Self-sealing rubber composition and self-sealing adhesive for tires, and preparation method therefor

Abstract

The present invention relates to a self-sealing rubber composition and self-sealing adhesive for tires, and a preparation method therefor. By means of excellent airtightness, flowability and self-adhesion capability of butyl rubber, rubber containing a diene structural unit and liquid polyisobutylene, a micro-crosslinking mode using a pyrrolinone-type crosslinking agent is used to enhance dimensional stability at high temperature, while keeping the flowability; and by means of the reinforcing and filling functions of carbon black and an inorganic filler and the tackifying effect of resin and by means of using the "like dissolves like" principle with the liquid polyisobutylene rubber, the self-sealing rubber composition is prepared by mixing. The positions outside airtight layers of tires corresponding to treads are coated with the prepared rubber composition having the self-sealing property, so as to form self-sealing layer structures; said self-sealing layer structures can ensure the rubber performance in environments of -45℃ to 120℃, and prevent the tires from leaking air when foreign matters below 6 mm puncturing the tires are removed; in addition, foam or other sound-absorption materials can be attached to the self-sealing layer structures to manufacture quiet tires or tires having both self-sealing and soundless functions.

Description

Self-sealing rubber composition for tires, self-sealing glue and preparation method thereof TECHNICAL FIELD

[0001] The present application relates to a self-sealing composition, in particular to a self-sealing rubber composition for tires, self-sealing glue and preparation method thereof. BACKGROUND

[0002] When the tire is running on the road, it may be punctured by a nail. After the nail pierces the tire air layer, the tire internal pressure will drop sharply, the vehicle will lose control and a traffic accident will occur. In view of the above situation, many tire factories in the market have developed self-sealing and self-repairing tires, that is, a layer of self-sealing glue is coated on the inner side of the tire air layer. After the nail pierces, the self-sealing layer in the tire can prevent the tire internal pressure from dropping, and can ensure the normal use of the tire after the nail is pierced or pulled out. The self-sealing glue needs to realize the tire sealing performance (the tire internal pressure drop is less than 10%) after the nail is pierced and pulled out in a very wide temperature range (-45~120℃), and the self-sealing glue should not flow or deform greatly in the tire running and static state, which does not affect the dynamic balance uniformity of the tire. The better the flowability of the self-sealing glue, the better the sealing performance, but the dimensional stability will be poor. Therefore, the sealing performance at high and low temperatures and the dimensional stability are the key points of the self-sealing glue formula design, and the selection of rubber and crosslinking system is crucial.

[0003] The self-sealing glue formula in the tire is mainly divided into hot melt glue system and rubber system in technology. The hot melt glue system has simple formula and process, and generally does not contain crosslinking system, so it is easy to flow at high temperature, thereby affecting the dynamic balance uniformity of the tire; in addition, the hot melt glue system generally adopts high temperature surface spraying method during coating, so that the coating thickness is uneven on the inner surface of the tire with a certain arc. The self-sealing glue of the rubber system generally contains a crosslinking system, but due to the difficulty in accurately controlling the crosslinking degree of the system during high temperature coating, the crosslinking degree is too high, which will make the sealing performance worse; the crosslinking degree is too low, which will make the high temperature dimensional stability worse, and it is difficult to balance the flowability and dimensional stability. SUMMARY

[0004] Therefore, in order to solve the problem, the present application discloses a novel self-sealing rubber composition for tires, self-sealing glue and preparation method thereof. The crosslinking degree of the self-sealing glue of the rubber system is controlled by using a pyrrolinone crosslinking agent, so as to adjust the self-sealing properties and high temperature dimensional stability.

[0005] It is to be noted that the self-sealing rubber composition disclosed in the present application is in a semi-flowing state of micro-crosslinking by using a special crosslinking agent. When the self-sealing rubber composition disclosed in the present application is applied to the inner wall of a tire or inlaid in the interior of a tire, it can quickly flow into the gap between a nail and the tread rubber after the tire is punctured by the nail to prevent the loss of internal air; when the nail is pulled out, part of the self-sealing rubber is wrapped around the nail and taken out together, and the other part continues to flow to block the hole, thereby achieving the sealing effect. The self-sealing rubber composition disclosed in the present application not only has good sealing effect at low temperature, but also has good size stability after the tire is driven at high speed for a long time, and has no influence on the dynamic balance uniformity of the tire.

[0006] In order to achieve the above-mentioned object, the present application adopts the following technical solutions:

[0007] The first technical object of the present application is to provide a self-sealing rubber composition for a tire, which is applied to the inner side of a tire or inlaid in the interior of a tire, and the composition at least comprises a halogenated butyl rubber, and a pyrrolinone crosslinking agent is used for crosslinking without using sulfur, zinc oxide and accelerators, and is combined with rubber comprising a diene structure unit, resin, reinforcing filler, filler and plasticizer;

[0008] The structure of the pyrrolinone crosslinking agent is as follows:

[0009] In the formula, R1, R2, R3 and R4 are the same or different, and represent a hydrogen atom, an alkyl group, an aralkyl group, an aryl group or a heterocyclic group; R3 and R4 are optionally connected together to form an alkylene group, and any two of R2, R3 and R4 are optionally connected together to form an alkylene group; each of these groups optionally has one or more substituents, and further, R1, R3 and R4 are hydrogen atoms, and R2 is a methyl group.

[0010] Alternatively, the structure of the pyrrolinone crosslinking agent is as follows:

[0011] In the formula, R5, R7 and R8 are the same or different, and represent a hydrogen atom, an amino group, an alkyl group, an aralkyl group, an aryl group or a heterocyclic group, and R6 represents an alkyl group, an aralkyl group, an aryl group or a heterocyclic group; further, R5, R6 and R8 are hydrogen atoms, and R7 is a methyl group.

[0012] It is to be noted that the pyrrolinone crosslinking agent selected in the present application is used as a vulcanizing agent, and can crosslink the halogenated butyl rubber through the dehalogenation reaction of the methylene group and the amino group. The type and amount of the crosslinking agent are particularly considered, and if the crosslinking degree of the self-sealing rubber is too high, the flowability of the rubber compound is insufficient, and the self-sealing effect cannot be achieved; and if the crosslinking degree is too low, the self-sealing rubber is prone to flow at high temperature and prone to cold flow at low temperature, which affects the dynamic balance uniformity of the tire.

[0013] Optionally, the rubber composition is mainly composed of the following components, in parts by weight:

[0014] halogenated butyl rubber 20-100 parts, diene structural unit-containing rubber 0-80 parts; reinforcing filler 0-60 parts; filler 0-60 parts; resin 1-60 parts; pyrrolinone crosslinking agent 0.1-20 parts; plasticizer 10-300 parts;

[0015] wherein the pyrrolinone crosslinking agent is crosslinked with the halogenated butyl rubber; and the pyrrolinone compound is one or more of a mixture of 3-methyl-5-pyrrolinone, 3-phenyl-5-pyrrolinone, 3-ethyl-5-pyrrolinone, 3-propyl-5-pyrrolinone, and 3-butyl-5-pyrrolinone.

[0016] Further, the main body rubber selected by the present application is halogenated butyl rubber, mainly because of its excellent air tightness and its adhesion and self-adhesion to the inner liner of the tire, and the halogenated butyl rubber can be selected to use different types of vulcanization system to control the crosslinking degree. The halogenated butyl rubber is one or a mixture of two or more of chlorinated butyl rubber and brominated butyl rubber, preferably brominated butyl rubber. The amount of halogenated butyl rubber is 30-80 parts, further preferably 40-60 parts.

[0017] Further, the base rubber selected by the present application also contains diene structural unit-containing rubber, which has a flexible molecular chain structure and can maintain good activity and flowability of the molecular chain at low temperature, realizing the low-temperature sealing property of the self-sealing glue. The glass transition temperature Tg of the diene structural unit-containing rubber is -20 to -120℃, preferably -30 to -110℃, and further preferably -40 to -110℃. The diene structural unit-containing rubber is one or a mixture of two or more of modified or unmodified butyl rubber, natural rubber, styrene-butadiene rubber, cis-butadiene rubber, isoprene rubber, ethylene-propylene-diene rubber, chlorobutyl rubber, and nitrile rubber, preferably natural rubber, cis-butadiene rubber, and styrene-butadiene rubber, further preferably natural rubber and cis-butadiene rubber, and still further preferably cis-butadiene rubber; and the amount of the diene structural unit-containing rubber is 20-70 parts, further preferably 40-60 parts.

[0018] Further, the reinforcing filler selected by the present application is one or a mixture of two or more of carbon black, acetylene black, white carbon black, carbon nanotube, graphite, graphene; the use of reinforcing filler can adjust the processability and dimensional stability of the self-sealing adhesive; the use of reinforcing filler with high specific surface area is beneficial to improve the dimensional stability during coating and use, but is not conducive to the flowability and self-sealing property of the adhesive; the use of reinforcing filler with low specific surface area can better balance the self-sealing property and dimensional stability. The reinforcing filler is preferably carbon black or white carbon black; the specific surface area of the carbon black is 20-160 m 2 / g, and the specific surface area of the white carbon black is 30-250 m 2 / g; preferably, the specific surface area of the carbon black is 30-140 m 2 / g, and the specific surface area of the white carbon black is 40-180 m 2 / g; further preferably, the specific surface area of the carbon black is 40-120 m 2 / g, and the specific surface area of the white carbon black is 50-160 m 2 / g. Preferably, the carbon black is one or a combination of N110, N121, N134, N220, N231, N234, N242, N293, N299, N315, N326, N330, N332, N339, N343, N347, N351, N358, N375, N539, N550, N582, N630, N642, N650, N683, N754, N762, N765, N774, N787, N907, N908, N990 and N991; the iodine absorption value of the carbon black is 5-150 g / kg, and the DBP absorption value is 30-150 cm 3 / 100 g. The amount of the reinforcing filler is 2-40 parts, and further preferably 5-20 parts.

[0019] Further, the filler selected by the present application is one or a mixture of two or more of calcium carbonate, talc, clay, kaolin, aluminum hydroxide, aluminum oxide, calcium hydroxide, calcium oxide, magnesium hydroxide, magnesium oxide; the filler is generally a non-reinforcing filler, which has a large particle size and low specific surface area, and its basicity can promote the dehalogenation crosslinking reaction of halogenated butyl rubber; the metal ions provided by the filler and the polar groups in the system can form ionic or complex bonds to achieve a good balance between the flowability and dimensional stability of the adhesive. The filler is preferably calcium carbonate, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, magnesium oxide; further preferably, it is calcium carbonate, aluminum hydroxide, calcium hydroxide, magnesium oxide. The amount of the filler is 1-40 parts, and further preferably 2-20 parts.

[0020] Further, the main purpose of the selected resin is to increase the adhesion of the self-sealing glue, which can increase the adhesion to nails on one hand, and can form a package to the nails when the nails pierce the self-sealing glue, and the self-sealing glue adhered to the nails can be taken out together with the nails after the nails are pulled out, thereby filling the hole to achieve the sealing effect. However, too much resin will cause the modulus of the self-sealing glue to increase and the flowability to decrease under normal use conditions, so that after the nail pierces, the hole cannot be self-sealed in time. The softening point of the selected resin is 10-160℃, and the molecular weight is 500-3000g / mol; preferably, the softening point is 40-145℃, and the molecular weight is 700-2500g / mol; further preferably, the softening point is 60-130℃, and the molecular weight is 800-2000g / mol. The resin is one or a mixture of two or more of C5 resin, C9 resin, C5 / C9 resin, hydrogenated C5 resin, hydrogenated C9 resin, rosin resin, terpene resin, dicyclopentadiene resin, hydrogenated dicyclopentadiene resin, phenolic resin, coumarone-indene resin, limonene resin, preferably phenolic resin, rosin resin, terpene resin, coumarone-indene resin, and further preferably phenolic resin, terpene resin. The amount of the resin is 1-60 parts, preferably 4-40 parts, and further preferably 8-20 parts.

[0021] Further, the selected plasticizer is one or a mixture of two or more of modified or unmodified polyisoprene, polybutadiene, polyisobutylene, polybutene, isobutylene butene copolymer, styrene butadiene copolymer, isoprene butadiene copolymer, mineral oil, vegetable oil; the plasticizer can adjust the flowability and self-adhesion of the rubber compound, and the more the amount of the plasticizer, the better the flowability and self-sealing property of the rubber compound, but the dimensional stability will be poor. In addition, the glass transition temperature Tg of the plasticizer also affects the low-temperature flowability of the self-sealing glue, and the glass transition temperature Tg of the plasticizer is -20 to -120℃, preferably -30 to -110℃, and further preferably -40 to -110℃. The plasticizer is preferably polyisoprene, polybutadiene, polyisobutylene, polybutene, isobutylene butene copolymer, and further preferably polyisobutylene, polybutene, isobutylene butene copolymer. Preferably, the plasticizer is PB1300, PB1400, PB2400, HV-15, HV-35, HV-50, HV-100, HV-300, HV-1900, SV-7000, LV-7, LV-50, LV-100; and the number average molecular weight of the plasticizer is 300-50000g / mol, preferably 600-30000g / mol, and further preferably 800-8000g / mol. The 40℃ kinematic viscosity of the plasticizer is 1000-1000000mm 2 / s, preferably 3000-800000mm 2 / s, further preferably 8000-600000 mm 2 / s. The amount of the plasticizer is 30-200 parts, further preferably 50-150 parts.

[0022] A second object of the present application is to provide a tire self-sealing glue prepared from the tire self-sealing rubber composition as described above.

[0023] And the preparation method of the tire self-sealing glue is specifically disclosed, which comprises two main steps: mixing in a banbury mixer or an open mill and mixing in a twin-screw extruder with a plasticizer; specifically:

[0024] Step 1): weighing raw materials; the raw materials include halogenated butyl rubber, diene structure unit-containing rubber, reinforcing filler, filler, resin, pyrrolinone crosslinking agent;

[0025] Step 2): after mixing the halogenated butyl rubber, diene structure unit-containing rubber, reinforcing filler, filler, resin and pyrrolinone crosslinking agent in a banbury mixer or an open mill, discharging to obtain a mixed material;

[0026] Step 3): after mixing the cooled mixed material with a plasticizer in a twin-screw extruder, discharging to obtain the tire self-sealing glue.

[0027] Optionally, the feeding sequence of Step 2) is: first feeding the halogenated butyl rubber and the diene structure unit-containing rubber and mixing for 30-120 seconds, then feeding the pyrrolinone crosslinking agent and mixing for 60-180 seconds, and then feeding the resin, reinforcing filler and filler and mixing for 60-300 seconds. The total mixing time of Step 2) is 150-600 seconds, preferably 240-600 seconds, further preferably 300-600 seconds; the discharging temperature is 100-160℃, preferably 115-150℃, further preferably 130-140℃.

[0028] Optionally, the mixing process of the twin-screw extruder in Step 3) is parallel co-rotating or parallel counter-rotating, preferably parallel co-rotating. The length-diameter ratio of the screw is 20-80, preferably 30-70, further preferably 40-60. The barrel setting temperature is 60-160℃, preferably 80-140℃, further preferably 100-120℃. The plasticizer feeding port is 1-6, preferably 2-5, further preferably 3-4. The temperature of the plasticizer feeding is 20-100℃, preferably 30-70℃, further preferably 30-60℃. Then the masterbatch prepared by the banbury mixer or the open mill is forcedly fed from the feeding port by a single-screw extruder, and the plasticizer is forcedly added from 3-4 liquid feeding ports by a metering liquid pump; the screw extruder is fully mixed and slowly extruded, and finally the tire self-sealing glue is obtained.

[0029] It should be noted that the processing method adopted by the present application is a traditional rubber master batch plus a double screw adding a large amount of plasticizer: the addition of a small amount of plasticizer in a general system is relatively simple, but the difficulty will increase sharply after more than 50 parts. In the internal mixer, the rubber will stick to the wall of the internal mixer, and it is difficult to take out, and the formula of the rubber taken out is not accurate, and when the plasticizer is added on the open mill, the rubber will also stick to the roller when a large amount of plasticizer is added, and due to the increasing strength of the rubber, it will be directly bonded to the roller in a broken state and cannot be removed. When mixing in the kneader, the viscosity difference between the masterbatch and the plasticizer is large, and a large amount of low-viscosity plasticizer is difficult to mix into high-viscosity masterbatch, and cannot be uniformly mixed. The present application uses a double screw mixing method to solve the problem of mixing a large amount of plasticizer into the masterbatch. The double screw has a large length-diameter ratio, and the screw elements inside can be adjusted and arranged in a large range. A large amount of plasticizer can be mixed into the masterbatch by a special method to form a uniformly mixed self-sealing rubber.

[0030] Compared with the prior art, the present application has the following advantages:

[0031] (1) The present application utilizes the excellent air tightness, flowability and self-adhesion of butyl rubber, diene structure unit-containing rubber and liquid polyisobutylene, increases the dimensional stability at high temperature by using pyrrolinone crosslinking agent for micro-crosslinking, while maintaining a certain flowability, and finally utilizes the similar solubility principle with liquid polyisobutylene rubber to prepare a self-sealing rubber by mixing according to a certain ratio.

[0032] (2) From the performance of the formula, the addition of butyl rubber plays a key role in air tightness; the addition of resin plays a key role in the adhesion of the self-sealing rubber; the addition of liquid polyisobutylene rubber plays a major role in the self-sealing performance; and the addition of pyrrolinone crosslinking agent plays a key role in maintaining the dimensional stability of the self-sealing rubber.

[0033] (3) The rubber composition with self-sealing performance prepared by the present application is coated on the outer part of the tire air tight layer corresponding to the tread part to form a self-sealing layer structure. The rubber with self-sealing performance has the performance of ensuring the rubber at-45℃-120℃ environment, and the tire will not leak after being punctured by foreign matter below 6mm and removed, and can be used normally; and the tire can be made into a silent tire or a tire with self-sealing and silent functions by pasting foam or other sound-absorbing materials thereon. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced. Obviously, the accompanying drawings in the following description only represent some embodiments of the present application, and for those skilled in the art, other drawings can be obtained without creative effort based on the accompanying drawings provided.

[0035] Fig. 1 is a graph showing the influence of different liquid polyisobutylene additive amounts on the Mooney viscosity of self-sealing glue.

[0036] Fig. 2 is a graph showing the influence of different liquid polyisobutylene additive amounts on the penetration of self-sealing glue.

[0037] Fig. 3 is a viscoelasticity curve. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments only represent some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative effort fall within the scope of the present application.

[0039] The term "embodiment" used herein as "exemplary" to illustrate any embodiment does not necessarily mean that it is superior or better than other embodiments. In the performance index test of the embodiments of the present application, unless otherwise specified, the conventional test method in the art is adopted. It should be understood that the terms described in the present application are only for describing the specific embodiments, and are not used to limit the disclosure of the present application.

[0040] Unless otherwise specified, the technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the art to which the present application belongs; and the test methods and technical means not specifically noted in the present application refer to the experimental methods and technical means commonly used by those skilled in the art.

[0041] In order to better illustrate the content of the present application, a large number of specific details are given in the specific embodiments below. Those skilled in the art should understand that the present application can also be implemented without some specific details. In the embodiments, some methods, means, instruments, equipment and the like which are well known to those skilled in the art are not described in detail, in order to highlight the main idea of the present application.

[0042] The technical features disclosed in the embodiments of the present application can be combined in any way without conflict, and the technical solutions obtained belong to the disclosure of the embodiments of the present application.

[0043] For better understanding of the present application, the present application is further specifically illustrated by the following examples, but it should not be understood as limiting the present application, and some non-essential improvements and adjustments made by those skilled in the art according to the above content of the application are also regarded as falling within the protection scope of the present application.

[0044] The tests of the self-sealing rubber composition in the present application are carried out according to the following standards and methods:

[0045] 1) Mooney viscosity: refer to ASTM D1646-2007, the test condition is that the final rubber is ML(1+4) 50℃ or the masterbatch is ML(1+4) 100℃. (Example Mooney viscosity / Comparative example Mooney viscosity)*100%, the larger the index, the higher the Mooney viscosity.

[0046] 2) Penetration: refer to GB / T 4509-2010, the value of the penetration of the self-sealing rubber is tested. (Example penetration / Comparative example penetration)*100%, the larger the index, the softer the rubber.

[0047] 3) Tensile strength and elongation at break: the obtained self-sealing rubber is pressed in a vulcanization mold at room temperature to obtain a 5mm rubber sheet, then refer to ASTM D412-2006, the sample is dumbbell-shaped, the test speed is 500mm / min, and the test environment temperature is 23±2℃. (Example tensile strength / Comparative example tensile strength)*100%, the larger the index, the higher the tensile strength. (Example elongation at break / Comparative example elongation at break)*100%, the larger the index, the greater the elongation at break.

[0048] 4) Tensile strength and elongation at break after cutting: the obtained self-sealing rubber is pressed in a vulcanization mold at room temperature to obtain a 5mm rubber sheet, then refer to ASTM D412-2006 to make the sample, which is dumbbell-shaped, then cut it in the middle with a cutter, bond it after 20 seconds, and place it for 1min, then test the tensile strength and elongation at break, the test speed is 500mm / min, and the test environment temperature is 23±2℃. (Example tensile strength after cutting / Comparative example tensile strength after cutting)*100%, the larger the index, the higher the tensile strength. (Example elongation at break after cutting / Comparative example elongation at break after cutting)*100%, the larger the index, the greater the elongation at break.

[0049] 5) Self-repairing rate: tensile strength after cutting / initial tensile strength, (Example self-repairing rate / Comparative example self-repairing rate)*100%, the larger the index, the better the self-repairing effect.

[0050] 6) Puncture sealability: The obtained self-sealing rubber compound was pressurized in a curing mold at room temperature to obtain a 5 mm rubber sheet, the release film on both sides was removed, and then a 4 mm nail was used to puncture the cured sheet at a speed of 50-300 mm / min until it was punctured, and whether it was punctured and the size of the puncture hole after the nail was pulled out and the degree of closure were observed. o Excellent closure, no obvious hole when pulling the cured sheet by hand; Δ Good closure, no hole without pulling; X Poor closure, obvious hole after puncture.

[0051] 7) Compression storage modulus temperature scanning: Metravib 1000+ DMA was used for testing in compression mode, static force 20 N, frequency 10 Hz, dynamic displacement 0.25%, temperature 25-150°C, and sample size was diameter 22 mm*height 5 mm.

[0052] 8) Gel content:

[0053] Toluene was used as the solvent, 0.2-0.25 g of the sample was cut and wrapped with filter paper and placed in a 50 mL vial, and the dissolution time was 4 days. The uncrosslinked part in the sample was dissolved, and the gel content of the sample was determined.

[0054] The calculation formula of the dissolution extraction rate (Xn) of the sample is: Xn = (mass of the sample before dissolution extraction - mass of the residual sample after dissolution extraction) / mass of the sample before dissolution extraction * 100%

[0055] The gel content (Wn) of the sample is: Wn = 1 - Xn (%)

[0056] (Example gel content / comparative example gel content) * 100%, the larger the index, the more gel.

[0057] 9) Crosslinking degree: torque difference during 170°C curing rheological test, S'max-S'min;

[0058] (Example crosslinking degree / comparative example crosslinking degree) * 100%, the larger the index, the higher the crosslinking degree

[0059] 10) High temperature dimensional stability, the rubber compound was prepared into a rubber sheet with a thickness of 3-3.5 mm and a length and width of 60 mm, and was scored at intervals of 2 cm to prepare a test sample. Then the test sample was placed in an oven at 150°C for 1 hour, and the flow of the score was observed. If the deformation is less than 5 mm, it is o, if the deformation is 5-10 mm, it is Δ, and if the deformation is greater than 10 mm, it is X;

[0060] The raw materials used in the following manufacturing examples / examples are as follows:

[0061] Brominated butyl rubber BIIR2302: Zhejiang Xinhui New Material Co., Ltd.

[0062] Butadiene rubber BR9000: Qilu Petrochemical Corporation

[0063] Natural rubber TSR20: No. 20 standard rubber, Sinochem International (Holding) Co., Ltd.

[0064] Carbon black N660: Cabot

[0065] White carbon HD60MP: Wuxi Quancheng Silicon Co., Ltd.

[0066] Calcium carbonate: Guangxi Huana New Material Technology Co., Ltd.

[0067] Aluminum hydroxide HT-205: Jinan Hongtu New Material Co., Ltd.

[0068] Phenolic tackifying resin SL-T421: Huachi Chemical Co., Ltd.

[0069] C5 hydrogenated resin: Zeon Corporation

[0070] Maleic rosin: Guangdong Kemolinyan Chemical Co., Ltd.

[0071] Rosin resin KE359: Arakawa Chemical Industries, Ltd.

[0072] Rosin KR616: Arakawa Chemical Industries, Ltd.

[0073] Liquid polyisobutylene PB1300, PB2400: Hanwha L&L

[0074] 3-methyl-5-pyrrolidone: Gled Pharma (Shanghai) Chemical Industry Development Co., Ltd.

[0075] Zinc oxide: Dalian Zinc Oxide Co., Ltd.

[0076] WS vulcanized resin: Huachi Chemical Co., Ltd.

[0077] DCP-40: Jiangsu Domino Chemical Co., Ltd.

[0078] Liquid polyisoprene LIR-50, liquid polybutadiene LBR-307: Kolon

[0079] Modified liquid polybutadiene POLYVEST MA75: Evonik

[0080] SEBS1726: Kraton Corporation

[0081] D1163, D1116: Kraton Corporation

[0082] APAO8825: Evonik

[0083] Unless otherwise specified, the composition of the self-sealing adhesive obtained in the production examples / embodiments was prepared by the following method:

[0084] Step one: through the internal mixer first into the base rubber (halogenated butyl rubber, butyl rubber, diene unit containing rubber) plasticizing 60 seconds, then put into crosslinking agent (such as pyrrolidone crosslinking agent, ZnO, WS vulcanized resin, DCP-40) mixing 120 seconds, finally put into resin (such as SL-T421, C5 hydrogenated resin, rosin resin, maleic rosin, hot melt adhesive SEBS and APAO, etc.), reinforcing filler (carbon black or white carbon black), filler (calcium carbonate, calcium hydroxide, etc.) 130-140℃ discharge; mixing time 600 seconds, that is, the completion of the self sealing glue masterbatch mixing process;

[0085] Step two: the self sealing glue masterbatch after cooling and placing is mixed with plasticizer (liquid polyisobutylene PB1300, liquid polybutadiene, etc.) by double screw extruder, using the same direction double screw extrusion mixing mode, screw length diameter ratio is 60, three zone temperature control is set to 120℃, the self sealing glue masterbatch is forced to feed from the feeding port by single screw extruder, and the plasticizer is forced to feed from three liquid feeding ports according to the ratio of 1:1:2 by metering liquid pump; after experiencing plasticizing, crushing, mixing and homogenizing four stages in the double screw extruder, it is slowly extruded, and finally the self sealing rubber composition with uniform mixing is obtained.

[0086] I. The preferred amount of plasticizer

[0087] A self sealing rubber composition, comprising: 60 parts of BIIR2302, 40 parts of butadiene rubber BR9000, 10 parts of tackifying phenolic resin SL-T421, 5 parts of calcium carbonate, 5 parts of carbon black N660, 0.2 parts of 3-methyl-5-pyrrolidone crosslinking agent, and several parts of liquid polyisobutylene PB1300 as follows

[0088] Table 1: comparison of raw materials and performance results of comparative examples 1 and 2 and examples 1-5

[0089] In Example 1, we investigated the influence of different liquid polyisobutylene addition amount on the properties of self-sealing glue. With the increase of the content of liquid polyisobutylene, the softness of the whole glue rises, which is reflected in the properties, that is, the Mooney viscosity decreases, the penetration value increases, and the measured gel content of the glue decreases. The addition of liquid glue also gradually reduces the tensile strength of the glue, but the efficiency of self-repair increases. And the sealing of the puncture nail gradually gets better. When the addition of liquid polyisobutylene is 30 parts or less, the glue is too hard and has insufficient flowability, and once the nail is punctured, the hole cannot be closed. When the content of liquid polyisobutylene in the self-sealing glue gradually increases, the self-adhesion and flowability of the glue become better, and the puncture sealing gradually becomes better. To ensure that the self-sealing glue has puncture sealing and subsequent use on the tire, it is necessary to ensure that the content of liquid polyisobutylene in the self-sealing glue is more than 40 parts or more (Example 1-1).

[0090] II. Rubber component and hot melt glue elastomer

[0091] Table 2: Comparison of raw materials and performance results of Comparative Examples 1, 2 and Example 1-6

[0092] Examples 2-1, 2-2, 2-3 list the changes in the crosslinking degree and self-sealing properties of the self-sealing glue in different proportions of BIIR2302 / BR9000. With the increase of the content of BIIR2302, the crosslinking degree of the whole system increases, but the puncture sealing remains, which is due to the high hysteresis loss and self-adhesion of the brominated butyl rubber. When the amount of BIIR2302 is further reduced, the self-repairing and puncture sealing will be poor (Comparative Example 2-2). In Comparative Example 2-1, the pure natural rubber system has poor puncture sealing due to the high molecular weight and entanglement of natural rubber and the characteristics of self-stretching crystallization, which leads to low molecular activity. It is not as good as the system with brominated butyl rubber. Examples 2-4, 2-5, 2-6 contain high hysteresis loss brominated butyl rubber BIIR2302 in the system, which is used with diene structural unit rubber. By adjusting the crosslinking degree (using sulfur or peroxide, vulcanized resin, etc.) or adding fillers (carbon black, white carbon black), oil, etc., impact-resistant materials can be made. This material has high hysteresis loss, and its hardness and tensile strength can be adjusted according to actual application, and can be used to make impact-resistant glue, elastomer, and applied to special glue or gloves, protective pads, etc.

[0093] The self-sealing property also needs to work at low temperatures, so to further improve the molecular chain activity of the rubber, in Examples 2-1 and 2-2, 2-3, butadiene rubber BR9000 with a lower glass transition temperature Tg was added, and the puncture sealing property was further improved. In addition, some patents such as CN 112823098 A also consider the case of hot melt adhesive, using pure hot melt adhesive or a mixed system of hot melt adhesive and rubber in the system, which can also achieve the effect of self-repair. Pure hot melt adhesive system has low viscosity after heating and melting, and many manufacturers can use spraying to coat on the surface of the tire, but due to the inner cavity surface of the tire is not a flat surface but a certain curvature slope, which will cause the coating thickness of the sealant to be uneven, affecting its dynamic balance and self-sealing property. The following is an example of our investigation of hot melt adhesive elastomers and mixed rubbers.

[0094] Table 3: Comparison of raw materials and performance results of Comparative Examples 3, 4, 5, 6 and Example 2-7

[0095] The hot melt adhesive commonly used in industry is mainly an ABA type block copolymer, with a soft rubber-like molecular chain segment in the middle and a rigid plastic-like polystyrene segment at both ends (such as SIS and SBS). In order to increase its oxidation resistance, the rubber segment in the middle also has a hydrogenated grade (SEBS). In order to maintain the softness of the glue as much as possible, the case group selected SIS (D1163) and SBS (D1116) with low styrene content, and SEBS and APAP were used as comparative examples. Since the Tg of the hot melt adhesive elastomer is higher than that of the rubber system, the self-sealing glue body will become hard, G' will increase, and the tensile strength will increase, and the self-sealing property will deteriorate. As can be seen from the viscoelasticity curve (Figure 3), the modulus of the hot melt adhesive system decreases rapidly after passing through its softening point at high temperature, but the modulus is actually larger at lower temperatures, which is not conducive to the formation of self-sealing effect. The modulus of the hot melt adhesive elastomer is very low at high temperature, but after returning to room temperature, due to the alternating soft and hard segments forming a cross-linked effect, the modulus at room temperature is relatively high, which is not conducive to the self-sealing property. Therefore, the effect of adding hot melt adhesive elastomer in the case group will deteriorate.

[0096] III. Selection of crosslinking agent

[0097] Table 4: Comparison of raw materials and performance results of Comparative Examples 1-5 and Example 1-4

[0098] For diene rubber and brominated butyl rubber, different kinds of vulcanizing agents and accelerators can be used for crosslinking, commonly used mainly sulfur, peroxide, phenolic resin, metal oxide, etc. In this case, we selected phenolic resin, WS vulcanizing resin, metal oxide ZnO, peroxide DCP-40, and sulfur. The application of sulfur is more common and has a larger crosslinking density, so the application of sulfur is not further exemplified in this application.

[0099] For different crosslinking agents, with the increase of crosslinking density, the strength and hardness increase. The increasing speed is: DCP-40> WS vulcanizing resin>ZnO-80>3-methyl-5-pyrroline ketone. If ZnO is used together, the crosslinking density will further increase, and the use of 3-methyl-5-pyrroline ketone can achieve a smaller increase in crosslinking density. It can be seen that 0.2 phr of 3-methyl-5-pyrroline ketone can increase the crosslinking degree of the masterbatch, but the increase is smaller than that of other vulcanizing agents. When the crosslinking degree index is >110, the puncture sealing performance is poor and the self-repairing performance is also poor. For self-sealing glue, controlling the appropriate crosslinking degree is the key to ensure its puncture sealing performance and self-repairing performance. The two nitrogens on 3-methyl-5-pyrroline ketone will attack the bromine atoms on the brominated butyl rubber when the temperature rises above 140 degrees, causing the brominated butyl rubber to crosslink. At the same time, 3-methyl-5-pyrroline ketone can also graft with butadiene rubber BR at high temperature, and then form hydrogen bonds (such as the hydroxyl groups in tackifying resin SL-T421 or the ketone groups and amino groups of 3-methyl-5-pyrroline ketone itself) with the rubber system, complex bonds and ionic bonds, enhancing its self-repairing ability. As a highly active crosslinking agent, 3-methyl-5-pyrroline ketone will graft to the molecular chain of brominated butyl rubber during vulcanization and form a crosslinking network structure, so that the entire system forms a multi-energy level network system with hydrogen bonds, complex bonds, ionic bonds and covalent bonds. When the nail is punctured and pulled out, the multi-energy level structure plays a role at different time scales to achieve self-sealing and self-repairing effect.

[0100] Four, the preferred resin

[0101] Table 5: Comparison of raw materials and performance results of Comparative Examples 1-2 and Examples 1-4

[0102] ​The main purpose of adding resin is to increase the viscosity of the self-sealing adhesive, which can increase the adhesion to nails and form a package around the nails when the nails pierce the self-sealing adhesive. The self-sealing adhesive adhering to the nails can be removed with the nails, thereby achieving the sealing effect. However, excessive addition of resin can cause the modulus of the self-sealing adhesive to increase significantly under normal use conditions, and the flowability to decrease, thereby making it difficult to form displacement and repair the pierced hole after the nail pierces it. It can be found in Example Group 4 that the puncture sealing performance of the phenolic tackifying resin and the rosin resin is better, and the C5 hydrogenated resin and the maleic rosin have poor effects, which is mainly because the Tg of the latter two is larger, causing the glue to be harder.

[0103] V. Preferred Reinforcing Fillers

[0104] Table 6: Comparison of raw materials and performance results of Comparative Examples 1-2 and Examples 1-3

[0105] With the addition of carbon black N660, the tensile strength of the self-sealing adhesive increases, but the self-sealing performance becomes worse. The same applies to white carbon black HD60MP, which mainly plays a reinforcing role and causes the combined rubber to appear in the system. However, the combined rubber hinders molecular movement and reduces the self-sealing effect. When the reinforcing filler is added in an amount of more than 5 parts, the puncture sealing performance becomes worse.

[0106] VI. Preferred Fillers

[0107] Table 7: Comparison of raw materials and performance results of Comparative Examples 1-2 and Examples 1-3

[0108] In order to reduce the rubber content, improve the processability, or reduce the cost of the self-sealing adhesive, a part of the filler is added. It is found through comparison that the addition of part of the filler can increase the overall crosslinking degree and the tensile strength, which is not conducive to the realization of the self-sealing function. Calcium carbonate and calcium hydroxide are two good fillers that basically do not cause a significant increase in the crosslinking density of the masterbatch. However, ZnO and aluminum hydroxide can further increase the crosslinking density of the masterbatch, thereby degrading the self-sealing performance.

[0109] VII. Selection of Different Plasticizers

[0110] Table 8: Comparison of raw materials and performance results of Comparative Example 1 and Example 1-4

[0111] Different liquid gums were tested for their self-healing properties. Polyisobutylene has good compatibility with butyl rubber due to its similar molecular structure. Low molecular weight polyisobutylene has good tackiness, but low strength. As the molecular weight increases, the tackiness decreases, but the strength increases. In addition to liquid polyisobutylene, liquid polybutadiene LBR and liquid polyisoprene LIR are also liquid materials that have good compatibility with butyl rubber and cis-butadiene rubber. They also have good puncture sealing properties, but are expensive and not suitable for large-scale production. In this system, the addition of hydrogen bond-related functional groups can improve the self-healing properties from a mechanistic point of view. In this case, the modified product of liquid polybutadiene, such as POLYVEST MA75, has a modified double bond with maleic anhydride, which increases its reactivity and reduces its self-healing properties. Polyisobutylene is the preferred plasticizer due to its excellent self-healing properties (self-healing rate) and low cost, and further preferred PB1300 with a number average molecular weight Mn of 800-1500 g / mol.

[0112] The above description of disclosed embodiments enables one skilled in the art to make or use the application. Numerous modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be applied to other embodiments without departing from the spirit or scope of the application. Therefore, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A self-sealing rubber composition for tires, characterized by, The rubber composition comprises at least one halogenated butyl rubber, and is crosslinked by a pyrrolinone crosslinking agent without using sulfur, zinc oxide and accelerators, and is combined with a rubber comprising a diene structural unit, a resin, a reinforcing filler, a filler and a plasticizer; The structure of the pyrrolinone crosslinking agent is: In the formula, R1, R2, R3 and R4, which are the same or different, represent a hydrogen atom, an alkyl group, an aralkyl group, an aryl group or a heterocyclic group; R3 and R4 are optionally linked together to form an alkylene group, and any two of R2, R3 and R4 are optionally linked together to form an alkylene group; each of these groups optionally has one or more substituents; further, R1, R3 and R4 are hydrogen atoms, and R2 is a methyl group. or the structure of the pyrrolinone crosslinking agent is: In the formula, R5, R7 and R8, which are the same or different, represent a hydrogen atom, an amino group, an alkyl group, an aralkyl group, an aryl group or a heterocyclic group, and R6 represents an alkyl group, an aralkyl group, an aryl group or a heterocyclic group; further, R5, R6 and R8 are hydrogen atoms, and R7 is a methyl group.

2. The self-sealing rubber composition for tires according to claim 1, characterized by, The rubber composition mainly comprises the following components in parts by weight: The halogenated butyl rubber is one or more of chlorinated butyl rubber and brominated butyl rubber, and the amount of the halogenated butyl rubber is 30-80 parts. The rubber comprising a diene structural unit is one or more of modified or unmodified butyl rubber, natural rubber, styrene-butadiene rubber, cis-butadiene rubber, isoprene rubber, ethylene-propylene-diene rubber, chlorobutyl rubber and nitrile rubber, and the amount of the rubber comprising a diene structural unit is 20-70 parts.

3. The self-sealing rubber composition for tires according to claim 2, characterized in that, The pyrrolinone compound is one or more of 3-methyl-5-pyrrolinone, 3-phenyl-5-pyrrolinone, 3-ethyl-5-pyrrolinone, 3-propyl-5-pyrrolinone and 3-butyl-5-pyrrolinone.

4. The self-sealing rubber composition for tires according to claim 2, characterized by, The reinforcing filler is one or more of carbon black, acetylene black, white carbon black, carbon nanotube, graphite and graphene, and the amount of the reinforcing filler is 2-40 parts.

5. The self-sealing rubber composition for tires according to claim 1 or 2, characterized in that, The filler is one or more of calcium carbonate, talc, clay, kaolin, aluminum hydroxide, aluminum oxide, calcium hydroxide, calcium oxide, magnesium hydroxide and magnesium oxide, and the amount of the filler is 1-40 parts.

6. The self-sealing rubber composition for tires according to claim 2, characterized by, The resin has a softening point of 10-160°C and a molecular weight of 500-3000 g / mol; the resin is one or more of C5 resin, C9 resin, C5 / C9 resin, hydrogenated C5 resin, hydrogenated C9 resin, rosin resin, terpene resin, dicyclopentadiene resin, hydrogenated dicyclopentadiene resin, phenolic resin, coumarone-indene resin and limonene resin; and the amount of the resin is 4-40 parts.

7. The self-sealing rubber composition for tires according to claim 2, characterized by, ​ 8. The self-sealing rubber composition for tires according to claim 2, characterized by, ​ 9. The self-sealing rubber composition for tires according to claim 2, characterized by, The plasticizer is one or more mixtures of modified or unmodified polyisoprene, polybutadiene, polyisobutylene, polybutene, isobutylene butene copolymer, styrene butadiene copolymer, isoprene butadiene copolymer, mineral oil, vegetable oil; the number average molecular weight of the plasticizer is 300-50000 g / mol; the amount of the plasticizer is 30-200 parts.

10. A self-sealing rubber for tires, characterized by, The self-sealing rubber for tires is prepared from the self-sealing rubber composition for tires according to claim 1.

11. A method of preparing a self-sealing rubber for tires as claimed in claim 9, characterized in that, The method specifically comprises the following steps: Step 1): weighing raw materials; the raw materials include halogenated butyl rubber, rubber containing diene structural unit, reinforcing filler, filler, resin, pyrrolinone crosslinking agent; Step 2): after mixing the halogenated butyl rubber, rubber containing diene structural unit, reinforcing filler, filler, resin, pyrrolinone crosslinking agent in a mixer or open mill, the mixed material is discharged to obtain a mixed material; Step 3): after mixing the cooled mixed material with a plasticizer in a twin-screw extruder, the mixed material is discharged to obtain the self-sealing rubber for tires.

12. The method for preparing the self-sealing adhesive for tires according to claim 10, characterized in that, The feeding sequence of step 2) is: first, the halogenated butyl rubber and the rubber containing diene structural unit are mixed for 30-120 seconds, then the pyrrolinone crosslinking agent is added and mixed for 60-180 seconds; subsequently, the resin, reinforcing filler and filler are added and mixed for 60-300 seconds; and the discharge temperature is 100-160℃.

13. The method for preparing the self-sealing adhesive for tires according to claim 10, characterized in that, In step 3), the twin-screw extruder has parallel co-directional or parallel opposite-directional rotation of the screw, a length-diameter ratio of the screw of 20-80, a barrel setting temperature of 60-160℃, and 1-6 plasticizer feeding ports; and the temperature of the plasticizer feeding is 20-100℃.

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