JPH0661867B2 - Continuous molding method for foamed rubber sheet - Google Patents

Description

Detailed Description of the Invention

[0001]

This invention is used as seal packing in various fields such as electric appliances and automobiles.
In addition, the present invention relates to a method for continuously molding a foamed rubber sheet that exhibits good sealing properties under a relatively low compression rate.

[0002]

2. Description of the Related Art A foamed rubber sheet for seal packing is formed by molding an unvulcanized rubber containing a foaming agent into a long sheet having a width of 0.5 to 1.2 meters by a calender or an extruder. It is made by cutting it to a short length of 0.5 to 3.0 meters and then vulcanizing it using a mold under a pressure of 1.0 to 10 kg / cm ² , and then punching it into a desired shape. It was used as seal packing.

On the other hand, as a method for producing a foamed rubber sheet used for a wet suit or the like, an unvulcanized rubber containing a foaming agent is formed into a long sheet shape, and one side or both sides of this rubber sheet has a cloth or a surface. Laminated synthetic resin film with unevenness, and supply between the heating cylinder rotating in one direction and the endless steel belt wound around the surface,
A method is known in which the above-mentioned rubber sheet is transferred by rotation of a heating cylinder and is heated under a surface pressure of 0.2 to 4 kg / cm ² by a steel belt to continuously perform vulcanization and foaming (Japanese Patent Laid-Open Publication No. Sho. 58-219036).

[0004]

However, the method of cutting an unvulcanized rubber sheet into a short length and vulcanizing it by using a mold is because the obtained foamed rubber sheet is short, so that the punching work of the seal packing is performed. Cannot be performed continuously,
There are problems such as an increase in man-hours and a decrease in yield. On the other hand, the method for producing a foamed rubber sheet for wet suits allows the work to be carried out continuously, while the unvulcanized rubber sheet is overlaid with a cloth or a synthetic resin film having surface irregularities. Unevenness is formed on the surface of the sheet, and since the pressure of the steel belt is only applied during vulcanization, the pressure during vulcanization is insufficient,
There are many variations in the size of the bubbles formed by foaming,
Since the compression set was large and the sealing performance was low, it was unsuitable for seal packing.

The present invention improves the continuous molding method using the above-mentioned known steel belt to have a smooth skin layer, small cell size, uniform size, and small compression set. A continuous production of a foamed rubber sheet suitable for seal packing.

[0006]

SUMMARY OF THE INVENTION A method of continuously forming a foamed rubber sheet according to the present invention comprises an unvulcanized rubber containing a foaming agent formed into a sheet, a heating cylinder which rotates the rubber sheet in one direction, and In the continuous molding method of a foamed rubber sheet, which is vulcanized and foamed under pressure while being sandwiched between a high-strength steel belt that is wound around a surface and rotated together with a heating cylinder and transferred, in the above-mentioned unvulcanized rubber The release sheet is placed on both the front and back sides or one side of the sheet, and the release sheet is supplied between the heating cylinder and the steel belt. The rubber sheet immediately after contacting the heating cylinder is a belt of 1 to 5 kg / cm ² due to the tension of the steel belt. Pressure and 2 to 5 kg / cm ² applied by a pressure device provided outside the steel belt
It is characterized in that the pressure is applied at the total pressure of the additional pressure of 1 and then only the above belt pressure is applied.

The unvulcanized rubber sheet of the present invention is molded by an extruder or a calendar as in the conventional case,
The thickness is preferably 1.0 to 10 mm. The release paper to be stacked on this rubber sheet needs to be stacked on both the front and back sides of the rubber sheet when the target sheet packing is a ring-shaped packing that intervenes at the joint for connecting the pipes by abutting each other. The sheet packing is interposed between the pipe and the blind flange, and in the case of packing having the same shape as the blind flange, only one side (the side in contact with the pipe) can be used. Further, the contact angle of the steel belt with respect to the heating cylinder is usually 180 to 2
It is 70 degrees, and this range is the vulcanization effective region, but it is preferable to provide a pressurizing device for applying an additional pressure in a region of 1/5 to 1/8 of the length of the vulcanization effective region. . In addition,
The vulcanization temperature is 150 to 220 ° C, and the total vulcanization time is 1 to
10 minutes is preferable, and it is set according to the thickness of the rubber sheet.

[0008]

The unvulcanized rubber sheet is vulcanized under pressure while passing through the vulcanization effective area where the steel belt contacts the heating cylinder, and at the same time foams to become a foamed rubber sheet.
In this case, a smooth skin layer having a uniform thickness is formed on the surface on which the release paper is stacked. At the inlet side of the effective vulcanization area, since it is vulcanized under a strong pressure due to the total pressure of the belt pressure and the additional pressure, foaming is suppressed, the bubbles are small and uniform, and then the inlet side portion Past,
Since it is vulcanized only under a weak pressure of the belt, it has a smooth skin layer and the thickness of the skin layer is 0.1 to 1.0.
A foamed rubber sheet having a small compression set can be obtained in a uniform foamed state with a foaming ratio of 1.1 mm to 2.5 mm.

However, when the belt pressure applied by the tension of the steel belt is less than 1 kg / cm ² , excessive foaming occurs, while when it exceeds 5 kg / cm ² , insufficient foaming occurs, and the additional pressure applied by the pressurizing device is 2 kg. / for cm less than ^2, the effect can not be obtained by adding additional pressure, greater than 5 kg / cm ² and the blowing is reduced on the contrary, not even able to achieve the intended purpose in any case. The compression set is used as a substitute characteristic for knowing the sealing performance of the seal packing, and the sample is compressed by 25% and stored in a room at 70 ° C.
It is indicated by the residual strain after standing for 2 hours, and the smaller the value, the less the settling and the better the sealing performance, but it is preferably 25% or less in practical use.

[0010]

FIG. 1 shows an example of a continuous vulcanizing apparatus suitable for carrying out the present invention. In FIG. 1, reference numeral 11 denotes a pulling roll, and on the left side thereof, an auxiliary roll 12, a heating cylinder 13 and a driving roll 14 are arranged in a staggered manner from the bottom to the auxiliary roll 12, the heating cylinder. 1
3 and the driving roll 14 are wound around an endless steel belt 15, and this steel belt 15 is driven by the driving roll 1
Drive 4 to rotate clockwise. The tension of the steel belt 15 can be changed by sliding the pulling roll 11 to the left and right in the figure, whereby the heating cylinder 1
The contact pressure between 3 and the steel belt 15 is adjusted.

Pressurization consisting of a plurality of thin pressure-bonding rolls 16 on the outside of the steel belt 15 in contact with the lower part of the heating cylinder 13 and a fluid cylinder (not shown) for individually pressing these into contact with the heating cylinder 13. A device is provided. Then, an unvulcanized rubber sheet S is supplied substantially horizontally from the left toward the upper surface of the steel belt 15 wound around the auxiliary roll 12, and this rubber sheet S is supplied.
The lower surface release paper 17 is supplied to the lower side of the heating cylinder 1
An upper surface release paper 18 is supplied via a guide roller 19 between the lower surface of 3 and the rubber sheet S in contact with the lower surface.

The unvulcanized rubber sheet S is the release paper 1 for the lower surface.
7 and the release paper 18 for the upper surface are overlapped and then introduced into the vulcanization area formed by the heating cylinder 13 and the steel belt 15, and at the inlet side thereof, the belt pressure by the tension of the steel belt 15 and the pressure bonding roll (pressurizing device ) 16 and vulcanized under the total pressure of
From the time when the steel sheet is left to reach the upper surface of the heating cylinder 13, it is continuously vulcanized under the belt pressure based on the tension of the steel belt 15, and then taken out from the upper surface of the heating cylinder 13 as the foamed rubber sheet Sa. Then, when the foamed rubber sheet Sa reaches above the drive roll 14, the upper surface release paper 18 is peeled from the upper surface and wound up, and the foamed rubber sheet Sa rides on the steel belt 15 and is placed on the pulling roll 11. When conveyed, the lower surface release paper 17 is peeled from the lower surface and wound up,
The foamed rubber sheet Sa is sent to a winding device (not shown) via the guide roller 20.

Example 1 A foamed rubber sheet was manufactured using the continuous vulcanizing apparatus shown in FIG. For unvulcanized rubber, NBR listed in Table 1 below is used.
2 mm thick from the extruder roller head using the compound
Was extruded into a sheet form. As the foaming agent, a mixture of azodicarbonamide and dinitropentamethyltetramine was used.

Table 1 NBR (Medium-high nitrile) 100 parts by weight Zinc white 5 parts by weight Stearic acid 1 part by weight DOP 15 parts by weight SRF carbon 60 parts by weight Sulfur 1.5 parts by weight Accelerator TT 0.2 parts by weight Accelerator DM 1.5 parts by weight Foaming agent 4.0 parts by weight

Release papers 17 and 18 are superposed on the front and back surfaces of the unvulcanized rubber sheet S, and have a diameter of 1500 mm and a temperature of 180.
℃, supplied to the heating cylinder 13 of effective vulcanization area length 3140mm, belt pressure 5kg / cm ² , additional pressure 3kg / cm ² ,
The length of the inlet side area to which additional pressure is applied is 523 mm (1/6 of the effective vulcanization area length), the speed of the steel belt 15 is 1 m /
Min, total vulcanization time was vulcanized under the condition of 189 seconds, and Example 1
The foamed rubber sheet Sa was manufactured. On the other hand, Example 1 above
The foamed rubber sheet of Comparative Example 1 was manufactured by omitting the additional pressure. The properties of the foamed rubber sheets of Example 1 and Comparative Example 1 are shown in Table 2 below.

Table 2 Example 1 Comparative Example 1 Foaming density (g / cc) 0.75 0.70 Porosity (%) 55 60 Compression set (%) 25 37

That is, Example 1 has significantly improved sealing performance as compared with Comparative Example 1, and has suitable performance for seal packing. The unvulcanized rubber sheet of Example 1 was vulcanized under various conditions and foamed (provided that the foaming density was 0.70 to 0.80), and the compression set and voids of the resulting foamed rubber sheet were When the ratio (the ratio of air bubbles to the solid portion) was measured, as shown in FIG.
Up to about 2%, as the porosity increases, the cell diameter increases and becomes uniform, so the compression set decreases and the sealing performance improves. However, when the porosity increases further, the bubbles become excessive and continuous. The number of air bubbles increased and the compression set rapidly increased, making it unusable as a sealing material.

Example 2 In the above Example 1, the amount of the foaming agent was reduced to 2.0 parts by weight, the belt pressure was 1 kg / cm ² , and the applied pressure was 4 kg / cm ^2.
except for changing the cm ² is carried out in the same manner as Example 1 Example 2
The foamed rubber sheet Sa was manufactured. Comparative Example 2 is the same as Example 2 except that the applied pressure of Example 2 is omitted.
The foamed rubber sheet of The performances of the foamed rubber sheets of Example 2 and Comparative Example 2 are shown in Table 3 below.

Table 3 Example 2 Comparative Example 2 Foaming density (g / cc) 0.71 0.80 Porosity (%) 51 40 Compression set (%) 20 33

[0020]

As described above, according to the present invention, an unvulcanized rubber sheet containing a foaming agent is sandwiched between a heating cylinder and a steel belt and continuously vulcanized while being pressurized to foam. In the method, the release sheet is superposed on both front and back surfaces or one side of the rubber sheet and sent to the heating cylinder, and at the inlet side of the vulcanization area formed by the heating cylinder and the steel belt, the tension of the steel belt is applied to the rubber sheet. It is a method of vulcanizing under strong pressure while applying additional pressure with a pressurizing device other than the belt pressure applied with, and vulcanizing under pressure other than the above-mentioned inlet side pressure under weak belt pressure only. , The above belt pressure is 1 to 5
Since the applied pressure is set to kg / cm ² and the applied pressure is set to ² to 5 kg / cm ² , respectively, a skin layer having a smooth and uniform thickness is formed on the surface on which the release paper is laminated, and bubbles formed by foaming are formed. It is possible to obtain a foamed rubber sheet which is small and uniform, has a small compression set, and is suitable for seal packing. Then, it can be easily carried out by adding a pressure device to the inlet side of the above-mentioned vulcanization area of the existing continuous vulcanization device.

[Brief description of drawings]

FIG. 1 is a side view of a vulcanizing apparatus illustrating an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the porosity of a foamed rubber sheet and the compression set.

[Explanation of symbols]

 S: Unvulcanized rubber sheet Sa: Foamed rubber sheet 11: Tensile roll 12: Auxiliary roll 13: Heating cylinder 14: Drive roll 15: Steel belt 16: Crimping roll constituting a pressure device 17: Release paper for lower surface 18: Top release paper 19, 20: Guide roller

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location B29L 31:26 4F

Claims (1)

[Claims] 1. An unvulcanized rubber containing a foaming agent is formed into a sheet, and a heating cylinder that rotates the rubber sheet in one direction and a high-tensile steel belt that is wound around the surface of the heating cylinder and rotates together with the heating cylinder. In a continuous molding method of a foamed rubber sheet that is vulcanized and foamed under pressure while being sandwiched between and transferred, the above-mentioned unvulcanized rubber sheet is laminated with release paper on both front and back surfaces or one surface thereof and a heating cylinder. The rubber sheet immediately after coming into contact with the heating cylinder is supplied between the steel belt and the steel belt by the tension of the steel belt.
A belt pressure of 5 kg / cm ^2, the steel belt was pressurized with a total pressure of the additional pressure of 2~5kg / cm ² which is added with a pressure device which is provided on the outside of, accordingly later above the belt pressure only at elevated A method for continuously molding a foamed rubber sheet, which comprises pressing.