CN108641150B

CN108641150B - Rubber material capable of being repeatedly processed and preparation method thereof

Info

Publication number: CN108641150B
Application number: CN201810306131.0A
Authority: CN
Inventors: 郭宝春; 邱敏; 吴思武; 唐征海
Original assignee: South China University of Technology SCUT
Current assignee: South China University of Technology SCUT
Priority date: 2018-04-08
Filing date: 2018-04-08
Publication date: 2021-01-19
Anticipated expiration: 2038-04-08
Also published as: CN108641150A

Abstract

The invention discloses a rubber material capable of being repeatedly processed and a preparation method thereof. The method of the invention introduces carboxyl on the surface of the filler through diazotization grafting reaction to obtain the modified filler, and the modified filler, the epoxidized rubber and the catalyst are mixed and thermally crosslinked to obtain the rubber material capable of being repeatedly processed. The rubber material capable of being repeatedly processed has excellent repeated processing performance, and can obviously improve the physical and mechanical properties of the rubber material. The method has simple process and low cost, does not need to add extra processing equipment and fussy steps, and has important application prospect in preparing the repeatable processing rubber material with high mechanical property.

Description

Rubber material capable of being repeatedly processed and preparation method thereof

Technical Field

The invention relates to the field of rubber modification, in particular to a reworkable rubber material prepared by utilizing an interface between a filler and rubber to exchange covalent bonds and a preparation method thereof.

Background

Rubber is widely used for manufacturing tires, shock absorbing members, insulating members, sealing members, etc. because of its unique high elasticity, excellent stretchability, shock absorbing property, abrasion resistance and processability. However, unreinforced rubbers have low strength, poor abrasion resistance and fatigue resistance, and are not of practical value, and therefore reinforcement is generally achieved by adding nanofillers. Common nanofillers include carbon black, white carbon black, carbon nanotubes, graphene, clay, and the like. However, these nanofilled rubber composites are typically crosslinked by sulfur or peroxides, and other adjuvants (guanidines, thiazoles, thiurams, etc.) are added to accelerate the rate of cure. The formation of permanent irreversible covalent bonds (C-S and C-C bonds) leads to a non-reworkable and remoldable shaping of the rubber composite, and in addition, the sulphur and the peroxide and the auxiliaries have a certain toxicity and are subjected to a vulcanization processThermal decomposition releases toxic gas (SO)₂And H₂S, etc.), which are harmful to the human body and the environment. At present, the annual production amount of waste tires in China exceeds 1000 ten thousand tons, the harmless utilization rate is only 60 percent, and the accumulated waste tires are piled in the open air for a long time, so that serious black pollution and resource waste are caused. Therefore, how to prepare the recyclable rubber composite material has strategic significance on resource conservation and environmental protection. At present, waste rubber is generally recycled through dynamic desulfurization, but the recycling efficiency is low, the recycling cost is high, and the performance of the recycled rubber is poor.

Under the action of heat, the exchangeable covalent bonds can generate continuous and effective exchange reaction among different crosslinking points of organic polymer molecular chains, so that the polymer is endowed with fluidity without damaging the structure and the performance of the polymer. Common exchangeable reactions include transesterification, transalkylation, olefin metathesis, siloxane silanol exchange, and disulfide exchange, among others. Under the action of high-temperature heat, exchangeable reaction is activated, and a polymer cross-linked network is subjected to topological structure rearrangement, so that the thermoplastic elastomer has malleability and reprocessing capability; at normal temperature, the exchangeable reaction is frozen and the crosslinked polymer behaves like a thermoset.

The invention starts from the surface modification of the rubber filler, and introduces organic carboxylic acid groups on the surface of the general rubber filler through universal diazotization reaction. In the hot-pressing vulcanization process of the modified filler and the epoxidized rubber, carboxylate radicals on the surface of the filler react with epoxy groups of the rubber to form interfacial covalent bond crosslinking of beta-hydroxy ester under the action of a proper reaction accelerator and a proper catalyst, so that the strength of the obtained rubber composite material is greatly improved. Meanwhile, due to the heat exchangeable characteristic of the beta-hydroxy ester, the cross-linked network topology structure of the rubber material can generate plastic flow under the action of heat, and the cross-linking density is kept unchanged, so that the repeatable processing capacity is obtained. The high-strength rubber material with the repeatable processing characteristic has important theoretical significance and practical significance for the sustainable development of rubber.

Disclosure of Invention

In order to overcome the above-mentioned disadvantages and shortcomings of the prior art, the present invention is directed to a reworkable high-strength rubber material prepared by constructing an interface by exchangeable covalent bonds and a method for preparing the same.

The invention discloses a general rubber filler surface organic carboxylic acid group diazotization reaction, and the modified filler is used for crosslinking epoxidized rubber, so that a beta-hydroxy ester interface covalent bond is formed on a rubber-particle interface, and the rubber material is endowed with excellent mechanical properties. Meanwhile, the exchangeable characteristic of the beta-hydroxy ester under the action of heat is utilized to endow the rubber material with the rearrangement characteristic of a cross-linked network, so that the high-strength rubber material capable of being repeatedly processed is prepared.

The purpose of the invention is realized by the following technical scheme.

A preparation method of a high-strength rubber material capable of being repeatedly processed comprises the following steps:

(1) introducing organic carboxylic acid groups on the surface of the filler through a grafting reaction;

(2) and mixing and thermally crosslinking the carboxyl modified filler, the epoxidized rubber, the reaction promoter and the catalyst to obtain the reworkable rubber material.

Further, the grafting reaction in the step (1) refers to a diazotization reaction.

Further, the filler in the step (1) refers to one or more of carbon nano-materials, silica, silicate and metal oxides.

Further, the carbon nanomaterial refers to carbon black, graphene, carbon nanotubes and spherical fullerene.

Further, the organic carboxylic acid group in the step (1) has the general formula

And R is alkyl or aromatic hydrocarbon.

Further, the content of the carboxylic acid groups in the step (1) is 2-5 mmol/g.

Further, the epoxidized rubber in the step (2) is one of epoxidized natural rubber, epoxidized butadiene rubber, epoxidized styrene-butadiene rubber and epoxidized nitrile-butadiene rubber; the molar ratio of epoxide groups to carboxylic acid groups is from 20:1 to 6: 1.

Further, in the step (2), the reaction promoter is Lewis base, and the catalyst is metal salt and chelate thereof; the content of Lewis base is 5% -20% of the mole content of carboxylic acid group, and the content of metal salt and chelate is 5% -15% of the mole content of carboxylic acid group.

Further, the temperature of the thermal crosslinking in the step (2) is 160-.

A reworkable rubber material is prepared by any one of the above preparation methods.

The basic principle of the invention is as follows: introducing organic carboxylic acid groups on the surface of a general rubber filler by utilizing the universality of diazo chemistry, crosslinking the epoxidized rubber by using a modified filler, reacting the carboxylic acid groups on the surface of the filler with epoxy groups of the rubber in the hot-pressing vulcanization process, and forming the interface connection of beta-hydroxy ester under the action of a proper reaction accelerator and a catalyst; the modified filler simultaneously serves as a rubber reinforcing agent and a crosslinking agent, so that the rubber has excellent mechanical properties; meanwhile, due to the heat exchangeable characteristic of the beta-hydroxy ester, the cross-linked network topology structure of the rubber material can generate plastic flow under the action of heat, and the cross-linking density is kept unchanged, so that the repeatable processing capacity is obtained.

Compared with the prior art, the invention has the following advantages and beneficial effects:

(1) the invention introduces organic carboxylic acid group on the surface of the filler by simple and universal diazotization reaction. The modified filler has excellent dispersion in a polar epoxidized rubber matrix, and simultaneously, the filler particles and the rubber matrix can form interfacial covalent bonds in the hot-press vulcanization process, so that the particle-crosslinked rubber has excellent mechanical properties.

(2) Due to the exchangeable characteristic of the interface covalent bond, the rubber material can be endowed with repeatable processing capability.

(3) The main raw materials of the method adopt industrial universal raw materials, the process is simple, the cost is low, additional processing equipment and complicated steps are not needed, and the method has important prospect in preparing high-strength rubber materials capable of being repeatedly processed.

Detailed Description

The present invention will be described in further detail with reference to specific examples, but the embodiments of the present invention are not limited thereto, and may be carried out with reference to conventional techniques for process parameters not particularly noted.

Example 1

(1) Carbon nano tubes are used as raw materials, isoprene nitrite is used as a catalyst, biphenyl dicarboxylic acid groups are introduced on the surfaces of the carbon nano tubes through diazotization chemistry, and the content of carboxyl groups is 2 mmol/g. The carboxyl-modified carbon nanotubes, epoxidized nitrile rubber and catalysts (zinc chloride and 1, 2-dimethylimidazole) were mixed using a two-roll mill, and the resulting rubber compound was compression molded with flat vulcanized rubber at 160 ℃ for 80 min, the molar ratios of epoxy groups to carboxylic acids were 15:1, 12:1 and 9:1, respectively, and the contents of zinc chloride and 1, 2-dimethylimidazole were 5% and 10% of the molar content of carboxylate groups, respectively, to give sample 1, sample 2 and sample 3. And shearing the sample 1, the sample 2 and the sample 3, and then hot-pressing again for 30 min at 160 ℃ to respectively obtain a reprocessed sample 1, a reprocessed sample 2 and a reprocessed sample 3.

Example 2

(1) Carbon black is used as a raw material, isoprene nitrite is used as a catalyst, and a benzoic acid group is introduced on the surface of the carbon black through diazotization reaction, wherein the carboxyl content is 3 mmol/g. The carboxyl-modified carbon black, epoxidized natural rubber and a catalyst (zinc acetate and 2, 4-lutidine) were mixed using a two-roll mill, and the resulting rubber compound was compression molded with flat vulcanized rubber at 180 ℃ for 60 min, with the molar ratios of epoxy group to carboxylic acid being 20:1, 10:1 and 6:1, respectively, to give sample 4, sample 5 and sample 6. And shearing the sample 4, the sample 5 and the sample 6, and then hot-pressing again for 30 min at the temperature of 180 ℃ to respectively obtain a reprocessed sample 4, a reprocessed sample 5 and a reprocessed sample 6.

Example 3

Taking white carbon black as a raw material, taking isoprene nitrite as a catalyst, and introducing phenylacetic acid groups on the surface of the white carbon black through diazo chemistry, wherein the carboxyl content is 5 mmol/g. The carboxyl-modified white carbon black, epoxidized styrene-butadiene rubber and a catalyst (zinc chloride and 1,5, 7-triazabicyclo [4.4.0] dec-5-ene) were mixed by a two-roll mill, and the obtained rubber compound was compression-molded with a flat vulcanized rubber at 200 ℃ for 30 min, with molar ratios of epoxy group to carboxylic acid being 14:1, 11:1 and 7:1, respectively, to obtain sample 7, sample 8 and sample 9. After cutting the sample 7, the sample 8 and the sample 9, hot pressing is carried out again for 30 min at 200 ℃, and a reprocessed sample 7, a reprocessed sample 8 and a reprocessed sample 9 are respectively obtained.

The properties of all samples and the control were tested in full according to the corresponding national standards of China (ISO 37-2005) and are listed in Table 1.

TABLE 1 original and reprocessed mechanical Properties of the samples of examples 1-3

Test items	Tensile Strength (MPa)	Modulus M100 (MPa)	Elongation at Break (%)
				Sample 1	9.5	2.0	348
Sample 2	15.0	4.5	292
				Sample 3	18.7	8.2	234
Reprocessed sample 1	6.6	1.9	260
				Reprocessed sample 2	11.5	3.6	220
Reprocessed sample 3	16.9	7.8	196
				Sample No. 4	10.3	1.7	527
Sample No. 5	13.3	2.8	425
				Sample No. 6	15.7	4.8	338
Reprocessed sample 4	8.0	1.0	603
				Reprocessed sample 5	10.0	1.6	470
Reprocessed sample 6	13.1	2.5	400
				Sample 7	4.7	0.8	500
Sample 8	7.2	1.1	420
				Sample 9	10.2	1.5	350
Reprocessed sample 7	4.0	0.6	400
				Reprocessed sample 8	6.6	0.8	360
Reprocessed sample 9	9.3	1.2	280

Table 1 shows that the process of the invention makes it possible to prepare rubber composites having excellent mechanical properties and good reworkability.

The above examples of the present invention are merely examples for clearly illustrating the present invention and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. The preparation method of the rubber material capable of being repeatedly processed is characterized by comprising the following steps of:

(1) introducing organic carboxylic acid groups on the surface of the filler by a grafting reaction, wherein the general formula of the organic carboxylic acid groups is

R is alkyl or aromatic hydrocarbon;

(2) and (2) mixing and thermally crosslinking the organic carboxylic acid group modified filler, the epoxidized rubber, the reaction promoter and the catalyst in the step (1) to obtain the rubber material capable of being repeatedly processed.

2. The method for preparing a reworkable rubber material according to claim 1, wherein in step (1), the grafting reaction is a diazotization reaction.

3. The method for preparing a reworkable rubber material according to claim 1, wherein in the step (1), the filler is one or more of carbon nanomaterial, silica, silicate and metal oxide.

4. The method as claimed in claim 3, wherein the carbon nanomaterial is selected from the group consisting of carbon black, graphene, carbon nanotube and fullerene.

5. The method for preparing a reworkable rubber material according to claim 1, wherein in step (1), the organic carboxylic acid group content is from 2 to 5 mmol/g.

6. The method for preparing a reworkable rubber material according to claim 1, wherein in step (2), the epoxidized rubber is one of epoxidized natural rubber, epoxidized butadiene rubber, epoxidized styrene-butadiene rubber and epoxidized nitrile-butadiene rubber, and the molar ratio of epoxy groups to carboxylate groups is 6:1-20: 1.

7. The method for preparing a reworkable rubber material according to claim 1, wherein in said step (2), the reaction promoter is a lewis base, and the catalyst is a metal salt or a chelate thereof; the content of Lewis base is 5% -20% of the mole content of carboxylic acid group, and the content of metal salt and chelate is 5% -15% of the mole content of carboxylic acid group.

8. The method as claimed in claim 1, wherein the thermal crosslinking temperature in step (2) is 160-200 ℃ for 30-80 min.

9. A reprocessable rubber material obtained by the production method according to any one of claims 1 to 8.