JPS623165B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a styrene/maleic acid based low polymer having a low content of α-alkyl substituted styrene homolow polymer. It is well known that alternating copolymers are obtained by polymerizing styrenes and maleic anhydride in the presence of radical polymerization catalysts, but the resulting polymers usually have extremely high softening points of 200°C or higher. However, its use is limited due to its poor compatibility with other resins such as epoxy resins and alkyd resins. On the other hand, it is also known that styrene/maleic acid-based low polymers can be obtained by reacting α-alkyl-substituted styrene and maleic anhydride in the absence of a radical polymerization catalyst. There is a method shown in Publication No. 8538. This is a method in which α-alkyl-substituted styrene is slowly added to maleic acid heated to 160-200°C, but according to this method, maleic acid is not involved along with the styrene-maleic acid-based low polymer as the main component. A considerable amount of a homopolymer of α-alkyl-substituted styrene was also produced as a by-product, and when the product was cooled after the reaction, the surface of the precipitated solid (styrene/maleic acid-based low polymer) appeared on the surface of the homopolymer of α-alkyl-substituted styrene. A phenomenon in which the coalescence oozes out in the form of oil, or in some cases, the oil layer separates, is observed. This α-alkyl-substituted styrene homopolymer does not have acid anhydride groups in its molecules, so styrene/maleic acid-based low polymers containing a large amount of this homopolymer can be used as crosslinking agents (curing agents) for epoxy resins. ), there were problems in that the crosslinking density was low, the curing speed was slow, and the performance of the cured product was significantly lowered due to insufficient curing. A possible solution to this problem is to remove the homopolymer by vacuum distillation or the like after the reaction between α-alkyl-substituted styrene and maleic anhydride is completed. However, in this method, since the vapor pressure of the α-alkyl substituted styrene homopolymer is extremely low, it is necessary to distill it at a temperature of at least around 200°C and a vacuum degree of mmHg. Because styrene/maleic acid-based low polymers have sublimation properties, not only do the low polymers sublimate at the same time, reducing the yield, but the sublimate adheres to condensers, etc., and solidifies. The problem is that it becomes very difficult to manage. Based on this, the present inventors
As a result of various studies in order to solve the above-mentioned problems in the production of maleic acid-based low polymers, the above-mentioned It was discovered that styrene-maleic acid-based low polymers can be efficiently produced without any problems, leading to the present invention. That is, in the present invention, a mixture of α-alkyl-substituted styrene and styrene (hereinafter referred to as styrenes) having a molar ratio of 9:1 to 4:6 and maleic acids are mixed, and a molar ratio of the mixture to maleic acids is 1:1. 1~
This is a method for producing a styrene-maleic acid based low polymer, which is characterized by carrying out the reaction at a ratio of 1:5 at a reaction temperature of 130° C. or higher and in the absence of a radical polymerization catalyst. The α-alkyl substituted styrene used in the present invention has the general formula A styrene compound represented by the formula, where R is a lower alkyl group having 1 to 4 carbon atoms (particularly a methyl group)
and X ₁ and X ₂ are not particularly limited, and each independently represents hydrogen, halogen (e.g., chlorine, bromine), aryl group (e.g., phenyl, tolyl, xylyl), aralkyl group (e.g., benzyl, phenethyl), or alkyl group. (e.g. methyl, ethyl,
propyl, butyl), cycloalkyl groups (e.g. cyclohexyl), etc. Specific compounds include α-methylstyrene, α・2
-dimethylstyrene, α・3-dimethylstyrene, α・4-dimethylstyrene, α・2,4-trimethylstyrene, α-methyl-4-chlorostyrene, α-methyl-4-tertiary-butylstyrene, etc. or these A mixture of the following may be mentioned. In addition, the maleic acids used in the present invention have the general formula It is a maleic acid compound represented by here,
X and Y are each independently a hydroxyl group, a halogen such as chlorine, bromine, or -OR, and R is an alkyl group such as methyl, ethyl, propyl, butyl, a cycloalkyl group such as cyclohexyl, or a cycloalkyl group such as phenyl, tolyl, xylyl, etc. Examples include aryl groups and aralkyl groups such as benzyl and phenethyl. Of course, in the above formula, X and Y
They do not need to be the same, and there is no problem even if they are the same or different. It may also be a so-called acid anhydride in which X and Y are combined to form an oxygen (O) bond. There are no special limitations on the substituents R ₁ and R ₂ ,
For example, hydrogen, halogens such as chlorine, bromine, alkyl groups such as methyl, ethyl, propyl, butyl,
These include cycloalkyl groups such as cyclohexyl, aryl groups such as phenyl, tolyl, and xylyl, and aralkyl groups such as benzyl and phenethyl.
R ₁ and R ₂ may be the same or different. Specific examples of such maleic acids include maleic anhydride, maleic acid, maleic acid monochloride, maleic acid dichloride, propyl maleic anhydride, 1,2-diethyl maleic anhydride, benzyl maleic anhydride, and cyclohexyl maleic anhydride. acid, maleic acid monoethyl ester, maleic acid monobutyl ester, maleic acid monooctyl ester, maleic acid monobenzyl ester, maleic acid monophenyl ester, maleic acid monocyclohexyl ester,
Examples include diethyl maleate, dibutyl maleate, and mixtures thereof, but are not limited to these. Other compounds that decompose and rearrange to the compounds exemplified above during the reaction may also be used as substances with the same effect as these compounds. The styrenes used in the present invention have a mixing molar ratio of α-alkyl substituted styrene and styrene of 9:
It is necessary that the ratio be in the range of 1 to 4:6. α−
If the amount of alkyl-substituted styrene is more than this, α-
Homopolymer of alkyl-substituted styrene tends to be produced in large quantities, while if α-alkyl-substituted styrene becomes less than this, homo-polymer of α-alkyl-substituted styrene becomes difficult to produce, but styrene/maleic acid-based Simultaneously with the formation of the polymer, a high molecular weight substance is formed in an amount comparable to this low polymer. In the former case, the high content of α-alkyl-substituted styrene homopolymer in the product reduces the performance of the cured product when used as a crosslinking agent, and in the latter case, the resulting polymer The molecular weight substances include those with a molecular weight of 10,000 or more, and the softening point of the resulting resin becomes high, making it difficult to react in a solvent-free system, complicating the manufacturing process such as solvent selection and recovery, and increasing the molecular weight. As a result, solubility in solvents and compatibility with other resins decreases, resulting in extremely poor workability. However, when the mixing molar ratio is within the range specified in the present invention, the amount of homopolymer of α-alkyl substituted styrene produced is small, the amount of the high molecular weight product is also small, and the molecular weight is approximately 5000. It has the following properties, so it has excellent workability. In the present invention, the reaction molar ratio of styrenes and maleic acids is such that 1 maleic acid is added to the total mole of α-alkyl substituted styrene and styrene.
The amount is preferably 1.2 to 3 times by mole, more preferably 1.2 to 3 times by mole. If the amount of maleic acids is less than this range, a large amount of a homopolymer of α-alkyl-substituted styrene will be produced, and if it is more than this range, a large amount of unreacted maleic acids will remain, which is undesirable. As for the reaction temperature, the lower the temperature, the slower the production rate of styrene/maleic acid-based low polymers, and the relatively larger amount of high molecular weight products produced.Moreover, the lower the reaction temperature, the higher the molecular weight of the high molecular weight products. , the reaction temperature is preferably as high as possible, and the minimum
130℃ is necessary. As for the reaction method, since this reaction is a reaction in which the production of styrene/maleic acid-based low polymers and the production of α-alkyl-substituted styrene homopolymer compete with each other, styrenes are mixed into heated maleic acids. It is preferable to carry out the reaction while preparing and adding the styrene, and to lower the concentration of α-alkyl-substituted styrene in the reaction system as much as possible to reduce the formation of a homopolymer of α-alkyl-substituted styrene. The addition method in this case may be continuous or intermittent (intermittent), and the longer the addition time is, the more preferable it is from the above-mentioned purpose, but considering each reaction condition, economic efficiency, etc. To be determined accordingly. Thus, the styrene-maleic acid-based low polymer produced by the method of the present invention has an overwhelmingly large amount of components with a molecular weight of 1000 or less, and has an extremely low softening point compared to ordinary styrene-maleic acid-based copolymers.
In the range of 80-140℃. Therefore, it has good solubility in solvents and compatibility with other resins, and is excellent in workability. Styrene-maleic acid based low polymers having such characteristics are useful as curing agents for resins having epoxy groups or hydroxyl groups. Examples of such resins include, but are not limited to, epoxy resins, acrylic resins, polyester resins, alkyd resins, polyvinyl alcohol, and saponified products of ethylene/vinyl acetate copolymers. The present invention will be explained below with reference to Examples. Note that the numbers in the middle part of the example and % are weights. Example 1 706 parts of maleic anhydride was charged into a four-necked flask equipped with a stirrer and a thermometer, and the internal temperature was raised to 180°C. Subsequently, while maintaining this temperature, a mixture of 423 parts of dimethylstyrene and 83 parts of styrene was added dropwise over 8 hours. After completion of the dropping, the mixture was kept at an internal temperature of 180°C for 1 hour. A product with a softening point of 95° C. was obtained here. Table 1 shows the results of component analysis of the product by GPC. *What we call dimethylstyrene here is α・4-
It is a mixture of dimethylstyrene and α.2-dimethylstyrene in a composition ratio of approximately 6:4. Examples 2 to 7 and Comparative Examples 1 to 5 were also carried out in the same manner as in Example 1. The results are shown in Tables 1, 2 and 3.

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Claims (1)

[Claims] 1. A mixture of α-alkyl substituted styrene and styrene in a molar ratio of 9:1 to 4:6 and maleic acids;
1:5, a reaction temperature of 130° C. or higher, and a method for producing a styrene-maleic acid-based low polymer, characterized in that the reaction is carried out in the absence of a radical polymerization catalyst. 2. The method according to claim 1, wherein a mixture of α-alkyl substituted styrene and styrene is reacted while being added to maleic acids.