JP5394779B2 - Modified natural rubber and method for producing modified natural rubber latex, modified natural rubber, modified natural rubber latex and tire using modified natural rubber - Google Patents

Description

The present invention relates to a modified natural rubber, a method for producing a modified natural rubber latex, a modified natural rubber, a modified natural rubber latex, and a tire using the modified natural rubber.

Epoxidized natural rubber and epoxidized natural rubber latex are obtained by epoxidizing latex natural rubber. This modification of natural rubber is performed by adding hydrogen peroxide and formic acid or acetic acid to a natural rubber latex stabilized with a surfactant, generating formic acid or peracetic acid in the latex, and reacting this with natural rubber. Epoxidize. Thereafter, when solid rubber is required, the latex is coagulated, and if necessary, neutralized, washed and dried. On the other hand, it is possible to further modify the epoxidized natural rubber by utilizing the latex state. Since natural rubber contains many gel components that are insoluble in the solvent, chemical modification using the solvent is difficult. Moreover, since it is not good for the environment to use a solvent, latex is preferably used because it can be chemically modified in an aqueous system.
When acetic acid is used for epoxidation, the production rate of peracetic acid is slow. Therefore, a strong acid such as sulfuric acid or p-toluenesulfonic acid is added as a catalyst. When formic acid is used, the epoxidation reaction is fast, so no catalyst is required, but the reaction takes at least about 2 to 24 hours. Patent Document 1 and Non-Patent Documents 1 and 2 have a description of 23 to 24 hours at 60 ° C., and Non-Patent Documents 1 and 2 have 6 to 14 hours at 50 ° C. and 40 to 120 hours at room temperature. And there is a problem that it takes a very long time to react. If the reaction takes a long time, the manufacturing costs will be high, such as labor costs and electricity costs (or fuel costs, etc.).

Such a reaction is a so-called batch method in which a predetermined weight of latex or chemical is charged into a container and reacted. When using formic acid, the epoxidation does not proceed at once as described above, and the reaction takes time, so that the degree of epoxidation varies as long as the time that the latex stays in the container is not the same. Become. Therefore, when the time during which the latex stays in the container is not constant, variation in the degree of epoxidation becomes a problem. In addition, in the case of moving to the coagulation step after completion of the reaction, coagulation with an acid or salt cannot be performed, and thus coagulation by temperature rise using the cloud point of the surfactant is used. At that time, water vapor is often used as a heat source, and there is a problem that the time during which the latex stays in the container is not constant during the treatment. Therefore, it is necessary to add an extra hydrogen peroxide so that the epoxidation reaction does not proceed while the latex remains in the container, or to add an agent for stopping the reaction. If an amount of hydrogen peroxide that is not excessive or insufficient is used, it is natural that the amount of formic acid generated correspondingly decreases and the reaction time increases.

Further, in the batch reaction, the temperature rises as the reaction proceeds, but the surfactant added as a stabilizer may become unstable and the rubber may gel. Therefore, strict temperature control is necessary, but if the size of the container is large, temperature unevenness is likely to occur, and even if the wall surface temperature is controlled, the internal temperature tends to run away, and reaction control is very difficult.

In addition, there is also known a method of mixing natural rubber latex and peracetic acid in a container and epoxidizing, but in this method, the reaction heat is large, and when peracetic acid is added at once, the entire latex hardens due to intense heat generation, A uniform reactant cannot be obtained. Therefore, although it is necessary to reduce the addition rate of peracetic acid, since the addition takes time, the distribution of epoxidation degree becomes large.

British Patent Application No. 2113692

David R. Barfield, two others (David R. Burfield et al.), “Journal of Applied Polymer Science”, 1984, Vol. 29, No. 5, p. 1661-1673 Nguyen Viet Bac et al., “Journal of Applied Polymer Science”, 1991, Vol. 42, No. 11, p. 2965-2933

An object of the present invention is to provide a modified natural rubber and a method for producing a modified natural rubber latex capable of making the properties of the reaction product constant while greatly reducing the reaction time and reducing the time required for reaction control as much as possible. It is to provide a modified natural rubber and a modified natural rubber latex obtained by the above production method, and a tire using the modified natural rubber.

As a result of intensive studies, the inventors have (a) a step of preparing peracetic acid from acetic acid and / or acetic anhydride and hydrogen peroxide, and (b) a step of mixing while continuously supplying the peracetic acid and natural rubber latex. And (c) a step of continuously transporting the mixed liquid, and (d) a step of coagulating the epoxidized natural rubber latex as necessary, and at least the step (c) epoxidizing the natural rubber latex The present invention has been completed by finding that the above-mentioned problems can be solved by the method for producing modified natural rubber and modified natural rubber latex.

That is, the present invention
(A) preparing peracetic acid from acetic acid and / or acetic anhydride and hydrogen peroxide;
(B) mixing the above-mentioned peracetic acid and natural rubber latex while continuously feeding; and
(C) It is related with the manufacturing method of the modified natural rubber latex which includes the process of transporting the mixed liquid continuously and epoxidizes the natural rubber latex in at least the process (c).

In the step (b), the peracetic acid and the natural rubber latex are preferably mixed in the flow path.
In the step (b), it is preferable that the peracetic acid and the natural rubber latex are supplied into the container and mixed in the container.
The dry rubber content in the natural rubber latex is preferably 5 to 67% by weight.

The present invention also relates to a modified natural rubber latex produced by the above production method.

The present invention also provides
(A) preparing peracetic acid from acetic acid and / or acetic anhydride and hydrogen peroxide;
(B) a step of mixing while continuously supplying the peracetic acid and natural rubber latex;
(C) a step of continuously transporting the mixed liquid to step (d), and
(D) It relates to a method for producing a modified natural rubber comprising a step of coagulating an epoxidized natural rubber latex, wherein at least the step (c) epoxidizes the natural rubber latex.

In the step (b), the peracetic acid and the natural rubber latex are preferably mixed in the flow path.
In the step (b), it is preferable that the peracetic acid and the natural rubber latex are supplied into the container and mixed in the container.
In step (d), it is preferable to neutralize the acid remaining in the rubber after coagulation with a basic substance.
It is preferable to perform the step (d) without storing the epoxidized natural rubber latex transported in the step (c) in the tank.
The dry rubber content in the natural rubber latex is preferably 5 to 67% by weight.

The present invention also relates to a modified natural rubber made by the above production method.

The present invention also relates to a tire using the modified natural rubber.

According to the production method of the present invention, natural rubber latex and peracetic acid are mixed and reacted in step (c) (for example, in the piping), thereby enabling uniform mixing and strict temperature control, and shortening the reaction time. Thus, a stable quality epoxidized natural rubber latex can be produced.
In addition, by controlling the residence time in the container and the residence time in step (c) (for example, in the piping), the distribution of the degree of epoxidation can be adjusted. This is very effective in widening the adjustment range when controlling the blendability (morphology) with other rubbers. Further, by controlling the mixing amount of latex and peracetic acid, various degrees of epoxidation can be achieved extremely easily and stably.
In addition, a large reactor requires a large-scale production apparatus, while the present invention allows the production amount to be controlled freely by increasing or decreasing the number of units while using an inexpensive and very simple apparatus. This eliminates the need for studying the conditions associated with scale expansion.

Hereinafter, the present invention will be described in detail.

(A) Preparation of peracetic acid from acetic acid and / or acetic anhydride and hydrogen peroxide in advance In order to make the properties of the reaction product constant, the epoxidation reaction time, which has conventionally taken several hours to several tens of hours, is set. It is desirable to shorten it dramatically. To achieve this, the present invention uses peracetic acid instead of performic acid. When using peracetic acid, as described above, even if acetic acid and hydrogen peroxide are added to the latex, the production rate of peracetic acid is slow, so it is necessary to add a strong acid. It takes. To solve this problem, peracetic acid is prepared in advance.

Peracetic acid is prepared by mixing acetic acid and / or acetic anhydride with hydrogen peroxide.
As the hydrogen peroxide, an aqueous solution having a concentration of 1 to 60% can be used, but considering safety and efficiency, hydrogen peroxide having a concentration of 5 to 50% is preferable. If the concentration of hydrogen peroxide exceeds 50%, the risk of explosion increases, and if the concentration is less than 5%, the efficiency may deteriorate.
Acetic acid may be used in an aqueous solution having a concentration of 10 to 99.9% or 100%. The purity of acetic anhydride is not particularly limited, but is preferably 50 to 100%, and most preferably 80 to 100%.
Hydrogen peroxide is preferably added in an amount of 0.05 to 5 mol per mol of acetic acid and / or acetic anhydride. In consideration of safety and efficiency, 0.1 to 2 mol is more preferable. If the addition amount is less than 0.05 mol, the conversion of acetic acid may be remarkably reduced, which is not economical. On the other hand, if the addition amount exceeds 5 mol, the conversion rate of hydrogen peroxide may be remarkably lowered, which is not economical.
The lower limit of the reaction temperature is preferably 5 ° C, more preferably 10 ° C, and the upper limit is preferably 60 ° C, more preferably 45 ° C. If the lower limit is lower than 5 ° C, the time to reach equilibrium may be too long, and if the upper limit is higher than 60 ° C, hydrogen peroxide and / or peracetic acid to be generated may be decomposed.
At this time, if a strong acid (sulfuric acid, hydrochloric acid, nitric acid, etc.) is added in a small amount (1 to 7 mol%, more preferably 3 to 5 mol% of acetic acid and / or acetic anhydride) as required, the production efficiency of peracetic acid increases. In particular, since sulfuric acid is divalent, the production efficiency is high, and therefore it is inexpensive.
Even if an ion exchange resin is used instead of a strong acid, high production efficiency can be achieved. If it is a strong acid, it needs to be added each time, but if it is an ion exchange resin, the reaction can be carried out by simply contacting it, which is advantageous from the viewpoint of both the environment and the total cost. Preferred ion exchange resins include strong acid cation exchange resins or weak acid cation exchange resins.

(B) Step of mixing peracetic acid and natural rubber latex Subsequently, natural rubber latex and peracetic acid prepared in step (a) are mixed while being continuously supplied. For the mixing, a tubular reactor or a stirring vessel can be used, and the mixing is performed in a flow path or a container.
In addition, when peracetic acid and natural rubber latex are mixed, the epoxidation reaction of natural rubber latex starts, but the reaction can be suppressed by adjusting the temperature if necessary.

When the tubular reactor is used, it becomes easy to make the concentration distribution of the inflow raw material constant, and a product having a uniform degree of epoxidation can be easily obtained.
When using a tubular reactor, for example, using a Y-shaped connector, peracetic acid and natural rubber latex are separately pumped continuously and quantitatively into the flow path and mixed. Since the mixing is performed in the flow path, the transportation described later can be performed simultaneously.
The shape and material of the flow path are not particularly limited as long as uniform mixing can be performed.
In addition, although it does not specifically limit in order to mix completely, It is preferable to mix in a pipe | tube using a static mixer, a venturi nozzle, etc. Moreover, a tube pump, a magnetic pump, a diaphragm pump, a gear pump, a rotary pump, etc. can be used for a pump.

When a stirring vessel is used, mixing of raw materials in the container can be performed easily and inexpensively by using a stirring blade.
When using a stirring kettle, peracetic acid and natural rubber latex are fed continuously and quantitatively and mixed. In order to realize continuous raw material supply and continuous transport of the mixed liquid, the stirring vessel is provided with a raw material supply port and a mixed liquid discharge port, but the shape is not particularly limited.
The material of the stirring pot is not particularly limited, but any of metal, glass, and resin can be used. The part that comes into contact with the liquid is preferably subjected to a surface treatment such as glass lining, epoxy coating, or fluorine coating.
In order to obtain a product having a uniform degree of epoxidation, it is necessary to minimize the reaction that occurs in the stirring vessel and to react in the flow path after discharging the mixed solution from the stirring vessel. Since the raw material is continuously supplied to the stirring vessel, if the mixture stays in the stirring vessel for a long time, the raw material supplied earlier and the raw material supplied later are mixed. As a result, the mixture mixed for a long time in the stirring vessel and the mixture mixed for a short time are mixed and discharged, and the distribution of the degree of epoxidation of the rubber is widened. Therefore, it is preferable to mix the raw materials supplied to the stirring vessel in a short time and quickly discharge them to the flow path. Even if the mixing in the stirring vessel is insufficient, the mixing may be completed in the flow path.

The lower limit of the dry rubber content in the natural rubber latex is preferably 5% by weight, more preferably 20% by weight, still more preferably 30% by weight, and the upper limit is preferably 67% by weight, more preferably 60% by weight. . If the dry rubber content is less than 5% by weight, the reaction may not proceed due to excessive moisture. On the other hand, when the limit concentration of 67% by weight is exceeded, the rubber is hardened.
Natural rubber latex includes low ammonia latex with a low ammonia content and high ammonia latex with a high ammonia content, either of which may be used. The lower limit of the ammonia content is preferably 0.1% by weight, more preferably 0.15% by weight, and the upper limit is preferably 1% by weight, more preferably 0.7% by weight.

There is no restriction | limiting in particular about the addition amount of peracetic acid, According to the desired degree of epoxidation, it determines suitably.
By accurately controlling the mixing ratio of peracetic acid to natural rubber, the desired degree of epoxidation can be obtained easily and accurately. This control can be achieved very easily only by controlling the flow rate of the pump. Although it is possible to adjust the ratio theoretically even with the conventional batch method, it is actually very difficult.

As described above, the degree of epoxidation can be controlled according to the amount of peracetic acid added. In particular, it is more preferable when the degree of epoxidation is 12% or less for the following reasons.
The reaction for generating peracetic acid from acetic acid and hydrogen peroxide is an equilibrium reaction, and the degree of epoxidation can be achieved up to about 35%. If the desired degree of epoxidation is high, the amount of acetic acid and hydrogen peroxide used is large, which has a very negative effect on cost, and is a basic substance required for neutralizing wastewater and neutralizing the remaining acid in rubber. At present, the loss is large. On the other hand, when the desired degree of epoxidation is low, the amounts of acetic acid and hydrogen peroxide to be used are small, so that these problems do not cause problems. In the present invention, the degree of epoxidation is not particularly limited, but the preferred degree of epoxidation when considered from such a viewpoint is preferably a lower limit of 0.5, and an upper limit of preferably 12.0, more preferably. Is 10.0.
Even if such a degree of epoxidation is low, it is possible to achieve a desired epoxidation rate accurately by adding peracetic acid necessary for the reaction. Since the degree of epoxidation is determined by the amount of peracetic acid, it is important to accurately know the concentration of peracetic acid in the peracetic acid solution. The peracetic acid concentration can be accurately known by using a peracetic acid concentration meter (for example, a peracetic acid counter PA-300 manufactured by Hiranuma Sangyo Co., Ltd.).

It is desirable to add a surfactant to the natural rubber latex in advance in order to prevent coagulation.
As the surfactant, an anionic surfactant and / or a nonionic surfactant can be used. However, as described in conventional patents and literatures, a nonionic surfactant is preferable. The cloud point of the nonionic surfactant is preferably 60 ° C. at the lower limit and preferably 100 ° C. at the upper limit, but is not particularly limited as long as coagulation is not hindered. Specifically, polyoxyethylene lauryl ether, polyoxyethylene alkyl ether, polyoxyethylene alkylene alkyl ether, polyoxyethylene distyrenated phenyl ether, polyoxyethylene tribenzyl phenyl ether, polyoxyethylene fatty acid alcohol, etc. are used. be able to.
When an anionic surfactant is used, a large amount of surfactant is required to prevent the latex from coagulating when peracetic acid is mixed later, which is not economical. Therefore, it is preferable to use a nonionic surfactant in combination.
The addition amount of the surfactant is sufficient if it prevents coagulation of the natural rubber latex, and since the reaction time is very short, 2/3 to half of the conventionally used amount is sufficient. The reduction of the surfactant is a great merit in the subsequent cleaning. The lower limit of the addition amount of the surfactant is preferably 0.1 parts by weight and more preferably 0.5 parts by weight with respect to 100 parts by weight of the dried natural rubber. Further, the upper limit is preferably 5 parts by weight with respect to 100 parts by weight of dry natural rubber, and more preferably 3 parts by weight. If the amount is less than 0.1 part by weight, the rubber may be solidified. If the amount is more than 5 parts by weight, the cost may be increased and removal by washing may be difficult.

(C) Step of transporting mixed liquid Subsequently, the mixed liquid is continuously transported to, for example, the step (d) (coagulation step) using piping such as a tube.
As described above, when peracetic acid and natural rubber latex are mixed, the epoxidation reaction of natural rubber latex starts. In the production method of the present invention, epoxidation of natural rubber latex is performed at least in step (c), but epoxidation may be further performed in steps (b) and (d). It is preferable that 50% or more of the epoxidation reaction performed in all steps is performed in step (c).

Since the tube has a high heat exchange rate due to its structure, there is an advantage that the temperature of the solution can be strictly controlled just by immersing the tube in a constant temperature water bath, thereby maintaining an ideal reaction temperature.
The lower limit of the inner diameter of the tube is preferably 2 mm, more preferably 3 mm, and the upper limit is preferably 200 mm, more preferably 100 mm. If it is smaller than 2 mm, the production efficiency may be lowered, and if it is larger than 200 mm, strict temperature control may not be performed.

The lower limit of the liquid feeding speed of the mixed liquid is preferably 2 mm / min. If it is less than 2 mm / min, mixing tends to be insufficient and heat conduction efficiency tends to deteriorate. In addition, if the liquid feeding distance (pipe length) is not considered, the liquid feeding speed is not particularly limited, and may be, for example, 3000 mm / min.

The lower limit of the temperature of the piping during the epoxidation reaction is preferably 5 ° C, more preferably 10 ° C, and the upper limit is preferably 70 ° C, more preferably 55 ° C. If the temperature is lower than 5 ° C, the reaction may take too much time. If the temperature is higher than 70 ° C, the natural rubber latex may coagulate or partially decompose.
The lower limit of the temperature of the mixture during the epoxidation reaction is preferably 20 ° C, more preferably 30 ° C, still more preferably 40 ° C, and the upper limit is preferably 65 ° C, more preferably 60 ° C. If it is lower than 20 ° C, the reaction may not proceed sufficiently, and if it is higher than 65 ° C, the rubber may be solidified.

It is also possible to uniformly mix peracetic acid and natural rubber latex in this transport step. By carrying out mixing and transportation at the same time, the residence time of the mixed liquid can be shortened.

In the mixing step (b) and the transporting step (c), the residence time t1 of the mixture in the stirring vessel is preferably 0 to 12 minutes, more preferably 0 to 5 minutes. As described above, when the residence time in the stirring vessel becomes too long, the distribution of the degree of epoxidation becomes wide. Residence time t2 in the flow path (tube) is preferably 1 to 35 minutes, more preferably 5 to 10 minutes. However, since the reaction rate depends on temperature, the inner diameter of the tube, etc., the residence time is not necessarily limited.
The range of the degree of epoxidation is generally better in terms of product quality, but considering blending with different types of rubber, it is also useful for improving affinity, and the wide range is not necessarily bad. Absent.

As described above, according to the present invention, by transporting in a tube, uniform mixing and strict temperature control are possible, and temperature runaway that occurs in a batch reaction can be easily prevented. Is kept constant. In addition, large reactors require large-scale production equipment, but this method allows a small pump to be used as a set of 2 to 3 units, while increasing the number of units while using a cheap and very simple device. The production amount can be controlled freely. In large reactors, the optimal charge range is small and inflexible.

In the present invention, if necessary, an excessive epoxidation reaction is stopped before coagulating the epoxidized natural rubber latex. In order to stop the reaction, a reaction stopper may be added to the mixed solution to neutralize peracetic acid. As the reaction terminator, basic substances such as ammonia, sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium hydrogen carbonate and the like can be used. Termination of the epoxidation reaction can be confirmed by peracetic acid titration.

In the present invention, when the epoxidized natural rubber latex is coagulated, it is preferable to put the sent epoxidized natural rubber latex into a coagulation apparatus without storing it in a tank. When stored in the tank, the mixture of the epoxidation reaction that has been supplied for a long time and the mixture that has been supplied later and the epoxidation reaction has not progressed are mixed. Because it spreads. By sending it to the coagulation process without storing it in the tank, the time from mixing of raw materials to coagulation becomes almost constant, making it easier to align product quality.

(D) Process for coagulating epoxidized natural rubber latex The coagulation process can be carried out in the same manner as in the prior art. That is, a thin latex is poured into the inside of the cylinder, and steam is blown from below to heat the rubber in a countercurrent (counter flow) to coagulate it. The solidified rubber is removed from the lower part and separated from moisture. Here, the moisture includes acetic acid that has not been converted to peracetic acid, hydrogen peroxide, water generated by thermal decomposition of hydrogen peroxide, and serum after the rubber is removed from the latex. With steam coagulation, 97-99% of the rubber can be recovered if the device is well designed, and almost no rubber remains in the water. Therefore, even if rubber is filtered using a simple mesh, it can be filtered for a very long time until the mesh is clogged. If the liquid after filtering the rubber is concentrated, acetic acid can be recovered and reused. For the concentration, normal operations such as heating and reverse osmosis membrane can be used.

Moreover, it is preferable to neutralize the acid (acetic acid) remaining in the rubber after coagulation with a basic substance. By neutralizing, the delay of vulcanization can be prevented and the properties of the resulting rubber can be improved. The basic substance is not particularly limited, and ammonia, sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium hydrogen carbonate and the like can be used.

According to the production method of the present invention, the time from the mixing of peracetic acid and natural rubber latex until the excess epoxidation reaction is stopped or until the epoxidized natural rubber latex is coagulated, whichever comes first. Can be within 5 minutes to 2 hours. The conventional method required several hours, but if this method is used, it can be completed in a very short time, the degree of epoxidation can be adjusted, and energy and labor costs can be reduced. .

The modified natural rubber of the present invention is particularly useful as a tire material.
Natural glass epoxidation increases the glass transition point of natural rubber. When the degree of epoxidation increases by 1%, the glass transition point also increases by about 1 degree. When the degree of epoxidation is high, the glass transition point is greatly increased, so that the coefficient of friction when wet is increased and the braking distance when raining is shortened. On the other hand, the rolling resistance tends to be high, the fuel consumption tends to be poor, and it becomes hard at low temperatures and tends not to be suitable for, for example, winter tires. On the other hand, when the degree of epoxidation is low, the elastic modulus at a low temperature is small and can be suitably used for winter tires and the like.
Moreover, the polarity of rubber | gum raises by epoxidizing, affinity with the silica used as a filler becomes high, and a fuel consumption improves. In the present invention, even when the degree of epoxidation is small as described above, the affinity with silica is sufficient and the glass transition point can be lowered, so that it can be suitably used for winter tires and the like.
There is no restriction | limiting in particular in the manufacturing method of a tire, It can manufacture using the conventional manufacturing method.

The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

First, various chemicals used in Examples and Comparative Examples will be described.
Natural rubber latex: Raw ammonia latex (60% by weight of dry rubber, 0.2% by weight of ammonia) to which anti-corrosion and stability are added by adding ammonia and a small amount of zinc oxide and tetrathiuram disulfide
Surfactant: Polyoxyethylene fatty acid alcohol (alcohol carbon number C _{12 to} C ₁₈ , cloud point 70 to 80 ° C.)
Acetic acid: For the preparation of peracetic acid a and b, active ingredient 98% reagent grade 1 was used. For the preparation of peracetic acid c, the active ingredient 99% reagent grade 1 was used.
Formic acid: active ingredient 88% reagent grade 1 was used.
Hydrogen peroxide solution: Peracetic acid a, b was prepared with 50% active ingredient. For the preparation of peracetic acid c, 30% active ingredient was used.
Sulfuric acid: 98% active ingredient was used.

Production Example 1
<Preparation of peracetic acid>
(Preparation of peracetic acid a)
102 g of acetic acid, 113.3 g of hydrogen peroxide, and 2 g of sulfuric acid were mixed and allowed to stand at 40 ° C. for 1 day. When peracetic acid was quantified by titration, it was found that 24 g was produced. Peracetic acid a was prepared with the same formulation at 200 times weight. Peracetic acid was quantified using a peracetic acid counter PA-300 manufactured by Hiranuma Sangyo Co., Ltd. Hereinafter, quantification of peracetic acid was carried out in the same manner.

(Preparation of peracetic acid b)
102 g of acetic acid, 56.6 g of aqueous hydrogen peroxide, and 2 g of sulfuric acid were mixed and left at 40 ° C. for 2 days. When peracetic acid was quantified by titration, it was found that 21 g was produced. Peracetic acid b was prepared with 200 times the weight of the same formulation.

(Preparation of peracetic acid c)
101 g of acetic acid, 94.4 g of hydrogen peroxide, and 2.45 g of sulfuric acid were mixed and left at 40 ° C. for 1 day. When peracetic acid was quantified by titration, it was found that peracetic acid was generated at 13.3% by weight of the total liquid weight. Peracetic acid c was prepared at 200 times weight with the same formulation.

Production Example 2
<Preparation of performic acid>
(Preparation of performic acid a)
113.6 g of formic acid, 147.8 g of hydrogen peroxide, and 2 g of sulfuric acid were mixed and left at 40 ° C. for 1 day. When the formic acid was quantified by titration, it was found that 7.9 g was produced. Performic acid a was prepared in 200 times weight with the same formulation.

(Preparation of performic acid b)
113.6 g of formic acid, 123.2 g of hydrogen peroxide, and 3.20 g of sulfuric acid were mixed and left at 40 ° C. for 1 day. When the formic acid was quantified by titration, it was found that 5.3 g was produced. Performic acid b was prepared in 200 times weight with the same formulation.

Production Example 3
<Preparation of aqueous surfactant solution>
150 g of polyoxyethylene fatty acid alcohol (alcohol C _{12 to} C ₁₈ , cloud point 75 ° C.) 150 g was dissolved in 850 g of ion-exchanged water to prepare a 15 wt% aqueous surfactant solution.

Example 1
460 g of distilled water is added to 500 g of low ammonia natural rubber latex having a dry rubber content of 60% by weight (including 300 g of dry rubber), and 40 g of the 15% by weight surfactant (6.0 g of active ingredient) is added. And slowly stirred for 2 minutes.
This latex was fed into the mixing apparatus at a rate of 10.0 g / min using a tube pump (inner diameter of the tube 4 mm) whose amount of liquid was adjusted in advance. The size of the mixing device was 25 cc.
At the same time, the above-mentioned peracetic acid a was fed into the mixing apparatus so as to be 7.6 g / min. After sufficiently mixing them using a stirring blade in the mixing apparatus, the liquid is fed to the coagulation apparatus by a tube pump (inner diameter of the tube 5 mm) adjusted so that the liquid feeding amount is 17.6 g / min (850 mm / min). did. The temperature of the mixed solution at the time of mixing was 25 ° C., and the temperature of the mixed solution at the time of feeding was 55 ° C. Since the liquid is hardly stored in the mixing apparatus, there is almost no time for the liquid to stay in the mixing apparatus. On the other hand, the residence time in the tube was 15 minutes. In the coagulation apparatus, a certain amount of water vapor is blown from the bottom, and from the top, the mixed liquid descends along the wall. The latex coagulated with water vapor while falling down and separated into rubber and serum. The rubber coming out of the coagulator was sampled every 10 minutes, cooled with water, immersed in a 1 to 3% aqueous sodium bicarbonate solution for a whole day and night, then washed again with water and dried to a constant weight. The degree of epoxidation of this rubber was examined by NMR. As a result, the degree of epoxidation was 25.1, 25.3, 25.1, 25.4, 25.4, 25.7, 25.3, 25.5, confirming that they were very stable. .

Example 2
460 g of distilled water is added to 500 g of low ammonia natural rubber latex having a dry rubber content of 60% by weight (including 300 g of dry rubber), and 40 g of the 15% by weight surfactant (6.0 g of active ingredient) is added. And slowly stirred for 2 minutes.
This latex was fed into the mixing apparatus at a rate of 10.0 g / min using a tube pump (inner diameter of the tube 4 mm) whose amount of liquid was adjusted in advance. The size of the mixing device was 25 cc.
At the same time, the above-mentioned peracetic acid b was fed into the mixing apparatus so as to be 9.0 g / min. After sufficiently mixing them using a stirring blade in the mixing device, the solution is fed to the coagulation device by a tube pump (5 mm inner diameter of the tube) adjusted so that the amount of liquid feeding becomes 19.0 g / min (913 mm / min). did. The temperature of the mixed solution at the time of mixing was 25 ° C., and the temperature of the mixed solution at the time of feeding was 60 ° C. Since the liquid is hardly stored in the mixing apparatus, there is almost no time for the liquid to stay in the mixing apparatus. On the other hand, the residence time in the tube was 20 minutes. In the coagulation apparatus, a certain amount of water vapor is blown from the bottom, and from the top, the mixed liquid descends along the wall. The latex coagulated with water vapor while falling down and separated into rubber and serum. The rubber coming out of the coagulator was sampled every 10 minutes, cooled with water, immersed in a 1 to 3% aqueous sodium bicarbonate solution for a whole day and night, then washed again with water and dried to a constant weight. The degree of epoxidation of this rubber was examined by NMR. As a result, the degree of epoxidation was 35.2, 35.8, 35.1, 35.3, 35.4, 35.6, 35.0, 35.6, confirming that they were very stable. .

Example 3
460 g of distilled water is added to 500 g of low ammonia natural rubber latex having a dry rubber content of 60% by weight (including 300 g of dry rubber), and 40 g of the 15% by weight surfactant (6.0 g of active ingredient) is added. And slowly stirred for 2 minutes.
This latex was fed into the mixing apparatus at a rate of 10.0 g / min using a tube pump (inner diameter of the tube 4 mm) whose amount of liquid was adjusted in advance. The size of the mixing device was 25 cc.
At the same time, the above-mentioned peracetic acid b was fed into the mixing apparatus at 3.87 g / min. After sufficiently mixing them using a stirring blade in the mixing device, the solution is fed to the coagulation device by a tube pump (inner diameter of the tube 5 mm) adjusted so that the amount of feeding is 13.87 g / min (666 m / min). did. The temperature of the mixed solution at the time of mixing was 25 ° C., and the temperature of the mixed solution at the time of feeding was 50 ° C. Since the liquid is hardly stored in the mixing apparatus, there is almost no time for the liquid to stay in the mixing apparatus. On the other hand, the residence time in the tube was 30 minutes. In the coagulation apparatus, a certain amount of water vapor is blown from the bottom, and from the top, the mixed liquid descends along the wall. The latex coagulated with water vapor while falling down and separated into rubber and serum. The rubber coming out of the coagulator was sampled every 10 minutes, cooled with water, immersed in a 1 to 3% aqueous sodium bicarbonate solution for a whole day and night, then washed again with water and dried to a constant weight. The degree of epoxidation of this rubber was examined by NMR. As a result, the degree of epoxidation was 15.2, 15.5, 15.1, 15.6, 15.2, 15.4, 15.5, and it was confirmed that they were very stable.

Example 4
460 g of distilled water is added to 500 g of low ammonia natural rubber latex having a dry rubber content of 60% by weight (including 300 g of dry rubber), and 40 g of the 15% by weight surfactant (6.0 g of active ingredient) is added. And slowly stirred for 2 minutes.
This latex was fed into the mixing apparatus at a rate of 10.0 g / min using a tube pump (inner diameter of the tube 4 mm) whose amount of liquid was adjusted in advance. The size of the mixing apparatus was 100 cc.
At the same time, the above-mentioned peracetic acid a was fed into the mixing apparatus so as to be 7.6 g / min. After sufficiently mixing them using a stirring blade in the mixing apparatus, the liquid is fed to the coagulation apparatus by a tube pump (inner diameter of the tube 5 mm) adjusted so that the liquid feeding amount is 17.6 g / min (850 mm / min). did. The temperature of the mixed solution at the time of mixing was 25 ° C., and the temperature of the mixed solution at the time of feeding was 55 ° C. Since the pump was operated after the liquid was stored in the mixing apparatus so that the liquid was almost full, the average time for the liquid to stay in the mixing apparatus was about 5 minutes. On the other hand, the residence time in the tube was 6 minutes. In the coagulation apparatus, a certain amount of water vapor is blown from the bottom, and from the top, the mixed liquid descends along the wall. The latex coagulated with water vapor while falling down and separated into rubber and serum. The rubber coming out of the coagulator was sampled every 10 minutes, cooled with water, immersed in a 1 to 3% aqueous sodium bicarbonate solution for a whole day and night, then washed again with water and dried to a constant weight. The degree of epoxidation of this rubber was examined by NMR. As a result, the degree of epoxidation is 23.8, 24.2, 26.0, 25.1, 26.2, 24.6, 25.8, and the distribution of the degree of epoxidation is slightly wider than in Example 1. I found out.

Example 5
460 g of distilled water is added to 500 g of low ammonia natural rubber latex having a dry rubber content of 60% by weight (including 300 g of dry rubber), and 40 g of the 15% by weight surfactant (6.0 g of active ingredient) is added. And slowly stirred for 2 minutes.
This latex was fed into the mixing apparatus at a rate of 10.0 g / min using a tube pump (inner diameter of the tube 4 mm) whose amount of liquid was adjusted in advance. The size of the mixing apparatus was 200 cc.
At the same time, the above-mentioned peracetic acid a was fed into the mixing apparatus so as to be 7.6 g / min. After sufficiently mixing them using a stirring blade in the mixing apparatus, the liquid is fed to the coagulation apparatus by a tube pump (inner diameter of the tube 5 mm) adjusted so that the liquid feeding amount is 17.6 g / min (850 mm / min). did. The temperature of the mixed solution at the time of mixing was 25 ° C., and the temperature of the mixed solution at the time of feeding was 55 ° C. Since the pump was operated after the liquid was stored so that the liquid was almost full in the mixing apparatus, the average time for the liquid to stay in the mixing apparatus was about 11 minutes. On the other hand, the residence time in the tube was 2 minutes. In the coagulation apparatus, a certain amount of water vapor is blown from the bottom, and from the top, the mixed liquid descends along the wall. The latex coagulated with water vapor while falling down and separated into rubber and serum. The rubber coming out of the coagulator was sampled every 10 minutes, cooled with water, immersed in a 1 to 3% aqueous sodium bicarbonate solution for a whole day and night, then washed again with water and dried to a constant weight. The degree of epoxidation of this rubber was examined by NMR. As a result, the degree of epoxidation was 25.4, 26.8, 27.2, 24.2, 24.0, 25.1, 23.9, and the distribution of the degree of epoxidation was broader than in Examples 1 and 4. I found out.

Example 6
460 g of distilled water is added to 500 g of low ammonia natural rubber latex having a dry rubber content of 60% by weight (including 300 g of dry rubber), and 40 g of the 15% by weight surfactant (6.0 g of active ingredient) is added. And slowly stirred for 2 minutes.
This latex was fed into the mixing apparatus at a rate of 10.0 g / min using a tube pump (inner diameter of the tube 4 mm) whose amount of liquid was adjusted in advance. The size of the mixing device was 25 cc.
At the same time, the above-mentioned peracetic acid a was fed into the mixing apparatus so as to be 7.6 g / min. After sufficiently mixing them using a stirring blade in the mixing device, a coagulation device or a storage container by a tube pump (tube inner diameter 5 mm) adjusted so that the amount of liquid to be fed is 17.6 g / min (850 mm / min) The solution was sent to. The temperature of the mixed solution at the time of mixing was 25 ° C., and the temperature of the mixed solution at the time of feeding was 55 ° C. Since the liquid is hardly stored in the mixing apparatus, there is almost no time for the liquid to stay in the mixing apparatus. On the other hand, the residence time in the tube was 15 minutes. The latex coming out from the tube outlet is sampled every 10 minutes, coagulated in methanol, thinned with a roll, cooled with water, and immersed in an aqueous solution of 1 to 3% sodium bicarbonate for a day and night. After washing again with water, it was dried to a constant weight. The degree of epoxidation of this rubber was examined by NMR. As a result, the degree of epoxidation was 25.7, 25.6, 25.2, 25.9, 25.5, 25.3, 25.6, 25.7, confirming that they were very stable. .

Example 7
460 g of distilled water is added to 500 g of low ammonia natural rubber latex having a dry rubber content of 60% by weight (including 300 g of dry rubber), and 40 g of the 15% by weight surfactant (6.0 g of active ingredient) is added. And slowly stirred for 2 minutes.
This latex was fed into the mixing apparatus at a rate of 10.0 g / min using a tube pump (inner diameter of the tube 4 mm) whose amount of liquid was adjusted in advance. The size of the mixing device was 25 cc.
At the same time, the above-mentioned peracetic acid b was fed into the mixing apparatus so as to be 9.0 g / min. After sufficiently mixing them using a stirring blade in the mixing apparatus, a coagulation apparatus or a storage container with a tube pump (tube inner diameter 5 mm) adjusted so that the amount of liquid to be fed is 19.0 g / min (913 mm / min) The solution was sent to. The temperature of the mixed solution at the time of mixing was 25 ° C., and the temperature of the mixed solution at the time of feeding was 60 ° C. Since the liquid is hardly stored in the mixing apparatus, there is almost no time for the liquid to stay in the mixing apparatus. On the other hand, the residence time in the tube was 20 minutes. The latex coming out from the tube outlet is sampled every 10 minutes, coagulated in methanol, thinned with a roll, cooled with water, and immersed in an aqueous solution of 1 to 3% sodium bicarbonate for a day and night. After washing again with water, it was dried to a constant weight. The degree of epoxidation of this rubber was examined by NMR. As a result, the degree of epoxidation was 35.4, 35.5, 35.3, 35.6, 35.7, 35.4, 35.1, 35.4, confirming that they were very stable. .

Example 8
460 g of distilled water is added to 500 g of low ammonia natural rubber latex having a dry rubber content of 60% by weight (including 300 g of dry rubber), and 40 g of the 15% by weight surfactant (6.0 g of active ingredient) is added. And slowly stirred for 2 minutes.
This latex was fed into the mixing apparatus at a rate of 10.0 g / min using a tube pump (inner diameter of the tube 4 mm) whose amount of liquid was adjusted in advance. The size of the mixing device was 25 cc.
At the same time, the above-mentioned peracetic acid b was fed into the mixing apparatus at 3.87 g / min. After sufficiently mixing them using a stirring blade in the mixing device, a coagulation device or a storage container with a tube pump (tube inner diameter 5 mm) adjusted so that the amount of liquid to be fed is 13.87 g / min (666 mm / min) The solution was sent to. The temperature of the mixed solution at the time of mixing was 25 ° C., and the temperature of the mixed solution at the time of feeding was 50 ° C. Since the liquid is hardly stored in the mixing apparatus, there is almost no time for the liquid to stay in the mixing apparatus. On the other hand, the residence time in the tube was 30 minutes. The latex coming out from the tube outlet is sampled every 10 minutes, coagulated in methanol, thinned with a roll, cooled with water, and immersed in an aqueous solution of 1 to 3% sodium bicarbonate for a day and night. After washing again with water, it was dried to a constant weight. The degree of epoxidation of this rubber was examined by NMR. As a result, the degree of epoxidation was 15.1, 15.3, 15.3, 15.7, 15.6, 15.5, and 15.3, confirming that they were very stable.

Example 9
460 g of distilled water is added to 500 g of low ammonia natural rubber latex having a dry rubber content of 60% by weight (including 300 g of dry rubber), and 40 g of the 15% by weight surfactant (6.0 g of active ingredient) is added. And slowly stirred for 2 minutes.
This latex was fed into the mixing apparatus at a rate of 10.0 g / min using a tube pump (inner diameter of the tube 4 mm) whose amount of liquid was adjusted in advance. The size of the mixing apparatus was 100 cc.
At the same time, the above-mentioned peracetic acid a was fed into the mixing apparatus so as to be 7.6 g / min. After sufficiently mixing them using a stirring blade in the mixing device, a coagulation device or a storage container by a tube pump (tube inner diameter 5 mm) adjusted so that the amount of liquid to be fed is 17.6 g / min (850 mm / min) The solution was sent to. The temperature of the mixed solution at the time of mixing was 25 ° C., and the temperature of the mixed solution at the time of feeding was 55 ° C. Since the pump was operated after the liquid was stored in the mixing apparatus so that the liquid was almost full, the average time for the liquid to stay in the mixing apparatus was about 5 minutes. On the other hand, the residence time in the tube was 6 minutes. The latex coming out from the tube outlet is sampled every 10 minutes, coagulated in methanol, thinned with a roll, cooled with water, and immersed in an aqueous solution of 1 to 3% sodium bicarbonate for a day and night. After washing again with water, it was dried to a constant weight. The degree of epoxidation of this rubber was examined by NMR. As a result, the degree of epoxidation was 23.1, 24.6, 25.7, 25.5, 26.0, 24.8, 25.5, and the distribution of the degree of epoxidation was slightly wider than in Example 6. I found out.

Example 10
460 g of distilled water is added to 500 g of low ammonia natural rubber latex having a dry rubber content of 60% by weight (including 300 g of dry rubber), and 40 g of the 15% by weight surfactant (6.0 g of active ingredient) is added. And slowly stirred for 2 minutes.
This latex was fed into the mixing apparatus at a rate of 10.0 g / min using a tube pump (inner diameter of the tube 4 mm) whose amount of liquid was adjusted in advance. The size of the mixing apparatus was 200 cc.
At the same time, the above-mentioned peracetic acid a was fed into the mixing apparatus so as to be 7.6 g / min. After sufficiently mixing them using a stirring blade in the mixing device, a coagulation device or a storage container by a tube pump (tube inner diameter 5 mm) adjusted so that the amount of liquid to be fed is 17.6 g / min (850 mm / min) The solution was sent to. The temperature of the mixed solution at the time of mixing was 25 ° C., and the temperature of the mixed solution at the time of feeding was 55 ° C. Since the pump was operated after the liquid was stored so that the liquid was almost full in the mixing apparatus, the average time for the liquid to stay in the mixing apparatus was about 11 minutes. On the other hand, the residence time in the tube was 2 minutes. The latex coming out from the tube outlet is sampled every 10 minutes, coagulated in methanol, thinned with a roll, cooled with water, and immersed in an aqueous solution of 1 to 3% sodium bicarbonate for a day and night. After washing again with water, it was dried to a constant weight. The degree of epoxidation of this rubber was examined by NMR. As a result, the degree of epoxidation was 25.5, 27.0, 23.7, 24.7, 24.2, 26.1, 25.9, and the distribution of the degree of epoxidation was broader than in Examples 6 and 9. I found out.

Example 11
460 g of distilled water is added to 500 g of low ammonia natural rubber latex having a dry rubber content of 60% by weight (including 300 g of dry rubber), and 40 g of the 15% by weight surfactant (6.0 g of active ingredient) is added. And slowly stirred for 2 minutes.
This latex was fed into the mixing device at a rate of 60.0 g / min using a tube pump (inner diameter of the tube: 6.5 mm) whose amount of liquid was adjusted in advance. The size of the mixing device was 25 cc.
At the same time, the above-mentioned peracetic acid c was fed to the mixing apparatus so as to be 1.71 g / min. After sufficiently mixing them using a stirring blade in the mixing device, the tube pump (tube inner diameter 6.5 mm) adjusted so that the liquid feeding amount is 61.7 g / min (1753 mm / min) is added to the coagulation device. Liquid was sent. The temperature of the mixed solution at the time of mixing was 55 ° C., and the temperature of the mixed solution at the time of feeding was 60 ° C. Since the liquid is hardly stored in the mixing apparatus, there is almost no time for the liquid to stay in the mixing apparatus. On the other hand, the residence time in the tube was 12 minutes. In the coagulation apparatus, a certain amount of water vapor is blown from the bottom, and from the top, the mixed liquid descends along the wall. The latex coagulated with water vapor while falling down and separated into rubber and serum. The rubber coming out of the coagulator was sampled every 5 minutes, cooled with water, immersed in a 1 to 3% aqueous sodium bicarbonate solution for a whole day and night, then washed again with water and dried to a constant weight. The degree of epoxidation of this rubber was examined by NMR. As a result, the degree of epoxidation was 0.9, 1.0, and 1.0, confirming that they were very stable.

Example 12
460 g of distilled water is added to 500 g of low ammonia natural rubber latex having a dry rubber content of 60% by weight (including 300 g of dry rubber), and 40 g of the 15% by weight surfactant (6.0 g of active ingredient) is added. And slowly stirred for 2 minutes.
This latex was fed into the mixing device at a rate of 60.0 g / min using a tube pump (inner diameter of the tube: 6.5 mm) whose amount of liquid was adjusted in advance. The size of the mixing device was 25 cc.
At the same time, the above-mentioned peracetic acid c was fed to the mixing apparatus so as to be 8.6 g / min. After sufficiently mixing these using a stirring blade in the mixing device, the tube pump (tube inner diameter 6.5 mm) adjusted so that the amount of liquid to be fed is 68.6 g / min (2007 mm / min) is added to the coagulator. Liquid was sent. The temperature of the mixed solution at the time of mixing was 55 ° C., and the temperature of the mixed solution at the time of feeding was 60 ° C. Since the liquid is hardly stored in the mixing apparatus, there is almost no time for the liquid to stay in the mixing apparatus. On the other hand, the residence time in the tube was 12 minutes. In the coagulation apparatus, a certain amount of water vapor is blown from the bottom, and from the top, the mixed liquid descends along the wall. The latex coagulated with water vapor while falling down and separated into rubber and serum. The rubber coming out of the coagulator was sampled every 5 minutes, cooled with water, immersed in a 1 to 3% aqueous sodium bicarbonate solution for a whole day and night, then washed again with water and dried to a constant weight. The degree of epoxidation of this rubber was examined by NMR. As a result, the degree of epoxidation was 5.1, 5.0, 5.1, and it was confirmed that it was very stable.

Example 13
460 g of distilled water is added to 500 g of low ammonia natural rubber latex having a dry rubber content of 60% by weight (including 300 g of dry rubber), and 40 g of the 15% by weight surfactant (6.0 g of active ingredient) is added. And slowly stirred for 2 minutes.
This latex was fed into the mixing device at a rate of 60.0 g / min using a tube pump (inner diameter of the tube: 6.5 mm) whose amount of liquid was adjusted in advance. The size of the mixing device was 25 cc.
At the same time, the above-mentioned peracetic acid c was fed to the mixing apparatus at 17.1 g / min. After sufficiently mixing them using a stirring blade in the mixing device, the tube pump (tube inner diameter 6.5 mm) adjusted so that the liquid feeding amount becomes 77.1 g / min (2192 mm / min) is added to the coagulator. Liquid was sent. The temperature of the mixed solution at the time of mixing was 55 ° C., and the temperature of the mixed solution at the time of feeding was 60 ° C. Since the liquid is hardly stored in the mixing apparatus, there is almost no time for the liquid to stay in the mixing apparatus. On the other hand, the residence time in the tube was 12 minutes. In the coagulation apparatus, a certain amount of water vapor is blown from the bottom, and from the top, the mixed liquid descends along the wall. The latex coagulated with water vapor while falling down and separated into rubber and serum. The rubber coming out of the coagulator was sampled every 5 minutes, cooled with water, immersed in a 1 to 3% aqueous sodium bicarbonate solution for a whole day and night, then washed again with water and dried to a constant weight. The degree of epoxidation of this rubber was examined by NMR. As a result, the degree of epoxidation was 10.1, 10.3, 10.4, and it was confirmed that it was very stable.

Example 14
460 g of distilled water is added to 500 g of low ammonia natural rubber latex having a dry rubber content of 60% by weight (including 300 g of dry rubber), and 40 g of the 15% by weight surfactant (6.0 g of active ingredient) is added. And slowly stirred for 2 minutes.
This latex was fed into the mixing device at a rate of 60.0 g / min using a tube pump (inner diameter of the tube: 6.5 mm) whose amount of liquid was adjusted in advance. The size of the mixing device was 25 cc.
At the same time, the above-mentioned peracetic acid c was fed to the mixing apparatus so as to be 20.6 g / min. After sufficiently mixing them with a stirring blade in the mixing device, the tube pump (inner diameter of the tube 6.5 mm) adjusted so that the liquid feeding amount becomes 80.6 g / min (2358 mm / min) is added to the coagulator. Liquid was sent. The temperature of the mixed solution at the time of mixing was 45 ° C., and the temperature of the mixed solution at the time of feeding was 60 ° C. Since the liquid is hardly stored in the mixing apparatus, there is almost no time for the liquid to stay in the mixing apparatus. On the other hand, the residence time in the tube was 15 minutes. In the coagulation apparatus, a certain amount of water vapor is blown from the bottom, and from the top, the mixed liquid descends along the wall. The latex coagulated with water vapor while falling down and separated into rubber and serum. The rubber coming out of the coagulator was sampled every 5 minutes, cooled with water, immersed in a 1 to 3% aqueous sodium bicarbonate solution for a whole day and night, then washed again with water and dried to a constant weight. The degree of epoxidation of this rubber was examined by NMR. As a result, the degree of epoxidation was 12.1, 12.3, 12.4, and it was confirmed that they were very stable.

Example 15
460 g of distilled water is added to 500 g of low ammonia natural rubber latex having a dry rubber content of 60% by weight (including 300 g of dry rubber), and 40 g of the 15% by weight surfactant (6.0 g of active ingredient) is added. And slowly stirred for 2 minutes.
This latex was fed into the mixing device at a rate of 30.0 g / min using a tube pump (inner diameter of the tube: 6.5 mm) whose amount of liquid was adjusted in advance. The size of the mixing device was 25 cc.
At the same time, the above-mentioned peracetic acid c was fed to the mixing apparatus so as to be 21.4 g / min. After sufficiently mixing these using a stirring blade in the mixing device, the tube pump (inner diameter of tube 6.5 mm) adjusted so that the amount of liquid to be fed is 51.4 g / min (1461 mm / min) is added to the coagulator. Liquid was sent. The temperature of the mixed solution at the time of mixing was 30 ° C., and the temperature of the mixed solution at the time of feeding was 42 ° C. Since the liquid is hardly stored in the mixing apparatus, there is almost no time for the liquid to stay in the mixing apparatus. On the other hand, the residence time in the tube was 15 minutes. In the coagulation apparatus, a certain amount of water vapor is blown from the bottom, and from the top, the mixed liquid descends along the wall. The latex coagulated with water vapor while falling down and separated into rubber and serum. The rubber coming out of the coagulator was sampled every 5 minutes, cooled with water, immersed in a 1 to 3% aqueous sodium bicarbonate solution for a whole day and night, then washed again with water and dried to a constant weight. The degree of epoxidation of this rubber was examined by NMR. As a result, the epoxidation degrees were 24.9, 25.2, and 25.7, and it was confirmed that they were very stable.

Comparative Example 1
460 g of distilled water is added to 500 g of low ammonia natural rubber latex having a dry rubber content of 60% by weight (including 300 g of dry rubber), and 40 g of the 15% by weight surfactant (6.0 g of active ingredient) is added. And slowly stirred for 2 minutes.
This latex was fed into the mixing apparatus at a rate of 10.0 g / min using a tube pump (inner diameter of the tube 4 mm) whose amount of liquid was adjusted in advance. The size of the mixing device was 25 cc.
At the same time, the above-mentioned performic acid a was fed to the mixing apparatus so as to be 22.79 g / min. After sufficiently mixing them using a stirring blade in the mixing apparatus, the mixture was fed to the coagulation apparatus by a tube pump (inner diameter of the tube: 5 mm) adjusted so that the liquid feeding amount was 32.8 g / min. The temperature of the mixed solution at the time of mixing was 25 ° C., and the temperature of the mixed solution at the time of feeding was 25 ° C. Since the pump was operated so that almost no liquid was stored in the mixing apparatus, the time for the liquid to stay in the mixing apparatus was almost 0 minutes. On the other hand, the residence time in the tube was 20 minutes. In the coagulation apparatus, a certain amount of water vapor is blown from the bottom, and from the top, the mixed liquid descends along the wall. The latex coagulated with water vapor while falling down and separated into rubber and serum. This was cooled with water, immersed in a 1 to 3% aqueous solution of sodium hydrogen carbonate for a whole day and night, then washed again with water and dried to a constant weight. The rubber was sampled at 10 locations from the coagulum.
The degree of epoxidation of this rubber was examined by NMR. As a result, the degree of epoxidation was almost zero.

Comparative Example 2
440 g of distilled water is added to 500 g of low ammonia natural rubber latex having a dry rubber content of 60% by weight (of which 300 g of dry rubber is added), and 60 g of the 15% by weight surfactant (active ingredient 9 g) is added and slowly added with a spatula. And stirred for 2 minutes.
While stirring this with a stirrer, 52.3 g of formic acid (88%) was slowly added, and 93.5 g of hydrogen peroxide (50%) was further added using a tube pump over 3 hours. The temperature of the latex started from 40 ° C. and exceeded 60 ° C. as the reaction proceeded, so that the reaction was conducted while cooling the surroundings so that the temperature would be 60-65 ° C. Sampling was performed for 4 hours, 8 hours, and 24 hours from the start of the addition of the hydrogen peroxide solution, the rubber was coagulated with water vapor, neutralized and dried, and the degree of epoxidation was examined by NMR. As a result, the degree of epoxidation was 12.5 at 4 hours, 18.5 at 8 hours, and 25.4 at 24 hours. Although epoxidation is possible, it can be seen that it takes a very long time.

Comparative Example 3
440 g of distilled water is added to 500 g of low ammonia natural rubber latex having a dry rubber content of 60% by weight (of which 300 g of dry rubber is added), and 60 g of the 15% by weight surfactant (active ingredient 9 g) is added and slowly added with a spatula. And stirred for 2 minutes.
While stirring this with a stirrer, 61.2 g of acetic acid (98%) was slowly added, and 93.5 g of hydrogen peroxide (50%) was further added using a tube pump over 3 hours. The temperature of the latex started from 40 ° C. and exceeded 60 ° C. as the reaction proceeded, so that the reaction was conducted while cooling the surroundings so that the temperature would be 60-65 ° C. Sampling was performed for 4 hours, 8 hours, and 24 hours from the start of the addition of the hydrogen peroxide solution, the rubber was coagulated with water vapor, neutralized and dried, and the degree of epoxidation was examined by NMR. As a result, the degree of epoxidation was 1 in 4 hours, 3 in 8 hours, and 5 in 24 hours. It can be seen that epoxidation hardly proceeds by the same method as in Comparative Example 2.

Comparative Example 4
460 g of distilled water is added to 500 g of low ammonia natural rubber latex having a dry rubber content of 60% by weight (including 300 g of dry rubber), and 40 g of the 15% by weight surfactant (6.0 g of active ingredient) is added. And slowly stirred for 2 minutes.
This latex was fed into the mixing apparatus at a rate of 10.0 g / min using a tube pump (inner diameter of the tube 4 mm) whose amount of liquid was adjusted in advance. The size of the mixing device was 25 cc.
At the same time, the above-mentioned performic acid a was fed to the mixing apparatus so as to be 22.79 g / min. After sufficiently mixing them using a stirring blade in the mixing apparatus, the mixture was fed to the coagulation apparatus by a tube pump (inner diameter of the tube: 5 mm) adjusted so that the liquid feeding amount was 32.8 g / min. The temperature of the mixed solution at the time of mixing was 25 ° C., and the temperature of the mixed solution at the time of feeding was 25 ° C. Since the pump was operated so that almost no liquid was stored in the mixing apparatus, the time for the liquid to stay in the mixing apparatus was almost 0 minutes. On the other hand, the residence time in the tube was 20 minutes. The latex coming out from the tube outlet is sampled 10 times, coagulated in methanol, thinned with a roll, cooled with water, immersed in a 1 to 3% aqueous solution of sodium hydrogen carbonate overnight, and then washed again with water. Then, it dried until it became constant weight. The degree of epoxidation of this rubber was examined by NMR. As a result, the degree of epoxidation was almost zero.

Comparative Example 5
440 g of distilled water is added to 500 g of low ammonia natural rubber latex having a dry rubber content of 60% by weight (of which 300 g of dry rubber is added), and 60 g of the 15% by weight surfactant (active ingredient 9 g) is added and slowly added with a spatula. And stirred for 2 minutes.
While stirring this with a stirrer, 52.3 g of formic acid (88%) was slowly added, and 93.5 g of hydrogen peroxide (50%) was further added using a tube pump over 3 hours. The temperature of the latex started from 40 ° C. and exceeded 60 ° C. as the reaction proceeded, so that the reaction was conducted while cooling the surroundings so that the temperature would be 60-65 ° C. Sampling was performed for 4 hours, 8 hours, and 24 hours from the start of addition of the hydrogen peroxide solution, and the rubber was solidified in methanol, neutralized and dried, and the degree of epoxidation was examined by NMR. As a result, the degree of epoxidation was 12.0 at 4 hours, 17.8 at 8 hours, and 24.9 at 24 hours. Although epoxidation is possible, it can be seen that it takes a very long time.

Comparative Example 6
440 g of distilled water is added to 500 g of low ammonia natural rubber latex having a dry rubber content of 60% by weight (of which 300 g of dry rubber is added), and 60 g of the 15% by weight surfactant (active ingredient 9 g) is added and slowly added with a spatula. And stirred for 2 minutes.
While stirring this with a stirrer, 61.2 g of acetic acid (98%) was slowly added, and 93.5 g of hydrogen peroxide (50%) was further added using a tube pump over 3 hours. The temperature of the latex started from 40 ° C. and exceeded 60 ° C. as the reaction proceeded, so that the reaction was conducted while cooling the surroundings so that the temperature would be 60-65 ° C. Sampling was performed for 4 hours, 8 hours, and 24 hours from the start of addition of the hydrogen peroxide solution, and the rubber was solidified in methanol, neutralized and dried, and the degree of epoxidation was examined by NMR. As a result, the degree of epoxidation was approximately 0 in 4 hours, 2 in 8 hours, and 3 in 24 hours. It can be seen that the epoxidation hardly proceeds by the same method as in Comparative Example 5.

Comparative Example 7
460 g of distilled water is added to 500 g of low ammonia natural rubber latex having a dry rubber content of 60% by weight (including 300 g of dry rubber), and 40 g of the 15% by weight surfactant (6.0 g of active ingredient) is added. And slowly stirred for 2 minutes.
This latex was fed into the mixing device at a rate of 60.0 g / min using a tube pump (inner diameter of the tube: 6.5 mm) whose amount of liquid was adjusted in advance. The size of the mixing device was 25 cc.
At the same time, the above-mentioned performic acid b was fed to the mixing apparatus so as to be 42.1 g / min. After sufficiently mixing them using a stirring blade in the mixing apparatus, the mixture was fed to the coagulation apparatus by a tube pump (inner diameter of the tube: 6.5 mm) adjusted so that the liquid feeding amount was 102.1 g / min. The temperature of the mixed solution at the time of mixing was 25 ° C., and the temperature of the mixed solution at the time of feeding was 25 ° C. Since the liquid was hardly stored in the mixing apparatus, the time for the liquid to stay in the mixing apparatus was almost 0 minutes. On the other hand, the residence time in the tube was 20 minutes. In the coagulation apparatus, a certain amount of water vapor is blown from the bottom, and from the top, the mixed liquid descends along the wall. The latex coagulated with water vapor while falling down and separated into rubber and serum. This was cooled with water, immersed in a 1 to 3% aqueous solution of sodium hydrogen carbonate for a whole day and night, then washed again with water and dried to a constant weight. The rubber was sampled from the coagulum at five locations. The degree of epoxidation of this rubber was examined by NMR. As a result, the degree of epoxidation was almost zero.

Comparative Example 8
440 g of distilled water is added to 500 g of low ammonia natural rubber latex having a dry rubber content of 60% by weight (of which 300 g of dry rubber is added), and 60 g of the 15% by weight surfactant (active ingredient 9 g) is added and slowly added with a spatula. And stirred for 2 minutes.
While stirring this with a stirrer, 7.84 g of formic acid (88%) was slowly added, and 34 g of hydrogen peroxide (30%) was added using a tube pump over 3 hours. The temperature of the latex started from 40 ° C. and exceeded 60 ° C. as the reaction proceeded, so that the reaction was conducted while cooling the surroundings so that the temperature would be 60-65 ° C. Sampling was performed for 4 hours, 8 hours, 20 hours, 24 hours, and 27 hours from the start of addition of the hydrogen peroxide solution, the rubber was coagulated with water vapor, neutralized and dried, and the degree of epoxidation was examined by NMR. As a result, the degree of epoxidation was 1.5 at 4 hours, 3.2 at 8 hours, 4.6 at 20 hours, 4.9 at 24 hours, and 5.1 at 27 hours. It can be seen that epoxidation proceeds slowly and reliably, but is very time consuming.

Claims (14)

(A) preparing peracetic acid from acetic acid and / or acetic anhydride and hydrogen peroxide;
(B) mixing while continuously supplying the peracetic acid and natural rubber latex; and
(C) A method for producing a modified natural rubber latex, comprising a step of continuously transporting the mixed liquid, and epoxidizing the natural rubber latex in at least the step (c). The method for producing a modified natural rubber latex according to claim 1, wherein in step (b), the peracetic acid and the natural rubber latex are mixed in a flow path. In the step (b), the peracetic acid and the natural rubber latex are respectively supplied into a container and mixed in the container, The method for producing a modified natural rubber latex according to claim 1 or 2. The method for producing a modified natural rubber latex according to any one of claims 1 to 3, wherein a dry rubber content in the natural rubber latex is 5 to 67% by weight. The method for producing a modified natural rubber latex according to any one of claims 1 to 4, wherein the step (c) is a step of continuously transporting the mixed liquid using a pipe. The method for producing a modified natural rubber latex according to any one of claims 1 to 5, wherein 50% or more of the epoxidation reaction carried out in all steps is carried out in the step (c). (A) preparing peracetic acid from acetic acid and / or acetic anhydride and hydrogen peroxide;
(B) mixing the peracetic acid and natural rubber latex while continuously supplying them,
(C) a step of continuously transporting the mixed liquid to step (d), and
(D) A method for producing a modified natural rubber comprising a step of coagulating an epoxidized natural rubber latex, wherein the natural rubber latex is epoxidized in at least the step (c). The method for producing a modified natural rubber according to claim 7 , wherein in step (b), the peracetic acid and the natural rubber latex are mixed in a flow path. The method for producing a modified natural rubber according to claim 7 or 8 , wherein in step (b), the peracetic acid and the natural rubber latex are respectively supplied into a container and mixed in the container. The method for producing a modified natural rubber according to any one of claims 7 to 9 , wherein in step (d), the acid remaining in the rubber after coagulation is neutralized with a basic substance. The modified natural rubber according to any one of claims 7 to 10 , wherein the step (d) is performed without storing the epoxidized natural rubber latex transported in the step (c) in a tank. Production method. The method for producing a modified natural rubber according to any one of claims 7 to 11 , wherein a dry rubber content in the natural rubber latex is 5 to 67% by weight. The modified natural rubber according to any one of claims 7 to 12, wherein the step (c) is a step of continuously transporting the mixed liquid to the step (d) using a pipe. Manufacturing method. The method for producing a modified natural rubber according to any one of claims 7 to 13, wherein 50% or more of the epoxidation reaction carried out in all steps is carried out in the step (c).