JPS5810412B2 - Polystyrene cutlet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a polystyrene resin that is transparent and has excellent impact resistance.

More specifically, the present invention relates to a method for producing a transparent styrenic copolymer having excellent impact strength by solution copolymerizing a vinyl-substituted aromatic hydrocarbon and a conjugated diene using an organolithium catalyst. be.

Hitherto, impact-resistant styrene polymers have been obtained by bulk polymerizing or suspension polymerizing a styrene solution of unvulcanized rubber, or by polymerizing in a bulk-suspension mixing system.

Although this kraft copolymer has significantly superior impact strength compared to polystyrene, it loses the beautiful appearance and transparency of polystyrene, and when the sheet is folded, it becomes flaky, cracks, or breaks. There are drawbacks such as.

Recently, a method for producing a block copolymer by anionic polymerization has been proposed as a method for obtaining a polystyrene resin having excellent impact resistance while taking advantage of the advantages of polystyrene.

Specific examples of these include Japanese Patent Publication No. 47-3252, 47
-A-B-A-B-A, A-B seen in No. 28915
-A-B-A-B-A complete block copolymer (A represents a vinyl-substituted aromatic hydrocarbon polymer block, B represents a conjugated diene polymer block).

). Also, Special Publication No. 48-2423, 48-200
No. 38 proposes a so-called 3-type tapering block copolymer having vinyl-substituted aromatic polymer blocks at both ends and mainly a conjugated diene polymer block in the middle.

However, although the block copolymers obtained in this way are transparent, they are still insufficient in terms of whitening cracks during bending operations, and are inferior to conventional high-impact polystyrene in terms of physical properties, especially impact strength. , is far inferior to polystyrene, and is comparable to or slightly superior to polystyrene.

In addition, when producing such a block copolymer, for example, if you want to obtain a polymer called A-B-A-B-A using an organic monolithium compound, it is necessary to add the monomer at least five times. However, there are drawbacks such as impurities contained in the monomer and solvent inactivating the catalyst and active polymer, making it impossible to avoid the formation of copolymers other than the intended block copolymer. It is disadvantageous for

Under these circumstances, the inventors of the present invention have conducted extensive studies with the aim of developing a strong polystyrene resin that is transparent, has excellent impact resistance, and does not cause any whitening cracks during bending operations. The present invention was achieved based on different concepts and knowledge.

That is, the conventional concept mainly concerns thermoelastomers, but this type of block copolymer requires a conjugated diene polymer block at the center and vinyl-substituted aromatic hydrocarbon homopolymer blocks at both ends. year,
Its tensile properties are said to depend on the cohesive force of the homopolymer of vinyl-substituted aromatic hydrocarbons at both ends; therefore, the vinyl-substituted aromatic polymer blocks at both ends have a certain length and uniformity required for cohesion. Sex was in demand.

In fact, all of the above four cited publications contain bis at both ends of the molecule.

It has a homopolymer block of nyl-substituted aromatic group.

Regarding transparency, there is little knowledge regarding this type of block copolymer.

The present invention was made based on knowledge regarding random copolymers of vinyl aromatic hydrocarbons and conjugated dienes, which could not be expected from such a concept, and completely new knowledge regarding transparency.

That is, in copolymerizing a vinyl-substituted aromatic hydrocarbon and a conjugated diene in an inert hydrocarbon solvent using an organolithium compound as a catalyst, the present invention provides (1) carbonization of a vinyl-substituted aromatic hydrocarbon using an organolithium compound as a catalyst; A random copolymer block of a vinyl-substituted aromatic hydrocarbon and a conjugated diene is formed in which the weight ratio of hydrogen and conjugated diene is 70/30 to 9515, and (2) a vinyl-substituted aromatic is added to the living polymer obtained in (1). Copolymerization under conditions such that a random copolymer block or a conjugated diene polymer block of a vinyl-substituted aromatic hydrocarbon and a conjugated diene is combined in a weight ratio of group hydrocarbon to conjugated diene of 30/70 to 0/100. (3) Add to the living polymer obtained in (2) a weight ratio of vinyl-substituted aromatic hydrocarbon and conjugated diene of 70/30.
Copolymerization is carried out under conditions such that a random copolymer of a vinyl-substituted aromatic hydrocarbon of 1 to 9515 and a conjugated diene is bonded.

This is a method for producing a polystyrene-based resin that is transparent and has excellent impact strength, and is characterized in that the total vinyl-substituted aromatic hydrocarbon is 70 to 95% by weight in the copolymer.

The copolymer obtained by the method of the present invention is first characterized by its transparency, which is almost as transparent as polystyrene.

The second feature is that it has excellent impact resistance, which is significantly improved compared to conventional block copolymers with a high styrene content, which only have impact strength comparable to polystyrene. The practical impact strength is superior to that of conventional high-impact polystyrene.

Furthermore, the copolymer obtained by the method of the present invention has excellent bending properties, and conventional block copolymers with a high styrene content crack when bent, and when completely bent to 180°, breakage or whitening cracks occur. On the other hand, the copolymer obtained by the method of the present invention is characterized in that the folded surface is completely transparent, and furthermore, it is strong enough to be sufficiently needleable after being bent several thousand times.

Furthermore, the copolymer obtained by the method of the present invention has a large tensile elongation at break, which is particularly noticeable in thin sheets processed for practical use.

Now, when a vinyl aromatic hydrocarbon and a conjugated diene are copolymerized using an organolithium compound as a catalyst, the copolymerization reactivity ratio is different, so the conjugated diene is polymerized first, and after the conjugated diene is consumed, the vinyl-substituted aromatic hydrocarbon is copolymerized. Block copolymers are produced as hydrocarbons polymerize.

Therefore, in order to obtain a copolymer consisting of a random copolymer block of a vinyl-substituted aromatic hydrocarbon and a conjugated diene as in the present invention, some kind of ingenuity is required.

Conventionally, two methods have been proposed for such randomization.

(1) A method of adding a polar compound that does not deactivate the organolithium compound as a randomizing agent.

(A typical example is Special Publication No. 36-15386.

) (2) A method of randomizing by operation during polymerization.

(A typical example is Special Publication No. 38-2394.

) To obtain a block copolymer consisting of a random copolymer of a vinyl-substituted aromatic hydrocarbon and a conjugated diene of the present invention,
Known randomization methods such as those described above can be applied, but are not limited to these as long as the vinyl-substituted aromatic hydrocarbon and conjugated diene in each block are randomly copolymerized.

The organolithium compound used in the method of the present invention is a hydrocarbon to which at least one lithium atom is bonded, such as n-propyllithium, isopropyllithium,
n-butyllithium, 5ec-butyllithium, ter
-butyllithium, n-pennallithium, methylcyclohexyllithium, Jnaumtoluene, benzyllithium, 1,4-dilithio-n-butane, 1,6-dilithio-n-hexane, 1,2-dilithio-1,2 -diphenylethane, etc., and particularly common ones include n-butyllithium and 5eC-butyllithium.

The copolymer obtained by the method of the present invention contains 70 to 95% by weight of vinyl-substituted aromatic hydrocarbon.

If the content of the vinyl-substituted aromatic hydrocarbon in the copolymer exceeds 95% by weight, the impact strength will decrease and the resin will break when bent, making it impossible to obtain a tough resin with high impact strength.

Furthermore, if the vinyl-substituted aromatic hydrocarbon in the copolymer is less than 70% by weight, the resin properties will be impaired, for example, the hardness will decrease and the rigidity will be lost, which is inconvenient when used as a sheet or film. .

The copolymer of the present invention has a random copolymer block of a vinyl-substituted aromatic hydrocarbon with a high content of vinyl-substituted aromatic hydrocarbon and a conjugated diene at both ends, and a vinyl-substituted aromatic hydrocarbon with a high content of conjugated diolefin in the middle. It consists of hydrogen and a random copolymer block of a conjugated diene, and the vinyl-substituted aromatic hydrocarbon content in the random copolymer block of a vinyl-substituted aromatic hydrocarbon at both ends and a conjugated diene is 70 to 95% by weight. .

If the vinyl aromatic hydrocarbon content is less than 70% by weight, the resin properties will be impaired and the hardness and tensile strength will be reduced.

Moreover, if it exceeds 95% by weight, whitening cracks are likely to occur during bending, resulting in a decrease in impact strength.

Next, the content of vinyl-substituted aromatic hydrocarbon in the random copolymer block of vinyl-substituted aromatic hydrocarbon and conjugated diene with a high content of intermediate conjugated diolefin, which constitutes the copolymer of the present invention, is 30% by weight or less. It is.

If the content of vinyl-substituted aromatic hydrocarbon in the intermediate random copolymer block of vinyl-substituted aromatic hydrocarbon and conjugated diene exceeds 30% by weight, impact strength decreases, cracks occur when bent, and breakage occurs. A tough resin with high impact strength, which is the objective of the present invention, cannot be obtained.

Vinyl-substituted aromatic hydrocarbons in the present invention include styrene, 0-methyl-styrene, p-methyl-styrene, m
- Menalustyrene, α-menaloustyrene, p-ethylstyrene, 1,3-dimethylstyrene, vinylnaphthalene, vinylanthracene, etc., and the most common one is styrene.

These may be used alone or in a mixture of two or more.

The conjugated diene in the present invention is a diolefin having 4 to 8 carbon atoms and a pair of conjugated double bonds, specifically 1,3-butadiene, 2-methyl-1
, 3-butadiene (isoprene), 2,3-thumenal-
1,3-butadiene, ■, 3-pentadiene, 1,3-
Hexadiene, etc., and the common ones are 1,
3-butadiene and isoprene.

These may be used alone or in a mixture of two or more.

Polymerization solvents in the method of the invention are aliphatic and aromatic hydrocarbons, such as cyclohexane, methylcyclohexane, ethylcyclohexane, 1,4-thumenalcyclohexane, benzene, ethylbenzene, toluene,
These include xylene and diethylbenzene, and these may be used alone or in a mixture of two or more.

The polymerization temperature in the method of the present invention is -40°C to 15°C.
0°C, but generally 40°C to 120°C.

The time required for polymerization is from 30 minutes to 24 hours, but generally from 1 hour to 10 hours.

It is desirable that the atmosphere surrounding the polymerization system be replaced with an inert gas such as nitrogen gas.

In addition, there may be impurities in the polymerization system that may deactivate the organolithium catalyst or active copolymer, such as water, oxygen, etc.
Care must be taken to avoid contamination with carbon dioxide gas, etc.

The transparent polystyrene resin with excellent impact strength obtained by the method of the present invention is an excellent resin that combines the advantages of conventional polystyrene and impact-resistant polystyrene, and is therefore useful in a wide variety of practical applications. products, such as food containers, films, etc., have been obtained.
The significance of the present invention is extremely large.

The resin of the present invention can be processed into a sheet or film in the same way as ordinary thermoplastic resins, and can be used as food containers, blister packaging materials, packaging films for fruits and vegetables, confectionery, and the like.

It can also be used in a blend with other thermoplastic resins, such as styrene resins and polyolefin resins.

Further, depending on the purpose, conventionally known fillers, reinforcing agents, etc. may be mixed and used.

Aspects of the present invention will be shown below with some Examples, but these are intended to explain the present invention in more detail and are not intended to limit the content of the present invention.

Example 1 An autoclave with an internal volume of 11 equipped with a stirrer and a jacket was washed, dried, and purged with nitrogen.

This Oh. While keeping the toclave at 50°C, 39.4.9 g of styrene and 4.4 g of butadiene were purified and dried in advance.
, 175.2 g of cyclohexane was supplied, and then a hexane solution of butyllithium was converted to 0.0 g in terms of butyllithium.
55 g of tetrahydrofuran and 8 times the molar amount of butyllithium were supplied to start the polymerization reaction.

One hour after adding the catalyst, 1.2 g of previously purified and dried styrene, 11.2 g of butadiene, and 49.6 g of cyclohexane were added. g of the mixture was added and the temperature was increased to 70°C to continue the polymerization.

After a further 1 hour, a mixture of 39.4 g of styrene, 4.4 g of butadiene, and 175.2 g of cyclohexane, which had been purified and dried in advance, was added, and the temperature was maintained at 50° C. again for 1 hour of polymerization.

After the polymerization reaction was completed, butyl hydroxytoluene (BHT) was added as a stabilizer to the resulting copolymer solution, and then
The copolymer was precipitated using excess methanol, and the precipitate was dried under reduced pressure (referred to as Example A sample).

Next, for comparison, a complete block copolymer was synthesized by the sequential addition method of monomers as described below.

40g of purified and dried styrene and 160g of cyclohexane were supplied to the same autoclave as above, and the hexane solution of butyllithium was 0.070 in terms of butyllithium.
g, polymerized for 30 minutes while keeping the temperature at 50'C,
Next, 20.9 g of purified and dried butadiene and 80 g of cyclohexane were added, polymerized at 70°C for 1 hour, and finally 40 g of purified and dried styrene and 160 g of cyclohexane were added.
was added and polymerized at 50°C for 1 hour.

The resulting copolymer solution was treated in the manner described above to obtain a copolymer (referred to as Comparative Example B sample).

Furthermore, for comparison, a type 3 decreasing block copolymer was synthesized by the method described below.

40 g of previously purified and dried styrene and 160 g of cyclohexane were supplied to the above-mentioned 11 autoclave, and the hexane solution of butyllithium was 0.0 in terms of butyllithium.
Add 7g, polymerize at 50°C for 1 hour, then pre-purify,
A mixture of 40 g of dry styrene, 20 g of butadiene, and 24.0 g of cyclohexane was added, and polymerization was continued for 1 hour while maintaining the temperature at 70°C.

The obtained copolymer solution was treated in the manner described above to obtain a copolymer (referred to as Comparative Example C sample).

The analytical values of these three samples were as follows.

Next, the obtained sample was evaluated for general physical properties, and the following results were obtained.

Example A obtained by the method of the present invention as seen from Table 2
The sample showed fully satisfactory results in all aspects such as tensile properties, impact strength, transparency, and bending properties, and especially in terms of impact strength and bending properties, it was better than conventional comparative examples B and C.
It is significantly superior to .

Further, although the sample of Comparative Example B, which is a complete block copolymer, has excellent tensile strength, it is inferior in impact strength and bending properties, and is not practical.

Furthermore, although Comparative Example C sample shows some improvement in bending properties compared to Comparative Example Sample B, it is clearly inferior to Example A sample obtained by the method of the present invention.

Example 2 38.6 g of styrene purified and dried in advance while keeping the autoclave used in Example 1 at 50°C: butadiene 4
．． 3g and 171.6g of dicyclohexane were supplied, and the hexane solution of butyllithium was converted to 0.3g in terms of butyllithium.
055. ! li' and tetrahydrofuran in a molar amount 9 times that of butyllithium were supplied to initiate the polymerization reaction.

One hour after adding the catalyst, 2.8 g of previously purified and dried styrene and 11.4 g of butadiene were added. ! ii', a mixture of 56.8 g of cyclohexane was added and the temperature was raised to 70° C. to continue polymerization.

After another hour, 38.6 g of pre-purified and dried styrene
, 4.3 g of butadiene, and 171.6 g of cyclohexane were added thereto, and polymerization was carried out for 1 hour while maintaining the temperature at 50'C.

The obtained copolymer solution was treated by the method of Example 1 to obtain a copolymer (referred to as Example D sample).

In addition, a copolymer having a styrene content of approximately 85% was synthesized using the same method and was designated as Example Sample E.

Next, for comparison, styrene was polymerized in cyclohexane at 50° C. for 1 hour using butyllithium as a catalyst to obtain polystyrene (referred to as Comparative Example F sample).

Furthermore, for comparison, a copolymer with a low styrene content was synthesized by the following method.

15g of pre-purified and dried styrene, 10g of butadiene
A mixture of 100 g of cyclohexane was supplied to the autoclave kept at 50° C., and 0.08 g of a hexane solution of butyllithium in terms of butyllithium and 8 times the molar amount of tetrahydrofuran as butyllithium were added to start the polymerization reaction. .

One hour after adding the catalyst, pre-purified and dried 20 g of sunalene, 30 g of butadiene, and 200 g of cyclohexane were added.
g, and the temperature was increased to 70° C. to continue polymerization.

(After 1 hour, 15g of pre-purified and dried styrene,
A mixture of 10 g of butadiene and 100 g of cyclohexane was added and polymerized at 50° C. for 1 hour.

The obtained copolymer solution was treated by the method of Example 1 to obtain a copolymer (referred to as Comparative Example Sample G).

The analytical values of these four samples were as follows.

*Measurement method is the same as in Example 1.

Next, the physical properties of the above four samples were evaluated and the following results were obtained.

Note that the evaluation method for physical properties is the same as in Example 1.

As is clear from Table 4, the Example and E samples obtained by the method of the present invention are excellent in all items such as transparency, impact resistance, bending properties, and tensile properties.

- Comparative Example F sample, which is polystyrene other than the strength tree invention, has excellent transparency and tensile strength, but has almost no impact resistance, poor bending properties, and cannot be said to be a strong resin.

Comparative Example G, which has a lower styrene content than the copolymer of the present invention, exhibits elastomeric properties rather than resinous properties.

That is, although it has excellent bending properties and tensile elongation, it has extremely low tensile strength and low hardness, making it inconvenient to use as a resin.

Claims (1)

[Claims] 1. In copolymerizing a vinyl-substituted aromatic hydrocarbon and a conjugated diene in an inert hydrocarbon solvent using an organolithium compound as a catalyst, (1) First, a vinyl-substituted aromatic hydrocarbon is copolymerized using an organolithium compound as a catalyst. Forming a random copolymer block of a vinyl-substituted aromatic hydrocarbon and a conjugated diene in which the weight ratio of the group hydrocarbon to the conjugated diene is 70/30 to 9515, Weight ratio of vinyl-substituted aromatic hydrocarbon and conjugated diene is 30/70
Copolymerization is carried out under conditions such that random copolymer blocks or conjugated diene polymer blocks of vinyl-substituted aromatic hydrocarbon and conjugated diene of 0/100 to 0/100 are combined, and (3) obtained in (2) Copolymerization is carried out under conditions such that a random copolymer block of a vinyl-substituted aromatic hydrocarbon and a conjugated diene is bonded to the living polymer in a weight ratio of 70/30 to 9515. and the total vinyl-substituted aromatic hydrocarbon is greater than 70% by weight and 95% by weight in the copolymer.
% by weight or less, a method for producing a polystyrene resin having excellent transparency and impact resistance.