JPS60203618A - Preparation of rubber-modified styrene based resin - Google Patents

Abstract

PURPOSE:To obtain the titled resin having improved colorability with a colorant, practical impact resistance, rigidity and gloss, by dissolving a polybutadiene rubber of a specific structure prepared by solution polymerization in the presence of an organolithium compound as a catalyst in styrene, and polymerizing the styrene. CONSTITUTION:2-15pts.wt. polybutadiene rubber, obtained by solution polymerization of butadiene in a solvent, e.g. benzene, in the presence of an organo lithium compound, e.g. n-butyllithium, as a catalyst, and having 20-40% 1,2- vinyl bond structure, 15-35% cis-1,4 bond structure, 1.2-1.8 ratio (Mw/Mn) between the weight-average molecular weight (Mw) and the number-average molecular weight (Mn) and >=50% coupling degree with a tri-tetrafunctional binder, e.g. SiCl4, is dissolved in 85-98pts.wt. styrene based monomer, and the resultant solution is subjected to block or block-suspension polymerization to afford the aimed resin.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a rubber-modified styrenic resin with excellent coloring properties. More specifically, due to the special structure of polybutadiene used as a toughening agent, it is possible to produce a rubber-modified styrenic resin that has excellent colorability with colorants, practical impact resistance, rigidity, and gloss. Regarding the method.

Traditionally, rubber-modified styrenic resins are produced by dissolving unvulcanized rubber in styrenic monomers and subjecting this solution to bulk, solution or bulk-suspension polymerization, or by simply mechanically polymerizing the unvulcanized rubber. It has been manufactured by mixing it with In particular, rubber-modified styrenic resins obtained by bulk or bulk-suspension polymerization are widely used industrially. In this case, unvulcanized rubbers commonly used as toughening agents include polybutadiene rubber and styrene-butadiene rubber. Polybutadiene rubber is most commonly used because the obtained rubber-modified styrenic resin has better low-temperature impact resistance than styrene rubber.

However, one of the drawbacks of rubber-modified styrenic resins using polybutadiene rubber as a toughening agent is poor colorability with colorants. Styrenic resins such as polystyrene that do not contain toughening agents originally have better coloring properties than other resins such as polyethylene, but in order to improve impact resistance, rubber-like toughening resins When the agent is added, the coloring property is significantly impaired. This tendency is more pronounced when polybutadiene rubber is used as the toughening agent than when using styrene-butadiene rubber, and even in polybutadiene rubber, cis-1,4 bonds obtained by solution polymerization with a lithium catalyst Rather than so-called low-cis polybutadiene rubber, which has a structure of 25 to 45%, so-called high-cis polybutadiene rubber, which has a cis-1,4 bond structure of 90% or more, is obtained by solution polymerization using a Ziegler catalyst. The coloring property is even worse.

Rubber-modified styrenic resins generally have a two-phase structure consisting of a rubber phase and a polystyrene phase, and it is speculated that this two-phase structure is one of the reasons why rubber-modified styrenic resins deteriorate in colorability. .

Transparency decreases due to the presence of a rubber phase,
In addition, although the dispersed rubber phase has a so-called salami structure containing a styrene polymer inside, the polybutadiene portion has poor coloring properties, which is thought to reduce the coloring property of the rubber-modified styrenic resin as a whole. It's here.

On the other hand, rubber-modified styrene-based resins are often used by injection molding to make so-called home appliances, such as TV frames, radio and video housings, but in that case, the physical properties required of the resin are coloring. It is desired that the material not only has good hardness and excellent impact resistance for practical use, but also has good gloss. It is generally known that the size of the rubber phase dispersed in the two-phase structure of rubber-modified styrenic resin has a large effect on gloss. That is, if the size of the rubber phase is made small, the gloss will be improved but the impact resistance will be poor, and if the size of the rubber phase is made large, the impact resistance will be strong but the gloss will be reduced.

To date, a satisfactory method for obtaining rubber-modified styrenic resins with excellent low-temperature impact resistance, coloring properties, and gloss has not yet been clarified.

As a disclosure of these improved techniques, Japanese Patent Application Laid-Open No. 53-13079
There is Publication No. 1. This specifies the polymer structure of polybutadiene rubber used as a toughening agent.

That is, JP-A-53-13079: LM Zenkan states that the polymer structure of polybutadiene is 7 to 35% 1,2 vinyl bond structure and 20 to 80% cis 1,4 bond structure.
%, a ratio of weight average molecular weight (Mw) to number average molecular weight (Mn) (Mw/Mn) of 2.6 or more, and a Williams recovery value of 2.68 or more. A solution in which polybutadiene rubber is dissolved in styrene. By bulk polymerization or bulk-suspension polymerization, impact-resistant polystyrene with improved low-temperature impact resistance and colorability can be obtained.

However, when we examine the method described in JP-A No. 53-130791 in detail, we find that, compared to conventional polybutadiene rubber, it does show some improvement in colorability and low-temperature impact resistance. However, it is not possible to obtain a satisfactory gloss, which is a practically necessary physical property.

The present inventor has solved this problem and has achieved the above three practical important points.
In order to obtain a rubber-modified polystyrene-based resin with an excellent balance of physical properties, as a result of intensive research, we have developed a rubber-modified polystyrene-based resin with excellent colorability, practical strength, and gloss by using a specific rubbery polymer. Find out what you can get,
The present invention has now been completed.

That is, the present invention provides (A) 1.2 vinyl bond structure is 2
0-40%, 15-35% cis 1,4 bond structure, (B
) Ratio of weight average molecular weight CM and number average molecular weight (Mn) (
My/Mn) is 1.2 or more and less than 1.8, and (Q cutting degree is 50% or more) Polybutadiene rubber is dissolved in a styrene monomer and the solution is subjected to bulk or bulk-suspension polymerization. The present invention provides a method for producing a comb-modified styrenic resin characterized by the following.

The present invention will be explained in more detail below.

First, the polybutatsuene rubber used as the toughening agent of the present invention will be described. The specific polybutadiene rubber used in the present invention is an organolithium compound such as n-butyllithium, especially -butyllithium, t-butyllithium, n-butyllithium, etc.
It is solution polymerized using propyllithium, isopropyllithium, benzyllithium, trimethylenelithium, etc. as a catalyst.

The polybutadiene rubber used in the present invention has a 1.2 vinyl bond structure of 20 to 40%, preferably 23 to 35%,
Cis 1,4 bond structure is 15-35% preferred, <18
It must be ~27chi. When a polybutadiene having a microstructure outside this range is used, the resulting rubber-modified styrenic resin has extremely poor coloring properties and is of poor practical value. Furthermore, if the 1.2 vinyl bond structure exceeds 40%, the properties as a rubber toughening agent will be poor. Furthermore, it is necessary that the weight average molecular weight (ratio of M and number average molecular weight (Mn) (Mw/M n ) of the polybutadiene rubber is 1.2 or more and less than 1.8.

If it is less than 1.2, the resulting rubber-modified styrenic resin will have excellent gloss but poor practical strength, and if it is 1.8 or more, it will have excellent practical strength but no gloss.

In addition, the colorability is also poor.

Furthermore, polybutadiene is required to have a branched polymer chain. That is, the ratio of coupled polybutadiene to the total (coupling degree )
is required to be 50% or more.

When the degree of coupling is less than 50%, the coloring properties of the rubber-modified styrenic resin obtained are poor, and especially when the degree of coupling is less than 30%, the coloring properties are extremely poor and are not suitable for practical use.

In the method of the present invention, the degree of coupling is 50% or more,
It is preferably 65% or more.

The method for producing such polybutadiene may be any conventionally known method;
Solution polymerization is carried out using an organic lithium compound such as c-butyllithium as a catalyst, and as mentioned above, halogen compounds such as silicon tetrachloride, tin tetrachloride, carbon tetrachloride, diesters such as diethyl adipate, dimethyl maleate, etc. The coupling reaction can be carried out with a polyfunctional binder (J, Po
Any other conventionally known method may be used as long as it satisfies the following.

In the method for producing a rubber-modified styrenic resin of the present invention,
The ratio of polybutadiene rubber to styrene monomer is 2.
~15 parts by weight -85 to 98 parts by weight are preferred. If the concentration of polybutadiene rubber is less than 2% by weight with respect to the total amount of polybutadiene rubber and styrene monomer, the impact strength of the resulting resin will be insufficient, and if it exceeds 15% by weight, it will not be economical. The most suitable range is from 2 to 15% by weight, since the degree of improvement in strength is small relative to the ratio of properties, and problems such as excessively high viscosity of the polymerization system tend to occur.

The method for producing the rubber-modified styrenic resin of the present invention includes:
Bulk, solution or bulk-suspension polymerization methods are advantageously used.

For example, when using the bulk-suspension polymerization method, the polybutadiene rubber of the present invention is dissolved in a styrene monomer, and the solution is mixed with an azo compound such as azobisinbutyronitrile, azobiscyclohexanecarbonitrile, etc. The solution is heated with stirring in the presence or absence of a catalyst such as peroxide such as benzoyl peroxide, t-butyl peroxybenzoate, zot-t-butyl oxide, dicumyl peroxide, etc. Radical polymerization is carried out, and the polymerization rate is 20~
When the concentration reaches 40%, the polymerization solution is suspended in water to continue polymerization and complete the polymerization. At this time, a molecular weight regulator such as mercaptan and a plasticizer such as white mineral oil may be used as appropriate. Further, it is also possible to separately add a catalyst and a molecular weight regulator during the polymerization.

In the present invention, the styrenic monomers include styrene, halamethylstyrene, t-,11-methylstyrene, α-methylstyrene, chlorostyrene, etc., singly or in combination. Further, a part of the styrene-based monomer may be replaced with a monomer that can radically copolymerize with these monomers, such as acrylonitrile, methyl methacrylate, and methyl acrylate.

The rubber-modified styrenic resin obtained in this manner is superior to conventional resins in terms of colorability with colorants, as well as practical impact resistance, marking properties, and gloss.

The rubber-modified styrenic resin obtained by the method of the present invention may be used in addition to a coloring agent, if necessary, in addition to a fermentation inhibitor,
It can be used for general injection molding, extrusion sheet molding, etc. by adding ultraviolet absorbers, lubricants, mold release agents, fillers, etc. in advance.

The present invention will be explained in more detail below using Examples and Comparative Examples. The present invention is not limited only to these examples.

Examples are shown in Table 1, and comparative examples are shown in Table 2. The rubber-modified styrenic resin shown in the Examples is excellent in all physical properties, and the one according to the present invention has a good balance of physical properties. I understand that.

Example 1 [Polybutadiene rubber synthesis] 50 L of dehydrated benzene, 10 mmol of n-butyllithium, and 0.7 f of THF (tetrahydrofuran) as a vinylating agent were placed in an autoclave with an internal volume of 100 t.
I prepared it. 700Of butadiene was added and polymerized at 60°C for 2 hours. Tin tetrachloride was added as a coupling agent to the obtained polymer, and after further reaction for 1 hour, methanol 709 was added to terminate the polymerization reaction.
As an anti-aging agent, 4-methyl-slow ditertiary
50 tf each of butylphenol and trinonylphenyl phosphite were added, and the polymer was precipitated by a steam nutribbing method. The physical properties of the polybutadiene rubber obtained by drying using the usual drying method were
Shown in the table.

[Synthesis of rubber-modified styrenic resin]

A rubber solution in which 8 parts by weight of the obtained polybutadiene was dissolved in 92 parts by weight of styrene was charged into a 100 t autoclave, and 0.0.
05 parts by weight, tertiary decyl mercazotane 0.0
Add 5 parts by weight and stir at 250 rpm. After replacing the inside of the autoclave with nitrogen gas, seal it tightly and raise the temperature. 1
After polymerizing at 00℃ for 6 hours, it was cooled and then the capacity was 200t.
100 Kf of pure water, sodium dodecylbenzenesulfonate O, St, and 800 f of tribasic calcium phosphate were added to an autoclave, and while stirring at 130 rpm, 77 f of &3 ditertiary 4-oxybutyric acid ethyl ester was added to the above-mentioned preliminary. 70 Kt of polymerization solution was added, and after purging with nitrogen, the vessel was sealed, heated, polymerized at 115°C for 5 hours, and at 135°C for 4 hours, and then cooled. After neutralization, dehydration, and drying in accordance with a conventional method, the polymer was put into an extruder to form a conventional lozenge to obtain a rubber-modified styrenic resin. The results of this physical property measurement are shown in Table 1.

Examples 2 to 5 and Comparative Examples 1 to 4 Polybutadiene rubber samples with different microstructures, degrees of coupling, and My/Mn were obtained in the same manner as the polybutadiene rubber was obtained in Example 1.

Using these polybutadiene rubbers, rubber-modified styrenic resins of Examples 2 to 5 and Comparative Examples 1 to 4 were obtained by the same bulk-suspension polymerization method as in Example 1.

Tables 1 and 2 show the measured values of these physical properties.

Comparative Examples 5 to 7 Three commercially available polybutadiene rubbers were used for the polybutadiene rubber glue used in Example 1, and
A rubber-modified styrenic resin was obtained. What commercially available number did you use? Table 2 shows the brand of Liptatsune rubber and the measured physical properties.

Example 6 Using the polybutadiene rubber obtained in Example 1, bulk polymerization was carried out under the following conditions to obtain a rubber-modified styrenic resin.

Polymerization liquid composition: 92 parts by weight of styrene 8 parts by weight of polybutadiene
Polymerization conditions: ■ 120°C, 70 rpm, 2 hours, ■ 14
0° C. 25 rpm 4 hours ■ 165° C. 10 rpm 4 hours Removal of unreacted monomers 230° C. 45 minutes This was formed into pellets using a 20-mode φ extruder.

Table 1 shows the physical property measurement results.

The microcomposition of polybutadiene was determined by measuring the infrared spectrum using an infrared spectrophotometer (model A-302 manufactured by JASCO Corporation) using carbon disulfide as a solvent, and using the Morello method [D, Mars
ro et al., Chim, 61nd, 41, 75
8 (1959)).

My/Mn of polybutadiene, coupling degree is G
Using a PC (HLC-802A manufactured by Toyo Soda),
Measurement was performed under the following conditions.

Solvent: Tetrahydrofuran (THF) Column: Toyo Ichida GMH-62Fset 2 columns Constant temperature bath Temperature: 38°C Solvent flow rate: 15 m/min Sample concentration: 0.1 Weight - Sample injection amount: 0.5 m Detector: Differential Refractometer data processing device: Toyo Soda CP-8000 Force springing degree is GPC7' obtained under the above GPC measurement conditions
- In the evening, the peak area ratio on the GPC chart corresponding to the molecular weight of the uncoupled rubber and the molecular weight of the coupled rubber is calculated and used as the coupling coefficient.

The physical properties of the rubber-modified styrenic resin were measured by the following method.

(1) Tensile strength: According to JIS K-6871 (2)
Izotsu impact strength: According to JIS K-6871 (3) Falling weight strength: 12cn1X of bigastric thickness by injection molding
At the center of the 12 cm square plate, the tip of the weight is 5 R.

Drop a weight with a diameter of 14 mm and a weight of 111 mm, and measure the strength by multiplying the height (cnl) at which cracks will not occur and the weight of the weight.

The molding machine was a 2-ounce in-line screw injection molding machine 5N-51B manufactured by Niigata Tekkosho Co., Ltd., and the molding temperature was 230°C.
Molded with. However, injection molded products are susceptible to directionality, and even when they crack due to external forces, they tend to crack in the direction of the molding flow. In this respect, the falling weight strength is the easiest to find the direction of, so in the present invention, the falling weight strength is adopted as an expression that suits the actual situation.

(4) Gloss: According to JIS Z-8741 (5) Colorability: 0.5 part of Nippon Pigment's blue pigment P8D-B-871 was added to 100 parts by weight of resin, and injection molded into a 33-step step plate. The one that is R-shaped, has a deep ultramarine blue color, is closest to the color of the pigment itself, and has the best coloring properties is labeled A, and the one that has a pale gray background and has the poorest coloring properties is labeled E, and the one in between. B and C in order.

Rated D.

[Brief explanation of drawings]

FIG. 1 shows molecular weight distribution curves by GPC of the polybutadiene rubber (A) used in Example 2 of the present invention and the commercially available polybutadiene rubber (B) used in Comparative Example 6, respectively. The horizontal axis shows the molecular weight in logarithm, and the subordinate axis shows the weight type. Patent applicant Denki Kagaku Kogyo Co., Ltd. Figure 1 3.00 4.00 5.00 6.00 7.00 [
LOGM]

Claims (2)

[Claims] (1) When polybutadiene rubber is dissolved in a styrene monomer and the solution is polymerized to produce a rubber-modified styrenic resin, the polybutadiene rubber has (A) 1.2 vinyl bonds. Structure is 20 to 40, cis 1,
4-bond structure is 15-35%, (B) Weight average molecular weight (MY) and number average molecular weight (M
n) has a ratio (Mw/Mn) of 1.2 or more and less than 1.8, and a (Q) coupling degree of 50% or more. (2) A method for producing a ren-based resin containing 2 to 15 parts by weight of polybutadiene rubber.