JP2006022219A - Method for producing diene-based rubber polymer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a diene-based rubber polymer, which improves productivity of a diene-based rubber polymer while keeping safety during polymerization of a diene-based monomer. <P>SOLUTION: The method for producing a diene-based rubber polymer by emulsion polymerization of a monomer containing a diene-based monomer comprises an initial polymerization process for collectively feeding ≥5 mass% and <10 mass % of the total monomer (100 mass%) to a reactor and polymerizing the monomer until the conversion ratio of the monomer to the polymer reaches 70-85 mass% and, successively the initial polymerization process, a drop polymerization process for dropping the residual monomer on the reactor and polymerizing the monomer. During the drop polymerization process, the monomer is dropped on the reactor so that the drop rate always makes the conversion rate of the monomer to the polymer 70-85 mass%. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing a diene rubber polymer.

  The diene rubber polymer is used as an elastic body in ABS (acrylonitrile-butadiene-styrene) resin, MBS (methyl methacrylate-butadiene-styrene) resin and the like, and is usually produced by emulsion polymerization. Of the performance of these resins, it is widely known that particularly impact resistance and the like depend on the particle size of the diene rubber polymer. The larger the particle size of the diene rubber polymer, the better the impact resistance, but there is a correlation between the particle size of the diene rubber polymer (number of particles) and the polymerization rate of the diene monomer. When the particle size is increased (the number of particles is decreased), the polymerization rate of the diene monomer is lowered, and the productivity of the diene rubber polymer tends to be lowered.

As a method for increasing the polymerization rate of the diene monomer, it is widely known that increasing the polymerization temperature is an effective means. However, when the polymerization temperature is increased from the initial stage of polymerization, the heat of polymerization per unit time is remarkably increased due to an increase in the polymerization rate, and the reaction control becomes difficult. Furthermore, as the production scale (reactor capacity) increases, it becomes difficult to remove the heat of polymerization reaction, which causes a runaway reaction. In particular, when the main component of the monomer is butadiene, if the temperature in the reactor is increased because the monomer has a large vapor pressure, the pressure in the reactor may increase significantly, possibly exceeding the reactor pressure resistance. There is. In order to avoid such a situation, it is conceivable to increase the pressure resistance of the reactor, but this leads to an increase in the production cost of the reactor, which is a big problem from the viewpoint of reducing the capital investment.
Based on this background, it is common to initiate the polymerization of the diene monomer at a relatively low temperature that does not cause a runaway reaction.

  In addition, the usefulness of diene rubber polymers has been increasing in recent years, and further improvement in productivity is desired. However, since the jacket cooling capacity per unit volume of the reactor decreases with an increase in the capacity of the reactor, even when the polymerization rate region can be easily produced in the case of a small scale, the capacity becomes large. The polymerization exotherm cannot be removed and causes a runaway reaction. Therefore, if the capacity of a reactor is increased for the purpose of improving productivity, it is necessary to reduce the polymerization rate to a speed corresponding to the heat removal capacity of the reactor, and to improve the target productivity. I had to take conflicting measures. Moreover, in order to implement production safely without reducing the polymerization rate, a method of increasing the heat removal capability by installing an auxiliary cooling facility such as a vent condenser is conceivable. It is difficult to improve productivity.

Thus, attempts have been made to improve the productivity of diene rubber polymers. For example, a semi-batch that continuously supplies a liquid feed composition comprising a diene monomer and an initiator to a liquid batch composition comprising water, an emulsifier, and a diene monomer previously charged in a pressure device. The proposal regarding the law is made | formed (for example, refer patent document 1).
However, in the method of Patent Document 1, if the temperature during polymerization is increased for the purpose of shortening the polymerization time, a diene monomer that is a high-pressure gas is used. Therefore, it is impossible to shorten the polymerization time above a certain level. Further, when the particle size of the diene rubber polymer is large, the difficulty of shortening the polymerization time is particularly noticeable.
JP-A-9-176213

  Therefore, an object of the present invention is to provide a method for producing a diene rubber polymer that can improve the productivity of the diene rubber polymer while maintaining safety during polymerization of the diene monomer. It is in.

As a result of studies to solve the above-mentioned problems, the present inventors have invented the method for producing a diene rubber polymer of the present invention.
That is, the method for producing a diene rubber polymer of the present invention is a method for producing a diene rubber polymer by emulsion polymerization of a monomer containing a diene monomer, and the total monomer (100% by mass) An initial polymerization step in which 5% by mass or more and less than 10% by mass of the monomer is charged into the reactor at once, and the monomer is polymerized until the conversion rate of the monomer to the polymer becomes 70 to 85% by mass; Subsequent to the initial polymerization step, there is a dropping polymerization step in which the remaining monomer is dropped into the reactor to polymerize, and during the appropriate polymerization step, the conversion rate of the monomer in the reactor to the polymer Is characterized in that the monomer is added dropwise at a dropping rate such that is always 70 to 85% by mass.
In addition, in the dropping polymerization step, it is desirable to drop 60 parts by mass or less of water together with the monomer with respect to 100 parts by mass of all monomers.

  According to the method for producing a diene rubber polymer of the present invention, it is possible to improve the productivity of the diene rubber polymer while maintaining safety during polymerization of the diene monomer.

Hereinafter, the present invention will be described in detail.
In the present invention, the pressure resistance is the reactor pressure resistance indicated by the reactor manufacturer, the normal pressure is the maximum pressure that can be increased in daily operations, and the initial stage of polymerization is a single amount from the start of polymerization. Up to the start of dropping of the rest of the body, the polymerization start temperature is a temperature at which the pressure at the start of polymerization becomes equal to or lower than the reactor normal pressure.

  The method for producing the diene rubber polymer of the present invention is a method in which a monomer containing a diene monomer is dispersed in water to which a polymerization initiator and an emulsifier are added. This is a method for producing a coalescence, in which a part of the monomers is charged into the reactor in a lump and the monomer is polymerized, and after the initial polymerization step, the remaining monomers are put into the reactor. A dropping polymerization step of dropping and polymerizing.

Examples of the diene monomer in the present invention include 1,2-butadiene, 1,3-butadiene, isoprene and the like.
Components other than diene monomers include aromatic vinyl compounds such as styrene and α-methylstyrene; acrylic acid esters such as methyl acrylate and n-butyl acrylate; methacrylic acid esters such as methyl methacrylate and ethyl methacrylate; acrylonitrile, And methacrylonitrile.
Moreover, it is possible to use crosslinking agents such as divinylbenzene, 1,3-butylene dimethacrylate, and allyl methacrylate; chain transfer agents such as mercaptans and terpenes in combination with monomers.

The emulsifier is not particularly limited, but alkali metal salts of higher fatty acids such as disproportionated rosin acid, oleic acid and stearic acid; sulfonic acid salt compounds such as sodium dodecylbenzenesulfonate and sodium alkyldiphenyl ether disulfonate; lauryl sulfate Examples thereof include sulfuric acid salt compounds such as sodium. These can be used alone or in combination of two or more.
In addition, an emulsifying dispersant can be used for the purpose of improving the polymerization stability. Examples of the emulsifying dispersant include sodium salt of β-naphthalenesulfonic acid formalin condensate.

  Although it does not specifically limit as a polymerization initiator, Water-soluble persulfuric acid, such as potassium persulfate, sodium persulfate, and ammonium persulfate; diisopropyl benzene benzene hydroperoxide, p-menthane hydroperoxide, cumain hydroperoxide, Redox initiators containing an organic peracid peroxide such as t-butyl hydroperoxide and methylcyclohexyl hydroperoxide as one component can be used.

The upper limit of the temperature in the reactor is not particularly limited, but is preferably 120 ° C. or less from the viewpoint of the stability of the diene rubber polymer.
A method for removing heat during emulsion polymerization is not particularly limited, but a method in which a jacket is provided around the reactor and a temperature-adjustable cooling water is circulated in the jacket is preferable.

(Initial polymerization process)
In this invention, the preparation amount of the monomer in an initial stage polymerization process is 5 mass% or more and less than 10 mass% among all the monomers (100 mass%). When the charged amount of the monomer is less than 5% by mass of the total monomer, the number of diene rubber polymers formed tends to vary from batch to batch, and the reproducibility of the diene rubber polymer is lowered. . When the monomer charge exceeds 10% by mass of the total monomer, the amount of unreacted monomer in the initial polymerization step increases, and the maximum pressure reached when temperature control in the reactor cannot be controlled. May grow.

  When the diene monomer is the main component, it is necessary to polymerize the diene monomer by liquefying under high pressure using a pressure resistant reactor, so that the polymerization temperature is limited in relation to the reactor pressure resistance. Therefore, it is usually necessary to start the polymerization by setting the polymerization temperature so that the pressure in the reactor becomes equal to or lower than the normal pressure of the reactor. For safety reasons, it is important that the monomer charge in the initial stage of polymerization is an amount that does not exceed the pressure resistance of the reactor even if a runaway reaction occurs in the initial stage of polymerization. The runaway reaction occurs when the heat generated by the polymerization increases the temperature in the reactor when the heat generated by the polymerization cannot be removed. Therefore, the smaller the amount of unreacted monomer at the start of the runaway reaction, the smaller the amount of heat generated by the polymerization. Therefore, the temperature in the reactor is not relatively high, and the reaction is stopped relatively quickly. In such a system, when the unreacted monomer decreases, the pressure in the reactor usually starts to decrease.

Therefore, in the present invention, the polymerization temperature is increased from the previously proposed semi-batch polymerization method by allowing the polymerization to proceed in a state where the pressure in the reactor is lowered in consideration of the cause of the runaway reaction. I found out that I can make it. In the reactor during the polymerization reaction of a butadiene monomer that is a high-pressure gas, the polymerization proceeds in a state where gas-liquid equilibrium is established. However, when the polymerization reaction proceeds and the amount of monomer decreases, the balance of gas-liquid equilibrium is lost, and the pressure in the reactor drops. This pressure drop generally begins when 50-60% by weight of the total monomer has been converted to a polymer. When the pressure starts to drop, increasing the polymerization temperature will not increase the pressure rapidly unless the monomer is added again.
In other words, when the monomer charged in the initial polymerization process reacts, the amount of unreacted monomer is greatly reduced, thereby making it difficult for the runaway reaction to occur, thereby reducing the decrease in the pressure in the reactor. Since it can be caused in time, the polymerization temperature can be raised from the initial stage of polymerization.

(Drip polymerization process)
In the present invention, the amount of the monomer dropped during the dropping polymerization step is 90% of the remainder of the monomer not charged in the initial polymerization step, that is, out of the total monomer (100% by mass). It is at least mass% and less than 95 parts by mass.

  In the present invention, the dropping of the remainder of the monomer is started when the conversion rate of the monomer charged in the initial polymerization step to 70% by mass to 70% by mass. If dropping of the remainder of the monomer is started in a state where the conversion is less than 70% by mass, the pressure increase value when the runaway reaction occurs may exceed the pressure resistance of the reactor. If the dropping of the remainder of the monomer is started in a state where the conversion rate exceeds 85% by mass, the stability of the polymer in the reactor is lowered, and cullet may be generated.

In the present invention, during the appropriate polymerization step, the monomer in the reactor (the sum of the monomer charged in the initial polymerization step and the monomer dropped in the dropping polymerization step) is polymerized. It is necessary to drop the monomer at a dropping rate such that the conversion rate of is always 70 to 85% by mass.
When the conversion rate of the monomer into the polymer in the reactor is less than 70% by mass, the pressure may increase because the pressure has not sufficiently decreased. When the conversion ratio of the monomer in the reactor to the polymer exceeds 85% by mass, the stability of the polymer in the reactor is lowered and cullet may be generated, which is not preferable.

  If the dropping rate is controlled so that the conversion rate of the monomer in the reactor into the polymer falls within this range, the pressure will drop, so the pressure in the reactor will be within the normal pressure from the start of polymerization. Can be maintained. As a method for determining the dropping rate, the dropping rate may be determined while measuring the conversion rate during the polymerization, or if the polymerization rate of the diene monomer is known in advance, the dropping rate may be determined. It can also be determined by determining the optimum dropping rate from the relationship between the amount of the monomer and the polymerization rate. In addition, the dropping of the monomer in the present invention is as long as the dropping rate of the monomer, that is, the dropping amount per unit time is such that the conversion rate of the monomer is 70 to 85% by mass, It may be performed continuously or intermittently.

  In the proper polymerization step, dropping 60 parts by mass or less of water together with the monomer with respect to 100 parts by mass of the total monomer removes heat in the reactor using the sensible heat of the dropwise addition of water. It is preferable in that When the amount of water dripped together with the monomer exceeds 60 parts by mass with respect to 100 parts by mass of all monomers, the amount of water initially charged decreases, so that the composition in the reactor cannot be stirred, and the particles The reproducibility in the polymerization behavior during the production period tends to decrease.

  The particle size of the diene rubber polymer thus obtained is preferably 80 to 400 nm, more preferably 100 to 300 nm, and still more preferably 120 to 300 nm in terms of mass average particle size. When the mass average particle diameter of the diene rubber polymer is smaller than 80 nm, sufficient impact resistance cannot be obtained. When the mass average particle diameter of the diene rubber polymer exceeds 400 nm, the transparency is lowered.

When attempting to produce a diene rubber polymer having a mass average particle diameter of 120 nm or more, the polymerization rate of the diene monomer is slow. Therefore, the method for producing a diene rubber polymer of the present invention can sufficiently exert its effect when producing a diene rubber polymer having a mass average particle diameter of 120 nm or more.
The diene rubber polymer in the present invention means a polymer containing 60 to 100 parts by mass of diene monomer units such as butadiene and isoprene in at least a polymer (100% by mass).

  The present invention will be described below based on examples. The part in an Example and a comparative example represents a mass part unless there is particular notice. Moreover, the pressure was represented by a gauge pressure.

[Mass average particle diameter]
The mass average particle size of the diene rubber polymer was determined from a capillary type particle size distribution meter.
[Measurement of conversion]
The conversion during polymerization was measured by collecting approximately 20g of the contents of the reactor from the open / close valve at the bottom of the autoclave into a sample bottle containing a small amount of polymerization inhibitor. After putting in the gear oven set to 180 degreeC for 30 minutes, mass was measured again, and solid content (mass%) was measured from the mass difference. And the value of the measured solid content was substituted into the following (1) formula, and the conversion rate was obtained. Here, in the formula (1), the monomer mass, the water mass, the nonvolatile content mass and the butadiene mass are the amounts of the monomer, water, nonvolatile content and butadiene charged and dropped into the reactor. Specifically, “min” refers to a catalyst used for polymerization of sodium pyrophosphate, ferrous sulfate, disodium ethylenediaminetetraacetate and the like.

[Example 1]
(Initial polymerization process)
A jacketed 70 L autoclave (reactor pressure 1.0 MPa, normal pressure 600 kPa) was charged with the initial charge composition shown in Table 1, the jacket circulating water temperature was set to 80 ° C., and the temperature inside the reactor was increased to 50 ° C. At that time, the catalyst shown in Table 1 was put into the reactor to start polymerization, and the polymer was sampled from the autoclave every 1 hr, and the conversion rate was measured. Further, the temperature was raised by adjusting the jacket circulating water so that the temperature in the reactor became 72 ° C. at 1.0 hr from the start of polymerization.

(Drip polymerization process)
From 1.0 hour after the start of polymerization, the dropping composition shown in Table 1 was added dropwise so that the conversion ratio of the monomer in the reactor to the polymer was 75% by mass. The dropping speed at this time is the dropping speed shown in Table 1, and this was dropped over 3.3 hours. At that time, the jacket circulating water was adjusted so that the temperature in the reactor was 72 ° C.

After the completion of the addition, an additional initiator shown in Table 1 was added every 1 hr, and the polymerization was completed 6.7 hr after the completion of the addition.
The maximum pressure during polymerization in the reactor was 574 kPa, which was within the normal pressure. The conversion ratio of the monomer was 96.8% by mass. Moreover, the mass average particle diameter of the diene rubber polymer after completion of the polymerization was 0.16 μm. The amount of cullet in the reactor was 0.1% by mass with respect to the monomer mass used. The results are shown in Table 2.

[Comparative Example 1]
In the dropping polymerization step, except that the dropping rate was set as shown in Table 3 so that the conversion rate of the monomer in the reactor to the polymer was 60% by mass, and the dropping time was changed to 2.5 hr, The same method as in Example 1 was used. As a result, the pressure in the reactor exceeded the normal pressure at 2.0 hr from the start of polymerization and increased to 696.7 kPa at 3.0 hr from the start of polymerization. The total polymerization time was 6.9 hr, and the monomer conversion was 96.9% by mass. Moreover, the mass average particle diameter of the diene rubber polymer after completion of the polymerization was 0.16 μm. The amount of cullet in the reactor was 0.1% by mass with respect to the monomer mass used. The results are shown in Table 4.

[Comparative Example 2]
(Initial polymerization process)
The jacketed 70L autoclave (reactor pressure 1.0 MPa, normal pressure 600 kPa) was charged with the initial charge composition shown in Table 5, the jacket circulating water temperature was set to 80 ° C., and the temperature inside the reactor was increased to 50 ° C. At that time, the catalyst shown in Table 5 was introduced into the reactor to start polymerization, and the temperature was raised until the temperature in the reactor reached 72 ° C.

(Drip polymerization process)
From 1.3 hours after the start of the polymerization, the dropping composition shown in Table 5 was added dropwise so that the conversion ratio of the monomer in the reactor to the polymer was 70% by mass. The dropping speed at this time is the dropping speed shown in Table 5, and this was dropped over 2.7 hr. At that time, the jacket circulating water was adjusted so that the temperature in the reactor was 72 ° C.

After the completion of dropping, the additional initiator shown in Table 1 was added every 1 hr, and the polymerization was completed 6.9 hr after the end of dropping.
The conversion ratio of the monomer was 96.7% by mass. The maximum pressure during the polymerization in the reactor rose to 639.7 kPa, which exceeds the normal pressure. Moreover, the mass average particle diameter of the diene rubber polymer after completion of the polymerization was 0.16 μm. The amount of cullet in the reactor was 0.1% by mass with respect to the monomer mass used. The results are shown in Table 6.

[Comparative Example 3]
In the dropping polymerization step, except that the dropping rate was set as shown in Table 7 so that the conversion ratio of the monomer in the reactor to the polymer was 90% by mass, and the dropping time was changed to 3.8 hr, The same method as in Example 1 was used. As a result, the maximum pressure in the reactor was 512.3 kPa. The total polymerization time was 6.9 hr, and the monomer conversion rate was 96.8% by mass. Moreover, the mass average particle diameter of the diene rubber polymer after completion of the polymerization was 0.16 μm. The amount of cullet in the reactor was 1.2% by mass relative to the mass of the monomer used. The results are shown in Table 8.

[Comparative Example 4]
(Initial polymerization process)
The initial charge composition shown in Table 9 was charged into a 70 L autoclave (reactor pressure resistance 1.0 MPa, normal pressure 600 kPa), and the temperature was increased. When the temperature reached 50 ° C., the catalyst shown in Table 9 was placed in the reactor. The polymerization was started to start polymerization, and the temperature in the reactor was increased to 62 ° C.

(Drip polymerization process)
From 1.2 hours after the start of the polymerization, the dropping composition shown in Table 9 was added dropwise so that the conversion ratio of the monomer in the reactor to the polymer was 60% by mass. The dropping speed at this time is the dropping speed shown in Table 9, and this was dropped over 4.0 hr. At that time, the jacket circulating water was adjusted so that the temperature in the reactor was 62 ° C.

After the completion of dropping, an additional initiator shown in Table 1 was added every 1 hr, and the polymerization was completed 9.0 hr after the end of dropping.
The monomer conversion was 96.1% by mass. The maximum pressure during polymerization in the reactor was 585.7 kPa. Moreover, the mass average particle diameter of the diene rubber polymer after completion of the polymerization was 0.16 μm. The amount of cullet in the reactor was 0.1% by mass relative to the mass of the monomer used. The results are shown in Table 10.

  In Example 1, the amount of the monomer in the initial polymerization step is 8.0% by mass of the total monomer (100% by mass), and the monomer in the reactor in the dropping polymerization step is added to the polymer. By setting the conversion rate to 75 to 80% by mass, the polymerization could be completed at a pressure lower than the normal pressure of the reactor.

  In Comparative Example 1, since the conversion ratio of the monomer in the reactor to the polymer in the dropping polymerization step was controlled to be 60 to 65% by mass, the pressure in the reactor became larger than the normal pressure. Oops. Therefore, when carrying out the polymerization under the conditions of Comparative Example 1, it was necessary to lower the temperature in the reactor and carry out the polymerization. By reducing the temperature in the reactor, the polymerization rate becomes slow, and the polymerization time becomes slow compared to Example 1.

  In Comparative Example 2, since the amount of the monomer in the initial polymerization step was 20% by mass of the total monomer (100% by mass), the maximum pressure in the reactor during the polymerization increased to 639.7 kPa. . This is because the amount of unreacted monomer in the reactor is larger than that in Example 1, and it is necessary to lower the temperature in the reactor during polymerization as in Comparative Example 1 to perform polymerization. Is longer than that of the first embodiment.

  In Comparative Example 3, the amount of the monomer in the initial polymerization step is 8.0% by mass of the total monomer (100% by mass), and the monomer in the reactor in the dropping polymerization step is added to the polymer. Polymerization was carried out while controlling the conversion rate to be 90 to 95% by mass. Although the result that the pressure in the reactor was smaller than that in Example 1 was obtained, the cullet in the reactor after the completion of polymerization increased 12 times compared with Example 1. An increase in cullet per polymerization will place a burden on cleaning in the reactor and may result in reduced productivity.

  In Comparative Example 4, the polymerization was carried out with the polymerization temperature lowered to 62 ° C. so that the pressure in the reactor did not exceed the normal pressure. Compared with Example 1, the polymer finally obtained was almost equivalent, but the polymerization time was 9 hr, which is disadvantageous in terms of productivity.

According to the method for producing a diene rubber polymer of the present invention, in a polymerization reaction of a diene monomer or a monomer mixture containing a diene monomer as a main component, a reactor from the start of polymerization to the end of polymerization. The internal pressure can be kept constant without raising the pressure beyond the normal pressure of the reactor, and the polymerization time can be greatly shortened. Such a method for producing a diene rubber polymer is industrially useful.

Claims (2)

A method for producing a diene rubber polymer by emulsion polymerization of a monomer containing a diene monomer,
5% by mass or more and less than 10% by mass of all the monomers (100% by mass) are charged into the reactor at a time, and the single monomer is used until the conversion rate of the monomer to the polymer becomes 70 to 85% by mass. An initial polymerization step for polymerizing the body,
Subsequent to the initial polymerization step, a dropping polymerization step in which the remaining monomer is dropped into the reactor and polymerized, and
The diene rubber weight is characterized in that the monomer is dropped at a dropping rate so that the conversion rate of the monomer into the polymer in the reactor is always 70 to 85% by mass during the appropriate polymerization step. Manufacturing method of coalescence. 2. The method for producing a diene rubber polymer according to claim 1, wherein in the dropping polymerization step, 60 parts by mass or less of water is dropped together with the monomer with respect to 100 parts by mass of all monomers.