JPS63159414A - Preparation of rubber-modified styrene resin composition having excellent flow property - Google Patents

Abstract

PURPOSE:To obtain the title resin composition easily, by graft-polymerizing styrene monomers in the presence of a rubbery polymer and a mineral oil and then adding a specified MW modifier at a point where the polymerization conversion rate reaches a given value. CONSTITUTION:Styrene monomers are graft-polymerized in the presence of a rubbery polymer of which the viscosity of a 5% styrene solution is 50-100cp and a mineral oil. When the polymerization conversion rate of these monomers is in a range of 10-50wt%, an MW modifier (e.g. acetyl chloride) having a chain transfer constant of 0.15-0.4 is added in an amount of 0.05-0.5pt.wt. per 100pts.wt. monomers, thereby obtaining the title resin composition wherein the weight-average MW of the continuous phase of styrene polymers is 11X10<4>-18X10<4>, the weight-average particle diameter of the grafted rubbery polymer particles is 1.8-5mu, the concentration of the rubbery polymer is 4-10wt%, and the methanol-soluble content in the graft-polymer product is 3-6wt%.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Field of Application) The present invention relates to a method for producing a rubber-modified styrenic polymer resin that has excellent flow characteristics during hot melting, that is, processability and moldability. It is something.

(Prior art) Conventionally, in order to improve the impact resistance of styrenic polymers, styrenic monomers are graft-polymerized to rubbery polymers, and the grafted rubbery polymers are dispersed in a polystyrene phase. , so-called rubber-modified styrenic resin compositions are known.

The rubber-modified styrenic resin obtained in this way is.

Its impact resistance has been greatly improved, and it is widely used in toys, daily necessities, food packaging containers such as meat trays, and various types of light electrical housings.

However, rubber-modified styrenic resins have poorer flow characteristics during injection molding than non-rubber-modified styrenic polymers. Therefore, in order to improve the flow characteristics, methods of adding mineral oil (Japanese Patent Publication No. 29-7892), methods of adding higher fatty acids such as stearic acid and oleic acid or their metal salts (Japanese Patent Publication No. 48-1236), etc. Proposed. Although these improved technologies improve the release property from the mold during injection molding, the release performance is lower than usual due to high-speed injection molding of molded products such as gears with complex shapes, and as a measure to save energy. When molding under temperature conditions, no fundamental solution has yet been found.

In addition, increasing the amount of mineral oil in order to improve fluidity will lower the heat resistance and mechanical strength (e.g., Vicat softening point and tensile strength), and will also limit industrial applications. .

(Problems to be Solved by the Invention) In view of the current situation, the present inventors believe that even when using a complicated molding die, and in the economically advantageous low temperature range (170 to 190°C), We conducted extensive research on rubber-modified styrenic resins that can be easily injection molded, that is, have excellent flow characteristics when melted.

The fluidity during injection molding, that is, during hot melting, essentially depends largely on the value of the weight average molecular weight (NA) of the polystyrene continuous phase in the rubber-modified styrenic resin.

The weight average molecule m(
) is in the range of 20 x 10' to 35 x 10'.

As a means of improving fluidity during hot melting, that is, a method of reducing the molecular weight, it is possible to raise the temperature during polymerization to a high temperature of 150 to 170 ° C. in the process of producing a rubber-modified styrenic resin. A method for removing the polymerization heat accompanying polymerization is industrially difficult and economically disadvantageous, and is therefore impractical.On the other hand, one method for reducing the molecular weight at relatively low temperatures is the use of fats, which are molecular weight modifiers. A method of adding group or aromatic mercaptans from the initial stage of polymerization is known. However, rubber-modified styrenic resins obtained by such easy molecular weight adjustment methods have poor impact resistance because the molecular weight of the polystyrene chains graft-polymerized to the rubbery polymer finely dispersed in the polystyrene continuous phase also decreases. It has the disadvantage of being severely degraded. A cumulative addition method of mercaptan has been proposed as a method to solve these problems (Japanese Patent Publication No. 41-11468), but since the chain transfer constant (CB) for styrene monomer is large (Cs
= 20 to 40), it is industrially difficult to control the amount added to adjust the molecular weight, and when mercaptans are used,
Yellowing may be observed in the molded product obtained by injection molding, and the peculiar odor of mercaptan may remain, resulting in a decrease in commercial value.

Furthermore, the flow characteristics of rubber-modified styrenic resins are determined not only by the molecular weight of the polystyrene continuous phase, but also by the characteristics of the rubber phase finely dispersed in the continuous phase, such as the rubbery polymer concentration, its solution viscosity, the rubber particle size, and even more. Comprehensive optimization of the solvent solubility of rubber-modified styrenic resins is required.

The present invention was discovered based on comprehensive optimization of these flow characteristic improvement factors, with the aim of obtaining a rubber-modified styrenic resin with improved flow characteristics during hot melting.

[Structure of the invention]

(Means for Solving the Problems) To summarize the present invention, a styrenic monomer is prepared in the presence of a rubbery polymer having a solution viscosity of 50 to 100 centipoise in a 5% styrene solution and mineral oil. Graft polymerization is carried out, and (i) the weight average molecular weight (na) of the styrenic polymer continuous phase is 11Xl.
O'~18 x 10'.

(ii) The weight average particle diameter (D,) of the grafted rubber polymer particles dispersed in the styrenic polymer continuous phase produced by graft polymerization of a styrenic monomer to the rubbery polymer is , 1.8 to 5μ, (in) the concentration of the rubbery polymer in the graft polymerization product is 4 to 10% by weight, and (tv) the methanol soluble content of the graft polymerization product is 3 to 5μ. When producing a rubber-modified styrenic resin composition with a weight of 6% by weight, the chain transfer constant (Cs) is 0.15-0. A rubber-modified styrenic system having excellent fluidity during hot melting, characterized in that 0.05 to 0.5 parts by weight of a molecular weight regulator having a value of 4 is added to 100 parts by weight of the styrenic monomer. The present invention relates to a method for producing a resin composition.

Hereinafter, the configuration of the present invention will be explained in detail.

First, we will discuss what kind of graft polymer is being prepared in the method of the present invention for producing a rubber-modified styrenic resin with excellent fluidity properties during hot melting. In the present invention, the weight average molecular weight of the polystyrene continuous phase is l
It is an essential condition to control the range between 1X10' and 18X10'.

The weight average molecular weight of polystyrene mentioned here is a value measured by a widely known method, and the rubber-modified styrenic resin prepared by the method of the present invention is dissolved in a solvent of methyl ethyl ketone and methanol in a ratio of 10:1. Then, separate the styrene polymer phase and rubber phase by centrifugation, and pour the supernatant into methanol and reprecipitate.

A styrene polymer continuous phase is obtained by filtration and drying, a portion of which is dissolved in tetrahydrofuran, and measured by gel permeation chromatography (GPC).

In the present invention, the weight average molecular weight (NA) of the styrenic polymer continuous phase is from 11x10' to 18x10', preferably from 13x10' to 15x10' (7) mo(7), and below 11x10', the weight average molecular weight (na) is 11x10' to 18x10'. Although the flow characteristics (formability) are improved, it is difficult to ensure impact resistance that can withstand use, and it is not practical.
If it is 18×10' or more, it is impossible to achieve the purpose of fundamentally improving the flow characteristics during hot melting, which is the greatest effect of the present invention.

In order to achieve the object of the present invention, in addition to optimizing the weight average molecular weight (NA) of the styrenic polymer continuous phase, it is necessary to specify the type and amount of the rubbery polymer and the dispersed rubber particle diameter. is necessary.

That is, the concentration of the rubbery polymer in the rubber-modified styrenic resin prepared by the method of the present invention is in the range of 4 to 10% by weight, preferably 5 to 8% by weight.

The solution viscosity of a 5% styrene solution of the rubbery polymer at 30°C is 45 to 100 centivoices, and the weight average of grafted rubber particles produced by graft polymerization of a styrene monomer to the rubbery polymer. Particle diameter (DV) is 1
．． The requirement of 8-5μ is essential.

In each of the above-mentioned requirement ranges, if the lower limit is below, it will not be possible to obtain a molded product with impact resistance that can withstand use, and if the upper limit is exceeded, it will be difficult to improve the flow characteristics and injection molding will be difficult. The surface gloss of the molded product obtained by this process is extremely reduced.

The weight average particle diameter (DV) of the grafted rubber particles referred to here is determined by using an electrolytic solution consisting of dimethylformamide and ammonium thiocyanate, and measuring the weight average particle diameter (DV) of 50% using a Coulter counter (Model Coulter mTA-n).
It is obtained as a quantitative value by determining the % median.

Furthermore, in order to achieve the object of the present invention, the solubility of the rubber-modified styrenic resin prepared according to the present invention is important, and the methanol soluble content must be maintained in the range of 3 to 6% by weight. . The methanol soluble content referred to here is
Precisely weigh 1 g of the rubber-modified styrenic monomer of the present invention, and
After dissolving in 0g of toluene, reprecipitate in about 800g of methanol, filtering and drying, then accurately weigh the precipitate to determine the amount of the reduced component, and calculate the ratio of the reduced amount to the original amount of resin. means. If the methanol soluble content is 3% by weight or less, the effects of the present invention, especially during injection molding, will have the disadvantage that the temperature dependence of the required injection molding pressure will be high, and the temperature range in which injection molding can be performed will be narrowed. Also, if it exceeds 6% by weight, heat resistance and tensile strength will decrease.

The bending strength decreases, making it impractical. In addition, the methanol soluble content measured by the above method refers to the total weight % concentration of soluble components such as 2 to 4 Ek styrenic oligomers, unreacted monomers, mineral oil, etc. contained in the rubber-modified styrenic resin. means.

Next, important points in the manufacturing process of the method for manufacturing the rubber-modified styrenic resin of the present invention will be explained.

First, a rubbery polymer that satisfies the above conditions is added to a styrenic monomer, and the mixture is heated and dissolved at 40 to 60°C.

The mixture is further heated and preliminarily bulk polymerized at 90 to 150°C with stirring. In this preliminary bulk polymerization step, the polymerization conversion rate of the styrenic monomer is 10 to 50% by weight, preferably 20 to 4% by weight.
When the concentration reaches 0% by weight, a polymerization molecular weight regulator having a chain transfer constant (Cs) of 0.15 to 0.4 for the styrene monomer is added to 100 parts by weight of the styrene monomer. 0.05 to 0.5 parts by weight, preferably 0.1 to 0.5 parts by weight
A method of adding 0.3 parts by weight and then carrying out bulk polymerization (bulk polymerization method), or a method of transferring and suspending polymerization to an aqueous phase containing a suspending agent such as tribasic calcium phosphate (bulk-suspension method) The polymerization is completed by a step polymerization method) or the like. It goes without saying that a polymerization initiator such as benzoyl peroxide can be used during the polymerization.

The chain transfer constant (Cs) here is 0.15 to 0.
A typical molecular weight modifier having a value of 4 is 2°4.
-diphenyl-4-methyl-1-pentene, 2°4.4
．． Examples thereof include triphenyl-1-pentene, paratertiary-butylpyrocatechol, dibromoethyl acetate, and acetyl chloride.

Here, in a different manner from that described above, that is, a molecular weight regulator is added at the initial stage of polymerization and polymerization is carried out.

The rubber-modified styrenic resin finally obtained cannot have impact resistance sufficient for use.

On the other hand, if the molecular weight modifier is added when a polymerization conversion rate of 50% by weight or more is reached, a resin composition with high fluidity, which is the objective of the present invention, cannot be obtained; If the molecular weight of the polystyrene continuous phase is forcibly lowered to give it high fluidity, the molecular weight modifier will remain in the rubber-modified styrenic resin that is finally obtained, causing flashing during injection molding or Therefore, in the method for producing the rubber-modified styrenic resin of the present invention, the timing of addition and the proportion of use of the molecular weight modifier are important requirements.

The rubber-modified styrenic resin obtained as described above is pelletized in the extrusion process when the entire process is carried out by bulk polymerization.
When carrying out a two-stage bulk-suspension polymerization method, the slurry is dehydrated;
The obtained beads are dried and pelletized using an extruder.

Further, the particle size of the grafted rubbery polymer particles specified in the present invention can be achieved by adjusting the stirring conditions during the preliminary bulk polymerization. In other words, by decreasing the rotation speed of the stirring blade, the average particle size increases, and by increasing the rotation speed, the rubber particle diameter decreases, so by selecting an appropriate stirring rotation speed, the particle size of the rubbery polymer particles can be adjusted. is achieved.

The styrenic monomer used in the method for producing a rubber-modified styrenic resin of the present invention is styrene.

α-methylstyrene, and styrene derivatives in which the hydrogen atom of the benzene nucleus is substituted with a halogen atom or a C1-C4 alkyl group, such as 0-chlorostyrene, P-chlorostyrene, and P-methylstyrene.

Examples include t-butylstyrene.

The rubbery polymer used in the method of the present invention is not limited as long as the solution viscosity of a 5% styrene solution at 30°C is in the range of 45 to 95 centistokes, but
Representative examples include polybutadiene rubber, styrene-butadiene copolymer rubber, styrene-butadiene-styrene block copolymer rubber, and ethylene-propylene terpolymer rubber.

The rubber-modified styrenic resin of the present invention prepared as described above can be blended with mineral oil as an additive flow improver. Mineral oil is added during the polymerization process or during the extrusion process. The type of mineral oil to be used is not particularly limited, but it is preferable to use one having a kinematic viscosity of 60 centistokes or less at 100 F.

In addition, in the present invention, 3,5-ditertiary
Of course, known and commonly used additives such as antioxidants such as butyl-4-hydroxytoluene (BHT) and lubricants such as zinc stearate can be used.

〔Example〕

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. In addition, all parts and percentages in the examples are based on weight.

Measurements of various physical properties in the examples were performed as follows.

■Melt flow rate JIS-7210 ■Izotsu impact value Compliant with JIS K-7110.

■Tensile strength Compliant with JIS K-7113.

(to) V 1cat softening temperature Compliant with JIS K-7206.

0 surface gloss Compliant with JIS Z-8741.

(2) Rubbery polymer content Determined by infrared spectroscopy, photometry, or pyrolysis gas chromatography.

■Flow characteristics due to spiral flow The Archimedes spiral flow mold is attached to an injection molding machine and the injection ram pressure is 600 kg/am.
) The flow characteristics were evaluated.The relationship between the inflow length ratio (L/T) obtained from the length L) from the position of the nozzle cod ≠ to the farthest part of the molded product and the molded product wall thickness (T) and the molding temperature, i.e. The temperature dependence of flow properties was investigated.

Example 1 701 Cg of styrene was charged into a polymerization tank with an internal volume of 100 Q and equipped with a stirrer, and a 5% styrene solution was added thereto to obtain a styrene-butadiene copolymer rubber (5BR containing 25% styrene) with a solution viscosity of 90 centipoise at 30°C. After pulverizing, the mixture was added and heated at 50° C. for 6 hours with stirring to dissolve until a homogeneous solution was obtained.

After adding 3 kg of mineral oil to this, increase the stirring number to 8.
Orpm, the temperature was raised and preliminary polymerization was carried out at 117° C. for 4 hours, and the polymerization conversion rate of styrene was 32%.

To this, 0.2 kg of 2,4-diphenyl-4-methyl-
1-pentene was added, and 10 minutes later, the polymer intermediate resulting from the prepolymerization was transferred to a polymerization tank equipped with a stirrer and having an internal volume of 200 Q, which had been adjusted and prepared in advance as described below, and was suspended and dispersed.

Water 140 kg Tertiary calcium phosphate 2 kg Polyvinyl alcohol 0.5 kg To this, add 0.2 kg of ditertiary-butyl peroxide,
Polymerization was carried out at 15°C for 3 hours and at 130°C for 2 hours. The obtained bead-like particles were filtered, dried, and extruded into pellets using an extruder.

Weight average molecular weight of the polystyrene continuous phase in the rubber-modified styrenic resin prepared as described above.

The concentration of the rubbery polymer, the weight average particle diameter of the grafted rubbery polymer, the measurement results of the methanol soluble content, and the measurement results of the physical properties of the test piece obtained by injection molding the pellets are shown in Table 1. Shown. or.

FIG. 1 shows the temperature dependence of the flow characteristics obtained by the spiral flow injection molding method.

Comparative Examples 1 and 2 Prepolymerization was carried out at 117°C for 1 hour, and the polymerization conversion rate of styrene was set at 8% (Comparative Example 1), and in Comparative Example 2, preliminary polymerization was carried out at 117°C for 7 hours, and the polymerization conversion rate of styrene was set at 8%. 5
A rubber-modified styrenic resin for comparison was obtained in the same manner as in Example 1 except that the amount was 8%.Next, various physical properties were measured in the same manner as in Example 1. The results are shown in Table 1 and Figure 1.

Table 1 From these results, the following can be said.

The pellets obtained by the method of Comparative Example 1 had an extremely poor isolite impact value and were not usable.

Also, the temperature dependence of fluidity in the spiral flow injection molding method is shown in FIG.

Although it is higher than that of Example 1, this is 200-2
The temperature range is 20°C, and there is no difference between the two in the low temperature range (180°C), which is the focus of the present invention.

On the other hand, the pellets obtained by the method of Comparative Example 2.

As is clear from FIG. 1, the injection molding temperature is lower than that of Example 1 in the entire range of injection molding temperatures, and the temperature dependence is high. This means that the pellets obtained by the method of Example 1 not only have a higher inflow length ratio than the pellets obtained by Comparative Example 2, but also provide stable molded products even when the molding temperature slightly fluctuates. (Low incidence of defects due to short shots etc.)
This means that you can get

Example 2.3 and Comparative Examples 3 and 4 Solution viscosity and amount added of a 5% styrene solution as a rubbery polymer at 30° C., and amount added of mineral oil.

Type and amount of molecular weight regulator used in the prepolymerization process,
A rubber-modified styrenic resin was obtained under the same conditions as in Example 1, except that the stirring rotation speed was changed as shown in Table 2, and then various physical properties were measured in the same manner. The results are also shown in Table 2.

Table 2 Compared to Example 2, Comparative Example 3 used a raw material rubber having an extremely high 5% solution viscosity of a rubbery polymer.
It can be seen that to obtain a resin with a melt blow rate equal to that of Example 2, it is necessary to increase the amount of mineral oil. In addition, the Vicat softening point and tensile strength of Example 2 were significantly improved compared to those of Comparative Example 3, demonstrating its superiority.

On the other hand, Example 3 and Comparative Example 4 compare the types of chain transfer agents used, that is, 2,4-biphenyl-4-methyl-1-pentene and n-dodecyl mercaptan. No abnormality was observed on the surface or hue of the molded product obtained, but in Comparative Example 4 using n-dodecyl mercaptan, flash was observed on the surface of the molded product and yellowing was observed in the molded product, making it unsuitable as a product. It was a loss of value.

Example 4 A raw material solution prepared by completely dissolving 7 parts of polybutadiene and 3.5 parts of mineral oil with a 5% styrene solution having a solution viscosity of 85 centipoise at 30°C in 100 parts of styrene monomer was poured into an anchor paddle-shaped solution. The polymerization reaction was carried out using a continuous reaction apparatus consisting of four 20Q seed reactors equipped with stirring blades, a heat exchanger, and a devolatilization tank. °The raw material solution is continuously supplied at 7Q/hour and prepolymerized at 135°C, and at the same time, it is extracted at 7Q/hour and supplied to the second tank reactor. and polymerize at 140°C, and in a second polymerization tank hestyrene monomer stock solution 10
0 parts of 2,4-diphenyl-4-methyl-1-pentene were continuously fed. Note that here, the first
When the weight conversion rates of the polymerization tank and the second polymerization detection port were measured, they were 21% and 43%, respectively. Thereafter, it was extracted from the second polymerization tank at a rate of 7 Q/hour, and polymerized while being sequentially supplied to and extracted from the third (145°C) and fourth (165°C) polymerization tanks. After that, the polymerization liquid is transferred to a heat exchanger for 2
After heating to 30°C and removing volatile components under a reduced pressure of 50IIIHg, the mixture was melted and kneaded using an extruder and pelletized to obtain a rubber-modified styrenic resin.Next, various physical properties were measured.

Note that the rotation speed of each polymerization tank was 1100 rpm in the first polymerization tank.

The speed of the second polymerization tank was 70 rpm + the third polymerization tank was 50 rpm, and the fourth polymerization tank was set to 3 Orpm. The measurement results are shown in Table 3. 6 Comparative Example 5 As a rubber trade polymer, 9 parts of polybutadiene with a solution viscosity of 30 centivoids in a 5% styrene solution at 30°C was used, and While adding 3.5 parts of mineral oil, 2,4-diphenyl-4-methyl-1-pentene was added initially,
In addition, in order to have the same rubber particle system as in Example 4, polymerization was carried out under the same conditions as in Example 4, except that the stirring rotation speed of the first polymerization tank was set to 85 rpm, and pellets were obtained. I made a determination. The measurement results are shown in Table 3.

Comparative Example 6 Pellets were obtained by polymerization under the same conditions as in Example 4, except that the rotation speed of the first polymerization tank was set to 5 Orpm, and then various physical properties were measured. The measurement results are shown in Table 3.

Table 3 [Effects of the Invention] The rubber-modified styrenic resin obtained by the method of the present invention has extremely good fluidity during hot melting, that is, during injection molding, and therefore does not easily form protrusions or thin walls.

Even when injection molding is performed using a mold having a complicated shape such as a gear part, molding can be easily performed. Also, food container 2
When molding daily necessities, etc., it is possible to mold at low molding temperatures, resulting in cost reductions due to energy savings.On the other hand, when producing colored pellets using dyes and pigments, conventionally master pellets with a high concentration of dyes and pigments are used. Usually, the master pellets and natural pellets (uncolored pellets) are blended and kneaded to produce colored pellets, but the rubber-modified styrenic resin obtained by the method of the present invention is Because of its excellent dispersion effect, it is also usefully used as master pellets for resin coloring.

[Brief explanation of the drawing]

Figure 1 shows the flow characteristics obtained by the spiral flow injection molding method! Shows rt dependence. Patent applicant Dainippon Ink & Chemicals Co., Ltd. Agent
Patent Attorney Yoshio Mizuno Figure 1 (Temperature dependence of flow characteristics) 18020022c) Injection molding temperature ('C) Tough? 10 positive echo (spontaneous) 7 Showa 6
February 2nd

Claims (1)

[Claims] A styrenic monomer is graft-polymerized in the presence of a rubbery polymer having a solution viscosity of 50 to 100 centipoise in a 5% styrene solution and mineral oil, and (i) a styrenic polymer continuous phase is obtained. Weight average molecular weight (na) is 11 x 10^
4 to 18 x 10^4, (ii) grafted rubbery polymer particles dispersed in the styrenic polymer continuous phase produced by graft polymerization of a styrenic monomer to the rubbery polymer. Weight average particle diameter (D_w) is 1.8~
5μ, (iii) the concentration of the rubbery polymer in the graft polymerization product is 4 to 10% by weight, and (iv) the methanol soluble content of the graft polymerization product is 3
When manufacturing a rubber-modified styrenic resin composition having a concentration of 6% by weight, a chain transfer constant (C_s) of 0.15-0. A rubber-modified styrene-based rubber-modified styrene-based material having excellent fluidity properties during hot melting, characterized in that 0.05 to 0.5 parts by weight of a molecular weight regulator having a value of 4 is added to 100 parts by weight of the styrene-based monomer. Method for producing resin composition.