JPH0625366A - Impact-resistant polystyrene resin - Google Patents

Abstract

PURPOSE:To obtain the subject resin useful as mechanical parts, etc., having excellent luster, injection moldability, cold flow characteristics, comprising a specific rubber composition and a polystyrene in a specific ratio. CONSTITUTION:The objective resin comprises 2-20wt.% rubber composition consisting of (A) 60-99 pts.wt. high cis-polybutadiene obtained by using a rare earth metal-based catalyst, having physical properties of >=90wt.% butadiene segment content and (B) 40-1 pts.wt. high trans-polybutadiene obtained by using a rare earth metal-based catalyst, having physical properties of >=5wt.% crystallinity at 25 deg.C and 98-80wt.% polystyrene.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition which can be preferably used as a rubber component of an impact-resistant polystyrene resin, and an impact-resistant polystyrene resin using this rubber composition.

[0002]

2. Description of the Related Art Conventionally, ABS resin has been mainly used for housings and mechanical parts of home electric appliances such as televisions and videos, and for housings of displays and keyboards of office automation equipment. For these applications, impact resistance and high gloss are required, and ABS resin is a resin that can sufficiently satisfy such requirements. However, ABS resin has a problem that it is expensive as compared with other more general-purpose resins such as polystyrene and polypropylene. For this reason, home appliance manufacturers and OA equipment manufacturers do not reduce product performance,
We are considering alternatives with cheaper resins.

One of such resins is a high impact polystyrene resin (HIPS). This resin has a considerably high impact resistance, is a resin excellent in injection moldability, and has a feature that the price is lower than that of the ABS resin. For this reason, HIPS has come to be widely used for television and video housings, etc., instead of ABS resin.

HIPS has a structure in which rubber particles such as polybutadiene having a diameter of 0.1 to 10 μm are dispersed in a continuous phase of polystyrene. Due to the absorption of impact energy by the rubber particles, HIPS exhibits a considerably high impact resistance. However, HIPS is lower in gloss than ABS resins and ordinary polystyrene resins, which has been an obstacle to further expanding the applications. HIP
It is widely known that when polybutadiene to be dispersed in S has a styrene monomer solution having a low viscosity, the particle size of the polybutadiene particles is reduced, thereby improving the gloss of HIPS.

It is also widely known that the easiest way to reduce the solution viscosity of polybutadiene is to reduce its molecular weight, which can improve the gloss of HIPS. However, lowering the molecular weight of polybutadiene not only lowers the solution viscosity, but also naturally lowers the solid viscosity. If the solid viscosity is reduced enough to develop excellent gloss performance, polybutadiene will deform due to cold flow (rubber flow for a long time due to its own weight or load when stored at room temperature). Will be caused significantly. This greatly limits the packaging or container of the polybutadiene product, increasing cost. Further, such a fluid polymer is difficult to handle, and there are problems such as increase in work and operation costs, and there is a limit to lowering the solution viscosity by naturally reducing the molecular weight of polybutadiene. It was

[0006] A method has already been attempted for obtaining HIPS having excellent gloss by reducing only the solution viscosity without deteriorating the cold flow property of polybutadiene, that is, without lowering the solid viscosity. As an example of this, there is a method disclosed in JP-A-61-148213. In this method, 1,3-butadiene is polymerized with an alkyllithium-based catalyst and then a branching agent such as tetrachlorosilane is reacted to obtain a HI using a branched low-cis polybutadiene.
Regarding PS. Branched polybutadiene exhibits a relatively low solution viscosity and high solid viscosity, with less problems in cold flow. In addition, HIPS obtained using this
Has improved gloss and impact resistance over conventional products.
However, there has been a demand for further improvement in impact resistance at low temperatures.

High-cis polybutadiene having a low solution viscosity and a high solid viscosity has also been developed by the so-called Ziegler catalyst technology containing transition metals such as nickel, cobalt and titanium as main components. This type of high-cis polybutadiene has a lower glass transition temperature than low-cis polybutadiene.
PS has the advantage of being excellent in low temperature impact resistance. However, in this kind of high-cis polybutadiene having a low solution viscosity, the branched structure of the polymer chain is mainly a short-chain branched structure and has many branched structures. There is a fundamental difference in the polymer chain structure from the low cis polybutadiene. Perhaps for this reason, the HIPS obtained using the same has been required to have further improvement in gloss performance.

Further, a composition of trans polybutadiene and a wide range of diene rubbers has been already known basically from JP-A-60-197749, and there is a description of high cis polybutadiene as one example of the diene rubbers. . However, there is no description of high trans polybutadiene and high cis polybutadiene according to the production method specified in the present application. Moreover, the impact-resistant polystyrene resin (H
There is no specific disclosure for use as IPS).

[0009]

DISCLOSURE OF THE INVENTION The present invention provides a high-impact polystyrene resin which is excellent in gloss and impact resistance using a rubber composition which hardly causes cold flow, and particularly excellent in impact resistance at low temperature. It is a thing.

[0010]

That is, the present invention provides (A) high cis polybutadienes obtained by using a rare earth metal-based catalyst and having the following structures:
60 to 99 parts by weight and the content of the butadiene segment is 90% by weight or more The bonding mode of the butadiene segment is in the following range 1,4-cis bond 75-99.5% 1,4-trans bond 22-0.5 % 1,2-bond 3 to 0% The weight average molecular weight is in the range of 50,000 to 500,000, and the molecular weight distribution represented by weight average molecular weight / number average molecular weight is 1.2 to.
Range of 3.5 (B) Crystalline high-trans polybutadienes obtained by using a rare earth metal-based catalyst and having the following structures and characteristics: 40 to 1 part by weight Content of butadiene segment is 90% by weight or more. The bonding mode of the butadiene segment is in the following range.

1,4-cis bond 12 to 0.5% 1,4-trans bond 80 to 99% 1,2-bond 8 to 0.5% Crystallinity at 25 ° C. is 5% by weight or more Weight average molecular weight Is in the range of 1 to 400,000, and the molecular weight distribution represented by weight average molecular weight / number average molecular weight is 1.2 to
It is an impact-resistant polystyrene resin composed of 2 to 20% by weight of a rubber composition in the range of 3.5 and 98 to 80% by weight of polystyrene.

The high cis polybutadiene used in the present invention is a rare earth metal (atomic number 21, 39 and 57).
To 71) based catalysts, preferably cerium group metal (atomic number 57 to 62) based catalysts, particularly preferably neodymium based catalysts. A preferable basic structure of a specific rare earth metal-based catalyst is (a) a rare earth metal compound represented by the general formula LnY ₃ (where Ln represents a rare earth metal and Y represents a reaction residue of an organic acid), (b) ) An organoaluminum compound and (c) a halogen compound. The organic acid that constitutes the rare earth metal compound is an organic compound having active hydrogen that can be substituted with the rare earth metal, and examples thereof include carboxylic acid, alcohol, thioalcohol, amine, organic phosphoric acid compound, and organic phosphorous acid compound. You can Specific polymer production techniques using this type of catalyst include, for example, the processes disclosed in JP-B-41-21995, JP-A-55-66903 and JP-A-60-23406.

The high-trans polybutadiene used in the present invention is a rare earth metal (atomic number 21, 39 and 57 to 71) type catalyst, preferably a cerium group metal (atomic number 57 to 62) type catalyst, particularly preferably a lanthanum type catalyst. Obtained. A preferable basic constitution of a specific rare earth metal-based catalyst is (a ′) general formula LnY ′ ₃ (here, Ln
Is a rare earth metal, Y ^′ represents a reaction residue of an organic acid), and (b ′) an organomagnesium compound. The organic acid that constitutes the rare earth metal compound is an organic compound having active hydrogen that can be substituted with the rare earth metal, and examples thereof include carboxylic acid, alcohol, thioalcohol, amine, organic phosphoric acid compound, and organic phosphorous acid compound. You can As a specific technique for producing a polymer using this type of catalyst, for example, JP-A-61-196
No. 11, and the method disclosed in JP-A No. 61-97311.

The high-cis polybutadiene and the high-trans polybutadiene constituting the rubber composition of the present invention include butadiene alone or a small amount of other conjugated gen monomer in the presence of the above-mentioned composite catalyst containing a rare earth metal as a main component. It can be obtained by bulk polymerization or solution polymerization in a hydrocarbon solvent by coexisting with a vinyl aromatic compound monomer. If necessary, a long chain branch can be introduced by coupling the polymer chain end by a known method after the polymerization. For example, the polymer terminal can be coupled by adding an organic compound having a carbonyl group after polymerization, particularly a compound having an ester group of a carboxylic acid in the molecule or a carbonic acid ester compound.

The content of high cis polybutadiene in 100 parts by weight of the polymer component of the rubber composition of the present invention is 60-.
It is in the range of 99 parts by weight, preferably 80 to 97 parts by weight, particularly preferably 90 to 95 parts by weight, the balance of the polymer component being crystalline high trans polybutadiene. When the content of high-cis polybutadiene is less than 60 parts by weight, the low temperature impact strength of HIPS obtained by using the same is lowered, which is not preferable, and when the content of crystalline high trans polybutadiene is less than 1 part by weight, the cold content is low. The effect of improving the flow is not sufficient, which is also not preferable.

High-cis polybutadiene and high-trans polybutadiene, which are the polymer components in the rubber composition of the present invention, are homopolymers of butadiene,
Generally, it is most preferable, but it may be a copolymer with another monomer. Examples of the monomer that can be copolymerized with butadiene include a conjugated gen monomer and a vinyl aromatic monomer that are copolymerizable with butadiene other than butadiene. However, the weight content of the butadiene segment contained in the polymer must be 90% or more, preferably 95% or more, and particularly preferably 99% or more. If the weight content of the butadiene segment is less than 90%, the HI obtained using this is the object of the present invention.
The performance of the rubber composition deteriorates in terms of the balance between the gloss of PS and impact resistance, and in some cases, the cold flow property of the rubber composition is unfavorable.

Furthermore, the bonding mode of the butadiene segment of the high cis polybutadiene in the polymer component of the rubber composition of the present invention has a 1,4-cis bond content of 75 to 99.
5%, preferably 90-99.5%, particularly preferably 9
It is in the range of 5 to 99.5. Generally, HIPS has an inverse correlation between gloss and impact resistance, depending on the rubber particle size. When the 1,4-cis bond content is less than 75%, the performance is deteriorated due to the balance between gloss and impact resistance of the HIPS obtained using this, which is not preferable. The 1,2-bond content is preferably 3% or less, more preferably 2% or less,
It is particularly preferably 1% or less. 1,2-bond content is 3
%, The performance is deteriorated due to the balance between gloss and impact resistance of the resulting HIPS, which is not preferable. Also, the residual bonding mode of the butadiene segment is 1,4-
It is trans-coupled and is in the range of 22-0.5%.

The bonding mode of the butadiene segment of the high trans polybutadiene in the polymer component of the rubber composition of the present invention has a 1,4-trans bond content of 80 to 99.
%, Preferably 85-95%, particularly preferably 87-9
It is in the range of 3%. 1,4-trans bond content is 80%
When it is less than 1, the cold flow property of the rubber composition is deteriorated (cold flow tends to occur), which is not preferable. Further, if the trans bond content is too high, the high trans polybutadiene is extremely crystallized, and the solubility of the rubber composition in the styrene monomer during the production of HIPS is lowered, which is not preferable. The 1,2-bond content is 8 to 0.5%, particularly preferably 6 to
It is in the range of 1%. If the 1,2-bond content exceeds 8%, the performance is deteriorated due to the balance between gloss and impact resistance of the resulting HIPS, which is not preferable. The remaining bonding mode of the butadiene segment is 1,4-cis bond,
It is in the range of 12 to 0.5%.

The high trans polybutadiene in the polymer component of the rubber composition of the present invention has a crystallinity at 25 ° C. of 5% by weight or more, preferably 10 to 60% by weight, particularly preferably 15 to 50% by weight. Is the range. When the crystallinity is less than 5% by weight, the cold flow property of the rubber composition is deteriorated, which is not preferable. Further, if the crystallinity is extremely high, the solubility of the rubber composition in the styrene monomer during the production of HIPS decreases, which is not preferable.

The high-cis polybutadiene in the rubber composition of the present invention has a weight average molecular weight of 50,000 to 500,000, preferably 100,000 to 400,000, and particularly preferably 150,000 to 350,000. If the weight average molecular weight is less than 50,000, the impact resistance of the HIPS obtained using the same is lowered, which is not preferable.
When it exceeds 0,000, gloss is deteriorated, which is not preferable. Also,
The molecular weight distribution represented by the ratio of the weight average molecular weight / number average molecular weight of the polymer component is 3.5 or less, preferably 3.0 or less, and particularly preferably 2.5 or less. When the molecular weight distribution exceeds 3.5, the gloss of HIPS obtained by using the same decreases, which is not preferable. Further, the molecular weight distribution of the high cis polybutadienes is generally preferably narrow,
A distribution of less than 1.2 was difficult to achieve in rubber manufacturing technology.

The weight average molecular weight of the high trans polybutadiene in the rubber composition of the present invention is in the range of 1 to 400,000, preferably 2 to 350,000, particularly preferably 5 to 300,000. If the weight average molecular weight is less than 10,000, the impact resistance of the HIPS obtained using the same is lowered, which is not preferable.
If it exceeds 10,000, the gloss is deteriorated, which is not preferable. The molecular weight distribution represented by the weight average molecular weight / number average molecular weight ratio of the polymer component is 3.5 or less, preferably 3.0 or less, and particularly preferably 2.5 or less. When the molecular weight distribution exceeds 3.5, the gloss of HIPS obtained by using the same decreases, which is not preferable. Further, it is generally preferable that the molecular weight distribution of the high-trans polybutadiene is narrow, but it is difficult to achieve a distribution of less than 1.2 in terms of rubber manufacturing technology.

Furthermore, in the rubber composition of the present invention, in addition to the polymer component specified in the present invention, additives such as stabilizers, antioxidants, and ultraviolet ray inhibitors that can be added to ordinary rubber products. Can of course be added to achieve the same known purpose. In the rubber composition of the present invention, the mixing method of each polymer component and additive is not particularly specified. After polymerization, both can be solution mixed as a polymerization solution, or can be mixed in a lump by a mechanical mixer.

In the high impact polystyrene resin (HIPS) of the present invention, the rubber composition is 2 to 20, preferably 5 to 15 with respect to polystyrene of 98 to 80, preferably 95 to 80% by weight. Must be weight percent. 2% by weight of rubber composition
When it is less than 0.1%, the resulting HIPS does not have sufficiently improved impact resistance, and when the proportion of the rubber composition exceeds 20% by weight,
The mechanical strength and rigidity of HIPS are significantly reduced, which is not preferable.

In addition to the rubber composition specified in the present invention, the HIPS of the present invention includes a so-called Ziegler containing, as a main component, a butadiene-based polymer which does not meet the requirements of the present invention, for example, known transition metals such as nickel, cobalt and titanium. High-cis polybutadiene obtained by a catalyst, polybutadiene having a 1,4-cis content of the butadiene segment of less than 75%, and rubber such as styrene-butadiene rubber, ethylene-propylene rubber, ethylene-vinyl acetate copolymer rubber, and acrylic rubber. You can also add ingredients. But,
These rubber components cannot fully exhibit the effects of the present invention unless the amount is limited to 30 parts by weight with respect to 100 parts by weight of the rubber composition of the present invention.

The HIPS of the present invention is a bulk polymerization method or a bulk-polymerization method.
Known polymerization methods such as suspension method and suspension polymerization method, for example, JP-A-5-
It can be produced by the method described in JP-A-7-143313. Further, during the production of HIPS, a vinyl-based monomer that is radically copolymerizable with styrene, for example, a substituted aromatic vinyl compound such as α-methylstyrene, or a methacrylic acid ester such as methyl methacrylate may be used as a comonomer. Such a vinyl-based monomer can be usually used up to 30 parts by weight based on the styrene monomer.

The high impact polystyrene resin (HI of the present invention
PS), in addition to the polymer component specified in the present invention,
Additives that can be added to ordinary HIPS products, such as polysiloxane compounds, stabilizers, antioxidants, and UV inhibitors, can of course be added to achieve the same known purpose.

[0027]

EXAMPLES The methods for preparing and measuring the polymers used in the examples of the present invention are shown below. 1. Preparation of high cis polybutadiene The high cis polybutadiene prepared by the rare earth metal catalyst used in Examples and Comparative Examples was prepared as follows.

Cyclohexane is used as a solvent for 1,3-butadiene monomer and 2-isopropyl-5 is used as a polymerization catalyst.
Polymerization was carried out using the neodymium salt of methylhexanoic acid, diisobutylaluminum hydride and ethylaluminum sesquichloride. Polymers having different structures were polymerized by controlling the composition of the catalyst, the amount used, and the additives.

After the polymerization, butyl trimellitate was added as needed to couple the ends. BHT after the reaction
[2,6-Bis (tert-butyl) -4-methylphenol] was added to stop the reaction, and then the solvent was heated to volatilize and the polymer was recovered. Table 1 shows the structure of the obtained high-cis polybutadiene (polymer species C1 to C7). 2. Preparation of high-trans polybutadiene High-trans polybutadienes using rare earth metal-based catalysts used in Examples and Comparative Examples were prepared as follows.

The 1,3-butadiene monomer was polymerized using cyclohexane as a solvent and a lanthanum salt of di-2-ethylhexyl phosphoric acid and dibutyl magnesium as a polymerization catalyst. Polymers having different structures were polymerized by controlling the composition of the catalyst, the amount used, and additives such as organolithium. The obtained high-trans polybutadiene solution was added with BHT as a stabilizer, and then the solvent was heated to be volatilized to recover the polymer.

The structure of the obtained high-trans polybutadiene (polymer species T1 to T7) is shown in Table 2. Analysis of polymer structure The structure of the obtained polymer was analyzed by the following method. (1) The bonding mode of the butadiene segment was determined by measuring with an infrared spectrophotometer and processing the data by the method of Morello. (2) The molecular weight was measured by gel permeation chromatography using THF (tetrahydrofuran) as a developing solvent. (3) The crystallinity of high-trans polybutadienes was calculated from the endothermic amount of a differential thermal analyzer (DSC). 4. Mixing method of rubber composition As a mixing method of rubber components such as high-cis polybutadienes and high-trans polybutadienes, an open roll heated to about 100 ° C was used to knead and mix. 5. Cold flow measuring method of rubber composition and comparative polymer Rubber block containing no bubbles such as air is 3 cm × 3 cm, height 1
Cut out to a 0 cm cube pillar and stick the bottom surface (3 cm x 3 cm surface) perpendicular to the slope with an inclination of 30 degrees. Over time, the rubber block gradually falls or deforms due to its own weight. The cold flow characteristics were evaluated based on the state after one day.

Criteria for evaluation ○: Almost no change in shape is observed (good) Δ: Partial deformation and flow observed (somewhat inferior) ×: Significant deformation and flow, overall change in shape Permitted (inferior) 6, Preparation of HIPS 1 liter separable flask was replaced with nitrogen gas, 552 g of styrene monomer was added, 48 g of the rubber composition to be evaluated was added and dissolved, and the rubber composition contained 8% by weight. A styrene solution was used. 0.2 g of n-dodecyl mercaptan was added to this solution, and the mixture was stirred at 135 ° C. and prepolymerized until the polymerization rate of styrene reached 30%. Then, this solution was charged into a 2-liter autoclave, and 700 ml of a 0.5% by weight polyvinyl alcohol aqueous solution was added,
1.4 g of benzoyl peroxide and 0.7 g of dicumyl peroxide were added, and polymerization was further carried out under pressure. The polymerization was carried out at 100 ° C. for 2 hours, then at 125 ° C. for 3 hours, then at 140 ° C. for 2 hours while stirring the autoclave.

A bead-like polymer was collected from the obtained reaction product mixture by filtration, washed with water, dried and then pelletized by an extruder to obtain about 500 g of a pellet fat of HIPS of the present invention. 7. HIPS performance measurement The obtained pellet-shaped HIPS was injection-molded to prepare a test piece for a physical property test, and the Izod impact strength, flexural modulus, and gloss were measured. Izod impact strength is JIS K
According to 7110 (notched), 25 ℃ and -30 ℃
It was measured at. The flexural modulus and gloss are based on JIS
It was measured according to K7203, JIS Z8741 (incident angle 60 °).

[0034]

Examples 1 to 3 and Comparative Examples 1 to 4 In Examples 1 to 3 and Comparative Examples 1 to 3, the composition ratio of high cis polybutadiene and high trans polybutadiene in the rubber composition was changed as shown in Table 3. Shows the composition effect. The high cis polybutadiene species used here is C1 (see Table 1),
The high trans polybutadiene species is T2 (see Table 2). The evaluation results are shown in Table 3.

In Comparative Example 4, the composition shown in Table 3 was prepared by using JSR-BR01 (product rubber manufactured by Japan Synthetic Rubber Co., Ltd.) in high cis polybutadiene and a barium catalyst in high trans polybutadiene. Used in
evaluated. Here, the high trans polybutadiene was prepared using a composite catalyst composed of barium dinonyl phenoxide, lithium magnesium tributyl and triethylaluminum. (According to the method of JP-A-55-38827) The resulting high-trans polybutadiene has the following binding modes: 1,4-trans 80%, 1,4-cis 14%, 1,2-bond 6%, Weight average molecular weight 120,000,
The number average molecular weight was 75,000 and the crystallinity was 4%.

[0036]

Examples 4 and 5 and Comparative Examples 6 and 7 In Examples 4 and 5 and Comparative Example 6, the high cis polybutadiene species listed in Table 4 and the high trans polybutadiene species T2 (see Table 2) were used in the rubber composition. ), The high cis polybutadiene / high trans polybutadiene = 9
The evaluation was made in the 2/8 weight composition ratio. In Comparative Example 7, diene 35A (low cis polybutadiene manufactured by Asahi Kasei Corporation) was used instead of high cis polybutadiene. The evaluation results are shown in Table 4. In addition, in order to facilitate understanding, Example 1 is reprinted in the table.

[0037]

Examples 6 and 7 and Comparative Examples 8 and 9 In Examples 6 and 7 and Comparative Example 8, C1 (see Table 1) as the high cis polybutadiene species and Table 5 as the high trans polybutadiene species in the rubber composition. And the high cis polybutadiene / high trans polybutadiene = 9
The evaluation was made in the 2/8 weight composition ratio. In Comparative Example 9, diene 35A (low cis polybutadiene manufactured by Asahi Kasei Kogyo Co., Ltd.) was used instead of high trans polybutadiene. The evaluation results are shown in Table 5. Also, to help understanding,
Example 1 is reprinted in the table.

[0038]

Comparative Examples 10 to 15 In Comparative Examples 10 to 15, as the high cis polybutadiene species and the high trans polybutadiene species in the rubber composition, those listed in Table 6 were used as the polybutadiene species, and the molecular weight and the molecular weight distribution effect were evaluated. The high cis polybutadiene / high trans polybutadiene = 92/8 weight composition ratio was evaluated. The evaluation results are shown in Table 6. Also, to help understanding,
Example 1 is reprinted in the table.

[0039]

[Table 1]

[0040]

[Table 2]

[0041]

[Table 3]

[0042]

[Table 4]

[0043]

[Table 5]

[0044]

[Table 6]

[0045]

INDUSTRIAL APPLICABILITY The rubber composition used in the present invention is excellent in cold flow characteristics, and the impact-resistant polystyrene resin obtained by using it has gloss and impact resistance as compared with conventional impact-resistant polystyrene. The sex correlation is remarkably improved.

Claims (1)

[Claims] 1. A method using (A) a rare earth metal-based catalyst,
High-cis polybutadienes having the following structures
60 to 99 parts by weight and the content of the butadiene segment is 90% by weight or more The bonding mode of the butadiene segment is in the following range 1,4-cis bond 75-99.5% 1,4-trans bond 22-0.5 % 1,2-bond 3 to 0% The weight average molecular weight is in the range of 50,000 to 500,000, and the molecular weight distribution represented by weight average molecular weight / number average molecular weight is 1.2 to.
Range of 3.5 (B) Crystalline high-trans polybutadienes obtained by using a rare earth metal-based catalyst and having the following structures and characteristics: 40 to 1 part by weight Content of butadiene segment is 90% by weight or more. The bonding mode of the butadiene segment is in the following range. 1,4-cis bond 12-0.5% 1,4-trans bond 80-99% 1,2-bond 8-0.5% Crystallinity at 25 ° C is 5% by weight or more Weight average molecular weight is 1- In the range of 400,000, the molecular weight distribution represented by the weight average molecular weight / number average molecular weight is 1.2 to
Impact-resistant polystyrene resin comprising 2 to 20% by weight of a rubber composition in the range of 3.5 and 98 to 80% by weight of polystyrene