JPS621962B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing modified liquid polyisoprene rubber by adding maleic anhydride to liquid polyisoprene rubber. Various studies have been conducted for a long time on the addition of maleic anhydride to solid diene rubbers such as natural rubber (NR) and isoprene rubber (IR).
By adding maleic anhydride to natural rubber, isoprene rubber, etc., it is possible to increase the unvulcanized strength of rubber compounds using them and the vulcanized adhesive strength of composites with metals, etc. It is known that this effect can be obtained. In addition, in recent years, many studies have been conducted on methods for producing low-molecular-weight polybutadiene by adding maleic anhydride to low-molecular-weight polybutadiene, and the resulting modified polybutadiene can be used as resin for paints, printing inks, etc. This technology has already been put into practical use. Recently, low molecular weight liquid polyisoprene rubber has been attracting attention, and due to its excellent fluidity, well-balanced adhesive strength and cohesive strength, etc., it can be used as a reactive plasticizer for solid rubber, adhesives, adhesives, and sealants. It is heavily used for this purpose. The present inventors have added maleic anhydride to this liquid polyisoprene rubber to obtain a modified liquid polyisoprene rubber.In addition to the properties of liquid polyisoprene rubber, the inventors have also achieved improved compatibility with polar polymers and improved compatibility with polar polymers. Various studies have been conducted on reactions in which a compound having a polar group such as maleic anhydride is added and introduced for the purpose of making a crosslinked product using a maleic acid group or making it water-soluble. Needless to say, the reaction of adding maleic anhydride to liquid polyisoprene rubber is a well-known technique as described above, but the present inventors discovered a surprising fact in the course of their investigation, and it was not until they completed the present invention. It was reached. That is, according to the present invention, the molecular weight is 8000~
When manufacturing modified liquid polyisoprene rubber by reacting maleic anhydride with liquid polyisoprene rubber having a molecular weight of 100,000 and a cis-1,4 bond content of 70% or more, unreacted polyisoprene rubber is produced by reacting in the presence of a phenol derivative. A modified liquid polyisoprene rubber can be obtained at an extremely high reaction rate to the extent that a step for removing maleic anhydride is not required. The ability to carry out the reaction at such a high reaction rate is extremely significant. In other words, in the conventional solution-based reaction between natural rubber or isoprene rubber and maleic anhydride,
The polymer concentration in the reaction system was extremely low, and the reaction rate in a normal reaction was extremely low. In addition, when producing an adduct of liquid polyisoprene rubber and maleic anhydride, the low viscosity of liquid polyisoprene rubber makes it easy to stir and mix with a simple tank-type stirrer. Since it is not necessary to use or even if it is used, only a small amount is sufficient, it is possible to carry out the reaction at a high polymer concentration, and the addition reaction of maleic anhydride can be carried out at a high reaction rate, but the reaction rate is at most 80%. Therefore, it was necessary to remove the remaining unreacted maleic anhydride. On the other hand, when a phenol derivative was present in the reaction system as in the present invention, the reaction rate of maleic anhydride reached almost 100%, and the unreacted maleic anhydride became almost negligible. This eliminates the need for the step of removing maleic anhydride and requires almost no reaction solvent, and is extremely significant industrially. Furthermore, since the reaction in the present invention is carried out at a relatively high temperature, liquid polyisoprene rubber causes significant deterioration, but the presence of a phenol derivative is extremely advantageous because it also exhibits the effect of suppressing deterioration. In addition, when the modified liquid polyisoprene rubber produced by the method of the present invention is actually used, it is often used with the addition of various antioxidants; Even without,
Alternatively, it also has the effect that even if it is used, it only needs to be used in a small amount. The liquid polyisoprene rubber used in the present invention has a molecular weight of 8,000 to 100,000 and a cis-1,4 bond content of 70% or more. If the molecular weight is lower than the above range, when the modified liquid polyisoprene rubber produced using it is mixed with other high molecular weight solid rubber, the physical properties of the resulting rubber compound may be significantly deteriorated. , there is no improvement effect on vulcanization adhesive strength. Further, a crosslinked product obtained by crosslinking only modified liquid polyisoprene rubber does not have sufficiently satisfactory physical properties. On the other hand, if the molecular weight is too high, the viscosity of the reaction system will become too high and the reaction will not proceed efficiently, and dispersion will be poor when mixed with other solid rubbers or when producing a crosslinked product with a crosslinking agent.
Not desirable. From this point of view, the molecular weight
Those with a molecular weight of 15,000 to 55,000 are more preferably used.
In addition, the molecular weight here means a viscosity average molecular weight (MV), and is a value calculated from the following formula by measuring the solid viscosity ([η]) at 30°C in toluene. [η]=1.21÷10 ^-4 MV ^0.77 Furthermore, the amount of cis-1,4 bonds in the liquid polyisoprene rubber used in ^the present invention must be 70% or more. Liquid polyisoprene rubber with an increased number of 3,4 bonds and an amount of cis-1,4 bonds that is lower than the above range is more likely to crosslink when heated, resulting in significant thickening or gelation during the reaction to add maleic anhydride. In addition, when it is made into a crosslinked product by a crosslinking reaction, it becomes a product with poor elasticity, and when mixed with other solid rubbers, there is a decrease in compatibility, and when it is made into a vulcanized product, there is a significant decrease in physical properties. This is not a good thing. Such liquid polyisoprene rubber is natural rubber or solid polyisoprene rubber (IR) obtained using Ziegler catalyst or lithium catalyst.
Liquid polyisoprene rubber can also be obtained by decomposing it at high temperature, but from the viewpoint of quality stability etc., it is most preferable to directly obtain liquid polyisoprene rubber by anionic living polymerization by controlling the amount of lithium-based catalyst. The phenol derivatives used in the present invention are monophenols, bisphenols, trisphenols, or derivatives thereof, and are used as antioxidants in the rubber and plastics industry, food industry, petrochemical products, and the like. Examples include 4,4-dioxydiphenyl, dioxydiphenyl methane derivatives, hydroquinone monobenzyl ether, 1,1-bis(4-hydroxyphenyl)-cyclohexane, 1
-oxy-3-methyl-4-isopropylbenzene 2,4,5-trihydroxybutyrophenone,
2,4-dimethyl-6-t-butylphenol,
2,4-di-t-butylphenol, 2,6-di-t-butylphenol, 2,5-di-t-amylhydroquinone, 2,5-di-t-butylhydroquinone, 2,6-di- t-Butyl-4-methylphenol, 4-hydroxymethyl-2,6-di-
t-butylphenol, 2,6-di-t-butyl-α-dimethylamino-4-methylphenol,
4,4'-bis(2,6-di-t-butylphenol), 2,2'-methylenebis(4-methyl-6-
t-butylphenol), 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 4,
4'-methylenebis(6-t-butyl-methylphenol), 4,4'-methylenebis(6-t-butyl-butylphenol), 6-t-butyl-3-
Derivative of methylphenol, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, 6-
Reaction product of t-butyl-4-methylphenol and sulfur dioxide, butylhydroxyanisole,
4,4'-butylidene bis(3-methyl-6-t-
butylphenol) 4,4'-thiobis(3-methyl-6-t-butylphenol), bis(3-methyl-4-hydroxy-5-t-butylbenzyl) sulfide, 4,4'-thiobis(6- t-butyl-2-butylphenol), 2,2'-thiobis(4-methyl-6-t-6butylphenol), thiobis(di-sec-amylphenol),
2,2'-dihydroxy-3,3'-di(α-methylcyclohexyl)-5,5'dimethyl diphenyl, 1,1,3'-trinu(2-methyl-4-hydroxy-5-t- (butylphenyl)butane, phenol condensates, styrenated phenols, fatty acid-modified substituted phenols, modified alkylated phenols, alkylated 4-methylphenols, alkylated styrenated phenols, methylene-bridged polyhydric alkylphenols, dialkyl phenols,
Included are sulfides, phenolic sulfides, alkylated bisphenols, high molecular weight phenols and their derivatives. These may be used alone or in combination of two or more. Depending on the type, there are those that cause phenomena such as blooming or migration in the modified liquid polyisoprene rubber produced in the present invention or its rubber compound, and those that sublimate and cause problems when using the modified liquid polyisoprene rubber. Care must be taken when selecting such materials, as some may have the adverse effect of deteriorating the working environment. From this point of view, phenol derivatives preferably used in the present invention include 2,6-di-t-butyl-4-methylphenol and 2,4-
Di-t-butylphenol, 2,4-dimethyl-
6-t-butylphenol, butylhydroxyanisole, styrenated phenol, 2,2'-methylbis(4-methyl-6-t-butylphenol), 4,4'-butylidenebis(3-methyl-6
-t-butylphenol), 44'-thiobis(3-
methyl-6-t-butylphenol), 2,5-
Di-t-butylhydroquinone, 1,1',3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, 1,1'-bis(4-hydroxyphenyl)cyclohexane, and their Examples include derivatives. Among these, 2,6
2,2'-methylenebis(4-methyl-6-t-
butylphenol), 44'-thiobis(3-methyl-6-t-butylphenol) and 4,4'-butylidenebis(3-methyl-6-t-butyl-6
O-t-butylphenol derivatives such as -t-butylphenol) are preferably used. Note that when liquid polyisoprene rubber and maleic anhydride were reacted without using a phenol derivative, the reaction rate reached only about 80% at most, and a higher reaction rate was not achieved. In the present invention, which uses a phenol derivative, the reaction rate of maleic anhydride reaches almost 100%, and the unreacted maleic anhydride can be ignored. In addition, there are various other phenol derivatives that act as antioxidants such as phenols, but surprisingly, they do not exhibit the effects observed in the present invention. That is, for example, when amines are used, the reaction rate is not sufficiently high, the resulting modified liquid polyisoprene rubber is heavily colored, and furthermore, there are various disadvantages such as a crosslinking reaction with the added maleic anhydride. occurs. In addition, in the method of the present invention, since a phenol derivative that also acts as an antioxidant is present in the reaction system, the effect of suppressing cooling of the liquid polyisoprene rubber is also exhibited, which is extremely advantageous. These phenol derivatives are preferably used in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of liquid polyisoprene rubber. If the amount used is less than 0.01 part by weight, the intended effect of the present invention will not be achieved, and if it is too much, it will show the effect of suppressing the deterioration of liquid polyisoprene rubber. This is not preferable because the acid reaction rate decreases. The reaction conditions for adding maleic anhydride to liquid polyisoprene rubber include a reaction time of 120~
The reaction time is 0.5~250℃, preferably 150~200℃
24 hours, preferably within the range of 1 to 12 o'clock. In particular, regarding the reaction temperature, if the reaction temperature is too low, the reaction will be slow and a significantly long reaction time will be required.On the other hand, if the reaction temperature is too high, problems such as side reactions such as decomposition of the liquid polyisoprene rubber may occur. Please note that this may occur. Further, it is not necessary to use a solvent during the reaction, but if it is used, it is important that the amount is such that the concentration of the liquid polyisoprene rubber is not too low. The solvents used here include aliphatic,
Alicyclic or aromatic hydrocarbons are preferably used, and those having a boiling point of about 70° C. or higher at normal pressure are preferably used in order to prevent the pressure of the reaction system from becoming too high. In the present invention, the amount of maleic anhydride added to the liquid polyisoprene rubber depends on the intended use of the modified liquid polyisoprene rubber, but is 0.1 to 30 mol% based on the isoprene monomer unit in the liquid polyisoprene rubber. It is preferable that it is in the range of . If the amount of maleic anhydride added is too small, the modification effect will not be exhibited, and if it is too large, problems such as significantly poor processability will occur when used in combination with high molecular weight rubber. The additionally introduced maleic anhydride can also be reacted with water, alcohol, ammonia, amine or epoxy compound to form maleic acid or areic acid derivatives. The modified liquid polyisoprene rubber obtained by the method of the present invention is a composite material with excellent plasticity of solid rubber, excellent vulcanization adhesion with metals and fibers, and an amine, epoxy compound, or By crosslinking with a crosslinking agent such as a metal oxide, it is widely used in applications such as solvent-free adhesives, adhesives, sealing materials, and potting materials. EXAMPLES The present invention will be specifically explained below with reference to Examples, but the present invention is not limited to these Examples in any way. Examples 1 to 3 When isoprene monomer is polymerized using sec-butyllithium as a catalyst, the molecular weight is 35,000.
A liquid polyisoprene rubber having a cis-1,4 bond content of 80% was obtained. This liquid polyisoprene rubber
8 g of each of the three types of phenol derivatives shown in Table 1 were added to 400 g, and the temperature was gradually raised to 150°C with gentle stirring, after which 30 g of maleic anhydride was added to each, and the temperature was raised to 190°C. The reaction was carried out at that temperature for 6 hours with stirring. After the reaction, unreacted maleic anhydride is extracted from the product with acetone, titrated with an aqueous caustic soda solution to determine the amount of unreacted maleic anhydride, and the maleic anhydride is added to the liquid polyisoprene rubber. The reaction rate was calculated. The results are shown in Table 1.

[Table] From Table 1, it can be seen that the addition rate of maleic anhydride in these Examples was all 99% or more, indicating that most of the added maleic anhydride participated in the reaction. It can also be seen that the liquid polyisoprene rubber has not undergone any modification other than maleic anhydride. Examples 4 to 6 Liquid polyisoprene rubber and maleic anhydride were prepared in the same manner as in Example 1, except that the amount of phenol derivatives added was changed to the amount shown in Table 2, and the reaction temperature was changed to 200°C. Made it react. The reaction rate of maleic anhydride and the acetone extract were measured in the same manner as in Example 1, and the results are shown in Table 2.

Table 2 shows that maleic anhydride is added to the liquid polyisoprene rubber at a very high reaction rate if the amount of the phenol derivative added is within the range specified in the present invention. Comparative Examples 1 and 2 The molecular weight was 3500 by polymerizing isoprene monomer using sec-butyllithium as a catalyst.
A liquid polyisoprene rubber having a cis-1,4 bond content of 80% was obtained. This liquid polyisoprene rubber 400
After gradually raising the temperature to 150° C. with stirring, 30 g of maleic anhydride was added thereto, and after raising the temperature to 190° C., a heating reaction was carried out for 6 hours. The reaction rate of maleic anhydride as a reaction product was 81.3%, which was significantly lower than when a phenol derivative was added. Also, the acetone extraction content is 3.5
It was a large percentage. In addition, in the above reaction, 2,2'-methylenebis(4-methyl-6-t-
When the reaction was carried out by adding 60 g of (butylphenol), which is more than the amount specified in the present invention, the reaction rate of maleic anhydride as a reaction product was as low as 82.8%. The acetone extraction content at this time was 0.2%.
It was hot. Example 7 The molecular weight was reduced by polymerizing isoprene monomer using sec-butyllithium as a catalyst.
71,000 to obtain a liquid polyisoprene rubber having a cis-1,4 bond content of 83%. To 300 g of this liquid polyisoprene rubber, 30 g of toluene and the phenol derivative 4,4'-butyldenbis(3-methyl-6-t-
After 4.5 g of butylphenol was added and dissolved, 15 g of maleic anhydride was added, the temperature was raised to 170° C. with stirring, and the mixture was reacted at that temperature for 16 hours.
When the reaction rate of maleic anhydride and the acetone extract were examined in the same manner as in Examples 1 to 3, the reaction rate was 99.1%, indicating that most of the added maleic anhydride had reacted. In addition, the acetone extract
It was found that the liquid polyisoprene rubber was hardly modified by this reaction other than modification with maleic anhydride. Comparative Example 3 Liquid polyisoprene rubber 300 used in Example 7
30 g of toluene and 4.5 g of N-phenyl-N'-isopropyl-P-phenylenediamine were added to the mixture, and a reaction was carried out in the same manner as in Example 7. The acetone extractable content of the reaction product was 0.8%,
The reaction rate of maleic anhydride was as low as 80.3%.
During the reaction, the reaction system turned dark purple and its viscosity gradually increased, and stirring became difficult after the reaction time exceeded 10 hours.

Claims (1)

[Scope of Claims] 1. In producing a modified liquid polyisoprene rubber by reacting a liquid polyisoprene rubber with a molecular weight of 8,000 to 100,000 and a cis-1,4 bond content of 70% or more with maleic anhydride, a phenol derivative is used. 1. A method for producing a modified liquid polyisoprene rubber, which comprises carrying out the reaction in the presence of. 2 The phenol derivatives are 2,6-di-t-butyl-4-methylphenol, 2,2'-methylenebis(4-methyl-6-t-butylphenol), 4,
The method according to claim 1, wherein the 4'-thiobis(3-methyl-6-t-butylphenol) or 4,4'-butylidenebis(3-methyl-6-t-butylphenol) is used.