JPH0442402B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a modified rubber composition with excellent green strength and physical properties after vulcanization. Conventionally, in order to obtain rubber compositions with improved green strength and adhesiveness after vulcanization, rubbers into which polar groups such as carboxyl groups have been introduced, such as rubbers to which maleic anhydride or glyoxal have been added, have been used as rubbers. known to be used. However, these rubbers have the disadvantage that their strength properties as a vulcanizate are insufficient because side reactions such as gelation of the rubber and reduction in molecular weight are likely to occur during the modification reaction. Therefore, the present inventor conducted various studies in order to develop a modified rubber composition that does not have such drawbacks, and found that
A composition obtained by blending carbon black with a modified rubber obtained by reacting a rubber having unsaturated carbon bonds with an organic compound having a carboxyl group and an aldehyde group in the presence of an acid catalyst has excellent green strength and a vulcanized product thereof. The present invention was achieved based on the discovery that the strength characteristics and rebound resilience of the material are significantly superior. Rubbers having unsaturated carbon bonds (hereinafter sometimes referred to as unsaturated rubbers or rubbers) used for the preparation of the modified rubber in the present invention include butadiene, isobrene, piperylene, 2,3-dimethylbutadiene, and chloroprene. Ring-opening of homopolymer rubbers of conjugated dienes, copolymer rubbers of two or more of these conjugated dienes, copolymer rubbers of these conjugated dienes and other monomers, and cycloolefins such as cyclopentene and norbornene. Typical rubbers having unsaturated carbon bonds include polymer rubbers, polymers of dienes such as ethylidene norbornene and 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. Union rubber, butadiene-piperylene copolymer rubber, butadiene-propylene alternating copolymer rubber, polypentenamer, ethylene-propylene-diene copolymer rubber, butyl rubber, butadiene-acrylonitrile copolymer rubber, butadiene-isoprene-acrylonitrile copolymer rubber, polychloroprene rubber, styrene-butadiene-styrene block copolymer rubber, styrene-isoprene-styrene block copolymer rubber, and the like. Among these, the reaction rate is generally high when isoprene homopolymer rubber or copolymer rubber, piperylene homopolymer rubber or copolymer rubber, and ethylene-propylene-diene copolymer rubber are used. The organic compound having a carboxyl group and an aldehyde group used in the present invention is one having at least one of each group, and includes a chain aliphatic compound having up to about 20 carbon atoms, a benzene ring, a naphthalene ring, It is selected from compounds having aromatic rings such as pyridine rings and furan rings, and alicyclic compounds such as cyclopentane rings, cyclopentene rings, and cyclohexane rings. These compounds can contain oxygen atoms, sulfur atoms, nitrogen atoms, or multiple bonds as appropriate in their molecular chains, and hydrogen atoms in the molecules can be replaced with halogen atoms as long as they do not adversely affect the reaction. , alkyl group,
Alkoxy group, acyl group, hydroxyl group, nitrile group,
It can also be replaced with any substituent such as an amino group. More specifically, examples of aliphatic compounds having a carboxyl group and an aldehyde group include glyoxylic acid, formyl acetic acid, 2-formylacrylic acid, 6-formylacrylic acid,
- formylhexanoic acid, 8-formyloctanoic acid, formylmethoxyacetic acid, 2-formylbutyric acid,
Compounds with aromatic rings such as 3-(carboxymethoxy)propylaldehyde include 2-,3
- or 4-carboxybenzaldehyde, 2-formyl-5-acetyl-benzoic acid, 2-, 3- or 4-formylphenylacetic acid, 2-formyl-5
-Hydroxyphenylacetic acid, 3-(2-formylphenyl)propionic acid, 2-formylcinnamic acid,
1,8-naphthaldehydic acid, 2-, 3- or 4
-Formylphenoxyacetic acid, 2-formyl-4-
Methylphenoxyacetic acid, 2-(2-formylphenoxy)propionic acid, 3-(2-formylphenoxy)propionic acid, 2-formyl-1-phenoxyisovaleric acid, 6-(2-,3 - or 4-formylphenoxy)hexanoic acid, (2-
formylphenyl)methoxyacetic acid, 2-, 3- or 4-formylphenylthioacetic acid, [(1-formyl-2-naphthyl)oxy]acetic acid, [(5-formyl-2-furyl)thio]acetic acid, (8- Formyl-
2-oxo-2H-1-benzopyran-7-yl-oxy)acetic acid, 2-, 3- or 4-carboxyphenoxyacetaldehyde, 2-(formylmethoxy)phenoxyacetic acid, and alicyclic compounds such as 2 -Formylcyclopentanecarboxylic acid, 4-formyl-2-cyclopentenecarboxylic acid, 2-formylcyclohexanecarboxylic acid, and the like. Among these compounds, those that have a structure in which the carboxyl group and aldehyde group of the compound can easily approach each other sterically or thermodynamically within the molecule through an acid catalyst, especially those that have an aromatic ring. It is most preferable that the carboxyl group or the atomic group containing this group and the aldehyde group or the atomic group containing this group are located at adjacent positions on the ring (ortho position in the benzene ring) because the reaction rate is high. In addition, organic compounds having a carboxyl group and an aldehyde group that are nonpolar or have a structure containing a large amount of relatively weakly polar hydrocarbon moieties or have a low melting point are suitable for reaction operations because they have high solubility in hydrocarbon solvents. . The amount of the organic compound having a carboxyl group and an aldehyde group to be used is not particularly limited, but is usually 0.01 to 20 parts by weight, preferably 0.1 to 5 parts by weight, per 100 parts by weight of the unsaturated rubber. The acid catalysts used in the preparation of the modified rubber in the present invention include sulfuric acid, nitric acid, chlorosulfonic acid,
It is selected from protic acids such as p-toluenesulfonic acid and hydrogen halides as well as commonly known Lewis acids. Typical examples of Lewis acids 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, Te, Ta, W,
Elements such as Hg, Bi, U or PO, SeO, SO,
Examples include halides of oxygen-element bonds such as SO ₂ and VO, organic halides, or complexes thereof, and those that form coordinate bonds with organic compounds having carboxyl groups and aldehyde groups are preferable. The color of the coordination bond is orange (absorption wavelength
480nm) or deeper is particularly desirable.
More specifically, _BF3 , ( _CH3 ) _2BF , _BCl3 ,
_AlCl3 , _AlBr3 , ( _C2H5 ) _AlCl2 , _POCl3 , _{TiCl4 ,
VCl4} , _MoCl6 , _SnCl4 , ( _CH3 ) _SnCl3 , _SbCl5 ,
Examples include TeCl ₄ , TeBr ₄ and WCl ₆ . Among these, SnCl ₄ , BCl ₃ , WCl ₆ , SbCl ₅ and the like are preferable because they have a high reaction rate and cause few side reactions such as gelation of rubber. Note that it is of course possible to use two or more types of protonic acids or Lewis acids, or to use a protonic acid and a Lewis acid in combination. The amount of acid catalyst used is not particularly limited, but is usually 0.01 to 5 mol per mol of organic compound having a carboxyl group and an aldehyde group.
Preferably it is 0.05 to 2 mol. The reaction for preparing the modified rubber 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. Suitable materials are those that are inert to the rubber and dissolve the rubber. Solvents that have a certain degree of solubility for organic compounds having carboxyl groups and aldehyde groups and acid catalysts are particularly suitable from the viewpoint of reaction rate, but are not necessarily limited thereto. Note that the organic compound having a carboxyl group and an aldehyde group and the acid catalyst may be added to the reaction system separately, or they may be mixed in advance (in this case, a chemical change may occur) before adding them to the reaction system. May be added to.
Further, the acid catalyst may be added in its entirety at the beginning of the reaction, or may be added in portions or continuously during the reaction. When carrying out a reaction using a Lewis acid as a catalyst, the reaction system must be maintained in an anhydrous state or under a limited amount of water in order to maintain the activity of the catalyst and to prevent side reactions such as excessive gelation and cyclization of the rubber. It is preferable. The presence of oxygen is also generally undesirable. The reaction temperature is not particularly limited and is usually between -20°C and 200°C.
℃, preferably in the range of 0 to 100℃. The reaction time is also set appropriately between 10 seconds and 50 hours. When the reaction is carried out in a solvent, for example, by adding a large amount of alcohol or hot water, the reaction can be stopped and the rubber can be coagulated. Next, the remaining acid catalyst and the like are removed by washing if necessary, and then the rubber is dried to obtain a modified rubber. The type of carbon black blended into the modified rubber obtained in this way is not particularly limited, but it is preferable to have an average particle size of 10 mμ to 500 mμ, and the commonly used abbreviations are EPC, MPC, HPC, CC, etc. Channel black, SAF, ISAF, HAF, MAF,
FEF, HMF, SRF, SPF, GPF, APF, FF,
It is appropriately selected from furnace blacks such as CF, thermal blacks such as FT and MT, and acetylene blacks. The amount of carbon black used is usually 1 to 200 parts per 100 parts by weight of modified rubber, depending on the application.
parts by weight, preferably from 10 to 12 parts by weight. The composition of the present invention may optionally contain conventional rubber compounds such as vulcanizing agents, vulcanization accelerators, vulcanization aids, softeners, tackifiers, fillers, reinforcing agents other than carbon black, and anti-aging agents. may contain additives for use. 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 Hydrogen resins, coumaron resins, phenol-terpene resins, etc. are used as fillers, calcium carbonate, clay, talc, etc. are used as fillers, silicic acid and its salts are used as reinforcing agents other than carbon black, and as anti-aging agents. Examples include amine type and phenol type. 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 composition of the present invention can also contain other rubbers such as natural rubber, styrene-butadiene copolymer rubber, polybutadiene rubber, and unmodified polyisoprene rubber in any proportion as desired. The method of mixing the components constituting the composition of the present invention is not particularly limited, and various rubber kneading machines are usually used. In particular, carbon black and various process oils are mixed in the raw rubber manufacturing process or modification process. They can also be mixed with rubber to make a carbon masterbatch and an oil masterbatch, respectively. The modified rubber composition of the present invention has excellent dynamic properties such as green strength in an unvulcanized state, tear strength after vulcanization, fatigue resistance, and rebound resilience, and is therefore suitable for use in passenger car tires, trucks, and buses. large tire carcass,
Toledo, sidewalls, bead fillers, inner liners, various anti-vibration rubbers, industrial belts,
Suitable for uses such as hoses. Next, the present invention will be specifically explained using examples.
In addition, the analysis method of the modified rubber, the preparation method of the unvulcanized compound and vulcanizate of the modified rubber, and the physical property testing method in each example are as follows. [Amount of organic compound having a carboxyl group and an aldehyde group (hereinafter sometimes referred to as organic compound) introduced into rubber] Added to rubber molecules using gel permeation chromatography equipped with an ultraviolet absorption spectrometer The amount was determined using the absorption of the aromatic ring of the organic compound at a wavelength of 275 nm. [Amount of carboxyl group introduced into rubber] After purifying and removing the low molecular weight components in the rubber, it was measured by the neutralization titration method. [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 (parts by weight) Rubber 100 HAF carbon 50 Aromatic oil 5 Zinc oxide 5 Stearic acid 2 Sulfur 2.5 N-oxydiethylene-2-benzothiazylsulfenamide (vulcanization accelerator) 0.8 N-isopropyl-N- Phenyl-p-phenylenediamine 1.0 [Wallace plasticity] According to Wallace Rapid Plastometer
Value at 100℃. [Green strength] A 2 mm thick unvulcanized rubber sheet is made by press-molding the unvulcanized rubber compound at 100℃ for 5 minutes.
Punch out a dumbbell-shaped JIS No. 3 test piece, 25℃,
The value of tensile stress at 500% elongation when performing a tensile test at a tensile speed of 500 mm/min. [Vulcanization speed] By oscillating disk rheometer
Time required for torque to reach 95% of maximum torque (T ₉₅ ) measured at 145°C. [Tensile test] The unvulcanized rubber compound was press-vulcanized at 145°C for a predetermined period of time to form a 2 mm thick sheet, and a dumbbell-shaped No. 3 test piece specified in JIS-K6301 was punched out.
The tensile speed was mm/min. [Tear strength] Three rectangular test specimens with a width of 15 mm and a length of 100 mm were punched out from a 2 mm thick vulcanized sheet in the grain direction and in the direction perpendicular to the grain. A cut of 6 mm was made perpendicularly to the side edge using a safety razor blade, and the test was performed at 25℃ at a tensile speed of 500 mm/min, and the average value of 6 pieces, 3 pieces each in the grain direction and 3 perpendicular to the grains, was measured. It was displayed. [Rebound modulus] Measured at 25°C using a Danlopt tripometer. Example 1 Polyisoprene rubber (98% cis-1.4 bonds) 160g
was dissolved in dehydrated toluene from step 3 and heated in a sealed glass container (separable flask) under a nitrogen atmosphere for 25 minutes.
The organic compounds listed in Table 1 were added while stirring at °C. Next, add the amount of SnCl ₄ listed in Table 1.
The solution was diluted with 40 times more dehydrated benzene and gradually added dropwise, and the color of the solution was observed. After further stirring for the reaction time listed in Table 1, 500 ml of methyl alcohol was poured into the mixture (it is assumed that this stopped the addition reaction). The obtained semi-solidified rubber solution was poured into methyl alcohol from Step 3 to completely solidify the rubber and the solidified material was washed in small pieces. Then about 2g of anti-aging agent (2,
The modified polyisoprene shown in Table 1 was obtained by immersing the coagulated pieces in methyl alcohol 3 containing (6-di-butyl-4-methylphenol), washing them, and drying them in a vacuum dryer overnight. Rubber samples A, B, C, D, E, F, and G were obtained.

[Table] * Comparative sample Next, the physical properties of the unvulcanized compound and vulcanized product of the samples shown in Table 1 were measured. The results are shown in Table 2. Table 2 shows that samples B, C, and D of the present invention are particularly excellent in green strength, tear strength, and rebound modulus.

[Table] Example 2 The reactions shown in Table 4 were carried out in the same manner as in Example 1, except that the organic compounds and acid catalysts used in Example 1 were replaced with those shown in Table 3. Modified polyisoprene rubber samples H to Q were obtained.

[Table] Next, the physical properties of each of the above samples were tested in the same manner as in Example 1, and the results shown in Table 4 were obtained.
From the same table, it can be seen that in all cases, the green strength and tear strength are especially excellent.

[Table] Example 3 An experiment similar to Example 1 was conducted using the rubber, organic compound, and acid catalyst shown in Table 5, except that they were reacted for the indicated time. As a result, modified rubber sample N shown in Table 5 was carried out. , O, P were obtained.

[Table] *Prepared using a lithium-based catalyst Next, physical property tests of each of the above samples and their corresponding unmodified rubbers were conducted in the same manner as in Example 1, and the results shown in Table 6 were obtained. However, the formulation and vulcanization temperature were partially changed as shown below. Sample N and corresponding unmodified rubber: Zinc oxide 3 (parts by weight) Sulfur 1.5 Vulcanization accelerator 1.1 Sample O and corresponding unmodified rubber: Zinc oxide 3 Sulfur 1.7 Vulcanization accelerator 1.4 Vulcanization temperature
160℃ Sample P and corresponding unmodified rubber: Zinc oxide 3 Sulfur 1.14 Vulcanization accelerator 1.8 Vulcanization temperature 160℃

[Table] The table shows that the modified rubbers obtained according to the present invention have higher green strength, 300% tensile stress, tensile strength, and tear strength than the corresponding unmodified rubbers. Example 4 The physical properties of a rubber composition prepared according to the formulation shown in Table 7 using Sample D in Example 1 and unmodified polyisoprene rubber were conducted in the same manner as in Example 1. The results are shown in Table 7.

[Table] As is clear from Table 7, the same results as in Example 1 were obtained even when the amount of carbon black was varied. Example 5 Glyoxylic acid hydrate (OHC-COOH・H ₂ O)
After drying and dehydrating 1.1 g at 50° C. for 10 hours under reduced pressure (below 1 mmHg), it was dissolved in 100 ml of benzene and a small amount of insoluble portion was removed. Polyisoprene rubber (98% cis 1.4 bonds) 160g
was dissolved in the dehydrated n-hexane from Step 3, and the entire amount of the above glyoxylic acid solution was added while stirring at 25° C. in a nitrogen atmosphere in a sealed glass container (separable flask). Next, 1.5 g of SnCl ₄ was gradually added dropwise as a benzene solution (the solution turned yellow), and after continued stirring for another 2 hours, 50 ml of methyl alcohol was poured in (it is assumed that this stopped the addition reaction. ). The obtained rubber solution was poured into acetone in Step 3 to completely coagulate the rubber, and the coagulated material was washed as small pieces. Next, the coagulated pieces were immersed in methyl alcohol 3 containing about 2 g of an anti-aging agent (2,6-di-tarsiallybutyl-4-methylphenol), washed, and dried overnight in a vacuum dryer. A modified polyisoprene rubber sample Q was obtained. The infrared absorption spectrum of the purified test Q was taken, and the absorbance at 1706 cm ^-1 (C=O) was determined to be 1660 cm ^-1 (C=
By comparing with the absorbance of C), it was found that the amount of carboxyl group introduced was 0.0013 mol/100 g rubber. Next, the physical properties of the unvulcanized compound and the vulcanized product were measured. The results are shown in Table 8.

【table】

Claims (1)

[Claims] 1. In the presence of an acid catalyst, a chain aliphatic compound having up to 20 carbon atoms, a compound having an aromatic ring, and an alicyclic compound having at least one carboxyl group and an aldehyde group is added to a rubber having an unsaturated carbon bond. A modified rubber composition characterized by blending carbon black into a modified rubber obtained by reacting a selected organic compound.