JPS5918703A - Coagulation of synthetic rubber latex - Google Patents

Abstract

PURPOSE:To coagulate a synthetic rubber latex in high efficiency with rubber crumbs being moderate in flocculation and porosity, using a small quantity of coagulant, by adding an aqueous solution of a polyalkylenepolyamine-epihalohydrin copolymer to a synthetic rubber latex of a specific pH. CONSTITUTION:The objective coagulation can be achieved by adding to (A) a synthetic rubber latex with its pH-value adjusted to 1.3-7 by an acid. (B) 0.005-5pts.wt. (per 100pts.wt. of the rubber solid in the latex) of an aqueous solution of a polyalkylenepolyamine-epihalohydrin copolymer prepared by the reaction between a polyalkylenepolyamine and an epihalohydrin in a molar ratio 1/0.3-2.5.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for coagulating synthetic rubber latex, which comprises efficiently coagulating synthetic rubber latex particles by adding an aqueous solution of a polyalkylene polyamine-epihalohydrin copolymer to the synthetic rubber latex.

The production of synthetic rubber by emulsion polymerization necessarily involves the formation of a synthetic rubber latex, and converting this latex into non-stick rubber crumb requires coagulation of the synthetic rubber particles present in the latex. do. Various coagulants such as inorganic salts such as sodium chloride, polyethyleneimine, dimethylamine-epichlorohydrin copolymer, dicyandiamide-formalin condensate, or organic polymer compounds such as cationically modified starch are used to achieve coagulation of the synthetic rubber particles. It is well known that

By the way, when these coagulants are used, it may not be possible to completely coagulate the rubber particles in the latex, or it may be necessary to add a large amount of coagulant to complete the coagulation, or the amount of coagulant may be increased. The shape of the rubber crumbs is fused and enlarged to form lumps, which makes it extremely difficult to wash and remove residues of polymerization catalysts, emulsifiers, or other coagulation aids such as inorganic salts contained in the lumps in the post-process. Furthermore, there are problems such as the need to strictly control the PH1 temperature of the latex or the amount of inorganic salts added in order to moderate the porosity of the rubber crumb to facilitate drying in the next process. was there.

In view of the current situation, the present inventors have conducted extensive research to solve various problems in the coagulation process of synthetic rubber latex, and as a result, they have added polyalkylenebolyamine-epihalohydrin as a coagulant to synthetic rubber latex with an adjusted pH range. By adding an aqueous solution of cobolimer, it is possible to coagulate the Latinx particles with the addition of an extremely small amount of coagulant compared to the conventional method using a coagulant.
The present invention was completed based on the discovery that it has a wide i-circumference, moderate agglomeration state of rubber crumb, moderate porosity, excellent post-cleaning and drying properties, provides a colorless serum, and has no adverse effect on the physical properties of the final rubber. I ended up doing it.

That is, the present invention provides a method for coagulating synthetic rubber latex, which comprises adding an aqueous solution of a polyalkylene polyamine-epihalohydrin copolymer to synthetic rubber latex having a pH of 1.3 to 7.

In the aqueous solution of polyalkylene polyamine-epihalohydrin copolymer used as a coagulant in the present invention, the copolymer has a molar ratio of polyalkylene polyamine to epihalohydrin of 1:0.3 to 2.5, preferably 1:0.5 to At a ratio of 1.5, the reaction temperature is usually 2.
It is obtained by reacting at 0 to 80°C for a reaction time of about 30 minutes to IO hours.

Here, examples of polyalkylene polyamines include diethylenetriamine, triethylenetetramine, tetraethylenepentamine, iminobispropylamine, etc.
These may be used alone or as a mixture of two or more. Further, examples of epihalohydrin include epichlorohydrin and shrimp bromohydrin, and epichlorohydrin is preferred.

The present invention uses an aqueous solution of such a polyalkylene polyamine-epihalohydrin copolymer, and the viscosity of the aqueous solution is preferably 3 Q cps or more when the solid content is 50% by weight and the temperature is 25°C. Preferably, if it is less than 3 Q cps, it tends to be difficult to obtain the desired effect. In addition, there is no particular restriction on the upper limit of viscosity, but usually solids concentration is 50% and 25°C.
2000 cps or less is used. Viscosity is 2
If it exceeds 000 CPS, the viscosity stability of the aqueous solution of the copolymer tends to be poor over time, and the viscosity often increases during storage and becomes a gel, which is inconvenient for use. It becomes necessary to store the product or to extremely shorten the period of use after production.

The addition M of the aqueous solution of polyalkylene polyamine-epihalohydrin copolymer is not particularly limited, and varies depending on the type of synthetic rubber latex, the liquid temperature at pH1 coagulation, the presence or absence of salts used in combination, and the amount thereof, etc. It may be sufficient as long as it is sufficient to coagulate, but usually it is 0.005 parts by weight or more as solids per 100 parts by weight of rubber solids in the synthetic rubber latex, preferably 0.01 parts by weight.
M (more than Okibe, more preferably more than 0.02 Kuradato. There is no particular restriction on the upper limit, but even if it is used in too many companies, the effect will not increase accordingly, and it is economically disadvantageous. Therefore, the amount is usually 5 parts or less, preferably 1 part - 1 part or less.

In addition, in the present invention (in this case, it is necessary that the pif of the synthetic rubber latex to which the aqueous solution of polyalkylene polyamine-epihalohydrin copolymer is added is in the range of 1.3.-7), Since latex is alkaline, the pH is generally adjusted in advance to the above range by adding an acid.

As the acid used, inorganic or organic acids can be used, and examples thereof include sulfuric acid, hydrochloric acid, acetic acid, and oxalic acid. If the pH value of the synthetic rubber latex to be treated exceeds 7, the coagulation effect will be poor and a large amount of coagulant will be required, which is uneconomical, and if the pH is less than 1.3, the coagulation effect will not improve. However, this method only increases the growth caused by acid use, which is economically disadvantageous, and both are undesirable.

Furthermore, in the present invention, conventionally known salts can be used in combination to more effectively coagulate the coagulation. Salts include water-soluble alkali metal inorganic acid salts,
Alternatively, it is an organic acid salt, such as an alkali metal salt such as hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid, acetic acid, citric acid, malic acid, oxalic acid, maleic acid, etc., and sodium chloride is usually used.

The general strategy for adding these salts is 0 to 20 parts by weight per 100 parts by weight of rubber solids in the synthetic comb latex, and even if the amount exceeds 20 parts by weight, No improvement in effectiveness was observed, which is not desirable.

Furthermore, the synthetic rubber latex referred to in the present invention includes styrene-butadiene latex, acrylonitrile-butadiene latex, polybutadiene latex, ethylene-propylene latex, polyisoprene latex, or carboxylated latex thereof, and the rubber in the latex Particularly good coagulation effects are obtained when the particle concentration is greater than io% by weight.

Furthermore, when coagulating synthetic rubber latex by the method of the present invention, there are no particular restrictions on the method and order of adjusting the latex pH, adding an aqueous solution of polyalkylene polyamine-epihalohydrin copolymer as a coagulant, and adding salts as necessary. There isn't.

Also, regarding the temperature of synthetic rubber latex during coagulation, O
Although it can be applied in a wide range from 100°C to 100°C, it is advantageous to carry out the process at 50°C or higher in terms of a retention property.

The present invention will be explained below with reference to Examples.

The coagulants used in each example were as follows: [Resin-A] An aqueous solution of diethylenetriamine-epichlorohydrin copolymer obtained by reacting 1 mole of diethylenetriamine with 1 mole of shrimp chlorohydrin at 60°C for 4 hours. The viscosity of an aqueous solution with a solid content of 50% by weight is 75 cps (
25°C).

[Resin-B-J] Various amines and epichlorohydrin shown in Table 1 were reacted in the same manner as in the case of resin to obtain an aqueous solution of each amine-epichlorohydrin copolymer.

The solid content of each copolymer aqueous solution obtained was 50
The viscosity at 25° C. in weight percent is shown in Table-■.

The amines in Table 1 are indicated by the following abbreviations.

DETA diethylenetetramine TETA:) Liethylenetetramine TEPA: Tetraethylenepentamine DMA dimethylamine Table 1 Examples 1-9. Comparative Example 1 Styrene-butadiene latex (1
500 grade) and the pH was adjusted to approximately 4 by adding sulfuric acid.・Add a coagulant to this, stir and mix for 2 minutes, stop stirring, and use a 60 mesh wire mesh to coagulate and precipitate the rubber (floating on the shoulder above the liquid) and liquid layer (referred to as serum water). For serum water, use a turbidity meter (manufactured by Nippon Seimitsu Kogaku Co., Ltd.) to measure
The turbidity was measured according to 01, and the degree of coagulation of the latex was determined. In this case, the turbidity is low and the transparent serum water has no residual emulsified rubber latex particles.
This indicates that the latex has completely solidified. In addition, the porosity (surface porosity, roughness) and particle size of No. 1 pseudo-hard rubber were visually evaluated, and those that were very stable were evaluated to be suitable for the drying process in the post-process of synthetic rubber manufacturing, and those that were good were evaluated as good. Those that were inferior were considered defective.

The results are shown in Table-2.

In addition, in the table, the additive rings of common salt and coagulant indicate their respective solid content relative to the rubber solid content in the synthetic rubber latex.

Examples 1O-12. Comparative Examples 2 to 4 Using the same styrene-butadiene latex as used in Examples 1 to 9, the results were shown in Table 3 using a salt combination system.

Procedural amendment (spontaneous) September 1981 Kazuo Wakasugi, Commissioner of the Japan Patent Office1, Indication of the matter 1981 Patent application No. 1281282, Name of the invention Method for coagulating synthetic comb latex 3 Addendum 1F Relationship with construction project 1 Patent applicant address 5-15 Kitahama, Higashi-ku, Osaka Name (20
9) Sumitomo Chemical Co., Ltd. Representative: Takeshi Kamigata 4, Agent Address: 5-1 Kitahama, Higashi-ku, Osaka, Asaji Column for detailed explanation of the invention in the specification (1) On page 8, line 12 of the specification: “ Correct the word “colorless J” to “transparent”.

(2) The turbidity ppm of serum water in Table 2 on page 18 of Example 8 is corrected from "fL, 2" to "12".

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Claims (1)

[Claims] A method for coagulating synthetic rubber latex, which comprises adding an aqueous solution of polyalkylene polyamine-epihalohydrin copolymer to synthetic rubber latex having a pH of 1.3 to 7.