1. The flame-retardant nitrile rubber composition is characterized by comprising the following components which are stored in a mixed manner or independently:

nitrile butadiene rubber matrix, lignin, an interface modifier, a softener, a vulcanization assistant and a flame retardant,

the interface modifier is at least one of epoxidized hydroxyl-terminated polybutadiene rubber, epoxidized epoxy-terminated butadiene-acrylonitrile rubber and epoxidized carboxyl-terminated butadiene-acrylonitrile rubber, and the flame retardant is zinc phytate and/or calcium phytate;

relative to 100 parts by weight of the nitrile rubber matrix, the content of the lignin is 5-150 parts by weight, the content of the interface modifier is 0.5-50 parts by weight, the content of the softener is 2-35 parts by weight, the content of the flame retardant is 0.1-40 parts by weight, and the content of the vulcanization aid is 0.1-30 parts by weight.

2. The composition according to claim 1, wherein the lignin is contained in an amount of 10 to 100 parts by weight, the interphase modifier is contained in an amount of 1 to 40 parts by weight, the softening agent is contained in an amount of 2 to 30 parts by weight, the flame retardant is contained in an amount of 1 to 30 parts by weight, and the vulcanization aid is contained in an amount of 2 to 15 parts by weight, relative to 100 parts by weight of the nitrile rubber matrix.

3. The composition as claimed in claim 1 or 2, wherein the interface modifier has a number average molecular weight of 1000-;

preferably, the interface modifier is epoxy-terminated nitrile rubber and/or epoxy carboxyl-terminated nitrile rubber;

preferably, the content of acrylonitrile structural units in the epoxy-terminated nitrile rubber and the epoxidized carboxyl-terminated nitrile rubber are each independently 10 to 35 wt%.

4. The composition according to any one of claims 1 to 3, wherein the acrylonitrile rubber matrix has an acrylonitrile structural unit content of 20 to 50% by weight and a Mooney viscosity of 35 to 90;

preferably, the content of phenolic hydroxyl in the lignin is more than or equal to 3.0 weight percent, and the number average molecular weight is 2500-5500;

preferably, the lignin is at least one selected from the group consisting of organosolv lignin extracted from lignocellulosic material by organosolv processes, Kraft lignin extracted from Kraft process pulp waste, enzymatic lignin extracted from fermentation ethanol, and alkali lignin obtained from paper making alkaline pulping.

5. The composition of any of claims 1-4, wherein the vulcanization aid comprises a crosslinking agent, and optionally further comprises a crosslinking aid;

preferably, the cross-linking agent is selected from dicumyl peroxide, benzoyl peroxide, bis (2, 4-dichlorobenzoyl) peroxide, di-t-butyl peroxide, t-butyl perbenzoate, t-butylcumyl peroxide, methyl ethyl ketone peroxide, at least one of cumene hydroperoxide, 2, 5-dimethyl-2, 5-di (tert-butylperoxy) hexane, 2, 5-dimethyl-2, 5-di (benzoyl peroxide) hexane, 2, 5-dimethyl-2, 5-di (tert-butylperoxy) hexyne-3, 1-di-tert-butylperoxy-cyclohexane, 1-di-tert-butylperoxy-3, 3, 5-trimethylcyclohexane and 1, 3-bis (tert-butylperoxypropyl) benzene, preferably the crosslinking agent is dicumyl peroxide;

preferably, the crosslinking coagent is selected from at least one of triallyl isocyanurate, triallyl cyanurate, N' -m-phenylene-bismaleimide, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, methylene thiuram hexasulfide, zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc ethylphenyldithiocarbamate and sulfur, preferably the crosslinking coagent is triallyl isocyanurate.

6. The composition of claim 5, wherein the vulcanization aid is a cross-linking agent and a cross-linking aid, and the content weight ratio of the cross-linking agent to the cross-linking aid is 1: (0.5-2);

preferably, the vulcanization aid is dicumyl peroxide and triallyl isocyanurate, and the content weight ratio of the dicumyl peroxide to the triallyl isocyanurate is 1: (0.5-2).

7. The composition according to any one of claims 1 to 6, wherein the softening agent is at least one selected from the group consisting of paraffin oil, naphthenic oil, hydroxysilicone oil, epoxidized soybean oil, trioctyl trimellitate, and diisooctyl cyclohexane-1, 2-dicarboxylate.

8. A process for the preparation of a flame retardant nitrile rubber/lignin composite, characterized in that it comprises mixing the components of the flame retardant nitrile rubber composition according to any of claims 1 to 7 and vulcanizing the mix obtained after mixing; in the flame-retardant nitrile rubber composition, relative to 100 parts by weight of a nitrile rubber matrix, the using amount of lignin is 5-150 parts by weight, the using amount of an interface modifier is 0.5-50 parts by weight, the using amount of a softener is 2-35 parts by weight, the using amount of a flame retardant is 0.1-40 parts by weight, and the using amount of a vulcanization aid is 0.1-30 parts by weight.

9. The method according to claim 8, wherein the operations of mixing the components of the flame retardant nitrile rubber composition and vulcanizing the mixture obtained after mixing comprise:

(1) carrying out first mixing on each component in the component A to obtain a first mixed material, wherein the component A contains a nitrile rubber matrix, an interface modifier and lignin;

(2) carrying out second mixing on the first mixed material and each component in the component B to obtain a second mixed material, wherein the component B contains a softening agent and a flame retardant;

(3) performing third mixing on the second mixed material and each component in the component C, and then discharging to obtain a discharged rubber, wherein the component C contains a vulcanization aid;

(4) vulcanizing the discharged rubber, namely vulcanizing the discharged rubber,

preferably, the lignin is used in an amount of 10-100 parts by weight, the interfacial modifier is used in an amount of 1-40 parts by weight, the softener is used in an amount of 2-30 parts by weight, the flame retardant is used in an amount of 1-30 parts by weight, and the vulcanization aid is used in an amount of 2-15 parts by weight, relative to 100 parts by weight of the nitrile rubber matrix.

10. The method of claim 9, wherein in step (1), the conditions of the first mixing comprise: the temperature is 60-150 ℃, and the time is 6-60 min;

preferably, the first mixing is carried out in an internal mixer at a speed of 60 to 90rpm, preferably at a speed of 70 to 90 rpm.

11. The method of claim 9 or 10, wherein the conditions of the second mixing comprise: the temperature is 40-150 deg.C, and the time is 5-25 min;

preferably, the conditions of the third mixing include: the temperature is 0-100 deg.C, and the time is 5-20 min;

preferably, the conditions of the vulcanization include: the temperature is 150 ℃ and 200 ℃, the pressure is 10-20MPa, and the time is 10-40 min.

12. A flame retardant nitrile rubber/lignin composite material obtainable by the process according to any one of claims 8 to 11.

13. Use of the flame retardant nitrile rubber/lignin composite according to claim 12 in at least one of automotive hoses, printer rollers and foamed insulation.

Background

Nitrile-butadiene rubber (NBR) is a synthetic rubber prepared by copolymerizing butadiene and acrylonitrile emulsion, and is widely applied to the fields of automobiles, aerospace, petrochemical industry, textiles, wires and cables, printing, food packaging and the like by virtue of good oil resistance, hydrocarbon solvent resistance and thermal aging resistance. Its disadvantages are poor low-temp resistance, ozone resistance and poor anti-ultraviolet ageing performance.

In recent years, a great deal of research is carried out on blending and modification of NBR, so that the NBR can meet the application requirements of flame retardance, low temperature resistance, ozone aging resistance and the like under more severe environments.

Lignin is a renewable aromatic polymer with the greatest abundance in the nature, and mainly comes from byproducts of pulping and papermaking industries and lignin generated by biomass (wood/straw and the like) hydrolysis. Phenolic hydroxyl, carbonyl, ether bond, methoxyl, aldehyde group, carboxyl and the like in the molecular structure of the lignin endow the lignin with higher reaction activity, and the characteristic structures of benzene ring, phenolic hydroxyl and the like enable the lignin to have excellent ultraviolet radiation resistance and ageing resistance. The lignin is used for replacing carbon black to prepare the rubber/lignin composite material with excellent ultraviolet resistance and aging resistance, so that the cost of the rubber material can be reduced, and the method has important significance for promoting the effective utilization of biomass resources and the green development of high polymer materials. Meanwhile, the lignin has the important advantages of low density, little dust flying of carbon black in the mixing process and the like.

However, due to the special structure and properties of lignin, lignin molecules are extremely easy to agglomerate in a nitrile rubber/lignin blending system, so that the compatibility of the lignin and a rubber matrix is poor and the lignin is not easy to disperse.

Aiming at the defects of the NBR in heat, oxygen aging and ultraviolet resistance, the common solution is to add small-molecule antioxidants and light stabilizers such as hindered phenols and hindered amines, but the problems of migration, extraction, certain toxicity, environmental pollution and the like exist, and the lignin is expected to overcome as a compound containing a large amount of hindered phenol groups.

Although a large amount of research reports on the preparation of the composite material by blending lignin and rubber exist at home and abroad, most prepared composite materials have poor performance. Naskar and the like [ Green chem, 2016,18: 5423-5437 ] introduce a peroxide initiator in the high-temperature mixing process of NBR and lignin to form a certain chemical bond between the lignin and a rubber interface, and simultaneously add polyoxyethylene with ultrahigh molecular weight as a compatilizer, so that the tensile strength of the obtained composite material is improved, but the elongation at break is not improved or is even greatly reduced. Furthermore, the structure, molecular weight and distribution of lignin and acrylonitrile content of nitrile rubber must be strictly controlled.

In addition, the nitrile rubber has an oxygen index of 17-20, is a flammable polymer, and the defect limits the application range of the nitrile rubber. In the prior art, a method of adding a flame retardant is generally adopted to improve the flame retardance of the nitrile rubber, but the improvement of the flame retardance after the flame retardant is introduced is generally accompanied with the reduction of mechanical properties. Meanwhile, the requirement for halogen-free flame retardance prompts large-scale test and application of the novel flame retardant.

Therefore, how to further improve the interface compatibility between lignin and a rubber matrix is not limited by the lignin structure, the molecular weight and the like, and the effect of lignin on reinforcing and aging resistance of rubber is a hot spot of current research. Meanwhile, the nitrile rubber composite material with excellent flame retardant property and oil resistance is developed, and the method is of great importance for expanding the application range of the nitrile rubber material.

Disclosure of Invention

The invention aims to provide a flame-retardant nitrile rubber composition which has high strength and ageing resistance and can be used as a flame-retardant rubber material.

In order to achieve the above object, one aspect of the present invention provides a flame retardant nitrile rubber composition, which comprises the following components stored in admixture or separately:

nitrile butadiene rubber matrix, lignin, an interface modifier, a softener, a vulcanization assistant and a flame retardant,

the interface modifier is at least one of epoxidized hydroxyl-terminated polybutadiene rubber, epoxidized epoxy-terminated butadiene-acrylonitrile rubber and epoxidized carboxyl-terminated butadiene-acrylonitrile rubber, and the flame retardant is zinc phytate and/or calcium phytate;

relative to 100 parts by weight of the nitrile rubber matrix, the content of the lignin is 5-150 parts by weight, the content of the interface modifier is 0.5-50 parts by weight, the content of the softener is 2-35 parts by weight, the content of the flame retardant is 0.1-40 parts by weight, and the content of the vulcanization aid is 0.1-30 parts by weight.

The second aspect of the invention provides a method for preparing a flame-retardant nitrile rubber/lignin composite material, which comprises the steps of mixing the components in the flame-retardant nitrile rubber composition of the first aspect, and vulcanizing the mixed rubber obtained after mixing; in the flame-retardant nitrile rubber composition, relative to 100 parts by weight of a nitrile rubber matrix, the using amount of lignin is 5-150 parts by weight, the using amount of an interface modifier is 0.5-50 parts by weight, the using amount of a softener is 2-35 parts by weight, the using amount of a flame retardant is 0.1-40 parts by weight, and the using amount of a vulcanization aid is 0.1-30 parts by weight.

In a third aspect, the invention provides a flame retardant nitrile rubber/lignin composite material prepared by the method of the second aspect.

In a fourth aspect, the invention provides the use of the flame retardant nitrile rubber/lignin composite material of the third aspect in at least one of automotive hoses, printer rollers and foamed thermal insulation.

In the flame-retardant nitrile rubber composition provided by the invention, the composite material has better ultraviolet resistance and anti-aging performance by using the interface modifier and the specific lignin amount in combination with zinc phytate/calcium and other components as flame retardants; in the composition provided by the invention, all components have synergistic effect, so that the prepared nitrile rubber/lignin composite material has excellent comprehensive mechanical property.

Additional features and advantages of the invention will be described in detail in the detailed description which follows.

Detailed Description

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

In the case where it is not specifically mentioned, the Mooney viscosity according to the present invention is measured by preheating a large rotor of a Mooney viscometer at 100 ℃ for 1min and rotating it for 4 min.

As mentioned above, the first aspect of the present invention provides a flame retardant nitrile rubber composition, which comprises the following components stored in admixture or separately:

nitrile butadiene rubber matrix, lignin, an interface modifier, a softener, a vulcanization assistant and a flame retardant,

the interface modifier is at least one of epoxidized hydroxyl-terminated polybutadiene rubber, epoxidized epoxy-terminated butadiene-acrylonitrile rubber and epoxidized carboxyl-terminated butadiene-acrylonitrile rubber, and the flame retardant is zinc phytate and/or calcium phytate;

relative to 100 parts by weight of the nitrile rubber matrix, the content of the lignin is 5-150 parts by weight, the content of the interface modifier is 0.5-50 parts by weight, the content of the softener is 2-35 parts by weight, the content of the flame retardant is 0.1-40 parts by weight, and the content of the vulcanization aid is 0.1-30 parts by weight.

According to a preferred embodiment, the content of the lignin is 10 to 100 parts by weight, the content of the interfacial modifier is 1 to 40 parts by weight, the content of the softening agent is 2 to 30 parts by weight, the content of the flame retardant is 1 to 30 parts by weight, and the content of the vulcanization aid is 2 to 15 parts by weight, relative to 100 parts by weight of the nitrile rubber matrix. The inventor finds that under the preferable embodiment, the content of the composition of the invention is controlled, and the rest characteristics in the scheme are matched, so that the obtained composite material has obviously better comprehensive mechanical property and flame retardant property.

Preferably, the number average molecular weight of the interface modifier is 1000-5500, and the epoxy equivalent is 200-3000.

In the present invention, the epoxy equivalent is measured by the acetone hydrochloride method.

Preferably, the interfacial modifier is an epoxy-terminated nitrile rubber and/or an epoxidized carboxyl-terminated nitrile rubber, more preferably the content of acrylonitrile structural units in the epoxy-terminated nitrile rubber and the epoxidized carboxyl-terminated nitrile rubber are each independently 10 to 35 wt%.

Preferably, the acrylonitrile rubber matrix contains acrylonitrile structural units in an amount of 20 to 50 wt% and has a Mooney viscosity of 35 to 90.

Preferably, the lignin of the present invention has a phenolic hydroxyl group content of 3.0 wt% or more and a number average molecular weight of 2500-5500. More preferably, the lignin is at least one selected from the group consisting of organosolv lignin extracted from lignocellulosic material by organosolv, Kraft lignin extracted from Kraft pulp waste, enzymatic lignin extracted from fermentation ethanol, and alkali lignin obtained from alkaline pulping in paper making. Preferably, the lignin content in the organic solvent lignin, the enzymatic hydrolysis lignin and the alkali lignin is respectively and independently more than or equal to 70 wt%.

Preferably, the vulcanization aid comprises a crosslinking agent, and optionally further comprises a crosslinking aid.

Preferably, the cross-linking agent is selected from dicumyl peroxide, benzoyl peroxide, bis (2, 4-dichlorobenzoyl) peroxide, di-t-butyl peroxide, t-butyl perbenzoate, t-butylcumyl peroxide, methyl ethyl ketone peroxide, at least one of cumene hydroperoxide, 2, 5-dimethyl-2, 5-di (tert-butylperoxy) hexane, 2, 5-dimethyl-2, 5-di (benzoyl peroxide) hexane, 2, 5-dimethyl-2, 5-di (tert-butylperoxy) hexyne-3, 1-di-tert-butylperoxy-cyclohexane, 1-di-tert-butylperoxy-3, 3, 5-trimethylcyclohexane and 1, 3-bis (tert-butylperoxypropyl) benzene, and it is particularly preferred that the crosslinking agent is dicumyl peroxide.

Preferably, the crosslinking coagent is selected from at least one of triallyl isocyanurate, triallyl cyanurate, N' -m-phenylene-bismaleimide, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, methylene thiuram hexasulfide, zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc ethylphenyldithiocarbamate and sulfur, and particularly preferably the crosslinking coagent is triallyl isocyanurate.

According to a preferred embodiment of the present invention, the vulcanization aid is a crosslinking agent and a crosslinking aid, and the content weight ratio of the crosslinking agent to the crosslinking aid is 1: (0.5-2).

According to a more preferred embodiment of the present invention, the vulcanization aid is dicumyl peroxide (DCP) and triallyl isocyanurate (TAIC), and the weight ratio of the dicumyl peroxide to the triallyl isocyanurate is 1: (0.5-2). The inventor finds that under the preferable embodiment, the vulcanization auxiliary agent in the scheme of the invention is controlled to be matched with the rest characteristics in the scheme, so that the obtained composite material has obviously better comprehensive mechanical property and flame retardant property.

Preferably, the softening agent is selected from at least one of paraffin oil, naphthenic oil, hydroxy silicone oil, epoxidized soybean oil, trioctyl trimellitate, and diisooctyl cyclohexane-1, 2-dicarboxylate.

As mentioned above, a second aspect of the present invention provides a process for the preparation of a flame retardant nitrile rubber/lignin composite, which process comprises mixing the components of the flame retardant nitrile rubber composition according to the first aspect of the invention and vulcanizing the mix obtained after mixing; in the flame-retardant nitrile rubber composition, relative to 100 parts by weight of a nitrile rubber matrix, the using amount of lignin is 5-150 parts by weight, the using amount of an interface modifier is 0.5-50 parts by weight, the using amount of a softener is 2-35 parts by weight, the using amount of a flame retardant is 0.1-40 parts by weight, and the using amount of a vulcanization aid is 0.1-30 parts by weight.

According to a particularly preferred embodiment, the operation of mixing the components of the flame retardant nitrile rubber composition and curing the mix obtained after mixing comprises:

(1) carrying out first mixing on each component in the component A to obtain a first mixed material, wherein the component A contains a nitrile rubber matrix, an interface modifier and lignin;

(2) carrying out second mixing on the first mixed material and each component in the component B to obtain a second mixed material, wherein the component B contains a softening agent and a flame retardant;

(3) performing third mixing on the second mixed material and each component in the component C, and then discharging to obtain a discharged rubber, wherein the component C contains a vulcanization aid;

(4) and vulcanizing the discharged rubber.

In the method for preparing the flame-retardant nitrile rubber/lignin composite material according to the second aspect of the present invention, the components in the flame-retardant nitrile rubber composition according to the first aspect are used as raw materials, and therefore, in the method according to the second aspect of the present invention, in order to avoid repetition, the description of the types and properties of the components in the compositions is omitted, and a person skilled in the art should not be construed as limiting the present invention.

More preferably, the lignin is used in an amount of 10 to 100 parts by weight, the interfacial modifier is used in an amount of 1 to 40 parts by weight, the softener is used in an amount of 2 to 30 parts by weight, the flame retardant is used in an amount of 1 to 30 parts by weight, and the vulcanization aid is used in an amount of 2 to 15 parts by weight, based on 100 parts by weight of the nitrile rubber matrix.

According to the method of the second aspect of the present invention, preferably, in step (1), the conditions of the first mixing include: the temperature is 60-150 deg.C, and the time is 6-60 min.

Preferably, in step (1), the first mixing is performed in an internal mixer, and the rotation speed of the internal mixer is 60 to 90rpm, more preferably 70 to 90 rpm.

According to the method of the second aspect of the present invention, preferably, in the step (2), the conditions of the second mixing include: the temperature is 40-150 deg.C, and the time is 5-25 min.

According to the method of the second aspect of the present invention, preferably, in step (3), the conditions of the third mixing include: the temperature is 0-100 deg.C, and the time is 5-20 min.

According to the method of the second aspect of the present invention, preferably, in the step (4), the vulcanization conditions include: the temperature is 150 ℃ and 200 ℃, the pressure is 10-20MPa, and the time is 10-40 min.

The pressures used in the present invention are gauge pressures unless otherwise specified.

In the present invention, preferably, the vulcanization is carried out in a vulcanizer, preferably a press vulcanizer.

According to a preferred embodiment of the invention, the discharged gum is tableted, for example in a two-roll mill, before the discharged gum is subjected to the vulcanization, and the vulcanized discharged gum is left standing for 6 to 48 hours after the tableted discharged gum is tableted.

As mentioned above, a third aspect of the present invention provides a flame retardant nitrile rubber/lignin composite material prepared by the method of the second aspect.

As mentioned above, a fourth aspect of the present invention provides the use of the flame retardant nitrile rubber/lignin composite of the third aspect in at least one of automotive hoses, printer rollers and foamed insulation.

The present invention will be described in detail below by way of examples. In the following examples, various raw materials used are commercially available ones unless otherwise specified.

Lignin: enzymolysis lignin, which is in the form of powder, the lignin content is more than or equal to 80 wt%, the number average molecular weight is 3850, the phenolic hydroxyl content is more than or equal to 3.0 wt%, and the lignin is produced by Shandong Longli Biotech Co., Ltd; solvent lignin is selected from bamboo brown powder, the lignin content is more than or equal to 85 wt%, the number average molecular weight is 3719, the phenolic hydroxyl group content is more than or equal to 3.0 wt%, Guangzhou, cortex albiziae and Sancheng Biotech limited;

nitrile rubber matrix: JSR N220S, content of acrylonitrile structural unit 41 wt%, mooney viscosity 55; JSR N240S japan, the content of acrylonitrile structural units being 26% by weight, the mooney viscosity being 56;

an interface modifier: epoxidized hydroxyl-terminated polybutadiene rubber with a number average molecular weight of 3500 and an epoxy equivalent of 588, Zibozilong chemical Co., Ltd;

an interface modifier: epoxy-terminated nitrile rubber, acrylonitrile structural unit content of 25 weight percent, number average molecular weight of 3150, epoxy equivalent of 1600, Beijing DeWatt chemical technology Co., Ltd;

an interface modifier: the epoxidized terminal carboxyl nitrile rubber has the acrylonitrile structural unit content of 23 weight percent, the number average molecular weight of 3455, the epoxy equivalent weight of 2660, and is prepared by petrochemical division of Lanzhou petrochemical company in China;

softening agent: paraffin oil, a Beichen Square reagent factory, Tianjin, chemically pure; ASTM103# naphthenic oil, ningbo co-evolution chemical ltd, industrial grade;

flame retardant: zinc phytate, beijing huamaike biotechnology, llc, content 98 wt%, analytically pure; calcium phytate, Chongqing Pulico Biotechnology Co., Ltd., content 98 wt%, analytically pure;

and (3) a vulcanization assistant: a crosslinking agent, dicumyl peroxide (DCP), brand F-90, available from Achima chemical company; bis (2, 4-dichlorobenzoyl) peroxide (DCBP or bis-tetra), Hengda Industrial additives, Inc. of Laiwu;

and (3) a vulcanization assistant: crosslinking coagent, triallyl isocyanurate (TAIC): bailingwei Tech Co., Ltd., purity of 99% by weight.

The rubber processing and testing equipment conditions in the following examples and comparative examples are shown in table 1.

The test conditions for the vulcanizates prepared in the following examples and comparative examples are shown in Table 2.

The amounts of the components in the following examples and comparative examples are in parts by weight, and each part (i.e., each part by weight) represents 10 g.

TABLE 1

Note: the limiting oxygen index is the minimum oxygen concentration required for the material to undergo flamed combustion in an oxygen-nitrogen mixture gas flow under specified conditions. Expressed as a volume percent of oxygen in the resin. High oxygen index indicates that the material is not easy to burn, and the material is generally considered to be flammable material with the oxygen index less than 22, flammable material with the oxygen index between 22 and 27, and nonflammable material with the oxygen index more than 27.

TABLE 2

Example 1

The formulation of the flame retardant nitrile rubber composition is shown in Table 3.

The preparation process of the flame-retardant nitrile rubber/lignin composite material comprises the following steps:

(1) preheating an internal mixer to 100 ℃, sequentially adding a nitrile rubber matrix, lignin and an interface modifier into the internal mixer, and fully mixing and reacting for 30min (first mixing) to obtain a first mixed material;

(2) adding a softening agent and a flame retardant into the first mixed material, and continuously mixing for 20min (second mixing) to obtain a second mixed material;

(3) adding a cross-linking agent and a cross-linking auxiliary agent into the second mixed material at 90 ℃, continuously mixing for 10min (third mixing), and then discharging to obtain a discharged rubber;

(4) and continuously milling the discharged rubber from the internal mixer on a double-roll mill for 12min, discharging, standing for 24h, and finally putting into a flat vulcanizing machine for vulcanization to obtain the flame-retardant nitrile rubber/lignin composite material, which is recorded as S1.

Example 11

The formulation of the composition of this example is exactly the same as in example 1.

The preparation process of the vulcanized rubber is as follows:

adding a nitrile butadiene rubber matrix, lignin, an interface modifier, a softener and a flame retardant into an internal mixer for first mixing at the mixing temperature of 100 ℃ for 50min, discharging and standing for 4h to obtain a section of master batch;

sequentially adding the obtained primary rubber, the accelerator and the vulcanizing agent into an internal mixer for secondary mixing, wherein the mixing temperature is 90 ℃, the mixing time is 10min, and discharging to obtain final rubber;

and (3) putting the final rubber compound into a flat vulcanizing machine for vulcanization, wherein the vulcanization temperature is 160 ℃, the vulcanization pressure is 15MPa, and the vulcanization time is 30min, so that the flame-retardant nitrile rubber/lignin composite material is obtained and is marked as S11.

The remaining examples were carried out using the same procedure as in example 1, except that the rubber composition formulation and the process parameters were different, unless otherwise specified, as shown in Table 3.

Comparative examples were carried out using a similar procedure to example 1, except that the rubber compositions were formulated and the process parameters were different, see in particular table 3.

TABLE 3

Table 3 (continuation watch)

Table 3 (continuation watch)

	Example 5	Comparative example 1	Comparative example 2	Comparative example 3	Comparative example 4
						Nitrile rubber matrix
Species of	JSR N220S	JSR N220S	JSR N220S	JSR N220S	JSR N220S
						Dosage of	100 portions of	100 portions of	100 portions of	100 portions of	100 portions of
Lignin
						Species of	Enzymatic hydrolysis of lignin	/	Enzymatic hydrolysis of lignin	Enzymatic hydrolysis of lignin	Enzymatic hydrolysis of lignin
Dosage of	60 portions of	/	60 portions of	60 portions of	60 portions of
						Interface modifier
Species of	Epoxy-terminated nitrile rubber	Epoxy-terminated nitrile rubber	/	Epoxy-terminated nitrile rubber	Epoxy-terminated nitrile rubber
						Dosage of	15 portions of	15 portions of	/	15 portions of	15 portions of
Softening agent
						Species of	Paraffin oil	Paraffin oil	Paraffin oil	Paraffin oil	Paraffin oil
Dosage of	12 portions of	12 portions of	12 portions of	12 portions of	40 portions of
						Flame retardant
Species of	Zinc phytate	Zinc phytate	Zinc phytate	/	Zinc phytate
						Dosage of	16 portions of	16 portions of	16 portions of	/	16 portions of
Crosslinking agent
						Species of	DCP	DCP	DCP	DCP	DCP
Dosage of	2 portions of	2 portions of	2 portions of	2 portions of	2 portions of
						Crosslinking aid
Species of	TAIC	TAIC	TAIC	TAIC	TAIC
						Dosage of	1.5 parts of	1.5 parts of	1.5 parts of	1.5 parts of	1.5 parts of
First mixing
						Temperature of	95℃	95℃	95℃	95℃	95℃
Time	25min	25min	25min	25min	25min
						Second mixing
Temperature of	95℃	95℃	95℃	95℃	95℃
						Time	20min	20min	20min	25min	25min
Third mixing
						Temperature of	90℃	90℃	90℃	90℃	90℃
Time	10min	10min	10min	10min	10min
						Vulcanization
Temperature of	160℃	160℃	160℃	160℃	160℃
						Pressure of	15MPa	15MPa	15MPa	15MPa	15MPa
Time	32min	32min	32min	32min	32min
						Rubber nomenclature
	S5	CS1	CS2	CS3	CS4

Test example

Preparing dumbbell-type splines which accord with GB/T528-2009 standards from the products of the examples and the comparative examples, and testing tensile property data by using a tensile testing machine; a sample strip meeting the GB/T2406.2-2009 standard is prepared, and the flame retardant property is measured by using a full-automatic oxygen index tester, and the result is shown in Table 4.

TABLE 4

From the results in Table 4, it can be seen that zinc phytate or zinc phytate has a great influence on the limiting oxygen index and mechanical strength of nitrile rubber, and the addition of lignin and zinc/calcium phytate is very important for improving the flame retardancy and reinforcement of rubber materials. In comparison with example 5, it can be seen that the tensile strength and elongation at break of the sample are improved and the limiting oxygen index (flame retardancy) is increased after the lignin is added. Compared with the example 5, the comparative example 2 can show that the tensile strength and the elongation at break of the obtained composite material can be obviously improved by introducing the interface modifier, and the flame retardant properties of lignin and zinc/calcium phytate can be better exerted.

Compared with example 5, the comparative example 3 can show that the addition of the flame retardant zinc phytate not only improves the flame retardance, but also reinforces the rubber material to a certain extent through the epoxy-metal coordination effect. In the flame-retardant nitrile rubber composition provided by the invention, the prepared nitrile rubber/lignin composite material has excellent comprehensive mechanical properties through the synergistic effect of all the components.

The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.