RU2497831C1 - Method of extracting butadiene-styrene rubber from latex - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to petrochemical industry, particularly production of butadiene-styrene rubber obtained by emulsion (co)polymerisation. The method of extracting butadiene-styrene rubber from latex by coagulation using a combined coagulating agent containing poly-N,N-dimethyl-N,N-diallylammonium chloride (PDMDAAC) and fibre material, with the following weight ratio of components, with respect to dry substance: fibre material:PDMDAAC=1:(0.020-1.2), followed by acidation of serum with a mineral acid, separating and drying the rubber crumbs. The fibre material used can be material made of natural, artificial and synthetic fibres.

EFFECT: invention provides complete coagulation of latex while reducing consumption of poly-N,N-dimethyl-N,N-diallylammonium chloride and without introducing mineral salts into the system, and also enables to obtain a product with improved physical and mechanical properties.

2 cl, 2 tbl

Description

The invention relates to the petrochemical industry, in particular to the production of styrene-butadiene rubbers obtained by emulsion (co) polymerization, and can be used to isolate rubbers from latexes.

Due to the fact that the traditionally used industrial methods for the isolation of styrene-butadiene rubbers from latexes involve the use of large quantities of sodium chloride or other inorganic salts, as well as mineral acids that enter water bodies together with waste water, it is relevant to search for more environmentally friendly methods to reduce harmful environmental pressure on the environment.

The basis of these methods is the use of organic coagulants (flocculants), in particular synthetic high molecular weight cationic polyelectrolytes, among which the quaternary ammonium polymer salt poly-N, N-dimethyl-N, N-diallylammonium chloride (PDMDAAH) attracts special attention.

A known method for the allocation of oil-filled butadiene- (α-methyl) -styrene rubber [RU 2067590 C1, publ. 10.10.1996], in which a suspension of the reagent in mineral oil containing PDMDAAH in an amount providing a dosage of 0.5 ÷ 1.5 kg / t of rubber is used as a coagulating agent, then an aqueous solution of sodium chloride in an amount of 20 ÷ 50 kg / is introduced t of rubber per dry matter, then serum acidified with sulfuric acid is introduced to create a pH of 4.5–5.5, followed by the introduction of an aqueous solution of mineral acid to create a pH of 3.5–4.5 and isolation of rubber crumbs. The method allows to achieve a uniform distribution of oil in the rubber and to obtain a loose crumb of rubber, to reduce the consumption of sodium chloride, however, it does not allow to completely abandon it.

A known method for the isolation of butadiene- (α-methyl) -styrene rubber [RU 2067592 C1, publ. 10.10.1996] by coagulation of rubber latex in an acidic environment using a solution of PDMDAAH in acidified serum as a coagulating additive. Coagulation is carried out in two or three stages with fractional administration of the coagulant. According to the authors, for rubber SKS-30 ARK, regardless of the number of stages, the consumption of PDMDAAH is 1.7 kg / t of rubber. However, it should be noted that, according to the data cited in [Nikulin S.S., Verezhnikov V.N., Poyarkova T.N., Vostrikova G.Yu. “The effect of the concentration of the dispersed phase on the patterns of rubber release from latex” Journal of Applied Chemistry, vol. 73, Issue 10, 2000, S.1720-1724], the consumption of this coagulant for the isolation of rubber SKS-30 ARC is from 3 to 5 kg / t rubber. Such discrepancies, apparently, are associated with the fact that the required amount of coagulant strongly depends on the quantitative content and qualitative composition of the surfactants present in the system. The disadvantage of this method is the multi-stage process, as well as the difficulty of accurately dosing the coagulant in real industrial conditions.

A known method for the allocation of oil-filled butadiene- (α-methyl) -styrene rubber [RU 2064939 C1, publ. 08/10/1996], in which a mixture of sodium chloride and the product of the interaction of protein (glue glue, proteinosin) with PDMDAAH is used as a coagulating agent in the following mass ratio of components based on dry matter (wt.%):

Sodium chloride - 83 ÷ 97

Protein - 2.8 ÷ 12.0

PDMDAAH - 0.2 ÷ 5.0.

The method allows to reduce the required amount of sulfuric acid from 18 to 12 kg / t of rubber, to reduce the consumption of table salt for coagulation, however, it does not completely abandon its use.

Closest to the proposed method is a method for the isolation of butadiene- (α-methyl) -styrene rubber [RU 2063980 C1, publ. 07/20/1996] using a combined coagulant and mineral acid, in which the product of the interaction of a protein (skin glue, proteincosine) with PDMDAAH is used as a combined coagulant with a protein: PDMDAAX weight ratio, calculated on a dry substance of 1: (0.1 ÷ 1,0). The method improves the quality of the resulting rubber crumb, improves the strength characteristics of the rubber, allows, in the case of rubber SKS-30 ARC, to reduce the consumption of coagulating agent to 2.1 ÷ 2.3 kg / t of rubber, depending on the type of protein component. The disadvantage of this method is that during storage and use the protein components that make up the coagulants undergo microbiological decomposition and give the reaction masses a sharp unpleasant odor, creating difficulties in the implementation of the process. The presence of PDMDAAH in coagulating mixtures prepared immediately before use slows down the process of microbiological decomposition of protein components, however, when protein solutions are stored as raw materials in industrial tanks, they decompose, especially in the summer. This leads to a violation of the ratio of protein: PDMDAAH in the composition of the combined coagulating agent, destabilizes the process and leads to the loss of rubber and components of the emulsion system with serum and wash water and requires a change in the consumption rates necessary for the complete release of rubber from latex.

The problem to which this invention is directed, is to provide a method for the isolation of styrene-butadiene rubber from latex, which provides complete coagulation of the latex while reducing the consumption of poly-N, N-dimethyl-N, N-diallylammonium chloride and without introduction into the system mineral salts, eliminating the problems associated with the use of protein fillers, and at the same time providing a product with improved physical and mechanical properties.

The problem is solved by the proposed method for the isolation of styrene-butadiene rubber by coagulation of rubber latex using a combined coagulant containing poly-N, N-dimethyl-N, N-diallylammonium chloride, followed by acidification of serum with mineral acid, separation and drying of rubber crumbs, characterized in that the combined coagulating agent additionally contains fibrous material in the following mass ratio of components: fibrous material: PDMDAAX = 1: (0.020 ÷ 1.2).

The possibility of using in rubbers as fillers of fibrous materials of various origin has recently been of great interest. It is known that the introduction of fibrous materials into rubber mixtures improves the resistance of vulcanizates to thermo-oxidative effects, to repeated deformations, etc. [Perepelkin K.E. Reinforcing fibers and fibrous polymer composites. SPb. Because of NOT, 2009, 380 pp.]. The use of fiber-containing composite fillers in rubbers allows us to solve the problem of waste disposal of textile, clothing and other industries, the volumes of which are tens of thousands of tons per year.

The introduction of fibrous fillers in rubbers is associated with technological problems, for example, the introduction of rollers on the rollers during the preparation of rubber compounds does not allow to achieve uniform distribution of the filler in the volume of material [Kornev A.E., Bukanov A.M., Sheverdyaev ON Technology of elastomeric materials. M .: NPPA "Istok", 2009, 504 pp.], Which negatively affects the physical and mechanical properties of vulcanizates. The search for methods to achieve uniform distribution of the fibrous filler in the volume of the polymer matrix, led to the creation of a series of inventions protected by patents [RU 2289590 C1, publ. 12.20.2006, RU 2291157 C1, publ. 01/10/2007, RU 2291158 C1, publ. 01/10/2007, RU 2291159 C1, publ. 01/10/2007, RU 2291160 C1, publ. 01/10/2007, RU 2291161 C1, publ. January 10, 2007], in which the general approach was used, in which the filler was introduced into latex as part of a fiber-polymer antioxidant composite at the stage preceding coagulation, and a 24% sodium chloride solution was used as a coagulant. At the same time, the technical characteristics of the product are improved, but the problem of wastewater quality remains unresolved.

In the proposed method, the fibrous material (filler) is introduced into the latex at the coagulation stage as part of a combined coagulating agent, which also includes PDMDAAH. This approach allows to achieve complete coagulation at a lower consumption of PDMDAAH than in the prototype, to refuse from introducing sodium chloride into the system at the coagulation stage, to provide a high yield of rubber crumb, which is a fiber-rubber composite, and at the same time to obtain the target product with improved mechanical properties and increased resistance to aging. The method allows to improve the quality of wastewater and at the same time solve the problem of recycling fiber-containing waste from industrial plants. This completely eliminates the problems associated with the instability of protein-containing coagulants during storage and use.

As the fibrous materials in the proposed method can be used any natural or synthetic fibers, which are waste from various industries, or obtained from outdated products from natural and artificial fibers, as well as a mixture of fibers of various nature.

As a product containing a polymeric cationic flocculant poly-N, N-dimethyl-N, N-diallylammonium chloride, a commercially available water-soluble cationic flocculant Polyelectrolyte VPK-402 containing, according to TU, at least 25 wt.% Of the main substance can be used. VPK-402 polyelectrolyte is used in the oil and gas industry, in water treatment technologies for the treatment of natural and waste waters.

To obtain a combined coagulating agent according to the present invention, the fiber is pre-subjected to pulping, crushed to a size of 2 ÷ 10 mm, and then mixed with milling for 10 ÷ 15 minutes at a given temperature with the calculated amount diluted to a concentration of 1 ÷ 5% PDMDAAH aqueous solution. The aqueous dispersion thus obtained is used further as a coagulating agent. The need to dilute VPK-402 Polyelectrolyte is associated with the complexity of the dosage of its concentrated solutions under industrial conditions. If the required norms are exceeded, recharging of the system can occur, leading to the loss of components of the emulsion system, to the leakage of the polyelectrolyte to the treatment plant, which can cause the death of activated sludge and disruption of the water treatment system.

Coagulation is carried out in the temperature range from 40 to 80 ° C.

The method is as follows.

Styrene-butadiene latex, in which the antioxidant was previously introduced, is mixed in a coagulation tank at a given temperature and with constant stirring with an aqueous dispersion of the coagulating agent obtained as described above. The amount of coagulating agent required for complete coagulation is determined empirically depending on the composition of the combined coagulant (fiber composition, relative mass content of fiber and PMDAAH based on dry matter), as well as on the physicochemical characteristics of latex, which can vary from batch to batch . The mixture is additionally stirred for several minutes, after which, to complete the coagulation process, a 1 ÷ 2% aqueous solution of sulfuric acid is introduced with stirring until a pH of 2.5 is reached. Obtaining transparent serum indicates the completeness of coagulation. The consumption of sulfuric acid does not exceed 15.0 kg / t of rubber.

Table 1 shows examples of the implementation of the proposed method using a combined coagulating agent, including various fibrous materials (fillers) in various mass ratios with PDMDAAH. SKS-30 ARK rubber, obtained by copolymerization of butadiene with styrene according to a continuous scheme, was used as styrene-butadiene rubber. Samples of cotton, viscose and kapron fiber obtained from textile waste were used as fibrous materials. As a source of PDMDAAH, VPK-402 Polyelectrolyte diluted with water to a working concentration of PDMDAAH 1-2% was used.

Table 1 Technological parameters Fiberfill Cotton fiber Viscose fiber Nylon fiber Dosage of fibrous filler, kg / t of fiber-rubber composite 0.5 1,0 5,0 10.0 12.0 5,0 5,0 5,0 5,0 5,0 Dosage PDMDAA, kg / t of fiber-rubber composite 0.6 0.375 0.275 0.250 0.250 0.250 0.225 0.250 0.275 0.250 The mass ratio of the fibrous filler: PDMDAAH 1: 1,2 1: 0.375 1: 0,055 1: 0,025 1: 0,021 1: 0.05 1: 0.05 1: 0.05 1: 0,045 1: 0.05 Dosage of combined coagulant, kg / t of fiber-rubber composite 1,1 1,375 5,275 10.25 12.25 5,250 5,225 5,250 5,275 5,250 Coagulation temperature, ° C 60 60 60 60 60 40 80 60 60 60 The output of the fiber-rubber composite,% 97.0 97.6 98.3 99.0 99.0 98.4 97.7 97.9 98.5 98.8 Example No. one 2 3 four 5 6 7 8 9 10

As can be seen from table 1, the effective coagulation of latex (the yield of the fiber-rubber composite is 97–99%) when the combined coagulating agent contains fibrous material in an amount of 0.5–12 kg / t of fiber-rubber composite and PDMDAAH in an amount of 0.225 ÷ 0.60 kg / t of fiber-rubber composite. In this case, the maximum yield is achieved with a dosage of fibrous material of 10 ÷ 12 kg / t and at low PDMDAAH costs not exceeding 0.250 kg / t of the resulting composite. The selection of rubber on the prototype requires a consumption of PDMDAAH 0.5-1.5 kg / t of rubber crumb.

From the above examples it is seen that the influence of temperature in the range of 40 ÷ 80 ° C on the product yield is negligible. The nature of the fibrous filler used also does not significantly affect the coagulation efficiency. In the entire range of mass ratios used, the fibrous filler: PDMDAAX achieves a high yield of fiber-rubber composite. An increase in the dosage of fibrous filler can adversely affect the physicomechanical properties of the vulcanizates; a decrease in the dosage of PDMDAAH can lead to incomplete coagulation. The higher the content of fibrous material in the coagulating agent, the less PDDMDAAH is required. This pattern holds true until the fiber dosage reaches 5 kg / t fiber composite. A further increase in the content of fibrous material, regardless of its nature, practically does not affect the consumption of PDMDAAH, which remains at the level of 0.225 ÷ 0.275 kg / t of rubber.

The crumb of the fiber-rubber composite obtained after processing with dilute sulfuric acid is separated from serum, washed with water and dried at a temperature of 80 ÷ 85 ° C. Rubber compounds obtained from crumbs after vulcanization are tested for physical and mechanical properties.

Table 2 presents the test results in comparison with the corresponding indicators for filled rubber SKS-30 ARC according to TU 38.40355-99 and the prototype.

As can be seen from Table 2, the vulcanizates obtained from the fiber-rubber composite in accordance with the invention correspond to TU conditions and have improved indicators compared to the prototype: higher resistance to dynamic loads (resistance to repeated stretching) and greater resistance to thermo-oxidative effects (aging factors) .

Thus, the proposed method for the isolation of styrene-butadiene rubber from latex provides complete coagulation of latex at a reduced cost of poly-N, N-dimethyl-N, N-diallylammonium chloride compared to the prototype, does not require the use of mineral salts, eliminates the problems associated with the use of protein fillers, and at the same time provides a product that allows to obtain vulcanizates with improved physical and mechanical properties.

Claims (2)

1. The method of isolation of styrene-butadiene rubber from latex by coagulation using a combined coagulating agent containing poly-N, N-dimethyl-N, N-diallylammonium chloride, followed by acidification of serum with mineral acid, separation and drying of rubber crumbs, characterized in that the combined coagulating agent additionally contains fibrous material in the following mass ratio of components, calculated on the dry matter: fibrous material: poly-N, N-dimethyl-N, N-diallylammonium chloride = 1: (0.020 ÷ 1,2). 2. The method according to claim 1, characterized in that as the fibrous material using materials obtained from natural, artificial and synthetic fibers.