JP2909554B2 - Method for controlling molecular weight of maleic anhydride-methyl vinyl ether copolymer - Google Patents

Description

The present invention relates to a method for controlling the molecular weight of a maleic anhydride-methyl vinyl ether copolymer.

More specifically, in the polymerization reaction, methyl vinyl ether, one of the monomers, is continuously charged during the polymerization reaction, and the maleic anhydride-methyl vinyl ether copolymer can easily control the molecular weight by adjusting the charged amount. The present invention relates to a method for controlling the molecular weight of coalescence.

The maleic anhydride-methyl vinyl ether copolymer is a linear water-soluble polymer electrolyte compound.

Recently, it has excellent non-toxicity to human body, long-term stability, adhesiveness, cohesiveness, water retention, and peelability.
It is applied in a wide range of industrial fields as a spray hair fixative, a builder of synthetic detergents, and the like.

In particular, those obtained by reacting a low molecular weight copolymer with various alcohols are used for these applications.

<< Prior art >> Conventionally, a maleic anhydride-methyl vinyl ether copolymer is prepared by charging a starting monomer, maleic anhydride and methyl vinyl ether, into a reactor as disclosed in JP-B-45-29193. It has been produced by a radical copolymerization reaction in an autoclave using a solvent such as benzene or benzene.

Next, the obtained polymer is taken out of the reactor in the form of a slurry, and the solvent is removed to produce a copolymer in the form of a powder or an anhydrous polymer dissolved in an excess of methyl vinyl ether without using a solvent. Maleic acid was polymerized while being vigorously tumbled in the powder bed, and after the reaction was completed,
A copolymer was produced by distilling off excess vinyl ether monomer.

JP-A-64-14222 discloses a method for producing a powdery copolymer by performing polymerization under pressure using methyl vinyl ether as a solvent.

The publication also discloses a method using a mixed solvent of 1,1,2-trichloro-1,2,2-trifluoroethane and methylene chloride.

In any of the methods, methyl vinyl ether, which is one of the monomers, was charged all at once before the start of polymerization, and then the polymerization reaction was performed.

When a maleic anhydride-methyl vinyl ether copolymer is produced, methyl vinyl ether is a volatile liquid having a boiling point of 5 ° C, and is in a gaseous state at a preferable polymerization temperature of 60 to 80 ° C.

In order to keep gaseous methyl vinyl ether in the reaction system, the reaction must be carried out in a closed system or it is necessary to add an excess of methyl vinyl ether sufficient to compensate for the amount lost by evaporation in a normal pressure system.

In order to produce a relatively low molecular weight grade, there are methods such as controlling the charged amount of the polymerization initiator, the polymerization temperature, and the added amount of the chain transfer agent.

<< Problems to be Solved by the Invention >> Among the above-mentioned methods for controlling molecular weight, when controlling using a reaction initiator, it was necessary to use a large amount of a reaction initiator (for example, lauryl peroxide or the like).

Specifically, for example, 1 to 3% of lauryl peroxide or the like is used for the resulting maleic anhydride-methyl vinyl ether copolymer.

Therefore, lauryl peroxide and the like are marketed while being necessarily mixed in the maleic anhydride-methyl vinyl ether copolymer as a product. Further, when used in a large amount, the reaction proceeds rapidly and generates heat, so that it is necessary to increase the capacity of the heat removing device. The method of controlling by the polymerization temperature requires a high-pressure facility in order to raise the temperature above the boiling point of the solvent used.

Further, in order to control the molecular weight using a chain transfer agent, it is necessary to select the type of the chain transfer agent according to the application.

For example, use of a thiol-based typical chain transfer agent is not preferable because a sulfur component is mixed in a product.

In view of the above situation, the present inventors have made intensive studies and completed the present invention.

<< Means for Solving the Problems >> That is, the present invention relates to a method for producing a maleic anhydride-methylvinyl ether copolymer, in which the entire amount of maleic anhydride supplied to the reaction is charged into a reactor, and A method for controlling the molecular weight of a maleic anhydride-methylvinyl ether copolymer, characterized by adding the maleic anhydride in a rate varying from 0.1 to 1.0 equivalent / hour relative to the total amount of maleic anhydride.

Incidentally, a reaction formula for producing a maleic anhydride-methyl vinyl ether copolymer is shown as follows.

[N is in the range of 10 to 100,000, and can be controlled by controlling the charged amount of the polymerization initiator, the addition rate of the methyl vinyl ether monomer, the polymerization temperature, and the added amount of the chain transfer agent.] The "method of controlling molecular weight of maleic anhydride-methyl vinyl ether copolymer" will be described in detail.

 First, a raw material is charged into a polymerization tank to perform a polymerization reaction.

In this polymerization tank, benzene is usually used as a dispersion solvent for a copolymer as a product, and maleic anhydride and methyl vinyl ether as starting materials are charged and a radical copolymerization reaction is carried out in the presence of a radical polymerization initiator.

The present invention is characterized in that one monomer previously charged, maleic anhydride, is charged with methyl vinyl ether, the other monomer, at a certain rate of charging.

Since methyl vinyl ether is a gas at a reaction temperature of 40 to 80 ° C., efforts have conventionally been made to charge the entire charge at once and then carry out the polymerization reaction in a closed pressurized system.

The point of the present invention is that pressure resistance is required by continuously adding methyl vinyl ether at a rate of 0.01 to 1.0 equivalent / hour with respect to the total charged amount of maleic anhydride from the bottom of the reaction vessel in the normal pressure open system during the polymerization reaction. To produce a maleic anhydride-methyl vinyl ether copolymer without using a reaction vessel to be used.

Furthermore, it is possible to produce a maleic anhydride-methyl vinyl ether copolymer having an arbitrary molecular weight by changing the charging rate of methyl vinyl ether to be charged continuously.

The charging rate of methyl vinyl ether is represented by the molar ratio to the number of moles of methyl vinyl ether continuously charged into the reactor per unit time and the number of moles of maleic anhydride previously charged in the reactor.

The charging rate of methyl vinyl ether varies depending on the molecular weight of the desired maleic anhydride-methyl vinyl ether copolymer, the amount of methyl vinyl ether dissolved in the reaction solvent, and the like, but is 0.1 to 1.0 equivalent / hour.

 More preferably, it is 0.1 to 0.3 molar equivalent / hour.

When the charged amount of methyl vinyl ether is continuously less than 0.1 molar equivalent / hour, the reaction time becomes longer, which is not convenient.

In addition, when continuously exceeding 1.0 molar equivalent / hour,
Methyl vinyl ether which evaporates from the liquid surface of the solvent without participating in the reaction increases, which is uneconomical.

It is better not to interrupt the addition of methyl vinyl ether until the molar ratio of methyl vinyl ether to the number of moles of maleic anhydride charged is 1/2 to 2/3.

The molecular weight of the maleic anhydride-methyl vinyl ether copolymer described in the present invention is actually measured by the specific viscosity.

 The measuring method of the specific viscosity is as follows.

1% using methyl ethyl ketone as a solvent for the copolymer
A solution having a (weight / volume, 25 ° C.) concentration is adjusted, and the fall time at 25 ° C. is measured using a capillary viscometer specified by JISK6726, and the calculated value is calculated by the following formula.

However, in the above formula, A = measured value of fall time for the copolymer solution B = measured value of fall time for the solvent

Since the value of the specific viscosity of a polymer having the same structural unit increases as the molecular weight increases, it is widely used as a standard for relatively expressing the molecular weight of the polymer.

Maleic anhydride obtained by the molecular weight control method of the present invention-
The molecular weight (specific viscosity) of the methyl vinyl ether copolymer is in the range shown in FIG.

In FIG. 1, the horizontal axis represents the charging rate of methyl vinyl ether continuously charged during the polymerization reaction.

 The unit of the horizontal axis is represented by equivalent / hour.

The vertical axis represents the molecular weight of the copolymer produced when the polymerization was carried out at the respective charging rates of methyl vinyl ether, as a specific viscosity.

Each ○ mark, △ mark, □ mark, as a polymerization initiator,
The polymerization was carried out using lauroyl peroxide, 2,2'-azobisisobutyronitrile, and benzoyl peroxide.

In any case, when the polymerization is carried out by clearly increasing or decreasing the charged amount of methyl vinyl ether, the specific viscosity (molecular weight) of the obtained copolymer can be controlled almost linearly.

In addition, the squares represent the methyl vinyl ether charge rates and the specific viscosities of the copolymers corresponding to the respective charge rates when the concentration of one of the monomers, maleic anhydride, was changed. Accordingly, even when the amount of maleic anhydride charged before the start of polymerization is changed, the specific viscosity (molecular weight) of the obtained copolymer can be controlled by increasing or decreasing the rate of charging methyl vinyl ether in the same manner. .

After completion of the reaction, the copolymer is taken out of the reactor in a slurry state.

<< Effects of the Invention >> The molecular weight control method of the present invention makes it possible to reduce the amount of a reaction initiator used during polymerization to 1/4 or less.

Therefore, the method of the present invention can meet the quality requirements of various grades.

Hereinafter, the method of the present invention will be described with reference to Examples and Comparative Examples.

Example 1 188 g of maleic anhydride and 2480 g of benzene were charged and dissolved in a 5-reactor having a stirrer, a reflux condenser and an internal temperature controller.

Thereafter, while maintaining the internal temperature at 80 ° C., methyl vinyl ether was continuously charged from the bottom of the reactor at a rate of 50 ml per hour (X ₁ equivalent / hour) to a total amount of Y ₁ ml.

4.8 g of benzene 80 of lauroyl peroxide as a polymerization initiator
The 0 ml solution was continuously charged at a rate of 50 ml per hour.

After performing the reaction for 6 hours, the inside of the reaction tube was cooled to obtain a copolymer slurry.

The solvent was removed from this slurry under reduced pressure to obtain a white powder.

 The specific viscosity of this copolymer was 0.62.

The reaction proceeded gently, and no sudden heat generation was observed.

Example 2 The reaction was carried out in the same manner as in Example 1.

However, the charging rate of methyl vinyl ether was 25 ml per hour (X ₂ equivalents / hour), and the total amount of Y ₁ ml was continuously charged.

After reacting for 10.5 hours, a copolymer having a specific viscosity of 0.28 was obtained.

Example 3 The reaction was carried out in the same manner as in Example 1. However, the charging rate of methyl vinyl ether was 78 ml per hour (X ₃ equivalents /
(Time), a total amount of Y ₃ ml was continuously charged.

After performing the reaction for 4.5 hours, a copolymer having a specific viscosity of 1.02 was obtained.

Example 4 The reaction was carried out in the same manner as in Example 1.

However, the polymerization initiator was changed to lauroyl peroxide,
9.6 g of 2'-azobisisobutyronitrile was used.

The charge rate of methyl vinyl ether is 46 per hour.
A total amount of Y ₄ ml was continuously charged in ml (X ₄ equivalents / hour).

After performing the reaction for 4.5 hours, a copolymer having a specific viscosity of 0.31 was obtained.

Example 5 The reaction was carried out in the same manner as in Example 4.

However, the charging rate of methyl vinyl ether was 26 ml per hour (X ₅ equivalents / hour), and the total amount of Y ₅ ml was continuously charged.

After reacting for 9 hours, a copolymer having a specific viscosity of 0.17 was obtained.

Example 6 The reaction was carried out in the same manner as in Example 4.

However, the charging rate of methyl vinyl ether was 72 ml per hour (X ₆ equivalents / hour), and the total amount of Y ₆ ml was continuously charged.

After performing the reaction for 3 hours, a copolymer having a specific viscosity of 0.55 was obtained.

Example 7 A reaction was carried out in the same manner as in Example 1.

However, 9.6 g of benzoyl peroxide was used instead of lauroyl peroxide as the polymerization initiator.

The charge rate of methyl vinyl ether is 46 per hour.
A total of ₇ ml of Y ( ₇ equivalents / hour) was continuously charged.

After reacting for 4 hours, a copolymer having a specific viscosity of 0.64 was obtained.

Example 8 The reaction was carried out in the same manner as in Example 7.

However, the charging rate of methyl vinyl ether was 26 ml per hour (X ₈ equivalents / hour), and the total amount of Y ₈ ml was continuously charged.

After performing the reaction for 6 hours, a copolymer having a specific viscosity of 0.33 was obtained.

Example 9 The reaction was carried out in the same manner as in Example 1.

However, maleic anhydride 282 g, lauroyl peroxide
9.6g was used.

The charge rate of methyl vinyl ether is 46 per hour.
A total amount of ₉ ml was continuously charged in ml (X ₉ equivalents / hour).

After reacting for 7 hours, a copolymer having a specific viscosity of 0.45 was obtained.

Example 10 The reaction was carried out in the same manner as in Example 4.

However, the charging rate of methyl vinyl ether was 24 ml per hour (X ₁₀ equivalents / hour), and the total amount of Y ₁₀ ml was continuously charged.

After performing the reaction for 14.5 hours, a copolymer having a specific viscosity of 0.24 was obtained.

Example 11 The reaction was carried out in the same manner as in Example 4.

However, the charging rate of methyl vinyl ether was 29 ml per hour (X ₁₁ equivalents / hour), and the total amount of Y ₁₁ ml was continuously charged.

After reacting for 9.5 hours, a copolymer having a specific viscosity of 0.33 was obtained.

Comparative Example 1 Into a pressure-resistant reaction tube having a capacity of 1 which had been cleaned in advance, 35.9 g of maleic anhydride, 557.9 g of benzene, and lauroyl peroxide were added.
Add 0.20g and dissolve. Attach the reactor to a 75 ° C oil bath.

When the temperature was stabilized, methyl vinyl ether was continuously charged with a high-pressure pump at 24.5 g (X ₁₂ equivalents / hour) in a total amount of Y ₁₂ ml.

The reaction solution after the polymerization reaction for 3 hours is transferred to an eggplant type flask, and BZ is removed by a rotary evaporator to obtain a white powder product.

After removing the solvent, a copolymer having a specific viscosity of 1.49 was obtained.

At this time, the polymerization pressure reached a maximum of 2.2 kgf / cm ² .

Comparative Example (Batch charging) 188 g of maleic anhydride and benzene were placed in a polymerization reactor 5 having a stirrer, a reflux condenser and an internal temperature controller in a tube.
2480 g was poured and dissolved.

After that, the internal temperature was maintained at 80 ° C.
Methyl vinyl ether was charged at a rate of 150 ml per hour.

14 g of dilauroyl peroxide as a polymerization initiator
Of benzene in 100 ml was charged over 1 hour.

 After polymerization for 2 hours, the reactor was cooled.

By removing the solvent from the obtained slurry under reduced pressure, a copolymer having a specific viscosity of 0.27 was obtained. Since a large amount of dilauryl peroxide was used in this polymerization reaction, the reaction proceeded in a short time, and severe heat generation was observed.

[Brief description of the drawings]

FIG. 1 is a graph showing the dependence of the specific viscosity (corresponding to the molecular weight) of the maleic anhydride-methyl vinyl ether copolymer produced in the above example on the charging rate of methyl vinyl ether, and the horizontal axis represents the methyl vinyl ether The charging speed and the vertical axis are numerical values of the specific viscosity.

Claims (1)

(57) [Claims] When a maleic anhydride-methyl vinyl ether copolymer is produced, the entire amount of maleic anhydride to be subjected to the reaction is charged into a reactor, and methyl vinyl ether is added in an amount of 0.1 to 1.0 with respect to the total amount of maleic anhydride. A method for controlling the molecular weight of a maleic anhydride-methyl vinyl ether copolymer, characterized in that the addition is carried out while being varied within a rate range of equivalent / hour.