 1031. Said pulp is fed to a twin-screw extruder equipped with a heated jacket. This procedure is repeated twice to allow the optimum mixture to be obtained; the material is then converted into granules (granules) with a length of 0.5 cm.

The properties of the compound thus prepared are determined on samples which have been compression molded at 180 ° C and are shown in Table No. 6. 502 757 _11- T ll No. - MFI g / 10 min 8.2 - Transparency% 90 - Tensile strength kg / cm 185 - Elongation at break% 100 - Modulus kg / cm ”12000 - Swath impact kg x cm / cm 3.5 fi xetrmLi 600 g of anhydrous cyclohexane and 30 g (99.84% pure) of butadiene are fed into a reactor with a capacity of 1 liter; the mass is heated to 60 ° C, and 0.09 g of seo-butyllithium is added. 20 minutes later, the polymerization of butadiene is total and the reaction temperature is approx. 60 ° C. 70 g (99.9% pure) of styrene are then added to the system, and the reaction is complete within a time of 20 minutes; during said time period the reaction mass reaches the temperature s2 ° c.

To the reaction mass is added successively 0.058 g of initiator (n-butyl-1 μm) and then a reaction mixture composed of 70 g of styrene and 30 g of butadiene.

The reaction takes place within 25 minutes and the temperature at the end of the reaction is 1 ° C. At the end of the process, 3 g of methyl alcohol are added to the system to inactivate the active centers.

To the polymer solution are added 0.8 g of TNPP (triphenyl-nonyl-phosphite) and 0.15 g of pentaerythuityl-thuaalkyl- (ε-di-tert-butyl-4-hydroxyphenyl) -propionate to the polymer solution.

The polymer is recovered by steam distillation of the solvent, and the recovered polymer is then dried in a vacuum oven at 60 ° C for 36 hours.

The physico-chemical characteristics and the mechanical characteristics of the polymer blend are given in Tables 7 and 8. 502 757 _ 12 _ lahgl! n; Example Mw x 10 * Mw x 10 "* Total Segment MFI No. (B, A, B, TAz) (B, TAz) styrene% styrene% (g / 10 min) 5 125 75 70 56 10 InbiJLnLß - Transparency% 85 - Elongation at break% 125 - Tensile strength kg / cmz 1,10 - Modulus kg / cmz 6800 - abrasion impact test at 23 ° c kg x cm / cm 5,0

Claims (12)

O 'CL F.) \' l (fl Q _ 13 _ PATENTKRAy A polymer composition containing at least one of the following two polymer blends BVT-A1-Bz-A, (I) and Bs 'T' A3 or B, -A, -B, -T-A2 (III) and wherein B1, B , and B, are polydiene segments, wherein B, is equal to or different from B, or BZ; A1, A, and A, are polyvinyl aromatic segments, wherein A, is equal to or different from A, or A2, and T is a copolymer chain moiety formed by random polymerization of a mixture of conjugated diene and vinyl aromatic hydrocarbon and wherein the two block copolymers (I ) or (III) amounts to 40 to 90% by weight of the two mixtures. Polymer composition according to Claim 1, characterized in that the linear 4-segment polymer (I) or (III) has an average molecular weight of from 50,000 to 300,000. Polymer grain position according to Claims 1 and 2, characterized in that the average molecular weight of the polymers identified by the formula (II) or (IV) is in the range from 20,000 to 150 ° () 0. Polymer composition according to the preceding claim, characterized in that in said composition the total amount of vinyl aroma fi monomer units is in the range from 60 to 90% by weight, the remainder up to 100% being diene monomer units. Polymer composition according to the preceding claim, characterized in that the diene segments consist of polybutadiene segments and that the polyvinyl aromatic segments consist of polystyrene segments. Method for preparing a polymer composition according to the preceding claim, characterized in that: in a first step, measured amounts of a diene and of a vinyl aromatic monomer are polymerized in a mixture with each other by living anionic polymerization , to a total or almost total monomer conversion; in a second step, a percentage ranging from 10 to 60% of the active living centers generated by the first reaction step is partially suppressed by the addition of compounds containing acid hydrogen ions; a measured amount of diene is added to the pulp from the second step, and is polymerized in a third step by anionic living polymerization until the conversion of the fed diene is total or substantially total; a measured amount of vinyl aromatic monomer is added to the product coming from the third step and polymerized, in a fourth step, until the conversion of the fed vinyl aromatic monomer is total or substantially total; the polymer mixture is recovered from the polymerization products from the fourth step, after a previous total elimination of the living active centers by means of a compound which contains acidic hydrogen atoms; in such a way that the polymer mixture consisting of the two polymers B, -T-Al-BfA, + B, -T-A, is obtained. Method for preparing the polymer composition according to claims 1 to 5, characterized in that: - in a first step polymerization takes place of measured amounts of conjugated dienes by means of anionic living polymerization up to total or almost total monomer conversion; in a second step, a measured amount of a vinyl aromatic monomer is added to the reaction mass coming from the first step and polymerized until the conversion of the fed vinyl aromatic monomer is total or substantially total; in a third step, the partial elimination is carried out in an amount comprised in the range from 10 to 60% of the active centers generated during the previous step by the addition of compounds containing acidic hydrogen atoms; In a fourth step, a mixture consisting of measured amounts of a diene and of a vinyl aromatic monomer is fed, and the polymerization is continued until the conversion of said monomers is complete or almost total; the produced mixture of polymers coming from the fourth step is recovered after the previous elimination of the living active centers by means of a compound which contains acidic hydrogen atoms, in such a way that the polymer mixture consisting of the polymers B, -A, -B2- T-A2 + B, -A, is obtained. Process according to Claims 6 and 7, characterized in that the polymerization is carried out in an organic, aliphatic or cycloaliphatic solvent at temperatures in the range from 30 to 150 ° C and at a pressure equal to or higher than atmospheric pressure. , in the presence of an alkyl metal or of an aryl metal. Process according to Claim 8, characterized in that the polymerization can be carried out in the presence of at least one linear or cyclic, polar compound selected from the group consisting of ethers or amines, in amounts ranging from 0.01 to 0.1 parts by weight relative to the solvent. Process according to Claims 6 and 7, characterized in that the solvent is cyclohexane and in that the reaction temperature is in the range from 50 ° to 10 ° C, the initiator is an alkyl lithium compound containing from 3 to 7 carbon atoms in the alkyl group, and in that said initiator is used. in amounts ranging from 0.025 to 0.20 parts by weight of 100 parts by weight of vinyl aromatic monomers. 11. ll. A method according to claims 6 and 7, characterized in that the diene consists of butadiene and that the vinyl aromatic compound is styrene. The use of polymer compositions according to claims 1 to 5 for the production of transparent and impact-resistant materials.