JPH0562123B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for modifying rubber having unsaturated carbon bonds. Traditionally, in order to improve the unvulcanized physical properties and vulcanized physical properties of rubber such as green strength and adhesion, polar groups such as carboxyl have been introduced into rubber, such as maleic anhydride and glyoxal, etc., to be added to rubber. It has been known. However, many of these methods tend to cause side reactions such as gelation of the rubber and molecular weight reduction due to the addition reaction, resulting in a decrease in the strength properties of the rubber vulcanizate, and the reaction rate and It has the disadvantage of low reaction efficiency. Therefore, the inventor of the present invention has conducted various studies in order to develop a rubber modification method that does not have such drawbacks.
The inventors have discovered that the desired object can be achieved by reacting a rubber having unsaturated carbon bonds with glyoxylic anhydride in the presence of a Lewis acid, and have arrived at the present invention. Rubbers having unsaturated carbon bonds (hereinafter sometimes referred to as unsaturated rubbers or rubbers) used in the present invention include homopolymer rubbers of conjugated dienes such as butadiene, isoprene, piperylene, 2,3-dimethylbutadiene, and chloroprene. , copolymer rubbers of two or more of these conjugated dienes or copolymer rubbers of these conjugated dienes and other monomers, ring-opening polymer rubbers of cycloolefins such as cyclopentene and norbornene, ethylidene norbornene and rubbers having ordinary unsaturated carbon bonds, such as polymer rubbers of dienes such as cyclopentadiene, and polyolefin rubbers such as copolymers of dienes and olefins. Typical examples include natural rubber, guayule rubber, polyisoprene rubber, polybutadiene rubber, styrene-butadiene copolymer rubber, butadiene-isoprene copolymer rubber, isoprene-styrene copolymer rubber, and butadiene-isoprene-styrene copolymer rubber. Rubber, butadiene-piperylene copolymer rubber, butadiene-propylene alternating copolymer rubber, polypentenamer, ethylene-propylene-diene copolymer rubber, butyl rubber, butadiene-acrylonitrile copolymer rubber, butadiene-isoprene
Examples include acrylonitrile copolymer rubber, polychloroprene rubber, styrene-butadiene-styrene block copolymer rubber, and styrene-isoprene-styrene block copolymer rubber. In the present invention, the glyoxylic anhydride used has the chemical formula: It is a compound represented by the formula, and can be synthesized by oxo-forming acetic anhydride with selenium dioxide, etc., decomposing maleic anhydride by ozonation, etc.
The amount of glyoxylic anhydride used is not limited in some cases, but is usually 0.0001 to 20 glyoxylic anhydride per 100 parts by weight of unsaturated rubber.
Parts by weight, preferably 0.01 to 5 parts by weight. Generally known Lewis acids can be used in the present invention. Typical examples are metal or metalloid halides, such as Be,
B, Al, Si, P, S, Ti, V, Fe, Zn, Ga,
Ge, As, Se, Zr, Nb, Mo, Cd, Sn, Sb,
Elements such as Te, Ta, W, Hg, Bi, U or PO,
These include halides of oxygen-element bonds such as SeO, SO, SO ₂ and VO, organic halides, and complexes thereof. More specifically, BF ₃ ,
_BF3O ( _C2H5 ) ₂ , ( _CH3 ) _2BF , _BCl3 , _{AlCl3 ,
AlBr3} , ( _C2H5 ) _AlCl2 , _PCOl3 , _TaCl4 , _{VCl4 ,
MoCl6} , _SnCl4 , ( _CH3 ) _SnCl3 , _SbCl5 , _TeCl4 ,
Examples include TeBr ₄ , FeCl ₃ and WCl ₆ . Among these, SnCl ₄ , BF ₃ O(C ₂ H ₅ ) ₂ , TiCl ₄ and the like are particularly suitable because they have a high reaction rate and cause few side reactions such as gelation of rubber. The amount of Lewis acid used is not particularly limited, but is usually 0.01 to 5 mol, preferably 0.05 to 2 mol, per 1 mol of cryoxylic anhydride. The reaction in the present invention is usually carried out in the presence of a suitable solvent or in the absence of a solvent in a rubber kneader. Industrially, it is advantageous to carry out the reaction in the rubber cement after the polymerization has ended. When using a solvent, any solvent can be used, such as aromatic solvents such as benzene and toluene, paraffinic solvents such as butane and hexane, and halogenated hydrocarbon solvents such as chloroform and dichloroethane. Those that are active and dissolve rubber are suitable. Glyoxylic anhydride may be added to the reaction system in its entirety at the beginning, or may be added in portions or continuously during the reaction. Further, the Lewis acid may be added simultaneously with glyoxylic anhydride or separately, or may be added after mixing both in advance. When carrying out the reaction, it is necessary to maintain the reaction system in an anhydrous state or under a limited amount of water. The reaction temperature is not particularly limited and is usually -20
℃~100℃, preferably -10℃~60℃. The reaction time is also not particularly limited, and is 10 seconds to 10 seconds.
The time is set appropriately. When the reaction in the present invention is carried out in a solvent, the reaction can be stopped and the rubber can be coagulated by pouring the reaction solution into a large amount of alcohol or hot water while stirring. Then,
After removing residues in the rubber by washing if necessary, the rubber is dried to obtain a modified rubber. The rubber thus obtained is mixed with conventional rubber compounding agents such as reinforcing agents, fillers, vulcanizing agents, vulcanization accelerators, vulcanization aids, softeners, tackifiers and anti-aging agents. The resulting unvulcanized formulation exhibits excellent green strength, and the vulcanizate has excellent strength properties such as tear strength. In addition, a rubber in which part or all of the ester groups in the modified rubber are changed to carboxyl groups by the above-described method has features such as an even better green strength of an unvulcanized compound. The type of reinforcing agent added to the modified rubber is not particularly limited, but the commonly used abbreviations are EPC, MPC,
Channel black for HPC, CC, etc., SAF,
ISAF, HAF, MAF, FEF, HMF, SRF,
Furnace blacks such as SPF, GPF, APF, FF, CF, thermal blacks such as FT, MT, and acetylene blacks with average particle diameters of 10 mμ to 500 mμ
Carbon black, anhydrous silicic acid produced by a dry process, hydrated silicic acid produced by a wet process, synthetic silicates, and other silica-based reinforcing agents having an average particle size of 10 to 100 mμ are preferred. Further, as the filler, calcium carbonate, clay, talc, etc. are used as appropriate. When blending reinforcing agents and fillers, the blending amount is usually selected from the range of 1 to 200 parts by weight, preferably 10 to 120 parts by weight, per 100 parts by weight of the modified rubber, depending on the purpose. Typical vulcanizing agents include sulfur and sulfur donors such as thiuram and thiazole.
Other peroxides, polyamines, metal oxides,
Urethane vulcanizing agents, resin vulcanizing agents, and the like can also be used as desired. Vulcanization accelerators include sulfenamide, thiuram, thiazole, guanidine, mercaptotriazine, aldehyde-amine, etc., and vulcanization aids include carboxylic acids such as stearic acid and oleic acid, and zinc stearate. , metal compounds such as zinc oxide, magnesium oxide, calcium hydroxide, and lead carbonate; softening agents include paraffin-based, naphthenic-based, and aromatic-based process oils; tackifiers include rosin-based and carbonized petroleum Examples of anti-aging agents include hydrogen resins, coumaron resins, and phenol-terpene resins, and examples of anti-aging agents include amines and phenols. Incidentally, the above-mentioned vulcanization accelerator and vulcanization aid are mainly used in the case of vulcanization using sulfur or a sulfur donor. The modified rubber obtained by the method of the present invention may be blended with other rubbers such as natural rubber, styrene-butadiene copolymer rubber, polyptadiene rubber, and unmodified polyisoprene rubber in any proportion as desired. You can also do it. The method of mixing each component is not particularly limited, and usually various rubber kneading machines are used. In particular, carbon black and various process oils are mixed with rubber in the manufacturing process or modification process of raw rubber, respectively. It can also be used as a batch or oil master batch. The modified rubber compound obtained by the method of the present invention has excellent green strength in an unvulcanized state, fatigue resistance after vulcanization, rebound resilience, etc., and is therefore suitable for use in passenger car tires, trucks, and large tires for buses. carcass,
Toledo, sidewalls, bead fillers, inner liners, various anti-vibration rubbers, industrial belts,
Suitable for applications such as hoses. It is also possible to use the modified rubber produced by the method of the present invention in the form of latex for ordinary latex applications. Next, the present invention will be specifically explained using examples.
The method for analyzing the modified rubber, the method for preparing the unvulcanized compound and vulcanizate of the modified rubber, and the method for testing their physical properties in each example are as follows. [Amount of glyoxylic anhydride introduced into the rubber] After purifying and removing the low molecular components in the rubber, it was measured by neutralization titration method (back titration method with sodium methylate/hydrochloric acid). [Preparation of unvulcanized rubber compound] The modified rubber is kneaded and mixed in a small Banbury mixer with various compounding ingredients in the following compounding recipe excluding sulfur and vulcanization accelerator, and the resulting mixture is mixed with sulfur and vulcanized. The rubber green compound was prepared by adding the accelerator and kneading on a small roll. Formula rubber 100 (parts by weight) HAF carbon 50 Aromatic oil 5 Zinc oxide 5 Stearic acid 2 Sulfur Yellow 2.5 N-oxydiethylene-2-benzothiazylsulfenamide (vulcanization accelerator) 0.8 N-isopropyl- N'-Phenyl-p-phenylenediamine 1.0 [Wallace Plasticity] Measured on rubber or unvulcanized rubber blends at 100°C using a Wallace Rabbit Plastometer. [Green strength] The unvulcanized rubber compound was press-molded at 100℃ for 5 minutes to form a 2 mm thick unvulcanized rubber sheet.
Punch out a dumbbell-shaped JIS No. 3 test piece, 25℃,
It is shown as the value of tensile stress at 500% elongation when a tensile test is performed at a tensile speed of 500 mm/min. [Vulcanization speed] By oscillating disk rheometer
It is expressed in time (T ₉₅ ) until the torque reaches 95% of the maximum torque measured at 145°C. [Tensile test] The unvulcanized rubber compound was press-vulcanized at 145℃ for a predetermined period of time to form a 2mm thick sheet, and a dumbbell-shaped No. 3 test piece specified in JIS-K6301 was punched out, and a
The tensile speed was mm/min. [Repulsion Resilience] Measured at 25°C using a Danlopt tripsomer. Example 1 Polyisoprene rubber (98% cis 1,4 bonds)
Dissolve 160 g in dehydrated benzene from step 4, add glyoxylic anhydride and Lewis acid as benzene solutions in the amounts listed in Table 1 at 25°C under a nitrogen atmosphere while stirring in a sealed glass container (separable flask), and stir. After reacting for 60 minutes, 100 ml of a water/acetone (1/1) mixture was poured (it is assumed that this stopped the addition reaction). Thereafter, the reaction solution was poured into methyl alcohol from Step 4 to completely coagulate the rubber, and the coagulated material was washed as small pieces. Then about 2g of anti-aging agent (2,6
Sample A shown in Table 1 was prepared by immersing the coagulated pieces in methyl alcohol 3 containing (di-tert-butyl-4-methylphenol), washing, and drying in a vacuum dryer overnight. ,B,
I got a C.

[Table] In all samples, the molecular weight hardly changed due to the addition reaction, and no gel was formed. Next, for Samples A, B, and C shown in Table 1, the unvulcanized compound and vulcanized product were measured. The results are shown in Table 2.

[Table] It can be seen that the samples of the present invention have improved green strength and high rebound modulus. Example 2 1 g of the rubber listed in Table 3 was dissolved in 30 ml of dehydrated n-hexane, and heated in an Erlenmeyer flask under a nitrogen atmosphere for 25 minutes.
℃ while stirring with a magnetic stirrer.
The listed amounts of glyoxylic anhydride and Lewis acid were added as a benzene solution and reacted for 30 minutes with stirring, then 5 ml of a water/acetone (1/1) mixture was poured in (this stopped the addition reaction). Presumed). The reaction was then poured into 200 ml of acetone to completely coagulate the rubber, and then immersed in methyl alcohol containing an anti-aging agent (2,6-di-tert-butyl-4-methylphenol) and washed. The samples D, E, and F shown in Table 3 were obtained by drying in a vacuum dryer for one day and night.

[Table] In all samples, the molecular weight hardly changed due to the addition reaction, and no gel was formed.

Claims (1)

[Claims] 1. A method for modifying rubber, which comprises reacting a rubber having unsaturated carbon bonds with glyoxylic anhydride in the presence of a Lewis acid.