JPS5953289B2 - Method for producing liquid cis-1,4-polyisoprene rubber aqueous dispersion - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a relatively high molecular weight and high viscosity liquid sis
, relates to a method for producing an aqueous dispersion of 4-polyisoprene rubber.

More specifically, the molecular weight. Adding an organic acid capable of forming soap to liquid cis-1,4-polyisoprene rubber of 10,000 to 60,000 in the presence of an aqueous solution of an alkaline substance;
Liquid cis-1,4-polyisoprene rubber water is mixed and then stirred and emulsified in the presence of water in which the alkaline substance is dissolved.

The present invention relates to a method for producing a dispersion. Conventionally, one method for producing aqueous dispersions of polymers is to mix an organic acid capable of forming a water-soluble soap in a polymer solution, convert the acid into soap in an emulsion, and then mix this with water. The method of stirring and emulsifying was published in 1977.
(888.

This method is known from the publication No. 1, and is used to process polyisoprene, polybutadiene, ethylene-propylene terpolymer, styrene-butadiene (or isoprene) random or block copolymer obtained by solution polymerization,
This method has no significant effect compared to the method of adding soap (emulsifier) to a polymer solution such as butyl rubber and continuously emulsifying it in one step.
For example, even if an aqueous dispersion is produced using know-how techniques, the particle size will only be slightly smaller, and if the emulsifying effect on the polymer or the degree of stirring during emulsification, which is inherently difficult for an aqueous dispersion, is reduced. effect is not achieved. In that sense, the method described in Japanese Patent Publication No. 35-6888 does not require a smaller amount of soap than the usual emulsification method; The use of such large amounts of emulsifiers or very vigorous agitation leaves many problems in aqueous dispersions and their preparation. A high-temperature emulsification method in which emulsification is achieved by raising the temperature of the emulsified material and soap water may be adopted as a solution to this problem, but in this case, significant foaming occurs during emulsification, resulting in various problems. becomes. In other words, at high temperatures that reduce the viscosity of the emulsified product system, foaming during emulsification increases, and a large amount of soap that is not attached to the particles of the emulsified product is adsorbed on the surface of the bubbles generated at this time. As a result, the amount of soap required for the emulsified material is reduced, and the particle size may not be reduced, or cavitation (idling) may occur excessively due to the air bubbles mixed in, resulting in the shearing force of the emulsified material being reduced. Furthermore, the mixed air bubbles aggregate and become coarse, and the hydrophobic substances in the composition are selectively adsorbed to the interface, making the emulsion system uneven and unstable.
In the end, the bubbles floated up with the emulsified material and separated. Also, unfortunately, this method cannot use general-purpose emulsifiers that are usually used for high-temperature emulsification and have the maximum emulsifying effect around room temperature.
Only specific emulsifiers that exhibit emulsifying effects at high temperatures can be used. This limits the uses of the obtained aqueous dispersion. In the case of these emulsifications, the viscosity of the polymer system must be reduced to below several tens of voids using an emulsifier and the help of an organic solvent, and emulsification must be performed by applying a large mechanical shearing force. It requires an emulsifying machine with a large horsepower, and great care must be taken in controlling the process.

Additionally, a large amount of organic solvent remains in the resulting aqueous dispersion, resulting in a substantial reduction in the concentration of the polymer in the aqueous dispersion, and furthermore, the removal of this organic solvent or the aqueous dispersion In order to concentrate the aqueous dispersion, passing through these steps while maintaining the stability of the aqueous dispersion is very difficult and takes a long time, there is a high risk of precipitation of coagulum, and the particle size Problems have also been pointed out, such as the emulsion becoming enlarged and making it difficult to produce a stable emulsion. There are various problems involved in emulsifying a polymer having a high viscosity of several thousand poise, and it has not been possible to easily obtain a stable aqueous dispersion.

On the other hand, liquid cis-1,4-polyisoprene rubber with a high viscosity and a molecular weight of 10,000 to 60,000 exhibits rubber physical properties that are not exhibited by liquid rubbers with a molecular weight of several thousand at most, and has various properties, such as: It can be molded using general rubber vulcanization technology that has been used for a long time, and can be easily combined with natural rubber, synthetic rubber such as synthetic cis-1,4-polyisoprene rubber, and polyptadiene rubber. It can be vulcanized, and when used as a softener for adhesives, it has a good balance between agglomeration and adhesive strength.

Blending such liquid cis-1,4-polyisoprene rubber into solid rubber can be carried out using a kneading machine using a conventional method, but synthetic rubber latexes such as natural rubber latex and cis-1,4-polyisoprene rubber latex can be blended. Alternatively, when blending with other synthetic resin emulsions, the liquid cis-1,4-polyisoprene rubber must of course be prepared as an aqueous dispersion. In view of these circumstances, the present inventor has developed a high viscosity,
As a result of various studies on methods for emulsifying high molecular weight liquid cis-1,4-polyisoprene rubber without using any organic solvent, it was found that the molecular weight was 10,000 to 6.
0000 liquid cis-1,4-polyisoprene rubber in the presence of an aqueous solution of an alkaline substance, an organic acid capable of forming soap is added and mixed, and then stirred and emulsified in the presence of water in which the alkaline substance is dissolved. 0.1~8μ depending on
It was discovered that an extremely stable aqueous rubber dispersion having a particle size of

The liquid cis-1,4-polyisoprene rubber used in the present invention has a relatively high molecular weight, with a viscosity average molecular weight of 10,000 to 60,000, preferably 20,000 to 50,000.

The viscosity average molecular weight (Mv) here is evaluated by the following formula, and the method for measuring the intrinsic viscosity ([η]) in toluene at 30°C in the following formula is, for example, "Experimental Chemistry Course No. 8". Volume Kobunshi Kagaku (published by Maruzen Co., Ltd. in 1964). [η] = 1.21 x 10-4Mv0.77 These high molecular weight liquid cis-1,4-polyisoprene rubbers are produced by anionic polymerization in which isoprene monomers are polymerized using a lithium catalyst, or by natural polymerization. Rubber and synthetic cis-1,4 obtained by Ziegler monopolymerization or anionic polymerization
- polyisoprene rubber at high temperature (e.g. 200-300
It is obtained by pyrolysis at ℃).

However, liquid cis-1,4- obtained by pyrolysis method
Polyisoprene has a strong odor and is heavily colored due to substances produced as by-products during thermal decomposition, and furthermore, it is difficult to stabilize its quality. Therefore, liquid cis-1,4-polyisoprene contains 75% or more of cis-1,4 bonds obtained by an anionic polymerization method, that is, a method in which isoprene monomer is polymerized using metallic lithium or organic lithium as a catalyst. Preferably. In the present invention, a modified liquid cis-1,4-polyisoprene having a functional group such as a hydroxyl group, a halogen group, or a maleic anhydride group added to the molecule can also be used.

An organic acid capable of forming soap in the presence of an alkaline substance added to the liquid cis-1,4-polyisoprene rubber used in the present invention is defined as an organic acid having at least 8 carbon atoms in the molecule, more preferably An organic acid containing 8 to 24 carbon atoms per carboxylic acid in the molecule, such as higher aliphatic saturated basic carboxylic acids (purinic acid, lauric acid, palmitic acid, stearic acid), higher aliphatic Examples include resin acids such as unsaturated basic carboxylic acids (oleic acid, linoleic acid, linolenic acid), rosin acids (abietic acid, levopimaric acid, textropimaric acid, tetrahydrobietic acid), and the like.

These soap-forming organic acids may be used alone or in combination of two or more. This organic acid not only forms a salt in an aqueous solution containing an alkaline substance during emulsification to provide a stable aqueous dispersion, but also provides an aqueous dispersion with a small particle size when stirred at about 1000 revolutions per minute. It also has functions and effects.

Although this cannot be explained well, soap is not immediately produced by mixing liquid cis-1,4-polyisoprene rubber containing an organic acid with an alkaline aqueous solution.
This is thought to be because the organic acid necessary for the particles is converted into soap on the fine particles generated by the shear force of stirring, and foaming is difficult because there is no large amount of excess soap in the emulsion system. The amount of the organic acid used is 0.5 to 10 parts by weight, more preferably 1 to 3 parts by weight, based on 100 parts by weight of liquid cis-1,4-polyisoprene rubber.

If the amount is less than this range, no substantial emulsifying effect will be observed;
On the other hand, if the amount is too high, the physical properties of products manufactured from the aqueous dispersion will deteriorate. The alkaline substance capable of forming a water-soluble soap with an organic acid may be any alkaline substance, but ammonia and anolekali metal hydroxide are particularly suitable.

The amount used is sufficient to neutralize the organic acid, but there is no problem even if it is larger or slightly smaller, and in general, a larger amount is preferable. An example of the manufacturing procedure of the liquid cis-1,4-polyisoprene rubber aqueous dispersion in the present invention is as follows.

(1) A predetermined amount of organic acid is mixed with liquid cis-1,4-polyisoprene rubber, and then water in which an alkaline substance is dissolved is added while stirring to emulsify.

(2) Liquid cis 1,4 in water containing an alkaline substance dissolved in it.
- A mixture of polyisoprene rubber and an organic acid is added under stirring and emulsified.

(3) Water with an alkaline substance dissolved and liquid cis 1,4
- a mixture of polyisoprene rubber and an organic acid added;
Add alternately or continuously and stir to emulsify.

(In either case, more water may be added after emulsification is completed.

) In these methods, there is nothing wrong with including other soaps in the liquid cis-1,4-polyisoprene rubber or in the aqueous phase.

If an aqueous dispersion with a finer particle size is required, it can be stirred and emulsified using an emulsifier with strong shearing force such as a homogenizer, homomixer, colloid mill, pipeline mixer, disper mill, or ultrasonic emulsifier. Good too.
Further, during emulsification, there is no problem even if the emulsification is carried out by heating at a high temperature.Furthermore, an antifoaming agent may be added for emulsification, and if necessary, a small amount of a solvent may be added for emulsification. In this way, in the present invention, emulsification while producing soap has the above-mentioned great effects, but the amount of water used at that time also has a large effect, and the liquid soap is Better results can be obtained by using 300 parts by weight or less, preferably 15 to 100 parts by weight, per 100 parts by weight of 4-polyisoprene rubber.

That is, since emulsification while producing soap has the above-mentioned effects, it is possible to form an aqueous dispersion by ordinary stirring in places where water in the above range is present. Here, the features of the present invention will be described based on the prior art as follows.

In other words, in the conventional technology, an organic solvent is used to reduce the viscosity of a polymer system to several tens of poise or less for emulsification. This is where it is emulsified.

In addition, in the conventional technology, 5 parts by weight per 100 parts by weight of the polymer.
Even if emulsified using ~15 parts by weight of an emulsifier (soap) or an acid capable of forming a water-soluble soap and stirring under strong shearing force, an aqueous dispersion with a large particle size of 5 to 20μ will be obtained. However, in the present invention, surprisingly, the amount of acid capable of forming soap used is 0.5 to 10% by weight. This means that a stable aqueous dispersion having a particle size as small as 0.1 to 4 μm can be obtained even by gentle stirring. Furthermore, when emulsifying rubber by adding soap from the beginning, excess soap other than the emulsifier that adheres to the particles can generally cause foaming during stirring, but in the present invention, soap is added to the particles. Since the required amount of soap to be deposited is formed from the organic acid and the alkaline substance, there is less excess soap and therefore less foaming, resulting in a stable aqueous dispersion of fine particles. These surprising effects cannot be fully explained, but they are due to the effects of a method in which soap is produced and emulsified with low-molecular compounds such as cosmetics and oils for the purpose of reducing the particle size of an aqueous dispersion. Although it is not observed in the case of the high polymer solution as mentioned above, it is extremely noticeable in the present invention, which uses a liquid rubber with a smaller molecular weight, and attracts attention. worth it. Moreover, the amount of organic acid used to produce the soap used for its great effect, and therefore the amount of soap produced in the aqueous dispersion, may be 1 to 2 parts by weight in the best case. , an aqueous dispersion with extremely good physical properties is provided. Furthermore, since it can be widely used as an organic acid capable of producing soap, the resulting aqueous dispersion can be used in a wide variety of applications.

In addition, transport of aqueous dispersion may lead to deterioration of stability of aqueous dispersion,
Although problems such as precipitation of polymer coagulum may occur and are difficult, in the case of the present invention, the liquid cis-1,4-polyisoprene rubber mixture containing an organic acid is transported instead of an aqueous dispersion. Another advantage is that a stable aqueous dispersion can be easily obtained by adding an aqueous solution of an alkaline substance and stirring under gentle conditions using a commonly used stirrer. The liquid cis-1,4-polyisoprene rubber aqueous dispersion thus obtained exhibits very good stability and can be used in adhesives, adhesives, rubber gloves, finger bags, etc. It is widely used for products such as dipping products, cast products such as rubber toys, rubber-based products, packaging such as palm locks, foam rubber, and crowns of pins, and products such as carpets and non-woven fabrics.

Hereinafter, the present invention will be explained in more detail with reference to 5N examples, but the present invention is not limited to these examples in any way.

Example 1 Liquid cis-1,4 with a molecular weight of 25,000 was produced by polymerizing isoprene monomer using a butyllithium catalyst.
- Polyisoprene rubber was obtained.

2.5 parts by weight of oleic acid was added to 100 parts by weight of the liquid cis-1,4-polyisoprene rubber and mixed well by stirring. The mixture thus obtained is heated to 60°C. On the other hand, an aqueous solution was prepared by dissolving potassium hydroxide in an amount 1.1 times the amount required to neutralize the above oleic acid in 40 parts by weight of water. This aqueous solution was placed in an ordinary stirrer with turbine blades set at a temperature of 60°C, and the mixture of oleic acid and liquid cis-1,4-polyisoprene rubber was added at once to this while stirring to emulsify. . The liquid cis-4-polyisoprene rubber aqueous dispersion thus obtained was stable and had a particle size in the range of 0.1 to 4μ (the number average particle size was 0.7μ). Ta. Moreover, this emulsion had stability to the extent that it was slightly tarnished even after being left for one month. Example 2 A mixture of liquid cis-1,4-polyisoprene rubber and oleic acid prepared in Example 1 was added to the aqueous potassium hydroxide solution prepared in Example 1 under stirring under the same conditions as in Example 1. It was added gradually and emulsified.

In this way, an aqueous dispersion with a relatively small particle size in the range of 0.1 to 3μ was obtained (number average particle size was 0.6μ).
It was μ. ). This aqueous dispersion showed almost no creaming even after being left for one month. Example 3 Liquid cis-1,4 with a molecular weight of 40,000 was obtained by polymerizing isoprene monomer using a butyllithium catalyst.
- Polyisoprene rubber was obtained.

Claims (1)

[Scope of Claims] 1. Liquid cis-1 having a molecular weight of 10,000 to 60,000,
4-A liquid system characterized by adding and mixing an organic acid capable of producing soap to polyisoprene rubber in the presence of an aqueous solution of an alkaline substance, and then stirring and emulsifying the mixture in the presence of water in which the alkaline substance is dissolved. -Manufacture of a 1,4-polyisoprene rubber aqueous dispersion. Method.