KR102024891B1 - Preparation method nitrile butadiene rubber - Google Patents

Abstract

The present invention relates to a method for preparing nitrile-butadiene rubber, and more particularly, to dispersing and commercializing carbon black nitrile-butadiene rubber matrix by controlling the molecular weight of nitrile-butadiene rubber by separately adding alkyl thiol-based molecular weight regulator. It relates to a method for producing nitrile-butadiene rubber which can improve the properties, and at the same time improve the physical properties of the final rubber molded article obtained after the vulcanization process.

Description

Preparation method of nitrile-butadiene rubber {Preparation method nitrile butadiene rubber}

The present invention relates to a method for producing nitrile-butadiene rubber having high dispersibility to carbon black and improving physical properties.

Recently, as the domestic and overseas automobile and machinery industries have developed rapidly, the demand for rubber products that require oil resistance is continuously increasing.

Currently, most commonly used oil-resistant rubbers include nitrile butadiene rubber (NBR), epichlorohydrin rubber (ECO), and chlorinated rubber (CR).

Among them, nitrile-butadiene rubber is a rubber produced by copolymerizing acrylonitrile and butadiene by batch or continuous low temperature emulsion polymerization, and has a strong nitrile group and a solubility parameter of 9 or more for petroleum solvent. As it has solvent resistance, it is referred to as the most representative oil-resistant rubber.

In addition, nitrile-butadiene rubber has the advantages of good wear resistance and aging resistance, low gas permeability and strong cohesion, and excellent compatibility with vinyl chloride resin, nitrocellulose and phenol resin.

Nitrile-butadiene rubber is applied to all fields such as industrial machinery, construction machinery, chemical and chemical equipment, automobiles, aircraft, kitchenware, among others, oil-resistant hoses, belts, rollers, tank linings, adhesives, shoe soles, tubes, sealing articles. Or widely used in packing agents.

Meanwhile, synthetic rubber and natural rubber, including nitrile-butadiene rubber, are commercialized through a molding process through vulcanization (or vulcanization), and various rubber compounding agents are used to improve physical properties during the molding process. The compound for rubber is generally designed and mixed in various forms according to the type of rubber, purpose of use and environment, Typically, fillers are used.

Filler is not only reinforcing the physical properties of rubber materials but also increased by the combination of fillers which are lower in cost than raw rubber, thereby reducing the unit cost of rubber compound, improving processability, and improving mechanical strength such as dimensional stabilization, tensile strength, tear strength, abrasion resistance, etc. Use for the purpose of improvement.

Typical fillers include carbon blacks such as channel black, furnace black, thermal black, and acetylene black. However, carbon black has a strong interaction between particles and tends to form carbon black agglomerates when mixed with rubber, which results in poor dispersibility in the rubber matrix and low compatibility, leading to deterioration of physical properties of the final rubber molded product.

In order to increase the dispersibility of carbon black, an additive such as a compatibilizer or a dispersing agent is added or a technique of modifying the surface of the carbon black has been proposed.

Korean Patent Laid-Open Nos. 2006-0102202 and 2002-0019835 propose a method of adding a metal aliphatic organic acid salt to solve the problem of using a silica dispersant when carbon black is used as a rubber composition for tires. Doing.

In addition, the Republic of Korea Patent No. 10-0642205 discloses that it is possible to improve the interaction between the carbon black and rubber by introducing an acidic or basic functional group on the surface of the carbon black through chemical treatment.

These methods resulted in some improvement in the dispersibility of the carbon black in rubber, but the use of additional additives or chemical modifications resulted in higher costs.

Republic of Korea Patent Publication No. 2006-0102202, "Rubber composition for tires with improved dispersion" Republic of Korea Patent Publication No. 2002-0019835, "Dispersion improved rubber composition" Republic of Korea Patent No. 10-0642205, "Method for producing carbon black surface modified by chemical treatment"

Applicants have conducted various studies to increase the dispersibility of carbon black without the use of additional additives or chemical modifications. As a result, when a specific molecular weight modifier is separately added in the preparation of the nitrile-butadiene rubber latex, Nitrile-butadiene rubber having a low molecular weight and high Mooney viscosity was prepared, and the nitrile-butadiene rubber was mixed with carbon black to improve the dispersibility of the carbon black to the rubber as well as the properties of the processed rubber molded article. The present invention was completed by confirming this improvement.

Accordingly, it is an object of the present invention to provide a method for producing nitrile-butadiene rubber having improved physical properties and processability of rubber molded articles.

In order to achieve the above object, the present invention provides a method for preparing nitrile-butadiene rubber, characterized in that the production of nitrile-butadiene rubber by dividing the alkyl thiol-based molecular weight regulator.

 The divisional input is characterized in that the first injection before the polymerization, the second injection after 20% polymerization conversion rate.

In this case, the second split injection is completed before the polymerization conversion rate is 50%.

In addition, 50 to 80% by weight at the time of the first input in the content of 100% by weight of the total molecular weight regulator, characterized in that 20 to 50% by weight at the time of the second input.

At this time, the alkyl thiol-based molecular weight modifier is characterized in that the C8 to C18 linear or branched alkyl group-containing thiol compound.

According to the present invention, the molecular weight of the nitrile-butadiene rubber can be easily controlled through the divided input of the alkyl thiol-based molecular weight regulator.

These nitrile-butadiene rubbers not only improve the dispersibility to the nitrile-butadiene rubber matrix when using fillers such as carbon black, but also improve the processability in the processing process and the properties of the final manufactured rubber molded article.

The present invention provides a method for producing nitrile-butadiene rubber which enables the production of rubber molded articles having improved physical properties and processability.

In order to commercialize the nitrile-butadiene rubber, a molding process is performed, in which additives such as carbon black must be well mixed with the nitrile-butadiene rubber. The mixing is advantageous as the dispersibility of the carbon black in the rubber matrix is excellent. This dispersibility is related to the molecular weight and viscosity properties of the nitrile-butadiene rubber, the lower the molecular weight, the narrower the molecular weight distribution, and the lower the viscosity. In addition, the molecular weight and viscosity are related to the flowability of the rubber during processing, and the better the flowability, the better the processability.

For rubber, Mooney viscosity is used in relation to the viscosity. The Mooney viscosity is the viscosity of the unvulcanized rubber measured by the Mooney viscometer, using a large rotor at 100, and measuring and reading the value 4 minutes after the start of the rotor at 1 minute of preheating and displaying it as ML1 + 4 (100). The Mooney viscosity refers to the viscosity of the rubber defining the processing conditions of rubber such as mink dough, and is a measure of the flowability of rubber in the processing process. The value of the Mooney viscosity is closely related to the molecular weight of the rubber. In general, when the molecular weight of the rubber is high, physical properties are improved, but the Mooney viscosity is high, which is difficult in terms of processability during the production process of the rubber.

A parameter related to the Mooney viscosity is Mooney stress-relaxation rate (MSR).

In the present invention, by controlling the molecular weight of the polymer by changing the addition method of the molecular weight modifier, compared to the case where the conventional molecular weight modifier is added in a batch, while improving the flow properties by increasing the Mooney viscosity while lowering the molecular weight filler fillers and elastic properties It provides a method for preparing nitrile-butadiene rubber that can improve the.

Specifically, the present invention is characterized by dividing a molecular weight regulator in the production of nitrile-butadiene rubber using emulsion polymerization.

The molecular weight regulator is added to control the polymerization reaction rate, and is used for the purpose of controlling the chain extension of the polymer through polymerization.

When the molecular weight regulator is added, the molecular chain of the nitrile-butadiene rubber grows at a constant rate (ie, polymerization) by controlling the polymerization reaction rate, but as the reaction time passes, the rate is not constant. It has a molecular weight of

Thus, in the present invention, the molecular weight regulator is initially added to control the molecular weight of the rubber, and the rate of growth of the chain connected to the rubber is added through the second addition after 20% of the polymerization conversion rate in which the firstly charged molecular weight regulator is exhausted to some extent. Adjust again. The second input after the polymerization conversion rate of 20% is to ensure the desired level of molecular weight and molecular weight distribution, wherein if the molecular weight control agent is added before the polymerization conversion rate is 20%, the effect of the desired divided input is lowered and added too late. If this problem occurs because the reaction is terminated before the added molecular weight regulator participates in the reaction, the addition of the molecular weight regulator is to be completed after 50% by the polymerization conversion rate after 20%.

The molecular weight regulator to be added is used in an amount of 0.01 to 10 parts by weight, preferably 0.5 to 3 parts by weight, based on 100 parts by weight of the total monomers constituting the nitrile-butadiene rubber. In this case, it is more advantageous to control the molecular weight of the first and second doses of the molecular weight regulator to be added in the same amount or at an excessive amount during the first dose. Preferably, the first dose is added in an amount of 50 to 80% by weight of the total molecular weight regulator, and the remainder is added in an amount of 20 to 50% in the second dose.

The composition of the molecular weight regulator is also one of the important factors with regard to the preparation of nitrile-butadiene rubber with the split dosing.

As the molecular weight regulator in the present invention, an alkyl thiol-based molecular weight regulator is used.

The alkyl thiol may be a C8-C18 linear or branched alkyl group-containing thiol compound. Preferably, linear alkyl group-containing thiol compounds of C8 to C14 or branched alkyl group-containing thiol compounds of C12 to C18 are possible.

The linear alkyl group-containing thiol compound may be one selected from the group consisting of n-octyl mercaptan, n-dodecyl mercaptan, n-decyl mercaptan, t-dodecyl mercaptan, and combinations thereof.

In addition, the branched alkyl group-containing towel compound refers to a compound having a structure in which 3 to 5 tertiary carbons are present in the molecular structure, wherein a thiol (SH) group is connected to the tertiary carbon. For example, in the group consisting of 2,2,4,6,6-pentamethylheptan-4-thiol, 2,2,4,6,6,8,8-heptamethylnonan-4-thiol and combinations thereof One selected is possible and preferably 2,2,4,6,6-pentamethylheptan-4-thiol is used.

A method for preparing nitrile-butadiene rubber incorporating a split injection method of the alkyl thiol-based molecular weight regulator as described above will be described in more detail below.

First, a monomer, an emulsifier, a polymerization initiator, an alkyl thiol molecular weight regulator and deionized water are added to the polymerization reactor.

In the present invention, the monomer for preparing nitrile-butadiene rubber is composed of a vinyl cyanide monomer and a conjugated diene monomer.

The vinyl cyanide monomer may be one selected from the group consisting of acrylonitrile, methacrylonitrile, fumaronitrile, α-chloronitrile, α-cyanoethyl acrylonitrile and combinations thereof, and preferably acrylonitrile Use

Such vinyl cyanated monomers comprise 15 to 50% by weight, preferably 20 to 45% by weight, more preferably 25 to 40% by weight of the total monomers constituting the nitrile-butadiene rubber. If the content is less than the above range, not only the oil resistance of the rubber molded article is lowered, but also the tensile strength is lowered. On the contrary, if the content exceeds the above range, the rubber molded article becomes hard and the wearability is poor.

The conjugated diene monomer is selected from the group consisting of 1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 1,3-pentadiene, isoprene, and combinations thereof 1 type is possible and, preferably, 1, 3- butadiene is used.

The conjugated diene monomer is 50 to 85% by weight, preferably 45 to 80% by weight, more preferably 50 to 75% by weight of the total monomer constituting the carboxylic acid-modified nitrile copolymer. If the content is less than the above range, the rubber molded article becomes hard and the wear feeling worsens. On the contrary, if the content exceeds the above range, the oil resistance of the rubber molded article deteriorates and the tensile strength decreases.

In the method of adding the monomer mixture constituting the nitrile-butadiene rubber, a method of introducing the monomer mixture into the polymerization reactor at once, a method of continuously introducing the monomer mixture into the polymerization reactor, a part of the monomer mixture into the polymerization reactor, and the remaining monomers Any method of continuously supplying to the polymerization reactor may be used.

In the production of this nitrile-butadiene rubber, an aliphatic organic acid is used as an emulsifier.

The aliphatic organic acid may be, for example, an aliphatic organic acid having 12 to 18 carbon atoms, or an aliphatic organic acid having 14 to 18 carbon atoms or 16 to 18 carbon atoms.

Specific examples include oleic acid, rosin acid, lauric acid, myristic acid, palmitic acid, stearic acid, naphthalene sulfonic acid And eicosanoic acid may be used.

The emulsifier is used in the nitrile-butadiene rubber is 0.5 to 10 parts by weight, preferably 0.8 to 8 parts by weight, more preferably 1.5 to 5 parts by weight of aliphatic organic acid based on 100 parts by weight of nitrile-butadiene rubber. If the content is less than the above range, the stability during polymerization is lowered. On the contrary, if the content exceeds the above range, foaming increases.

Although it does not specifically limit as a polymerization initiator, A radical initiator can be used. As said radical initiator, Inorganic peroxides, such as sodium persulfate, potassium persulfate, ammonium persulfate, potassium perphosphate, hydrogen peroxide; t-butyl peroxide, cumene hydroperoxide, p-mentanehydro peroxide, di-t-butyl peroxide, t-butylcumyl peroxide, acetyl peroxide, isobutyl peroxide, octanoyl peroxide, dibenzoyl peroxide Organic peroxides such as oxides, 3,5,5-trimethylhexanol peroxide and t-butyl peroxy isobutylate; At least one selected from the group consisting of azobis isobutyronitrile, azobis-2,4-dimethylvaleronitrile, azobiscyclohexane carbonitrile, and azobis isobutyric acid (butyl acid) methyl, and among these radical initiators Inorganic peroxide is more preferable, and persulfate can be used preferably.

The amount of the polymerization initiator used is 0.01 to 2 parts by weight, preferably 0.02 to 1.5 parts by weight based on 100 parts by weight of the total monomers constituting the nitrile-butadiene rubber. If the content is less than the above range, the polymerization rate is lowered, making it difficult to manufacture the final product. On the contrary, if the content exceeds the above range, the polymerization rate is too fast to control the polymerization.

The composition and content of the alkyl thiol-based molecular weight modifier are as described above.

At this time, in addition to the above composition, if necessary, an additive such as an activator, a chelating agent, a dispersant, a pH adjusting agent, an oxygen scavenger, a particle size adjusting agent, an anti-aging agent, an oxygen scavenger, and the like can be added.

Next, the emulsion polymerization is carried out, and the second alkyl thiol-based molecular weight regulator is added at a polymerization conversion rate of 20% or more, and the addition is completed within 50%.

In the emulsion polymerization, the polymerization temperature may be 10 to 90 ° C, preferably 20 to 80 ° C, more preferably 25 to 75 ° C, but is not particularly limited thereto. In the above temperature range, the time required for reaching the polymerization conversion rate of 80% may be performed to be 7 to 8 hours.

The second input of the alkyl thiol-based molecular weight regulator may be a batch or a continuous method.

Next, the polymerization is completed to prepare nitrile-butadiene rubber latex.

The completion of the polymerization usually terminates the polymerization at a polymerization conversion rate of 80% to obtain nitrile-butadiene rubber in latex form.

The nitrile-butadiene rubber latex is subjected to conventional post-treatment procedures such as coagulation and washing to obtain nitrile-butadiene rubber.

Coagulation is carried out through the addition of coagulants, wherein coagulants are such as barium chloride, calcium chloride, magnesium chloride, zinc chloride and aluminum chloride; metal chlorides; Nitrates such as barium nitrate, calcium nitrate and zinc nitrate; Acetates such as barium acetate, calcium acetate and zinc acetate; Sulfates such as calcium sulfate, magnesium sulfate, and aluminum sulfate. Of these, calcium chloride and magnesium sulfate are preferred. The coagulation may be coagulation at 50 to 100 ° C., and coagulation agent may be 5 wt% or less based on the total amount of the total salt used for coagulation.

The washing can be carried out at 50 to 90 through the use of distilled water or the like.

According to the invention, the nitrile-butadiene rubbers obtained according to the process described above have a Mooney viscosity (ML (1 + 4 @ 100)) of 30 to 150 Mooney units.

The nitrile-butadiene rubber prepared according to the present invention exhibits excellent oil resistance, abrasion resistance, and aging resistance, and can be applied to various products by performing a molding process under a vulcanization reaction.

Molding of the nitrile-butadiene rubber is not particularly limited in the present invention, and follows the method known in the art. In one example, the nitrile-butadiene rubber is kneaded by adding a vulcanizing agent, a vulcanizing accelerator, and various additives, and then molded into a predetermined shape through a molding process under a vulcanization reaction.

Sulfur is used as a vulcanizing agent, and peroxide-based compounds may be used in addition, but sulfur crosslinking systems are generally used.

The vulcanization accelerator serves to improve the vulcanization efficiency and reaction rate by allowing the vulcanization reaction to occur uniformly at the rubber reaction site. The vulcanizing accelerator may be at least one selected from the group consisting of thiazole-based, thiuram-based, thiourea-based, guanine-based and thiocarbamate-based activators. have. Specific examples of the thiazole type include N-t-butyl-2-benzothiazole sulfenamide (TBBS).

At this time, the additives may be fillers, heat stabilizers (antiaging agents, antioxidants, rubber stabilizers), ozone blockers, processing aids, extender oils, plasticizers, antifoaming agents, softeners, flame retardants, antistatic agents, retardants, release agents and the like.

In particular, when nitrile-butadiene rubber uses carbon black as a filler, the carbon black is uniformly dispersed in the rubber to improve physical properties of the final rubber molded product.

The use of carbon black increases the rubber compounding cost, lowers the cost of rubber compounding, improves processability, and improves mechanical strength such as dimensional stabilization, tensile strength, tear strength, and abrasion resistance. Carbon black that can be used is not limited in the present invention as long as it is used in the general rubber related art, channel black, furnace black, thermal black, acetylene black and the like.

The anti-aging agent serves to prevent the aging of the double bonds present in the nitrile butadiene-based rubber, but is not particularly limited as long as it is used for kneading of the rubber, it is preferable to use an amine-based or phenol-based antioxidant.

The zinc oxide (ZnO) forms a complex during processing with stearic acid to serve as a vulcanization promoter. In this case, stearic acid not only facilitates rubber processing as a processing aid, but also forms a complex with zinc oxide (ZnO) to serve as a vulcanization promoter.

In addition, metal soap is used as a processing aid and a vulcanization accelerator, and sodium stearate, potassium stearate, and the like may be used as an example.

The rubber molded article produced in the present invention has a tensile strength in the range of 200 to 300 kgf / cm ² , elongation in the range of 400 to 500%, 300% modulus in the range of 120 to 200, wherein the tensile strength, elongation, 300% modulus may be measured on vulcanizates according to DIN 53 504.

Accordingly, the rubber molded article is applied to all fields such as industrial machinery, construction machinery, chemical equipment, automobiles, aircraft, kitchen appliances, and the like, among them, seals, caps, hoses or diaphragms, O-ring seals, flat seals, and wrinkles. Type sealing ring, sealing sleeve, sealing cap, dust blocking cap, plug sealing, insulation hose, oil cooler hose, intake hose, servo control hose, pump diaphragm, belt, rubber roller, foam insulation, tank lining, adhesive, It is preferably applicable to shoe soles, tubes and the like.

Hereinafter, preferred examples are provided to help the understanding of the present invention, but the following examples are merely for exemplifying the present invention, and various changes and modifications within the scope and spirit of the present invention are apparent to those skilled in the art. It goes without saying that changes and modifications belong to the appended claims.

EXAMPLE

Example 1 Preparation of Nitrile-Butadiene Rubber and Rubber Molded Article

(1) Preparation of Nitrile-Butadiene Rubber

72 parts by weight of 1,4-butadiene and 19 parts by weight of acrylonitrile were added to the reaction vessel, and 3 parts by weight of an aliphatic organic acid (Fatty acid (Company: LG Life Health Co., Ltd., product name: elofad TP 200) based on 100 parts by weight of the monomer). 0.3 weight part of molecular weight regulator 2,2,4,6,6-pentamethylheptan-4-thiol, and 200 weight part of water were added, and emulsion polymerization was advanced.

Then, when the polymerization conversion reached 50%, 0.2 parts by weight of the molecular weight regulator and 9 parts by weight of acrylonitrile were further added.

After the polymerization was continued, the reaction was terminated when the polymerization conversion rate reached 80%, and the reaction time was 7 hours.

2 parts by weight of calcium chloride was added to 100 parts by weight (solid content) of the obtained nitrile-butadiene rubber latex, heated to 70 ° C., aged for 20 minutes, cooled to obtain a coagulated product, and washed with ion exchanged water 2 to 3 times to remove residual monomer. Then it was dehydrated using a filter. It was then dried using a roll dryer to produce nitrile-butadiene rubber.

(2) Preparation of Nitrile-Butadiene Rubber Molded Article

140 parts by weight of nitrile-butadiene rubber coagulum prepared above, 56 parts by weight of carbon black, 4.2 parts by weight of ZnO, 1.4 parts by weight of stearic acid, Nt-butyl-2-benzothiazole sulfenamide : TBBS) 0.98 parts by weight, and 2.1 parts by weight of sulfur were kneaded at 50 ° C. and 50 rpm conditions for 8 minutes using a Haake mixer, followed by a roll mill at 50 ° C. for 2 minutes, and 50 minutes at 150 ° C. The specimen was prepared by pressing.

Example 2 Preparation of Nitrile-Butadiene Rubber and Rubber Molded Article

(1) Preparation of Nitrile-Butadiene Rubber

66 parts by weight of 1,4-butadiene and 34 parts by weight of acrylonitrile were added to the reaction vessel, and 3 parts by weight of an aliphatic organic acid (Fatty acid (company name: LG Life Health Co., Ltd., product name: elofad TP 200)) based on 100 parts by weight of the monomer. 0.3 weight part of t-dodecyl mercaptan and 200 weight part of water were added as a molecular weight modifier, and emulsion polymerization was performed.

Then, when the polymerization conversion rate reached 50%, 0.2 parts by weight of the molecular weight regulator was further added.

After the polymerization was continued, the reaction was terminated when the polymerization conversion rate reached 80%, and the reaction time was 7 hours.

2 parts by weight of magnesium sulfate was added to 100 parts by weight (solid content) of the obtained nitrile-butadiene rubber latex, and heated to 70 ° C., aged for 20 minutes, and cooled to obtain a coagulum. The remaining monomers were washed 2 to 3 times with ion exchanged water. After removal, it was dehydrated using a filter. It was then dried using a roll dryer to produce nitrile-butadiene rubber.

(2) Preparation of Nitrile-Butadiene Rubber Molded Article

140 parts by weight of nitrile-butadiene rubber coagulum prepared above, 56 parts by weight of carbon black, 4.2 parts by weight of ZnO, 1.4 parts by weight of stearic acid, Nt-butyl-2-benzothiazole sulfenamide : TBBS) 0.98 parts by weight, and 2.1 parts by weight of sulfur were kneaded at 50 ° C. and 50 rpm conditions for 8 minutes using a Haake mixer, followed by a roll mill at 50 ° C. for 2 minutes, and 50 minutes at 150 ° C. The specimen was prepared by pressing.

Comparative Example 1: Preparation of Nitrile-Butadiene Rubber and Rubber Molded Article

(1) Preparation of Nitrile-Butadiene Rubber

72 parts by weight of 1,4-butadiene and 19 parts by weight of acrylonitrile were added to the reaction vessel, and 3 parts by weight of an aliphatic organic acid (Fatty acid (Company: LG Life Health Co., Ltd., product name: elofad TP 200) based on 100 parts by weight of the monomer). , 0.5 weight part of molecular weight regulator 2,2,4,6,6-pentamethylheptan-4-thiol, and 200 weight part of water were added, and emulsion polymerization was advanced.

Then, when the polymerization conversion reached 50%, 9 parts by weight of acrylonitrile was further added.

After the polymerization was continued, the reaction was terminated when the polymerization conversion rate reached 80%, and the reaction time was 7 hours.

2 parts by weight of calcium chloride was added to 100 parts by weight (solid content) of the obtained nitrile-butadiene rubber latex, heated to 70 ° C., aged for 20 minutes, cooled to obtain a coagulated product, and washed with ion exchanged water 2 to 3 times to remove residual monomer. Then it was dehydrated using a filter. It was then dried using a roll dryer to produce nitrile-butadiene rubber.

(2) Preparation of Nitrile-Butadiene Rubber Molded Article

140 parts by weight of nitrile-butadiene rubber coagulum prepared above, 56 parts by weight of carbon black, 4.2 parts by weight of ZnO, 1.4 parts by weight of stearic acid, Nt-butyl-2-benzothiazole sulfenamide : TBBS) 0.98 parts by weight, and 2.1 parts by weight of sulfur were kneaded at 50 ° C. and 50 rpm conditions for 8 minutes using a Haake mixer, followed by a roll mill at 50 ° C. for 2 minutes, and 50 minutes at 150 ° C. The specimen was prepared by pressing.

Comparative Example 2: Preparation of Nitrile-Butadiene Rubber and Rubber Molded Article

(1) Preparation of Nitrile-Butadiene Rubber

66 parts by weight of 1,4-butadiene and 34 parts by weight of acrylonitrile were added to the reaction vessel, and an aliphatic organic acid (Fatty acid (Company: LG Life Health Co., Ltd., product name: elofad TP 200)) was used as an emulsifier based on 100 parts by weight of monomer. Emulsion polymerization was carried out by adding 3 parts by weight of the mixture of rosin acid, 0.5 part by weight of t-dodecyl mercaptan and 200 parts by weight of water as the molecular weight regulator.

After the polymerization was continued, the reaction was terminated when the polymerization conversion rate reached 80%, and the reaction time was 7 hours.

2 parts by weight of magnesium sulfate was added to 100 parts by weight of the obtained nitrile-butadiene rubber coagulum (solid content), and the mixture was heated to 70 ° C., aged for 20 minutes, cooled to obtain a coagulum, and washed 2 to 3 times with ion-exchanged water. After removal, it was dehydrated using a filter. It was then dried using a roll dryer to produce nitrile-butadiene rubber.

(2) Preparation of Nitrile-Butadiene Rubber Molded Article

140 parts by weight of nitrile-butadiene rubber coagulum prepared above, 56 parts by weight of carbon black, 4.2 parts by weight of ZnO, 1.4 parts by weight of stearic acid, Nt-butyl-2-benzothiazole sulfenamide : TBBS) 0.98 parts by weight, and 2.1 parts by weight of sulfur were kneaded at 50 ° C. and 50 rpm conditions for 8 minutes using a Haake mixer, followed by a roll mill at 50 ° C. for 2 minutes, and 50 minutes at 150 ° C. The specimen was prepared by pressing.

Experimental Example 1: Analysis of Nitrile-Butadiene Rubber and Physical Properties of Rubber Molded Article

(1) Nitrile-Butadiene Rubber Characterization

The physical properties of the nitrile-butadiene rubber molded article prepared in Examples and Comparative Examples were evaluated as follows, and the results are shown in Table 1. The physical property measurement of each item was performed as follows.

Molecular weight: The nitrile-butadiene rubber coagulum was stirred in DMF at 0.1% by weight for 24 hours, and then the number average molecular weight (Mn) and the weight average molecular weight (Mw) were measured by gel permeation chromatography (GPC). .

Polydispersity Index (PDI): The ratio of Mw / Mn was calculated.

MV (mooney viscosity): measured according to DIN 53523/3.

Mooney stress-relaxation rate (MSR): measured at 100 ° C. using a shear disc viscometer according to ISO 289-4: 2003E. The higher the MSR value, the lower the long chain branching fraction.

(2) Physical property analysis of nitrile-butadiene rubber molded article

The physical properties of the nitrile-butadiene rubber prepared in Examples and Comparative Examples were evaluated as follows, and the results are shown in Table 1. The physical property measurement of each item was performed as follows.

(2-1) Vulcanization characteristics: MDR2000E, 170 ℃, 30 minutes

ML, MH: Min / max torque values were measured respectively.

Ts1: The time required until 1% vulcanization was measured.

Tc'90: Measured with 90% cure time, which means the vulcanization rate.

(2-2) Mechanical Properties

Tensile strength (kg / cm ² ), elongation (%), 300% modulus: It was performed according to Korean Industrial Standard KSM 6518 2-4.

Example 1 Example 2 Comparative Example 1 Comparative Example 2 Monomer
(Parts by weight) 1.4-butadiene 72 66 72 66 Acrylonitrile 28 ^* 34 28 ^* 34 Emulsifier
(Parts by weight) Aliphatic organic acid 3 - 3 Aliphatic Organic Acid + Rosin Acid - 3 - 3 Molecular weight regulator
(Parts by weight) PMHT ¹⁾ Primary 0.3 - 0.5 - Secondary 0.2 - - - TDDM ²⁾ Primary - 0.3 - 0.5 Secondary - 0.2 - - coagulant CaCl ₂ MgSO ₄ CaCl ₂ MgSO ₄ Molecular Weight Characteristics Number average molecular weight (Mn) 6.64 x 10 ⁴ 7.56 x 10 ⁴ 7.08 x 10 ⁴ 9.36 x 10 ⁴ Weight average molecular weight (Mw) 4.18 x 10 ⁵ 5.46 x 10 ⁵ 3.41 x 10 ⁵ 4.78 x 10 ⁵ Polydispersity (PDI) 6.30 7.22 4.81 5.11 Viscosity characteristics Mooney Viscosity (MV, ML1 + 4 (100) 44.8 75.2 43.4 77.5 Mooney Stress Relief Rate (MSR) 0.418 0.359 0.477 0.371 Vulcanization Characteristics Torque (MH-ML, kgf / cm) 12.3 12.46 12.5 14.61 Curing time (Ts'1, min) 1.05 0.89 1.07 1.02 Curing time (Tc'90, min) 2.50 7.65 2.59 7.64 Mechanical properties Tensile Strength (kg / cm ² ) 251.3 294.6 242.7 251.3 % Elongation 450.9 425.2 469.8 444.9 300% Modulus (Pa) 148.5 184.7 134.7 168.8 *: Split injection
1) PMHT: 2,2,4,6,6-pentamethylheptan-4-thiol
2) TDDM: t-dodecyl mercaptan

Referring to Table 1, it can be seen that the rubber of Example 1 in which the molecular weight modifier is separately added according to the present invention, compared to the rubber of Comparative Example 1 of the same composition, has a high Mooney viscosity and a low molecular weight. In addition, it can be seen that the mechanical properties are also excellent as a result of comparing vulcanization characteristics and mechanical properties after mixing with carbon black.

These results showed the same tendency in Example 2 and Comparative Example 2 using other molecular weight modifiers.

Accordingly, it can be seen that the divided injection of the molecular weight modifier as in the present invention improves the dispersibility with carbon black, improves the workability and also improves the physical properties of the final rubber molded product.

The method for producing nitrile-butadiene rubber according to the present invention can be applied to all fields, such as industrial machinery, construction machinery, chemical and chemical equipment, automobiles, aircraft, kitchen appliances, etc., in which rubber products are required.

Claims (10)

(a) emulsion polymerizing a vinyl cyanide compound and 1,4-butadiene to prepare a nitrile-butadiene rubber; And
(b) kneading the nitrile-butadiene rubber prepared above with carbon black; a method for producing a nitrile-butadiene rubber molded article, including
Step (a) is 2,2,4,6,6-pentamethylheptan-4-thiol, 2,2,4,6,6,8,8-heptamethylnonan-4-thiol and combinations thereof Including 50 to 80% by weight of the first one or more alkyl thiol-based molecular weight regulator selected from the group consisting of before the polymerization, and 20 to 50% by weight after the polymerization conversion rate of 20% A method for producing a nitrile-butadiene rubber molded article. delete delete The method of claim 1,
The alkyl thiol-based molecular weight regulator is a method for producing a nitrile-butadiene rubber molded article, characterized in that it is used in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the total monomers constituting the nitrile-butadiene rubber. delete delete delete delete The method of claim 1,
The vinyl cyanide compound is characterized in that it comprises one selected from the group consisting of acrylonitrile, methacrylonitrile, fumaronitrile, α-chloronitrile, α-cyanoethyl acrylonitrile, and combinations thereof. Method for producing nitrile-butadiene rubber molded article.
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