KR970009238B1 - Method of degree of polymerization using olygomers - Google Patents

Abstract

The method is for controling degree of polymerization of polymers, in polymerization reaction of polymerizable monomers in free radicals, by employing oligomers of homo polymer type or random copolymer type as chain transfer agents or termination agents. AIBN of radical initiator is reacted with styrene monomers and methacrylate monomer in ethyl acetate, oligomers of homo polymer type or random copolymer type are added in an amount of 0.01 to 5 mole% based on the quantity of monomers, and reacted at 70 deg. C under the nitrogen atmosphere to provide the method for controling degree of polymerization of polymers.

Description

Method for Controlling Polymerization Using Oligomer

The present invention relates to a method for controlling the degree of polymerization of various polymers by using homo- or random copolymer-type oligomers in the polymerization of free radically polymerizable monomers.

When a polymer is obtained from a polymerization system in which polymerization is initiated by a free radical initiator, the polymer obtained here needs to be controlled to have a degree of polymerization depending on the purpose of use and need. This molecular weight control problem arises especially when certain polymers need to be molded in very delicate and complex molds or when trying to prevent polymer chains from being oriented by polymer solution flow. In addition, the molecular weight control of the polymer is very important when trying to maintain a low viscosity while maintaining a high solid content, such as paint or paint.

Polymerization systems in which polymerization is initiated by free radical initiators generally produce polymers of high molecular weight, where the molecular weight is determined by several factors involved in the polymerization, as shown in the following formula (1).

Where k _p is the polymerization rate constant of the polymerization point, k _t is the polymerization stop rate constant, k _d is the decomposition rate constant of the initiator, f is the efficiency of the initiator, [I] is the concentration of the initiator, and [M] is Concentration. As can be seen from the above equation, to properly reduce the degree of polymerization, each factor must be adjusted appropriately. But each method has its own problems,

1) Increasing the concentration of the initiator is an uneconomic disadvantage due to the consumption of a large amount of initiator,

2) There is a method to increase k _d by increasing the polymerization temperature, which causes a large energy loss from the high polymerization temperature.

3) There is also a method of increasing the k _t by adding a thiol-based chain transfer agent, in which a problem is that the produced thiol-containing polymer is inferior in durability and odor may occur because it is a sulfur derivative.

To remedy these shortcomings, N. S. Enikolopyan et al. J. Polym. Sci., Chem. Ed., Vol. 19, 879 (1981) published a study on the molecular weight of PMMA and PS using cobalt (II) porphyrin compounds. A. F. Burczyk et al. Sci., Chem. Ed., Vol. 22, 3255 (1984) published a study on PMMA molecular weight control using cobalt oximes. In addition, Carlson et al. In US Pat. No. 4,526,945 and A. H. Janowicz et al. In US Pat. No. 4,680,352 report on the control of the molecular weight of styrene and methacryl-based polymers using similar coblat compounds. The advantage of the polymerization system by such a cobalt compound is that the cobalt compound required is a small amount. However, these compounds are generally unstable in air and have limitations in the selection of monomers and initiators that can be applied and have the disadvantage that they can color the polymerization system and thus affect the color of the resulting polymer. Especially when the products obtained by increasing the polymerization yield are directly connected to the product without pretreatment, such as in bulk polymerization, suspension polymerization or emulsion polymerization, these catalysts are used due to the thermal and light stability, discoloration or color caused by the presence of these catalysts. Although there is a need to remove them, there is a disadvantage that it is practically impossible to remove them.

Therefore, in this study, as a result of intensive studies to improve the above disadvantages, it was found that oligomo having a special structure acts as a chain transfer agent, and that the oligomers can overcome the disadvantages of the conventional chain transfer agents. okay. That is, the present invention relates to the use of a homopolymer-type or random copolymer-type molecular structure as in formula (2) as a chain transfer agent or a stopper.

Where Z is X or Y, X or Y = -COOR, -CN, -CONR'R, R is C1-C8 alky1, 2-hydroxyethyl, allyl, dimethylaminoethyl, glycidyl, Arylalkyl, one of H, R ', R is C1-8 alkyl or H, Ar is phenyl or C1-4 alkylphenyl, 1 + m + n = 1-20, m + n = 1-20, n = 1-20

Similar compounds are mainly applied to kraft polymerization with other monomers. P. Cacioli et al., J. Macromol, Sci. In Chem., A23, 839 (1986), there is an example of gragft copolymerization of MMA oligomer with ethyl acrylate, styrene, MMA, An, vinyl acetate, and the like. However, they did not comment on the control of molecular weight. In addition, H. Tanaka et al. J. Polymer Sci. Part A: Polymer Chem. vol. 27, 1741 (1989) (thermally) decomposed dimethyl 2,2'-azobisiso butylate to obtain dimer form of MMA (n = 1, 1 = m = 0, Y = -COOCH ₃ ) and dimethyl tetramethylsuccinate about 3/7. Attempts were made to copolymerize this mixture with monomers such as styrene, scrylonitrile, methacrylonitrile, methyl acrylate, methyl methacrylate, methyl vinyl ketone, and methyl isopropenyl ketone. In this attempt, they found that the presence of the mixture reduced the polymerization kinetics, suggesting that it was due to the possibility that oligomo could be added to the polymer chain ends. In addition, they synthesized Compound (2) (1 = 0, m + n = 35, X = Y =-COOCH ₃ ) having a certain molecular weight and used instead of the low molecular weight mixture. However, even in these studies, molecular weight control has not been studied.

In the present invention, paying attention to the fact that the polymerization rate is lowered as described above, the reason for the study was carefully studied, and the system was refined and selected to obtain the results of this study. That is, as a result of increasing the purity of the compound of the general formula (2) and controlling the molecular weight well, it was found that they can act as a chain transfer agent in the polymerization of various vinyl monomers, and the chain transfer effect of the compound used is a kind of free radical initiator. I found it almost irrelevant.

On the other hand, the compound of formula (2) used in the present invention has a main component is a mixture of 1 + m + n = 1-20, n = 1-20, etc. in small amounts (5 mole% or less than the monomer to be polymerized) to function Say something you can do. That is to say, by addition of a small amount, the molecular weight of the target polymer can be M _n = thousands of thousands. Compounds of 1 + n + m20 may also be used as part of the compound, which has a lower value per unit weight than the main component.

The radical initiators used are Azo compounds such as Azobisisobutyronitrile (AIBN), 2,2'-azobis (2-methyl) butanenitrile, 4,4'-azobis (4-cyanovaleric acid), 2- (t-butylazo) -2-cyanopropane , t-butylhydroxy-peroxide, benzoyl peroxide, t-butyl peroxide, cumyl peroxide, lauroyl peroxide, cumyl hydroperoxide, peroxide such as t-bytyl peracetate, acetyl peroxide, or persulfate. Therefore, the half life is preferably about 1 to 4 hours, and is determined according to the solubility according to the choice of the polymerization system.

The present invention is also applicable to any polymerization method to which radical polymerization methods such as bulk polymerization, solution polymerization, suspension polymerization and emulsion polymerization can be applied, and the amount of the chain transfer agent of the compound of the formula (2) used is based on the amount of the monomer. About 0.01-5 mole% is suitable. The process can be carried out in any manner, either continuously or batchwise.

Monomers to which the present invention can be applied are all monomers capable of radical polymerization, and typical examples thereof include styrene monomer, methacrylate monomer, acrylate monomer, methacrylamide, acrylamide, vinyl acetate, diene monomer, acrylonitrile, methacrylonitrile, vinyl chloride. , vinyl ketones, isopropenyl ketones, vinyl oxazoline, isopropenyl oxazoline and allyl. In this case, monomers including functional groups that do not directly affect radical polymerization, such as acid glycidyl or hydroxyalkyl, may also be applied to the present invention.

In order to describe the present invention in detail, embodiments will be described below. The effects of the present invention are specifically shown by the examples described below.

Preparation Example 1

In a flack equipped with a reflux condenser, 400 g of MMA and 0.56 g of AIBN were added to 200 ml of ethyl acetate to prepare a solution, followed by 10 mg of coblat porphyrin catalyst. The solution was bubbling with nitrogen to remove air, reacted at about 85 ° C for about 5 hours, and treated with activated carbon to remove the catalyst. Removal of the solvent and MMA from the rotary evaporator yielded about 285 g of oligomer (about 70% yield). The GPC molecular weight determined based on polystyrene and MMA was number average molecular weight M _n = 473, weight average molecular weight Mw = 620, and molecular weight distribution M _w / M _n = 1.31.

Preparation Example 2

In the same manner as in Preparation Example 1, ⁵⁰ parts of normal-butyl methacrylate (nBMA), ⁵⁰ parts of MMA, and 10.8 × 10 ⁻² parts of AIBN were reacted at about 70 ° C. with the required amount of catalyst. The yield of oligomer was 69%, M _n = 349, M _w / M _n = 1.31.

Preparation Example 3

NBMA 100parts and AIBN 10.8 × 10 ⁻² parts were reacted with the required amount of catalyst at about 70 ° C. by the same method as Preparation Example 1. The yield of oligomer was 89%, M _n = 382, M _w / M _n = 1.12.

Preparation Example 4

50 parts of styrene and 0.1 parts of AIBN were reacted with the required amount of catalyst at about 70 ° C. by the same method as Preparation Example 1. The yield of oligomer was 67%, M _n = 408, M _w / M _n = 1.66.

Example 1

10 g of MMA monomer and 10 mg of AIBN are dissolved in 10 ml of ethyl acetate, and the oligomer synthesized in Preparation Example 1 is added in the required amount (C / M = oligomer / molu ratio of MMA). When reacted for about 3 to 5 hours in a nitrogen stream and precipitated in excess methanol to obtain PMMA, the molecular weight is controlled as shown in Table 1.

As shown in Table 1, the molecular weight of PMMA obtained in the polymerization system without an oligomer was M = 169600, M = 321200, and M / M = 1.89.

Example 2

10 g of styrene monomer and 10 mg of AIBN are dissolved in 10 ml of ethyl acetate, and the oligomer synthesized in Preparation Example 1 is added in the required amount (C / M = oligomer / styrene molu ratio). Reaction is carried out for about 24 hours at 70 ℃ under nitrogen stream and precipitated in excess methanol to obtain polystyrene, the molecular weight of which is controlled as shown in Table 2.

On the other hand, the polystyrene molecular weight obtained when superposition | polymerization advanced without an oligomer under the same conditions was M = 79200, M = 137100, and M / M = 1.73.

Example 3

2.46 g of styrene monomer and 7 mg of AIBN were dissolved in 3.5 ml of ethyl acetate, and then 1.06 mg of the oligomer synthesized in Preparation Example 1 was added (C / M = 0.09). Reaction was carried out for about 24 hours at 70 DEG C under nitrogen stream and precipitation in excess methanol yielded polystyrene, at which the molecular weight was M = 4560, M = 6010 and M / M = 1.32.

Example 4

Dissolve 9.1g of styrene monomer and 20mg of benzoyl peroxide in 10ml of ethyl acetate, and add the oligomer synthesized in Synthesis Example 1 as necessary. The reaction is carried out for about 24 hours at 70 ℃ under nitrogen stream and precipitated in excess methanol to obtain polystyrene, the molecular weight of which is controlled as shown in Table 3.

Example 5

Dissolve 8g of styrene monomer, 2g acrylonitrile monomer and 10mg of AIBN in 10ml of ethyl acetate, and add the oligomer synthesized in Synthesis Example 1 as necessary. Reaction with nitrogen at about 70 ° C. for 15 hours and precipitation in excess methanol yields a SAN (styrene-acrylonitrile) polymer, the molecular weight of which is controlled as shown in Table 4.

Example 6

10 g of ethyl acrylate and 10 mg of AIBN are dissolved in 10 ml of ethyl acetate, and the oligomer synthesized in Preparation Example 1 is added as necessary. When reacted for about 12 hours at 70 ° C. under a nitrogen stream, an ethyl acrylate polymer was obtained. The molecular weight was controlled as shown in Table 5.

Example 7

10 g of vinyl acrylate and 10 mg of AIBN are dissolved in 10 ml of ethyl acetate, and the oligomer synthesized in Preparation Examples 2 to 4 is added as necessary. When the reaction is carried out for a predetermined temperature and time under a nitrogen stream to obtain a polymer, the molecular weight is controlled as shown in Table 6.

Examples 8-10

10 g of styrene monomer and 10 mg of AIBN are dissolved in 10 ml of ethyl acetate, and the oligomer synthesized in Preparation Examples 2 to 4 is added as necessary. The reaction is carried out for a predetermined temperature and time under a nitrogen stream, and a polymer is obtained. The molecular weight is controlled as shown in Table 7.

* Reaction temperature about 70 ℃, reaction time about 24 hours

Claims (6)

A method for controlling the degree of polymerization of a polymer characterized by using a homopolymer type or a random copolymer type oligomer represented by the following general formula (2) in the polymerization of free radically polymerizable monomers. Where Z is X or Y, X or Y = -COOR, -CN, -CONR'R R is C1-C8 alky1, 2-hydroxyethyl, allyl, dimethylaminoethyl, glycidyl, Arylalkyl, one of H, R ', R is C1-C8 alkyl or H, Ar is phenyl or C1-C4 alkylphenyl , 1 + m + n = 1-20, m + n = 1-20, n = 1-20 The monomer of claim 1, wherein the polymerizable monomer comprises one or two or more of styrene, acrylonitrile, methacrylate, vinyl acetate, alkyl acrylate having 1 to 8 carbon atoms, and a monomer comprising a double bond. How to. The method of claim 1, wherein the initiator comprises an azo compound, a persulfate compound, a peroxide compound. The method of claim 1, wherein the oligomo comprises one or two or more mixtures selected from those having a value of 1 + m + n ≦ 20 in formula (2). The monomer comprising a double bond is acrylamide, diene monomer, vinyl ketone of alkyl having 1 to 6 carbon atoms, isopropenyl ketone of alkyl having 1 to 6 carbon atoms, vinyl oxazoline, isopropenyl oxazoline. How to include. The method of claim 1, wherein the amount of oligomer used comprises 0.01 to 5 mole% relative to the monomer.