WO2013105320A1

WO2013105320A1 - Method for manufacturing latex foam

Info

Publication number: WO2013105320A1
Application number: PCT/JP2012/076512
Authority: WO
Inventors: 高井　淳; 芳明宮本
Original assignee: 住友ゴム工業株式会社
Priority date: 2012-01-11
Filing date: 2012-10-12
Publication date: 2013-07-18
Also published as: JP5351983B2; JP2013142116A

Abstract

The present invention provides a method for manufacturing latex foam that can manufacture latex foam in which bubbles have been made small to a sufficient level using a simple device with excellent productivity with few steps and in a short time. A stirring tank (8) is disposed such that a center axis (L2) is vertical. Rubber or resin latex is accommodated in the stirring tank (8), and a disk turbine fin (1) having an axis of rotation (L1) in the vertical direction is immersed in the latex. Letting D be the inside diameter of the stirring tank (8) and h be the distance between the center part in the direction of the height of the disk turbine fin and the liquid surface of the latex, the depth of immersion is set to a depth that satisfies the ratio h/D being 0.5 - 1.5. Moreover, a disk turbine fin (1) that has a disk (3) that rotates horizontally and a plurality of flat plate shaped fin bodies (4) attached radially in the direction of the periphery of the disk (3) so as to be orthogonal to the disk (3) is used.

Description

Method for producing latex foam

The present invention relates to a production method for producing latex foam by foaming rubber or resin latex by stirring.

Rubber and resin latexes are excellent in processability for processing into various article shapes, and can form articles excellent in strength and the like. For this reason, it is widely used as a forming material in various applications such as rubber gloves (including rubber gloves and resin gloves, the same applies hereinafter).
For example, by immersing a mold corresponding to the three-dimensional shape of a rubber glove in the latex and pulling it up, after attaching the latex to the surface of the mold, in the case of rubber latex, the mold is heated and vulcanized together with the resin. In the case of this latex, the rubber gloves corresponding to the three-dimensional shape of the mold can be produced by drying and then curing as necessary and then removing from the mold.

Moreover, when latex is foamed by stirring to form a latex foam containing air, and the latex foam is used as a material for forming an article such as a rubber glove, the formed article has a porous structure and improves properties such as flexibility. Or providing new characteristics such as liquid absorbency, and further, the weight of the article can be reduced.
The added value of an article formed using latex foam is determined by the size (average bubble diameter) and amount (bubble content) of bubbles contained in the article. Therefore, it is important to control the average bubble diameter and bubble content of the latex foam that affects these.

In particular, the average bubble diameter is important, and the smaller the average bubble diameter, the denser the bubbles, the more the relative bubble surface area can be increased when compared with the same bubble content while maintaining the strength of the article in an appropriate range. Therefore, characteristics such as liquid absorbency due to the porous structure can be further improved.
For example, in rubber gloves, wet grip properties can be improved by imparting liquid absorbency with a porous structure on the surface. At that time, it is preferable that the average bubble diameter of the latex foam as the forming material is small because the average bubble diameter of the rubber glove to be formed can be reduced and the liquid absorbency is improved. Specifically, the average cell diameter is preferably 300 μm or less, and more preferably about 100 μm or less.

However, from the viewpoint of processability, strength of the article, etc., the bubble content of the latex foam is preferably as small as possible. Specifically, the bubble content is preferably 60% by volume or less, and more preferably about 40% by volume or less.
Methods for foaming latex are roughly classified into chemical foaming and physical foaming.
Among these, the chemical foaming method uses a foaming agent that generates gas by heating or chemical reaction. By blending a foaming agent in the latex, gas is generated from the foaming agent by heating or the like, and the latex is included in the latex, the latex can be foamed.

In addition, as the physical foaming method, for example, a method of blowing air directly into the latex, or stirring and foaming the latex, that is, by mixing the lower latex (liquid) and the upper air from the liquid level by gas-liquid mixing, A method of including air as bubbles in latex is known.
In general, the physical foaming method has the advantage that the material cost can be reduced by the amount that does not require a foaming agent compared with the chemical foaming method, but it is difficult to control the average bubble diameter and bubble content of latex foam. Yes.

In order to solve this problem, various methods have been studied.
For example, in Patent Document 1, it has been studied to disperse the generated bubbles by stirring them using a stirrer equipped with a propeller blade as a stirring blade after bubbling gas into latex. In Patent Document 2, it is considered that the latex is stirred and foamed using a continuous mechanical foaming machine, a home mixer, or the like.

According to these methods, it is considered that the bubbles in the latex can be made finer to some extent than usual.
However, according to the inventor's study, these methods may not be able to reduce the bubbles to a sufficient level, for example, a level capable of imparting good liquid absorbency to the rubber glove as described above. In addition, the number of processes increases and the apparatus becomes complicated, and the time required for the work becomes long, resulting in a decrease in latex foam productivity and an increase in production cost.

JP 2011-1662 A JP 2007-231428 A

An object of the present invention is to provide a method for producing a latex foam, which can produce a latex foam with fine bubbles to a sufficient level, with a simpler apparatus, with fewer steps and a shorter working time with high productivity. There is.

In order to solve the above-mentioned problems, the inventor conducted various studies on a stirrer used for foaming latex by stirring.
As a result, as a stirring blade attached to the stirring shaft of the stirrer, a disc (disk) attached to the stirring shaft perpendicular to the direction of the central axis of the stirring shaft, and the stirring shaft in the circumferential direction of the disc It has been found that it is sufficient to use a disk turbine blade having a plurality of flat blade bodies that are radially attached to the center and are mounted perpendicular to the disk.

That is, when the latex is stirred using a stirrer in which a disk turbine blade is attached to a stirring shaft, not only can the bubbles be generated in the latex by gas-liquid mixing, but the generated bubbles are also transferred from the blade body to the latex. It can also be finely dispersed by a strong shearing force applied to.
For this reason, the latex can be foamed more finely in a short time without the need for other processes, simply by using a stirrer equipped with a disk turbine blade, and the bubbles are refined to a sufficient level. Latex foam can be produced with higher productivity than ever.

Accordingly, the invention of claim 1 is a method for producing a latex foam, comprising a step of preparing a bottomed cylindrical stirring tank arranged so that a central axis is vertical, and a latex of rubber or resin in the stirring tank A step of immersing a disc turbine blade having a rotating shaft in a vertical direction in the latex accommodated in the agitation tank, and stirring the latex by rotating the disc turbine blade at a constant speed for a certain period of time. A method for producing a latex foam, comprising: a step; and a step of pulling up the disk turbine blade after the rotation is stopped from within the latex.

According to a second aspect of the present invention, the disk turbine blade is attached to a disk that rotates horizontally around a rotation axis, and to the circumferential direction of the disk, radially about the rotation axis and orthogonal to the disk. The method for producing a latex foam according to claim 1, comprising a plurality of flat wing bodies.
According to a third aspect of the present invention, in the step of stirring the latex, the rotational speed of the disk turbine blade is 100 m / min or more as expressed by the linear velocity at the radially outer tip of the blade body. A method for producing latex foam.

The invention according to claim 4 is the latex foam according to claim 2, wherein the rotational speed of the disk turbine blade is 250 m / min or more in terms of the linear velocity at the radially outer tip of the blade body. It is a manufacturing method.
The invention of claim 5 is characterized in that the rotational speed of the disk turbine blade is 500 m / min or less, expressed by the linear velocity at the radially outer tip of the blade body. It is a manufacturing method of latex foam given in one paragraph.

The invention of claim 6 is characterized in that the rotational speed of the disk turbine blade is 450 m / min or less in terms of the linear velocity at the radially outer tip of the blade body. The method for producing a latex foam according to the item.
The invention according to claim 7 is the method for producing latex foam according to claim 1, wherein the time for rotating the disk turbine blade in the step of stirring the latex is from 30 minutes to 2 hours.

By these inventions, it is possible to produce a latex foam in which bubbles are refined to a sufficient level in a short time efficiently by applying a strong shearing force to the latex from the blade body of the disk turbine blade.
Further, according to the invention of claim 11, in the step of immersing the disc turbine blade, the inner diameter of the agitating tank is set to D and the central portion in the height direction of the disc turbine blade immersed so that the rotation axis extends in the vertical direction and the liquid of the latex. 2. The immersion depth is adjusted so that the ratio h / D is in a range satisfying 0.5 or more and 1.5 or less, where h is the distance to the surface. This is a method for producing a latex foam.

In the invention of claim 12, the ratio d / D, where D is the inner diameter of the stirring tank and d is the maximum diameter of the disk turbine blade (the dimension from the blade tip to the opposite blade tip through the rotation center). 2. The latex foam according to claim 1, wherein the maximum diameter d of the disk turbine blade and the inner diameter D of the stirring tank are set so that the pressure is in the range of 0.3 to 0.4. It is a manufacturing method.

According to these inventions, when the ratio h / D that defines the amount of immersion of the disk turbine blade in the latex is less than 0.5, the amount of immersion is not sufficient, and the disk turbine blade is considerably on the liquid surface of the latex. It will rotate at a close position.
Therefore, there is a tendency that the degree of gas-liquid mixing by stirring tends to be too strong, the bubble content of the latex foam becomes excessively high, and the workability when processing into the shape of an article using the latex foam as a forming material is high There is a possibility that the strength of the article to be formed may be reduced.

On the other hand, when the ratio h / D exceeds 1.5, the amount of immersion becomes excessive, and the disk turbine blade rotates at a position considerably deeper than the liquid level of the latex.
Therefore, there is a tendency that the degree of gas-liquid mixing by stirring tends to be too weak, and the bubble content of the latex foam becomes excessively low, and an article excellent in desired properties such as liquid absorbability may not be obtained.

On the other hand, when the ratio h / D is within the range of 0.5 or more and 1.5 or less, the amount of immersion of the disk turbine blade in the latex and the degree of gas-liquid mixing by stirring are in an appropriate range. Can be maintained.
For this reason, the bubble content of the latex foam is set within a suitable range to further improve the workability, and further improve the properties such as strength and liquid absorbency of articles formed using the latex foam. It becomes possible to do.

ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method for manufacturing the latex foam refined | miniaturized to sufficient level to a sufficient level with high productivity by a fewer process and short working time using a simpler apparatus can be provided. It becomes possible.

It is a perspective view which shows the external appearance of an example of the disc turbine blade used with the manufacturing method of the latex foam of this invention. It is sectional drawing which shows an example of the process of foaming latex using the disk turbine blade of the example of the said FIG. 1 among the manufacturing methods of the latex foam of this invention.

FIG. 1 is a perspective view showing an appearance of an example of a disk turbine blade used in the method for producing a latex foam of the present invention.
Referring to FIG. 1, a disc turbine blade 1 of this example is attached to and can be removed from a stirring shaft 2 of a stirrer (not shown) in a state orthogonal to the direction of the central axis L1 of the stirring shaft 2. A disc 3 and a plurality of (six in this example) wing bodies 4 provided at equal intervals in the circumferential direction of the disc 3 are provided. The wing body 4 has a rectangular flat plate shape that is attached radially to the stirring shaft 2 and orthogonal to the disc 3.

At the center of the disc 3, a cylindrical boss 6 having a through hole 5 through which the inner diameter thereof substantially coincides with the outer diameter of the stirring shaft 2 and through which the stirring shaft 2 is inserted is integrally provided. The disc 3, the boss 6 and the through hole 5 are provided concentrically with each other. The disc 3 is provided integrally with the boss 6 in a direction orthogonal to the direction of the boss 6 and the central axis of the through-hole 5 (which coincides with the central axis L1 of the stirring shaft 2 in the figure).

A screw hole 7 is passed through the boss 6 from the outer peripheral surface to the inner peripheral surface facing the through hole 5.
With the stirring shaft 2 inserted into the through hole 5 of the boss 6, a screw (not shown) is screwed into the screw hole 7 and tightened to tighten the disc 3 in the direction of the central axis L 1 of the stirring shaft 2. It can be fixed in an orthogonal state. Moreover, the disc 3 can be removed from the stirring shaft 2 by loosening the tightening of the screw.

Although the disk turbine blade 1 in the example shown in the figure includes six blade bodies 4, the number of blade bodies 4 can be arbitrarily set.
As the number of the wing bodies 4 increases, the effect of refining the bubbles by the shearing force is improved. On the other hand, however, a large rotational torque is required to rotate the disk turbine blade 1 at a predetermined rotational speed. Therefore, the number of the wing bodies 4 is preferably about 4 or more and 6 or less.

Further, although the shape and size of each wing body 4 are not particularly limited, the shape of the wing body 4 is a rectangular flat plate shape as shown in the figure in consideration of applying a shearing force to latex to make bubbles finer. Is preferred.
In addition, the larger the dimensions of each side of the rectangular flat blade body 4, the more the bubbles can be made finer by applying shear force to the latex. On the other hand, in order to rotate the disk turbine blade 1 at a predetermined rotational speed, Requires a large rotational torque. Therefore, the dimensions of both the vertical and horizontal sides are 0.2 times or more the maximum diameter d of the disk turbine blade 1 (the dimension from the tip of the blade body 4 to the tip of the opposite blade body 4 through the central axis L1), It is preferably about 0.3 times or less.

FIG. 2 is a cross-sectional view showing a process of foaming latex in a batch-type open stirring tank using the disk turbine blade 1 of FIG. 1 in the latex foam production method of the present invention.
Referring to FIG. 2, stirring tank 8 has a cylindrical shape having a constant inner diameter D, and is disposed with its central axis L2 facing in the vertical direction. The upper end of the stirring tank 8 in the vertical direction is an opening 9 and the lower end is closed as a bottom 10. That is, the stirring tank 8 has a bottomed cylindrical shape.

In this step, first, a predetermined amount of latex 11 that becomes the basis of the latex foam is accommodated in the stirring vessel 8.
Next, referring to FIGS. 1 and 2, the central axis L <b> 2 of the stirring tank 8 and the central axis L <b> 1 of the stirring shaft 2 of the stirrer (not shown) coincide with each other in the stirring tank 8. In addition, the stirring shaft 2 having the disk turbine blade 1 attached to the tip is immersed in the latex 11.

At this time, the distance from the liquid surface 12 of the latex 11 before stirring to the disk 3 of the disk turbine blade 1 (distance to the center in the height direction of the disk turbine blade 1) h (center axis L1, L2 direction (vertical) The immersion depth is set so that the distance h) in the direction) is in a range satisfying 0.5 or more and 1.5 or less, expressed as a ratio h / D with the inner diameter D of the stirring tank 8.
If the ratio h / D is less than 0.5, the immersion depth of the disk turbine blade 1 in the latex 11 is not sufficient, and the disk turbine blade 1 rotates at a position that is considerably close to the liquid surface 12 of the latex 11. become.

Therefore, there is a tendency that the degree of gas-liquid mixing by stirring tends to be too strong, the bubble content of the latex foam becomes excessively high, and the workability when processing into the shape of an article using the latex foam as a forming material is high There is a possibility that the strength of the article to be formed may be reduced.
On the other hand, when the ratio h / D exceeds 1.5, the immersion depth becomes too deep, and the disc turbine blade 1 rotates at a position considerably deeper than the liquid surface 12 of the latex 11.

Therefore, there is a tendency that the degree of gas-liquid mixing by stirring tends to be too weak, and the bubble content of the latex foam becomes excessively low, and an article excellent in desired properties such as liquid absorbability may not be obtained.
On the other hand, when the ratio h / D is in the range of 0.5 or more and 1.5 or less, the immersion depth of the disk turbine blade 1 in the latex 11 and the degree of gas-liquid mixing by stirring are in an appropriate range. Can be maintained.

For this reason, the bubble content of the latex foam is set within a suitable range, the workability is further improved, and the properties such as strength and liquid absorbency of articles formed using the latex foam are further improved. It is possible to make it.
In addition, it is preferable that ratio h / d is 0.7 or more also in the said range, and it is preferable that it is 1.0 or less.

The blade diameter d of the disk turbine blade 1 can be arbitrarily set according to the size of the stirring tank 8. However, considering the stirring efficiency, the blade diameter d and the stirring tank 8 are set so that the ratio d / D between the blade diameter d and the inner diameter D of the stirring tank 8 is in the range of 0.3 to 0.4. It is preferable to set the inner diameter D of the.
Further, in the example of the figure, only one disk turbine blade 1 is attached to the tip of the stirring shaft 2, but depending on the depth of the stirring tank 8, the amount of latex 11 accommodated in the stirring tank 8, etc. Two or more disk turbine blades 1 may be attached to one stirring shaft 2 in the axial direction thereof.

In that case, what is necessary is just to set so that the immersion depth of the disc turbine blade 1 attached to the upper side of the stirring shaft 2 near the liquid level 12 of the latex 11 may satisfy the range of the ratio h / D.
Next, in the immersed state, the stirring shaft 2 (not shown) is rotated, and the latex 11 is stirred by the disk turbine blade 1 attached to the tip of the stirring shaft 2.

Then, the lower latex 11 from the liquid level 12 and the upper air are gas-liquid mixed by stirring, and air is included in the latex 11 as bubbles, and the bubbles are transferred from the blade body 4 of the disk turbine blade 1 to the latex 11. Can be finely dispersed by a strong shearing force applied to.
Therefore, only by stirring, latex can be finely foamed in a short time without the need for other steps, and latex foam with fine bubbles to a sufficient level is produced with high productivity. Can do.

The rotational speed of the agitation shaft 2 is preferably set to 100 m / min or more, particularly 250 m / min or more in terms of the linear velocity of the disk turbine blade 1 at the radially outer tip 13 of the blade body 4.
By setting the linear velocity within the above range, a strong shearing force is applied to the latex 11 from the blade body 4 of the disk turbine blade 1, and a latex foam in which the bubbles are refined to a sufficient level in a short time is manufactured. It becomes possible.

The linear velocity is 500 m / min or less, particularly 450 m / min or less, taking into account that the degree of gas-liquid mixing by stirring becomes too strong and the bubble content of the latex foam is prevented from becoming excessively high. It is preferable to set.
The stirring time, temperature, and the like can be arbitrarily set according to the type and viscosity of the latex to be stirred.

Among these, the stirring temperature (latex liquid temperature) is about room temperature (5 to 35 ° C.) in consideration of foaming while preventing the rubber in the latex from being completely vulcanized during stirring. Is preferred.
Further, the time for stirring is preferably 30 minutes or longer, and preferably 2 hours or shorter in consideration of making the bubbles fine enough to a sufficient level.

As the latex that is the basis of the latex foam to be produced, various latexes that can be used as a forming material for various articles, including various rubbers and resins, can be used.
Examples of the rubber latex include one or more of natural rubber latex, deproteinized natural rubber latex, nitrile rubber (acrylonitrile-butadiene rubber) latex, styrene-butadiene rubber latex, chloroprene rubber latex, and the like.

For rubber latex, in addition to vulcanizing agents (sulfur, etc.) for vulcanizing rubber, vulcanization accelerators, vulcanization accelerators (titanium oxide, etc.), anti-aging agents, fillers, dispersants, stability You may mix | blend various additives, such as an agent and surfactant.
Further, a foaming agent, a microcapsule, a foaming agent, or the like may be blended, and the latex may be foamed by stirring and foamed by a chemical foaming method using a foaming agent or the like.

Examples of the resin latex include one or more emulsions (latex) of a resin that can be emulsified (latexed), such as a vinyl chloride resin, a urethane resin, and an acrylic resin.
Various additives such as an antioxidant, a filler, a dispersant, a stabilizer, and a surfactant may be further added to the latex of the resin.

Further, in the same manner as rubber latex, a foaming agent, microcapsules, a foaming agent and the like may be blended and foamed by stirring, and foamed by a chemical foaming method using a foaming agent or the like.
According to the present invention, it is possible to produce a latex foam in which bubbles are refined to a sufficient level only by stirring a rubber or resin latex using a disk turbine blade in a short working time with high productivity. Become.

Hereinafter, the present invention will be described more specifically based on examples and comparative examples, but the configuration of the present invention is not limited to these examples. In addition, manufacture of the latex foam of an Example and a comparative example was implemented in 23 degreeC environment.
<Example 1>
(Latex preparation)
For natural rubber latex, 0.5 parts by mass of ammonia casein, 1 part by mass of potassium oleate, 1 part by mass of potassium hydroxide, 1 part by mass of sulfur, and dibutyl per 100 parts by mass of rubber (solid content) in the natural rubber latex 1 part by mass of zinc carbamate, 0.5 part by mass of zinc oxide, and 3 parts by mass of titanium oxide were blended to prepare a latex as a raw material for latex foam. In addition, what was supplied in aqueous solution among the said each component described the quantity of the active ingredient in it.

(Stirring process)
As shown in FIG. 2, the stirring tank 8 for storing the latex has a cylindrical shape with an inner diameter D of 140 cm, and its central axis L2 is arranged in the vertical direction, and the upper end in the vertical direction is an opening 9. And having a capacity of 500 L with the lower end closed as the bottom 10.
As the stirring blade, as shown in FIGS. 1 and 2, a disc 3 attached to the stirring shaft 2 so as to be orthogonal to the direction of the central axis L <b> 1 of the stirring shaft 2, the circumferential direction of the disc 3, etc. A disc turbine blade 1 having six blades 4 having a rectangular plate shape, which is provided at intervals, is radially centered on the agitation shaft 2 and is mounted perpendicularly to the disc 3, and has a blade diameter d of 50 cm. Was used.

The ratio d / D between the blade diameter d and the inner diameter D of the stirring tank 8 is 0.36.
The disc turbine blade 1 attached to the tip of the stirring shaft 2 was immersed in the latex 11 so that the distance h from the liquid surface 12 of the latex 11 before stirring to the disk 3 was 120 cm.
The ratio h / D between the distance h and the inner diameter D of 8 of the stirring vessel is 0.86.

Next, the stirring shaft 2 was rotated at a rotation speed of 200 rpm and stirred for 1 hour to foam the latex, thereby producing a latex foam.
The linear velocity of the radially outer tip 13 of the blade body 4 of the disk turbine blade 1 during stirring was 314 m / min.
<Example 2>
A latex foam was produced in the same manner as in Example 1 except that the rotation speed of the stirring shaft 2 was 60 rpm, and the linear velocity of the radial outer tip 13 of the blade body 4 of the disk turbine blade 1 was 94 m / min.

The ratio d / D is 0.36, which is the same as in Example 1, and the ratio h / D is also 0.86, which is the same as in Example 1.
<Example 3>
A latex foam was prepared in the same manner as in Example 1 except that the disk turbine blade 1 was immersed in the latex 11 so that the distance h from the liquid surface 12 of the latex 11 before stirring to the disk 3 was 60 cm. Manufactured.

The ratio d / D is 0.36, the same as in Example 1, and the ratio h / D is 0.43.
<Example 4>
A latex foam was prepared in the same manner as in Example 1 except that the disk turbine blade 1 was immersed in the latex 11 so that the distance h from the liquid surface 12 of the latex 11 before stirring to the disc 3 was 210 cm. Manufactured.

The ratio d / D is 0.36, the same as in Example 1, and the ratio h / D is 1.5.
<Comparative example 1>
Instead of the disk turbine blade 1, three blades having a substantially elliptical shape and twisted are fixed to a cylindrical boss by being inclined with respect to the direction of the central axis L1, and the blade diameter d is 50 cm. The three-blade propeller blade was used.

The propeller blade was immersed in the latex 11 so that the distance h from the liquid level 12 of the latex 11 before stirring to the boss of the propeller blade to the attachment portion of each blade was 60 cm.
The ratio d / D is 0.36, which is the same as in Example 1, and the ratio h / D is 0.43, which is the same as in Example 3.
In this state, the stirrer was driven, the stirring shaft 2 was rotated at a rotation speed of 200 rpm, and stirred for 1 hour to foam the latex, thereby producing a latex foam.

The linear velocity at the radially outer tip of the blade body of the propeller blade during stirring was 314 m / min.
<Comparative example 2>
Instead of the disc turbine blade 1, four blades having a blade diameter d of 50 cm, in which four blades having a rectangular flat plate shape are fixed to a cylindrical boss while being inclined with respect to the direction of the central axis L <b> 1. The paddle wing was used.

The paddle blade was immersed in the latex 11 so that the distance h from the liquid surface 12 of the latex 11 before stirring to the center position of the boss of the paddle blade in the direction of the central axes L1 and L2 was 60 cm. .
The ratio d / D is 0.36, which is the same as in Example 1, and the ratio h / D is 0.43, which is the same as in Example 3.

In this state, the stirrer was driven, the stirring shaft 2 was rotated at a rotation speed of 200 rpm, and stirred for 1 hour to foam the latex, thereby producing a latex foam.
The linear velocity at the radially outer tip of the blade body of the paddle blade during stirring was 314 m / min.
<Measurement of latex foam properties>
The average bubble diameter and bubble content of the latex foam produced in each example and comparative example were measured by the following methods. All measurements were performed in an environment of 23 ° C.

(Average bubble diameter)
A small amount of the manufactured latex foam was sampled on a petri dish, an image was taken using a digital microscope, and image analysis was performed. That is, 50 bubbles were arbitrarily selected from the photographed image, and the average value was calculated from the result of measuring the diameter of each bubble in the two-point distance measurement mode to obtain the average bubble diameter (μm).

(Bubble content)
The produced latex foam was weighed with a cylinder to have a volume of 100 ml, and its mass was measured to determine the apparent specific gravity of the latex foam.
The bubble content (% by volume) was calculated from the apparent specific gravity and the true specific gravity of the latex that was the basis of the latex foam.

The results are shown in Table 1.

From the results of Examples 1 to 4 and Comparative Examples 1 and 2 in Table 1, the average cell diameter of the latex foam produced by using a disc turbine blade as a stirring blade is larger than when other stirring blades are used. It was found that the latex foam can be refined to a sufficient level and the latex foam can be produced with high productivity in a short working time without requiring a step of dispersing the bubbles.

Further, from the results of Examples 1, 3, 4 and Example 2, in consideration of making the average bubble diameter as small as possible with the same stirring time, the linear velocity at the radially outer tip of the blade body of the disk turbine blade is 100 m. It has been found that it is preferable to rotate the stirring shaft so that it is at least 1 minute.
Furthermore, from the results of Examples 1 and 2 and Examples 3 and 4, considering that the bubble content is suppressed, the amount of immersion of the disk turbine blade in the latex is h / D of 0.5 or more, 1.5 It was found that it is preferable to set so as to be as follows.

DESCRIPTION OF SYMBOLS 1 Disc turbine blade 2 Stirring shaft 3 Disc 4 Blade body 5 Through-hole 6 Boss 7 Screw hole 8 Stirrer tank 9 Opening 10 Bottom part 11 Latex 12 Liquid surface 13 Radially outward tip D Inner diameter d Blade diameter h Distance L1, L2 center axis

Claims

A method for producing latex foam, comprising:
Preparing a bottomed cylindrical stirring tank arranged so that the central axis is vertical;
Containing a latex of rubber or resin in the stirring tank;
Immersing a disk turbine blade having a vertical axis of rotation in the latex contained in the stirring vessel;
Agitating the latex by rotating the disk turbine blade at a constant speed for a certain period of time;
A step of lifting the disk turbine blade after the rotation stops from within the latex;
A method for producing a latex foam.
The disk turbine blade includes a circular plate that rotates horizontally around a rotating shaft, and a plurality of flat blades that are mounted in a circumferential direction of the disk, radially about the rotating shaft and orthogonal to the disk. The method for producing a latex foam according to claim 1, comprising: a body.
The method for producing a latex foam according to claim 2, wherein in the step of stirring the latex, the rotational speed of the disk turbine blade is 100 m / min or more as expressed by the linear velocity at the radially outer tip of the blade body.
3. The method for producing a latex foam according to claim 2, wherein the rotational speed of the disc turbine blade is 250 m / min or more as expressed by the linear velocity at the radially outer tip of the blade body.
The latex foam according to any one of claims 2 to 4, wherein the rotational speed of the disk turbine blade is 500 m / min or less, expressed as a linear velocity at a radially outer tip of the blade body. Manufacturing method.
The latex foam according to any one of claims 2 to 4, wherein the rotational speed of the disk turbine blade is 450 m / min or less, expressed as a linear velocity at a radially outer tip of the blade body. Manufacturing method.
The method for producing a latex foam according to claim 1, wherein the time for rotating the disk turbine blade in the step of stirring the latex is 30 minutes or more and 2 hours or less.
In the step of storing the latex, the rubber latex stored in the agitation tank may be natural rubber latex, deproteinized natural rubber latex, nitrile rubber (acrylonitrile-butadiene rubber) latex, styrene-butadiene rubber latex, or chloroprene rubber latex. The process for producing a latex foam according to claim 1, comprising one or more of the following.
In the step of storing the latex, the latex of the resin stored in the stirring tank is one selected from a resin emulsion (latex) that can be emulsified (latexed) with a vinyl chloride resin, a urethane resin, or an acrylic resin. The method for producing a latex foam according to claim 1, comprising two or more kinds.
The method for producing a latex foam according to claim 1, wherein in the step of stirring the latex, the disk turbine blade is rotated in a state in which the rotation axis of the disk turbine blade and the central axis of the stirring tank coincide with each other.
In the step of immersing the disc turbine blade,
The ratio h / D is 0.5, where D is the inner diameter of the stirring tank and h is the distance between the central portion in the height direction of the disk turbine blade immersed so that the rotation axis extends in the vertical direction and the liquid level of the latex. The method for producing a latex foam according to claim 1, wherein the immersion depth is adjusted so as to be within a range satisfying 1.5 or less.
When the inner diameter of the stirring tank is D and the maximum diameter of the disk turbine blade (the dimension from the blade tip to the tip of the opposite blade through the rotation center) is d,
2. The maximum diameter d of the disk turbine blade and the inner diameter D of the stirring tank are set so that the ratio d / D is in a range of 0.3 to 0.4. Process for producing latex foam.