JP3236056B2 - Method for producing rubber-modified styrenic resin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a rubber-modified styrenic resin having excellent impact resistance balance and appearance.
More specifically, a rubber modification in which the amount of grafting is arbitrarily controlled and the rubber particle size distribution has a mechanical strength corresponding to a narrow application, and the appearance of unevenness such as weld lines and flow marks is hardly generated. The present invention relates to a method for producing a styrene resin.

[0002]

2. Description of the Related Art A rubber-modified styrenic resin is prepared by dissolving a rubber-like polymer in an aromatic monovinyl-type monomer and dispersing the resulting rubber particles with stirring. It is produced by any method of polymerization. However, the rubber-modified styrenic resin produced by such a method is subjected to a graft reaction because the rubber-like polymer is exposed to the polymerization reaction for a certain period of time before the rubber phase inversion where the rubber-like polymer becomes dispersed rubber particles. And the rubber particle size distribution represented by the ratio of weight average particle size / number average particle size (Dw / Dn) becomes wider,
In particular, there is a problem that unevenness of appearance such as a weld line and a flow mark easily occurs in an injection molded product.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to produce a rubber-modified styrenic resin having a arbitrarily controlled graft amount, a narrow rubber particle size distribution, and excellent balance between appearance and impact strength. An object of the present invention is to provide a method for producing a rubber-modified styrenic resin.

[0004]

The present inventors have conducted intensive studies to develop a rubber-modified styrenic resin having such preferable physical properties, and as a result, the rubber-like polymer is turned into particles by phase inversion. It has been found that the reaction before reaching the polymerization conversion rate has a very large effect on controlling the amount of grafting and narrowing the rubber particle size distribution. A monomer polymer and an aromatic monovinyl monomer solution containing a rubber-like polymer are supplied to a plug flow reactor while adjusting the blending, and the polymerization is allowed to proceed under specific conditions. Have been found, and the present invention has been completed.

That is, according to the present invention, a first reaction is carried out in which an aromatic monovinyl monomer containing no rubbery polymer is supplied to a first reactor and a polymerization reaction is carried out to a polymerization conversion rate not exceeding 50%. And a second stream of the aromatic monovinyl monomer solution containing 5 to 25% by weight of the rubbery polymer by mixing the polymerization product of the aromatic monovinyl monomer with the rubbery polymer. The compounding ratio is adjusted so that the weight ratio is 0.5 to 3.5, and the content of the rubbery polymer with respect to the aromatic monovinyl monomer and its polymerization product is 3 to 18% by weight. , A rubber phase inversion is continuously performed by continuously charging the inside of a plug flow type reactor to continue a polymerization reaction, and a ratio of weight average particle diameter / number average particle diameter of rubber particles after the rubber phase inversion occurs. (Dw / Dn) is controlled to be 2.0 or less,
Rubber-modified styrene-based resin that can be arbitrarily controlled in the amount of graft by removing the unreacted monomer and solvent after devolatilization after increasing the polymerization conversion rate by supplying it to the subsequent reactor It is a manufacturing method of.

Further, in this method for producing a rubber-modified styrenic resin, a method in which an aromatic monovinyl-based monomer containing no rubbery polymer is further compounded when fed to a subsequent reactor to increase polymerization conversion. It is. Further, in this method for producing a rubber-modified styrene resin, the polymerization solution from the final polymerization reactor is subjected to heat treatment conditions prior to devolatilization treatment, whereby the rubbery polymer component in the rubber-modified styrene resin is dissolved in toluene. This is a method of adjusting the swelling index within the range of 8 to 13.

Hereinafter, the present invention will be described in detail. In the method of the present invention, examples of the aromatic monovinyl monomer used as one component of the raw material include styrene alone or a mixture with another vinyl monomer copolymerizable with styrene. Examples of the copolymerizable monomer include aromatic monovinyl compounds such as α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, vinylethylbenzene, vinylxylene, and vinylnaphthalene; and methacrylic acid. Examples include methyl, ethyl methacrylate, methyl acrylate, ethyl acrylate, acrylonitrile, methacrylonitrile, methacrylic acid, acrylic acid, maleic anhydride, phenylmaleimide, and halogen-containing vinyl monomers. These copolymerizable monomers may be used singly or in combination of two or more, but are usually used for a wholly aromatic monovinyl monomer containing styrene. 30
% Or less, preferably 10% or less by weight.

In the method of the present invention, the rubbery polymer used as another component of the raw material includes polybutadiene,
Examples include styrene-butadiene copolymer, polyisoprene, butadiene-isoprene copolymer, and natural rubber. Polybutadiene may be low cis polybutadiene, or high cis polybutadiene,
The styrene-butadiene copolymer may be a random type having a styrene content of 5 to 50% by weight or a block type. These rubbery polymers are
The seed may be used alone, or two or more kinds may be used in combination. However, the amount may be 5 to 25% by weight based on the total weight of the aromatic monovinyl monomer forming the second stream. It is necessary that the content of the rubbery polymer based on the aromatic monovinyl monomer and its polymerization product be 3 to 18% by weight after mixing with the first stream. Needs to be adjusted. When the amount of the rubbery polymer contained in the second stream is less than 5% by weight, the amount of the rubbery polymer that obtains sufficient impact resistance after adjusting the blending with the polymerization solution of the first stream is maintained within a range. Does not provide a sufficient effect on the control of the graft amount. 25% by weight
In the above, the viscosity of the second flow increases, and the inside of the reaction system becomes non-uniform at the time of adjusting the compounding, and the control of the rubber particle diameter and the rubber particle diameter distribution becomes insufficient. If the amount of the rubber-like polymer after blending adjustment is less than 3% by weight, the impact resistance is insufficient, and if it exceeds 18% by weight, the viscosity of the polymerization system becomes too high, and operation troubles occur. This causes an unfavorable situation, such as an increase in the likelihood.

In the method of the present invention, an organic solvent can be added to the aromatic monovinyl monomer solution in which the rubbery polymer is dissolved, if necessary, in order to appropriately adjust the viscosity in the polymerization system. . Examples of such a solvent include aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene, and diethylbenzene, and at least one organic solvent selected from ketones such as methyl ethyl ketone. Can be blended in an amount of 30% by weight or less based on the aromatic monovinyl monomer solution in which is dissolved. If necessary, an organic peroxide or a chain transfer agent as a polymerization initiator, a general antioxidant, a mineral oil, a silicone oil, or the like can be appropriately added.

In the present invention, an aromatic monovinyl-based monomer containing no rubbery polymer is supplied to a first reactor and a polymerization reaction is carried out to a range where the polymerization conversion does not exceed 50%. The first reactor used here is not particularly limited, but is preferably stirred for ease of operation and operation and for controlling the molecular weight and the like of the aromatic monovinyl monomer polymer. It is preferable to use a complete mixing tank type reactor and continuously perform a bulk polymerization reaction within a polymerization temperature range of 80 to 120 ° C., depending on the type of the organic peroxide. The polymerization conversion for polymerization in the first reactor is 50% by weight or less, preferably 10 to 40% by weight of the aromatic monovinyl monomer.
It is necessary to be. If the polymerization conversion rate exceeds 50% by weight, it is difficult to adjust the rubber concentration to a predetermined rubber concentration due to the viscosity difference between the two streams when mixing and adjusting the second stream containing the rubbery polymer. It is not preferable.

When the first stream having undergone such a polymerization reaction is supplied to a plug-flow type second reactor, the polymerization reaction solution contains a rubber-like weight of 5 to 25% by weight based on the aromatic monovinyl monomer. The second stream of the aromatic monovinyl monomer solution containing the coalesced is adjusted so that the content of the rubbery polymer is 3 to 18% by weight based on the aromatic monovinyl monomer and the polymerization product thereof. Adjust blending. Such mixing adjustment may be performed beforehand in a pipe before being supplied to the plug flow type second reactor, or may be separately supplied and then mixed in the reactor. The supply amount of the first stream and the polymerization conversion rate of the aromatic monovinyl monomer to be adjusted are determined by the content and the supply amount of the rubbery polymer in the second stream. In this case, it is desirable to supply the mixture by adjusting the weight ratio of the polymerization product of the aromatic monovinyl monomer to the rubbery polymer to be 0.5 to 3.5. In particular, in the region where the weight ratio of the polymerization product of the aromatic monovinyl monomer to the rubbery polymer is less than 0.5, the influence of the grafting reaction until the rubber phase inversion occurs inside the plug flow type second reactor. Therefore, it is difficult to control the graft amount, and the rubber particle size distribution cannot be narrowed. Also,
If the blending is adjusted so as to have a weight ratio of 3.5 or more, the graft amount is extremely reduced, and the impact strength is reduced.

In the inside of the plug flow type second reactor, it depends on the content of the rubbery polymer after the blending and adjustment and the weight ratio of the polymerization product of the aromatic monovinyl monomer to the rubbery polymer. The rubber phase is inverted while the polymerization reaction is continued to form particles of the rubbery polymer. However, by controlling the stirring speed of the stirrer and the reaction temperature, the weight average particle diameter /
It is important to control the ratio of the number average particle diameter (Dw / Dn) to 2.0 or less to advance the polymerization reaction. At this time, if the ratio (Dw / Dn) of the weight average particle diameter / number average particle diameter of the rubber particles exceeds 2.0, unevenness in appearance such as weld lines and flow marks is unpreferably observed. In order to carry out the polymerization while controlling the ratio (Dw / Dn) of the weight average particle diameter / number average particle diameter of the rubber particles to 2.0 or less, the polymerization reaction solution output from the second reactor is sample-analyzed, and the polymerization temperature and It is preferable that the stirring be performed by appropriately controlling the stirring speed, the supply amounts of the first flow and the second flow, and the like.

The plug flow type second reactor has a performance in which the number of equivalent tanks in a complete mixing tank row model with small back mixing is 10 or more, preferably 30 or more. Any polymerizer can be used as long as it can be polymerized to the maximum extent. For example, a polymerization reactor equipped with a stirrer and a static mixer type plug flow reactor proposed in JP-A-63-238,101 can be used. The polymerization temperature in the plug-flow type second reactor is preferably in the range of about 100 to 140 ° C. Outside this range, the reaction heat is removed and the polymerization product of the aromatic monovinyl-based monomer forming the matrix is removed. It is not preferable in terms of control of molecular weight, control of rubber particle diameter, and the like.

In the present invention, the unreacted monomer, solvent and the like are removed by successively supplying the mixture to the subsequent reactor to increase the polymerization conversion of the aromatic monovinyl monomer and then performing devolatilization treatment. The subsequent reactor is not particularly limited as long as it can continue polymerization by a method such as a bulk polymerization method, a solution bulk polymerization method, or a suspension polymerization method.

When feeding to a subsequent reactor, an aromatic monovinyl monomer containing no rubbery polymer is further converted to an aromatic monovinyl monomer and a rubbery polymer to a polymerization product of the monomer. It is also an important factor to balance the impact strength to increase the polymerization conversion rate and the graft amount at the same time in order to increase the polymerization conversion rate. Although the range of the graft amount is not particularly limited, the degree of the increase is controlled by adjusting the polymerization conversion rate from the second reactor and the amount of the aromatic monovinyl monomer containing no rubbery polymer to be blended. Controlled.

After the polymerization is completed, unreacted monomers, organic solvents and the like are removed under reduced pressure while appropriately performing a heat treatment. It is also an important factor to select conditions such as the temperature and time of the heat treatment at this time and to control the swelling index of the rubber component in the form of particles in toluene within a specific range. Heating temperature is high,
The longer the heating time, the lower the swelling index, and the shorter the heating time, the higher the swelling index. The swelling index of the rubber component in toluene is preferably in the range of 8 to 13, and more preferably 9 to 11. When the swelling index is lower than 8, the impact strength is remarkably reduced. When the swelling index is higher than 13, even if the particle size distribution is controlled, appearance irregularities such as weld lines and flow marks during injection molding tend to occur.

[0017]

EXAMPLES Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. The properties of the resin were determined by the following methods. (1) Swelling index in toluene The swelling index of the rubber component in toluene is determined by adding 35 ml of toluene to 1 g of resin, sufficiently dissolving or swelling, sedimenting the gel component with a centrifuge, and then decanting. Separated gel is weighed. The toluene-swollen gel thus obtained is dried at 120 ° C. under normal pressure for 1 hour, and subsequently under reduced pressure for 1 hour, and the dried gel is allowed to cool in a desiccator and weighed. The swelling index is a value obtained by dividing the weight of the toluene-swelled gel by the weight of the dried gel. (2) Measurement of rubber particle size and particle size distribution In a Coulter counter (Coulter Multisizer II type) equipped with an aperture tube having a diameter of 30 μm, a matrix is formed using 2 to 3 resin pellets using a mixed solvent of methyl ethyl ketone / acetone. After dissolving only the polystyrene portion to be dissolved, it is separated from the undissolved rubber particle portion in a centrifuge. Then, it is dispersed in a dimethylformamide electrolyte solution at an appropriate concentration and measured. (3) Graft amount 1 g of resin was methyl ethyl ketone / acetone = 50/50
(WT / WT) is sufficiently dissolved in a mixed solvent, and the insoluble matter is separated by centrifugation, followed by decantation, drying of the precipitate, and weighing. The graft amount can be obtained by the following formula by setting this value to methyl ethyl ketone / acetone insoluble matter. Graft amount = (methyl ethyl ketone / acetone insoluble-
(Rubber content) ÷ Rubber content (4) IZ impact strength (kg · cm / cm) Determined in accordance with JIS K-6871 (notched). (5) Drop weight impact strength (kg · cm) Determined in accordance with ASTM D-1709. (6) Flexural modulus (kg / mm ² ) Determined according to ASTM D-790. (7) Unevenness in appearance Judgment was made by visual inspection of the injection molded product.

EXAMPLE 1 A raw material liquid composed of 93.3% by weight of styrene and 16.7% by weight of ethylbenzene was continuously supplied at a supply rate of 3 L / hr to a stirred polymerization type first reactor having an inner volume of 6 L. Then, a bulk polymerization reaction was carried out under a polymerization reaction condition of 115 ° C., and the polymerization conversion of styrene at the outlet of the reactor, which became a steady state, was 30%. Next, low-cis polybutadiene was placed in a plug flow type second reactor having an internal volume of 10 liters.
6% by weight, styrene 71.7% by weight, ethylbenzene 1
A raw material solution consisting of 6.7% by weight was mixed with the polymerization liquid from the outlet of the first reactor at a feed rate of 3 L / hr, and the content of low-cis polybutadiene was 5.8% by weight,
It was supplied at the same time as adjusting the weight ratio to the produced polystyrene to be 2.0.

Thereafter, the polymer having a rubber phase inversion at a polymerization conversion rate of styrene of 30% from the outlet of the second reactor was added with 1,
1-Di-tert-butylperoxycyclohexane and tert-butylcumyl peroxide were added, and the polymerization was continued in a subsequent plug-flow reactor until the polymerization conversion of styrene reached 95%. The volatile component was removed under reduced pressure while performing a heat treatment at 230 ° C. in a twin-screw extruder with a pellet to form a pellet. Table 1 shows the measurement results of the physical properties of the obtained resin.

Example 2 In Example 1, the polymerization temperature of the first reactor was changed to 110.
C. and the polymerization conversion of styrene at the outlet of the first reactor was 22.
Pelletization was carried out under the same conditions as in Example 1 except that the weight ratio after mixing was adjusted to 1.5%. Table 1 shows the measurement results of the physical properties of the obtained resin.

Example 3 In Example 1, the polymerization temperature of the first reactor was changed to 105.
° C and the polymerization conversion of styrene at the outlet of the first reactor was 15.
Pelletization was performed under the same conditions as in Example 1 except that the weight ratio after mixing was adjusted to 1% and adjusted to 1.0. Table 1 shows the measurement results of the physical properties of the obtained resin.

Example 4 In the above-mentioned Example 1, 1 part was added to the polymer obtained by inverting the rubber phase at a polymerization conversion rate of styrene of 30% from the outlet of the second reactor.
Pellets were formed under the same conditions as in Example 1 except that styrene was added at a feed rate of 1 liter / hr. Table 1 shows the measurement results of the physical properties of the obtained resin.

Comparative Example 1 In Example 1, the polymerization temperature in the first reactor was 100
° C and the polymerization conversion of styrene at the outlet of the first reactor was 7.0.
%, And pelletized under the same conditions as in Example 1 except that the weight ratio after mixing was adjusted to be 0.46. Table 1 shows the measurement results of the physical properties of the obtained resin.

Comparative Example 2 In Example 1, the polymerization temperature of the first reactor was set to 140
° C and the polymerization conversion of styrene at the outlet of the first reactor was 60.
Pelletization was performed under the same conditions as in Example 1 except that the weight ratio after mixing was adjusted to 0% and adjusted to 4.0. Table 1 shows the measurement results of the physical properties of the obtained resin.

Comparative Example 3 Pellets were formed under the same conditions as in Example 1 except that the temperature of the heat treatment in the twin-screw extruder was 210 ° C. Table 1 shows the measurement results of the physical properties of the obtained resin.

Comparative Example 4 Pellets were formed under the same conditions as in Example 1 except that the temperature of the heat treatment in the twin-screw extruder was changed to 250 ° C. Table 1 shows the measurement results of the physical properties of the obtained resin.

Comparative Example 5 5.8% by weight of low-cis polybutadiene, 77.
A raw material solution consisting of 5% by weight and 16.7% by weight of ethylbenzene was continuously supplied at a supply rate of 6 L / hr to a stirred polymerization type first reactor having an internal volume of 6 L at 115 ° C.
After the bulk prepolymerization reaction was performed to a polymerization conversion rate of styrene of 12% under the polymerization reaction conditions of the above, all the components were supplied to the plug-flow type second reactor having an internal volume of 10 liters without mixing. Pellets were formed under the same conditions as in Example 1.
Table 1 shows the measurement results of the physical properties of the obtained resin.

Comparative Example 6 In the raw material solution of Comparative Example 5, tert was used as a chain transfer agent.
-Pelleted under the same conditions as in Example 1 except that dodecyl mercaptan was added. Table 1 shows the measurement results of the physical properties of the obtained resin.

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

According to the method of the present invention, it is possible to easily produce a rubber-modified styrenic resin having a narrow rubber particle size distribution, excellent appearance and excellent impact strength balance, by arbitrarily controlling the graft amount. .

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yoshitaka Sakamaki 4-7-6, 101 Nakai, Kokurakita-ku, Kitakyushu-shi, Fukuoka Prefecture (56) References JP-A-3-277613 (JP, A) JP 47 −48515 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08F 279/00-279/04 C08F 291/00

Claims (3)

(57) [Claims] 1. An aromatic monovinyl monomer containing no rubbery polymer is supplied to a first reactor to obtain a polymerization conversion of 50.
% In which the polymerization reaction has been carried out to a range not exceeding
The second stream of the aromatic monovinyl monomer solution containing 5 to 25% by weight of the rubbery polymer is mixed with the polymerized product of the aromatic monovinylic monomer and the rubbery polymer in a weight ratio of 0. .5
To 3.5 and the content of the rubbery polymer with respect to the aromatic monovinyl monomer and its polymerization product is 3
１８18% by weight, and continuously charged into a plug flow type reactor to carry out the rubber phase inversion while continuing the polymerization reaction. Ratio of weight average particle diameter / number average particle diameter (Dw / Dn)
Is controlled so as to be 2.0 or less, and subsequently supplied to the subsequent reactor to increase the polymerization conversion rate, and then devolatilization treatment is performed to remove the unreacted monomers and the solvent. A method for producing a rubber-modified styrenic resin that allows arbitrary control. 2. The amount of grafting is increased by blending and adjusting an aromatic monovinyl monomer containing no rubbery polymer when feeding to a subsequent reactor to increase the polymerization conversion.
A method for producing the rubber-modified styrenic resin according to the above. 3. The swelling index of the rubbery polymer component in the rubber-modified styrene resin in toluene is adjusted to 8 to 13 by adjusting the heat treatment conditions prior to devolatilization of the polymerization solution from the final polymerization reactor. 3. Adjustment within 1
A method for producing the rubber-modified styrenic resin according to the above.