JPS621961B2 - - 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. Methods for reacting such solid rubber with maleic anhydride include a method in which the rubber is dissolved in a solvent and reacted in the solvent because a high molecular weight polymer is used, and as a special example, a method in which a high-power extruder is used. A method of mixing and reacting in the solid phase using a mixer is adopted. However, in any of these reactions, the reaction rate is not high, only several tens of percent at most, and requires a step to remove residual unreacted maleic anhydride, which significantly reduces productivity. This is extremely disadvantageous industrially. Such a low reaction rate is due to the properties of solid rubber, such as excellent fluidity, adhesiveness that shows an excellent balance between adhesive strength and cohesive force, and excellent compatibility with diene-based solid rubber. By adding maleic anhydride to liquid polyisoprene rubber, which is widely used as a reactive plasticizer, pressure-sensitive adhesive, adhesive, sealant, etc., in addition to the above-mentioned properties of liquid polyisoprene rubber, solid rubber can also be anhydrous. Currently, liquid polyisoprene rubber is being studied to improve the properties of maleic acid adducts, as well as to improve their compatibility with polar polymers and to diversify crosslinking methods using added maleic anhydride groups. Since it is highly fluid, it poses a major problem in industrial implementation. In view of the above-mentioned current situation, the present inventors have completed various studies on the reaction of adding maleic anhydride to liquid polyisoprene rubber at a high reaction rate, and as a result, have completed the present invention. According to the present invention, when producing a modified liquid polyisoprene rubber by adding maleic anhydride to liquid polyisoprene rubber, the liquid polyisoprene rubber has a molecular weight of 8,000 to 100,000 and a cis-
Use a liquid polyisoprene rubber having a 1,4 bond content of 70% or more and a water content of 0.5% or less, and 0.1 to 85% per 100 parts by weight of the liquid polyisoprene rubber.
By reacting part by weight of maleic anhydride at a temperature of 120 to 250°C, a modified liquid polyisoprene rubber can be obtained with a reaction rate so high that a step of removing unreacted 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 reaction of adding maleic anhydride to liquid polyisoprene rubber, the low viscosity of liquid polyisoprene rubber allows stirring and mixing in a simple tank reactor, and therefore a small amount can be mixed without using a solvent. This makes it possible to react at high polymer concentrations, and maleic anhydride is 80%
However, it was still necessary to remove unreacted maleic anhydride. However, in the present invention, by specifying the amount of cis-1,4 bonds, molecular weight and water content of liquid polyisoprene rubber, as well as the reaction temperature,
It has become possible to drive the reaction rate to such a level that unreacted residual maleic anhydride can be virtually ignored. As a result, the method of the present invention does not require the step of removing unreacted maleic anhydride, making it extremely advantageous industrially. Furthermore, as mentioned above, the method of the present invention requires almost no use of solvent, and is therefore extremely useful industrially. Furthermore, although the conventional technique of adding maleic anhydride to low molecular weight polybutadiene is widely known, the reaction causes significant thickening or gelation, and the low molecular weight polybutadiene that can be used in the reaction is limited to extremely low molecular weight ones. However, in this respect, the method of the present invention uses liquid polyisoprene rubber without causing significant thickening or gelation. It has the advantage of being able to easily react even substances with relatively high molecular weights. The liquid polyisoprene rubber used in the present invention has a molecular weight of 8,000 to 100,000, a cis-1,4 bond content of 70% or more, and a water content of . 5% or less. 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 a crosslinked product is used as a crosslinking agent. , which is not desirable. From this point of view, those having 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 intrinsic viscosity ([η]) at 30°C in toluene. [η]=1.21×10 ^-4 MV ^{0.77 Also} , the liquid polyisoprene used in the present invention,
It is necessary that the amount of cis-1,4 bonds is 70% or more. Liquid polyisoprene with an increased number of 3,4 bonds and an amount of cis-1,4 bonds that is lower than the above range is likely to undergo crosslinking when heated, resulting in significant thickening or gelation during the reaction of adding 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, its compatibility decreases.
When used as a vulcanizate, it causes a significant decrease in physical properties,
Not desirable. 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. In addition, the water contained in liquid polyisoprene rubber,
That is, the water content needs to be 0.5% or less. If the water content exceeds 0.5%, maleic anhydride and water will react, maleic anhydride will turn into maleic acid, and the addition rate to liquid polyisoprene rubber will drop significantly. From this perspective, the water content is
More preferably, it is 0.1% or less. In the present invention, it is necessary that the liquid polyisoprene rubber having the above-mentioned specific structure has a limited water content, but the reaction temperature in the reaction with maleic anhydride may be 120 to 250 °C. This is an indispensable condition. If the reaction temperature is too low, the reaction will be slow and a significantly long reaction time will be required, while if it is too high, side reactions such as decomposition of the liquid polyisoprene rubber will occur, which is not preferred. From this point of view, the reaction temperature is more preferably in the range of 150 to 200°C. Although the reaction time is determined by the reaction temperature and cannot be determined unconditionally, it is preferably 30 minutes to 24 hours, preferably 1 to 12 hours. Although it is preferable not to use a solvent during the reaction, a solvent can be used in an amount that does not lower the concentration of the liquid polyisoprene rubber too much. As the solvent used here, aliphatic, alicyclic, or aromatic hydrocarbons are preferably used, and those with 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. It will be done. In the present invention, the amount of maleic anhydride added to the liquid polyisoprene rubber is 0.1 to 85 parts by weight, preferably 0.1 to 85 parts by weight per 100 parts by weight of the liquid polyisoprene rubber.
It is 0.5 to 50 parts by weight. If the added maleic anhydride is less than the above range, there will be almost no improvement effect on unvulcanized strength (green strength) or vulcanized adhesive strength when mixed with high molecular weight rubber, and when used alone, When made into a crosslinked product, the crosslinking density is extremely low and it cannot be put to practical use. Furthermore, if the amount of maleic anhydride exceeds the above range, the viscosity of the reaction system will increase significantly, making it difficult to manufacture, and furthermore, when mixed with other high molecular weight rubbers, dispersion will be poor and the product cannot be used. occurs. The added maleic anhydride group is hydrolyzed with water to form maleic acid groups, reacted with alcohols to form monoesters or diesters, and further reacted with ammonia or amines to form ammonium salts, amides, It is also possible to imidize or introduce a hydroxyl group by reacting with an epoxy compound. 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 can be 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 By polymerizing isoprene monomer using sec-butyllithium in the pressure-resistant reactor of 1,
A liquid polyisoprene rubber having a molecular weight of 35,000 and a cis-1,4 bond content of 80% was obtained. This liquid polyisoprene rubber was washed with water, dried, and its water content was measured using a Karl Fischer water titration apparatus, and found to be 0.08%. Add 4 g of 2.6-di-t-butyl-4-methylphenol to 40 g of this liquid polyisoprene rubber, gradually raise the temperature with gentle stirring, and when the temperature reaches 150°C, add 20 g of maleic anhydride. The temperature was raised to a predetermined reaction temperature shown in Table 1, and the reaction was carried out for a predetermined time. After the reaction was completed, unreacted maleic anhydride was extracted from a portion of the product using acetone, and the amount of unreacted maleic anhydride was determined by titrating with an aqueous caustic soda solution, and each reaction rate was calculated. . The results are shown in Table 1. Comparative Example 1 A liquid polyisoprene rubber having a molecular weight of 35,000 and a cis-1,4 bond content of 80% was obtained in the same manner as in Examples 1 to 3. After washing and drying this liquid polyisoprene rubber, its water content was examined and found to be 1.05%. This liquid polyisoprene rubber was reacted with maleic anhydride at 180° C. for 8 hours in the same manner as in Examples 1 to 3. The reaction rate of the product maleic anhydride is
It was 82.4%.

[Table] From Table 1, it can be seen that when the water content of the liquid polyisoprene rubber is 0.08%, the reaction rate is 98% or more, and only 2% or less of unreacted maleic anhydride remains. On the other hand, it can be seen that when the water content is 1.05%, a large amount of unreacted maleic anhydride remains. Examples 4 and 5 Liquid polyisoprene rubber with a molecular weight of 18,000, a cis-1,4 bond content of 80%, and a water content of 0.13%, obtained by polymerization using sec-butyllithium, was , 4 g of 6-di-t-butyl-4-methylphenol was added, and Example 1~
40 g of maleic anhydride was reacted in the same manner as in Example 3 under the reaction conditions shown in Table 2. The reaction rate of maleic anhydride was determined in the same manner as in Examples 1 to 3, and the second
Shown in the table. Note that the acetone extractable content of the product obtained in Example 4 was 0.4%. Comparative Examples 2 and 3 The reaction temperature was within the temperature range specified in the present invention.
Liquid polyisoprene rubber was reacted with maleic anhydride under the same reaction conditions as in Examples 4 and 5, except that the reaction times were changed to 100°C and 270°C (see Table 2). The reaction rate of maleic anhydride was measured and the results are shown in Table 2. In addition, the product obtained in Comparative Example 3, in which the reaction temperature was 270°C and the reaction time was 6 hours, had a bad odor probably due to significant deterioration.
When the acetone extractable content was measured, the extractable content was 4.5%.

[Table] As can be seen from the above, when the reaction temperature is too low, the reaction rate is low, and conversely, when the reaction temperature is too high, the liquid polyisoprene or modified liquid polyisoprene rubber undergoes reactions other than the addition of maleic anhydride. On the other hand, when the reaction is carried out within the temperature specified in the present invention, unnecessary side reactions are unlikely to occur and modified liquid polyisoprene can be obtained at a high reaction rate. Comparative Example 4 By adding diethyl ether to the polymerization of isoprene using sec-butyllithium, a liquid polyester having a molecular weight of 37,000, a cis-1,4 bond content of 38%, and a water content of 0.09% was produced. Isoprene rubber was obtained. The liquid polyisoprene rubber was reacted with maleic anhydride in the same manner as in Example 3 except that this liquid polyisoprene rubber was used. However, as heating continued, the viscosity of the reaction system gradually increased, and eventually stirring became impossible. The reaction product after cooling was gelatinized and contained 58% benzene insoluble matter. Example 6 The molecular weight obtained by polymerizing using sec-butyllithium in the pressure-resistant reactor of 1 was 71000.
Then, 300 g of liquid polyisoprene rubber with a cis-1,4 bond content of 83% and a water content of 0.21%, 30 g of toluene, and 3 g of 2,6-di-t-butyl-4-methylphenol were added and dissolved with stirring. , the temperature
When the temperature was raised to 150°C, maleic anhydride was added, the temperature was further raised to 170°C, and the reaction was carried out for 16 hours. The reaction rate of product maleic anhydride is 98.9%
It was hot.

Claims (1)

[Claims] 1. When producing modified liquid polyisoprene rubber by adding maleic anhydride to liquid polyisoprene rubber, the liquid polyisoprene rubber has a molecular weight of 8000 to 100000 and a cis-1,4 bond amount of 70.
% or more and whose water content is 0.5% or less, and reacting 0.1 to 85 parts by weight of maleic anhydride per 100 parts by weight of the liquid polyisoprene rubber at a temperature of 120 to 250°C. Characteristic method for producing modified liquid polyisoprene rubber.