JPS5921781B2 - Method of manufacturing foam rubber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing non-gel latex foam rubber, and more specifically, the present invention relates to a method for producing non-gel latex foam rubber. When manufacturing rubber, even if the latex compound liquid has a high viscosity, it is possible to stably discharge a foamed product with a low density, which makes it possible to manufacture foam rubber with a low density of 0.29/cnt or less. The present invention relates to a method for producing non-gel latex foam rubber.

Unlike gel-type rubber, non-gel latex foam rubber does not cause rapid separation of water and solids during the gelling process, so a large amount of filler can be added, which is advantageous in terms of cost and physical properties. It has particularly excellent tensile properties and is mainly used as a carpet lining.

However, with non-gel latex foam rubber, the foamed material must be stable during heating because it is immediately heated, dried, and vulcanized without gelling or solidifying. Although efforts have been made to increase the viscosity of latex blended liquids by increasing the solid content of the liquid and further adding thickeners, the solid content of latex blended liquids is large and
If the viscosity is high, it will be very difficult to foam, and only foams with a high density can be obtained, and foam products with a density of 0.29
Only products with densities higher than 1.5mm can be manufactured stably.

For example, a cylindrical rotor 2 is rotatably disposed within a cylindrical stator 1 as shown in FIG. A latex blended liquid and air are introduced into the foaming machine 4 of a closed type pin mixer type (Euromatic type) from the inlet ports 5 and 6, respectively.
The rotor 2 is rotated to stir and foam the latex mixture and air, and the inner diameter is 30 to 50 m.
When attaching hose 8 of 1.5 m and discharging foamed material from the hose outlet, the solid content of the latex compound liquid is 70 to 80%.
If the foam is large and has a high viscosity of 500 to 5000 cps, it is possible to create bubbles in a stable state with a density of O,
This is the case when producing a foam product with a density of 3 y/crit or more, and even if an attempt is made to obtain a foam product with a density lower than that, a stable foam product cannot be obtained. In this case, even if the amount of air input is increased in order to further reduce the density of the foamed product, the air and the latex blended liquid are discharged in a separated state, and the density of the foamed product does not decrease. Such a separation phenomenon becomes more noticeable as the flow rate of the latex mixture to be foamed by the foaming machine increases (inevitably, the flow rate of air must also increase). In addition, as a method of reducing the density of the foamed product, it has been proposed to lower the solid content of the latex compound liquid and lower the viscosity of the liquid.In this case, the density of the foamed product can be reduced, and compared to However, as the solid content of the latex mixture decreases, the thermal energy required for drying and vulcanization increases, and the stability of the foam during drying and vulcanization increases. This method has disadvantages in that it is impractical in terms of cost and process, as it causes problems such as a decrease in the physical properties of the foam rubber produced, and the inability to increase the amount of filler blended.

Thus, non-gel latex foam rubber usually has a density of 0.2f! It is difficult to obtain foam products with a density lower than that, and for this reason, attempts have been made to use non-gel latex foam rubber as cushioning agents for pinerests, cushions, etc. However, since the foam density is 0.2 g/d or more, the weight of the product becomes large, making it inconvenient for daily use and making the product expensive. It had problems such as being generally unsuitable as a material.

The present invention has improved the above-mentioned situation, and provides a method for simply, reliably, and inexpensively manufacturing non-gel latex foam rubber that has a low foam density and can be suitably used as cushioning material for pinerests, cushions, etc. The purpose is to provide.

That is, the inventors of the present invention have conducted intensive studies on the manufacturing method of low-density non-gel latex foam rubber, and as a result, introduced a latex mixture and air into a closed foaming machine such as a closed pin mixer type. When producing a non-gel latex foam rubber by foaming a latex blended liquid and discharging the foamed product, drying and vulcanizing, an orifice or valve is provided at the discharge port of the foaming machine, or Attach a small diameter hose to the foam machine discharge port to restrict the foam discharge passage.
In addition to increasing the internal pressure of the foaming machine to perform foaming,
The diameter of the outlet of the discharge passage is increased to discharge the foamed material from the outlet of the discharge passage at a low speed, particularly preferably the internal pressure of the foaming machine is 2 kg/Cd or more, particularly 2 to 8 kg/C7ll.
By setting the flow velocity at the outlet of the discharge passage to 1.2 m/Sec or less, the latex mixed liquid is
Even when the viscosity is as high as
．． It was discovered that low density non-gel latex foam rubber with a density of 29/d or less can be reliably produced and the above object is achieved, and the present invention has been completed. This will be explained in detail with reference to FIGS. 2 to 5.

The method for producing non-gel latex foam rubber according to the present invention involves introducing a latex mixture and air into a closed foaming machine, foaming the latex mixture, and discharging the foamed product. A throttle is provided to the discharge passage, thereby increasing the internal pressure of the foaming machine, and the diameter of the outlet of the discharge passage is increased to discharge the foamed material from the outlet of the discharge passage at a relatively low speed. Figures 2 to 5 each show an example of the apparatus used to carry out the method of the present invention (in the apparatuses shown in Figures 2 to 5, the configuration of the foaming machine is the same as that in Figure 1). Since it is the same as the foaming machine, the same mechanical parts are given the same reference numerals and the explanation thereof will be omitted.

), which shows the method of throttling the discharge passage. To further explain this point, in the device shown in FIG. 7. The foamed material discharge passage 11 formed by the orifice 9 and the discharge hose 10 is narrowed by the arrangement of the orifice 9. Valve 9 instead of 9
By arranging ', a restriction is added to the discharge passage 11.

In addition, the device shown in FIG. 4 has a valve 9' at the foaming machine discharge port 7 and a discharge hose 10' whose inner diameter gradually increases from the inlet side to the outlet side, so that the discharge passage 11 can be The foamed material is discharged at a slower speed (the length of the discharge hose 10' is preferably 0.5 m or more, and the inner diameter is expanded at a rate of 502 m1 or less in diameter per 1 m of length). (Furthermore, it is also possible to make the inner diameter of the discharge hose 10' narrower on the inlet side to provide a restriction.)
In the apparatus shown in FIG. 5, a first hose 10a with a small diameter is attached to the foaming machine discharge port 7, a second hose 10b with a larger diameter is attached to the first hose 10a, and a second hose 10b with a larger diameter is attached to the second hose 10b. A third hose 10c with a larger diameter is attached, and in this way, a plurality of hoses with different inner diameters are connected in order of decreasing diameter, and the hose with the smallest inner diameter is attached to the foaming machine discharge port 7. Therefore, the discharge passage 11 is restricted by the hose 10a with the minimum inner diameter, and the hose with a large diameter is connected to slow down the discharge speed of foamed material at the outlet of the discharge passage. (The length of each hose 10a, b, c is preferably 0.5 m or more). in this case,
The inner diameter of the inlet end of the discharge hose 10', which gradually increases in inner diameter from the inlet side to the outlet side, or the inner diameter of the hose 10a with the minimum inner diameter is set to a diameter smaller than the foaming machine outlet 7, as shown in FIGS. 4 and 5, respectively. The aperture effect can be further enhanced by forming the aperture. Note that the squeezing method is not limited to the above method, and various changes can be made, and the squeezing methods described above can be combined as appropriate. In this way, the present invention constricts the discharge passage of the foamed material, widens the outlet side of the discharge passage, increases the internal pressure of the foaming machine, and
The foamed material is discharged from the outlet of the discharge passage at low pressure and low speed. This makes it possible to stably discharge low-density foamed material without causing bubble collapse, etc. This made it possible to obtain a non-gel latex foam rubber with a high density.

On the other hand, such an effect cannot be obtained even if a hose having the same inner diameter is simply connected to the discharge port of the foaming machine over its entire length as shown in FIG. Even if the diameter of the hose is reduced, if the flow rate of the latex mixture and air is increased, bubbles will collapse at the end of the hose (flow path outlet), resulting in a high density of foamed material. This is because the discharge flow rate of the foamed material at the tip of the hose increases and the foam collapses.
It is preferable to use the hose connection method shown in the figure to reduce the discharge speed of the foamed material. The degree of constriction of the discharge passage varies depending on the size of the foaming machine, the amount of latex mixture and air sent into the foaming machine, and the desired foam rubber density, etc.
Cd or more, preferably 2 to 8 kg/C7 ll, and the foamed material has a flow rate of 1 at the outlet of the discharge passage.
．． It is preferable to flow at a rate of 2 m/Sec or less, so that even if the Relatex compounded liquid has a high viscosity, a low-density foam can be reliably discharged.
Foam rubber having a value of 9/CTl or less can be manufactured reliably.

On the other hand, if the pressure inside the foaming machine is lower than 2k9/d, a phenomenon occurs in which bubbles and air are separated and discharged, and a low-density foamed product may not be stably discharged. In addition, 8
There is no problem even if it is higher than kg/d, but in this case, a device with high pressure resistance is required. Furthermore, if the flow velocity of the foam at the outlet of the discharge passage is faster than 1.2 m/Sec, bubble collapse will occur at the outlet of the passage and the density of the foam will increase.
There may be cases where it is not possible to obtain a foam rubber with a low density of 0.2f1/Crl or less. To give a more specific example, when using the foaming machine shown in the example below, when the latex flow rate is 1k9/Mm, the internal pressure of the foaming machine is 41<9/Cr.
l or more, latex flow rate 2k9/Mi! When l, internal pressure is 5
When 1<9/Cd or more, the internal pressure is 6 kg/d or more when the latex flow rate is 3 kg/Mm, and the flow rate of the foamed material at the outlet of the discharge passage is 1.2 m/Sec or less, so that the density is 0.
．． A foamed material having a diameter of about 19/d can be produced satisfactorily.

In the present invention, there is no particular restriction on the composition of the latex compounding liquid, and those having the composition used in the production of ordinary non-gel latex foam rubber can be used, such as natural latex, SBR, etc.
Synthetic latex such as latex, sulfur, vulcanization accelerators such as mercaptobenzothiazole zinc salt, zinc diethyldithiocarbamate, anti-aging agents such as styrenated phenol, fillers such as zinc white, clay, talc, calcium carbonate, mica, etc. A conventional composition prepared by appropriately mixing components such as a surfactant can be used.

Furthermore, although the type of foaming machine is not necessarily limited to the type shown in the above-mentioned drawings, the present invention can be applied not only to low-viscosity latex mixtures but also to high-viscosity latex mixtures with a viscosity of 500 to 5,000 cps. It can be suitably adopted, and it is possible to obtain a foam rubber with particularly excellent physical properties, and it can be manufactured at a low cost because it can contain a large number of fillers, and the thermal energy required for drying and vulcanization can be reduced. The viscosity is 5 because it has the advantages of
It is effective to apply the method of the present invention to a latex compound liquid with a high viscosity of about 00 to 5,000 cps, and in this case, it is possible to use a closed pin mixer type euromatic foaming machine as shown in the figure. preferable. Furthermore, the steps after discharging the foam can be the same as in the case of manufacturing conventional non-gel latex foam rubber, such as drying and vulcanization at a desired temperature by a desired means such as hot air blowing,
Manufactures foam rubber.

In this case, hot air is used during drying and vulcanization, and the amount of hot air is increased at the beginning of drying and vulcanization (20 to 8
0TI? [, preferably 40 to 50 I/Mm], or increase the hot air temperature (120 to 150 °C, preferably 140
~150℃) to increase the amount of energy supplied by hot air,
At the final stage of drying and vulcanization, reduce the hot air volume (10 to 50 i/M7!t1 preferably 20 to 30 i/M per 1 d of product)
m) By lowering the hot air temperature (80 to 130°C, preferably 100 to 120°C) and reducing the amount of energy supplied to the hot air, stable drying and vulcanization can be achieved, especially at low density. This is effective when obtaining a foam rubber product with a large thickness. As explained above, the present invention narrows down the foamed material discharge passage and preferably lowers the internal pressure of the foaming machine to 2.
kg/c! By increasing the viscosity to 11 or more, especially 2 to 8 kg/Cd, and discharging the foamed material at a low speed of 1.2 m/Sec or less at the exit of the passage, the viscosity is 500
Even when using a latex compounded liquid with a high viscosity of ~5000 cps, it is possible to stably and continuously discharge a good foamed product with low density and no bubble collapse, and 0.29 cps.
/Crlt or less low-density sheet-like foam rubber can be easily and reliably produced at low cost,
Therefore, it is possible to provide a non-gel latex foam rubber that can be suitably used as a cushion material at a low cost.
Next, the present invention will be explained in more detail by showing examples and comparative examples, but the present invention is not limited to the following examples.

In the following examples, the formulation of the latex mixture and the foaming machine used are as follows.

Latex Compound Solution A latex compound solution was prepared by adding required amounts of sulfur, vulcanization accelerator, anti-aging agent, zinc white, filler, and surfactant to a mixture of SBR latex and natural rubber latex.

Foaming machine used: Euromatic type foaming machine 1;
1] Attach a 51 mφ orifice for squeezing to the discharge port (bore diameter 30 mI) of the above foaming machine, and also add an orifice with an inner diameter of 20 μm.
A 5m diameter discharge hose was attached.

Flow rate of latex to the foaming machine is 2.0kg/7707! , air is 18.01/Mm (value at normal temperature and pressure, same below)
The foam is introduced and foamed at a rate of 307 r per 1 TrI product, and the foam is continuously discharged from a hose onto a conveyor.
/i1 Drying and vulcanization were carried out under the conditions of hot air temperature of 145° C. at the beginning and 120° C. at the final stage to obtain a foam rubber. At this time, the pressure inside the foaming machine was 5.0 k9/d, the flow rate of the foamed material at the outlet of the discharge hose was 1.1 m/Sec, and the discharge state of the foamed material was stable.

The density of the obtained foamed material was 0.109/Crl, and by drying and vulcanizing it, the density was approximately 0.075.
A foam rubber of 9/Cl was obtained. [Example 2
] A 5 m hose with an inner diameter of 12 m 1 Lφ was attached to the outlet of the foaming machine for squeezing, and a 1 m hose with an inner diameter of 20 Lφ was attached to the tip of the hose, and foaming was carried out under the same flow rate conditions as in Example 1.
I got a foam mule.

At this time, the internal pressure of the foaming machine was 5.2 kg/Cdl, and the flow rate of the foamed material at the outlet of the discharge hose was 1.1 m/Sec.
The discharge state of the foamed material was stable.

Moreover, the density of the obtained foamed material was 0.109/d. [Example 3] 6m1 for squeezing at the outlet of the foaming machine
! An Lφ orifice was attached, and a 5 m hose with an inner diameter of 20 m and 1φ was also attached.

The 1 m portion of this hose on the distal end side was formed so that the inner diameter gradually increased toward the distal end, so that the inner diameter of the hose discharge port was 231 m1. Latex was introduced into a foaming machine at a flow rate of 3.0 kg/Mml and air at a rate of 27.0/Mul, foamed, and the foam was continuously discharged from a hose onto a conveyor under the same conditions as Example 1. It was dried and vulcanized to obtain a foam rubber. At this time, the internal pressure of the foaming machine is 6,
0K9/Cd, and the flow rate of foam at the hose outlet is 1
．． The discharge state of the foamed material was stable at 2 m/Sec.

Moreover, the density of the obtained foam was 0.109/CTil. [Example 4] A first 5 m hose with an inner diameter of 12 mmφ was attached to the discharge port of the foaming machine for squeezing.
Inner diameter 20m7 at the end of the hose! The second hose of Lφ is 1m.
1 Furthermore, the inner diameter of this second hose tip is 25m77! 3rd of φ
A 1 m hose was attached and foaming was carried out under the same flow rate conditions as in Example 3 to obtain a foam rubber in the same manner.

At this time, the internal pressure of the foaming machine was 6.2kg/(177f), and the flow rate of the foamed material at the third hose outlet was 1.0m/S.
ec, the discharge state of the foamed material was stable.

Moreover, the density of the obtained foamed product is 0.10f! /C7l. [Comparative example] 6 m for squeezing at the outlet of the foaming machine
7! Attach an orifice of Lφ and further increase the inner diameter to 22u1φ
A 5 m hose was attached and foaming was carried out under the same flow rate conditions as in Example 3 to obtain foam rubber in the same manner.

At this time, the internal pressure of the foaming machine was 6.01<g/CTIl, and the flow rate of the foamed material at the outlet of the hose was 1.3 m/Sec.
The foamed material was discharged as a jet from the hose outlet.

Moreover, the density of the obtained foamed material was 0.30 g/d.

[Brief explanation of the drawing]

Figure 1 is a schematic cross-sectional view of the foaming and discharging device used in the conventional method.
2 to 5 are schematic cross-sectional views each showing an example of a foaming and discharging device used in the method of the present invention O1...
Stator, 2...Rotor, 3,3t...
... Pin, 4... Foaming machine, 5... Latex mixture inlet, 6... Air inlet, 7...
... Foaming machine discharge port, 9 ... Orifice,
9t...Valve, 10, 10', 10a, 10b
, 10c...Discharge hose, 11... Foamed material discharge passage.

Claims (1)

[Claims] 1. Introducing the latex mixture and air into a closed foaming machine to foam the latex mixture and discharge this foamed product,
In a method of manufacturing latex foam rubber by drying and vulcanizing, a restriction is provided to the discharge passage of the foamed material to increase the internal pressure of the foaming machine, and the foamed material is discharged from the outlet of the discharge passage at a flow rate of 1.2 m. A method for producing latex foam rubber, characterized by discharging at a low speed of /sec or less.